Laser for soldering

Hi.

First post here.

I want to use a laser to solder. I hope to apply solder paste, which is dark gray, to a small copper pad, and use a laser to create a finished solder joint.

I already own a blue "burning" laser, purported to be about 3 watts (not sure that is true) and it does indeed create a solder bead. But I think the laser is not strong enough to do what I want. It takes about 5 seconds for the solder bead to fully form.

I understand that once the metal is melted, it will reflect much of the incident energy. I still think this will work, though, but have issues:

1- Is blue the right color? Would IR be better?
2- I would like the focal length of the beam to be about 8".
3- I need a spot of about 2mm in diameter, or better a rectangle of 2mm x 4mm. I can always move the laser off the optimum focal length to create the desired spot size.

Any recommendations? I actually will need six lasers, as I want to solder six pads at once.

I understand safety, especially will invisible IR.

Regards,

Craig Newman

the types of lasers you are talking about are illegal in most countries to sell you are talking about building them as for color spectrum i don't think that will matter in this context the reflectivity of solder will reflect all wavelengths equally IR might be better but it is inherently more dangerous. humm it seems industrial laser soldering is ir...