日本語
I just got back some prototype PCBs from a PCB manufacturer and I noticed that they took out the solder mask between the pads of a QFN-40, 0.4mm pitch footprint.
I asked for the reason and they said their minimum solder mask bridge is 10mil (0,254mm). This constraint is not listed in their manufacturing capabilities, btw.
How important is it actually to have solder mask between the pads? For the prototypes and hand-soldering it didn't appear to be an issue, the PCB works as expected, would it be more critical for an actual PCBA run?
- Comments(1)
A****min
Aug 21.2019, 09:28:26
The real purpose of solder mask is not for stopping solder bridges. Solder will bridge across mask, if you have too much anyway, particually at fine pitches. Its to stop solder from wicking down tracks.. if you hav eever used a board with no solder mask ( prob dip parts ) you will know will know that you can put the solder on any old bit of copper.. For wave soldering this would have been horrific.
At 0.4mm pitch your stenciling will need to be resoanbly good.
