FEDEVEL
Platform forum

aleph_null , 07-03-2016, 10:04 PM

Hi, I have a few follow up questions to the PCB design class.

1) When a footprint has pads with a small pitch, the solder mask sliver in between adjacent pads becomes smaller than the PCB manufacturer's capabilities, even while using the smallest solder mask expansion (see the attached images for examples). What should I do in these cases?

2) If I intend to solder my components by hand, should I use the sizes recommended for reflow or wave soldering?

3) How do I know what pad and hole sizes I should use for through hole components?


thanks!

robertferanec , 07-04-2016, 11:05 AM

1) If needed, I make the solder mask expansion smaller (if there is no other way, I go as small as 1mil). For through hole pins, you can very often make the pins oval (not circular), that also helps. Note: I always prefer to keep the mask between the pads as it helps to separate the tin between the pads and it helps to prevent creating short circuits during soldering. Usually, the minimum solder mask which I use is 0.1mm.

2) I always start with reflow footprint. Then, I print out the footprint on a paper, I place the real component on the paper and if needed I adjust the pad size to be able to solder it by hand.

3) Usually, the hole size will be in the component drawing. They sometimes also recommend the pad size, if not, you can use any pad size you think is reasonable.