| Does anyone have any recommendations on spray fluxers? Are there major differences between the high priced ultrasonic machines to the low priced flux/air spraying machines? We are going to be spraying an OA flux with 11% solids content. Are there any precautions I need to be aware of for spraying an OA flux besides having a stainless nozzle and a purge option? | | Thanks, | Todd | Hi Todd,
There are big differences between the high-priced ultrasonics and the more economic time/pressure systems. And yes, unfortunately, you get what you pay for...
I really like USI's Opti-fluxer. It's an ultrasonic head that reciprocates back and forth under the circuit board. I've got an article coming out about it in Electronics Packaging and Production. I think it's in the March issue, but it may not be until next month. I'll email you a copy of the study I did where we put the Opti-Fluxer head-to-head with the Jet Fluxer. In my opinion, the Opti was much better. And as a bonus, it was about $20K cheaper, too.
Now I know I said you get what you pay for, but in that sense I was referring to the simple time/pressure systems that typically use Binx spray heads that were designed for spraying paint. A high solids content will clog these in a heartbeat, particularly if the carrier is alcohol.
The other problem is that these types of sprayers cannot atomize the flux as readily as the ultrasonics can. The coarser mist cannot penetrate the samll clearances in pin thru hole parts or small vias. You end up throwing a lot of flux at the board in an effort to try to get topside solder fillets. Then you have so much flux on the bottom of the board that you underactivate it, getting crappy soldering, and letting the wave wash it off, so you end up with the black rosin sludge floating on top of the solder pot. Doesn't sound pretty, does it? It isn't.
As for precautions associated with OA, everything around the flux mist should be stainless, not just the nozzle. OA is active at room temperature, and seems to never get exhausted. You'll need a stainless enclosure, a good curtain to keep it from getting into the wave solder machine chassis, stainless exhuast ducts, and teflon delivery hoses. Most of the fluxer manufacturers offer an OA upgrade package that encompasses these precautions. If the manufacturer claims that their regular spray fluxer will handle OA just fine, don't believe them!! Either they haven't really done the life cycle test, or they're counting on the revenue from the spare parts. And they're sure as heck not just altruistically making all fluxers super-beefy in this cost-compettitive market.
I think that pretty much covers it. Sorry to be so long-winded, but I haen't been on the SMT net for a few weeks and I think I just got carried away. I'll email the report.
Chrys
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