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The application of no-flow underfills for high IO density, fine-pitch, flip chip in package (FCIP) applications is analyzed. A number of commercially developed no flow underfills are evaluated. Process parameters for improved assembly yields depend strongly on the underfill materials characteristics and particularly the reflow profile. The test vehicles used in this study incorporate high I/O density, large chip size, and small interconnect pitch. This paper presents a methodology for evaluating new commercial no flow underfill materials, techniques for establishing baseline reflow profiles for yielding FCIP devices, and initial yield sensitivity analysis for the FCIP assembly process.