Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
1999-12-30
2001-06-19
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S106000, C438S111000, C438S584000, C257S666000, C257S684000, C257S692000
Reexamination Certificate
active
06248615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wiring patterned film and its production. Specifically, the invention relates to a wiring patterned film and its production wherein a gold lead which extends from a wiring pattern formed on the adhesive side of a resin film adhered to the side of a semiconductor element on which an electrode terminal is formed, and which bridges a window section opening on the resin film, is cut off at a prescribed location facing the window section and is bent so that the lead tip is connected to the electrode terminal.
2. Description of the Related Art
In recent years, practical applications of chip size packages, such as that shown in
FIG. 3
, which are small and can be made with small mounting areas, are being attempted as semiconductor devices built into portable electronic devices such as cellular phones (see, for example, WO 94/03036).
This type of chip size package has a wire patterned film
11
(hereunder sometimes referred to simply as “film
11
”), consisting of a wiring pattern
14
formed on one side of a resin film
16
, on one side of a semiconductor element
10
on which is formed an electrode terminal
20
around the edges, and adhered at a region inward from the region where the electrode terminal
20
is formed, via an elastomer layer
12
which is an elastic resin layer. The film
11
has a smaller area than the side of the semiconductor element
10
on which it is adhered, and a lead made of gold (hereunder referred to as “gold lead”)
18
extends from one end of the wiring pattern
14
consisting of a gold layer and copper layer formed on the adhesion side with the elastomer layer
12
, to the outer edge of the resin film
16
.
This gold lead
18
is bent so that the lead tip is connected to the electrode terminal
20
of the semiconductor element
10
while it is sealed, together with the electrode terminal
20
etc., by a sealing resin
22
.
Also, at an opening
23
which reaches the back side surface at the other end of the wiring pattern
14
formed on the resin film
16
, there is provided a bump
24
, as an external connection terminal, formed by a plated or soldered ball or the like.
The film
11
is manufactured by the process illustrated in
FIGS. 4A
to
4
F. In these illustrations, a copper foil
32
attached to one side of a resin film
16
is coated with an organic polymer resist layer
34
(hereunder sometimes to be referred to simply as “resist layer
34
”) and subjected to light exposure and development, so as to expose the portion of the copper foil
32
on which the wiring pattern
14
and gold lead
18
are to be formed (
FIGS. 4A
,
4
B). The exposed areas of the copper foil
32
are coated with an electrolytic gold plating to form gold plated sections
36
(FIG.
4
C).
Also, after the coated resist layer
34
is removed and window sections
23
,
23
are formed, which expose the back side of the copper foil
32
at prescribed locations on the other side of the resin film
16
, bumps
24
are formed by electrolytic nickel plating (FIG.
4
D). The opposite side of the resin film
16
is covered with a mask at this time.
Next, the sections of the resin film
16
on which the gold leads
18
are to be formed are removed by laser light, to form gold lead-formed sections
38
where the back side of the copper foil
32
is exposed (FIG.
4
E).
Then, by using chemical etching or the like on the gold lead-formed sections
38
to remove the copper foil
32
where the back side is to be exposed, it is possible to form wiring patterns
14
and gold leads
18
(FIG.
4
F). In this step, the copper foil
32
where the back side is exposed is removed at the gold lead-formed sections
38
, forming window sections
40
bridged by the gold leads
18
consisting of only the gold layer.
Thus, for each wiring pattern
14
and gold lead
18
which are formed in connection, the wiring pattern
14
consists of a double layer of a copper layer and gold layer, while the gold lead
18
consists of only the gold layer. The gold lead
18
can therefore be easily bent.
In the step shown in
FIG. 4F
, the copper foil
32
is also simultaneously removed on the other side of the resin film
16
so that the wiring pattern
14
is not formed there.
To manufacture of a semiconductor device using a wiring patterned film
11
on which such a wiring pattern
14
and gold lead
18
are formed, an elastomer layer
12
is used to connect the side of the resin film
16
on which the wiring pattern
14
is formed to the side of the semiconductor device
10
on which the electrode terminal is formed.
Next, the gold lead
18
bridging the window section
40
is cut at a prescribed location and bent with a bonder (not shown), while the lead tip of the gold lead
18
which has been cut is connected to the electrode terminal
20
of the semiconductor device
10
, after which the gold lead
18
and electrode terminal
20
are sealed with a sealing resin
22
.
Incidentally, notches
42
are formed at prescribed locations on each of the gold leads
18
as shown in
FIG. 5
, in order to facilitate cutting of the gold lead
18
when the gold lead
18
bridging the window section
40
is cut.
In this type of conventional wiring patterned film
11
, it is necessary to form the notches
42
to a minimum prescribed depth in the widthwise direction of the gold leads
18
in order to ensure satisfactory cutting of the gold leads
18
.
However, because deeper notches
42
are more difficult to form and reduce the mechanical strength of the gold leads
18
, the notches
42
must by necessity be made shallow. This in turn reduces the cuttability of the gold leads
18
.
In addition, when the gold leads
18
are fine as in the case of high-density gold leads
18
required for highly integrated semiconductor elements
10
, the depth of the notches
42
must be made even more shallow.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a wiring patterned film and its production process, whereby notches can be easily formed at the prescribed locations of the gold leads bridging the window sections open on the resin film, and whereby the gold leads can be easily cut at the prescribed locations, as well as a gold plating solution which can be used for this process.
With the goal of overcoming the problems described above, the present inventors first made microscopic observations of lead portions A where the notch sections
42
are formed at their narrowest, as shown in
FIG. 5
, and have found that in a conventional film
11
, the surface opposite the flat back side which faces the window section
40
at the lead portion where the notch section
42
is formed at its narrowest has a flat board-like shape, as shown in
FIG. 6
, and that the lateral cross-sectional shape of the lead portion is rectangular, as shown in FIG.
7
. It was also found that at the notch section
42
of the gold leads
18
shown in FIG.
6
and
FIG. 7
, the notch depth in the widthwise direction of the gold lead
18
of the notch section
42
and its cuttability are in a proportional relationship.
Thus, as a result of much research on shapes at the narrowest parts of notch sections of gold lead portions in order to achieve improved cuttability of the leads, the present inventors completed the invention upon finding that if the lateral cross-sectional shape of a lead portion, at which the notch section is formed at its narrowest, has a semicylindrical shape, its cuttability may be improved compared to a gold lead wherein the lateral cross-sectional shape of the lead portion is rectangular, and also that a gold lead wherein the lead portion at which the notch section is formed at its narrowest has a semicylindrical lateral cross-sectional shape can be easily formed by electrolytic plating by the application of a pulse waveform plating current to a gold plating solution containing substantially no grain refiner.
In other words, the present invention provides a wiring patterned film wherein a gold lead which extends from a wiring pa
Chaudhari Chandra
Kilday Lisa
Pennie & Edmonds LLP
Shinko Electric Industries Co. Ltd.
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