A low‐cost solder‐bumped chip scale package ‐NuCSP

A new solder‐bumped flip chip land grid array (LGA) chip scale package (CSP) called NuCSP is presented in this paper. NuCSP is a minimized body size package with a rigid substrate (interposer). The design concept is to utilize the interposer to redistribute the very fine pitch peripheral pads on the solder‐bumped chip to much larger pitch area‐array pads on the printed circuit board (PCB). Using conventional PCB substrate manufacturing processes, NuCSP offers a very low‐cost package suitable for memory chips and low pin‐count application‐specific ICs (ASICs). Also, NuCSP is surface mount technology (SMT) compatible and can be joined to the PCB with a 6‐mil (0.15mm) thick 63wt %Sn‐37% Pb solder paste.