The 3 pin TO-92 looks like it’s plastic, so I’m already worried about low thermal conductivity.* However, how should I secure this to ensure that the chip has the best thermal conduction? Thermal paste crossed my mind, but it’d be pointless to add that with plastic unless there is a big gap there.
I haven’t picked out a heatsink yet, but there are plenty of them with a fairly large, flat surface that I could attach the sensor to if I needed. However, I can’t glue it onto the heatsink because most glue doesn’t conduct heat.
What I’d typically do is to use a tiny amount of non-conductive heat compound to thermally bond the flat side of the sensor to the heat sink, down between the ribs of possibly, and centered if possible. Basically try to get it to where you think will be the hottest. You don’t need a lot, it’s basically just to avoid air in microscopic gaps between the heat sink and plastic. Then secure it in-place with glue. Don’t worry too much about the plastic, it’s got some thermal resistance, but not that much. Don’t gunk up with too much glue either, would be a thermal buffer and would also isolate the heat sink from the air it’s supposed to move heat to.
If you got enough thickness in the heatsink, you can drill a hole so that maybe 80% of the plastic sits in the hole, then use Fujik to hold it in-place. Fujik is rubbery enough so that you can, if need be, pop it out. The TO-92 is a half-circle, so just complete the circle with a drilled hole.
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Do you need digital control, though? Sometimes it’s just easier to use a thermistor in a metal case like this
