| Hello, | | I will be evaluating and qualifying two equipment types. The first is a fountain soldering device. I need practical advice on all the stuff you guys and gals know about as good, bad, ugly, best applications, setup, limitations, and all the rest. I've never used one of these things and would appreciate any experienced input. | | I am inheriting an SRT 1000 BGA/Fine pitch rework/repair station. So far it looks straight forward and easy to program and operate. I do question having to edit INI files to set some parameters for board and component types, and sequences, etc. Additionally, the very long removal and replacement arm/rod/tube seems very vulnerable and I can't help wondering about repeatabillity let alone initial accuracy though, from what I've seen so far, no worries? Any experienced input concerning operations, do's, dont's, capabilities, limitations, etc. also would be appreciated. | | Thanks everyone, | | Earl Moon | Hi Earl!
Ah, solder fountains - a necessary evil. What do you want first? The good, the bad, or the ugly?
The good: - quick removal of high pin count devices. Ever try solder-sucking a PGA with a bent pin? You're gonna be there for a while. - Increased throughput vs hand soldering connectors and other things that are located contrary to the solder side of the board, or on DSR boards with tall components that cannot fit in selective solder pallets.
The bad: - Unless you're gonna spend big bucks to automate, this is a highly operator dependent process. The lack of motion normally found in wave sodlering doesn't exist, so you don't get a nice "peel-off" to break bridges. When the fountain of solder drops, you get icicle-type bridges. - A good operator can finesse the board out at an angle to mimic a peel-off and reduce the bridging rate. But everyone developes their own technique. I actually saw one operator develop a technique that involved smacking the board against the nozzle while the solder was still hot to aid in the debridging process. (Yikes!!!! Wouldn't buy that card!!!) - Can't handle fine pitch (below 60 mil) connectors or ones with short lead lengths - bridge city.
The ugly: - Manual fluxing - depending on technique, the product will have unprocessed flux on it wherever flux was applied but not contacted by solder. Paste flux helps. Liquid flux - forget it. - Rapid thermal expansion (okay, call it shock). I don't have to tell Earl the implications here, but for any other readers... What I have found is that if the device being solder fonutained is near the edge of the board, there is a path for the X-Y expansion and contraction, and visually the board looks allright. If the device is located in the center of the board, however, the surrounding rigid laminate prevents expansion in X and Y, so the Z-axis takes the brunt of it. Rework a PGA twice on a board, look carefully, and you'll see the delamination and cracking around it. Cross-section if you dare. That being said, many fountain systems now come equipped with board heating devices to prevent the scenario I just described. Some also provide motion to help debrige. Other will add a little atomized fluxer that will spray through an aperture the size of the nozzle to eleiminate the worry of unprocessed flux.
It all depends on how much you're willing to spend. If you are inheriting a system, you probably don't have a lot of choice, but with a little ingenuity, you can pull a Steve Gregory: Grab some duct tape, a book of matches, and a videotaped rerun of MacGyver for inspiration. Then add an old section of conveyor that no one wants, some blocks to elevate one end of it, an old PITA time/pressure dispensing system that you ripped out of your adhesive dispenser in a fit of rage, the hot air blower from the Pace station that's had its optics canibalized, and an updraft duct for ventilation, and, VIOLA! you've made yourself a miniature wave soldering machine in your spare time.
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Hello,
I will be evaluating and qualifying two equipmen...
- Jan 21, 1999
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