Data Sheet HMC8402
Rev. A | Page 13 of 15
APPLICATIONS INFORMATION
BIASING PROCEDURES
Capacitive bypassing is required for V
DD
, as shown in the typical
application circuit in Figure 38. Gain control is possible through
the application of a dc voltage to V
GG
2. If gain control is used, V
GG
2
must be bypassed by 100 pF, 0.01 μF, and 4.7 μF capacitors. If gain
control is not used, V
GG
2 can be either left open or capacitively
bypassed as described.
The recommended bias sequence during power-up is as follows:
1. Set V
DD
to 7 V (this results in an I
DQ
near its specified
typical value).
2. If the gain control function is to be used, apply to V
GG
2 a
voltage within the range of −2 V to +2.6 V until the desired
gain is achieved.
3. Apply the RF input signal.
The recommended bias sequence during power-down is as follows:
1. Turn off t he RF input signal.
2. Remove the V
GG
2 voltage or set it to 0 V.
3. Set V
DD
to 0 V.
Unless otherwise noted, all measurements and data shown were
taken using the typical application circuit (see Figure 38), configured
as shown on the assembly diagram (see Figure 39) and biased
per the conditions in the Specifications section. The bias conditions
shown in the Specifications section are the operating points
recommended to optimize the overall performance. Operation
using other bias conditions may provide performance that differs
from what is shown in this data sheet. To obtain the best
performance while not damaging the device, follow the
recommended biasing sequence outlined in this section.
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 transmission lines on 0.127 mm (5 mil) thick alumina
thin film substrates (see Figure 37).
Figure 37. 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:
All bare die ship in either waffle or gel-based ESD protective
containers, sealed in an ESD protective bag. After the sealed
ESD protective bag is opened, store all die in a dry nitrogen
environment.
Handle the chips in a clean environment. Never use liquid
cleaning systems to clean the chip.
Follow ESD precautions to protect against ESD strikes.
While bias is applied, suppress instrument and bias supply
transients. To minimize inductive pickup, use shielded
signal and bias cables.
Handle the chip along the edges with a vacuum collet or
with a sharp pair of bent tweezers. The surface of the chip
may have fragile air bridges and must not be touched with
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
ABLETHERM 2600BT 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 1 mil (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).
RF GROUND PLANE
0.051mm (0.002") THICK GaAs MMIC
WIRE BOND
0.254mm (0.010") THICK ALUMINA
THIN FILM SUBSTRATE
0.150mm
(0.005”) THICK
MOLY TAB
0.076mm
(0.003")
13853-037
