LEAD FRAME WITH COINED INNER LEADS
A lead frame used in semiconductor packaging has an outer dam bar and inner leads that extend away from the dam bar. The inner leads have distal ends and tips at the distal ends. Each inner lead has a coined area on a first major surface at the distal end and spaced from the tip. The coined area and the spacing of the coined area from the tip form a shoulder structure. The coined area is configured to receive one end of a bond wire that interconnects the inner lead with a wire bond pad of a semiconductor die. The shoulder structure creates a molding compound locking mechanism to reduce shear stress and delamination in the lead bonding area.
1 . A lead frame for a semiconductor device, the lead frame comprising:
a generally rectangular outer dam bar; and
a plurality of inner leads extending from the dam bar, the inner leads having distal ends spaced from the dam bar, each of the distal ends having a tip, wherein a first major surface of each inner lead includes a coined area at said distal end, said coined area being spaced from said tip by a predetermined distance, and wherein spacing said coined area from said distal end forms a shoulder area at said distal end.
2 . The lead frame of claim 1 , wherein said predetermined distance is between 0.20 mm and 2.0 mm from said tip.
3 . The lead frame of claim 1 , wherein said coined area has a depth of between 0.03 mm and 0.12 mm
4 . The lead frame of claim 1 , wherein said coined area has a depth of up to about half of a thickness of the inner lead.
5 . The lead frame of claim 1 , wherein said coined area is plated with a metal or metal alloy that allows for a strong bond with a bond wire.
6 . The lead frame of claim 5 , wherein the lead frame is formed of Copper, said coined area is plated with Silver, and the shoulder area of the inner lead is unplated.
7 . The lead frame of claim 1 , further comprising a die bond pad located at a generally central area of the lead frame and within a perimeter formed by the dam bar and the inner leads, wherein the tips of the inner leads are spaced from the die bond pad.
8 . The lead frame of claim 7 , wherein the die bond pad is attached to the dam bar with a tie bar.
9 . An integrated circuit device, comprising:
a semiconductor die having a plurality of die wire bond pads formed on a surface thereof;
a plurality of inner leads spaced from and surrounding said semiconductor die, said inner leads having a tip that is proximate to said semiconductor die, wherein a first major surface of said inner leads includes a coined area, said coined area being spaced from said tip by a predetermined distance, wherein spacing said coined areas from said tips forms shoulder areas on said inner leads;
a plurality of bond wires connecting the die wire bond pads with respective ones of said inner leads, wherein one end of each of said bond wires is attached to said coined areas and the other end of each of said bond wires is attached to a respective one of said die wire bond pads; and
an encapsulation material covering said die, said bond wires and said coined areas.
10 . The integrated circuit device of claim 9 , wherein said predetermined distance is between about 0.20 mm to 2.0 mm from said tip.
11 . The integrated circuit device of claim 9 , where said coined area has a depth of between 0.03 mm and 0.12 mm.
12 . The integrated circuit device of claim 11 , wherein said coined area is plated.
13 . The integrated circuit device of claim 12 , wherein the shoulder area of the inner lead is unplated.
14 . The integrated circuit device of claim 9 , wherein said inner leads are formed of Copper, the wires are formed of Gold and said coined area is plated with Silver.
15 . The integrated circuit device of claim 9 , further comprising a die bond pad upon which the semiconductor die is mounted.
16 . A lead frame for a semiconductor device, the lead frame comprising:
a generally rectangular outer dam bar; and
a plurality of inner leads extending from the dam bar, the inner leads having distal ends spaced from the dam bar, each distal end having a tip, wherein the first major surface of each inner lead includes a coined area at said distal end, said coined area being spaced from said tip by a predetermined distance of between 0.20 mm and 2.00 mm, and having a depth of between 0.03 mm and 0.12 mm, and
wherein the lead frame is formed of Copper, said coined area is plated with Silver, and said inner lead tip is bare.