Over the years I’ve piled up a lot of footprints in FreePCB…many are just to fit the current project, others may be the only part I ever used from a particular company. Microchip Technologies fits into neither of these categories; I’ve used hundreds of different parts from them over the years. To make things easier, I always make the base package footprint for a part and then make another copy of it with the pins labeled. I recently noticed that I had almost all of the base footprints they have. They offer a PDF that contains every device package they make, so I downloaded it and went looking for the ones I missed. I made all of the ones I missed, then put the part footprints in order by package type (DIP, QFN, etc), followed by pin count. I’m sharing these to save everyone else time. The link (click the words “Lots of FreePCB Footprints” above this post) is a ZIP file. Extract the two files within it to [FREEPCB DIRECTORY]\lib and restart FreePCB, you will now have all of these footprints. Disclaimer: Some of the footprints have never been tested, I did my best with the information available, but many of the SMD parts don’t even have footprint designs in the PDF from Microchip Technologies, so without actually making boards and buying chips I cannot confirm they will work. I am not responsible for any flaws in the boards you make, or for anything you do with these.
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If your system is overheating in spite of the fan turning fast, this is one area you should look at. Over time, the heatsink bases and/or the chip tops can warp slightly, causing poor thermal transfer…and without that, it does not matter how fast the fan spins. The system shown is a 40GB model. As you can see, one of the chips is not touching the heatsink except at the very edges, and thus, the temperature is very high even with the fan at maximum speed and the system at an idle. The other chip has better contact, although it isn’t quite perfect, there was enough contact to keep the chip cool.
To fix this, I simply removed both heatsinks and lapped them. This is a process of sanding the base smooth by rubbing it back and forth across a piece of low-grit sandpaper that is placed on a flat surface. Once the low-grit has leveled out the heatsink, you switch to 600 grit to remove the scratches from the low grit, and then you use 1000-2000 grit to put a mirror finish on it. In this particular model, there were raised edges on one of the heatsinks…I used a Dremel Trio to remove those before doing the low-grit sanding (NOTE: this moved the screw stops, so it is almost like doing the washer trick, except without washers). Once both heatsinks were flat and smooth, I put it all back together with cheap white thermal compound, then disassembled to check the contact squares again. While they still were not perfect, they were more than good enough. If they had still been bad, it would have had to sand the chip tops…this is a VERY time consuming process that I am very happy to have avoided. Last, I cleaned off the crummy white stuff and put a super-thin but even layer of Arctic Silver 5 on both chip tops, screwed it all back together, and that was that…