Screaming Circuits: Silk on Pad


Silk on Pad

We've written about things on or in pads before. Mostly vias in pads. But this is something less common: silk screen on pads. It does happen. In fact, I wrote about it just the other day. This one though is a really extreme case.

Silk_on_pad You can see that we did attempt to scrape the sik screen off of one of the pads. Some times we can do that and get away with a decent prototype assembly, but sometimes that just adds in too many other problems. In this specific case, there were just too many cases of silk screen ink covering pads. It was all over the place and it was just too much. We can't use these boards.

There are a few things you can do to prevent this.

  1. First, dig into the parts library. Examine the silk layer and make sure it doesn't stomp on the solder area like this. Modify the library parts if you have to.
  2. Make sure your board fab house has good registration. Sometimes this is caused by poor quality control and the fab house and not the libraries, as was the case here.
  3. Select a board fab house that will clip the silk screen off of the pad area during fab. It's always better to fix the problem where it is caused, like in the library, but it's good to have a back up plan. Sunstone does offer the service of clipping the silk screen off the pads. You have to ask for it, but it could have saved these boards.

My advice to you: Always double check all of the layers and ask your board fab house to clip the silk screen just in case.

Duane Benson
It may look like a silver Oreo, but it doesn't taste as good


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