Autodesk Moldflow Insight AMI Undeerfill Encapsulation

Transcription

1 Autodesk Moldflow Insight 2012 AMI Undeerfill Encapsulation

2 Revision 1, 22 March This document contains Autodesk and third-party software license agreements/notices and/or additional terms and conditions for licensed third-party software components included within the product. These notices and/or additional terms and conditions are made a part of and incorporated by reference into the Autodesk Software License Agreement and/or the About included as part of the Help function within the software.

3 Contents Chapter 1 Underfill Encapsulation analysis Chapter 2 Underfill Encapsulation analysis types and analysis technologies Underfill Encapsulation analysis types and analysis technologies Setting up an Underfill Encapsulation analysis Dynamic dispensing for Underfill Encapsulation set up Underfill Encapsulation analysis types and analysis technologies Process Settings Wizard dialog Underfill Encapsulation Settings Underfill Encapsulation Advanced Options dialog Underfill Encapsulation process settings dialog Chapter 3 Modeling for Underfill Encapsulation analysis Chapter 4 Dynamic dispensing for Underfill Encapsulation Dynamic dispensing for Underfill Encapsulation Dynamic dispensing for Underfill Encapsulation set up iii

4 Chapter 5 Dispensing locations Dispensing locations Setting up underfill dispensing locations Dispensing locations Dispensing Location dialog Dispensing controller dialog Dispensing data dialog Chapter 6 Shape factor calculation for underfill encapsulation Chapter 7 Underfill encapsulant materials Underfill encapsulant materials Checking the properties of the underfill encapsulant Underfill encapsulant materials Underfill Encapsulant dialog - Description Underfill Encapsulant dialog - Recommended Processing Underfill Encapsulant dialog - Rheological Properties Underfill Encapsulant dialog - Thermal Properties Underfill Encapsulant dialog - Reaction Kinetics Properties Underfill Encapsulant dialog - Surface Tension Properties Underfill Encapsulant dialog - Filler Properties iv

5 Underfill Encapsulation analysis 1 The Underfill Encapsulation analysis is used to analyze the flow of the encapsulant material in the cavity, between the chip and the substrate during the underfill encapsulation process. NOTE: For analysis of a pressurized underfill process, use Microchip Encapsulation. Flip chips are sometimes used for high-density electronic packaging. Flip chips offer the advantage of an area array which interconnects the chip and substrate. A weakness in the flip chip process is the solders that typically connect the chip to the board. During service, the solders can be damaged, mainly from the stresses associated with the temperature change of the package. Underfill encapsulation is the process of filling the cavity between the chip and the substrate with a thermoset encapsulant. This helps to protect the solders during service. In most cases, underfill encapsulation is done by dispensing the encapsulant material along the periphery of the chip. Capillary force drives the encapsulant through the space between the chip and the board. During Underfill Encapsulation, each injection location is open at a different time because of the time delay when the dispensing head moves around the edge of the chip for the dispensing. It is often common to find that dispensing is done over several passes to avoid excessive spreading of encapsulant in the dispensing area when a large amount of encapsulant is dispensed all at once. This is known as dynamic dispensing. The Dynamic Dispensing analysis option in the Process Settings Wizard enables you to simulate this situation. 1

6 Underfill Encapsulation analysis types and analysis technologies 2 The following table shows the available analysis technologies for an Underfill Encapsulation analysis. Table 1: Underfill Encapsulation process and analysis types Analysis Type Analysis Technology Fill+Pack Underfill Encapsulation analysis types and analysis technologies Setting up an Underfill Encapsulation analysis The following table summarizes the setup tasks required to prepare an Underfill Encapsulation analysis. Setup task Analysis technology Modeling for Underfill Encapsulation analysis on page 7 Importing a C-MOLD *.fem file Molding processes Analysis sequence Selecting a material 1 Dispensing locations on page 11 Process settings 1 Select an encapsulation molding compound when selecting a material for this analysis. 2 Underfill Encapsulation analysis types and analysis technologies

7 Dynamic dispensing for Underfill Encapsulation set up NOTE: The option to Perform dynamic analysis is available only for 3D models. Make sure you have assigned nodes along your dispensing path as injection locations, and you know which one will be the start of the dispensing path and which one will be the end. It is recommended that all nodes on the injection plane along the dispensing path have been assigned as injection locations. NOTE: A minimum of 4 injection locations are required on each injection plane. To set up dynamic dispensing, first you will define the properties associated with the start and end nodes, and then you will assign the start and end nodes. 1 Click Boundary Conditions tab > Dispensing panel > Set Controller to open the Set Dispensing controller dialog. 2 Click Edit to open the Dispensing controller dialog. 3 In the Dispensing controller dialog, in the Start node or end node of the pass section, select Start node from the dropdown menu, and type a unique name for the start node properties in the Name box. 4 Click Edit data to open the Dispensing data dialog. 5 Decide how many dispensing passes you would like to perform and the volume of encapsulant you would like to dispense in each pass, and enter the information in the relevant boxes. Make sure that the start time of the first pass is 0, and that the start time of all subsequent passes is after the end time of the previous pass. Click OK to close the Dispensing data dialog, then click OK again to close the Dispensing controller dialog. 6 In the Set Dispensing controller dialog, if you haven't already created an end node property, click New to create one. 7 In the Start node or end node of the pass section, select End node from the dropdown menu, type a unique Name for the end node properties, and click OK. The start node properties, end node properties, and number of passes have now been defined. Now you need to assign these properties to your chosen start and end nodes: 8 In the Set Dispensing controller dialog, select the start node properties you defined, then click on your model to select the start node of your dispensing path (this node must already have been defined as an injection location). Underfill Encapsulation analysis types and analysis technologies 3

8 A cross will appear on the selected node. The orientation of the cross is irrelevant, but confirm that the center of the cross is superimposed on your selected start node. 9 In the Set Dispensing controller dialog, select the end node properties you defined, then click on your model to select the end node of your dispensing path (this node must already have been defined as an injection location). A cross will appear on that node. The orientation of the cross is irrelevant, but confirm that the center of the cross is superimposed on your selected end node. 10 Close the Set Dispensing controller dialog by clicking on the close dialog cross in the top right hand corner. 11 Click Home tab > Molding Process Setup panel > Process Settings and activate dynamic dispensing by clicking on the Perform dynamic analysis checkbox, then click OK. 12 Once you have set all your other processing conditions, click Start Analysis in the Study Tasks pane, to start the simulation. Underfill Encapsulation analysis types and analysis technologies Use this dialog to specify settings for an Underfill Encapsulation analysis. Process Settings Wizard dialog Underfill Encapsulation Settings This page of the Process Settings Wizard is used to specify the underfill encapsulation related process settings for the analysis sequence. To access this dialog, ensure that the molding process has been set to Underfill Encapsulation. Click (Home tab > Molding Process Setup panel > Process Settings) to open the Underfill Encapsulation Settings dialog. Initial encapsulant temperature Initial encapsulant conversion Substrate temperature Curing temperature Specify the temperature of the encapsulant at the start of the process as it enters the chip cavity. Specify the initial conversion (curing) level of the encapsulant before the start of the process. Specify the temperature of the substrate during the process. The temperature at which a thermoset material will become sufficiently cross-linked from heating to form a solid, or cure. 4 Underfill Encapsulation analysis types and analysis technologies

9 Curing time Dynamic dispensing analysis Advanced options... The time taken for a thermoset material to become sufficiently cross-linked from heating to form a solid and freeze. Check this box to enable dynamic dispensing. Dynamic dispensing allows you to simulate underfill encapsulation dispensing that is completed over several passes, and where each injection location is open at a different time to account for the time delay during dispensing. Displays the advanced options for the analysis. Underfill Encapsulation Advanced Options dialog This dialog is used to specify the underfill encapsulation analysis related advanced options for the analysis sequence. To access this dialog, ensure that you have selected the Underfill Encapsulation process, click (Home tab > Molding Process Setup panel > Process Settings), then click Advanced options. Underfill encapsulant Solver parameters Click Edit to edit the properties of the default underfill encapsulant, or click Select to choose an alternate underfill encapsulant from the supplied database. Allows you to select and edit the solver parameters to be used during the analysis. Underfill Encapsulation process settings dialog The Underfill Encapsulation process settings dialog is used to specify default values for the analysis inputs to an Underfill Encapsulation analysis. To access this dialog, click Tools tab > Databases panel > New, select Geometry/Mesh/BC from the Category drop-down menu and select Dispensing location from the Property type menu. Curing temperature Curing time The temperature at which a thermoset material will become sufficiently cross-linked from heating to form a solid, or cure. The time taken for a thermoset material to become sufficiently cross-linked from heating to form a solid and freeze. Underfill Encapsulation analysis types and analysis technologies 5

10 Initial encapsulant temperature Initial encapsulant conversion Substrate temperature Dynamic dispensing analysis Specify the temperature of the encapsulant at the start of the process as it enters the chip cavity. Specify the initial conversion (curing) level of the encapsulant before the start of the process. Specify the temperature of the substrate during the process. Check this box to enable dynamic dispensing. Dynamic dispensing allows you to simulate underfill encapsulation dispensing that is completed over several passes, and where each injection location is open at a different time to account for the time delay during dispensing. NOTE: The values used for the current analysis sequence may be changed by entering the desired values on the Process Settings Wizard Underfill Encapsulation Settings dialog. 6 Underfill Encapsulation analysis types and analysis technologies

11 Modeling for Underfill Encapsulation analysis 3 There are modeling guidelines for an Underfill Encapsulation analysis. To model the cavity under the chip, assign the Part surface property to the cavity mesh elements. At present, flow outside the chip cannot be analyzed, because only the cavity under the chip is modeled. The thickness of the cavity under the chip is assumed to be uniform. The nodes where the dispensing occurs are modeled as the injection location. For accurate analysis, you must model each solder individually. To model the region away from the solders, use a shape factor of 1. To model the region near the solders, calculate a shape factor by using the following equation: shape factor = (actual area of solid wall in thickness or planar direction) / (area of solid wall used in the simulation) 7

12 Dynamic dispensing for Underfill Encapsulation 4 In order to take advantage of dynamic dispensing for underfill encapsulation, there are several requirements that need to be considered. Dynamic dispensing for underfill encapsulation is a feature that allows you to simulate the actual dispensing path more realistically. To use this feature, you need to determine your dispensing path, decide which is the start node and which is the end node, and assign injection locations along the entire path. A minimum of 4 injection locations are required, but ideally all nodes on the plane along the dispensing path should be set as injection locations. NOTE: The option to Perform dynamic analysis is available only for 3D models. 1 Make sure that the dispensing path is a single continuous path. The path can be multiple planes, as long as they are connected. However, a closed loop is not allowed. 2 Make sure that each plane of the dispensing path has straight edges. 3 Define at least 4 injection locations for each injection plane. Although it is not required, we recommend that every node on the plane along the dispensing path is set as an injection location. NOTE: Not all injection locations on a plane should be aligned along a straight line. 4 Decide which injection node at one end of the dispensing path will be the start node, and which injection node, at the other end of the dispensing path, will be the end node. 5 Decide how many dispensing passes you want. For each dispensing pass, the dispensing speed is constant. However, different passes can have different speeds. 6 The dispensing volume added over all passes should total at least 100% of the cavity volume to avoid short shot. NOTE: The total dispensing volume may be greater than 100% of the cavity volume. Dynamic dispensing for Underfill Encapsulation There are steps required to set up an underfill encapsulation analysis. 8 Dynamic dispensing for Underfill Encapsulation

13 Dynamic dispensing for Underfill Encapsulation set up NOTE: The option to Perform dynamic analysis is available only for 3D models. Make sure you have assigned nodes along your dispensing path as injection locations, and you know which one will be the start of the dispensing path and which one will be the end. It is recommended that all nodes on the injection plane along the dispensing path have been assigned as injection locations. NOTE: A minimum of 4 injection locations are required on each injection plane. To set up dynamic dispensing, first you will define the properties associated with the start and end nodes, and then you will assign the start and end nodes. 1 Click Boundary Conditions tab > Dispensing panel > Set Controller to open the Set Dispensing controller dialog. 2 Click Edit to open the Dispensing controller dialog. 3 In the Dispensing controller dialog, in the Start node or end node of the pass section, select Start node from the dropdown menu, and type a unique name for the start node properties in the Name box. 4 Click Edit data to open the Dispensing data dialog. 5 Decide how many dispensing passes you would like to perform and the volume of encapsulant you would like to dispense in each pass, and enter the information in the relevant boxes. Make sure that the start time of the first pass is 0, and that the start time of all subsequent passes is after the end time of the previous pass. Click OK to close the Dispensing data dialog, then click OK again to close the Dispensing controller dialog. 6 In the Set Dispensing controller dialog, if you haven't already created an end node property, click New to create one. 7 In the Start node or end node of the pass section, select End node from the dropdown menu, type a unique Name for the end node properties, and click OK. The start node properties, end node properties, and number of passes have now been defined. Now you need to assign these properties to your chosen start and end nodes: 8 In the Set Dispensing controller dialog, select the start node properties you defined, then click on your model to select the start node of your dispensing path (this node must already have been defined as an injection location). Dynamic dispensing for Underfill Encapsulation 9

14 A cross will appear on the selected node. The orientation of the cross is irrelevant, but confirm that the center of the cross is superimposed on your selected start node. 9 In the Set Dispensing controller dialog, select the end node properties you defined, then click on your model to select the end node of your dispensing path (this node must already have been defined as an injection location). A cross will appear on that node. The orientation of the cross is irrelevant, but confirm that the center of the cross is superimposed on your selected end node. 10 Close the Set Dispensing controller dialog by clicking on the close dialog cross in the top right hand corner. 11 Click Home tab > Molding Process Setup panel > Process Settings and activate dynamic dispensing by clicking on the Perform dynamic analysis checkbox, then click OK. 12 Once you have set all your other processing conditions, click Start Analysis in the Study Tasks pane, to start the simulation. 10 Dynamic dispensing for Underfill Encapsulation

15 Dispensing locations 5 The dispensing location is the point where the encapsulant is dispensed for the underfill encapsulation process. For an Underfill Encapsulation, ensure that the dispensing location is set along the entire line of one side of the flip chip. It is important that the correct amount of underfill material is dispensed. If too little material is dispensed, the part will not be completely underfilled or may have a fillet that induces stress on the edge of the die. The result is a package with lower reliability. If too much material is dispensed, the fillet will extend to unwanted areas on the board or over the top of the die. Reliability of the surrounding components and heat transfer can be adversely affected. NOTE: The dispensing location is similar to, and set in the same manner, as the injection location in thermoplastic injection molding. Dispensing locations The dispensing locations can be considered to be the same as an injection location. Setting up underfill dispensing locations For line dispensing in Underfill Encapsulation, you must specify the dispensing location at every node along the line. This is done the same way as setting an injection location for thermoplastic injection molding processes. 11

16 NOTE: If you would like to perform dynamic dispensing, where the encapsulant is dispensed over several passes, you will need to set the dispensing controller, under Boundary Conditions tab > Dispensing panel > Set Controller, and check Perform dynamic analysis in the Process Settings Wizard. Dispensing locations Use this dialog to specify settings for dispensing locations. Dispensing Location dialog This dialog is used to specify values for the dispensing location related inputs for a Underfill Encapsulation analysis. Underfill encapsulant Underfill conditions Solver parameters Click Edit to edit the properties of the default underfill encapsulant, or click Select to choose an alternate underfill encapsulant from the supplied database. Allows you to select and edit a pre-saved set of processing conditions for the Underfill Encapsulation process. Allows you to select and edit the solver parameters to be used during the analysis. Dispensing controller dialog Use this dialog to define the dispensing control nodes, start and end, for dynamic dispensing in Underfill Encapsulation. Assign properties to the start node and give it a unique name. Create another unique name for the end node. Start node or end node of the pass Dispensing controller - Name One injection location must be designated as the start node, and another the end node. The properties of the start node can be edited to allow multiple passes. This name relates to the start node or the end node. Each time you change the properties of these nodes, you should create a unique name and save it by clicking OK. 12 Dispensing locations

17 Dispensing data dialog In Underfill Encapsulation, you have the option to set multiple dispensing passes. In this dialog, you can set the number of passes, the length of time for each pass, and the volume to be dispensed in each pass. To enter data in the table, simply click on the relevant cell and enter the data. If you have entered a row of data and no longer want that row, highlight the row and hit the delete button on your keyboard to remove it. Dispensing volume per pass Start time / End time for each pass When choosing multiple dispensing passes in Underfill Encapsulation, you need to specify the volume of material you would like dispensed in each pass. You can choose an absolute volume or a %Part volume. When choosing multiple dispensing passes in Underfill Encapsulation, you need to specify the start and end time for each pass. Enter the start time and the end time for each pass, in seconds, in the the table. Dispensing locations 13

18 Shape factor calculation for underfill encapsulation 6 There are different shape factor methods that you can use for an Underfill Encapsulation analysis, depending on whether the region is modeled away from the solders or near the solders in the model. Using shape factors To model the region away from the solders, use a shape factor of 1. To model the region near the solders, you can calculate a shape factor by using the following equation: Shape factor = (actual area of solid wall in thickness or planar direction) / (area of solid wall used in the simulation) For example, consider the following case shown below, where one cell is taken around a solder from the array of solders to consider the surface area around that solder: 14 Shape factor calculation for underfill encapsulation

19 There are three areas related to this cell: A area around the solder in the upper region (not including the solder region). B area around the solder in the lower region (not including the solder region). C surface area of the solder. For this case, the shape factor is = (A + B + C) / (A+B) If the length of the cell (assuming square cell) is L and the diameter of the solder is D and the cavity thickness (which is the same as the solder height) is T, then: A = L2 πd 2 /4 B = L2 πd 2 /4 C = πdt Shape factor calculation for underfill encapsulation 15

20 Underfill encapsulant materials 7 Underfill encapsulant materials have certain properties. Underfill encapsulant material properties are almost the same as those of encapsulation molding compounds used for standard microchip encapsulation, with two differences: For underfill encapsulant rheological data, the Herschel-Bulkley-WLF model includes one additional term, h (thickness), as described in the Herschel-Bulkley-WLF viscosity model. Underfill encapsulants include an additional data category, surface tension, as described below. Surface tension data In underfill encapsulation, when the encapsulant is dispensed, the driving force is the capillary force at the melt front. In order to analyze this dispensing process, surface tension data is required to analyze the dispensing process. To model surface tension, the dynamic temperature-dependent surface tension model by Han is used, which can be represented as follows. The surface tension and the equilibrium contact angle can be described by the equations given in the Dynamic surface tension model. Underfill encapsulant materials All materials in the database have physical properties recorded, which you can view to decide on the appropriateness of the selected material for the analysis. Checking the properties of the underfill encapsulant The material used in an analysis impacts heavily on the results. A generic material is assigned to an analysis by default. 1 Click Home tab > Molding Process Setup panel > Select Material to open the Select Material dialog. 2 Click Details to open the Underfill encapsulant dialog. 3 Select each of the different tabs to view the relevant information contained in that section. 4 Click OK to close the dialog, and return to the Select Material dialog 16 Underfill encapsulant materials

21 Underfill encapsulant materials The underfill encapsulant dialog provides you with access to all the properties of the material you have selected. Underfill Encapsulant dialog - Description This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Description tab of this dialog provides general, descriptive information identifying the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill Encapsulant dialog - Recommended Processing This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Recommended Processing tab of this dialog is used to specify the recommended processing conditions for the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill Encapsulant dialog - Rheological Properties This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Rheological Properties tab of this dialog is used to specify the rheological (flow-related) properties of the underfill encapsulant material. Underfill encapsulant materials 17

22 To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill Encapsulant dialog - Thermal Properties This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Thermal Properties tab of this dialog is used to specify the thermal properties of the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. TIP: To determine whether you have selected an appropriate material for analysis, plot graphs of the materials specific heat and thermal conductivity with relation to its heating/cooling rates. Underfill Encapsulant dialog - Reaction Kinetics Properties This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Reaction Kinetics Properties tab of this dialog is used to specify the reaction kinetics (curing-related) properties of the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. 18 Underfill encapsulant materials

23 The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill Encapsulant dialog - Surface Tension Properties This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Surface Tension Properties tab of this dialog is used to specify the surface tension properties of the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill Encapsulant dialog - Filler Properties This dialog is used to view/edit the properties of the selected underfill encapsulant material. The Filler Properties tab of this dialog is used to specify the physical properties of any filler material(s) added to the underfill encapsulant material. To access this dialog to view the properties of the currently selected encapsulant, right-click the Material Selection task in the Study Tasks pane and select Details. To access this dialog to edit the properties of the currently selected material, double-click the Process Settings task in the Study Tasks pane, click Advanced options, then click the Edit button associated with the Underfill encapsulant option. The collection of property values defined on the dialog are saved to a property set with the description shown in the Name box. Underfill encapsulant materials 19