![]() The bottom is 10-20C colder from my thermocouple investigations but does catch up if I let it sit for too long. This paper is a summary of best practices in optimizing the reflow process to meet these challenges of higher reflow temperatures, smaller print deposits, decreased powder particle size, and their affect on the reflow process. The FTDI chip on top didn't fall off the board when I reflowed a second time with it hanging upside down. 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. The Temperature gradient is important because too quick changes of temperature can cause damage to components. The aim of the preheating stage is to accumulate heat smoothly in the board and the components. I have to hand solder the holder next time. Reflow solder profiles usually have four stages, preheat, thermal soak, reflow and cooling. 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. If you follow the steps given in this paper and use a KIC profiler, you will get the most accurate profile possible of your production boards. It must heat to a minimum of 286☌, and 300☌ is preferable. SOLUTION: Use a soldering iron that is rated for 10-88-2 solder. Maybe my coin battery holder will not melt. Typical rework soldering irons do not get hot enough to melt 10-88-2 solder. ![]() 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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