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

Strange, it’s working now :stuck_out_tongue:

It works for me ;).
Generally this is a great idea! These will be much more practical compared to your first design. When can you have them ready?

Scheduled for January….
My first design wasn’t intended for flashlight, it’s for my personal specific use. This was a perfect size/shape for prototyping many general lightings with 144A/119 series.

I’m in the group buy for 2 of your “universal” boards and I’ll honor that commitment, but I’m definitely interested in some of these boards too. 16s and 20s seem like a great start.

Very clever design, Clemence! By the way, it’s really great to have you amongst us!

=)
Not possible without BLF & TLF supports

Let’s not hope much. CDTP design is highly surface area dependent, smaller surface area = higher Tj. That means bigger board will be better. But this new design utilizing maximum possible surface area possible for both anode/cathode. I also try to reduce current heating as much as possible. Using dielectric with as high as possible thermal conductivity I could get. I predict it would be a bit less cooler than the standard VirEnce S30 but in smaller 16mm package.

Fellows, you're venturing into new territory here with a cathode direct thermal path board.

The lack of electric isolation is going to be a real hurdle, I think. Something which could be fixed with a thin layer of some über-high conductivity material. If the cathode track pad is reasonably maximized in surface and you can get some thin layer of über-conductive electrical isolator below, the problem is solved, and the industry moves forward.

Pretty sure there's someone around there who can offer aluminium nitride/beryllium oxide sheet/foil at much less than those prices, clemence. Hell, you could get diamond foil for a lower quote, LoL!

Why don't you ask for some help from a specialized manufacturer? More or less recently some Shenzen Kerui Electronic Industry representative has been around here promoting their products. More info: https://www.linkedin.com/company/shezhen-kerui-electronic-industry-co-ltd-

Cheers ^:)

It’s indeed universal. I use some for my desk and workshop light with assymetric TIR optics. Plan to use it for my parking area lighting with Ledil Jenny CY optics.

Thanks Bark,
Even without super material CDTP can be designed to surpass neutral DTP approach as long as you have the required surface area. The idea is to lower the heat potential difference (does anyone know shorter terms for this?) thus less thermal resistance. This is pretty much why Nichia still manufacture 2 pads design.
In theory two pads design can achieve lower Tj compared to three pads design (ignoring the surface area required) since copper used in cathode/anode has much better thermal conductance than the dielectric material commonly used in LED. Combined together with very high conductance and thin solder joint such as Indium solder, the result should be even better.

Upstream just at the heat source, heat flux intensity is higher that downstream where the surface area is cooler and larger.

For example: If a 119 has to pass 10 watt of power through two tiny solder pads. The heat intensity is roughly 10 watt/11,9 mm^2 (0,84 W/mm^2). After heat flux passing the solder pads, the intensity lowers down to 10 watt/201 mm^2 (0,05 W/mm^2) using a circular 16mm MCPCB.

My simple logics:

- Upstream:
common Sn60Pb40 thermal conductance ~50 W/M.K
heat intensity ~ 0,84 W/mm^2

- Downstream
Thermal pad material with X thermal conductance
heat intensity ~0,05 W/mm^2
To get the same state, thus X= ~2,9 W/M.K

I still don’t have any valid data to stand up for this one yet. I rather make some and then test it based on that logic. The universal VirEnce board test result was higher than expected. And I think (emphasizing the: I think), solder choice is one of the most important thing in CDTP design, it’s where the bottleneck occurs (not downstream at the MCPCB’s thermal pad). As long as we use MCPCB with surface area reasonably LARGER than the footprint of the LED’s solder pads.

I’m using Sn96,5Ag3Cu0,5 for most of my newer project now. It’s harder on the boards (218C liquidus) than 60/40 and requires extra effort to get a good reflowed boards. The thermal conductance is ~58-60 W/M.K.
I have a spool of SnxxAgxx (lost the label) solder wire rated at 70W/M.K but requires 240C to a flowable liquidus. Much harder and stronger joint very useful for aluminum soldering.

The larger the MCPCB surface/mating area to the heatsink, the less sophisticated the thermal pad required.

That’s the ideas behind my idea….

Indalloy #290, 97In3Ag, is eutectic, melts at 143°C/289.4°F, and provides a 73W/m×K thermal conductivity figure. Sources:

Cheers ^:)

Very nice, must be expensive though

“melts at 143°C”

would be too low for my liking

Best thermal protection….when it gets hot the LED would just dropping run off the board :smiley:
Good for “normal” applications, not for you Matthias

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.

Yup, for example soldering over soldered joint. I have many PVC backed waterproof cable connector joiner with very low melting temp solder. Just apply moderate heat using heat gun.
Hey, I think that Sn96,5Ag3,5 is very similar to my spool. Mine rated at 221C but in practice I had to set my hotplate to 240C for it to reflow properly. That’s the solder wire I used when I sent Djozz the samples. 240C reflow temp really turned those white S30 VirEnce board dark yellow. I also used wrong flux to worsen the looks.

chouster, the thermal conductivity figure you provide for Sn96.5Ag3.5 is not supported by the guys at Indium Corporation. They claim a 33W/m×K for it (Indalloy #121). Check it out in the table link above, and here: Alloy Thermal Conductivity @ Indium Corporation.

Cheers ^:)

@ clemence

But I think you made a very valid point. It’s the solder joint that has to pull away the heat from the LED at first and using Sn96,5Ag3,5 instead of standard Sn63Pb37 should give an increase of 56% in thermal conductivity. Just use solder paste with less agressive flux.

clemence, you slipped in while I was still editing my post.

So, you reflowed those Nichias with 96.5Sn3.5Ag? Ooops! You may had created a heat transfer bottleneck, so Djozz's tests may not resemble the results most of us would get with Sn63Pb37/Sn60Pb40/Sn99.3Cu0.7…
Time for a little retest?

Cheers ^:)

That was accidental….
I dipped the solder wire to a super aggressive ALUMINUM flux. If you see those boards in Maukka’s spectrum test thread, some were extremely “burnt” by the flux.

I don’t know if the move to SA35 (Sn96,5Sn3,5) would really make measurable end result difference (higher lumen) with thin solder line. With proper soldering (very thin bond line) the difference would be minimal. In the case of thicker joint then solder choice should be more critical.
I usually just put a small blob of solder paste and heat until the LED soldered, then remove excess solder using fluxed solder wick to create the thinnest possible joint. LED pre-centering is critical with this method. Less solder between LED and solder pads give less self centering effect.