Question on Mounting LED's to heatsink
- Thread starter miko12
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To do drilling and tapping, pick the size screws you're going to use (I used a 4-40), then get a drill bit (#43) and tap appropriate for that size. You pretty much have to use a drill press IMO.
After you've got the holes drilled where you want them, you make threads in the hole with the tap. Using the tap is a lot like using an old-fashioned corkscrew to open a bottle of wine, but you gotta back the tap out frequently (half a turn in, then back out a quarter turn before continuing). Take your time with the tap or else it will snap and get lodged inside the heatsink, and cutting fluid (Tap Magic or perhaps WD-40) makes it a lot easier. It's super easy to get a feel for it once you've done a few, but it's tedious if you've got 50 holes to drill and tap.
If you go this route, first, see if you can find small enough nylon washers to keep the metal screws from contacting the solder pads. They don't carry them at HomeDepot or Lowes in my part of the country, so I had to go to a mom and pop hardware store to get them. surprised that those still exist, really.
After you've got the holes drilled where you want them, you make threads in the hole with the tap. Using the tap is a lot like using an old-fashioned corkscrew to open a bottle of wine, but you gotta back the tap out frequently (half a turn in, then back out a quarter turn before continuing). Take your time with the tap or else it will snap and get lodged inside the heatsink, and cutting fluid (Tap Magic or perhaps WD-40) makes it a lot easier. It's super easy to get a feel for it once you've done a few, but it's tedious if you've got 50 holes to drill and tap.
If you go this route, first, see if you can find small enough nylon washers to keep the metal screws from contacting the solder pads. They don't carry them at HomeDepot or Lowes in my part of the country, so I had to go to a mom and pop hardware store to get them. surprised that those still exist, really.
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dhutcheson
Active Member
I agree that a dirll and tap is by far the best for thermal transfer for a reference think (45 W/mK). It is also much more work when building a larger fixture I used a true thermal adhesive not the thermal grease for my build. A thermal epoxy is somewhat difficult to find and prety expensive by comparison but offers a better heat transfer than the thermal grease think (3-7 W/mk for the epoxy and 1 W/mk for the grease . Luckly I was able to use what we had remaining in a tube at work. But I only had to attach 48 Cree LEDs. I checked and the 10oz tube we used here was around $350.00 but for my project I did not need very much. However is it worth it? My next build will be drill and tap to get the approx 6 times better heat transfer to the heat sinks.
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dhutcheson
Active Member
I may be off in my understanding but without the transfer of heat from the LED to the heat sink the LED would build up so much heat it would burn up in just a few minutes depending on how hard it is being driven. I have seen some test units get so hot they desolder themselves from the star.
wld1783
Well-Known Member
+1
I did this photographing optics spread. I left a Cree XR-E on at 700mA for a few minutes and....OOPS
Even on a heatsink you have to watch thermal management. Its amazing on how quickly a fan will cool a quality heatsink.
Overall LEDs run cooler than any other lighting but they do produce a lot of heat at the source. To keep them cool you must transfer this heat to a heatsink. Lots of options but use a quality adhesive and a heatsink of appropriate mass and surface area will work with sufficient air flow.
Bill
