Werner,

I heard stories in my last Company about barrels in holes for PTH
components being "too small" or " too deformed' to permit components to be
fitted. Turned out to be a combination of finished hole diameter not having
sufficient component lead/solder clearance and barrel-crushing through
board expansion/contraction. Maybe wrong choice of PCB materials as well, I
don't know. It was remarked, however, that the effects would have been
greatly mitigated if n.f. pads had been retained.

Peter



Werner Engelmaier <[log in to unmask]>    27/03/2003 10:46 PM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Engelmaier

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: Re: [TN] non functional pad removal








Hi Bill,
Removing non-functional lands leads to a higher propensity for resin
recession and inner-layer separation [post separation] for larger diameter
holes. Whether or not this will cause any real problems depends on the
details.
The barrel integrity is not significantly affected.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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