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Placing Solder Terminals on Silicon Wafers

IP.com Disclosure Number: IPCOM000038573D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Schmeckenbecher, AF: AUTHOR

Abstract

An extrusion method has been developed for close control of solder composition and its placement on semiconductor wafers. Instead of a conventional evaporation method, solder, with a composition identical to the composition of the starting bulk alloy, is extruded through a mask opening used for placement of the solder on the ball limiting metallurgy (BLM) pads on the wafer. In the proposed method, solder 1 (Fig. 1) is placed in a metal block 2. A piston 3 is used to extrude the solder through holes in (Image Omitted) three plates 4,5,6. A support plate with windows 7 is used to receive excess solder. The extrusion may be done at room temperature, or the device may be heated to lower the viscosity of the solder.

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Placing Solder Terminals on Silicon Wafers

An extrusion method has been developed for close control of solder composition and its placement on semiconductor wafers. Instead of a conventional evaporation method, solder, with a composition identical to the composition of the starting bulk alloy, is extruded through a mask opening used for placement of the solder on the ball limiting metallurgy (BLM) pads on the wafer. In the proposed method, solder 1 (Fig. 1) is placed in a metal block 2. A piston 3 is used to extrude the solder through holes in

(Image Omitted)

three plates 4,5,6. A support plate with windows 7 is used to receive excess solder. The extrusion may be done at room temperature, or the device may be heated to lower the viscosity of the solder. The three plates are made of a metal or alloy with a thermal coefficient of expansion (TCE) similar to that of silicon. The metal has to be harder than solder and not be wetted by liquid solder. Passivated 40-60 nickel-steel alloy or Mo is suitable. The plates 4, 5, 6 (Fig. 2) have holes 8 drilled which match the array of the BLM pads on the wafer. Their diameter is 20-30% larger than that of the pads. The top 4 and bottom 6 plates are each 2-5 mm thick, while the center plate 5 is 50-100 mm thick. The holes in the top plate may be flared so as to facilitate injection of the solder. Once the holes are filled with solder, the plates are removed from the press. While pressure is applied from the top, the center plat...