SMT007 Magazine

SMT007-Nov2021

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NOVEMBER 2021 I SMT007 MAGAZINE 71 for so long really wasn't that big a deal. I rec- ommend reading the WP-019B and Chapter 8 of the J-STD-001, to confirm that it's not as bad as people may think. I will try to address the changes in layman's terms. You must have objective evidence that what you are doing is producing acceptable hardware. It gives you three options: 1. Surface insulation resistance (SIR) testing, testing of cleaning test boards and sometimes called test vehicles, IAW IPC-9202 and IPC-9203. SIR testing uses a grid in hard to clean areas to test for damaging contaminants building up over time with increased temperature and humidity. Ion chromatography (IC) testing could be used to assist in identify- ing possible contaminants le behind. 2. "If it ain't broke don't fix it." What you are doing has been documented as safe and effective for your service environment on delivered hardware over time (See J-STD-001 - Appendix C). 3. Custom testing that simulates the service environment. Troubleshoot any failures to determine if residues caused the failure. • Rework processes (solder, flux, heat) need to be included • Once you do this you don't need to requalify until you change something called out in 8.3 • Determine your UCL (the WP-019 is helpful); document your process • What to do if you exceed your UCL? • What if you change something? ose are covered well in 8.2.3 and 8.3. e best advice I can give is to read WP-019B, be- cause it gives examples to help determine what works for you. Some of the other major changes to revision H were: • Clarification on the word lead as an attachment and lead (Pb) the element that may be found in solder. e homograph (words that are spelled the same but having different meanings) could be confusing for other translations of the J-STD-001. It was proposed that the term lead (a part attachment) would remain unchanged, and lead (the element) would be lead (Pb) or Pb-free as needed. is has now become a common change in multiple IPC documents as they are updated. • Clarification of voiding from the process not being followed, compared to normal voids that naturally occur. is was very helpful because there was some confusion on the subject, so Appendix D was incor- porated to clarify this issue. Team Skele- ton, led by the outgoing chairs, Dan Foster and Kathy Johnston, worked this task. • Addition of new SMT parts. Inductors wrapped around terminal posts (quad package). SMT electrolytic capacitor (AKA V-Chip) or sometimes a crystal called Vertical Cylindrical Cans with outward L-shaped leads. Flat unformed leads (not powered) criteria for ribbon cables. Center terminations on SMT chip components. • Modification to flat and round gull wing leads for toe overhang and heel fillet requirements. Data was presented by Udo Welzel (co-chairperson of the Auto Addendum) for a proposal to change the heel fillet requirement to one-half the lead thickness for Product Class 3. e concern here was the leads were relatively thick and additional solder needed to meet the requirement could result in a weakened solder joint as shown in thermal cycle test- ing. Also, the contact area of the lead on the land and toe overhang were tweaked to help address some issues. • You may notice that the International Space Station symbol is gone. It was only

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