Re: TO-220 Failures due to lead bending?


"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:qele82hsf7obkhgjstb0r037vbgqi5tau9@xxxxxxxxxx
On Wed, 7 Jun 2006 17:35:03 -0500, "Brian"

Having seen a lot of data on the subject, we run no clean. Treated right, it
has a lot less effect on the circuitry than a wash process that is not kept
really clean. Any cheating at all with a wash process, and the results are
quite bad and the boards WILL fail.

With no clean, you just must use compatible processes all through production
for it to perform well. Don't do touch up with water soluable and expect to
even spot wash it. If you conformal coat, you must use a water based one.
Basically, you just have to respect what it is, controlled, encapsulated
residue. Most people that have issues with it muck it up themselves by
treating it incorrectly.

If you want to do water wash, you simply MUST monitor the process
consistently and keep it clean. Isolate the stages' water from each other.
Final rinse MUST be DI water, and I really mean must. Deleting this step
kills ya. Set the washer PSI and flow rate too low, you have issues. To
high, issues. Its a tighter process than one would think.

We have found the synthetic fluxes to work best for us in a no clean
process. We just have not seen any issues with it at all. A perfect wash
system would produce a board with less contaminants, yes, but I rarely saw
this "ideal" anywhere, making, to me, no clean the more practical and
reliable process for the majority of products.



.

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