No it's no coincidence.
Soldering is a nasty process. High flux activity means low soldering
defects. The flux is doing a job, breaking up barriers which would prevent
wetting. The more aggressive tyhe flux the better it will break up the
oxides on the surfaces. The issue is what are the implications for the long
term life of the assembly. Many assembly locations don't even consider this,
the DPMO is the bottom line. (Probably aren't monitoring that anyway).
Anyway, life is a balance. These figures fall nicely in the range where you
will have good soldering but still be reasonable for long term reliability.
Who is your customer, what is the application? Do we really need XE+10?
Regards
Ed Brunker
Principal Process Engineer
Sendo

-----Original Message-----
From: Amanda.Mountain [mailto:[log in to unmask]]
Sent: Thursday, August 24, 2000 2:41 PM
To: [log in to unmask]
Subject: [TN] SIR Interpretation


Hi all.  I'm hoping to pull on the experience on this list...

Performing a flux evaluation, we performed SIR tests with 8 different
conditions (4 fluxes, 2 temperatures).  The IPC coupons were processed
through our wave soldering/spray fluxing process, doing our best to simulate
regular production.  The fluxes we are evaluating are all VOC free/no
clean/water soluble/low solids/low residue fluxes.

The test was performed to Bellcore standards.

The SIR results we received were lower than expected - ranging from 2.74E+9
to 4.27E+10.   The pass value assigned by the laboratory is 3.2E+10.  Only 3
of 32 samples actually passed this standard.  6 of the 32 samples passed the
Bellcore minimum value (2.0E+10).  What sort of implications can we expect
with selecting a flux with slightly lower SIR results than the minimum
value?  Each of the flux vendors provided their own passing SIR test
results.

One other thing that was noted was that the boards with the fewest defects
came back with the poorest SIR results, and vice versa.  Is this just a
coincidence, or is there a solid explanation for this?

Thanks in advance,

Amanda Mountain

Amanda Mountain
Process Engineering
Leitch Technology International Inc.
Phone: (416) 445-9640 ext. 3852
Fax:  (416) 445-7927
http://www.leitch.com/

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