HMC292A Data Sheet
Rev. 0 | Page 16 of 17
MOUNTING AND BONDING TECHNIQUES FOR MILLIMETER WAVE 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 transmission
lines on 0.127 mm (0.005 inches) thick alumina thin film
substrates (see Figure 37).
0.102mm (0.004″) THICK GaAs MMIC
WIRE BOND
RF GROUND PLANE
0.127mm (0.005″) THICK ALUMINA
THIN FILM SUBSTRA
TE
0.076mm
(0.003″)
13885-036
Figure 37. Routing RF Signals
If 0.254 mm (0.010 inches) thick alumina thin film substrates
must be used, raise the die 0.150 mm (0.006 inches) so that the
surface of the die is coplanar with the surface of the substrate.
One way to accomplish this is to attach the 0.102 mm
(0.004 inches) thick die to a 0.150 mm (0.006 inches) thick
molybdenum heat spreader (moly-tab) that is then attached
to the ground plane (see Figure 38).
0.102mm (0.004
″
) THICK GaAs MMIC
WIRE BOND
0.254mm (0.010″) THICK ALUMINA
THIN FILM SUBSTRATE
0.076mm
(0.003″)
0.150mm (0.006″) THICK
MOLY TAB
RF
GROUND PLANE
13885-038
Figure 38. Routing RF Signals (Raised)
Microstrip substrates must be brought as close to the die
as possible to minimize ribbon bond length. Typical die to
substrate spacing is 0.076 mm to 0.152 mm (0.003 inches to
0.006 inches). Gold ribbon of 0.076 mm (0.003 inches) width
and minimal length <0.31 mm (<0.012 inches) is recommended
to minimize inductance on RF, LO, and IF ports.
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 and are then 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% Au/20% Sn 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 a 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
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 schedule
provided by the manufacturer.
WIRE BONDING
RF bonds made with 0.003 inches × 0.0005 inches gold ribbon are
recommended for the RF ports. These bonds must be
thermosonically bonded with a force of 40 g to 60 g. DC bonds
of 0.025 mm (0.001 inches) 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, <0.31 mm (<0.012 inches).
