In prototyping use I have added soldered on brass shim heat-sink flags to
power diodes and to power resistors.
Worked OK in that context.

In your context - if you run the resistor so that it is withing spec for
desired lifetime at operating temperature most of the heta loss must be by
radiation, with the leads then largely providing mechanical and electrical
connection.
The object is then to have leads which provide adequate mechanical support
and which LIMIT heat transmission to the board. Lengthening the leads AND
heat flagging them in some manner at tghe PCB end and not all the way up to
the resistor may [tm] act similarly to a simple RC filter with the lead
limiting energy flow rate and the flag having to deal with the energy that
does pass down the lead. This increases the temperature of the resistor
above what it would otherwise be at and reduces board temperature.

An 'adequate' result may be achievable by each coiling the leads in a tight
spiral so that thermal conductivity is much reduced. This could perhaps be
done aroung an insulatorv which is left in place to add mechanical
robustness. (Something like Richard's second drawing but with many small
turns. Electrical resistance rises slightly due to longer leads. Inductance
may be an issue depending on application.


Russell
--=20
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