LOW-COST COMPLIANT WAFER LEVEL PACKAGE TECHNOLOGYAuthors: Guilian Gao, Kenneth Honer, and Charles Rosenstein
Date Published: 10/13/2008 Conference: IWLPC (Wafer-Level Packaging)
Tessera has developed a new compliant WLP that dramatically lowers cost over previous compliant WLPs. The resulting package is very similar in concept to a face-down compliant µBGA-W package. However, rather than attaching an individual die to a substrate, this process laminates a compliant layer plus conductor to a wafer. The compliant layer is more cost effective than spin-on polyimide, BCB or silicone dielectrics, which are used in conventional WLPs. This is because the copper conductor is etched to form traces and protected with solder mask and the etching process costs less than electroplating. In addition, wire bonds are used to connect the individual die pads to the copper traces. Encapsulation, solder ball attach and singulation complete the compliant WLP packaging process. Using this approach, Tessera built 9mm x 14mm package demonstrators. To show the feasibility of a low-cost two-metal package, two compliant copper clad layers were laminated in succession and subsequently wire bonded.
KEY WORDS: Low cost, laminated and etched WLP, two-metal WLP, compliant, wire bond
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