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RA06H8285M

RoHS Compliance, 820-851MHz 6W 12.5V, 3 Stage Amp. For MOBILE RADIO

Publication Date : Oct．2011

7

RECOMMENDATIONS and APPLICATION INFORMATION:

Construction:

This module consists of an alumina substrate soldered onto a copper flange. For mechanical protection, a plastic cap is

attached with silicone. The MOSFET transistor chips are die bonded onto metal, wire bonded to the substrate, and coated

with resin. Lines on the substrate (eventually inductors), chip capacitors, and resistors form the bias and matching circuits.

Wire leads soldered onto the alumina substrate provide the DC and RF connection.

Following conditions must be avoided:

a) Bending forces on the alumina substrate (for example, by driving screws or from fast thermal changes)

b) Mechanical stress on the wire leads (for example, by first soldering then driving screws or by thermal expansion)

c) Defluxing solvents reacting with the resin coating on the MOSFET chips (for example, Trichloroethylene)

d) ESD, surge, overvoltage in combination with load VSWR, and oscillation

ESD:

This MOSFET module is sensitive to ESD voltages down to 1000V. Appropriate ESD precautions are required.

Mounting:

Heat sink flatness must be less than 50 µm (a heat sink that is not flat or particles between module and heat sink may

cause the ceramic substrate in the module to crack by bending forces, either immediately when driving screws or later

when thermal expansion forces are added).

A thermal compound between module and heat sink is recommended for low thermal contact resistance and to reduce

the bending stress on the ceramic substrate caused by the temperature difference to the heat sink.

The module must first be screwed to the heat sink, then the leads can be soldered to the printed circuit board.

M3 screws are recommended with a tightening torque of 4.0 to 6.0 kgf-cm.

Soldering and Defluxing:

This module is designed for manual soldering.

The leads must be soldered after the module is screwed onto the heat sink.

The temperature of the lead (terminal) soldering should be lower than 350°C and shorter than 3 second.

Ethyl Alcohol is recommend for removing flux. Trichloroethylene solvents must not be used (they may cause bubbles in

the coating of the transistor chips which can lift off the bond wires).

Thermal Design of the Heat Sink:

Stage

(W)

(W)

(°C/W)

(A)

(V)

1

st

0.001

0.04

29.0

0.02

2

nd

0.04

1.2

4.5

0.28

3

rd

1.2

6.0

3.7

1.05

12.5

When mounting the module with the thermal resistance of 2.69 °C/W, the channel temperature of each stage transistor is:

The 175°C maximum rating for the channel temperature ensures application under derateed conditions.

Output Power Control:

Depending on linearity, the following two methods are recommended to control the output power:

a) Non-linear FM modulation:

When the gate voltage is close to zero, the RF input signal is attenuated up to 60 dB and only a small leakage current

flows from the battery into the drain.

b) Linear AM modulation: