LOW NOISE AMPLIFIERS - CHIP
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Mounting & Bonding Techniques for Millimeterwave GaAs MMICs
The die should be attached directly to the ground plane eutectically or with
conductive epoxy (see HMC general Handling, Mounting, Bonding Note).
50 Ohm Microstrip transmission lines on 0.127mm (5 mil) thick alumina thin lm
substrates are recommended for bringing RF to and from the chip (Figure 1). If
0.254mm (10 mil) thick alumina thin lm substrates must be used, the die should be
raised 0.150mm (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 0.102mm (4 mil) thick
die to a 0.150mm (6 mil) thick molybdenum heat spreader (moly-tab) which is then
attached to the ground plane (Figure 2).
Microstrip substrates should be brought as close to the die as possible in order to
minimize bond wire length. Typical die-to-substrate spacing is 0.076mm (3 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 > ± 250V ESD
strikes.
Transients: Suppress instrument and bias supply transients while bias is applied.
Use shielded signal and bias cables to minimize inductive pick-up.
General Handling: Handle the chip along the edges with a vacuum collet or with
a sharp pair of bent tweezers. The surface of the chip has fragile air bridges and
should not be touched with vacuum collet, tweezers, or ngers.
Mounting
The chip is back-metallized and can be die mounted with AuSn eutectic preforms or
with electrically conductive epoxy. The mounting surface should be clean and at.
Eutectic Die Attach: A 80/20 gold tin preform is recommended with a work surface
temperature of 255 °C and a tool temperature of 265 °C. When hot 90/10 nitrogen/hydrogen gas is applied, tool tip temperature
should be 290 °C. DO NOT expose the chip to a temperature greater than 320 °C for more than 20 seconds. No more than 3
seconds of scrubbing should be required for attachment.
Epoxy Die Attach: Apply a minimum amount of epoxy to the mounting surface so that a thin epoxy llet is observed around the
perimeter of the chip once it is placed into position. Cure epoxy per the manufacturer’s schedule.
Wire Bonding
Ball or wedge bond with 0.025 mm (1 mil) diameter pure gold wire is recommended. Thermosonic wirebonding with a nominal stage
temperature of 150 °C and a ball bonding force of 40 to 50 grams or wedge bonding force of 18 to 22 grams is recommended. Use
the minimum level of ultrasonic energy to achieve reliable wirebonds. Wirebonds should be started on the chip and terminated on
the package or substrate. All bonds should be as short as possible <0.31 mm (12 mils).
0.102mm (0.004”) Thick GaAs 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 GaAs 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
Moly Tab
HMC-ALH102
v02.0209
GaAs HEMT MMIC WIDEBAND
LOW NOISE AMPLIFIER, 2 - 20 GHz
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