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Mechanical Testing of Blind Vias

IP.com Disclosure Number: IPCOM000042992D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Darekar, VS: AUTHOR [+2]

Abstract

A test to measure the force that is necessary to separate blind vias from circuit board interplans is accurately performed in the following four-step procedures: Step One: Cut a small area around the via 1 to be tested (including its pad P In the interplane) and remove from board. Cut all circuit lines near the via, and immerse the via 1 in concentrated sulfuric acid at 185ŒF. After 30 minutes remove and separate all glass cloth from the via. Step Two: Insert pin 2 in a mount (not shown) and apply adhesive 3 to the head of the pin. Place the via in an upright position on the adhesive, and let it set for 30 minutes. Next, place a drop of oil 4 on the upper surface 7 of via pad P. Step Three: Place nut 5 on a glass slide (not shown) and fill the nut with molding compound 6.

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Mechanical Testing of Blind Vias

A test to measure the force that is necessary to separate blind vias from circuit board interplans is accurately performed in the following four-step procedures: Step One: Cut a small area around the via 1 to be tested (including its pad P In the interplane) and remove from board. Cut all circuit lines near the via, and immerse the via 1 in concentrated sulfuric acid at 185OEF. After 30 minutes remove and separate all glass cloth from the via. Step Two: Insert pin 2 in a mount (not shown) and apply adhesive 3 to the head of the pin. Place the via in an upright position on the adhesive, and let it set for 30 minutes. Next, place a drop of oil 4 on the upper surface 7 of via pad P. Step Three: Place nut 5 on a glass slide (not shown) and fill the nut with molding compound 6. Invert the pin/via assembly and lower in molding compound until the oiled pad surface 7 touches the compound 6. Let it set for a few hours. Oil 4 prevents pad P from becoming affixed to compound 6. Step Four: Attach the nut and pin to a known pull tester (not shown). Using a one-pound load cell and .02"/min. crosshead speed, pull until the via separates. Record the loading, measure the contact area, and calculate the via bond strength. The key features of this process are the isolation of the via to eliminate surrounding material interference, room temperature cementing to avoid damaging heat effects, and the molding technique to avoid breaking of via walls duri...