New VirEnce MCPCB for E17/E21/119/144/233U

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djozz
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It is a bit of a gut feeling, but in the course of testing quite a few leds and ledboards I did not notice obvious performance effects of using thick or thin solder layers under the led, so my working conclusion is that once you use a DTP board and thus the connection from the thermal pad to the core is all-metal, then the thickness of the solder layer is not the thermal bottleneck anymore. In this reasoning, using a solder type with 1.5 times the thermal conductivity of common solder will not change much either.

But again, I do not have hard data from a clean test on this.

clemence
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Well, indeed it’s time for a re-test. I’m not an expert in metallurgy science. A real life test should be enough. But this time only the new 16mm and 20mm. Are you ready Djozz? Wink

chouster
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@Barkuti,

you refer to some company selling special Indium solders. Now, do they at least give us the temperature at which the thermal conductivity is that bad as they state? Thermal conductivity of such an alloy decreases with rising temperature. If they want to provide facts, they should at least tell the whole story. A thermal conductivity without corresponding temperature is useless.

That’s at 25°C. —-> 78 W/m⋅K

That’s at 85°C. ——> 55 W/m⋅K

Fact is, 96.5Sn3.5Ag is superior to most standard solder compositions, regarding thermal conductivity. Maybe that’s why the VirEnce board tested even better as expected, maybe not that much of an impact, but certainly no disadvantage.

EDIT: Well, maybe “superior to most” isn’t the right way to say it, but it’s certainly no slouch in that regard.

chouster
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Anyways, I think we should rather be talking about the best ways to isolate the board, if we don’t go the way of having cathode across the entire housing of our lights. Aluminum nitride can be bought cheaper at some chinese suppliers at alibaba for example, but the thing is, you’d have to have two additional layers of thermal compound. With some pad or thermal foil (both insulating type of course), you wouldn’t have to use any thermal compound in between and such a foil usually comes in much thinner as a disc or sheet of ALN.

Barkuti
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That's what I was talking about earlier. An MCPCB manufacturer could assemble emitter boards with a foily layer of Aluminium Nitride as dielectric. That's it.

 

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chouster
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Yeah, or diamond PVD coating. But with this board, as it is, what would be the best, affordable way to put it to a good use? What’s the best foil for this application?

clemence
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Guys, please remember that AIN coated MCPCB can’t conform to irregular rough surface as good as soft thermal pad. This fact offset its benefit. Unless, you always have to lap your heatsink/pill to near perfect FLAT mirror like finish.

Thermal pad/adhesives is the way to go for our application and my current budget.

Clemence

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16mm board
- 1,6 – 1,8mm thick
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

20mm Board
- 1,6 – 1,8mm thick
- standard screw slots
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

Thermal pad info:
- Thermal conductivity 12 W/M.K
- Thermal resistance 0,18 C/W at 50 psi
- Compressible down to 30% original thickness at 100 psi

What about optics holes? Ledil / Carclo / Gaggione / else?
Feel free to add more suggestions

Barkuti
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More wire slots please, makes cable routing/balancing easier. Example:

 

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clemence
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Barkuti wrote:

More wire slots please, makes cable routing/balancing easier….

I have to reserve as large as possible surface area hence only critical slots/holes will be added

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clemence, I only said slots, not holes. Two holes, and 2 slots at each hole's sides. This allows routing two thinner wires per slot, resulting in a flatter profile, handy when you have a retaining ring screwing down over the board (I think Noctigons suck because of only 2 slots). Smile

 

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Question,

For the 20mm:
Do you need the screws to be completely flush with the board surface (countersunk).
OR…
Is it OK to just let the head protruded (normal M3 × 0,5 screw head)?

Thank you,
Clemence

djozz
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A 16mm board, if screw holes are added, must have them countersunk or the scews will mess with many reflectors. =less needed for 20mm

clemence
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djozz wrote:
A 16mm board, if screw holes are added, must have them countersunk or the scews will mess with many reflectors. =less needed for 20mm

No screw holes for the 16mm only the 20mm has it.
How do you usually secure the 16mm and 20mm boards?

djozz
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clemence wrote:
djozz wrote:
A 16mm board, if screw holes are added, must have them countersunk or the scews will mess with many reflectors. =less needed for 20mm

No screw holes for the 16mm only the 20mm has it.
How do you usually secure the 16mm and 20mm boards?


In many flashlights they are just pressed down by the reflector, or adhesive is used under the board, this is especially common for 16mm boards. 20mm boards are sometimes screwed down. The holes in the board may best be somewhat wider than the used screw, to have some wiggle room to center it under the reflector. Thinking of that, it may be a good idea to not make countersink holes.
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djozz wrote:
clemence wrote:
djozz wrote:
A 16mm board, if screw holes are added, must have them countersunk or the scews will mess with many reflectors. =less needed for 20mm

No screw holes for the 16mm only the 20mm has it.
How do you usually secure the 16mm and 20mm boards?


In many flashlights they are just pressed down by the reflector, or adhesive is used under the board, this is especially common for 16mm boards. 20mm boards are sometimes screwed down. The holes in the board may best be somewhat wider than the used screw, to have some wiggle room to center it under the reflector. Thinking of that, it may be a good idea to not make countersink holes.

I thought so too. With countersunk holes, the free play is limited. It’s also easier to isolate the screws from the board (CDTP limitation).
You know what Djozz? “CDTP” is popularized by you! You were the first to use that term, AFAIK Wink

The_Driver
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Screws in general might be a problem. They might create an electrical connection between mpcb and the heatsink.

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The_Driver wrote:
Screws in general might be a problem. They might create an electrical connection between mpcb and the heatsink.

No if you use high strength plastic screws Wink

Wieselflinkpro
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clemence wrote:
16mm board
- 1,6 – 1,8mm thick
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

20mm Board
- 1,6 – 1,8mm thick
- standard screw slots
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

Thermal pad info:
- Thermal conductivity 12 W/M.K
- Thermal resistance 0,18 C/W at 50 psi
- Compressible down to 30% original thickness at 100 psi

What about optics holes? Ledil / Carclo / Gaggione / else?
Feel free to add more suggestions

Are they still under development?
When will them be sold?
What is the expected price?

djozz
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clemence wrote:
The_Driver wrote:
Screws in general might be a problem. They might create an electrical connection between mpcb and the heatsink.

No if you use high strength plastic screws Wink


and not if there is a copper trace clear-out of 2mm around the holes so the screw head can not get in contact with the electrical circuitry
clemence
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Wieselflinkpro wrote:
clemence wrote:
16mm board
- 1,6 – 1,8mm thick
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

20mm Board
- 1,6 – 1,8mm thick
- standard screw slots
- 2 × 3mm dia. wire slots
- with/without thermal pad (0,5/1 mm thick)

Thermal pad info:
- Thermal conductivity 12 W/M.K
- Thermal resistance 0,18 C/W at 50 psi
- Compressible down to 30% original thickness at 100 psi

What about optics holes? Ledil / Carclo / Gaggione / else?
Feel free to add more suggestions

Are they still under development?
When will them be sold?
What is the expected price?

- The (three) designs are 90% ready for upload, only holes/slots placement left. I also design another aluminum square DTP 30mm x 25mm linear 3535 single/triple config exclusively for use with LEDIL STRADA and SHELLY
- ASAP in early February. But please, please, don’t take it tightly. I’ve been trying my best to be a faster designer/provider, yet still not fast enough for BLF.
- Will TRY to bring them here at approximately USD 3 – 4/pcs

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C'mon! A fiber washer is all you need for those metal screws.

 

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clemence
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Barkuti wrote:

C’mon! A fiber washer is all you need for those metal screws.


 


Cheers Party

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 × 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.

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clemence wrote:
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 × 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

clemence
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Cula wrote:
clemence wrote:
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 × 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

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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. Wink

Thank you,
- Clemence

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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)

clemence
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djozz wrote:
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 Wink

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chouster wrote:
Well, I think the opposite is the case. That stuff is for special applications. For normal application, just go with normal solder paste. Or go with SnAg (96.5/3.5) if you really want good thermal properties. 221°C reflow temperature shouldn’t be a problem at all and that stuff is quite affordable.

!{width:60%}http://s3.electronics-cooling.com/legacy_images/2006/08/2006_August_Tech...!

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

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