Method for manufacturing a chip scale package having copper traces selectively plated with gold

A method for manufacturing a chip scale package, the method comprising:

• (A) preparing a tape wiring board comprising a strip of polyimide tape having a plurality of copper traces on a bottom surface of the tape, a window through the tape having portions of the copper traces extending across the window, a plurality of connection holes through the tape exposing other portions of the copper traces through the holes, and an elastomer chip carrier on a bottom surface of the tape;
• (B) applying a preflux to the portions of the copper traces exposed through the connection holes;
• (C) plating the copper traces extending across the window with gold (Au) to define beam leads, wherein the preflux prevents the portions of the copper traces exposed through the connection holes from being plated;
• (D) attaching a semiconductor chip to the elastomer beam carrier;
• (E) bonding the gold plated beam leads to the semiconductor chip through the window;
• (F) encapsulating the bonding area between the beam leads and the semiconductor chip;
• and,
• (G) forming a solder bump on each of the portions of the copper traces exposed through the connection holes, such that the solder bump bonds through the preflux to the portions of the copper traces exposed through the connection holes without an intervening gold layer, whereby the formation of gold-solder intermetallic compound at the portions of the copper traces exposed through the connection holes is prevented.

A method for manufacturing a chip-scale package, comprising:

• (A) preparing a tape wiring board comprising a polyimide tape having copper traces on a bottom surface of the tape, a window through the tape having portions of the copper traces extending across the window, a plurality of connection holes in the tape exposing other portions of the copper traces, and an elastomer chip carrier on the bottom surface of the tape;
• (B) attaching to the top surface of the polyimide tape a cover film comprising an adhesive layer, wherein the layer of adhesive on the cover film is an ultraviolet-light-sensitive adhesive that releases its adhesion upon exposure to ultraviolet light;
• (C) plating the portions of the copper traces extending across the window with gold (Au) to define beam leads;
• (D) removing the cover film from the polyimide tape by irradiating the cover film with an ultraviolet light;
• (E) attaching the semiconductor chip to the elastomer;
• (F) bonding the beam leads to the semiconductor chip;
• (G) encapsulating the bonding area between the beam leads and the semiconductor chip;
• and,
• (H) forming a solder bump on each of the solder ball mounting pads.