Hi All,

I notice that a few new references have been made to the above subject and
thought I would share some of my early work with you.

In my first post as a graduate, I researched the causes of dewetting on
circuit boards. I came across a solution, the make-up of which I have since
lost, which dissolved the tin lead alloy but left the two intermetallic
layers.

I produced a number of one inch square coupons which I soldered using 63/37
alloy, RMA flux and a Tri Moore Rotary Dip Tester.

These were divided into three categories:

1       Control
2       Remove tin lead and re test in the Rotary Dip.
3       Remove tin lead, Several hours steam ageing and re test.

Microsections showed that I had taken off the alloy successfully and left
the IMC.s.

All of the re tested coupons soldered successfully, including the steam aged
ones.

This was some years ago so I cannot remember the etchant nor the hours and
conditions in the steam ageing equipment. I do remember that the IMC
soldered very well so I am always dubious when somebody blames the
intermetallic for poor soldering.

I seem to be alone in my faith that the IMC solders but this was the result
of my very own work and I stand by it.

Regards
Eric Dawson, Defender of the IMC.

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