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 accom-
plish 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 brought as close to the die as possible in order
to minimize bond wire length. Typical die-to-substrate spacing is 0.076mm
to 0.152 mm (3 to 6 mils). Gold ribbon of 0.075 mm (3 mils) width and minimum
< 0.31 mm (<12 mils) is recommended.
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.
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
RF bonds made with 0.003” x 0.0005” ribbon are recommended. These bonds should be thermosonically bonded
with a force of 40-60 grams. DC bonds of 0.001” (0.025 mm) diameter, thermosonically bonded, are recommended.
Ball bonds should be made with a force of 40-50 grams and wedge bonds at 18-22 grams. All bonds should be made
with a nominal stage temperature of 150 °C. A minimum amount of ultrasonic energy should be applied to achieve
reliable bonds. All bonds should be as short as possible, less than 12 mils (0.31 mm).
0.102mm (0.004”) Thick GaAs MMIC
3 mil Ribbon 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
3 mil Ribbon 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
HMC517
v02.0907
GaAs PHEMT MMIC LOW NOISE
AMPLIFIER, 17 - 26 GHz
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