Best MCPCB and solder

likevvii · 2019-08-15T09:48:31.000Z

Hello,
I am about to purchase some solder WIRE and need some advice on what is the best solder to use for thermal conductivity.
I want to use Sn/Ag (96.5/3.5) Are there even more superior options? The melting temp needs to be under 250C because the sensitive Nichia LED will not do too well when overheated.
How about solder pastes? I prefer using wire because I like to tin both surfaces and then squish the solder out by squishing the LED.

My next question is which MCPCB has the highest performance? I will mainly be using 3x or 1x LED, 20mm board configurations.
Noctigon
LED4POWER
mtnElectronics
etc

While on this topic, what type of flux should I use? I don’t have an ultrasonic cleaner so I only got alcohol.
Kester 186
Kester 951
etc

The_Driver1 · 2019-08-15T13:33:20.000Z

Pure Indium is the best in terms of heat conductance. It's not very strong though so it makes sense to only use it for the center contact of an LED.

The SnAg value in that table is probably not correct, we discussed it elsewhere here in the forum.

You can use any copper dtp pcb for best performance. They are all basically the same.

clemence · 2019-08-15T10:33:22.000Z

[Reference] Physical and Mechanical Properties of Solder Alloys Flashlight Modding and DIY Parts

Physical and Mechanical Properties of Solder Alloys Original source: http://alasir.com/reference/solder_alloys/ Solder Alloy Melting Point, °C solidus / liquidus Density, g/cm³ Electrical Resistivity, µΩ⋅m Thermal Conductivity, W/m⋅K Tensile Strength at Break, kgf/cm² Tensile Elongation at Break, % Brinell Hardness, HB alloys of tin (Sn) with silver (Ag) and / or copper (Cu) Sn96.5Ag3.5 (alloy #121) 221 / 221 7.37 0.123 55 580 35 15 Sn95Ag05 (alloy #13…

[Clemence]

mattlward · 2019-08-15T13:42:09.000Z

You will definitely want solder paste for led reflows. Mountain Electronics sells one that works very well. When I reflow, I apply the paste and the led’s and use a hot air reflow gun to heat the bottom of the MCPCB until the led’s do the wiggle dance and settle in. I often help them with a q-tip so they are down and square.

Which MCPCB? I really like to use copper core with a white upper finish. The Noctigons are/were great boards, extracted heat well and reflowed well, but they are RED. This will affect the tint of the output on quads and triples. How much? Depends upon the build.