Browse Prior Art Database

Solder Well Cap and Process

IP.com Disclosure Number: IPCOM000088843D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Koopman, N: AUTHOR

Abstract

A shaped solder body can be formed by reflow on the backside of a semiconductor chip. A solder preform 9 is placed, as shown in Fig. 1, in well cap 10 and the structure placed on the back of semiconductor chip 11, which has electrical contacts 12 connected to substrate 13. The assembly is placed in a furnace held at a temperature above the solder's melting point. Solder reflow causes the solder to fill the lower cavity of the cap 10, as shown in Fig. 2, at the expense of the reservoir. The well cap 10 contains the solder so it does not flow out over the chip 11 edge.

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Solder Well Cap and Process

A shaped solder body can be formed by reflow on the backside of a semiconductor chip. A solder preform 9 is placed, as shown in Fig. 1, in well cap 10 and the structure placed on the back of semiconductor chip 11, which has electrical contacts 12 connected to substrate 13. The assembly is placed in a furnace held at a temperature above the solder's melting point. Solder reflow causes the solder to fill the lower cavity of the cap 10, as shown in Fig. 2, at the expense of the reservoir. The well cap 10 contains the solder so it does not flow out over the chip 11 edge.

Solder is now constrained on all six sides so that the impact of shock cannot dislodge or move it. The maximum area on the chip surface is covered with solder. An alternative geometry for the well cap is shown in Figs. 3 and 4. Fig. 3 shows alternate well cap 14 and solder preform 15 before reflow, and Fig. 4 shows the situation after reflow.

These structures allow a cost effective, low thermal resistance path to be made between the chip and the cap for high power dissipation. No metallurgical bonding of the solder to either the cap or the chip takes place.

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