Browse Prior Art Database

Relief of Residual Stress in Solder Fillet

IP.com Disclosure Number: IPCOM000122042D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Kimura, S: AUTHOR

Abstract

Disclosed is a method for reinforcing I/O pin adhesion strength to ceramic substrate by reducing the thermal residual stress acting on the periphery of I/O pin solder fillet, which is created when the pins are soldered to the substrate. In order to reduce the residual stress, compressive plastic deformation is created in the solder I/O pin fillet.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 77% of the total text.

Relief of Residual Stress in Solder Fillet

      Disclosed is a method for reinforcing I/O pin adhesion
strength to ceramic substrate by reducing the thermal residual stress
acting on the periphery of I/O pin solder fillet, which is created
when the pins are soldered to the substrate.  In order to reduce the
residual stress, compressive plastic deformation is created in the
solder I/O pin fillet.

      The figure shows the typical I/O pin structure.  The tensile
residual stress remains around the periphery of I/O pin solder fillet
2, because the thermal expansion coefficient of solder is much larger
than that of ceramic substrate 3.  This stress also induces tensile
stress in the ceramic substrate under the periphery of I/O pin 1.
This tensile stress in the substrate makes weak the I/O pin adhesion
strength.  As a result, crack 5 occurs and expands from the periphery
of I/O pin when force acts to I/O pin.

      In order to make strong the I/O pin adhesion strength, it is
effective to reduce the maximum residual tensile stress in the
ceramic substrate or to change the direction of the residual stress
from tensile to compression.  Solder used for the I/O pin fillet is
metal.  So it has a plastic deformation ability enough to relieve the
elastic strain which is calculated by dividing stress by elastic
modulus.

      By pushing solid ring or bar 4 into the periphery of the I/O
pin fillet 2, compressive plastic deformation is created in the
solder, which...