Patent ID: 9642261
Date: 2017-05-02
CPC Classifications: H01L,H05K

Claim:
1. A method of fabricating a multilayer composite structure comprising feature layers extending in an X-Y plane, each adjacent pair of feature layers being separated by an inner via layer comprising via posts that couple adjacent feature layers in a Z direction perpendicular to the X-Y plane, the via posts being embedded in an inner layer dielectric, the multilayer composite structure further comprising at least one outer layer of terminations comprising a two dimensional array of copper via posts that are only partially embedded in an outer layer of dielectric that extends for at least five microns beyond an outer layer of pads, such that part of each copper via post in said two-dimensional array protrudes between 5 and 50 microns beyond a surface of the outer layer of dielectric, comprising the steps of: (i) obtaining a substrate comprising alternating copper feature layers and connection via layers embedded in a dielectric; (ii) thinning away an outer layer to expose ends of a layer of copper vias; (iii) sputtering a layer of copper over the thinned surface; (iv) applying, exposing and developing a penultimate pattern of photoresist; (v) electroplating an external feature layer into the pattern; (vi) stripping away the penultimate pattern of photoresist; (vii) applying, exposing and developing an ultimate pattern of photoresist corresponding to the desired a two dimensional array of copper via posts; (viii) pattern plating copper via posts into the ultimate pattern of photoresist; (ix) stripping away the ultimate pattern of photoresist; (x) etching away the seed layer; (xi) laminating a dielectric outer layer; (xii) planarizing the dielectric outer layer; (xiv) plasma etching the dielectric outer layer to expose ends of said two dimensional array of copper via posts to a desired depth of between 5 microns and 50 microns, and (xv) applying an Organic Solder Preservative (OSP) to the copper posts.