Laser cuttable, thermally conductive, electrically non-conductive material? - Page 1
Forum section: electronics / projects

author: Corporate666
author_rank: Unknown
timestamp: October 02, 2017, 10:36:08 pm
content: Title pretty much says it. I have a strangely shaped LED board that goes into an aluminum housing for heat dissipation, but the board is *really* tightly routed and has traces on the back side as well as vias. So I need something to isolate the board before it's bolted onto the aluminum housing.I am open to using some sort of adhesive, but it seems like a thin sheet of material I can laser cut would be better. Any suggestions?

author: jbb
author_rank: Super Contributor
timestamp: October 02, 2017, 10:39:06 pm
content: If all else fails you can get a knife cutting tool made to stamp 'em out. What's your volume?

author: Corporate666
author_rank: Unknown
timestamp: October 02, 2017, 10:49:01 pm
content: Quote from: jbb on October 02, 2017, 10:39:06 pmWell, right now this is a short run of just 30 parts for a client who wanted something special for his project. The only way to make it commercially viable was for us to reuse much of the design in a "sister" product that we'll be releasing ourselves... but even if that does well, we'd be looking at 3,000 units per year, so volume will be low.I have a laser cutter, however, so I was hoping there is some material that I can just buy in a sheet form and cut - would would perfect for this project and would be useful for lots of other prototypes and short-run stuff we make too.

author: edavid
author_rank: Super Contributor
timestamp: October 02, 2017, 10:57:23 pm
content: I usually see Bergquist Gap-Pad used for this, but I don't know if you can laser cut it.

author: Corporate666
author_rank: Unknown
timestamp: October 02, 2017, 11:05:16 pm
content: I can try calling Bergquist tomorrow... the other issue is that the customer needs the assembled unit in their hands on Friday, so it would need to be something I can order from somewhere like Digikey, McMaster or Amazon and have it here within a couple of days.What about liquid materials? There are thermally conductive epoxies, but the difficulty there would be either applying it to the PCB and letting it dry and trying to get a thin and flat coating so as to minimize thermal insulation, or I could apply it and then put the PCB into the housing, with the difficulty being ensuring that none of the vias have made contact with the housing and that it stays that way until it's cured.The PCB is a donut shape and there are 4 mounting screws... maybe I could put very thin washers under the PCB to provide clearance and use thermal epoxy to provide heat transfer?The finished unit will see quite a lot of vibration too, so I don't want to rely on traditional thermal compound alone to provide electrical insulation.

author: jbb
author_rank: Super Contributor
timestamp: October 02, 2017, 11:42:23 pm
content: If you need 30 pieces by Friday, I suggest a gap pad (eg Bergquist) + a sharp scalpel.You can print out the required outline at 1:1 scale for use as a template. CHECK THE SCALING because some print drivers have difficulty with this...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 03, 2017, 12:18:54 am
content: Waterjet can cut soft materials, but for 30x, scalpel should do it fine. Or a good pair of scissors.Alternatively kapton tape on the PCB and fill the gap with heatsink goop

author: ajb
author_rank: Super Contributor
timestamp: October 03, 2017, 04:39:17 am
content: Laird T-gard K52. It's a kapton film coated on both sides with a ceramic PCM. Available with base film thicknesses of 1-3mil. We laser cut it all the time for lining heatspreaders, works great, and available in 11"x18" sheets from Digikey/Mouser.Although I've also seen reputable manufactures just use regular kapton film slathered with silicone grease on both sides, so...If you go the thermal epoxy route, a good way to get a reliable film thickness is to lay a few strands of suitable-thickness plastic filament in the joint, and then compress it. The diameter of the filaments will set the film thickness.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 03, 2017, 07:42:39 am
content: just silicon pads to where they need to

author: FermiLab
author_rank: Newbie
timestamp: October 03, 2017, 12:22:35 pm
content: 3M makes thermally conductive but electrically insulating tapes that sound like they would work for you. I can't remember the number of it right now. Message me if you're interested and I'll dig into it more.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 03, 2017, 12:38:49 pm
content: I'm a fan of T-Global thermal gap filler pads. They make a whole range of them in different thicknesses and hardnesses, with and without adhesive.Try these for starters:https://www.digikey.co.uk/en/product-highlight/t/t-global/l37-3s-ultra-soft-gap-filler

author: DTJ
author_rank: Super Contributor
timestamp: October 08, 2017, 02:50:09 am
content: Have a look at Electrolube TPM550 or TPM350.I just read an advertisement for it.It seems to be the same stuff as the bergquist phase change pad material but it's supplied in a viscous liquid form.You pour it in where you want it and the solvent evaporates leaving a custom shaped thermal transfer pad.It actually seems like pretty neat stuff:https://www.electrolube.com/products/thermal-management/tpm550/thermal_phase_change/