Method for orienting solder balls on a bga device

Abstract

A BGA structure having larger solder balls in high stress regions of the array is disclosed. The larger solder balls have higher solder joint reliability (SJR) and as such may be designated critical to function (CTF), whereby the larger solder balls in high stress regions carry input/output signals between a circuit board and a package mounted thereon. The larger solder balls are accommodated by recessing each ball in the package substrate, the circuit board, or both the package substrate and the circuit board. Additionally, a ball attach method for mounting a plurality of solder balls having different average diameters is disclosed.

1 . A method of forming a device comprising:
 providing a printed circuit hoard (PCB) having a land surface;   providing a package having a mounting surface; and   electrically joining the mounting surface of the package to the land surface of the PCB with a first plurality of solder balls having a first average diameter and a second plurality of solder halls having a second average diameter, wherein the first average diameter is larger than the second average diameter.   
     
     
         2 .- 20 . (canceled)