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Improved Gel Test for Epoxy Prepregs

IP.com Disclosure Number: IPCOM000039488D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Appleby-Hougham, G: AUTHOR [+3]

Abstract

A technique for measuring the gel time of resin powder flaked off of an epoxy prepreg which is used as an adhesive in the manufacture of multilayer printed circuit boards is disclosed. The technique comprises: alternatingly compressing the resin sample with a probe and permitting the sample to expand as the probe is retracted, accurately measuring the probe movement, timing the procedure, and defining a gel time as the point in time where the thickness of the sample ceases to increase when an attempt is made to retract the probe. The technique permits an accurate, reproducible, objective gel test. An apparatus for performing a gel test for resin powder flaked off of an epoxy prepreg or gained from a liquid epoxy varnish is seen in Fig. 1. The technique for performing a gel test is also understood with reference to Fig. 1.

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Improved Gel Test for Epoxy Prepregs

A technique for measuring the gel time of resin powder flaked off of an epoxy prepreg which is used as an adhesive in the manufacture of multilayer printed circuit boards is disclosed. The technique comprises: alternatingly compressing the resin sample with a probe and permitting the sample to expand as the probe is retracted, accurately measuring the probe movement, timing the procedure, and defining a gel time as the point in time where the thickness of the sample ceases to increase when an attempt is made to retract the probe. The technique permits an accurate, reproducible, objective gel test. An apparatus for performing a gel test for resin powder flaked off of an epoxy prepreg or gained from a liquid epoxy varnish is seen in Fig. 1. The technique for performing a gel test is also understood with reference to Fig. 1. In an oven 10 equilibrated to approximately 300 degrees F, a resin powder sample 15 is placed on a disposable bottom disc 20 made of aluminum, or the like. The disc 20 is clamped by clamps 25 to the oven 10. A probe 40, having a disposable disc 45 attached to one end via a bayonet shutter 50, or the like, and a spring 60 extending from the other end, is located directly above the sample 15. The probe extends out of the oven 10, and the spring 60 which is arranged to have a spring constant which is less than or equal to the adhesive force between the disc 45 and the sample 15 at the gel point of the sample, is attached to a rod or piston 65 via an adjustment clamp 70. The rod 65 is limited in its movement by a bar 75 such that it is free to move only in a direction perpendicular to its length. The rod 65 is supported by an asymmetrical wheel 80 which forces the rod, and hence the probe 40, upwards at certain intervals of the rotation of the wheel. At other intervals, the rod 65, and hence the probe 40, will move downwards due to the force of gravity. Probe 40 is also arranged with an electronic displacement monitor 85 which is used to accurately mon...