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Drill Hole in a SMD Pad

ScottCad

Hi guys, kind of a general question this time. I have a farily dense board with lots of decoupling caps "0603" footprint. I was wondering has anyone used drill in a pad to get to the internal power ground layers without seeding a via. What I was thinking of doing is putting a small 10 mil drill hole in the center to the 0603 pad to connect to the inner layers, kind of make that 0603 pad a th pad.

I dont believe the solder paste will wick through the 10 mil hole to the bottom side of the board, kind of wanted to put the idea out there to see what you think

Thanks Scott

  • Scott,

    Puttin vias on pad is what I really like as a designer. It connects the cap directly to the power plane.

    Don't put just one via, put 4 small ones. 

    I remember reading a app note by ultracad(I think), that showed the difference in power integrity.

    I think the problem will be with manufacturing. Check if it increases cost. 

     

  • I believe you should investigate blind vias with your fabricator.  The cost increase comes from having to do the multilayer lamination and drill steps at least twice.  The b-stage epoxy will become liquid and fill in the via holes so you won't have paste wicking problems.

    Including the drill with the pad is not a good idea.  Common practice is to keep flexibility in moving those vias around to avoid bumping into other things.   Investigate same-net DRC checking.

  • Guys, thanks for the advice and assistance, I am going to contact the company that assemble our boards to confirm if they can apply solder paste to a land that has a small drillhole in it. Off the cuff I dont see a problem in doing this but it is better to confirm before I push the go button.

    Normally I use a 25 Mil via with a 12 mil drill, but on a dense design a via sometimes just wont fit. The thing I do like about the drill in pad is that when used with a decoupling cap for a pin you are connected directly to the plane with the shortest possible distance to the pin.

    Thanks Again Scott

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