![]() The bottom is 10-20C colder from my thermocouple investigations but does catch up if I let it sit for too long. Heat to about 175C at a slower temperature rise rate (0.5-1C/sec), then the gradient rises to about 180 within 20-30S, and then quickly rises to about 220 at 2.5-3.5/sec, Z Then quickly cool down at no more than 4C/sec. Will have to turn the heat up & down a little at the hold temperatures as the oven cools, and then heats up again. This is the current best reflow oven temperature curve. The FTDI chip on top didn't fall off the board when I reflowed a second time with it hanging upside down. Turn off the heat, crack open the door a little, let the temperature cool down, once below 180C you can open the door full. I did two steps, top side with less components first, then bottom side with more components. I'll produce some videos so you can see what I see. I have to hand solder the holder next time. Many yellow-orange residue and some seem more than just surface. I just did the same run again and similar result. I tried to find temperature with my thermocouple taped to a board but the center seems to be up to 25DegC hotter than indicator on the oven and there is considerable hysteresis. Maybe my coin battery holder will not melt. Maybe I need longer pre-heat time and higher temperature? If it is not a result of sitting for too long in the oven after soldering phase, I will increase the "keep" temperature and let the oven cool boards sooner. The oven seems to be ramping at max rate all the time and then just sit at the set temp once it reaches it. The oven has only 3 temperatures and timers, and then a fourth temperature below which it turns on air cooling.
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