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Re: gEDA-user: Silkscreen over pads

Larry Doolittle wrote:

On Mon, Jan 30, 2006 at 09:23:04AM -0800, Matt Ettus wrote:


Please note that some new parts have a RECOMMENDED footprint from the
manufacturer which has silkscreen ON THE PAD intentionally. This is
done to create a grid pattern on the large center pad to ensure
multiple contact points. PCB will need to be able to print silkscreen
in those areas.



That just sounds weird.
Wouldn't it be be better to use the soldermask for this purpose?
There are many boards made with no silkscreen at all.

    - Larry




Another way to do this is to explicitly pattern the solder paste. Many manufacturers recommend this for their parts, especially for power components with large pad area. Unfortunately, it doesn't look like PCB supports this approach either. You would have dedicate a mask layer to it, rather than just making the paste pattern the same (or slightly smaller) than the pad. (Another request for more layers???)

Using the silkscreen to pattern the solder paste depends on good registration of the silkscreen, which is not usually that good. (This is not as much as much of a problem with the past since surface tension helps with the solder paste.)
The silkscreen also has a tendency to get into the gap between the pad and the edge of the solder resist opening. Sometimes it will just not stick to the pad.

Joe T