Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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via masking

cc

#18435

via masking | 13 December, 2001

Does anybody know what is the nominal thickness for via masking and is there a set max.? I recently have some bridging on some fine pitch components and my suspicion is that the new fab with new via masking is the culprit. Thanks CC

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#18439

via masking | 13 December, 2001

There is neither �nominal thickness� nor �is there a set maximum� for via masking. We use some of our vias as test pads. So, as you�d expect, we get rabid when we get mask bleed onto these pads.

IPC-6012 - Qualification & Performance For Rigid Printed Boards * 3.8.3 Solder Resist Thickness states words to the effect of: � solder resist thickness is not measured unless specified in the procurement documents. * 3.8.1 Solder Resist Coverage talks to things like: - Metal conductors shall not be exposed in areas where solder resist is required. - Solder resist variations shall not expose adjacent conductors. - Conductors under components shall not be exposed. - Misregistration of solder resist defined features shall not expose adjacent isolated features. - Discussion of allowable solder mask on solderable pads. - Acceptability of pits and voids in solder mask in nonconductor areas. - Requirements for coverage of closely spaced surface mount lands. - Acceptability of chipping and lifting of solder mask along the board edge after fabrication.

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cc

#18494

via masking | 20 December, 2001

Thanks Cc

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