Electroformed and chemical milled bumped tape process

Claim 2

A process for producing bumped lead frae tape comprising the preliminary steps of: (a) laminating a metaI foil sheet on a first side and a second side with a photoresist; (b) simultaneously exposing said first side to an image of bumps and said second side to an image of leads; (c) developing said image of bumps to expose a plurality of bump openings while protecting said photoresist on said second side from being developed; (d) cleaning those parts of said metal foil sheet exposed in said bump openings; and (e) electroforming metal bumps on said metal sheet in said bump openings to a predetermined height.

Claim 3

The process of claim 1 further including the subsequent steps of: (f) developing said lead image on said second side of said sheet; (g) chemically milling exposed parts of said metal sheet on said second side with an etchant while protecting said first side from contact with said etchant, for a time sufficient to form a plurality of bumped leads; (h) removing any remaining said photoresist from said first and second sides to leave a bumped tape; and (i) activating said bumped tape with a solution of sodium persulfate.

Claim 4

The process of claim 2 further including the step of overplating said bumped tape with a second metal.

Claim 5

The process of claim 3 wherein step e) comprises using a double-cell electroplating apparatus having a relatively high-impedance ion path interconnecting the cells.

Claim 6

The process of claim 4 wherein said metal foil is copper and said second metal comprises gold.

Claim 7

The process of claim 4 wherein said predetermined height is not less than 0.0013 inch.

Claim 8

The process of claim 3 wherein said overplating is done to a thickness of greater than 0.0001 inch.

Claim 9

The process of claim 4 wherein the cleaning step includes washing with sodium persulfate.

Claim 10

A process for manufacturing a bumped lead tape comprising the steps of: (a) laminating both sides of a copper foil with dry film photoresist to form a panel; (b) exposing said photoresist material on one side of said panel to light in accordance with a desired lead pattern and exposing the photoresist material on an opposite side of said panel to light in accordance with a desired bump pattern; (c) baking said panel at 70° C. for about five minutes; (d) developing said photoresist to expose said desired bump pattern while protecting said lead pattern from development; (e) baking said panel at 70° C. for about five minutes; ( f) inspecting said bump holes at the base thereof for traces of developer and removing any which are found; (g) connecting said panel as the cathode in one cell of a double-cell electroplating apparatus having a relatively high-impedance ion path connecting the two cells; (h) supplying current through said double-cell electroplating apparatus for a length of time sufficient to electroform copper bumps having a height greater than or equal to 0.0013 inch in said bump holes; (i) developing said desired lead pattern on said one side of said panel while protecting said opposite side of said panel; (j) masking said opposite side of said panel to prevent contact of an etchant with said bumps; (k) chemically milling said copper sheet until a plurality of bumped leads remain; (i) unmasking said one side of said panel containing said bumps; (m) stripping said dry film photoresist to leave a bumped tape; and (n) activating the surface of said bumped tape with sodium persulfate.

Claim 11

A process for manufacturing a bumped lead tape comprising the steps of: (a) laminating both sides of a copper foil with dry film photoresist to form a panel; (b) exposing said photoresist material on one side of said panel to light in accordance with a desired lead pattern and exposing the photoresist material on an opposite side of said panel to light in accordance with a desired bump pattern; (c) baking said panel at 70° C. for about five minutes; (d) developing said photoresist to expose said desired bump pattern while protecting said lead pattern from development; (e) baking said panel at 70° C. for about five minutes; ( f) inspecting said bump holes at the base thereof for traces of developer and removing any which are found; (g) connecting said panel as the cathode in one cell of a double-cell electroplating apparatus having a relatively high-impedance ion path connecting the two cells; (h) supplying current through said double-cell electroplating apparatus for a length of time sufficient to electroform copper bumps having a height greater than or equal to 0.0013 inch in said bump holes; (i) developing said desired lead pattern on said one side of said panel while protecting said opposite side of said panel; (j) masking said opposite side of said panel to prevent contact of an etchant with said bumps; (k) chemically milling said copper sheet until a plurality of bumped leads remain; (i) unmasking said one side of said panel containing said bumps; (m) stripping said dry film photoresist to leave a bumped tape; and (n) activating the surface of said bumped tape with sodium persulfate.

Claim 12

The process of claim 9 further including the step of plating said bumped tape with gold to a thickness greater than 0.0001 inch.

Claim 13

The process of claim 9 further comprising the following steps to produce a semiconductor die electrically coupled to a substrate: (o) bonding said leads to a semiconductor die; (p) forming said leads and cutting them to produce a plurality of free ends; and (q) bonding said free ends to said substrate.

Claim 14

The process of claim 11 wherein said bonding is achieved by thermocompression.