Forward it to Technet.
I am sorry that I am new to the Technet, I replied the e-mails to the personal mailbox. For those whom I sent e-mails to your personal mailbox, please accept my apology for that.
Chris.
christian ge <[log in to unmask]> 写道：
日期: Thu, 25 May 2006 10:00:19 +0800 (CST)
发件人: christian ge <[log in to unmask]>
主题: 回复： Re: [TN] Thermal cycle test for
plated through holes filled with epoxy ink and
cap plated on the top
收件人: [log in to unmask]
Dear all,
Thank you very much for your help!
Werner,
We asked the supplier to do 1000 thermal cycle tests at -40degree C to +145 degree C. Dwell time of each temperature is 30minutes. The supplier measured the resistance at 250 cycles, 500 cycles, 750 cycles and 1000 cycles and conducted the cross-section after 1000 cycles.
As to your questions : How do know " All have completed barrel crack except the holes of 10mils"? I know this from the supplier's cross-sections. They made cross-sections on all kinds of holes, and only 10mils holes didn't have complete barrel crack. Here the "complete barrel crack" I said means the crack length is equal to the plated copper thickness on the hole wall.
Thanks.
Chris.
[log in to unmask] 写道：
Nee how Chris,
What you describe is very unusual.
Normally, the smaller the hole diameter, the earlier the barrel crack. Reason: it is more difficult to plate good copper into smaller-diameter holes.
If you only measure at the beginning of the test and at the end at room temperature, the fracture surfaces will make good contact under compression, and it is like matting connector surfaces. The reason for this is that during the high temperature the barrel is stretched and somewhat plastically deformed. Then fatigue failure happens. On cooling the resin shrinks backk to its original volume, and the fractured halves of the stretched barrel are pressed together.
That is why one should always measure the daisy-chain resistance during testing; that way, you also know when the failures occurred.
How do you know " All have complet barrel crack except the holes of 10mils ."?
Regards,
Werner Engelmaier 材鹧拉黎栏
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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