MicroCSP (Chip Scale Package) Parts
We received a question about a MicroCSP (also called flip-chip by some manufacturers or Wafer Level Package) packaged part the other day. If you're not familiar this type of package, it's a lot like a little BGA - a very little BGA. Basically, the solder balls are bonded right to the silicon die or a substrate layer on the die. That means that the entire part is the size of the silicon. Very small.
This particular part is an eight ball chip that is 1.8mm X 2.5mm and less then half a mm thick. The solder balls are in two rows at a .5mm pitch. It's a pretty impressive package. Interestingly, though, this isn't the smallest part or pitch we've placed. It's still bigger than an 0201 passive and we've placed a Texas Instruments 4 ball flip-chip that's a bit smaller than this as well. We've placed larger MicroBGAs with .4mm pitch also. Check out this Appnote from Analog Devices talking about one of their wafer level chip scale package parts.
Because there aren't any wire bonds and leads, this package can deliver improved electrical performance and, of course, you can put more of them on the board. Still, there are a lot of challenges with this type of part. If you are going to use one of these, make sure your board house can really register fine traces and solder mask.
NSMD (non solder mask defined) land pads are recommended and if possible don't route any traces between pads. If you need to put vias in the pads, the only reliable method is to fill and cap the via. If you do that, just be sure that the surface ends up totally flat. (there's always one more thing, isn't there?) Sometimes plugged and plated over vias end up slightly bulgy or with a slight dip. Either will lead to a less reliable connection.
We can assemble this type of part for you, but it would be best to give us a call and chat with one of our manufacturing engineers first.
Tiny is as tiny does