Laser soldering?

[Laser Dude]

Hi all,

If I use a 405nm or 445nm laser diode, how much power would I need to melt solder paste? The solder blobs would be roughly 1.5mm x 1.5mm max and about 1mm high. Melting temp is approx 300 deg-F. Would a 3W laser do the job?

This video shows an example (see around 4:25)... https://www.youtube.com/watch?v=LDpc1-lV5Ns

Thanks.

 

[Aleksa]

Why would you solder with a laser ?

 

[Laser Dude]

So I can CNC-automate it as part of the pick-and-place process.

 

[SteveT]

My 1.7w 445 can ignite white paper which is regarded to have an ignition temperature of ~230C/450F. Assuming correct focus and ample heat absorption I'd say you could 'indent' a blob of solder but not sure if you could melt it. I might try it and report back.

Edit: All I could do on assorted sized blobs was make an indentation in the solder. It would not be practical to desolder with a laser not to mention the high levels of reflection involved

 

[Aleksa]

https://www.youtube.com/watch?v=KnyB9btlhS8

CO2(1000+nm) laser,or high power brick semiconductor type. Probably in the range of 50-100W.

 

[Laser Dude]

SteveT, that would be great. I can send you a PCB, some components and some solder paste if you wish.

Aleksa, how did you figure out or calculate that much power. I'd think the mass of a 1.5mm blob of solder paste should be *very* low.

 

[Aleksa]

You can get away with 1-2W 445nm,but for hi speed and precision,you need a correct wavelength and power to heat up the material very fast. From my experience,a 40w 808nm is still a bit to weak for hi speed and accuracy.

 

[Laser Dude]

I'm still not well versed in which wavelengths are best for what. If I can get away with 1-2W 445nm, would 3W be good enough? Or what wavelength is best. I really don't want to mess with CO2 tubes and mirrors etc.

 

[Aleksa]

CO2 would be your best choice. Cause other wavelengths will just be reflected.

 

[10fenny]

I tried to melt solder with my 1W 445! It vaporized it! it was really tiny solder though.

 

[The Lightning Stalker]

It's not as easy as it looks. Spot size,
power, time, and temperature must all be
very carefully controlled. If you can get
it working, let us know. We are very
interested in such things.

 

[Sigurthr]

Fwiw; I tried it with a 15W CO2 laser focussed with a 100mm FL ZnSe lens. Did not work; as soon as the solder's top surface liquifies it becomes too reflective and absorbs no more light. Peak power has to be enough to liquefy the entire target without vaporizing the surface, and depth of focus has to be enough but not so much to damage the traces.

 

[Laser Dude]

Thanks for the data. What type of solder are you guys using? My intention would be to use solder paste, which looks very dull. It would only start reflecting once the solder has already melted. If we point 2 or 3 lasers at the solder blob from different directions (say 45-deg angles to each other), wouldn't that help to melt the whole blob quickly, rather than just melt one part of it before the laser gets reflected?

 

[SteveT]

Thanks for the data. What type of solder are you guys using? My intention would be to use solder paste, which looks very dull. It would only start reflecting once the solder has already melted. If we point 2 or 3 lasers at the solder blob from different directions (say 45-deg angles to each other), wouldn't that help to melt the whole blob quickly, rather than just melt one part of it before the laser gets reflected?

Standard lead-free rosin core 0.8mm spool. I will do some further experimentation today using an IR thermometer to see if I can measure the surface temperature of the solder whilst being lased. I also have two high power 445 units which I can test together. Will report back later

Update.

Not much luck with the IR thermometer but I can say that when focused to a pinpoint, my 2.4W 445 was able to melt the solder from the spool in approximately 12-15 seconds.

Happy to try further experiments if required

 

[DashApple]

I haven't tried to solder with it , but a 7W 940nm laser has no issues melting tin/silver solder with flux core , not to sure on the lowest power you could get away with .

00140001 1944 by TwirlyWhirly555, on Flickr

 

[SteveT]

Great pic, that's one beast of a laser!