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Shear Force Testers On Chips Glued On PCB

IP.com Disclosure Number: IPCOM000100043D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 117K

Publishing Venue

IBM

Related People

Halliday, DK: AUTHOR

Abstract

This article describes methods and equipment devised to measure and test the adhesive strength of bonding materials used to fix microchips to cards. Chips have become detached from printed circuit boards because no method existed for checking bond strength; chemical analysis was too slow and costly. Rapid testers are required to operate under high volume manufacturing conditions and to be adjustable for both viscous and cured states of adhesives of different types. Also, the size of the chip and the quantity of adhesive specified must be taken into account. The basic shear-force test employed in this disclosure is to apply a force to the edge of a chip glued to a fixed- base card and observe strain on the strain gauge or the effect on a pre-set slipping clutch.

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Shear Force Testers On Chips Glued On PCB

       This article describes methods and equipment devised to
measure and test the adhesive strength of bonding materials used to
fix microchips to cards.  Chips have become detached from printed
circuit boards because no method existed for checking bond strength;
chemical analysis was too slow and costly.  Rapid testers are
required to operate under high volume manufacturing conditions and to
be adjustable for both viscous and cured states of adhesives of
different types.  Also, the size of the chip and the quantity of
adhesive specified must be taken into account.  The basic shear-force
test employed in this disclosure is to apply  a force to the edge of
a chip glued to a fixed- base card and observe strain on the strain
gauge or the effect on a pre-set slipping clutch.  Rotary torque is
also applied to the periphery of the chip to test for "twisting off"
by means of a simple line operations GO/NOGO manual tool.

      Three mechanisms are disclosed to ensure adequate bonding.
      Operators Torque Pencil (Fig. 1).

      Torque Watch (Fig. 2) for calibrating the Torque Pencil (Dial
Reading).

      X-Y Shear Tester (Fig. 3).  Accurate Analysis Tool (PC display
from strain gauges).

      The Torque Pencil Tool (Fig. 1) A Torque Pencil was developed
to be used as an inexpensive operator's tool for checking that a chip
adhesive came up to the required strength.  The tool has to be tested
and calibrated with the horizontal force tester. The design is
effectively a clutch developed within a pencil, set to slip at a
given force.

      Referring to Fig. 1, a cylindrical body 4 has projecting from
it an upper knob 1 flexibly held by suspension collar 3 and rotating
through a ball race 2. Encased in knob 1 is an adjustable clutch
plate 8 formed by loading ball 11 under spring 10 pressure adjusted
by grub screw 9.  The body 4 has three jaws 7 machined to fit a
particular size of chip 5.  When a different size chip is used, body
4 can be replaced by another with different jaw 7 dimensions to match
a new chip size.  A guide bush 6 with low surface area holds knob 1
central with the minimum of friction.

      Torque Watch Tool (Fig. 2) The Torque Watch Tool is a manually
operated tool to apply to a chip glued to a PCB to ascertain shear
tolerance. When tolerances have been ascertained with t...