Reusing a Computer Heatsink to Create a Transistor Heatsink

A while ago I bought some Raspberry Pi 3s to play around with. As they come with no heatsink I was in the market for some. I did a quick Google search and came across this Instructable (Raspberry Pi Heat Sink) - this was after rejecting the idea of purchasing them after seeing they would be so easy to make. I already had some thermal compound from a failed attempt to fix an Xbox 360 red ring of death a few years back. Being on the lookout for used heatsinks I started obsessing with heatsinks and after fixing my Raspberry Pis I made a bunch more to give out to friends, family and random people! Anyway I digress…

Is you transistor running hot and needs cooling down? If you do not have a heatsink handy to make it run cooler in your amazing new idea that you are prototyping then this Instructable is going to show you to create a heatsink for it. NOTE: the resulting heatsink from following this Instructable is best suited to PNP type of transistors (such as a TIP41C as the one shown in the pictures) - I am still learning about all electronic components so apologies for not using proper terminology; however, with a bit of imagination it might be adaptable for other uses.

As you can see from the pictures the best used computer heatsink to use for this is one that is round with 'wings' coming out rather than a square one. I got mine from an old Dell computer but other computers might have similar ones. Make sure that you no longer need the computer you take this from or check a computer you keep around for 'spare' parts :)

While likelihood of injury is slim, please take care when following this Instructable since heatsinks might have sharp edges that could cut.

Materials/Tools

• Old computer heatsink (as shown in picture)
• Screwdriver (flathead)
• Needle-nose pliers (optional but recommended)
• File (optional)

Without further ado lets get started.

Take the flathead screwdriver and pick a place to insert it in the old heatsink fully. Push it in the direction of the 'wings' and keep pushing until you no longer can (you might have to exert a bit of force here). Alternatively you can do this without the screwdriver but this tends to hurt! Additionally, you could also push in the opposite direction as well i.e. in both directions. Basically we want to make as much space as we can to manoeuvre.

Insert the screwdriver on the next 'wing' where you made the space, although it doesn't matter which side you choose the one in the direction of the wings might be better. Push in the opposite direction to what you pushed in step one, until you have some space to use your fingers.

Now using you fingers (thumb and index finger!) move the wing from left to right/ up and down (whichever position you have the old heatsink) - we are trying to break it off so keep doing this until it breaks off. You can also use the screwdriver for this but it might take slightly longer. NOTE: Make sure the wing is moving from the centre of the old heatsink as possible. This should provide a longer heatsink for the transistor and hopefully give better heat dissipation.

Once the wing has come off you might want to file it down a bit from where it broke off to smooth down that edge as it could be a bit sharp for when you put it on the transistor.

Use the screwdriver again to separate the two sides from each other. Carefully move one side as far as you can, possibly until it reaches 90 degrees. Any further, might risk it breaking off, if it does brake off then try again with a new one.

Use the screwdriver to bend this side round so that it forms a rough half circle but don't worry if it doesn't. We just need it bend as much as possible as shown in the picture. If the gap is big between the two sides then you might want to push the bent side in a bit leaving enough space for the transistor to fit. Actually we need slightly less space so that when we put this on the transistor we should have to apply a bit of force and making sure the bent side acts as a spring. If you find that the bend side breaks then try again with a new one i.e. repeat steps above with slight adjustments. You might need to use the pliers for this step, I used a bigger screwdriver because I found the one used in the above steps was too small to bend the side with my hands. In fact you can use anything that is round and roughly the right size if you don't have pliers.

To attach the 'new' heatsink to the transistor it is best to do this from the side and not from the top and probably before you add the transistor to you breadboard. If you find that it is loose try pushing the bent side down a bit more and if you are finding it hard putting the heat sink on the transistor try making the gap a bit bigger. Basically the gap needs to be slightly smaller than the transistor.

Thank you for checking out this Instructable (my first!) and hope you find it useful. I have not had a chance to put this to practice because my circuits at the moment consist of only LEDs and resistors :) but its should work in theory.