HI
The pot capacity in most selective soldering machine is small enough that it
would probably be simpler to just change the contents periodically. The old
material would have value to offset the cost [although to reduce charges you
might want to batch them up to get a good net price].
If you go the analysis route you I suggest you plot analysis (impurity
levels) against usage/throughput. The number of boards processed in time
against the growth in impurities will help predict change over and - on
larger machines anyway - give information for SPC. You could relate joint
quality to pot content anyway.
You may find impurity growth is slow enough that you only need every other
sample analyzed (retaining the inbetweenies till next analysis so as to be
able to backtrack unexpected changes). Or you might find the levels steady
state at an uncritical level so you never change. 
XRF is not sensitive enough to accurately measure all impurities at the
levels they become important. 
Solder suppliers do supply analytical services but will relate the costs to
the value of your business.

Regards


Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Wednesday, September 07, 2011 12:11 AM
To: [log in to unmask]
Subject: [TN] Solder bath purity testing questions

I just installed a small selective solder rework system and now have to
start testing the solder bath for purity.

Who do you use for testing your solder bath for purity?  I cannot seem
to find the old standby sources I had used in the past.

Do I have to keep the solder purity analysis going back to the same
company that I buy the bars from (alp___ to alp___, kes___ to kes___,
etc) or has this service been farmed out permanently to independent
labs?  I am not able to find it quickly on the internet.

I thought about trying to use an XRF machine to perform my analysis
myself but I am a little skeptical about its' precision.  

Lastly, I find that the words in J-STD-001 seem a bit excessive for my
situation:

	"Records containing the results of all analyses and solder bath
usage (e.g., total time in use, amount of replacement solder, or
area throughput) shall be maintained for a minimum of one year for each
process/system."

Do I really need to record the time that we have the solder molten?  I
can understand recording volume of solder introduced, but this is a
rework pot and the usage and throughput would be minimal.

Any help is appreciated.

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