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Method for a pressurized solder paste dispense alternative wafer bump process

IP.com Disclosure Number: IPCOM000007236D
Publication Date: 2002-Mar-06
Document File: 3 page(s) / 165K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a pressurized solder paste dispense alternative wafer bump process. Benefits include improved ease of manufacturing, and improved reliability.

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Method for a pressurized solder paste dispense alternative wafer bump process

Disclosed is a method for a pressurized solder paste dispense alternative wafer bump process. Benefits include improved ease of manufacturing, and improved reliability.

Background

              Conventionally, wafer bumps are generated through the semiconductor photolithography fabrication process (see Figure 1). It defines the pad pattern and metal plating for placing the bump precursor material (typically a lead-tin alloy) on to the wafer pads. The wafer is subjected to a heating process known as reflow that heats the bump precursor material above its melting point. The wafer cools and forms a bump. This process is very expensive (hundreds of dollars per wafer) and significantly adds to the cost of the individual device.

              Alternative conventional wafer bumping processes rely on stencil printing and ball placement technologies. These technologies provide advantages but also have drawbacks when applied to large wafers (300 mm) and to products with high bump counts, such as microprocessors.

General description

              Disclosed is a method of applying solder paste to the land pads on semiconductor circuitry while in wafer form. The process utilizes a stencil that matches the wafer-pad layout. Solder paste is applied to the stencil top and pushed down into the pattern holes. The thickness of the stencil and size of the holes determine volume of solder dispensed on the wafer. The stencil is placed into a fixture that provides a seal around the wafer pattern. The stencil is placed, bottom-side down onto the wafer. Pressure is applied through the fixture on the top of the stencil. The solder paste is pushed out the holes and onto the wafer while the stencil is raised at a predetermined rate. The paste is cleared out of the stencil and deposited on the wafer pads.

Advantages

              The disclosed method uses readily available manufacturing technology and equipment that can be modifie...