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Thermal Layer Metallurgy for Solder Ball Connect Substrate Rework

IP.com Disclosure Number: IPCOM000102145D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Seidel, VP: AUTHOR

Abstract

Present removal of solder ball connected (SBC) ceramic semiconductor substrates from cards for rework purposes entails heating the back side of the card where the substrate is located. The amount of heat required can damage other components on the card. A thermal layer located between the substrate and card, which can itself generate heat, will reduce the amount of backside heat required to remove the substrate, thus reducing potential damage to other card components.

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Thermal Layer Metallurgy for Solder Ball Connect Substrate Rework

       Present removal of solder ball connected (SBC) ceramic
semiconductor substrates from cards for rework purposes entails
heating the back side of the card where the substrate is located. The
amount of heat required can damage other components on the card. A
thermal layer located between the substrate and card, which can
itself generate heat, will reduce the amount of backside heat
required to remove the substrate, thus reducing potential damage to
other card components.

      Referring to the figure, a grid of fine metal lines runs
between substrate solder balls and allows the balls to extend through
the grid to contact card pads (not shown). Sufficient spacing is
maintained so that the solder balls do not electrically contact the
grid layer and result in short circuits. When a substrate attached to
a card requires rework (substrate removal), a current source is
connected to the thermal grid layer by means of a tab. Heat is
generated by the metal lines in proportion to the current forced, and
this heat is conducted to the area around each solder ball. This
allows for faster disconnection of the substrate and less heat to
other components on the same card.

      During normal operation, the thermal layer metallurgy may be
connected to the card ground by use of a grounding attach point. An
insulator between the thermal layer and the card would be required
for some card designs.