Attaboy, Werner!
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, January 16, 2006 7:41 PM
To: [log in to unmask]
Subject: Re: [TN] Drill and plated hole callouts
Hi Bob,
The call out of finished hole size is an anachronism left over from the
through-hole technology era. In modern high-density PCBs you should
specify the drilled hole size (no tolerance) with a minimum plating
thickness in the hole to be verified by cross-sectiong of coupons.
The reliability of your vias depends on PCB thickness, drilled hole
size, Cu plating thickness, Cu plating quality (verified by testing
co-plated mandrel foils for tensile strength and ductiolity--not
elongation). Your friend is right, electrical test is not enough. You
should have coupons either IST or HATS-tested. This will be even more
important with LF-soldering temperatures. You then might want to specify
not only Tg, but Td and CTE(z) as well.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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