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Date: | Tue, 5 Nov 1996 15:19:21 -0500 |
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What I have failed to mention is the process must be UL
recognized. That means not only the raw material, in this
case soldermask, but the process used to apply must be UL
recognized. In addition UL must also recognize the use of
soldermask as a dielectric insulating material. If anyone
knows of conformance of soldermask to those requirements, let
me know.
______________________________ Reply Separator _________________________________
Subject: INSULATING LAYER
Author: [log in to unmask] at Internet
Date: 11/1/96 2:53 PM
We have an application on a 2 layer board with through hole
technology which requires an insulating material
laminated/applied to one surface/side. Initially we thought
of having a prepreg material laminated to one surface but are
unsure if this is the most cost effective method. Anyone out
there who knows of a method or material which would support
this requirement please respond.
Some of our requirements are;
>>>>>>Have you considered solder mask!!!!
1. Must be a UL recognized material
>>>>>>>>yes
2. Must provide at least 500V of dielectric insulation
>>>>>>>>>solder mask is typically 40V per micron, so to
provide 500V requires a minimum of 12.5um of resist, easily
achievable by double coating wet on dry.
3. Would preferably be thin, .001-.003 thick.
>>>>>>>>>see above
Some questions we have are;
1. What type of relief would be needed around PTH?
>>>>>>>>photoimageable = print tolerance 2. How thick would the material
nee
d to be?
>>>>>>>>see above 3. Who is doing this type of fabrication today?
>>>>>>>>everyone 4. Can it be applied selectively?
>>>>>>>>photoimage 5. What is the typical cost impact to a double sided
boar
d?
>>>>>>>>do you want % or in cents - or do you already have the
the answer and its on your board already?
Dougal Stewart
Exacta Circuits
Scotland
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