Via-in-pad puts a via inside an SMT pad instead of routing out to it, saving space and shortening connections under fine-pitch BGAs and thermal pads. For assembly the via has to be filled with epoxy or copper and plated flat over the top (VIPPO, via-in-pad plated over), otherwise solder wicks into the hole and leaves voids or starved joints. Fill and cap add cost, so designers use it where pitch or thermal performance demands it.
0.4 mm pitch BGA, no room for dog bones, so it's via-in-pad with VIPPO across the whole array.
Also heard as
- VIPPO
- via in pad
- VIP
Related terms
Dog bone
Short trace from a surface mount pad to a nearby via, shaped like a cartoon bone, used to fan out parts.
Microvia
Very small laser-drilled via, typically 0.15 mm or less across, spanning one thin dielectric layer.
Wicking
Solder or plating chemistry drawn by capillary action where it is not wanted, up a lead, into a via or along glass.
Voiding
Gas pockets trapped inside solder joints, seen as light spots on X-ray, which weaken them and block heat.