US 7,598,122 B1Granted

Die attach method and microarray leadframe structure

AssigneeNational Semiconductor Corporation

InventorsJaime A. Bayan, Nghia Thuc Tu, Lim Fong, Chan Peng Yeen

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Abstract

In one aspect of the invention, a method of attaching a semiconductor die to a microarray leadframe is described. The method comprises stamping an adhesive onto discrete areas of the microarray leadframe using a multi-pronged stamp tool. The adhesive is applied to the leadframe as a series of dots, each dot corresponding to an associated prong of the stamping tool. In some embodiments the adhesive used to attach the semiconductor die to a leadframe is a black epoxy based adhesive material. In an apparatus aspect of the invention, lead traces in a microarray leadframe are arranged to have tails that extend beyond their associated contact posts on the side of the contact post that is opposite a wire bonding region such that such lead traces extends on two opposing sides of their associated contact posts. The tails do not attach to other structures within the lead frame (such as a die attach structure). The width of at least some of these tailed lead traces in a region that overlies their associated contact post is narrower than their associated contact post. Thus, these narrowed lead traces have extensions that extend beyond their associated contact posts. The extensions provide additional surface area that gives an adhesive applied to the narrowed lead trace (as for example by stamping) room to bleed (flow) along the top surface of the lead trace on both sides of the associated contact pad.

Claims5

Dependent claims

A method of packaging a semiconductor die using a microarray leadframe having an array of contact posts suitable for forming contact pads, a die attach structure and a plurality of lead traces, the posts being arranged in a plurality of rows and each lead trace being integrally formed with an associated contact post and the die attach structure being integrally formed with at least one associated contact post, the method comprising:

stamping an adhesive onto discrete areas of the microarray leadframe using a multi-pronged stamp tool, wherein the adhesive is applied to a surface of the microarray leadframe that faces away from bottom surfaces of the contact posts as a series of dots, each dot corresponding to an associated prong of the stamping tool, wherein at least some of the adhesive dots are placed on lead trace portions of the microarray leadframe and at least some other of the adhesive dots are placed on the die attach structure of the microarray leadframe and wherein no prong of the stamping tool applies more than one adhesive dot;
attaching a die to the microarray leadframe using the adhesive;
electrically connecting the die to the leadframe;
and
forming an encapsulant cap over the leadframe and die while leaving bottom, surfaces of the contact posts exposed to provide electrical contacts for the packaged die, wherein the encapsulant cap is formed such that encapsulant material is exposed on a bottom surface of the package between the exposed contact posts;
wherein:
top surfaces of the lead traces are substantially co-planar with a top surface of the leadframe;
bottom surfaces of the lead traces are recessed relative to a bottom surface of the leadframe;
bottom surfaces of the contact posts are substantially co-planar with the bottom surface of the leadframe;
and
wherein at least some of the lead traces extend beyond their associated contact posts on two opposing sides of their associated contact posts and have a width in an overlying region of their associated contact post that is narrower than their associated contact post.

8 more elements

A method of packaging a plurality of semiconductor dice using a microarray leadframe panel having a plurality of device areas, each device area including an array of contact posts suitable for forming contact pads, and a plurality of lead traces, the posts being arranged in a plurality of rows and each lead trace being integrally formed with an associated contact post, the method comprising:

stamping an adhesive onto discrete areas of at least one device area using a multi-pronged stamp tool;
repeating the stamping operation until an adhesive has been applied to each of the device areas, wherein with each stamping operation, the adhesive is applied to the leadframe in a series of dots, each dot corresponding to an associated prong of the stamping tool, wherein at least some of the adhesive dots are placed on lead trace portions of the leadframe and wherein no prong of the stamping tool simultaneously applies more than one adhesive dot in any one stamping operation;
attaching a selected die to a selected device area of the leadframe using the corresponding adhesive to secure the die to the leadframe;
repeating the attaching operation until a die has been attached to each device area;
electrically connecting the dice to the leadframe;
and
forming at least one encapsulant cap over the leadframe and dice while leaving bottom surfaces of the contact posts exposed to provide electrical contacts for the packaged dice, wherein the at least one encapsulant cap is formed such that encapsulant material is exposed on a bottom surface of the package between the exposed contact posts;
wherein:
top surfaces of the lead traces are substantially co-planar with a top surface of the leadframe;
bottom surfaces of the lead traces are recessed relative to a bottom surface of the leadframe;
bottom surfaces of the contact posts are substantially co-planar with the bottom surface of the leadframe;
and
wherein at least some of the lead traces extend beyond their associated contact posts on two opposing sides of their associated contact posts and have a width in an overlying region of their associated contact post that is narrower than their associated contact post.

10 more elements

Dependencies are inferred from the claim text.