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A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps.

A wafer level packaging technique has been developed with an inherent advantage of excellent solder joint co-planarity essential for wafer level test and burn-in. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced by stretching the solder joint to achieve high aspect ratio and small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder joints has been found to be considerably better than that of the conventional spherical-shaped solder bumps.

A cost-effective wafer level packaging technique termed "stretch and break", based on stretching and detachment of solder interconnections, has been established. Excellent co-planarity, essential for wafer level test and burn-in, is inherent in the process. The technique allows the freedom to use solder materials of up to 400/spl deg/C melting temperature for forming the interconnection. The shape of the interconnection can also be easily manipulated for optimum performance. The mechanical and thermal cycling reliabilities of the stretched solder interconnection have been found to be significantly better than those of conventional solder joints.