Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-10-12
2002-07-30
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C361S704000, C174S016300, C174S050510, C029S841000, C029S842000, C029S846000
Reexamination Certificate
active
06425179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to semiconductor integrated circuit packages, and more particularly to methods and apparatus pertaining to the manufacture of flex tape ball grid array packages.
2. Description of the Related Art
Tape ball grid array packages (TBGA's) are an increasingly common form of packaging for integrated circuits. TBGA's comprise a flexible plastic tape comprising a dielectric material, such as Kapton, and a metal pattern (traces) formed on the dielectric material. The metal pattern is connected to bond pads on an integrated circuit. Each of the traces is connected to a solder ball, which serves as the electrical interface between the package and a printed circuit board. In this manner, integrated circuit bond pads in TBGA's are electrically coupled to an appropriate solder ball.
The flexible tape material is relatively thin and therefore allows the entire package to be correspondingly thin and lightweight. These characteristics are beneficial for systems that are portable, such as cellular phones and other handheld electronic devices.
During the assembly of TBG's, due to the thin nature of the flexible tape, the tape must be supported while a die is attached to it. One conventional support structure for a flexable tape comprises, as shown in
FIG. 1
a
, a metal sheet
10
with openings
12
therein, including opening
12
a
. The metal sheet
10
has sprocket holes such as hole
8
that allow it to moved along during the assembly process. For ease of description, the packaging of die will be described will be appreciated that the same process is applied to assembly a plurality of packages, one for each of the openings
12
.
As shown in
FIG. 1
b
, a flexible tape substrate
14
with a top side
13
(see
FIG. 1
c
), to which a die will be attached, and a bottom side
15
, to which solder balls will be attached, is attached to the metal sheet
10
. Specifically, an adhesive is applied to the metal around the periphery of the opening
12
a
and the periphery of the top side
13
is attached to the adhesive. The flexible tape substrate
14
is larger than the opening
12
a
such that, as shown by dotted line in
FIG. 1
c
, the periphery of the top side
13
is covered by the metal sheet
10
when viewed from the top side
13
.
As shown in
FIG. 1
d
, a die
17
is attached to the top side
13
and wire bonds connect bond pads on the die
17
to traces on the top side
13
. After connecting the die to the top side
13
of the tape, and the flexible tape substrate
14
. Solder balls are then attached to the bottom side
15
, of the flexible tape, which also involves heating the metal sheet
10
and the flexible tape substrate
14
. Finally, the flexible tape substrate
14
is removed from the support by scribing around the molding to create an individual package.
The metal sheet
10
has different thermal expansion characteristics in comparison with the flexible tape substrate
14
. This mismatch causes the flexible tape substrate
14
to warp or stretch when the flexible tape substrate
14
and metal sheet
10
are heated together, which occurs during molding and solder ball attach, as described above. Warping and/or stretching of the flexible tape substrate
14
can damage the fine metal traces on the flexible tape substrate
14
and can cause the resulting package to be warped.
It would be desirable to decrease the warping or stretching of a flexible tape substrate.
SUMMARY OF THE INVENTION
The present invention decreases the warping or stretching of a flexible tape substrate. According to the present invention, a method for creating a package for a semiconductor die, the package comprising a flexible tape, comprises the following steps. A support with an opening has a plurality of arms extending through at a portion of the opening. For example, for a square opening, there may be eight arms, two extending from each side of the opening. The arms preferably form a “z” shape or some other shape with a transverse component.
The flexible tape is then attached to the ends of the arms within the opening such that the flexible tape is supported by the arms. A die is attached to the flexible tape, the die is preferably covered with a molding compound, and the die/flexible tape assembly is scribed from the support, thereby creating an individual package.
REFERENCES:
patent: 4649415 (1987-03-01), Herbert
patent: 5330919 (1994-07-01), Westbrook
patent: 5386342 (1995-01-01), Rostoker
patent: 5506756 (1996-04-01), Haley
patent: 5838546 (1998-11-01), Miyoshi
patent: 5844168 (1998-12-01), Schueller
patent: 5888849 (1999-03-01), Johnson
patent: 5901041 (1999-05-01), Davies
patent: 6011694 (2000-01-01), Hirakawa
Chia Chok J.
Low Qwai H.
Ranganathan Ramaswamy
Arbes Carl J.
LSI Logic Corporation
Luedeka Neely & Graham
Smith Sean
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