Hey Tony - That is an interesting result. There is no substitute
for actual measurement. This suggests that case contact with the
pad is important. I always install the BS170s first with the screw
and washer ensuring they are all flat and only then solder in
place. Thanks for your efforts! Sandy KB3EOF
On 9/11/24 22:18, mux_folder2001 via
groups.io wrote:
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I have attached a PDF file that describes an experiment with the
goal of determine where the heat flows in a BS170. The PDF
contains pictures of the fixture and a graph of the results. The
essence of it is that, given equal opportunity, heat will flow
as follows:
-
Best flow is through the case.
-
Second best flow is the drain
lead.
-
A distant third is the source
lead.
-
Last is the gate lead.
The graph will give you a sense of how much difference there is
between them.?
The transistor is configured in a DC circuit and is dissipating
767mw continuously in the test. I should have put that in the
PDF file but I forgot to.
Tony
AD0VC
