Which solder paste for LED reflow?

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Muto
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Which solder paste for LED reflow?

Got a hot air gun today and would like to reflow some emitters
Is this a decent choice for something available on Amazon?

https://www.amazon.com/dp/B017RSZFQQ/ref=sspa_dk_detail_1?psc=1

It has lead (probably not much content), is that the better choice over the lead free?
All advice is appreciated.
Thanks!

Keith

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Lexel
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I would not buy lead free paste unless its low temperature BiSn
this paste has not even marked which compond it is so I would not buy it

sn62pb36ag2 is still the best leaded solder compond

lead free SN98 or 96 paste has a too high melting temperature
if you use hot air then on a bigger piece of Aluminum or copper asbuffer so it heats up and cools down steady and slow
and heat aypplied from below, not from above!

RobertB
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I use this stuff. Seems to work great

Enderman
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MGchemicals

KawiBoy1428
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Tried them all, I liked MG Chemicals, but went back to Kester EP256 63/37. I buy from CML Supply it seems to be fresher because they sell a crap load on Amazon/FleaBay and in my experience it flows a bit better/faster/cleaner with a hot air/reflow station and last longer, IMHO, it was $17.99 free shipping 3 days to the door, usually.

https://www.cmlsupply.com/kester-ep256-lead-solder-paste-63-37-syringe-d...

KB1428 “Live Life WOT

Lexel
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also the grain of the paste matters if you want solder very small stuff
Type 5 is smallest paste

amars7
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Like the others I usually use the MGChem stuff. I have also used a lower temp Sn/Bi paste called Maker Paste, it seems to work fine as well.

clemence
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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]

amars7
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I figured that might be the case, I originally got it because it was the only thing available.

clemence
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Useful information:
http://budgetlightforum.com/node/51628

[Clemence]

BlueSwordM
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@Muto, do not use SnBi thermal paste for anything other than soldering springs.

It does not work well for LEDs and connections at all.

My very own high current Beryllium Copper springs Gen 3:
http://budgetlightforum.com/node/67401
Liitokala Aliexpress Stores Battery Fraud: http://budgetlightforum.com/node/60547

amars7
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Awesome info, thanks!

clemence
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BlueSwordM wrote:
@Muto, do not use SnBi thermal paste for anything other than soldering springs.

It does not work well for LEDs and connections at all.

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]

moderator007
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I use this stuff https://www.digikey.com/product-detail/en/chip-quik-inc/SMD291AX50T3/SMD...
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.

.

Lexel wrote:

sn62pb36ag2 is still the best leaded solder compond


I agree 100%. I haven’t found anything better. The added silver also helps improve conductance.
WillyD
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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.

JasonWW
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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.

staticx57
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JasonWW wrote:
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.

JasonWW
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staticx57 wrote:
JasonWW wrote:
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.

mattjk
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You can revive expired paste by mixing some IPA in. Its just the carrier fluid for the flux that evaporates

Muto
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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

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DB Custom
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Kester EP256, nothing else. To me the MG Chemicals sucks.Kester EP256

nsl18
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clemence wrote:
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]


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?
clemence
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nsl18 wrote:
clemence wrote:
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]


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]

Chatika vas Paus
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Someone used this? Good for leds?

clemence
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Chatika vas Paus wrote:
Someone used this? Good for leds?

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]