Leadless plastic chip carrier with standoff contacts and die attach pad
View Patent ↗A process for fabricating a leadless plastic chip carrier includes selectively etching at least a first surface of a leadframe strip to partially define at least a plurality of contact pads and a die attach pad; selectively plating at least one layer of metal on a second surface of the leadframe strip, on an undersurface of at least the plurality of contact pads and the die attach pad; mounting a semiconductor die on the first surface, on the partially defined die attach pad; wire bonding the semiconductor die to ones of the contact pads; encapsulating the wire bonds and the semiconductor die in a molding material such that the molding material covers a first portion of the die attach pad and first portions of the contact pads; selectively etching a second surface of the leadframe strip to define a second portion of the contact pads and a second portion of the die attach pad by etching the second surface with the at least one layer of metal resisting etching; and singulating the leadless plastic chip carrier from the leadframe strip.
1. A process for fabricating a leadless plastic chip carrier, comprising:
selectively etching at least a first surface of a leadframe strip to partially define at least a plurality of contact pads and a die attach pad;
selectively plating at least one layer of metal on a second surface of said leadframe strip, on an undersurface of at least said plurality of contact pads and said die attach pad;
selectively plating at least one layer of metal on said first surface of said leadframe strip including selectively plating said at least one layer of metal on only a peripheral portion of said die attach pad and plating said at least one layer of metal on a surface of said plurality of contact pads for facilitating wire bonding;
mounting a semiconductor die on said first surface, on the partially defined die attach pad;
wire bonding said semiconductor die to ones of said plurality of contact pads;
encapsulating said wire bonds and the semiconductor die in a molding material such that said molding material covers a first portion of said die attach pad and first portions of said plurality of contact pads;
selectively etching a second surface of said leadframe strip to define a second portion of said plurality of contact pads and a second portion of said die attach pad by etching said second surface with said at least one layer of metal resisting etching; and
singulating said leadless plastic chip carrier from said leadframe strip.
2. The process for fabricating a leadless plastic chip carrier according to claim 1 , wherein said selectively plating said at least one layer of metal on said first surface and said selectively plating said at least one layer of metal on said second surface is carried out in a single plating step.
3. The process for fabricating a leadless plastic chip carrier according to claim 1 , further comprising coating all exposed surfaces of said second portion of said die attach pad and said second portion of said plurality of contact pads for oxidation protection.
4. The process for fabricating a leadless plastic chip carrier according to claim 3 wherein coating comprises dipping at least a portion of said leadless plastic chip carrier in at least one of tin, solder dipping, and organic surface protection.
5. The process for fabricating a leadless plastic chip carrier according to claim 1 wherein said at least one layer of metal is selected from the group consisting of a layer of silver, layers of nickel and gold, and layers of nickel and palladium.
6. The process for fabricating a leadless plastic chip carrier according to claim 1 , wherein said step of selectively plating further includes selectively plating a perimeter portion of said leadframe strip for providing package rigidity, said perimeter portion being removed by said singulating.
7. A process for fabricating a leadless plastic chip carrier, comprising:
selectively etching a first surface and a second surface of a leadframe strip to define at least a plurality of contact pads and a die attach pad joined together by remaining portions of metal between etched away portions;
selectively plating at least one layer of metal on said first surface of said leadframe strip and on a second surface of said leadframe strip, on an undersurface of at least said plurality of contact pads and said die attach pad;
mounting a semiconductor die on said first surface, on the die attach pad;
wire bonding said semiconductor die to ones of said plurality of contact pads;
encapsulating said wire bonds and the semiconductor die in a molding material such that said molding material covers a first portion of said die attach pad and first portions of said plurality of contact pads;
further selectively etching to remove said remaining portions of metal between said etched away portions to isolate said plurality of contact pads and said die attach pad; and
singulating said leadless plastic chip carrier from said leadframe strip.
8. The process for fabricating a leadless plastic chip carrier according to claim 7 , further comprising coating a second portion of said die attach pad and a second portion of said plurality of contact pads for oxidation protection.
9. The process for fabricating a leadless plastic chip carrier according to claim 8 , wherein coating comprises dipping at least a portion of said leadless plastic chip carrier in an organic surface protection material.
10. The process for fabricating a leadless plastic chip carrier according to claim 7 wherein said at least one layer of metal is selected from the group consisting of a layer of silver, layers of nickel and gold, and layers of nickel and palladium.
11. The process for fabricating a leadless plastic chip carrier according to claim 7 , wherein said step of selectively plating further includes selectively plating a perimeter portion of said leadframe strip for providing package rigidity, said perimeter portion being removed by said singulating.