Hong Yuen Electronics Ltd. wrote:-
>We used Morton Epic 200A & B Wet Film Solder Mask for a long time, from Mid
>of November, 97. , we found that there were some residual on board after
>Developing, all our Process and Equipments are
>normal,

This sounds like a problem with your drying cycle being too hot. If the
temperature gets too high you will get partial polymerisation at the
board surface and the resist will not develop off. If you are seeing
this problem on one side only and are coating both sides before
exposure, then it will be happening on the first side as this sees the
drying cycle twice. If you can't solve the problem quickly, then you
could consider exposing and developing the first side before coating the
second side although this takes more time.

Good Luck
Paul Gould
Teknacron Circuits Ltd
Isle of Wight,UK

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