No, plain washer still expose the screw thread to possibly contact to the MCPCB body
You have to at least use waisted/flanged washer to insulate both the screw head and the thread body, otherwise you’ll screw it. But flanged washer will need bigger holes. Normal clearance fit for M3 x 0,5 is 3,2mm. With flanged washer you have to open up to 3,8-4mm minimum hole diameter.
With plastic screw you can save the precious surface area and simplify installation. Plastic screw comes in wide variety of materials and designs.
Hi Clemence,
Got a link for those hi strength plastic screws?
Thanks
http://www.extreme-bolt.com/applications-high-temperature.html
https://www.plasticnutsandbolts.com/materialsz.html
https://solidspot.com/engineering_plastic_screws.html
PEEK is my preferred material choice
Please review these drafts.
Decided to follow standard “star” shape, though mine is rounded to make centering easier if necessary.
I still haven’t heard about optic holes for the 20mm. Should I just leave it blank? So everyone can just drill themselves?
I prefer to leave it blank, since in this CDTP design, anode/cathode surface area is of high importance.
@Barkuti: Dude, you get those slots. 
Thank you,
- Clemence
So the +trace is one large pour over the entire surface with just a clearing for the -pad which is a small connection the size of the solder pad going down to the core?
(I’m not familiar with single led optics so I can’t advice on the holes)
That, I can’t tell you yet
Ever wondering why this budget friendly Sn96,5Ag3,5 with superior thermal conductivity 78 W/M.K is not so popular?
Here’s the answer: http://www.psma.com/ul_files/forums/leadfree/aim_lead_free_guide.pdf
The short answer is it has somewhat troublesome wetting ability. Not a good thing for automated soldering. But for us who really likes to spend hours just to get perfect reflow, this should not be a major problem. The jump from ~50 W/M.K to 78 W/M.K is indeed worth the hassles.
- Clemence
Eye candy
Nice render, time for and avatar picture change?
Ah, Forgot that. Thanks Jos
The PEEK screw and 12 W/M.K thermal pad samples are on their way to my workshop……
Will be a great chrismast gift!
- Clemence
Any updates on the PCBs and screws?
The screw samples are still on holiday trip to my country. Just received the expensive thermal pad samples this afternoon.
12 W/M.K 0,5mm thick, not bad eh?
0.5mm thick copper tracing??
OMD, I wish… 
No, it’s the thermal pads to insulate the MCPCB from the base
Ah, completely mistunderstood it then, or it was wishful thinking 
FYI,the next VirEnce will be 3 oz thick minimum.
I’m an SI person, had to look that up: 3 oz = 0.1mm sounds good
I could not find back what the copper thickness of my 119 boards are, but a common thickness for Kerui seems 0.036mm, that makes your tracing 3 times as thick.
I’m an SI person too. It’s just Oz is a universal unit used in many copper tracing industries. Yes, It was hard to convince them to make 3 oz for me. I had to insist on it (at additional charge). I haven’t place the order yet, even though I made them busy for weeks
They have one of the best customer service in the industry.
Great, thanks!
When will you get samples of the PCBs?