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PACKAGING

Removing the Etched Wafers The result of the coating/etching process is a silicon wafer that contains from 100 to 400 integrated circuits, each of which includes millions of transistors.

Mounting the Wafers

Each wafer is vacuum mounted onto a metal-framed sticky film tape. The wafer and metal frame are placed near the tape; then all three pieces are loaded into a vacuum chamber. A vacuum forces the tape smoothly onto the back of the wafer and metal frame.

Dicing the Wafers

A diamond-edged saw, with a thickness of a human hair, separates the wafer into individual processors, known as die, in a process called dicing. Water spray keeps the surface temperature low. After cutting, high-pressure water rinses the wafer clean. In some situations, special lasers are used to cut the wafers.

Attaching the Die

Individual die are attached to silver epoxy on the center area of a lead frame. Each die is removed from the tape with needles plunging up from underneath to push the die while a vacuum tip lifts the die from the tape. Lead frames are then heated in an oven to cure the epoxy. The wafer map created in probe tells the die-attach equipment which die to place on the lead frame.

Packaging the Chips

The chips are packaged in protective ceramic or metal carriers. The carriers have standard-sized electrical pin connectors that allow the chip to be plugged conveniently into circuit boards. Because the pins tend to corrode, the pin connectors are the most vulnerable part of a computer system. To avoid corrosion and a bad connection, the pins on some carriers are made of gold.