a plurality of metal bumps connecting a nonconducting substrate and a chip , consisting of : at least a first metal bump having at least one curved face , at least a second metal bump having at least one curved face , and at least a third metal bump having at least a first curved face and a second curved face . the three centers of these first three metal bumps form a triangle , in that the first curved face of the third metal bump is adjacent to the curved face of the first metal bump , and the second curved face of the third metal bump is adjacent to the curved face of the second metal bump .