Anthony,
Is it possible that these "spots" are pressure points where some roughness
on the prepreg has disturbed the oxide surface. If so the solution is to
delay application of full pressure until the resin softens at about 70
degrees celsius. It also helps to increase the pressure slowly taking maybe
10 minutes over it. This is the same mechanism that produces "shiners" on
pressed panels and the solution is the same. Were there any shiners on the
panels before etching ?
Regards, Dave Heywood
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To: [log in to unmask]; Dave Heywood
Subject:      [TN] copper spots after lamination