Device and method for forming and attaching an array of conductive balls

Claim 1

A preform of conductive material capable of being formed into a plurality of conductive balls for accurate and secure attachment to respective conductive ball receiving areas of a substrate, comprising in combination: (a) a substantially planar structure having an upper plane and a lower plane, said upper and lower planes being separated by a maximum thickness; said preform also incorporating upper intermediate and lower intermediate planes, said intermediate planes being separated by a minimum thickness; (b) said preform being perforated with a plurality of through-holes to define a matrix of sub-preforms, each said sub-preform comprising a substantially non planar structure, having a thickness that varies from said minimum thickness to said maximum thickness, wherein: (i) said sub-preforms are connected to one another by thinned regions of conductive material; (ii) said sub-preforms being spaced form one another so as to be coordinated with respective individual conductive ball receiving areas of a substrate; (iii) said preforms incorporate contacting means, said contacting means being solid protrusions of said conductive material, extending to said upper plane from said upper intermediate plane and to said lower planes from said lower intermediate plane, for the purpose of making positive contact between said preform and said substrate when the preform is superposed above and, substantially parallel to said substrate; said contacting means further comprising in combination: a) protrusions on each of said sub-preforms of said preform; b) said protrusions being substantially centrally located relative to the through holes defining each sub-preform; c) said protrusions configured in a shape selected from the group consisting of column, cone, truncated cone, spherical section and hyperboloid; (iv) each of said sub-preforms contains a volume of conductive material sufficient to form a conductive ball of a desired diameter as said preform is heated for a length of time above a melting point of said conductive material such that said preforms separate from each other along said thinned regions, each conductive ball for attachment to a respective conductive ball receiving area of said substrate, thereby providing a means for attaching an array of accurately sized spheroids of conductive material to a substrate with greater accuracy and reliability, and at lower cost that with current methods.