Ken Patel asked:

>How often one should take solder sample from the wave solder pot for content
>analysis (impurities)? Is there a guideline which assembly house should
>follow?

Q1: Depends, see below.

Q2: Yes, J-STD-001B paragraph 5.3 "Solder Purity Maintenance". This
requires one to analyze either monthly or at a frequency "determined on the
basis of historical data" Also, the requirment to maintain records for
solder bath usage (time, area, amount of replacement solder) are mentioned
with the term "shall". This means it is required in all cases for class 3,
and where no "documented process control plan" exists for class 2.

In my experience, soldering a lot of boards, normal temps, and making
regular additions of bar solder; analyze every 3 months for a year (to
build historic records), then every 6 months. High copper is what you would
probably see first. Your bar solder supplier would probably give you a
discount on analyses if you asked. With gold and silver leadframes mostly
history, wavesolder pots stay in spec if replenished with quality solder.
YMMV.


regards,


Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com

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