I've been using a halogen oven with a home made controller as a simple reflow oven. The controller uses a thermocouple to measure and control the temperature profile.
The problem I have is that I'm getting inconsistent results depending on the component. As a test I made a simple board with 8 resisters and 8 LEDS. In this case I've put a little solder on the pad using a soldering iron, positioned the components on the pads and then re-heated in the oven. I cleaned the board with liquid flux before applying the solder and again after applying solder (In one case – I had similar results when I didn't do this second clean)
The resistors have all come out fine. They are positioned well and the solder looks good. The LEDS however all come out terrible. They all just about have proper electrical contact so the board "works" but they are very poor indeed.
The components are all about the same size and have similar contacts. There was no difference in the preparation. The LEDS are very slightly thicker I suppose. They are within 1cm on the board and I don't believe would have significantly different temperatures.
I'm wondering if anyone has any explanation or suggestions about how to improve? Maybe I need to increase the temperature? Or hold the temperature a little longer?