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New technologies of structure, materials an encapsulating process for over-coated flip-chip chip scale package (OFCSP) have been developed in this study. A MAP (matrix array package) type flip chip package with over-coating is developed by simultaneous encapsulating process which has the same universal production system as mini-BGA and doesn't need to change molding facility due to die shrink or product changed. A 4×4 chips are array flip chip test vehicle was designed for this study. The new technology shows many advantages such as: high electric performance, low cost, good reliability property, high throughput, thinner package, and void free during encapsulating process. Not only remarkable down-sizing, but also a new developed package shows miraculous property of soldering resistance. OFSCP is developed by vacuum molding for simultaneous encapsulating process without void remain, and fine filler molding compounds for underfilling penetration well. According to failure analysis, internal stress on the die surface around solder bump will cause the package circuit-opened failure. OFCSP shows the smallest stress concentrated on the die surface from FEM (finite element model) analysis. It can pass perfectly pre-conditioned level 1 JEDEC standard at 230°C reflowing and level 2 JEDEC standard at 260°C reflowing. It can also pass the reliability testing items including USPCT, TCT and HST after pre-condition of JEDEC level 3. Since the perfect property of soldering resistance can be achieved by considering package structure, encapsulant properties and process, developed technology in this study can be applied for more advanced package such as paper-thin package, FC/WB embedded stacked package etc.