First of all, if you are going to tell me to throw my crappy equipment away, and buy a better oven because 3 zones isn't enough for lead free soldering, please find another thread to troll in. We have been using a Hotflow 3 for several years for lead free solder with pretty good results. If you know how to get the most out of what you can afford, like us, please continue reading...
We have a Hotflow5 that is our "backup" when our Hotflow 3 is down. Beleive it or not, we have better results with our 3. The 3 has the belt option, the 5 does not. Would that make the 3 work better, as you are setting the board on a belt that is already warm?
Anyway, on to my real question, The Hotflow 5 has 2 of the 6 "sections" of air nozzles blocked off. I determined that part of our issue is the boards with bigger parts are not hot enough long enough. If I turn the temperature up hot enough to reflow the big parts, the leads on the resistors turn gold. And at just about every setting our SOT23s look terrible. Slower belt with lower reflow temp didn't work, as I think we were burining off the flux before it hit the reflow zone.
Anyway, I took those covers off, and it didn't seem to help, now I'm cooking boards even worse. So was there a reason they blocked those off? With them off, I have 2 preheater zones of 22" each, and the reflow zone at 22". With those blocked, I have a only about 14" of reflow zone. My thought was remove them and get more time above reflow temp, and I might be able to lower the temperature.
Anybody know what length each zone should be? Should I put the shields back on the Reflow zone?
Ideally I want to find a profile that works on a wide range of boards, as we run 4 Pick and Place machines, and are down to 1 oven. Even with the other fixed, we only have 2. So Ideally I have one set for Lead, the other for Lead Free. It used to work well with the Hotflow 3 running.
Does anybody have a good resource for profiling? I have been attaching a thermocouple to a through hole pad on the board as it runs through, and trying to tweak it with that. Do I put one on the biggest part, and one on the littlest? Do I use a board that has already been run through, or only a fresh board? How do you attach the thermocouple without it pulling the part off the board?
Any suggestions for better (And easier) methods would be great.
We are trying to find a used "waverider" or something similar, but they are expensive, and our datalogger with thermocouples seems to work pretty well (until they get caught in the belt, that is).
Thanks,
Jon
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