Hey John,
Can you explain a little about thermal relief and the ground flood fill connection?
I like Dave T am a beginner and am interested in why.
I just did my first board and used flood fill, I am not really concerned with thermal relief as my board is only for signals not power but would like to understand the practical aspects of board layout.
regards
steve w
Sure, it's simple. When you're soldering to something attached to a big chunk of copper, like a copper pour for example, you'll have some trouble pumping enough heat into the joint to make a good joint. Thermal reliefs are generally implemented as little spokes that come off the pad and attach to the pour. They limit the flow of heat to the big chunk of copper, and make for easier soldering.
You can generally configure them for shape and size. After the pour, you do need to examine the board closely to make sure that all of the reliefs are actually adequate. It's not unusual to loose a spoke or two on some pads because of clearance to a nearby component. You also want to check that the pour itself has good continuity without getting too thin in areas. For example, sometimes you end up with sections of the pour being connected to each other with these thin, strands of copper. It can happen because of clearance to other components or traces, and you just need to give the board a little scan when you're done to make sure that you're happy with what you have.
I usually size my spokes so that I can loose two of them on any pad and I'm still good. Soldering would be slightly easier if I sized them to be barely adequate, but it's easy enough as it is, and this way I don't have to chase down every last issue to get a working board.
But that's just my own design philosophy. There are probably lots of different ways to do this, and they're probably all correct in their own way.