MIXERS - I/Q MIXERS / IRM - CHIP
3
3 - 65
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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 ribbon bond length. Typical die-to-substrate spacing is 0.076mm (3
mils). Gold ribbon of 0.075 mm (3 mil) width and minimal length <0.31 mm (<12
mils) is recommended to minimize inductance on RF, LO & IF ports.
An RF bypass capacitor should be used on the Vdd input. A 100 pF single layer
capacitor (mounted eutectically or by conductive epoxy) placed no further than
0.762mm (30 Mils) from the chip 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
HMC404
v03.0907
GaAs MMIC SUB-HARMONICALLY
PUMPED IRM MIXER, 26 - 33 GHz
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