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9

HMC1086

v06.0318

25 WATT GAN MMIC POWER AMPLIFIER,

2 - 6 GHz

0.102mm (0.004”) Thick GaN MMIC

Wire Bond

RF Ground Plane

0.127mm (0.005”) Thick Alumina

Thin Film Substrate

0.076mm

(0.003”)

Figure 1.

0.102mm (0.004”) Thick GaN MMIC

Wire Bond

RF Ground Plane

0.254mm (0.010”) Thick Alumina

Thin Film Substrate

0.076mm

(0.003”)

Figure 2.

0.150mm (0.005”) Thick

Copper Tungsten

Mounting & Bonding Techniques for GaN MMICs

The die should be eutectically attached directly to the ground plane (see

HMC general Handling, Mounting, Bonding Note).

50 Ohm Microstrip transmission lines on 0.127 mm (5 mil) thick alumina

thin film substrates are recommended for bringing RF to and from the

chip (Figure 1). If 0.254 mm (10 mil) thick alumina thin film substrates

must be used, the die should be raised 0.150 mm (6 mils) so that the

surface of the die is coplanar with the surface of the substrate. One way

to accomplish this is to attach the 0.102 mm (4 mil) thick die to a copper

tungsten or CuMo heat spreader which is then attached to the thermally

conductive ground plane (Figure 2).

Microstrip substrates should be placed as close to the die as possible in

order to minimize bond wire length. Typical die-to-substrate spacing is

0.076 mm to 0.152 mm (3 to 6 mils).

Handling Precautions

Follow these precautions to avoid permanent damage.

Storage: All bare die are placed in either Waffle or Gel based ESD

protective containers, and then sealed in an ESD protective bag for

shipment. Once the sealed ESD protective bag has been opened, all die

should be stored in a dry nitrogen environment.

Cleanliness: Handle the chips in a clean environment. DO NOT attempt

to clean the chip using liquid cleaning systems.

Static Sensitivity: Follow ESD precautions to protect against ESD

strikes.

Transients: Suppress instrument and bias supply transients while bias

is applied. Use shielded signal and bias cables to minimize inductive

pick-up.

Die placement: A heated vacuum collect (180 °C) is the preferred method of pick up. Ensure that the area of

vacuum contact on the die is minimized to prevent cracking under differential pressure. All air bridges (if applicable)

must be avoided during placement. Minimize impact forces applied to the die during auto-placement.

Mounting

The chip is back-metallized with a minimum of 5 microns of gold and is the RF ground and thermal interface. It is

recommended that the chip be die mounted with AuSn eutectic preforms. The mounting surface should be clean

and flat.

Eutectic Reflow Process: An 80/20 gold tin 0.5 mil (13 um) thick preform is recommended with a work surface

temperature of 280 °C. Limit exposure to temperatures above 300 °C to 30 seconds maximum. A die bonder or

furnace with 95 % N

thermal expansion matching is critical for long term reliability.

Die Attach Inspection: X-ray or acoustic scan is recommended.

Wire Bonding

Thermosonic ball or wedge bonding is the preferred interconnect technique. Gold wire must be used in a diameter

appropriate for the pad size and number of bonds applied. Force, time and ultrasonics are critical parameters:

optimize for a repeatable, high bond pull strength. Limit the die bond pad surface temperature to 200 °C maximum.