Leadless packaging process using a conductive substrate

Details Leadless packaging process using a conductive substrate Leadless packaging process using a conductive substrate

2000-03-20

2002-04-16

Everhart, Caridad (Department: 2825)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

C438S110000, C438S124000

Reexamination Certificate

active

06372539

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to the bulk packaging of integrated circuits. More particularly, the invention relates to the use of leadless packaging processes and designs that utilize a conductive substrate.
A leadless leadframe package (LLP) is a relatively new integrated circuit package design that contemplates the use of a metal (typically copper) leadframe type substrate structure in the formation of a chip scale package (CSP). As illustrated in
FIG. 1
, in typical leadless leadframe packages, a copper leadframe strip or panel
101
is patterned (typically by stamping or etching) to define a plurality of arrays
103
of chip substrate features
105
. Each chip substrate feature includes a die attach pad
107
and a plurality of contacts
109
disposed about their associated die attach pad
107
. Very fine tie bars
111
are used to support the die attach pads
107
and contacts
109
.
During assembly, dice are attached to the respective die attach pads and conventional wire bonding is used to electrically couple bond pads on each die to their associated contacts
109
on the leadframe strip
101
. After the wire bonding, a plastic cap is molded over the top surface of the each array
103
of wire bonded dice. The dice are then singulated and tested using conventional sawing and testing techniques.
FIG. 2
illustrates a typical resulting leadless leadframe package. The die attach pad
107
supports a die
120
which is electrically connected to its associated contacts
109
by bonding wires
122
. A plastic cap
125
encapsulates the die
120
and bonding wires
122
and fills the gaps between the die attach pad
107
and the contacts
109
thereby serving to hold the contacts in place. It should be appreciated that during singulation, the tie bars
111
are cut and therefore the only materials holding the contacts
109
in place is the molding material. The resulting packaged chip can then be surface mounted on a printed circuit board or other substrate using conventional techniques.
Although leadless leadframe packaging has proven to be a cost effective packaging arrangement, there are continuing efforts to further improve the package structure and processing to reduce production costs, improve production efficiency and/or improve production yields.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and according to the purpose of the present invention, an improved method of packaging integrated circuits in a leadless package is disclosed. A conductive substrate sheet is initially patterned to form troughs that define a multiplicity of device areas. Each device area includes a plurality of contact landings (and preferably a die attach pad) that are formed in the substrate sheet by patterning. The patterning can be done using a variety of conventional techniques (e.g. etching). A multiplicity of dice are then attached to the substrate sheet and bond pads on the dice are electrically connected to associated contact landings using conventional techniques such as wire bonding. The substrate sheet serves to support the contacts (and die attach pad) during the bonding. One or more caps are then molded over the device areas to encapsulate the dice and bonding wires and to fill the troughs. After the caps have been formed, excess portions of the substrate sheet (e.g. portions below the troughs) are removed to electrically isolate the contact landings thereby forming electrically isolated independent contacts in a molded package. In the resulting arrangement, the molding material serves to hold the contacts in place as well as to electrically isolate the independent contacts.
The excess substrate material can be removed using a variety of techniques including mechanical grinding and chemical etching and/or a combination of the two. It should be appreciated that in the described arrangement, the “excess” substrate material serves to prevent the formation of flash below the contacts during the molding operation. The “excess” substrate material also supports the die attach pad and the contacts during both wire bonding and the die attach process.
In an apparatus aspect of the invention, it is believed that the intermediate patterned substrate sheet is a novel structure and that the matrix based packaging of devices using such a substrate is also new.


REFERENCES:
patent: 3838984 (1974-10-01), Crane et al.
patent: 5367196 (1994-11-01), Mahulikar et al.
patent: 5494207 (1996-02-01), Asanasavest
patent: 5508556 (1996-04-01), Lin
patent: 5580466 (1996-12-01), Tada et al.
patent: 5596231 (1997-01-01), Combs
patent: 5623123 (1997-04-01), Umehara
patent: 5656550 (1997-08-01), Tsuji et al.
patent: 5741729 (1998-04-01), Selna
patent: 5844315 (1998-12-01), Melton et al.
patent: 5854511 (1998-12-01), Shin et al.
patent: 5866948 (1999-02-01), Murakami et al.
patent: 5981314 (1999-11-01), Glenn et al.
patent: 5990545 (1999-11-01), Schueller et al.
patent: 6013946 (2000-01-01), Lee et al.
patent: 6033934 (2000-03-01), Hsieh
patent: 6060774 (2000-05-01), Terui
patent: 6060778 (2000-05-01), Jeong et al.
patent: 6093960 (2000-07-01), Tao et al.
patent: 6133070 (2000-10-01), Yagi et al.
patent: 6177288 (2001-01-01), Takiar
patent: 6182359 (2001-02-01), Nieto
patent: 6188130 (2001-02-01), Ramirez et al.
patent: 2 059 157 (1981-04-01), None
patent: 3-108745 (1991-05-01), None
Leadless Leadframe Package (LLP), National Semiconductor Application Note 1187, Sep. 2000.

Affiliated with

Also associated with

Rating

Leadless packaging process using a conductive substrate does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Leadless packaging process using a conductive substrate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Leadless packaging process using a conductive substrate will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2862290