Hey all,
I have 3 questions about reflow. Hopefully someone can help me.
1. I am having a problem. I set the peak at 230 and my mole thermocouples are telling me the temp in that zone gets to 237. How is this possible even if the thermocouple came loose from the board? Even then the temp shouldn't get above 230. I am running without rail heaters and Speedline tells me that the accuracy tolerance for the Omniflow 7 without rail heaters is plus/minus 4 degress C. So, theoretically I shouldn't see temps over 234. Bleed over is not the problem since this is the hottest zone. What could be making my zone hotter than setpoint? Also, my PID is fast ramp, but I've waited until stabilization, so the PID is not the problem. I've also checked the offsets and they are not the problem either. Any help?
2. What happens to solder paste (any no-clean solder paste) when the suggested max peak temperature has been exceeded? I'm only talking about 7 degrees. I know that excessive heat can cause leaching, but what else? Chemically, what's happening when it goes over temp?
3. How does everyone out there verify accuracy of your ovens? What verification process/technique do you use to prove the accuracy of the heat zones and internal thermocouples?
Thanks in advance, Spanky
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