HMC1049

Data Sheet

Rev. B | Page 12 of 14

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 36).

If 0.254 mm (10 mil) thick alumina thin film substrates are

required, raise the die by 0.150 mm (6 mil) to ensure that the

surface of the die is coplanar with the surface of the substrate.

One method to accomplish this coplanarity is to attach the

0.102 mm (4 mil) thick die to a 0.150 mm (6 mil) thick molyb-

denum heat spreader (molytab), and then attach the unit to the

ground plane (Figure 37).

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 36. RF Lines

0.254mm (0.010”) THICK ALUMINA

THIN FILM SUBSTRATE

0.150mm (0.005") THICK

MOLY TAB

0.102mm (0.004") THICK GaAs MMIC

WIRE BOND

0.076mm

(0.003")

RF GROUND PLANE

Figure 37. Die Attachment Using Molybdenum Heat Spreader

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 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 80/20 gold tin preform with a work surface

temperature of 255°C and a tool temperature of 265°C. When

hot 90/10 nitrogen/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 should be required for attachment.

Epoxy Die Attach

Apply a minimum amount of epoxy to the mounting surface so

that upon placing it into position, a thin epoxy fillet is observed

around the perimeter of the chip. Cure epoxy per the schedule

provided by the manufacturer.