Is it safe to route through a pad?

[swen_s]

Is it safe to route through a SMD pad or should I always make a T connection to the pad?

And when is it safe to connect SMD pads withoud thermel thermal reliefs? Is it ok for 0805 but not for smaller packages? I often see evaluation boards for DC/DC converters that connects decoupling capacitors from a ground plane to a copper area without any thermal reliefs.

 

[Centmo]

In my limited experience, PCB assemblers will recommend against putting a via through a pad. The problem is that solder may get wicked through the via to the bottom of the board, and leave a bad solder joint on top. If it is a pad underneath a component, it can leave a void and affect thermal performance.

Thermal reliefs just help with the hand-soldering process, but I don't think they're ever necessary. If you're going to assemble your board by hand, as long as you have the right tools, lack of thermal reliefs should not cause you much trouble in most cases. Try a board without them and see. If you're using a company to do your assembly, ask them.

 

[rontopia]

if your using surface mount parts.. do not put vias on the surface mount pads. when the board gos through reflow, the solder paste will get wicked away from the surface mount pad down into the hole of the via and the chance of a bad connection or tumbstoning gos way up.

 

[marce]

Yes.
All the time for SMD components.