Hi, Bob
It depends on what you are trying to solder, rework, mark, or weld. Most laser soldering systems on the market today are typically set up to repeatedly solder the same product in high volumes, that is their niche or specialty. Many of those use the bulb system you describe, or a single laser that is restricted to a particular task.
There are no laser soldering machines that I know of that can be set up to cover a wide variety of materials and tasks as a single machine. The combination of our machine and our patented chemical bath or chemical spray systems, special pre-heaters, solder paste treatments, etc, allow us to solder just about anything with different lasers, I/R sources, or cure with U/V, etc. Analog Technologies has spent the last 5 years doing nothing but laser-soldering and related process development 8-12 hours a day to get to this capability. They are very, very good at it, but the biggest reason we have been able to be so successful is due to our machine's capabilities (as well as having an excellent engineering staff). We started out looking for a machine on the market that could do what we needed to accomplish for a single contract, and performed a very thorough evaluation of many machines on the market but could not find the exact machine we needed. They all had some type of serious drawback. So we designed and built our own machine, and have been developing processes around it ever since. The capability of being able to quickly switch out or simultaneously control up to 4 different energy sources such as different lasers, UV sources, I/R sources, etc., helped us to be able to perform many, many widely different processes in a very cost-effective manner. Our machine can load 4 different lasers and operate them simultaneously, if we ever needed to do that. Each fiber/optic channel is controlled by its own individual iris so we can run programs that automatically control the individual source power, focal spot size and focus, pulse time, dwell time, beam travel and speed, etc. That is how we can perform tasks such as reballing, ball attachment, pinpoint soldering, microweld, and so on with a single program and set-up.
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Thursday, February 04, 2010 9:31 AM
To: 'TechNet E-Mail Forum'; Stadem, Richard D.
Subject: RE: [TN] Laser soldering of BGA
Hi,
On focusing Heat:
I looked around and found docs that 1 micron IR will heat solder metals and
FR4 at about the same rate. Longer wavelengths heat FR4 and reflect off
solder. I found quartz "Bulbs" that peak at 1 micron. CO2 Lasers emit at 10
microns, a little on the long side.
While the laser is collimated and easily focused the bulbs are a lot less
expensive. A simple "Long Tube Reflector" seems to be sufficiently focused
for rework of PCBs.
Can any verify the above findings? I only know enough to be dangerous here.
Thanks,
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, February 04, 2010 10:07 AM
To: [log in to unmask]
Subject: Re: [TN] Laser soldering of BGA
I agree with you, but just keep in mind that laser is darn near infinitely
controllable. I can easily "warm up" a surface by adjusting the power, lase
speed, focal spot, dwell time, etc.
But warming up or pre-heating a large surface area (larger than 4" square,
for example) to reflow temps is difficult in that the laser head needs to
oscillate over such a large area that it is difficult to heat the area when
it is cooling down just as fast, or faster.
35 mm sq. BGAs, no problem. 4" square area of Teflon, I'm not so sure.
However, it would be very easy to perform solder ball attachment to pads on
flex circuits, and then reflow the components to the solder balls using
convection.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Thursday, February 04, 2010 8:53 AM
To: [log in to unmask]
Subject: Re: [TN] Laser soldering of BGA
I'd be very surprised if you could. Two reasons:
1. For the balls heat to melting point the opposite side of the flex
would have to be much hotter as most PWB materials have a low thermal
conductivity. Thus you'd probably damage the flex material.
2. Lasers I've seen apply heat very quickly. The flex material would
probably burn before the balls melted.
My stupid suggestion would be to get the BGA device without the balls
and attach it to the flex with a hot bar and conductive paste or film.....
Regards,
On 04/02/2010 14:41, Stadem, Richard D. wrote:
> Trying to heat flex to the temperature required to melt solderballs on the
other side, I am not sure if that can be done using laser, nor would it be
feasible due to the amount of time required versus convection reflow.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
> Sent: Thursday, February 04, 2010 8:21 AM
> To: [log in to unmask]
> Subject: Re: [TN] Laser soldering of BGA
>
> Technos,
>
> There are 2 main ideas I can gather from your answers:
>
> 1. Why do I bother with laser when I could reflow? Well, as I said, reflow
seems to warp either the component or the PCB and having no idea about laser
soldering myself, I thought it would be a good idea to inquire. Since it
seems to have no benefit, I believe I better get back to reflow. But not
before asking another one: the BGA is soldered onto flex that is backed by a
12 mil rigid something; are there lasers that could solder from the bottom,
through the substrate, rather than through the part, thus minimizing the
heat seen by the assembly?
>
> 2. Steve K, could you please elaborate regarding the metal stiffener vs.
FR-4. To my surprise, it seems that brass stiffeners yield better results
than FR-4 indeed; shouldn't they give a bigger CTE mismatch?
>
> Thanks,
>
> Ioan Tempea, ing.
> Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
> T | 450.967.7100 ext.244
> E | [log in to unmask]
> W | www.digico.cc
>
> N'imprimer que si nécessaire - Print only if you must
>
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