Hi all!
I’m a complete newbie in this space - so apologies if this is a daft question. I’m trying to build a powerful flashlight with a diameter of a pen (approx 5-7mm). The LED would be a 3-5W 3mmx3mm. I’m wondering what the smallest MCPCB for this purpose is. I can’t find anything smaller than 10mm. I’m not worried about the heat transfer/dissipation at the moment; I’m just trying to see if there are MCPCB small enough in the first place. Thank you for any advice!
You could always cut / dremel the pcb to make it smaller. However the optic efficiency will be a bigger problem. For such a small frontal opening, it’s hard to get much light out. No space for a reflector. Maybe a small TIR, and definitely not a convex lens as it is the most inefficient way to project light forward.
You could get something custom made, maybe by somewhere like JLPCB? This is likely to be a lower performance aluminium one though, I would agree with FunkyRider and suggest sanding down a larger high performance copper one. It’s pretty easy to do you just have to check for shorts
Check these: (links are from mobile app)
5,88€ | KDLITKER 3535-10 10mm DTP Copper MCPCB for 3535 LED Flashlight DIY LED PCB Star
and these:
1,53€ | 3535 UV LED Copper Base Plate Copper Substrate PCB for 395nm 405nm UV LED Spot Light Source Flashlight
That smallest ones I’ve used have been 8mm when swapping emitters in penlights. Something like 50 stücke Aluminium LED PCB Board 20mm 16mm 14mm 12mm 10mm 8mm Für Cree XPE XP-E XTE XT-E XPG XP-G 3535 LED Licht - AliExpress 39 (though there are quite a few similar sellers on AE, so you’d want to look around for the best price/reviews).
Thank you all! You’ve been most helpful. I think I will buy some 8mm ones and sand them down. Thanks again 
The smallest MCPCB I’ve seen is this one, from thefreeman’s modified Zebralight. It’s for a Nichia B35A, so not what you need for your project.
