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Subject:	Re: Thermal cycle test for plated through holes filled with epoxy ink and cap plated on the top
From:	Werner Engelmaier <[log in to unmask]>
Reply To:	TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:	Tue, 23 May 2006 08:38:04 EDT
Content-Type:	text/plain
Parts/Attachments:	text/plain (37 lines)

 (JI am resending this, because when I opened what I got from Technet it was  (B
 (Jpretty garbled. (B

 (JNee how Chris, (B
 (JWhat you describe is very unusual. (B
 (JNormally, the smaller the hole diameter, the earlier the barrel crack.  (B
 (JReason: it is more difficult to plate good copper into smaller-diameter holes. (B
 (JIf you only measure at the beginning of the test and at the end at room  (B
 (Jtemperature, the fracture surfaces will make good contact under compression, and it  (B
 (Jis like matting connector surfaces. The reason for this is that during the  (B
 (Jhigh temperature the barrel is stretched and somewhat plastically deformed. Then  (B
 (Jfatigue failure happens. On cooling the resin shrinks backk to its original  (B
 (Jvolume, and the fractured halves of the stretched barrel are pressed together. (B
 (JThat is why one should always measure the daisy-chain resistance during  (B
 (Jtesting; that way, you also know when the failures occurred. (B
 (JHow do you know " All have complet barrel crack except the holes of 10mils  (B
 (J."? (B

 (JRegards, (B
 (JWerner Engelmaier  $B2DpQ@-@h@8 (B
 (JEngelmaier Associates, L.C. (B
 (JElectronic Packaging, Interconnection and Reliability Consulting (B
 (J7 Jasmine Run (B
 (JOrmond Beach, FL 32174 USA (B
 (JPhone: 386-437-8747, Cell: 386-316-5904 (B
 (JE-mail: [log in to unmask], Website: www.engelmaier.com (B

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