[PCB_FORUM] Re: Strange solder paste mask creation... how to??

Hi Gene,

We have created new layers: manufacturing/autopaste_top and manufacturing/autopaste_bottom.
I have a Skill script that splits paste pads into acceptable sizes and places the resultant shapes on the autopaste layers.
If I need specific shapes, I place those on the original layer and these get copied through.

See attached.

This not only meets RF requirements but keeps our production engineers happy because the edges of smaller pads are less likely to be caught by the squeegee.

I don't like the idea of adding extra pins to the packages or modifying the original paste pad as that makes your library technology bound.

Cheers, Dave


MAILER-DAEMON@xxxxxxxxxxxxx wrote:

OK here is one for the group...

We work with some rather strange shaped parts in the RF world... things that are built the way they are built, due to physics, not some IPC or JEDEC suggested "standard" footprint. (you digital folks are lucky... )

These footprints often have large odd shaped center "slugs" in the middle of the package that needs to be soldered for RF ground and heatsink reasons. Rather than put an equal amount of solderpaste on the slug (in other words a 1:1 solderpaste "pad" equal to the component "pad") we have found that smaller solder paste shapes work better... the part will then not "float" on the huge center pad, which can cause the outer, smaller pads to not solder correctly. Making smaller solder dots and stripes on the center "slugs" roughly the same size as the other connection pads works best.

Well, the problem with this is defining what ends up as several "pads" for pastemask verses one (odd shaped) "pad" for the slug. 

It looks as though the best solution, at this point, is to put the paste mask 
on a new subgroup layer:  package geometry pastemask_top and 
pastemask_bottom...  this permits us to add any unusual hourglass shapes, dots 
or stripes, or whatever as recommended by the manufacture as needed.

I am just wondering, are there any other better solutions?

Gene Carman
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