Fellow TechNeters,

We manufacture hardware for DOD per ANSI J-STD-001 and I have a couple of
questions regarding solder pots for removing gold from components prior to
tinning and soldering.

We send out solder samples for testing from our tinning and gold stripping
solder pots every thirty days.  To answer the question of "what do you do
with parts that were tinned while the solder pot is being tested (and the
test fails)" we shut the pot down until the test results come back.  The
problem is we only have one gold pot and don't want to shut it down during
testing.  How does your companies address this issue?  Is it fair to assume
that since there is a secondary tinning operation that the small amount of
gold that may remain on the parts will not be a problem?  Do you dump the
pot every thirty days?

The answer to this one is based on the criteria you are basing your solder analysis on.
If you have a limit of x amount of gold in your solder sample and you can show that after thirty days you accumulate y
amount of gold in your solder pot then the decision is based on what 'safe' limit you decide to set.
eg
limit = 100
30 days gives a reading of 20

then it follows
1) if your production is 'steady' then no way will your pot rise to 100 in less than say 60 more days
and any production going through during this period is 'safe'
2)think about changing the frequency of solder analysis to more accurately reflect your throughput (you
 should always receive test results giving you the ok if you tighten up on this)

My second question is, what is the maximum amount of gold that can be plated
on a terminal and still be soldered into an assembly with only tinning and
not cleaning?  Is there a specification that allows this?

we work to an internal spec that allows up to 1.3%  gold in
a solder joint (excess of this and ductility will be impaired and the
joint will become brittle). Other opinions state as low as 0.4% (by volume)
of gold in a joint

Thanks in advance for all responses.

Hope this advances your search

Ken Bloomquist
Sr. Principal Process Eng.
PRIMEX Aerospace Company
[log in to unmask]
(425) 881-8990 ext. 6645

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Regards
Ian Squires
Senior Production Engineer
-------------------------------------------------------

Graseby Dynamics Ltd
Park Avenue, Bushey, Watford, Herts, WD2 2BW
Web Site: www.gradyn.co.uk
Phone:    01923-228566 xt 295
Fax:      01923-221361
E-mail:   [log in to unmask]

Registered in England no. 480992
Registered office:
765 Finchley Road, London, NW11 8DS
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