Method and apparatus for reducing cold joint defects in flip chip products

A method of processing an electronic device, the electronic device having a chip surface and solder bumps on the chip surface, wherein at least one solder bump is coated with a foreign material different from the bulk material of the solder bumps, the method comprising:

• dispersing a layer of particles on a surface of a flat plate, the particles being composed of an electroconductive material that is abrasive and harder than the foreign material, and being firmly held in place;
• positioning the electronic device against the flat plate surface, wherein the chip surface faces the surface and the solder bumps contact the layer of particles;
• pressing together the electronic device and flat plate with a controlled amount of force while the chip surface is parallel with the flat plate surface, such that the distance between the two surfaces is decreased and at least some of the foreign material becomes embedded in the layer of particles;
• and
• removing the electronic device from the flat plate leaving some of the foreign material of at least one solder bump in the layer of particles and exposing the bulk material of that solder bump.