MIXERS - SUB-HARMONIC - CHIP
3
3 - 21
For price, delivery, and to place orders, please contact Hittite Microwave Corporation:
20 Alpha Road, Chelmsford, MA 01824 Phone: 978-250-3343 Fax: 978-250-3373
Order On-line at www.hittite.com
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).
An RF bypass capacitor should be used on the Vdd input. A 100 pF single layer
capacitor (mounted eutuctically or by conductive epoxy) placed no further than
0.762mm (30 Mils) from the chip is recommended. The photo in gure 3 shows a
typical assembly for the HMC264 MMIC chip.
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
Ball or wedge bond with 0.025 mm (1 mil) diameter pure gold wire. 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).
Figure 3: Typical HMC264 Assembly
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
HMC264
v02.1007
GaAs MMIC SUB-HARMONICALLY
PUMPED MIXER, 20 - 32 GHz