Data Sheet HMC8121
Rev. B | Page 15 of 16
MOUNTING AND BONDING TECHNIQUES FOR MILLIMETERWAVE GaAs MMICS
Attach the die directly to the ground plane eutectically or with
conductive epoxy.
To bring RF to and from the chip, use 50 Ω microstrip trans-
mission lines on 0.127 mm (5 mil) thick alumina thin film
substrates (see Figure 40).
RF GROUND PLANE
0.05mm (0.002") THICK GaAs MMIC
RIBBON BOND
0.127mm (0.005") THICK ALUMINA
THIN FILM SUBSTRATE
0.076mm
(0.003")
13154-037
Figure 40. Routing RF Signals
To minimize bond wire length, place microstrip substrates as
close to the die as possible. Typical die to substrate spacing is
0.076 mm to 0.152 mm (3 mil to 6 mil).
HANDLING PRECAUTIONS
To avoid permanent damage, adhere to the following
precautions.
Storage
All bare die ship in either waffle or gel-based ESD protective
containers, sealed in an ESD protective bag. After opening the
sealed ESD protective bag, all die must be stored in a dry
nitrogen environment.
Cleanliness
Handle the chips in a clean environment. Never use liquid
cleaning systems to clean the chip.
Static Sensitivity
Follow ESD precautions to protect against ESD strikes.
Transients
Suppress instrument and bias supply transients while bias is
applied. To minimize inductive pickup, use shielded signal and
bias cables.
General Handling
Handle the chip on the edges only using a vacuum collet or with
a sharp pair of bent tweezers. Because the surface of the chip
has fragile air bridges, never touch the surface of the chip with a
vacuum collet, tweezers, or fingers.
MOUNTING
The chip is back metallized and can be die mounted with gold/tin
(AuSn) eutectic preforms or with electrically conductive epoxy.
The mounting surface must be clean and flat.
Eutectic Die Attach
It is best to use an 80% gold/20% tin preform with a work surface
temperature of 255°C and a tool temperature of 265°C. When
hot 90% nitrogen/10% hydrogen gas is applied, maintain tool tip
temperature at 290°C. Do not expose the chip to a temperature
greater than 320°C for more than 20 sec. No more than 3 sec of
scrubbing is required for attachment.
Epoxy Die Attach
ABLEBOND 84-1LMIT is recommended for die attachment.
Apply a minimum amount of epoxy to the mounting surface so
that a thin epoxy fillet is observed around the perimeter of the
chip after placing it into position. Cure the epoxy per the
schedule provided by the manufacturer.
WIRE BONDING
RF bonds made with 0.003 in. × 0.0005 in. gold ribbon are recom-
mended for the RF ports. These bonds must be thermosonically
bonded with a force of 40 g to 60 g. DC bonds of 0.001 in.
(0.025 mm) diameter, thermosonically bonded, are recommended.
Create ball bonds with a force of 40 g to 50 g and wedge bonds
with a force of 18 g to 22 g. Create all bonds with a nominal
stage temperature of 150°C. Apply a minimum amount of
ultrasonic energy to achieve reliable bonds. Keep all bonds as
short as possible, less than 12 mil (0.31 mm).
