Browse Prior Art Database

Repairable Plastic Ball Grid Array Package

IP.com Disclosure Number: IPCOM000115954D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Frankeny, JA: AUTHOR [+4]

Abstract

Disclosed here is a method for making a plastic ball grid array, using a C4 chip attachment technology, that will still allow repair of the module ball array, without reflow of the chip attach C4 joints. The Figure shows the structure of the module. The difference between the disclosed structure and the standard non-repairable plastic ball grid array lies in the palladium dendrites plated on the chip attachment pads(1). This plating is produced by a process which produces a surface of built-up cones and needles instead of a flat smooth surface. A flash of gold may be plated on the dendrites to improve electrical contact and solderability.

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Repairable Plastic Ball Grid Array Package

      Disclosed here is a method for making a plastic ball grid
array, using a C4 chip attachment technology, that will still allow
repair of the module ball array, without reflow of the chip attach C4
joints.  The Figure shows the structure of the module.  The
difference between the disclosed structure and the standard
non-repairable plastic ball grid array lies in the palladium
dendrites plated on the chip attachment pads(1).  This plating is
produced by a process which produces a surface of built-up cones and
needles instead of a flat smooth surface.  A flash of gold may be
plated on the dendrites to improve electrical contact and
solderability.

      In manufacturing, the eutectic tin-lead solder C4 balls of the
chip(2) are pressed into place on the dendrites plated attachment
pads.  At this point an electrical connection is made and the chip
can be tested in-situ.  If the chip is found to be defective it can
be removed easily, since only a temporary metallic contact is formed.
If the chip is good it can be reflowed in place at the standard
melting
point of eutectic tin-lead (183 degrees C), without damage to the
substrate(3).  The joining metallurgy for the chip to the substrate
is between the eutectic tin-lead balls and the palladium dendrites
plated on the attachment pads.

      After testing, the chip and the substrate are ready for
joining.  As the joining temperature exceeds the melting point of the
...