A colleague, Rick Day, has provided the following response to the Vacrel
8140 lamination question:


      We see this "laking" phenomenon when the laminator temperature
 is too high.  The color differences are due to thickness differences.
 I'd check the temperature uniformity - if there are hot spots, that will
 be the worst area.  I would also lower the temperature and see how that
 affects this defect.  Vacrel 8100 is fairly soft and can be laminated at
 relatively low temperatures (compared to some other dry films).  The
 dwell time may need to be lengthened to compensate for lower temperature.


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 Hello Technet,
 We have been experiencing problems with our soldermask lamination process.  We
 use Dupont's Vacrel 8140 dry film soldermask, and apply with an EH2400 vacuum
 laminator.  Upon removal from the laminator, we frequently see that rings have
 formed in the soldermask.  The rim of the ring is darker green, and the area
 confined by the ring is lighter green than the surrounding soldermask.  We
 have requested help/suggestions from mfg of both laminator and film, but as
 often happens, each says the problem is not with their product.
 Has anyone else experienced this problem while vacuum laminating dry film
 soldermask?  Any suggestions on how to eliminate this problem would be greatly
 appreciated.
 cbh
ÿÿ

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