We've sectioned micro vias down to 0.002" diameter. Grinding and
polishing has been by hand using rotary grinders down to 1200
grit, followed by 5 and 1 micron diamond. It helps if you have a
row of vias, then you grind at a slight angle. The widest via
after polishing is close to the centre line. It takes some skill
which requires time to develop, It's very easy on the course









         grits to go straight through the row your interested in. Using hot
         pressure setting mounting compound helps fill the vias. We use the
         same method for flip chip joints as well. If you are trying to
         section a specific via, then you just have to go very carefully.
         The amount of material removed by the 5 micron diamond paste for
         example becomes significant.

         If anyone is using equipment or jigging to help hit the right spot
         on these small features I'd be interested to hear.

         J Drake
         Celestica Ltd
         Kidsgrove
         Stoke on Trent England