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MOSFET mod cooling via soldering: the safe way

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Aeon Flux

I NEED TO CONTACT SILVERSINKSAM, AS I HAVE A OUTST
Joined
Aug 12, 2003
EDIT: Sorry about that *NADS* typo. Quick typing leads to a lot of typos. It is now fixed.

I was reading over a post and someone said it was completly unsafe to solder plating to your mosfets to cool them. Wel all know placing a heatsink over the silicone of the mosfets will dissipate some heat but is not the most effeciant way of doing it. Some people have tried soldering copper plate tabs to their mosfets from the metal tab to help dissipate heat. This works much better because it attaches directly to the metal from inside the transistor. People are skiddish of doing this though because of dangerous it might be. I am going to write a quick write up on how to do this safely.

First off for my background expereince. I have taken 3 years of elctronics in school. My background in electronics persists of; circuit board layout, circuit board design, building circuit boards, and electrnoic theory.

I assure you with this article if followed right will allow you to safely solder plates to your MOSFETS to cool them. As always it has to be said, I take no responsibilty of damage done to your board because I can not control your hands, body, etc.. and can not be there to make sure it is done right. But dont let this dissuade you if you really want to do this. It's very safe.

What you will need:
Solder pencil-a small 10 dollar one will work great from radio shack. Make it a lower wattage pencil.

Solder- make it a 50/50 solder. Otherwise half tin, half flux. Can be bought at radio shack for a couple dollars.

Small alligator clip and wire- Again can be bought at radio shack for a couple dollars. Make it a small alligator clip with as small teeth as you can find.

A very bright light and good working space- you can work that out on your own.

Small needle nose pliars-look in your tool box. If worst comes to worst again hit up radio shack.

And last but not least your copper plating- can be bought at a hardware store for a couple dollars. get 1/16 mm think or half mm thick. This will let you cut it with normal scissors and bend it with a ruler and your hands.

Lets get this done now.

First remove the motherboard from the case and put it in a place that you can work in easily and have a very bright light near by so you can easily see. Use all usually precautions when removing and placing your motherboard somewhere other then your computer case. PLEASE READ ALL OTHER INSTRUCTIONS BEFORE ATTEMPTING THIS.

First step: You need to make a heatsink. Remember that alligator clip and wire you bought? Solder that wire to the back of the alligator clip. That simple. You now have a heatsink for any time you decide to solder something. Make the wire a few feet long. This will leave enough room for heat to store. The wire does not need to be desheathed. Actually for where we're using it at the moment I reccomend leaving the plastic on the wire as to not short anything out by mistake. Not takeing the plastic off wont hurt it any.

Step 2: You need to locate the MOSFETS. For purposes of experience I am going to assume you know what they are and what they look like. If you do not know either of these you should not be doing this. Locate someone else that understands this write up completly and have them do this for you. It is better to have someone with some experience do this or has complete confidence in themselves.

Step 3: You need to heat up the mosfets and remove the backing from the motherboard. The Mosfets should be soldered down to a little metal tab underneath of them on the motherboard. PLEASE READ EVERY STEP FROM HERE ON OUT BEFORE ATTEMPTING TO GO ANY FURTHER. To do this hook the alligator clip the best you can to the metal tab on the MOSFET. make sure it is secure. Also you want the alligator clip as close to the silicone casing as possible on the MOSFET. Now with your new soldering pencil heat up that metal tab on the mosfet. This should only take a few seconds. After it is heated up use the needle nose pliars to lift that tab away from the motherboard. You only to need to pull the tab a few mm away from the motherboard. Just enough to be able to slip the copper underneath of it. From here on out keep the heatsink on the MOSFET until the process is complete or otherwise noted. And also again make sure the heatsink is as close to the silicone as possible. This may be a good time to reseat the heatsink closer and more secure if you need too.

Step 4: Make the copper tab. You need to cut out a copper tab the width of the MOSFET and as long as you would like it. Just use a ruler and a pencil and draw out the design on the copper and after finished cut it out with some sharp scissors. If you are not sure what dimensions to use just use these. Make a rectangle approximatly 7mm but 25mm. After cutting the copper with scissors you may notice it is a little bent. Use a peice of glass or something hard and flat and place that over the copper on a table. Now find a big heavy book or similiar and press down on the copper to flaten back out again. After the copper is cut measure about 7mm again up the tab and mark it. Use a ruler and bend the copper at that mark 90 deggrees. After you are done you should have a piece of copper that looks like a small L.

Step 5: Now Its time to attach the copper. Do this step carefully. First as an outline as what will go on in this step. You will be heating up both the MOSFET and the copper. You will be soldering the copper to the MOSFET. Pay attention to the heating part. Also AGAIN READ THIS STEP FIRST AGAIN BEFORE COMPLETING AND MEMORIZE IT EXACTLY AS YOU WILL NOT HAVE TO READ THIS WHILE DOING THIS STEP. Now that you have the MOSFET pulled up and copper cut it is time to attach it to the MOSFET. First you need to heat up the copper. Hold the copper with the pliars and touch the soldering pencil to the small bent tab on the copper. You will need to heat it for a few good minutes and get it nice and hot. After this is complete melt some solder on to that little tab. Now quickly put that put that small copper tab underneath the metal tab on the mosfet. The long part of the copper should be sticking up above the MOSFET. now you will have to squeeze the copper and the mosfet together with the pliars and hold it. Heat up the metal tab on the MOSFET for a good 30 seconds to a minute. It is absoultly nessecary to heat up both so the solder will stick to the metal. Solder WILL NOT stick to cold metal. It must be hot. After heating up the metal tab and after it feels very warm take the solder pencil away from the MOSFET. Hold the copper and the MOSFET together until they are both cool. This may take some time. As a reccmondation I would not blow or try and rapidly cool either. It is better to let them cool slowly. Do not worry about the MOSFET as the heatsink is keeping the transistor cool. And as for surrounding components they may feel warm or hot but because they did not have direct contact with the soldering pencil they did not absorb anough heat to damage them. If you do not feel safe about not protecting them dont be afraid to make another heatsink and attach them to the surrounding components. After it is cool and down to room tempature you can let go of the MOSFET slowly and remove the heatsink. Push the mosfet back down against the motherboard with a gentle touch of your finger.
Repeat this process for all the MOSFETS until completed.

And congrats. You have just helped cool your mosfets. You can seat a heatsink on top of the MOSFETS and solder the copper tabs to that heatsink to help further cool it. Follow the same basic steps to solder the tabs to the heatsink and enjoy. If not just place a fan near those metal tabs to blow air on them. That will be more then enough. If you have any questions about this PM me or email, [email protected]. Most of all enjoy and besafe. DONT FORGET SAFETY GOGGLES!!!
 
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