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April 1999

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Subject:
From:
doug smith <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 30 Apr 1999 09:29:19 -0700
Content-Type:
text/plain
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text/plain (47 lines)
Dennis,
One explanation for differing appearances is using different stackups, either foil or cap construction. The first plane layer will be a different color based on whether or not the oxide treated layer is facing out (visible). If layer 2 is a plane, then a foil construction would have the oxide (dark color) visible. If using cap construction the oxide layer faces the board center. 

The board should still meet your requirements, as long as you spelled out your requirements on your fab drawing. If you just have a generic "xx layer" board without specifying dielectric thicknesses, you can get a wide variety of stackups. If you don't specify a stackup you leave the decision up to the vendor. If you don't specify, the assumption is it doesn't matter.

Regards,
Doug

>>> Carson Dennis D <[log in to unmask]@yusa.com> 04/30 8:06 AM >>>
We recently received product in which it was noted that the board coloration
was different than those we had received before. The distributor stated that
this was because they came from a different supplier (they use three
suppliers), but that the board was certified to FR-4 requirements. We
requested and received this material certification. The question(s) I have
are: What would cause a color change? Does this difference in coloration
affect the mechanical or electrical properties of the board? Where is
coloration covered by the IPC standards (if it is)? Any help would be
appreciated.
Dennis D. Carson
Cab and Controls Team
Phone:  309 - 748 - 2073
Fax:      309 - 765 - 2206
Internet Address:   [log in to unmask] 

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