Bonding Procedures, Ball Bonding

3.2.4Pick up a chip with tweezers (EREM type 5 SA recommended) and orient it properly prior to placement on the heated surface.

3.2.5Place the chip on the heated surface and scrub with a back-and- forth motion being careful not to scratch the top surface of the chip. Continue this until wetting occurs; this should take place within 3 to 4 scrubs.

3.2.6If wetting does not occur check that the heater block temperature is correct and that the inert atmosphere blanket is present.

3.2.7When wetting occurs, perform a circular scrub for one stroke to insure wetting of the chip perimeter. Carefully remove the tweezers from the die.

3.2.8Remove the circuit or package from the heated surface and allow it to cool in air.

4.0 Bonding Procedures

Either gold-ball bonding or thermocompression (wedge) bonding may be used on almost all HP transistors. Bonding pad sizes and metal adhesion strengths are compatible with either technique, thus giving the circuit designer the flexibility to use either approach. In general, for higher frequency use (greater than 8 GHz), a thermocompression wedge bond is preferred because of the resulting shorter bond lengths and reduced electrical parasitics.

4.1 Ball Bonding

HP, in the majority of cases, has used West Bond Model 7700 (Thermosonic) and 7716 (Thermocompression) series ball bonders for assembly, but any bonder capable of handling 0.001" or smaller diameter gold wire is appropriate. Prestressed (annealed) wire is preferred. Two modes of operation, Thermosonic and Thermocompression, are possible, with slightly different conditions required for each.

4.1.1Heater Block Temperature

4.1.1.1 Thermocompression

Calibrate the heater block temperature to 300°C ± 10° for Si Bipolar devices and 260°C ±10° for GaAs FETs.

4.1.1.2 Thermosonic (or Ultrasonic)

Calibrate the heater block temperature to 150°C ± 10°.

4.1.2 Calibrate bond force as follows:	MWB: 0.0007, 20 ±2
Ball Bond: 0.0007, 15-20 gram	MWB: 0.0007, 20 ±2
0.001, 20-30 gram	0.001, 25 ±2

4.1.3Proceed with bonding according to machine specifications.

4.1.4General Comments:

The normal approach is to place the ball on the circuit bonding pad and then complete the second bond to the chip.