Could anybody help explain the retionale behind the "exposed copper" specification? Why would any amount be rejectable for high-reliability applications? I can understand that for specific applications (e.g.: flex circuits that go inside an HDD), loose copper oxide can permanently damage the media surface. But for most other applications, such sensitivity does not exist.

-Luke Mendoza-
Electronic Assemblies Inc.

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Sent: 	Wednesday, July 24, 1996 1:44 AM
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Subject: 	Re: Exposed copper

Darrell

It seem that there is some confusion between SOLDER coverage and SOLDERMASK
coverage.  IPC-RB-276, the bare board spec, allows exposed copper (copper
that is not covered with solder) along the vertical edges and 1% of the other
conductor surface that is not covered with soldermask or meant to be
soldered.  The same specification, IPC-RB-276 Amend. 1, does not allow voids
...<snipped>...

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