Abstract: An integrated circuit assembly includes a base board, an interposer, and an array of solder balls electrically and structurally interconnecting the interposer and the base board. The interposer has a backbone layer having a backbone stiffness, a first compliant layer affixed to the backbone layer between the backbone layer and the integrated circuit and having a first-layer stiffness of less than the backbone stiffness, and a second compliant layer affixed to the backbone layer between the backbone layer and the base board and having a second-layer stiffness of less than the backbone stiffness. An integrated circuit is supported on the interposer. The integrated circuit includes integrated-circuit bonding pads thereon and a bonding pad protective coating overlying the integrated-circuit bonding pads. An electrical interconnect extends from the integrated circuit to at least one of the solder balls, and a cover overlies and protects the integrated circuit.

Abstract: A modified printed wiring board for reducing the cracking of solder joints used to attach ceramic leadless chip carriers to the surface of the printed wiring board. A relatively thin expansion layer is provided on top of the conventional printed wiring board. This expansion layer is bonded to the printed wiring board except at locations underneath the footprint of the chip carrier and solder joints. This expansion layer reduces the stress of solder joints between the ceramic leadless chip carrier and the printed wiring board due to thermal expansion mismatch, thereby reducing cracking of the solder joint.