RA20H8087M Datasheet, PDF (8/10 Pages) Mitsubishi Electric Semiconductor – 806-825/ 851-870MHz 20W 12.5V, 3 Stage Amp. For MOBILE RADIO

ELECTROSTATIC SENSITIVE DEVICE
OBSERVE HANDLING PRECAUTIONS
MITSUBISHI RF POWER MODULE
RA20H8087M
PRECAUTIONS, 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, Trichlorethylene)
d) Frequent on/off switching that causes thermal expansion of the resin
e) 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 0.4 to 0.6 Nm.
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 soldering temperature must be lower than 260°C for a maximum of 10 seconds, or lower than 350°C for a maximum
of three seconds.
Ethyl Alcohol is recommend for removing flux. Trichlorethylene 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:
At P_out=20W, V_DD=12.5V and P_in=50mW each stage transistor operating conditions are:
Stage
P_in
(W)
P_out
(W)
R_th(ch-case)
(°C/W)
I_DD @ η_T=25%
(A)
V_DD
(V)
1^st
0.05
1.0
4.5
0.50
2^nd
1.0
8.0
3.2
1.90
12.5
3^rd
8.0
20.0
1.6
3.90
The channel temperatures of each stage transistor T_ch = T_case + (V_DD x I_DD - P_out + P_in) x R_th(ch-case) are:
T_ch1 = T_case + (12.5V x 0.50A - 1.0W + 0.05W) x 4.5°C/W
T_ch2 = T_case + (12.5V x 1.90A - 8.0W + 1.0W) x 3.2°C/W
T_ch3 = T_case + (12.5V x 3.90A - 20.0W + 8.0W) x 1.6°C/W
= T_case + 23.9 °C
= T_case + 53.6 °C
= T_case + 58.8 °C
For long-term reliability, it is best to keep the module case temperature (T_case) below 90°C. For an ambient
temperature T_air=60°C and P_out=20W, the required thermal resistance R_{th (case-air)} = ( T_case - T_air) / ( (P_out / η_T ) - P_out +
P_in ) of the heat sink, including the contact resistance, is:
R_th(case-air) = (90°C - 60°C) / (20W/25% - 20W + 0.05W) = 0.50 °C/W
When mounting the module with the thermal resistance of 0.50 °C/W, the channel temperature of each stage transistor
is:
T_ch1 = T_air + 53.9 °C
T_ch2 = T_air + 83.6 °C
T_ch3 = T_air + 88.8 °C
The 175°C maximum rating for the channel temperature ensures application under derated conditions.
RA 20H8087M
MITSUBISHI ELECTRIC
8/10
25 April 2003