Mounting LM317 TO-3 case

Thread Starter

keiichicom

Joined Apr 26, 2022
76
Hi Guys and Gals,

How do I attach TO-3 ICs like this one to a prototyping board or pc board and add a heat sink?
One of the 3 IC leads is attached to the metal top:

lm317.png

Thanks in Advance
 

BobTPH

Joined Jun 5, 2013
9,160
You don’t. These are designed to be mounted in a separate heat sink with wired connections to the PCB. Use the TO-220 version if you want it PCB mounted.
 

Thread Starter

keiichicom

Joined Apr 26, 2022
76
Thanks, Bob. So probably after inserting them in the heat skink, they are attached to the project case with bolts/screws and the 3 wires go to the pc board?
 

dl324

Joined Mar 30, 2015
17,007
How do I attach TO-3 ICs like this one to a prototyping board or pc board and add a heat sink?
You can solder/clip wires to the terminals and insert the wires into the breadboard/board. Adding a heatsink would be done in a similar fashion as you'd use for the final assembly. If you're using a solderless prototyping board, take care in how much current you allow in the transistor. I've acquired several second hand solderless breadboards that look like they were abused in this manner.

Attaching wires to the leads of TO-3 devices is quite common as that's usually how they're attached in finished products.
 

MrChips

Joined Oct 2, 2009
30,961
You can use TO-3 mounting kit that includes a mica washer and nylon sleeves. This keeps the device insulated from the heat sink.
 

Thread Starter

keiichicom

Joined Apr 26, 2022
76
You can solder/clip wires to the terminals and insert the wires into the breadboard/board. Adding a heatsink would be done in a similar fashion as you'd use for the final assembly. If you're using a solderless prototyping board, take care in how much current you allow in the transistor. I've acquired several second hand solderless breadboards that look like they were abused in this manner.

Attaching wires to the leads of TO-3 devices is quite common as that's usually how they're attached in finished products.
thanks for info
 

ElectricSpidey

Joined Dec 2, 2017
2,837
When using a socket be sure to use one with the proper lead diameter.

Putting a high current TO3 transistor into a "standard" socket is nearly impossible.

A typical TO3 socket.
1674749454534.png
 
Last edited:

crutschow

Joined Mar 14, 2008
34,690
You can use TO-3 mounting kit that includes a mica washer and nylon sleeves. This keeps the device insulated from the heat sink.
If you don't need the heatsink to be electrically isolated from the IC then just mount the device directly on the sink with a thin layer of thermal grease.
That will give the lowest thermal resistance from the device to the sink.
You can then isolate the heatsink from the circuitry if necessary.
 
TO3 devices have become very expensive, see below, and as such their use is diminishing rapidly. Mounting hardware used to be ubiquitous, but I haven’t checked in a while. Suggest that you procure something.
1674763097326.png
 
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