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3.0 Die Attach Procedure
Different die attach procedures are used for silicon chips and GaAs devices. To die attach a silicon chip, the chip and mounting surface are heated sufficiently for the gold of the mounting surface to mix with the gold backside of the chip and melt into the silicon of the chip, forming a
GaAs devices are more temperature sensitive, and use instead a lower temperature gold alloy “solderdown” technique. In both cases the die- attach station should have the actual die attach area flooded with an inert (forming gas or nitrogen) atmosphere.
3.1 Silicon Bipolar Transistor Die Attach Procedure
3.1.1The heater block temperature should be 410°C ±10°.
3.1.2Place the circuit or package into which the transistor or capacitor will be attached on the heater block. Allow sufficient time to heat thoroughly (5 to 15 seconds depending on thermal mass).
3.1.3Pick up a chip with tweezers (EREM type 5 SA recommended) and orient it properly prior to placement on the heated surface.
3.1.4Place the chip on the heated surface and scrub with a
3.1.5If wetting does not occur check that the heater block temperature is correct and that the inert atmosphere blanket is present.
3.1.6When wetting occurs, perform a circular scrub for one stroke to insure wetting of the chip perimeter. Carefully remove the tweezers from the die.
3.1.7Remove the circuit or package from the heated surface and allow it to cool in air.
3.2 GaAs FET Attach Procedure
3.2.1The heater block temperature should be 300°C ±10°.
3.2.2Place the circuit or package into which the transistor will be attached on the heater block. Allow sufficient time to heat thoroughly (5 to 15 seconds depending on thermal mass).
3.2.3Pick up a
