Orcad Layout. Getting Started

Transcription

1 Orcad Layout Gettig Started

2 Copyright Cadece Desig Systems, Ic. All rights reserved. Trademarks Allegro, Ambit, BuildGates, Cadece, Cadece logo, Cocept, Diva, Dracula, Gate Esemble, NC Verilog, OpeBook olie documetatio library, Orcad, Orcad Capture, PSpice, SourceLik olie customer support, SPECCTRA, Spectre, Vampire, Verifault-XL, Verilog, Verilog-XL, ad Virtuoso are registered trademarks of Cadece Desig Systems, Ic. Affirma, Assura, Cierto, Evisia, Mercury Plus, Quicktur, Radium, Silico Esemble, ad SPECCTRAQuest are trademarks of Cadece Desig Systems, Ic. Alaza is a service mark of Cadece Desig Systems, Ic. All other brad ad product ames metioed herei are used for idetificatio purposes oly ad are registered trademarks, trademarks, or service marks of their respective holders. Part Number Secod editio 31 May 2000 Cadece PCB Systems Divisio (PSD) offices PSD mai office (Portlad) (503) PSD Irvie office (949) PSD Japa office PSD UK office PSD customer support (877) PSD web site PSD customer support web page PSD customer support form Cadece PCB Systems Divisio SW 68th Parkway, Suite 200 Portlad, OR 97223

3 Cotets Before you begi vii Welcome to OrCAD vii How to use this guide viii Symbols ad covetios viii Chapter 1 Chapter 2 Chapter 3 Chapter 4 Board desig tasks 1 Typical board desig tasks Board desig flow Creatig a board 5 Methods to create a board Creatig a board from scratch Creatig a board usig a board template Importig a board usig the DXF to Layout traslator Importig a board usig the PRO-E to Layout traslator Settig up board parameters 15 Creatig a board outlie Settig uits of measuremet Settig system grids Addig moutig holes to a board Defiig the layer stack Defiig global spacig values Defiig padstacks Usig vias Placig compoets 29 Preparig the board for compoet placemet Checkig the board, place, ad isertio outlies Checkig the place grid

4 Cotets Checkig mirror layers ad library layers Weightig ad color-codig ets Checkig gate ad pi iformatio Securig preplaced compoets o the board Creatig height or group keepis ad keepouts Loadig a placemet strategy file Disablig the power ad groud ets Placig compoets maually Selectig the ext compoets for placemet Placig compoet groups Miimizig coectios to optimize placemet Checkig placemet Usig Placemet Spacig Violatios Usig the desity graph Viewig placemet statistics Chapter 5 Chapter 6 Routig critical ets 45 Push-ad-shove routig Iteractive routig Before you begi routig Routig the board maually Checkig the board outlie, via defiitios, ad routig ad via grids 48 Loadig a routig strategy file Chagig board desity usig routig strategy files Routig power ad groud Faout Verifyig plae layer coectios ad disablig power ad groud ets 54 Usig iteractive push-ad-shove routig Usig shove track mode Checkig routig Usig Route Spacig Violatios Viewig routig statistics Fiishig the board 59 Checkig desig rules Ivestigatig errors Removig violatios Cleaig up your desig Reamig compoets Back aotatig iv

5 Cotets Post processig Creatig reports Idex 67 v

6 Cotets vi

7 Before you begi Welcome to OrCAD OrCAD offers a total solutio for your core desig tasks: schematic- ad VHDL-based desig etry; FPGA ad CPLD desig sythesis; digital, aalog, ad mixed-sigal simulatio; ad prited circuit board layout. What s more, OrCAD s products are a suite of applicatios built aroud a egieer's desig flow ot just a collectio of idepedetly developed poit tools.

8 Before you begi How to use this guide This guide is desiged so you ca quickly fid the iformatio you eed to use OrCAD Layout. Symbols ad covetios OrCAD prited documetatio uses a few special symbols ad covetios. Notatio Examples Descriptio C+r Press C+r Meas to hold dow the C key while pressig r. A, f, o From the File meu, choose Ope (A, f, o) Meas that you have two optios. You ca use the mouse to choose the Ope commad from the File meu, or you ca press each of the keys i paretheses i order: first A, the f, the o. Moospace fot I the Part Name text box, type PARAM. Text that you type is show i moospace fot. I the example, you type the characters P, A, R, A, ad M. UPPERCASE I Capture, ope CLIPPERA.DSN. Path ad fileames are show i uppercase. I the example, you ope the desig file amed CLIPPERA.DSN. Italics I Capture, save desig_ame.dsn. Iformatio that you are to provide is show i italics. I the example, you save the desig with a ame of your choice, but it must have a extesio of.dsn. viii

9 Board desig tasks 1 This maual was created especially to address specific tasks that electroic desig egieers perform. Depedig o where you fall i the task list below, you ll use some or all of Layout s capabilities to accomplish your board desig tasks. The See otatio below each bullet item directs you to the chapters or sectios i this maual that pertai to your specific tasks. Desigig a board from start to fiish. See The etire maual. Reviewig boards that others have created. See Checkig placemet, Checkig routig. Specifyig placemet ad critical routig. See Placig compoets, Checkig placemet, Routig critical ets, ad Checkig routig.

10 Chapter 1 Board desig tasks For istructios o creatig a etlist i Capture, see the Capture documetatio. For iformatio o usig GerbTool, see the OrCAD Layout GerbTool User s Guide. Typical board desig tasks Typical board desig tasks iclude the followig: Creatig the board. Usig Capture, you create a etlist from your schematic that may iclude your desig rules to guide logical placemet ad routig, the load the etlist ito Layout. Specifyig board parameters. You specify global settigs for the board, icludig uits of measuremet, grids, ad spacig. I additio, you create a board outlie ad defie the layer stack, padstacks, ad vias. Placig compoets ad checkig the placemet. You use the compoet tool to maually place compoets o the board idividually or i groups. You the check the placemet usig placemet iformatio from a variety of sources. Routig the board ad checkig the routig. You route the board, ad ca take advatage of push-ad-shove (a routig techology), which moves tracks to make room for the track you are curretly routig. You the check the routig usig routig iformatio from a variety of sources. Fiishig the board. Layout supplies a ordered progressio of commads o the Auto meu for fiishig your desig. These commads iclude Desig Rule Check, Cleaup Desig, Reame Compoets, Back Aotate, Ru Post Processor, ad Create Reports. Layout icludes GerbTool, which is a full-featured CAM tool, icludig a Gerber editor, that reads ad writes all stadard Gerber formats ad IPC-356. GerbTool has features for automatic teardroppig, paelizatio, vetig ad thievig, ad removal of uused pads ad silkscree o pads. These processes are used to improve maufacturability. 2

11 Board desig flow Layout also icludes Visual CADD, which is a two-dimesioal draftig tool you ca use for your mechaical desig eeds. Visual CADD facilitates desig ad draftig by providig tools for creatig board outlies, height keepis ad keepouts, ad similar objects, as well as sigle or double lies, circles, regular ad irregular polygos, ad more. Visual CADD imports ad exports.dwg,.dxf, ad.gcd files. For iformatio o usig Visual CADD, see the OrCAD Layout Visual CADD User s Guide or the OrCAD Layout Visual CADD Tutorial maual. Board desig flow The flowchart below illustrates a typical board desig flow. 3

12 Chapter 1 Board desig tasks 4

13 Creatig a board 2 Before you begi creatig a board, read the followig to become more familiar with the types of files you may be workig with. A etlist file (.MNL) describes the itercoectios of a schematic desig usig the ames of the ets, compoets, ad pis. A etlist cotais the followig: Footprit ames Electrical packagig Compoet ames Net ames The compoet pi for each et Net, pi, ad compoet property iformatio For istructios o creatig a etlist i Capture, see the Capture documetatio.

14 Chapter 2 Creatig a board Other board criteria, such as uits of measuremet, system grids, ad spacig values ca be saved with a board template for use with future boards. For istructios o creatig a custom board template (.TPL), see Custom templates i Chapter 4: Settig up the board i the OrCAD Layout User s Guide. A techology template (.TCH) specifies the characteristics of a board, icludig maufacturig complexity ad compoet type. Techology templates ca also iclude the layer structure, grid settigs, spacig istructios, ad a variety of other board criteria. The techology templates supplied with Layout are documeted i Appedix A: Uderstadig the files used with Layout i the OrCAD Layout User s Guide. A board template (.TPL) combies a board outlie ad possible moutig holes, edge coectors, ad other physical board objects merged with Layout s default techology template, DEFAULT.TCH. The board templates supplied with Layout are illustrated i the OrCAD Layout Footprit Libraries maual. A board file (.MAX) cotais all of the board s physical ad electrical iformatio. Methods to create a board Create a board from scratch Use a board template Import your board to Layout usig the DXF to Layout traslator Import your board to Layout usig the PRO-E to Layout traslator 6

15 Methods to create a board Creatig a board from scratch To create a board from scratch 1 Esure that a etlist with all footprits ad other ecessary iformatio has bee created. 2 Create a directory i which the schematic desig, etlist, ad board will coexist ad put the schematic desig (if you have it) ad etlist i it. OrCAD provides a directory (ORCADWIN\LAYOUT\DESIGN) for this purpose. 3 From the Layout sessio frame s File meu, choose New. The Load Template File dialog box displays. 4 Select a techology template (.TCH), the choose the Ope butto. The Load Netlist Source dialog box displays. 5 Select a etlist file (for example, desig_ame.mnl), the choose the Ope butto. The Save File As dialog box displays. 6 Specify a ame for the ew board (for example, desig_ame.max), the choose the Save butto. The AutoECO process begis. 7 If ecessary, respod to the Lik Footprit to Compoet dialog box (choose the dialog box s Help butto for a explaatio of the dialog box s optios). 8 Draw a board outlie usig the steps i To create a board outlie o page 24. Tip If your board uses metric uits, use METRIC.TCH. 7

16 Chapter 2 Creatig a board Creatig a board usig a board template If you fid a board template that is similar to what you wat to use but eeds some modificatio, you ca customize it ad save it uder aother ame usig a.tpl extesio. For istructios o creatig a custom board template, see Custom templates i Chapter 4, Settig up the board i the OrCAD Layout User s Guide. Tip Note Note Oe beefit of usig a board template (.TPL) is that, i additio to cotaiig all the iformatio i DEFAULT.TCH, a board template cotais a board outlie, savig you the task of havig to draw oe yourself. To determie which of the board templates (.TPL) you wat to use, you ca view their illustratios i the OrCAD Layout Footprit Libraries maual, or you ca do the followig: From the Layout sessio frame s File meu, choose Ope. The Ope Board dialog box displays. Chage to the ORCADWIN\LAYOUT\DATA directory, chage the Files of type to All Files, select a board template (.TPL), the choose the Ope butto. The board template displays i Layout. Ispect the board template to determie if you wat to use it for your ew board. If ot, repeat the process as may times as ecessary to fid a.tpl file you wat to use, the close the file. If a board template has compoets (such as edge coectors), the you must have matchig parts with matchig referece desigators i your schematic desig i order for Layout to assig ets to the compoets. If the referece desigators do ot match, Layout will brig i a ew part, ad the compoets that are part of the board template will ot have ets assiged to them. 8

17 Methods to create a board To create a board usig a board template 1 Esure that a etlist with all footprits ad other ecessary iformatio has bee created. 2 Create a directory i which the schematic desig, etlist, ad board will coexist ad put the schematic desig (if you have it) ad etlist i it. OrCAD provides a directory (ORCADWIN\LAYOUT\DESIGN) for this purpose. 3 From the File meu, choose New. The Load Template File dialog box displays. 4 Select a board template (.TPL), the choose the Ope butto. The Load Netlist Source dialog box displays. 5 Select a etlist file (for example, desig_ame.mnl), the choose the Ope butto. The Save File As dialog box displays. 6 Specify a ame for the ew board (for example, desig_ame.max), the choose the Save butto. The AutoECO process begis. 7 If ecessary, respod to the Lik Footprit to Compoet dialog box (choose the dialog box s Help butto for a explaatio of the dialog box s optios). 8 AutoECO fiishes, ad you see the compoets i the desig widow. 9

18 Chapter 2 Creatig a board Importig a board usig the DXF to Layout traslator For istructios o creatig a board outlie ad savig it as a.dxf file i Visual CADD, ad o modifyig the MAXDXF iitializatio file, which specifies the mappig of data betwee DXF ad Layout formats, see the OrCAD Layout Visual CADD Tutorial. For istructios o usig Visual CADD, see the OrCAD Layout Visual CADD User s Guide. To import a board usig the DXF to Layout traslator 1 Esure that a etlist with all footprits ad other ecessary iformatio has bee created. 2 Create a directory i which the schematic desig, etlist, ad board will coexist ad put the schematic desig (if you have it) ad etlist i it. OrCAD provides a directory (ORCADWIN\LAYOUT\DESIGN) for this purpose. 3 Create a board outlie i Visual CADD (or i aother mechaical CAD applicatio), save it (ad ay other pertiet floor plaig iformatio) as a.dxf file, the put the.dxf file i the same directory as your schematic desig ad etlist. 4 From Layout s sessio frame, choose File, the Import, the DXF to Layout. The DXF to MAX dialog box displays. 5 I the Iput DXF File text box, use the Browse butto to locate ad select the.dxf file you created i step 3, the choose the Ope butto. Note If the.dxf file was created usig millimeters, the DXF to MAX result will be a metric board (.MAX). Therefore, your etlist must also be i millimeters, because Layout will ot read i a etlist created i iches if the board is i millimeters (ad vice versa). 6 I the Output Layout File text box, supply a ame for the output.max file. 10

19 Methods to create a board 7 Verify that MAXDXF.INI displays i the DXF.INI File text box ad that DEFAULT.TCH displays i the Techology File text box, the choose the Traslate butto. Layout combies the files ad displays the results of the traslatio i a text editor, such as Notepad. Close the text editor whe you re fiished viewig the traslatio results. 8 From Layout s sessio frame, choose File, the Ope. The Ope Board dialog box displays. 9 Locate ad select the.max file that you supplied the ame for i step 6, the choose the Ope butto. The board displays i Layout. 10 Review the board, esurig that the datum is where you wat it ad the drill chart is i a acceptable locatio (for example, to the right of the board outlie, to keep it out of the way of compoets that will load with the etlist). Whe the board is as you wat it, save it (usig a.max extesio) ad exit Layout. Tip You ca save the board you ve reviewed i step 10 as a board template (.TPL), so that you ca reuse it. For istructios o creatig a custom board template, see Custom templates i Chapter 4, Settig up the board i the OrCAD Layout User s Guide. 11 From the Layout sessio frame s File meu, choose New. The Load Template File dialog box displays. 12 Chage the Files of type to Board (*.MAX), locate ad select the.max file you saved i step 10, the choose the Ope butto. The Load Netlist Source dialog box displays. 13 Select a etlist file (for example, desig_ame.mnl), the choose the Ope butto. The Save File As dialog box displays. 14 Specify a ame for the ew board (for example, desig_ame.max), the choose the Save butto. The AutoECO process begis. 15 If ecessary, respod to the Lik Footprit to Compoet dialog box (choose the dialog box s Help butto for a explaatio of the dialog box s optios). For istructios o movig the datum, see the fial step of Creatig a board outlie o page 24. For istructios o movig the drill chart, see Movig the drill chart i Chapter 11, Post processig i the OrCAD Layout User s Guide. 11

20 Chapter 2 Creatig a board 16 AutoECO fiishes, ad you see the compoets i the desig widow. Importig a board usig the PRO-E to Layout traslator The PRO-E to Layout traslator ca be used to traslate Pro/ENGINEER Itermediate Drawig Format (IDF) files ito Layout. Note that IDF files come i pairs: the board file (.EMN) cotais the board outlie, keepouts, ad compoet placemets, while the library file (.EMP) cotais additioal data for each compoet placed i the board file, such as the compoet placemet outlie ad the compoet height. To import a board usig the PRO-E to Layout traslator 1 Esure that a etlist with all footprits ad other ecessary iformatio has bee created. 2 Create a directory i which the schematic desig, etlist, ad board will coexist ad put the schematic desig (if you have it) ad etlist i it. OrCAD provides a directory (ORCADWIN\LAYOUT\DESIGN) for this purpose. 3 Save your Pro/ENGINEER desig i IDF format, usig a.emn extesio for the board file ad a.emp extesio for the library file, the put the.emn ad.emp files i the same directory as your schematic desig ad etlist. 12

21 Methods to create a board 4 From Layout s sessio frame, choose File, the Import, the PRO-E to Layout. The PRO-E to Layout dialog box displays. 5 I the Iput IDF Board File text box, supply a ame for the Pro/ENGINEER board file (.EMN). 6 I the Iput IDF Library File text box, supply a ame for the Pro/ENGINEER library file (.EMP). Tip Mechaical Egieers will sometimes create a board outlie, height restrictio zoes, voids, ad route keepouts i a tool like Pro/ENGINEER, the trasmit that iformatio to the Electrical Egieer usig a IDF Board file. Sice there is o compoet placemet data, there will ot be a IDF Library file. I this case, simply leave the text box for the Iput IDF Library File blak. 7 I the Iput Techology or Layout File text box, supply a ame for the techology or layout file. Tip If you are creatig a ew Layout file, choose a techology file (.TCH) to use as a template. If you are brigig back to Layout a board that has udergoe thermal aalysis, put the ame of the origial Layout board file (.MAX) you modeled i the Iput Techology or Layout File text box. That way, if you have shifted compoet placemets to meet your heat dissipatio goals, the compoets i your origial Layout board file will be moved to their ew locatios. 8 I the Output Layout File text box, supply a ame for the output.max file. 9 Select the followig optios as desired, the choose the Traslate butto. Overwrite existig files Select this optio if you wat the output files to overwrite existig files without first promptig for your permissio. 13

22 Chapter 2 Creatig a board Ceter placed compoets If the placemet origi for critical compoets as defied by the Mechaical Egieer does ot match the placemet origi as defied by the Electrical Egieer, select this optio, which causes the cetroid of the Mechaical Egieer s part to overlay the cetroid of the Electrical Egieer s part. Note, though, that the referece desigator used for the part must match the referece desigator specified i your etlist. If it does ot, edit the part oce you have traslated the desig ito Layout format, but before you load your etlist. Oce the referece desigator matches your etlist, loadig the etlist provides the part with the required footprit, silkscree, ad electrical coectivity iformatio. Igore all compoets Select this optio if you wat to discard the compoet placemet iformatio i your IDF Library file. Do ot update board outlie or voids Select this optio if you chaged the board outlie (for example, durig thermal modelig), but you wat to keep the board outlie that s i your origial Layout file. 10 From the Layout sessio frame s File meu, choose New. The Load Template File dialog box displays. 11 Chage the Files of type to Board (*.MAX), locate ad select the ew.max file, the choose the Ope butto. The Load Netlist Source dialog box displays. 12 Select a etlist file (for example, desig_ame.mnl), the choose the Ope butto. The Save File As dialog box displays. 13 Specify a ame for the ew board (for example, desig_ame.max), the choose the Save butto. The AutoECO process begis. 14 If ecessary, respod to the Lik Footprit to Compoet dialog box (choose the dialog box s Help butto for a explaatio of the dialog box s optios). 15 AutoECO fiishes, ad you see the compoets i the desig widow. 14

23 Settig up board parameters 3 I Layout, you should set up the board s parameters before you begi placig compoets. The parameters are listed below, but ot all of them may be eeded for your board. Create a board outlie Set the uits of measuremet Set system grids Add moutig holes Defie the layer stack Set global spacig Defie padstacks Defie vias

24 Chapter 3 Settig up board parameters Note All of the items listed above ca be saved to board templates. For istructios o creatig a custom board template (.TPL), see Custom templates i Chapter 4: Settig up the board i the OrCAD Layout User s Guide. For iformatio o settig et properties, ad o the optios i the Edit Net dialog box, see Chapter 4: Settig up the board i the OrCAD Layout User s Guide. Creatig a board outlie Note Layout requires exactly oe board outlie, o the global layer. Tip Layout has a 50 mils default board outlie width, i order to provide clearace o plae layers for the copper of the plae to the edge of the board. Oe-half of the width is the pullback (25 mils i the default width), so set the board outlie s width to two times the pullback you would like. The cut is made dow the ceter of the board outlie obstacle. To create a board outlie 1 From the Tool meu, choose Dimesio, the choose Datum. Click o the lower left corer of the board outlie to place the datum (to provide a startig grid for compoet placemet). Press HOME to redraw the scree. Note Placig the datum i the lower-left corer of the board outlie gives you positive X, Y coordiates, while placig it i other corers gives you egative coordiates (i your reports ad post processig results). I additio, sice the board datum is used for all grids, if you move the datum after compoet placemet, your place, routig, ad via grids will all be affected. Ad, you may have difficulty replacig the datum at the precise locatio you moved it from. 2 Choose the obstacle toolbar butto. 3 From the pop-up meu, choose New, the from the pop-up meu, choose Properties. The Edit Obstacle dialog box displays. 4 From the Obstacle Type drop-dow list, select Board outlie. 5 I the Width text box, eter a value for the outlie s width. 16

25 Settig uits of measuremet 6 From the Obstacle Layer drop-dow list, select Global Layer, the choose the OK butto. The Edit Obstacle dialog box closes. 7 Move to the poit o the board at which you wat to start drawig the outlie, the click the left mouse butto to isert the first corer. Note Sice a board outlie must be a closed polygo, Layout automatically begis formig a closed area after you isert the first corer of the board outlie, ad automatically closes the polygo for you if you do t close it yourself. 8 Cotiue clickig the left mouse butto to isert corers. 9 After you click to isert the last corer, choose Fiish from the pop-up meu. Layout automatically completes the board outlie. Tip If you zoom i while drawig, you ca press C to put your curret cursor locatio i the ceter of the scree. Settig uits of measuremet I Layout, you ca set umeric data to display i mils, iches, micros, millimeters, or cetimeters. You ca chage these values as eeded (for example, you ca route the board i iches or mils, the cofirm pad locatios withi footprits i millimeters). Note If your board uses metric uits, you ca achieve the best precisio by usig the METRIC.TCH techology template. With your board ope i Layout, choose Load from the File meu, select METRIC.TCH, the choose the Ope butto. After METRIC.TCH loads, save your board. 17

26 Chapter 3 Settig up board parameters To set measuremet uits 1 Ope your board i Layout. 2 From the Optios meu, choose System Settigs. The System Settigs dialog box displays. 3 Select mils, iches, micros, millimeters, or cetimeters. 4 Choose the OK butto. Note Oce you decide o a measuremet uit, you should stick with it ad ot chage it i either your board or your schematic. If you back aotate to your schematic, the chage to aother measuremet uit, it may cause board corruptio problems. Settig system grids Usig the System Settigs dialog box, you ca set five distict grid settigs. The grid values that you assig determie the resolutio of the poiter locatio coordiates give i the status bar i the lower left corer. For example, if the obstacle tool is selected ad the Place grid is set to 100 mils, the coordiates that display are accurate to 100 mils. Grid values are i user-specified uits that you set i the Display Uits group box i the System Settigs dialog box. If you wat to use fractios i your grid values, eter a space character followig the iteger ad use a forward slash as the divisio character (for example, 8 1/3). You ca also use decimals for ratioal umbers. 18

27 Settig system grids Tip Here are some rules of thumb for settig the grids: For efficiet routig performace, the routig grid ad via grid should have the same value. The place grid must be a multiple of the routig ad via grids. The routig grid should ever be less tha 5 mils. The detail grid ca be set as low as 1 mil for better resolutio. Compoets are placed o the place grid usig the compoet datum, which is typically pad 1 (uless the compoet has bee modified). To set system grids 1 From the Optios meu, choose System Settigs. The System Settigs dialog box displays. 2 Set these optios, the choose the OK butto. Visible grid Assigs a display grid based o the X ad Y coordiates (for example, if you re usig mils, a settig of 200 would place a grid dot at every 200 mils). Detail grid Assigs a drawig grid (for lies ad text) based o the X ad Y coordiates. Place grid Assigs a compoet placemet grid based o the X ad Y coordiates. For greatest routig efficiecy, this value eeds to be a multiple of the routig grid. The datum, or origi, of footprits is costraied to this grid. Routig grid Assigs a grid used for routig (see the routig grid chart below for suggested settigs). Via grid Assigs a grid upo which you or the router ca place vias. 19

28 Chapter 3 Settig up board parameters The followig chart is a syopsis of routig grids ad how to use them i Layout. Routig grid Uses Compatible grids 25, 12 1 /2, 8 1 /3, ad 6 1 /4: 25, 12 1 /2 Use for less dese (usually.45 desity or greater) through-hole ad SMT boards, ad for routig oe track betwee IC pis. 8 1 /3 Use for a secodary grid o through-hole boards, ad for a primary grid o SMT boards. Use as a secodary grid with 25 mils grid oly if the 25 mils grid iitially routes 95% or better. 6 1 /4 Use for 6/6 techology, or deser oe-betwee boards. Compatible grids 20 ad 10: 20 Use for through-hole boards oly. This is the most efficiet way to route two tracks betwee IC pis. 10 Use for through-hole, two-betwee boards placed o a 50 mils grid, ad for SMT boards usig 10/10 techology. Also, use for special cases whe a 20 mils grid causes off-grid jogs. Compatible grids 25, 20, ad 10: 5 Use for extremely dese SMT boards that use 5 mils spacig ad 5 mils track width (for mixed ich ad metric techologies). Note Icompatible grids (such as 20 ad 25) should ot be mixed o the same board. If you fid it ecessary to do so, use a 5 mils grid for the fial reroute pass. Also, a via grid smaller tha the routig grid (for istace, a 5 mils via grid o a 25 mils grid board) icreases completio o difficult SMT boards. Of course, if a board is very dese, via sizes should by reduced to the miimum size possible, sice vias are resposible for much of the chael blockage durig routig. 20

29 Addig moutig holes to a board You ca add moutig holes to a board, ad you ca also save them i a board template (.TPL). Oce you add the moutig holes to the board, defie them as o-electrical. You ca still attach o-electrical moutig holes to the groud et. It s just that the o-electrical flag keeps the ECO process from removig them. Addig moutig holes to a board To add moutig holes to a board 1 Choose the compoet toolbar butto. 2 From the pop-up meu, choose New. The Add Compoet dialog box displays. 3 Choose the Footprit butto. The Select Footprit dialog box displays. 4 I the Libraries group box, select LAYOUT.LLB. Use the Add butto, if ecessary, to add this library to the list of available libraries. (LAYOUT.LLB resides i the LIBRARY directory.) 5 I the Footprits group box, select a moutig hole (OrCAD provides three: MTHOLE1, MTHOLE2, ad MTHOLE3). Choose the OK butto to close the Select Footprit dialog box. 6 Select the No-Electric optio, the choose the OK butto to close the Add Compoet dialog box. The moutig hole attaches to your cursor. 7 Place the moutig hole by clickig the left mouse butto. 21

30 Chapter 3 Settig up board parameters Tip To have a moutig hole thermal ito the plae layer, attach it to the et that is shorted to the plae layer. You ca do this after placemet. If you do t wat a pad o the top, bottom, ad ier layers, but eed clearace o the plae layers, place pads that are 1 mil i diameter o the top, bottom, ad ier layers. These 1 mil pads will be see by SmartRoute ad avoided, ad will be drilled out whe drill holes are drilled through the board. For the plae layers, you eed to defie pads that are 15 mils larger tha the drill hole, to provide adequate clearace from the drill. Pad size o plae layers is used to defie clearace. Plae layers are represeted i the iverse, i Layout. Defiig the layer stack For istructios o how to copy a padstack layer to a ewly defied layer (for example, a additioal plae layer), see Copyig padstack layers i Chapter 14, Creatig ad editig footprits i the OrCAD Layout User s Guide. Routig ad documetatio layers are defied i the Layers spreadsheet. Usig the spreadsheet, you ca defie the umber of routig layers that will be used for the board. If you pla to have a board with four routig layers (TOP, BOTTOM, INNER1, ad INNER2) ad two plae layers (POWER, GROUND), the you eed to defie the layers i a techology template (.TCH) or a board template (.TPL). Tip It is better to have too may routig or plae layers defied tha too few (if you re usure of the umber you will eed) before readig i a etlist, because you ca decrease the umber of the layers later, by desigatig them as uused. After defiig the layer stack, you ca save the iformatio to a board template (.TPL) for use i future boards. 22

31 Defiig global spacig values To defie layers for routig 1 Choose the spreadsheet toolbar butto, the choose Layers. The Layers spreadsheet displays. 2 Review the type assigmets for the routig layers ad double-click i the Layer Name colum of a layer you wat to modify. The Edit Layer dialog box displays. 3 I the Layer Type group box, select the desired optio (for example, to disable a layer for routig, select Uused Routig; to defie a additioal plae layer, select Plae Layer). 4 If you chaged a routig layer to a plae layer, chage the Layer LibName to PLANE. 5 Choose the OK butto. Note Do ot delete layers from the Layers spreadsheet. To disable a layer, double-click o it, the specify it as Uused Routig i the Edit Layer dialog box. Defiig global spacig values Global spacig values set rules for spacig betwee the various objects o the board. You ca defie global spacig values for the board usig the Edit Spacig dialog box, which is accessed from the Route Spacig spreadsheet (choose the spreadsheet toolbar butto, choose Strategy, the choose Route Spacig). You ca save spacig requiremets i a board template (.TPL). Uiform spacig requiremets per layer reduce processig time. Tip To globally assig the same spacig to all layers, double-click i the Layer Name title cell i the Route Spacig spreadsheet. Whe the Edit Spacig dialog box displays, eter a value i the appropriate text box (for example, eter a value for Track to Track Spacig), the choose the OK butto. 23

32 Chapter 3 Settig up board parameters To defie global spacig values 1 Choose the spreadsheet toolbar butto, choose Strategy, the choose Route Spacig. The Route Spacig spreadsheet displays. 2 Double-click o the layer you wat to modify. The Edit Spacig dialog box displays. 3 Set these optios, the choose the OK butto. Track to Track Spacig Tracks are defied as ay routed track ad copper obstacles (such as keepouts ad place outlies). Track-to-track spacig specifies the miimum space required betwee tracks of differet ets, ad betwee tracks ad obstacles of differet ets. Track to Via Spacig Track-to-via (ad obstacle-to-via) spacig specifies the miimum space required betwee vias ad tracks of differet ets. Track to Pad Spacig Track-to-pad (ad obstacle-to-pad) spacig specifies the miimum space required betwee pads ad tracks of differet ets. Via to Via Spacig Specifies the miimum space required betwee vias of differet ets. Via to Pad Spacig Specifies the miimum space required betwee pads ad vias of the same et (as well as differet ets, which is the usual case). For istace, to keep a distace of 25 mils betwee your SMT pads ad the faout vias coected to the pads, set Via to Pad Spacig to 25. Pad to Pad Spacig Specifies the miimum space required betwee pads of differet ets. 24

33 Defiig padstacks Padstacks defie the pads of the footprit. They possess properties o each layer of the board, such as shape ad size. If you are usig the stadard Layout footprit libraries, or if you have made your ow footprits usig Layout stadards, you have used padstacks T1 through T7 to create most of the stadard through-hole compoets i your library. Note Do t ame your custom padstacks usig the ames T1 through T7, because they will be overwritte by techology template padstacks wheever you load a techology template. Also, be sure to defie through-hole padstacks o all layers, icludig uused layers. Otherwise, you may uitetioally create blid or buried vias. Surface-mout pads, o the other had, are ot defied o iteral layers. You ca create ew padstacks whe you set up the board, or i the footprit library. You must defie padstacks before you assig them to footprits. You ca defie ew padstacks by copyig ad editig existig padstacks i the Padstacks spreadsheet. The, you ca assig them to footprits or footprit pis. After you create ew padstacks, you ca save them i a board template (.TPL) for use with future boards. Defiig padstacks For iformatio o assigig padstacks to footprits or footprit pis, ad o editig padstacks, see Chapter 14, Creatig ad editig footprits i the OrCAD Layout User s Guide. To create a ew padstack 1 Choose the spreadsheet toolbar butto, the choose Padstacks. The Padstacks spreadsheet displays. 2 Select a padstack ad choose Properties from the pop-up meu. The Edit Padstack dialog box displays. 3 Type a ew ame for the padstack i the Padstack text box, edit the other optios to chage the size or shape as desired, the choose the OK butto. 4 Make specific layer defiitios for the padstack for the drill ad plae layers. 25

34 Chapter 3 Settig up board parameters Usig vias You ca defie the types of vias that you wat to use whe routig your board, either vias or free vias. Free vias (deoted by the letters FV) are igored by Layout s board cleaup routies, so you ca place them o your board ad have them stay there, as log as they are attached to a et. They are preserved through AutoECO, uless the et or routed track they are coected to is etirely deleted or removed from the board. Layout regards free vias as stad-aloe compoets: you ca shove them, place them i isolatio (free of tracks), or coect them to multiple tracks o the same et. You ca use free vias for special purposes, such as zero-legth faouts of ball grid array (BGA) compoets ad the stitchig of plae layers. Layout provides oe defied via ad fiftee udefied vias. You defie additioal vias i the Edit Padstack dialog box (from the Padstacks spreadsheet) to make them available for routig. The, usig the Assig Via dialog box (from the Nets spreadsheet), you ca assig a specific via to be used whe routig a particular et. Note Selectig a via for a particular et does ot prohibit ay other et from usig that via. The assigmets made i the Assig Via dialog box simply override, for selected ets, the Use All Via Types optio set i the Route Settigs dialog box (from the Optios meu, choose Route Settigs). Therefore, you ca select the Use All Via Types optio ad still assig specific vias to specific ets usig the Assig Via dialog box. For example, if you wat to use Via 1 for all of your sigal routig, but you wat to restrict VCC to Via 2 ad GND to Via 3, you would start by selectig the Use All Via Types optio to make the defied vias available for routig. The you would select VCC i the Nets spreadsheet, choose Assig Via per Net from the pop-up meu, ad select Via 2 i the Assig Via dialog box. Fially, you would select GND i the Nets spreadsheet, choose Assig Via per Net from the pop-up meu, ad select Via 3 i the Assig Via dialog box. 26

35 Usig vias Tip If you do t select the Use All Via Types optio i the Route Settigs dialog box, you must specifically assig vias to ets that eed their via types restricted. Otherwise, the router chooses what it cosiders the best via, usig its stadard criteria: the layer(s) the via is defied o ad its size compared to track size. To make a via available for geeral routig 1 Choose the spreadsheet toolbar butto, the choose Padstacks. The Padstacks spreadsheet displays. 2 Select a uused via ad choose Properties from the pop-up meu. The Edit Padstack dialog box displays. 3 Type a ew ame for the via (for a free via, for example, you could use the ame POWERVIA) ad edit the other optios to chage the size or shape as desired, the choose the OK butto. 4 From the Optios meu, choose Route Settigs. The Route Settigs dialog box displays. 5 Select the Use All Via Types optio ad choose the OK butto. 6 Close the Padstacks spreadsheet. To assig a via to a et 1 Choose the spreadsheet toolbar butto, the choose Nets. The Nets spreadsheet displays. 2 Select the et to which you wat to assig a via. 3 From the pop-up meu, choose Assig Via per Net. 4 Select the desired via ad choose the OK butto. 5 Close the Nets spreadsheet. Note You do t have to select the Use All Via Types optio i the Route Settigs dialog box to assig a via to a particular et. For iformatio o chagig the defiitio of a via, see Chagig vias i Chapter 8, Routig the board i the OrCAD Layout User s Guide. 27

36 Chapter 3 Settig up board parameters To place a via 1 Choose oe of the routig toolbar buttos. 2 Begi routig the et o which you wat to place a via. 3 Click the left mouse butto to place a vertex (a corer). 4 From the pop-up meu, choose Add Via. or From the pop-up meu, choose Add FreeVia. 28

37 Placig compoets 4 Oce you have set up your board by followig the procedures i Chapter 3, Settig up board parameters, you ca begi compoet placemet.

38 Chapter 4 Placig compoets Preparig the board for compoet placemet Before you begi placig compoets maually, it is importat to set up the board properly. Use the list below as a preplacemet checklist. Check the board, place, ad isertio outlies Check the place grid Check mirror layer or library layer settigs Weight ad color-code ets Check gate ad pi data Check preplaced compoets ad secure them o the board usig the Lock or Fix commads Create compoet height keepis ad keepouts, or group keepis ad keepouts Checkig the board, place, ad isertio outlies The board outlie is used by Layout to determie the overall board placemet boudary, ad it must be preset o the global layer of the board. It ca be defied as part of the board template, or you ca create it whe you set up the board. A place outlie defies the extet of the area that is reserved for a compoet s placemet. Each footprit must have oe. Layout uses place outlies to determie whether ay compoet spacig violatios occur durig placemet. A place outlie ca be assiged a height ad a layer. Oe or more place outlies of differet heights ad shapes, ad o differet layers, ca be used to more closely represet the placemet area required by a compoet. 30

39 Preparig the board for compoet placemet Tip If you select the Show 3D Effects optio i the User Prefereces dialog box (accessed by choosig User Prefereces from the Optios meu), ad have assiged a height for a place outlie, Layout displays a three-dimesioal image represetig the compoet s height, ad idicates the height o the image. A isertio outlie is optioal, ad is used by Layout to provide clearace for auto-isertio machies. Note A isertio outlie ca overlap aother isertio outlie, but a place outlie caot overlap aother place outlie. To check board, place, ad isertio outlies 1 Choose the spreadsheet toolbar butto, the choose Obstacles. The Obstacles spreadsheet displays. 2 Review the Obstacle Type colum i the spreadsheet to check that the board, place, ad isertio outlies have the correct width ad height, ad that they are o the correct layer (for example, the board outlie must be o the global layer). 3 Close the Obstacles spreadsheet so that you ca view the board outlie i the desig widow. If there are cutouts i the board outlie where o compoets should be placed, you eed to create zero-height keepouts iside the cutouts, to esure that o compoets are placed i these areas. For iformatio o creatig height keepouts, see Creatig height or group keepis ad keepouts o page 44. For iformatio o creatig board outlies, see Chapter 3, Settig up board parameters. Checkig the place grid The place grid affects the spacig used for compoet placemet. Before placig compoets, check the settig for the place grid i the System Settigs dialog box. The default placemet grid is 100 mils, with which you ca use routig grids of 25 mils, 20 mils, 12 1 /2 mils, 10 mils, 8 1 /3 mils, 6 1 /4 mils, or 5 mils (because 100 mils is a multiple of these values). The stadard metric placemet grids are 2 mm, 1 mm, ad 0.5 mm. If you use a 50 mils or 25 mils placemet grid, you ca use routig grids of 25 mils, 12 1 /2 mils, 10 mils, 8 1 /3 mils, or 6 1 /4 mils. 31

40 Chapter 4 Placig compoets To check the place grid settig 1 From the Optios meu, choose System Settigs. The System Settigs dialog box displays. 2 Check the value i the Place grid text box, chage it if ecessary, the choose the OK butto. Checkig mirror layers ad library layers You ca check which layers are set up to have their obstacles, padstacks, ad text mirrored to aother layer durig compoet placemet, ad chage the settigs, if ecessary. For example, all of the TOP layer compoets ca be automatically mirrored to the BOTTOM layer, ad vice versa. Typically, all ier layers of a desig (INNER1, INNER2, ad so o) correspod to the INNER library ame, ad all plae layers of a desig (POWER, GROUND) correspod to the PLANE library ame. All other layers typically have a oe-to-oe correspodece; for example, the BOTTOM layer i the desig correspods to the BOTTOM library ame. To check the mirror layer ad library layer settigs 1 Choose the spreadsheet toolbar butto, the choose Layers. The Layers spreadsheet displays. 2 Check the settigs i the Mirror Layer colum agaist the settigs i the Layer Name colum, to esure that the layers are set to mirror to their opposite layers. 3 Double-click o each layer to brig up the Edit Layer dialog box, check that the Layer LibName is set appropriately, the press ESC to close the dialog box. 32

41 Preparig the board for compoet placemet Weightig ad color-codig ets Layout places a higher priority o keepig higher-weighted ets ad their compoets together durig placemet. I Layout, ets are weighted o a liear scale from 0 to 100. To weight ad highlight ets 1 Choose the spreadsheet toolbar butto, the choose Nets. The Nets spreadsheet displays. 2 Double-click i the Net Name cell that correspods to a et whose weight you wat to chage, or that you wat to highlight. The Edit Net dialog box displays. 3 To chage the weight for a et, type i a ew weight i the Weight text box, the choose the OK butto. or Use the scroll bar at the left of the text box to chage the umber, the choose the OK butto. The ew umber shows i the Weight colum of the spreadsheet. 4 To highlight a et, select the Highlight optio i the Edit Net dialog box, the choose the OK butto. The et shows i the highlight color. Tip To assig a color to a et other tha the highlight color, click i the Color cell i the Nets spreadsheet, choose Chage Color from the pop-up meu, the select a color from the color palette displayed. For iformatio o settig et properties, see Chapter 4, Settig up the board i the OrCAD Layout User s Guide. To color-code a et 1 I the Nets spreadsheet, select the et(s) to which you wat to assig a color. 2 From the pop-up meu, choose Chage Color, the select a color from the palette that displays. 33

42 Chapter 4 Placig compoets Checkig gate ad pi iformatio A package is the electroic gate ad pi iformatio associated with a compoet (as opposed to a footprit, which is the iformatio regardig the physical characteristics of a compoet). The iformatio i the Packages spreadsheet is used to determie whether you ca swap gates betwee idetical compoets or oly withi a compoet, ad how the gates are arraged withi a part. To check gate ad pi iformatio 1 Choose the spreadsheet toolbar butto, the choose Packages. The Packages spreadsheet displays. 2 Verify that the followig iformatio i the spreadsheet is correct, the close the spreadsheet. Package Name A text strig that desigates the ame of the electrical package. Gate Name Usually a alpha character that desigates which gate each pi belogs to. Each gate i a package must have a uique gate ame, ad all of the pis i the same gate must share the same gate ame. Pi Name Idetifies each pi i terms of its electrical characteristics (INA, INB, ad so o) so that Layout ca swap gates correctly. Each pi withi a gate must have a uique idetifier. For swappable gates, correspodig pis must have idetical pi ames. Gate Group A iteger used to determie which gates ca be swapped. Ay gates that are assiged to the same Gate Group are swappable. Gate Group 0 is a special case that represets a o-swappable gate. 34

43 Preparig the board for compoet placemet Pi Group A iteger used to determie which pis ca be swapped. Ay pis that are assiged to the same Pi Group are swappable. Pi Group 0 is a special case that represets a o-swappable pi. Pi Type Usually set to Noe for stadard TTL-type pis, which idicates that the pi is ot part of a ECL et, ad is ot a source, a termiator, or a load. You ca assig a Pi Type of Noe, Source, Termiator, or Load. Securig preplaced compoets o the board If your desig has compoets or footprits that were placed at the schematic level or as part of the template, you should esure that they were placed properly before you begi placig additioal compoets. Preplaced compoets may iclude coectors, moutig holes, memory arrays, predefied circuits, aligmet targets, ad compoets that must be placed i specific locatios due to mechaical or temperature restrictios. Oce you are satisfied that the preplaced compoets are properly placed, you must affix them to the board usig the Fix or Lock commads. Otherwise, they may be moved iadvertetly whe you are placig other compoets. The Lock commad is temporary; you ca easily override the commad. However, the Fix commad must be disabled i the Edit Compoet dialog box. The Fix commad is iteded for parts like coectors ad moutig holes that eed to be placed permaetly i specific locatios. 35

44 Chapter 4 Placig compoets To lock compoets o the board 1 Choose the compoet toolbar butto. 2 To select all of the preplaced compoets, hold the left mouse butto dow while you drag the mouse, drawig a rectagle aroud the compoets. Release the left mouse butto. Each selected compoet is highlighted. 3 To temporarily lock compoets i a locatio, choose Lock from the pop-up meu. or To permaetly fix compoets i a locatio, choose Fix from the pop-up meu. To override the Lock commad 1 Select a few locked compoets. A dialog box askig Oe or more compoets locked. Override? displays. 2 Choose the OK butto. The compoets are ulocked. To override the Fix commad 1 Choose the spreadsheet toolbar butto, the choose Compoets. The Compoets spreadsheet displays. 2 Double-click o the row for the compoet that you wat to move. The Edit Compoet dialog box displays. 3 I the Compoet flags group box, deselect the Fixed optio, the choose the OK butto. 36 Creatig height or group keepis ad keepouts You ca restrict compoet placemet based o physical costraits usig the Comp height keepi or Comp height keepout obstacle types. A height keepi cotais all compoets at or above a specified height, while a height keepout excludes all compoets at or above a specified height.

45 Preparig the board for compoet placemet You ca also restrict placemet based o group umber (assiged i the schematic) usig the Comp group keepi or Comp group keepout obstacle types. A group keepi cotais all the compoets i a specified group, while a group keepout excludes all the compoets i a specified group. To create keepis ad keepouts 1 Choose the obstacle toolbar butto. 2 From the pop-up meu, choose New. 3 Draw a rectagle that defies the desired keepi or keepout area. 4 Double-click o the rectagle. The Edit Obstacle dialog box displays. 5 I the Obstacle Type drop-dow list, select Comp height keepi or Comp height keepout. I the Height text box, eter a umber correspodig to the height of the compoets you wat to iclude or exclude ad choose the OK butto. or I the Obstacle Type drop-dow list, select Comp group keepi or Comp group keepout. I the Group text box, eter a umber correspodig to the group umber of the compoets you wat to iclude or exclude, the choose the OK butto. 6 From the pop-up meu, choose Fiish. If you created a compoet height restrictio, the rectagle displays the height umber ad the words Comp keepi or Comp keepout. If you created a compoet group restrictio, the rectagle displays the group umber ad the words Group umber keepi or Group umber keepout. Tip If your keepis ad keepouts do t display ay idetifyig text (as described i step 6), you may have to eable the Show 3D Effects optio. To do so, choose User Prefereces from the Optios meu. I the User Prefereces dialog box, select the Show 3D Effects optio, the choose the OK butto. 37

46 Chapter 4 Placig compoets Loadig a placemet strategy file Strategy files set up your display (so you ca see what you eed to see durig compoet placemet) by highlightig appropriate elemets such as place outlies, electrical coectios, ad referece desigators, ad makig irrelevat elemets (such as plae layers) ivisible. OrCAD recommeds loadig the strategy file PLSTD.SF before performig maual placemet. To load a placemet strategy file 1 From the File meu, choose Load. The Load File dialog box displays. 2 If ecessary, chage Files of type to Strategy. 3 Select PLSTD.SF from the list ad choose the Ope butto. Disablig the power ad groud ets If the power ad groud ets are ot critical to placemet, disable routig for all ets attached to plae layers. This sigificatly improves system performace durig placemet, as these (typically) large ets ofte have o bearig o placemet. To disable routig for ets attached to plae layers 1 Choose the spreadsheet toolbar butto, the choose Nets. The Nets spreadsheet displays. 2 Usig the CTRL key, select the ets that are attached to plae layers (usually, GND ad VCC). 3 From the pop-up meu, choose Eable<->Disable. I the Nets spreadsheet, the Routig Eabled colum for the ets chages to No. 38

47 Placig compoets maually There are several commads available i Layout to assist you i maually placig compoets o a board. You ca place compoets oe at a time or i groups. Use the Queue For Placemet commad to make a compoet or group of compoets available for placemet based o a set of criteria (referece desigator, footprit ame, or first letters with wildcards), the place the compoets idividually usig the Select Next commad. To place compoets idividually 1 Choose the compoet toolbar butto. 2 From the pop-up meu, choose Queue For Placemet. The Compoet Selectio Criteria dialog box displays. Note The Queue For Placemet commad ad the Select Ay commad display the same Compoet Selectio Criteria dialog box, but the commads work differetly. The Queue For Placemet commad makes certai compoets available for placemet i cojuctio with usig the Select Next commad. The Select Ay commad, o the other had, actually selects specified compoets or groups for placemet ad attaches them to your cursor. 3 Eter the referece desigator (or other criteria) of the compoet that you wat to place i the appropriate text box ad choose the OK butto. (Choose the dialog box s Help butto for iformatio o the optios i the dialog box.) 4 From the Edit meu, choose Select Next. The compoet saps to the cursor. If you selected a group (such as all compoets begiig with the letter U), the the compoet with the greatest umber of coectios that meets the specificatio saps to the cursor. 5 Drag the compoet to the desired locatio ad click the left mouse butto to place it. Placig compoets maually For iformatio o matrix placemet, movig compoets, ad editig compoets, see Chapter 7, Placig ad editig compoets i the OrCAD Layout User s Guide. Tip You ca specify more tha oe compoet usig wildcards: use a asterisk (*) as a substitute for multiple characters ad a questio mark (?) as a substitute for a sigle character. For example, if you eter U*, you will select all compoets with referece desigators begiig with the letter U. 39

48 Chapter 4 Placig compoets Selectig the ext compoets for placemet Use the Place commad o the pop-up meu to display a dialog box that lists the compoets yet to be placed. If you made compoets available for placemet accordig to certai criteria (usig the Compoet Selectio Criteria dialog box), Layout displays oly the compoets that remai to be placed that meet those criteria. From this list, you ca select the ext compoet that you wat to place. The default selectio that displays i the dialog box is the oe that Layout would automatically choose if you had used the Select Next commad. You ca accept the default, or eter a ew choice. To select the ext compoet for placemet usig Select Next 1 Choose the compoet toolbar butto. 2 From the pop-up meu, choose Place. The Select Next dialog box displays. 3 Select a compoet for placemet, the choose the OK butto. Placig compoet groups You ca assig fuctioally related compoets to groups at the schematic level. Whe you specify the group umber (as assiged i the schematic) i the Compoet Selectio Criteria dialog box, the compoets assiged to the group sap to the cursor for placemet. To place a compoet group 1 Choose the compoet toolbar butto. 2 From the pop-up meu, choose Select Ay. The Compoet Selectio Criteria dialog box displays. 40

49 Checkig placemet 3 Eter the group umber, as assiged at the schematic level, i the Group Number text box ad choose the OK butto. The group of compoets saps to the cursor. 4 Click the left mouse butto to place the compoets o the board. Miimizig coectios to optimize placemet Use the Miimize Coectios commad to evaluate the coectios withi a et ad fid the shortest route for the et (ratsest) based o the placemet of the pis or compoets o the board. Whe othig is selected, Miimize Coectios is a global commad; it affects the etire board each time you apply it. However, if you have selected oe or more compoets, Miimize Coectios oly affects the ets attached to the selected compoets. You ca also select just a sigle et ad miimize the coectio legth o that et oly. To use the Miimize Coectios commad 1 Choose the compoet toolbar butto. 2 If desired, select the appropriate compoet(s) or et(s). 3 From the pop-up meu, choose Miimize Coectios. Checkig placemet You should check the placemet of a board usig Placemet Spacig Violatios, the desity graph, ad the placemet iformatio i the Statistics spreadsheet. 41

50 Chapter 4 Placig compoets For iformatio o how to use the error tool to get more iformatio about reported errors, see Chapter 6, Fiishig the board. Usig Placemet Spacig Violatios Before you route the board, you should ru Placemet Spacig Violatios, which looks for compoet-to-compoet spacig violatios ad other placemet errors, such as compoets that violate height restrictios, isertio outlies, or grid restrictios. Tip Placemet Spacig Violatios uses compoet outlies to determie whether there is a spacig violatio. Therefore, compoet outlies should ecompass the etire area of the IC or discrete compoet, icludig such objects as piout patters ad sockets. Ay problem foud by Placemet Spacig Violatios is marked with a circle. You ca fid out the ature of the problem by choosig the query toolbar butto, which brigs up the query widow. The, whe you choose the error toolbar butto ad select the error, the iformatio about the error displays i the query widow. To check placemet spacig violatios 1 From the Auto meu, choose Desig Rule Check. The Check Desig Rules dialog box displays. 2 Choose the Clear All butto. 3 Select the Placemet Spacig Violatios optio, the choose the OK butto. Layout checks the board for compoet placemet violatios ad marks ay errors with circles. 42

51 Checkig placemet Usig the desity graph The desity graph displays a graphical represetatio of the coectio desity of your board. Usig colors ragig from blue ad gree (acceptable desity) to pik ad red (very dese), the desity graph represets the degree of difficulty that will be faced i routig the board. The desity graph aalyzes all routig layers, routed tracks, widths of tracks, spacig rules, DRC settigs, ad coectios to calculate the available routig chaels. It shows the crossig cout at each locatio of the board i relatio to how much of each cell is beig filled by a pad, track, or coectio. There are two kids of data show o the desity graph: the board desity at each locatio (the umber of pads ad coectios i a give area of the board), ad the track desity (the track desity i each chael), show as bar graphs at the top ad right. To ope the desity graph 1 From the View meu, choose Desity Graph. The desity graph widow displays. 2 To retur to the desig widow, choose Desig from the View meu. Note A small amout of red i the desity graph is acceptable, but you should attempt to keep the percetage of red below 25%, because a board that is more tha 25% red is likely to ecouter serious routig difficulties. 43