The ninety-odd spreaders I made were tapped M3. I assumed the
idea was to clamp the PCB to the spreader using an M3 screw in the
tapped hole for soldering, then discard the M3 and use the M3
tapped hole as an M2.5 clearance (just) hole to fix the whole
thing to a heatsink.
Just guessing mind, although I made all those spreaders, I
haven't made an amplifier for myself.
On 30/09/2020 21:02, militaryoperator
via groups.io wrote:
the instructions are the other way, drill tap 3mm then fix with
i think the copper tapped to 2.5 was to secure the
spreader while the fet is soldered,
Then the holes opened to 3mm to take bolts to
compression fit the board and copper spreader to the
heatsink, it would not be possible to get the spreader
compressed to the heatsink with threads in the copper,
On Wednesday, 30 September 2020, 18:29:49 BST,
militaryoperator via groups.io
A bit unclear.
Notes on fitting the heat spreader to
the G4BAO/G7NTG 70 watt PA
The centre holes in the PCB should be
opened out to 3mm and secured to the heat
spreader with a smear of solder paste in
between them with two short M3 stainless
The screws are then removed and then
the pcb can be fixed to the heatdink with
2 x m2.5mm screws.
If I have tapped two 3mm holes how can
2.5mm bolts fit?