Perfect molding challenges and the limitations

As today's market requirement on semiconductor product qualities has risen to a very high level, the control in manufacturing of semiconductor has becoming very demanding. In this paper, the unwanted molding defects of voids, incomplete fills, and piping holes are thoroughly investigated. Four areas of focuses: 1) Potential mold flow weakness; 2) Temperature control sensitivity; 3) Pressure effects; and 4) Mold tool cleanliness influence are defined. The in-depth understanding of mold flow in the High Density(HD) LF design is gained through mold flow numerical tool. The numerical model prediction is verified using short shots and end-of-line auto vision data. The key controllable parameters of temperature, pressure, transfer profile, and cleaning of the molding influences on molding quality are thoroughly assessed and examined. Resulted from these defects, the long term impact on the product reliability in the field is also assessed. A systematic methodology is developed and formulated to understand the process and equipment build-in capability from two different equipment manufacturers. The cleanliness of mold tool, which can affect mold flow is maximize through control of vacuum suction and duration, vacuum head design, and mold brush detection. The sizes of the void are minimized through transfer pressure optimization. The complex temperature controller on one of the systems is analyzed and its control is established to improve the compound flow viscosity. Empirically, the process limitations are investigated and transfer profiles are optimized to change the melt front to move the molding defects to non-critical location so that the void will not form at the 500um diameter bonded wire loop peak. The verification of potential negative effects resulted to changes to improve voids, incomplete fills and piping holes are also included in this study. Upfront analysis by adopting numerical tool to understand the existing design and improvement options are proven to be useful.