Delco Electronics Corporation

Curt A Erickson

Ralph Edward Cornell

Aparna Vaidyanthan

A surface mount circuit device (,), such as a flip chip, of the type which is attached to a conductor pattern (,) with solder bump connections (,). The solder bump connections (,) are formed by reflowing solder on shaped input/output pads (,) on the device (,), with the shape of the pads (,) being tailored to favorably affect optimal distribution, shape and height of the solder bump connections (,) following reflow soldering of the device (,) to the conductor pattern (,). The solder bump connections (,) are preferably characterized by a shape that increases the stand-off height of the device (,). The shaped solder bump connections (,) also promote stress relief during thermal cycling, improve mechanical bonding, allow better penetration of cleaning solutions, and improve flow of encapsulation materials between the device (,) and its substrate (,).

Solder bump input/output pad for a surface mount circuit device

A method for forming a solder bump pad (,), and more particularly converting a wire bond pad (,) of a surface-mount IC device (,) to a flip chip solder bump pad (,), such that the IC device (,) can be flip-chip mounted to a substrate. The process generally entails an aluminum wire bond pad (,) on a substrate, with at least a portion of the wire bond pad (,) being exposed through a dielectric layer (,) on the substrate. A nickel layer (,) is then deposited on the portion of the wire bond pad (,) exposed through the dielectric layer (,). The nickel layer (,) is selectively deposited on the exposed portion of the wire bond pad (,) without use of a masking operation, such as by an electroless deposition technique. The nickel layer (,) completely overlies the aluminum wire bond pad (,), and therefore protects the bond pad (,) from oxidation due to exposure. Thereafter, the solder bump pad (,) is formed by depositing a solderable material on the nickel layer (,). The solder bump pad (,) is formed to cover only a limited portion of the nickel layer(,), and its shape is tailored to achieve the required geometric characteristics for a solder bump (,) subsequently formed on the solder bump pad (,).

Flip chip solder bump pad

A method for forming a solder bump pad (22), and more particularly converting a wire bond pad (12) of a surface-mount IC device (10) to a flip chip solder bump pad (22), such that the IC device (10) can be flip-chip mounted to a substrate. The process generally entails an aluminum wire bond pad (12) on a substrate, with at least a portion of the wire bond pad (12) being exposed through a dielectric layer (16) on the substrate. A nickel layer (24) is then deposited on the portion of the wire bond pad (12) exposed through the dielectric layer (16). The nickel layer (24) is selectively deposited on the exposed portion of the wire bond pad (12) without use of a masking operation, such as by an electroless deposition technique. The nickel layer (24) completely overlies the aluminum wire bond pad (12), and therefore protects the bond pad (12) from oxidation due to exposure. Thereafter, the solder bump pad (22) is formed by depositing a solderable material on the nickel layer (24). The solder bump pad (22) is formed to cover only a limited portion of the nickel layer (24), and its shape is tailored to achieve the required geometric characteristics for a solder bump (26) subsequently formed on the solder bump pad (22).

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Carmel, IN, United States of America

Curt A Erickson