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  • Milling down a copper heatsink

    So I upgraded the processor in my mac mini from a core duo 1.66ghz to a Core2Duo 2.0ghz. Nice speed boost. Only problem is cooling. At full load the processor core gets to about 90 to 95 degrees C. The CPU is rated to ran up to 100C with throttling at 105C (Laptop class processor. Exposed die.) I would rather it be a little cooler. Once its starts warming up and the ambient goes up I am a little worried.

    The heatsink has its own temp sensor on it and at 90C die temp the heat sink is only 60C. Not real good thermal transfer go on here. I tried a couple different heat sink compounds and no good. I milled the anodizing off the back of the heatsink flat and polished and that really didnt help either.

    So my next idea is to use a low profile solid copper heatsink from something like a 1U server. Only problem is the size. I need to cut it down and drill holes for mounts. Any ideas on cutting it down without tearing up the fins? I was thinking about one of the low melting point alloys. Fill the fins and then mill, drill, and counterbore.

    Will the alloy wet the copper? Maybe another idea?

  • #2
    How much do you have to remove--ie. would a belt sander be the simple solution?

    If you do need to mill it, I think I would try a sharp end mill. I have read that milk is a good lube for copper. If the stuff cuts, then there should be no need to fill between the fins although you would have some burrs to clean up.

    Paul
    Paul Carpenter
    Mapleton, IL

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    • #3
      If you have to pack the fins, do so with brown sugar. Dissolves away, and it can be tamped into a ridgid block.

      Dave

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      • #4
        How much I remove just depends on the closest size heat sink I can find, which I am still looking for. I have found a couple close. withing a half inch or so. But still a bit tall.

        I cant imagine packed brown sugar being solid enough to keep the fins from bending.

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        • #5
          screw the heatsink - put in an intercooler

          Some of the guys here at school (being a science and tech school with lots of ... well nerdy individuals) have water cooled computers for - yep you guessed it - gaming!

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          • #6
            Aww, heck I will just go with LN2 cooling...

            We've seen some overclockers go to pretty great lengths to keep those chips cool while they crank up the GHz, but Foxconn's demonstration at the company's CeBIT booth is really a sight to behold.


            But I really would like to keep it in the case!

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            • #7
              Here are a coupe of ideas. Mill off the thick portion, and cut the fins with a pair os snips, or if you have room just leave the fins hang over the edge.

              Freeze the while thing in a block of ice. Easy Cheap, and should stay frozen long enough for you to mill it.

              The other option is to keep the heat sink you have and add a fan if you have room. I know there is not much room in the mini, I dislike this option as I would not want to add noise to one of my mac's.

              Dale

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              • #8
                There are waxes that come in granular form to be melted for encapsulating things like heat sinks for machining.

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                • #9
                  If you wanted to go with water cooling, you could run a line from the drinking water stand, then combine your cooling project into a coffee maker. 30 minutes of computing gives you a cup of coffee.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    Originally posted by DR
                    There are waxes that come in granular form to be melted for encapsulating things like heat sinks for machining.

                    Macona I have done this exact thing a bunch of times for one of my customers, it works pretty good and I would say the hardest part of the whole operation is getting the wax back off of the heatsink, boiling it in water seemed to work pretty well.


                    I have also done it without the wax using a big diameter slitting saw and basically cutting one fin off at a time from the side, the fins were relatively thick though and were aluminum not copper.

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                    • #11
                      Are you using heat sink compound this increases the thermal transfer between the component and the heat sink.

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                      • #12
                        Have any diamond dust laying around

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                        • #13
                          The slickest heatsinks are heat pipes.

                          So long as you do not exceed the max power rating, you KNOW exactly how hot the contact surface will get, because it is related directly to the boiling temp of the working fluid.

                          Naturally, you have to find somewhere to dump the heat, but then you KNOW exactly what temp the fins can get to........... and the power, so you can fairly easily calculate the airflow required.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

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                          • #14
                            Low Melting Point Alloys

                            I use Cerrobend, one of the low melting alloys, all the time with brass tubing. If you soak the park in oil before pouring the alloy around it, it won't tin the part. I just use 30w from yonder AutoZone because it coats and stays coated. I like to drain the oil for a half hour or so, but the Cerro displaces any remaining puddles of oil if you don't want to wait.

                            Stuart
                            Stuart de Haro

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                            • #15
                              Sorry, no sinking advice... Just curious. Why so much heat.. My lil laptop here has a 2.0 Duo Core and it doesnt get hot at all. And it has a variable fan set up and never kicks into overdrive.. Are there different processors? This one is a T2500 I guess.. Maybe not the same.. JR

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