Hi,
I have some bushes for the TO-220 package, and these fit no issue to the backplate of the transistor.
The BD139/BD140 is a TO-225 package, and the hole in the transistor is not large enough for the TO-220 bush.
The rear of the BD139/140 has the collector electrical connection, and the 3mm hole seems to be insulated.
Can anyone confirm that using an M3 screw to secure the transistor to the heatsink, with the thermal insulation in place, is acceptable.
I am unable to locate any M2.5 bushes from Farnell, RS Electronics, Mouser, Digikey etc., which leads me to believe that they are not generally available since TO-225 packages do not require them since they have the necessary insulation around the hole.
Thanks and regards,
Shadders.
I have some bushes for the TO-220 package, and these fit no issue to the backplate of the transistor.
The BD139/BD140 is a TO-225 package, and the hole in the transistor is not large enough for the TO-220 bush.
The rear of the BD139/140 has the collector electrical connection, and the 3mm hole seems to be insulated.
Can anyone confirm that using an M3 screw to secure the transistor to the heatsink, with the thermal insulation in place, is acceptable.
I am unable to locate any M2.5 bushes from Farnell, RS Electronics, Mouser, Digikey etc., which leads me to believe that they are not generally available since TO-225 packages do not require them since they have the necessary insulation around the hole.
Thanks and regards,
Shadders.
Last edited:
Hi,Yes, that's just fine
/U.
Thanks - seemed obvious- but wanted to check.
Regards,
Shadders.
No,just do not trust this!Yes, that's just fine
/U.
Just yesterday i had an issue using 3mm screw to fix a bd139Vbe multiplier.
Yes, the hole seems isolated but screw easy destroy the isolation.
Hi,
Thanks - i did locate some 3mm out diameter and M2 inner diameter bushes. When you search bush on the internet, a lot of non-electronic engineering results are returned.
https://uk.farnell.com/c/fasteners-...xings/spacers-feet/spacers?outer-diameter=3mm
Regards,
Shadders.
Hi,
Thanks - i located them from Farnell UK. I did just try bushings, and similar to bush, but the range of products on Google refers to too many false hits.
I am surprised, that if people have had issues with te TO-220 package, that their availability is not more prolific.
The bushes ordered from Farnell are a perfect fit, aside from a slight reduction in the length for 3mm, which needs to be trimmed.
Regards,
Shadders.
Thanks - i located them from Farnell UK. I did just try bushings, and similar to bush, but the range of products on Google refers to too many false hits.
I am surprised, that if people have had issues with te TO-220 package, that their availability is not more prolific.
The bushes ordered from Farnell are a perfect fit, aside from a slight reduction in the length for 3mm, which needs to be trimmed.
Regards,
Shadders.
The TO126 is specifically designed to be used with 3mm screws and provide isolation.
It is however good practice to use a belleville or compression washer between the screw head and the transistor body, for two reasons:
1 It spreads the pressure on the whole body
2 Many screws have an uncontrolled diameter or burrs very close to the head, and this can damage the plastic
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