SnBi based solder paste has very BAAAAD thermal properties and very brittle. EDIT: I only use it for [wire pads] on hard to solder MCPCB, mixed with approximately 30% Sn60Pb40 to make it slightly flexible. Never use it for LED or anything requires good thermal conductivity.
AFAIK, Sn52Bi48 only has 19W/MK TC. For comparison: copper ~400W/MK, Aluminum ~200W/MK, Brass ~100W/MK, Stainless steel ~16W/MK, Sn63Pb37 51W/MK, SAC307 62W/MK.
[Clemence]
I figured that might be the case, I originally got it because it was the only thing available.
Useful information:
[Clemence]
@Muto, do not use SnBi thermal paste for anything other than soldering springs.
It does not work well for LEDs and connections at all.
Awesome info, thanks!
Except mixed. I mixed it with ~30% Sn60/Pb40. But don’t forget to heat it first to temp slightly above 60/40 melting point. Otherwise the 60/40 granules will stays unmixed. You still get around 150C combined melting point
[Clemence]
I use this stuff SMD291AX50T3 Chip Quik Inc. | Soldering, Desoldering, Rework Products | DigiKey
Works really well for me.
All the resistor’s plus cap’s (size 0402) and other components are reflowed with the Chipquik and a hot air.
I use this same stuff for all my led reflows too, I haven’t found a need to try anything else, if it’s not broken why fix it.
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I agree 100%. I haven’t found anything better. The added silver also helps improve conductance.
I know Micro Center has locations in PA, so if you have one near I’d suggest checking out their soldering supplies. I used to order everything after Radio Shack went away until I finally realized Micro Center has just about everything you’ll ever need.
I don’t even use solder paste. I use the same solder that I use with my iron, Kester 44.
I clean the old solder off the pad then add flux and solder with my iron. Then more flux and put the led on top and heat the mcpcb up again.
The thing about pastes is they go bad over time and then don’t work well. I’d rather have the reliable spool and do the extra step. Just my opinion.
How do you reflow? If you are using hot air for a PCB or hot plate for MCPCB paste is really helpful. I have been using the same cheap syringes of paste for a few years now without issues.
Hot air.
A lot of pastes technically expire like 6-9 months after date of manufacture. I rarely reflow stuff, so that paste just goes to waste with me. I’m also not real comfortable using it after the expire date. It’s probably okay, but eh.
You can revive expired paste by mixing some IPA in. Its just the carrier fluid for the flux that evaporates
You guys rock.
Ordered the MG
Figured there would be plenty of choices and just like when I first visited here, I have no clue what a lot of the terms used in the above posts mean and don’t need to know just need what works all around best for an amateur hobbyist and it looks like this stuff will do well.
Thanks again
Keith
The thickness of alloy is very small to have a significant effect on final heat dissipation. An more narrowed space- the p-n junction to thermal pad. You was compare the junction themperature with different alloy, with infrared thermometr?
It is significant. 50W/MK vs 86W/MK TC made huge difference in output. Haven’t tested 19W/MK vs 50W/MK but I suspect the difference would be much greater.
[Clemence]
It’s works good but not my favourite. Keep it in cool in an air tight container, gets dry fast when left open overnight. I prefer higher oily flux content. Get the syringe container for longer shelf life.
[Clemence]
I’m new with soldering paste and bought this paste from ali:
When heating it with hot air it doesn’t realy melt and the structure stays the same(tried temperatures from 150-450°C), also the color of the paste stays grey and I assume it should get silver when melting(like tin)?
It doesn’t get realy hard when cooled down, I can scratch it of with my fingernails
I stored it in the fridge(4°C) as soon as it arrived here, but it did 2 weeks from China till here, maybe the higher temperature within shipping time did something with the paste?
i get mine from digikey, they ship in cold container like medicine, or perishable food, if the paste requires it. i usually buy small quantity, and i do not buy a lead free, i do not believe a lead solder under the led, in a sealed light is a cause to be concerned, but it makes more reliable joints. to be honest i never even look at brand, i used several different brands i got from them, not one gave me an issue.