Importance

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Abstract

A flip chip is soldered to an array of flexible pillars of compliant dielectric material on a circuit board. Each pillar has an electrically conductive core electrically coupled to the circuit board. The pillars absorb movement due to differences in the coefficient of thermal expansion of the chip and board, and hence reduce the possibility of fatigue failure of the solder joint. The pillars are manufactured by forming a layer of compliant dielectric material on the circuit board, forming blind holes in the layer, filling the holes with electrically conductive material overlapping the edges of the holes, and then laser ablating to remove the compliant dielectric material except where protected by the electrically conductive material.

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First Claim