Testing - under computer control, the probe station automatically steps across the wafer performing functional testing at each die site.

die separation -

1. the wafer is mounted on a holder and automatically scribed in both x and y directions using a diamond-tipped scribe
2. diamond saws are also widely used for die separation

1. epoxy die attachment
2. eutectic die attachment

Wire bonding is the most widely used method for making electrical connection between the die and the package. There are at least three types of bonding:

thermocompression bonding (nail head or ball binding) - a combination of pressure and temperature to weld a fine gold wire to the aluminum bonding pads 15 to 75 m m in diameter

ultrasonic bonding - a combination of pressure and rapid mechanical vibration, is used with aluminum wire

thermosonic bonding - a combination of ultrasonic and thermocompression bonding

"Purple Plague"

  A problem encountered in the production of gold-aluminum bonds is the formation of the "purple plague." Gold and aluminum react to intermetallic compounds.

AuAl₂ is purple-colored

Au₂Al is tan-colored

 AuAl₂ appeared to be the culprit associated with a faulty bonds. However, this compound is highly conductive. The actual culprit is a low-conductivity, tan-colored compound, Au₂Al, which is also present. Limiting the die temperate helps to prevent the formation of intermetallic compounds.

Packages

Integrated-circuit dice can be mounted in a wide array of packages:

1. Circular TO-Style packages
2. Dual-in-line package (DIPs)
3. Pin-grid arrays (PGAs)
        Leadless chip carriers
        Surface mounting
4. Flip-Chip and Tape-automated-bonding

TO PAGE 2