Baked boards coming out quite dark?

[phonoplug1]

Another problem I have been having is the boards coming out quite dark, looking almost burnt. OK, so I have burnt some boards genuinely, but this was happening even when parts of the board hadn't reflowed, so it wasn't because it was too hot in these cases.

The solution? Well, I guess you should be really careful with this, but it helps a lot. Bake boards with the drawer slightly open. That allows the flux fumes to escape easily resulting in the board coming out less dark. When doing this, you will need to reduce the soldering temperature, as having the drawer open a little seems to mean the thermocouples don't get as hot for the same PCB surface temperature. Previously I was baking with a peak temperature of 255-260 degrees, and now a peak temperature 230 works well with the drawer open a little. When I say a little, the opening at the top of the drawer is about 8mm wide.

If you use the oven in a cold place (garage or loft for example), you got to watch it the first few times, as the software in it doesn't seem to use PID control. The result is that if the environment is cold, it can't quite reach the target temperature with the door open a little - it will hang a couple of degrees short, plusing the heaters with not enough duty to raise it the last degree or two. This can result in the board being baked for a long time (perhaps indefinitely), so thats why you need to keep your eye on it until you have done this a few times and are confident with how it works.

Yes, I have used my oven a lot!