General Process Specification for Reflow Soldering of Boardmount 3M Pak Connectors, 3M CF Card Headers and 3M PCMCIA Sockets and Headers

Transcription

1 General Process Specification for Reflow Soldering of Boardmount 3M Pak Connectors, 3M CF Card Headers and 3M PCMCIA Sockets and Headers Technical Report November A

2 Table of Contents Introduction Reference Materials Connector Requirements Connector Materials SMT and Wave Solder Processing Solder Processing Guidelines A

3 Introduction This document covers the recommended specifications for the successful solder processing of 3M connectors. Wave solder and/or reflow soldering processes are recommended. Reference Materials Drawings - All 3M Connectors are detailed in their respective technical specification (TS) drawings. Qualification Test Results Available for every 3M product series as a PDF document either on the 3M Interconnect website ( or through a 3M applications engineer. Commercial Specifications IPC Specification MS-810 provides solder joint acceptance standards as set forth by the Institute for Interconnecting and Packaging Electronic Circuits. RoHS Demands 3M is engaged in a program with the intent of having all of our connector and cable products meet the demands of RoHS and WEEE before the required implementation date. Check the 3M Interconnects website under Regulatory Issues ( for specific product release dates by product series. Product releases for RoHS will include a product ID change to ensure a distinctive part number and to ensure that stocks of leaded product are not employed. The distinctive product ID change will be in the suffix for the plating callout as it calls out a RoHS equivalent, solderable plating of tin. See specific TS Drawing or the Regulatory Issues section of the 3M Interconnects website. Connector Requirements Connector Design Standoffs Standoffs are employed to help ensure proper connector spacing from the printed circuit board surface the Z height. They are also placed so as not to interfere with the placement of solder paste or its molten flow front during reflow soldering. For information on recommended connector part numbers for wave or reflow processing, contact your 3M sales rep or application engineer. Alignment Post Recommendations In most applications, the use of location posts is not recommended as the connector will self-align to the printed circuit board pads during the soldering process. In applications where the connector is subjected to mechanical forces that could jeopardize solder joint integrity, a location post to absorb those forces should be included in the connector ordering sequence. Mechanical Hold Downs In applications where there are considerable mechanical forces applied to an interconnect during use, 3M recommends using mechanical hold downs, usually consisting of mechanical press fit contacts or screw, washer and nut hardware. These mechanical forces may include, but are not limited to, mating connector/ cable insertion and withdrawal forces, mating printed circuit board forces generated as a result of shock or assembly mismatch forces and mechanical forces associated with card insertion and withdrawal. Where required 3M provides for a means to fasten the connector down to the printed circuit board. This fastening should occur, where practical, prior to the solder process to eliminate solder joint stresses. Environmental Specification on the TS Drawing 3M attempts to state in all TS Drawings both the continuous use Temperature Rating and the Process Rating temperature for all 3M Boardmount Connectors. As 3M rapidly responds to RoHS demands, the Process Rating temperatures for any given connector may be revised. It is important that you reference to the latest TS Drawing on the 3M Interconnects website for the latest revisions. Connector Materials Molding Materials In general, all 3M Boardmount Connectors have options for body moldings, which will withstand wave solder and/or reflow soldering processes. If a connector has the ability for both low temperature (wave solderable only) and high temperature (reflow and wave soldering) options, these options will be signified by the use of an N prefix in a part number sequence. In cases where an N prefix is not available, the connector is only available as a high temp option with one exception. Where a molding material of Glass Filled Nylon is called out, see the specific TS Drawing these connectors are for wave solder applications only. Molding materials are generally non-hygroscopic and need no preconditioning to remove moisture prior to soldering with the exception of connectors molded of Glass Filled Nylon. As stated above, utilization of RoHS compliant ( no lead ) solders will require connector insulators to withstand higher processing temperatures in both wave and reflow soldering processes. RoHS compliant boardmount connectors intended for reflow processing will utilize insulators evaluated under the conditions specified by J-STD-022C for both heat A 3

4 resistance and moisture sensitivity levels. While no industry standard exists yet for wave solder connector evaluation using no lead solders, results from initial evaluations using common no lead soldering conditions (260ºC wave, 1.5 m/min. line speed) indicate that wave soldered connectors will require high temperature insulators. Stamping/Platings Depending on the application, all connectors are manufactured with an appropriate copper based alloy. Beryllium Copper, Phosphor Bronze and brass alloys are utilized depending on the application. Contacts are always underplated with a barrier layer of nickel. Gold and/or palladium nickel are commonly used on the mating interface. Presently, tin/lead is utilized on the wetable solder tail at either a 90/10 or 60/40 ratio depending on the application. Future revisions are being planned to meet the demands of RoHS and WEEE. Solderable interfaces on RoHS compliant connectors will generally utilize a nickel underplate and a low-stress, low-organic, matte finish pure tin plating. Preliminary testing shows that this contact finish is backward compatible with eutectic tin-lead solders. Connector Storage Requirements Connectors should be stored in a climate controlled area to prevent moisture build-up on the exterior surfaces. With this precaution, there should be no need for preconditioning. Even with a nickel barrier layer, non-solderable intermetallics form in tin or tin-lead solder tail platings over time. Shelf life is limited by this phenomena. Hot and/or humid conditions have been shown to accelerate the degradation of the solderability of the solder tails. Good inventory management procedures (first-in/first-out) should be used. If old stock is identified, the solderability of the solder tails should be checked using an appropriate method from J-STD-002. Preliminary testing indicates that RoHS compliant tin plated solder tails may be more sensitive to degradation than were the tin-lead plated parts. Packaging - Connectors are shipped in various forms of packaging, tray, tubes or tape and reel designed to prevent damage to leads and connector bodies. We recommend the use of tape and reel packaging, EIA 481 style packaging, for most 3M Connectors. Connectors should be maintained in these original packages until time of use. SMT and Reflow Solder Processing Printed Circuit Board Requirements Printed Circuit Board Layout For specific connector printed circuit board layout, see the appropriate TS Drawing. Refer to the 3M Interconnects website or call your 3M sales representative. Printed Circuit Board The variability of the printed circuit board pad layout must be limited to a coplanarity of.05 mm (.002 ) max. This variability takes into account printed circuit board bow/warp, cover coat plating and other manufacturing anomalies. The use of board stiffeners or design specific racks is highly recommended especially on board designs which have large surface area connectors soldered to them incorporating close spaced contacts, i.e. <1 mm. Solder Resist - A solder mask is recommended to minimize solder bridging and the height should not exceed the pad height by.05 mm (.002 ). Some specific connectors specify keep out areas for the solder mask see specific TS Drawing. This area is delineated to ensure that the mask does not interfere with the coplanarity of the installed connector system of printed circuit board/solder paste deposition/connector coplanarity variation. Solder Paste / Flux Leaded Designs - A 60/40 tin lead composition paste is recommended with a solids content of 85% minimum. RMA flux is recommended RoHS Compliant or Pb Free Designs As of this writing, the industry is leaning toward a SAC alloy consisting of Sn, Ag 3%, Cu.05%. NEMI has recommended the use of Sn, 3.9% Ag, 0.6% Cu for reflow soldering applications. Solids and flux recommendations are still being finalized. Solder Volume Solder paste volume is dependent on pad layout and paste deposition thickness. As pad layout is defined in the TS Drawing, the remaining variable is thickness. A deposition thickness of.15 mm (.006 ) is generally recommended. Some 3M Connectors, especially those with large pin counts and/or those connectors with a large surface area on the board will require thickness depositions of.2 mm (.008 ). A deposition of.13 mm (.005 ) will, in many cases, cause opens or insufficients due to limited solder volume and therefore is not recommended A

5 Solder Processing Guidelines Connector Placement Recommendations To minimize disruption of solder paste and to ensure proper vertical placement of connector into the printed circuit board and/or solder paste, an automated placement technique is highly recommended. Placement accuracy should be within guidelines set forth in J-STD-001. Solder Process Heat Profile Recommendations - The following is the maximum recommended soldering profile for time and temperature taken at or near the connector solder lead. This profile is for the higher temperature demands of RoHS solder processing, typically the SAC 305 type of Sn, Ag 3%, Cu.05%. The profile in Figure 1 is not meant to define an overall solder temperature profile for any complete printed circuit board, but only as a guide for maximum temperature exposure for the connector being soldered. As there are many variables within the solder process that are outside of 3M s control, it is recommended that a trial run be conducted to ensure proper solder conditions are met for the application and the specific populated printed circuit board to be soldered. Figure 1 Flux Removal/Cleaning It is recommended that all residue of the solder process be removed. Consult with the solder paste manufacturer for recommended aqueous cleaning and other solvents. 3M connectors will generally withstand all recommended solvents if time and temperature are limited. The usual time and temperature is a max of 100 Celsius and a max of five minutes. Solder Joint Quality A recommendation of solder joint quality is not provided herein as this area has been exhaustively studied by many different groups and trade organizations, notably IPC. Additionally the Pb Free solders being investigated will require a complete revision of the acceptance standards for solder joint quality A 5

6 3M is a trademark of 3M. Important Notice All statements, technical information, and recommendations related to 3M s products are based on information believed to be reliable, but the accuracy or completeness is not guaranteed. Before using this product, you must evaluate it and determine if it is suitable for your intended application. You assume all risks and liability associated with such use. Any statements related to the product which are not contained in 3M s current publications, or any contrary statements contained on your purchase order shall have no force or effect unless expressly agreed upon, in writing, by an authorized officer of 3M. Warranty; Limited Remedy; Limited Liability. This product will be free from defects in material and manufacture for a period of one (1) year from the time of purchase. 3M MAKES NO OTHER WARRANTIES INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. If this product is defective within the warranty period stated above, your exclusive remedy shall be, at 3M s option, to replace or repair the 3M product or refund the purchase price of the 3M product. Except where prohibited by law, 3M will not be liable for any indirect, special, incidental or consequential loss or damage arising from this 3M product, regardless of the legal theory asserted. 3 Electronic Solutions Division 6801 River Place Blvd. Austin, TX / Recycled paper 40% Pre-consumer waste paper 10% Post-consumer waste paper Litho in USA 3M A