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Blind VIA Quality Test

IP.com Disclosure Number: IPCOM000045196D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Strope, DH: AUTHOR [+2]

Abstract

Evaluation of the quality of a printed circuit manufacturing process as related to blind vias is a critical requirement. Information can be obtained by the sectioning of individual holes. This, however, is a slow procedure and does not yield any information as to the mechanical integrity of the contact. Additional information can be obtained by electrically testing the via contact. This testing, when combined with thermal cycling, can supply very useful information, but leaves many questions unanswered. The technique described below makes possible a more complete evaluation of the manufacturing process.

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Blind VIA Quality Test

Evaluation of the quality of a printed circuit manufacturing process as related to blind vias is a critical requirement. Information can be obtained by the sectioning of individual holes. This, however, is a slow procedure and does not yield any information as to the mechanical integrity of the contact. Additional information can be obtained by electrically testing the via contact. This testing, when combined with thermal cycling, can supply very useful information, but leaves many questions unanswered. The technique described below makes possible a more complete evaluation of the manufacturing process.

The tests are performed on test coupons located on each circuit line subassembly. The test procedure requires that the pull temperature after soldering be such that the first few mils of epoxy glass below the top copper be above its glass transition level, but that the epoxy glass surrounding the bottom copper be solid. Under these conditions the pull force registered on an Instron tester will provide a measure of the mechanical integrity of the plated contact. The entire coupon made up of some 60 individual vias is separated at the same time. Once the top copper has been separated from the bottom copper, both optical and chemical analysis can be performed on the contact interfaces.

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