Best practices for high performance mpcbs? Solder and springs?

5 posts / 0 new
Last post
PyriteParachute
Offline
Last seen: 4 days 5 hours ago
Joined: 07/28/2021 - 00:29
Posts: 51
Location: Southwest USA
Best practices for high performance mpcbs? Solder and springs?

Hey everyone,

I’m putting things together for a Convoy s2+ or Jaxman E2L triple Optisolis build.

Both mPCBs found here claim better thermal performance due to the AlN substrate. Clemence also talks about the improved dielectric thermal conductivity,

[quad] https://www.eurekatronix.com/product-page/vr21p4-1
[triple] https://asflashlights.com/home/134-sinkpad-copper-mcpcb-for-cree-xm-l2-x...

I don’t want to hobble the performance of these boards with a poor component choice elsewhere. A mntnelectronics page says “If you are running more than a 3.4A driver, you must bypass the tailcap switch spring”, and apparently there are thicker springs used on higher amp Convoy models. I’ll be running 2.5-2.8 amps. Do I need to worry about switching out or modifying the stock spring?

Clemence’s page also recommends leaded solder paste or Indium wire. Would lead-free paste be worse electrically, or just harder to apply?

Any other things I should think about when putting this together?

Lightbringer
Lightbringer's picture
Offline
Last seen: 4 hours 35 min ago
Joined: 08/30/2016 - 14:12
Posts: 15866
Location: nyc

Won’t make much of a difference.

Great light, but it’s a tubelight with like zero fins or similar cooling area. It’ll be like holding the wrong end of a curling iron in your hand regardless, if you let it cook too high for too long.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

thefreeman
thefreeman's picture
Offline
Last seen: 26 min 26 sec ago
Joined: 01/06/2020 - 09:56
Posts: 962
Location: France

A good dielectric layer as a big inpact on the performance on LEDs with no neutral thermal pad (no DTP).

Long steel springs can have a quite high resistance, the highest I’ve measured was in a H600 at 50mΩ and it doesn’t compress a lot so the spires don’t touch, at 3.5A that’s 0.175V lost in the spring and 0.6W, quite significant.

BeCu springs have much better conductivity.
Bypassing a spring reduces it to like 1mΩ.

Clemence did some test with indium
https://budgetlightforum.com/comment/1465850#comment-1465850
https://budgetlightforum.com/comment/1461666#comment-1461666

No or minimal difference, some of which could be attributed to LED variation.
Plus indium is uber expensive and a pain to work with, terrible flow/wetting, probably better with rosin activated or acid flux, which need to be thoroughly cleaned, Clemence uses the later and clean his soldered MCPCBs in a hot water ultrasonic bath…

No relevant difference in electrical conductivity between Lead free (like SAC305) and SnPb.
The excellent wetting of SnPb and the lower melting temperature makes it easier to work with.

max
max's picture
Online
Last seen: 6 min 7 sec ago
Joined: 02/17/2014 - 18:55
Posts: 447
Location: Austin, TX

Here's a couple of tips -  I believe 20mm is the largest that will fit so the 21mm in one of your links above may not work without some filing. Heck I've even had to file, a little, on a 20mm to get it to slide down the tube of a S2+ before.

Don't worry about changing out the tail spring, unless you just really want to, just solder in a bypass wire. Use 22 AWG and go from the bottom of the spring to the top. You can see pics of them installed on Simon's (Convoy) store's website for several of his lights. You can probably find youtube videos showing this done. It's quick and easy to do. Most of us are probably using good hi temp Tenergy wire. Here's one place to buy it:  https://www.mtnelectronics.com/index.php?route=product/product&path=25_71&product_id=68

For health reasons i use lead free solder (some jewelers will refer to it as 'silver solder'). The stuff i use flows better, for me, than a lot of standard leaded solder. It's more expensive than cheapo typical lead/tin solder but I'm not going to breathe those lead fumes. Here is a link to the solder i use:  Kester lead free solder

Also, if I'm re-flowing LED's onto a MCPCB, or chips on a driver for that matter, i use good quality solder paste. Again, i don't cheap out here either. I have had good luck with a silver bearing solder paste called "solder-it" that you can buy online or at your local Home Depot/Lowes type store.

As with all things YMMV, I'm just trying to share some of my experiences.

 

 

 

 

 max

flightless22
flightless22's picture
Offline
Last seen: 16 hours 19 min ago
Joined: 11/19/2018 - 12:07
Posts: 552
Location: California

Max, I have bad news for you, Simon uses leaded solder for his lights. Glasses

The fumes are from the flux and not from the lead in the solder.

I upgraded my CPU fan fume exactor to inline duct fan and used cat litter container as the base Facepalm

Some parts
Cat litter Base – $16:
Inline Duct – $11.99:
Vent hose – $7.53:
On / Off Switch – $9.99:
Carbon filter – $10.99: