from RF Power Amplifer for UHF TV Transmitter #1
MECHANICAL MACHINING OF THE HEATSINK
The raised edges at the top side of the heatsink have been removed because the printed circuit board has a width of 113 mm (see Fig.3). To fit the heatsink to the printed-circuit board the following machinings have been carried out:
MECHANICAL MACHINING OF THE HEATSINK
The raised edges at the top side of the heatsink have been removed because the printed circuit board has a width of 113 mm (see Fig.3). To fit the heatsink to the printed-circuit board the following machinings have been carried out:
- Rectangular holes of 2.8 mm deep have been mould in the heatsink because the transistor leads have to be soldered on the printed-circuit board. Also it was necessary to make avings of 4 mm wide and 0.6 mm deep at the positions of the straps on the printed-circuit board. The transistors have been fastened with M 2.5 screws in the heatsink (see Fig.4).
- To achieve that the printed-circuit board lays tight to the heatsink also savings have been made in the heatsink on the spots of the 8 rivets through the printed-circuit board.
CONCLUSIONS
With the construction of the BLV57 amplifiers a good thermal resistance (0.2 °C/W) has been achieved by means of a forced air-cooling. Attention has been payed to a good mechanical contact between heatsink and printed circuit board and a good ground contact on the printed circuit board by means of rivets and straps at the edges and under the emitter leads. (datasheet)
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