Browse Prior Art Database

Chip Packaging Stress Relief by Use of an Overflow Reservoir

IP.com Disclosure Number: IPCOM000043733D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Gupta, OR: AUTHOR [+2]

Abstract

A technique is described whereby an overflow reservoir is used to provide stress relief to a semiconductor chip mounting, when thermal grease is used in heat dissipation. Thermal grease is used effectively in electronic circuit assembly and is applied between the semiconductor chip and the mounting cap to provide heat conduction to a heat sink or to convect the heat to the ambient air. The semiconductor chip 1, as shown in Fig. 1, is mounted via solder balls 2 onto a substrate 3. Dabs of thermal grease 4 are placed between chip 1 and module cap 5. The module cap 5 is positioned so that a desired gap 6 is attained between chip 1 and cap 5. Pressure is applied to spread the thermal grease 4 from the center of the chip 1 to the periphery.

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Chip Packaging Stress Relief by Use of an Overflow Reservoir

A technique is described whereby an overflow reservoir is used to provide stress relief to a semiconductor chip mounting, when thermal grease is used in heat dissipation. Thermal grease is used effectively in electronic circuit assembly and is applied between the semiconductor chip and the mounting cap to provide heat conduction to a heat sink or to convect the heat to the ambient air. The semiconductor chip 1, as shown in Fig. 1, is mounted via solder balls 2 onto a substrate 3. Dabs of thermal grease 4 are placed between chip 1 and module cap 5. The module cap 5 is positioned so that a desired gap 6 is attained between chip 1 and cap 5. Pressure is applied to spread the thermal grease 4 from the center of the chip 1 to the periphery. This pressure has caused the chips to fracture because of sheer forces acting on the thermal grease. To eliminate this damaging effect, the flat surface 7 of module cap 5 has been modified as shown in Fig. 2. The cross-section of Fig. 2 shows the modified module cap 8 to include a series of grooves 9, replacing the flat surface 7. The grooves 9 enable the thermal grease 4 to spread across chip 1, still maintaining the required gap between cap 8 and chip 1, but requiring much less pressure to spread the thermal grease. The grooves provide an overflow reservoir to capture excess thermal grease. Without the grooves, the thermal grease 4 is squeezed when the cap 5 is position...