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Reply To: | TechNet E-Mail Forum. |
Date: | Wed, 15 Jul 1998 08:07:11 EDT |
Content-Type: | text/plain |
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Hi K.K.,
While your idea to "specify in my PCB drawing such that a fab. house always
orientates my PCB in a particular axis...as a means to match with the CTE of
certain components on that PCB", is a good one theoretically, in practical
terms it is not very practical. The CTEs between X-axis and Y-axis vary
typically by 2 to 3 ppm/C, but the CTEs for these directions themselves have a
varibility of about +/-2 ppm/C. If you are that desperate to tailor the PCB
CTE to the coponent CTE, you will have to measure and select from a population
of PCBs.
But I can not believe to achieve adequate reliability requires such drastic
measures.
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]
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