Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-12-15
2001-02-27
Shoap, Allan N. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S852000, C029S825000, C174S262000
Reexamination Certificate
active
06192579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tape carrier and a manufacturing method thereof. More particularly, the present invention relates to a tape carrier, on the tape base material of which a plurality of metallic wires are formed through an adhesive layer, and in the tape base material of which a plurality of via holes communicated with the metallic wires are formed. Also, the present invention relates to a method of manufacturing the tape carrier.
2. Description of the Related Art
Recently, semiconductor elements such as IC chips are highly integrated and mounted on electronic devices at high density. In accordance with that, various semiconductor devices (tape carrier packages), in which tape carriers are used, have been developed and put into practical use. Concerning the material used for the tape carrier (TCP), three layer tapes are commonly used, on which a layer of copper foil is made to adhere onto an insulating tape base material made of polyimide through an adhesive layer.
Description will be given to a common manufacturing method of BGA (Ball Grid Array) type tape carrier in which the above three layer tape is used. First, in a tape material in which an adhesive layer is formed on a base material made of polyimide, punching to form various openings is conducted so that device holes, outer lead holes, via holes and sprocket holes are formed.
Next, a layer of copper foil is laminated on the side of the tape material, which has been punched and on which the adhesive layer is formed, so that a three layer tape can be formed. The above copper foil is subjected to photolithography of the prior art, and a wiring pattern is formed using the copper foil. The above wiring pattern is subjected to tin plating, solder plating, nickel plating or gold plating. Then, solder balls are put on the via pads exposed to the via holes and reflowed so that the solder bumps are formed. In this way, the tape carrier is manufactured.
In the above method of manufacturing the tape carrier, the tape material is punched. Examples of the punching method are: a punching method conducted by a press, a method of forming holes by means of laser beams, and a method of forming holes by means of etching.
From the viewpoint that the number of manufacturing processes is small and the production cost is low, the punching method conducted by a press is preferably used. In the case of punching a tape material, on the polyimide base material of which the adhesive layer is formed, when punching is conducted from the polyimide base material side, a burr of the adhesive layer is generated. Therefore, punching is commonly conducted from the adhesive layer side to the polyimide base material side.
However, when the tape material
51
is punched from the adhesive layer
52
side in the direction of arrow E, sags are caused on the adhesive layer
52
at the opening edge portion as shown in FIG.
9
. Therefore, the adhesive enters the via hole
53
. When the layer of copper foil
54
is laminated on the adhesive layer
52
under the condition that the sags are generated on the adhesive layer
52
, there is caused a gap
55
between the copper foil
54
and the adhesive layer
52
by the influence of the sags. When the metallic wire
57
including the via pad
56
exposed to the via hole
53
is formed by etching the layer of copper foil
54
as shown in
FIG. 10
, an adhesive area of the via pad
56
is reduced by the sags of the adhesive layer
52
. Accordingly, there is a possibility that the via pad
56
can be peeled off and that the reliability of the package can be deteriorated.
Therefore, for example, when the diameter of the via hole is &phgr;0.200 mm and consideration is given to the sags of the adhesive layer
52
, adhesive region R of the via pad
56
with respect to the tape material
51
must be at least 50 &mgr;m on one side in the radial direction. More preferably, adhesive region R of the via pad
56
with respect to the tape material
51
must be approximately 75 &mgr;m on one side in the radial direction. Unless the above adhesive region R is ensured, it is impossible to maintain the reliability of the package.
As described above, the diameter of the via pad to be joined to the solder ball
58
must be larger than a predetermined value. When the wiring pattern, the wiring pitch of which is made to be fine, is designed, this extended via pad diameter puts a great restriction on the design of the wiring pattern.
In order to join the solder ball
58
to the via pad
56
exposed to the via hole
53
as shown in
FIG. 10
, when consideration is given to the wettability of the solder and the pad surface, it is necessary that the solder ball
58
comes into contact with the via pad
56
. The size of the solder ball
58
is restricted by the via hole diameter, the tape material thickness and the solder ball diameter. In this case, there are two requirements which are incompatible with each other. One requirement is that the via hole diameter tends to be decreased when the pitch of the wiring pattern is made to be fine. The other requirement is that the solder ball diameter is made as large as possible for increasing the height of the solder bump as high as possible when the base board or IC chip
59
is mounted on the solder bump.
In the conventional tape carrier, for example, when the solder ball
58
, the diameter of which is not less than &phgr;0.200 mm, is inserted and jointed to the via hole
53
, the diameter of which is &phgr;0.200 mm, there is a possibility that the solder ball
58
can not be sufficiently joined to the via hole
53
. Actually, it is impossible to join the solder ball
58
to the via hole
53
. When the thickness of the tape material
51
is decreased to as small as possible, the following problems may be encountered. In general, the tape material
51
is in a belt-shape and moves between the reels. While a predetermined tension is given to the tape, it is conveyed. Therefore, when the mechanical strength of the tape material is lowered, it becomes difficult to convey the tape. For the above reasons, thickness of the tape material
51
can be reduced only to 50 &mgr;m.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above technical problems of the prior art. It is an object of the present invention to provide a tape carrier and a manufacturing method thereof characterized in that: the diameter of the via pad is reduced in order to make the pitch of the wiring pattern to be fine, so that the degree of freedom of designing the fine wiring pattern can be enhanced; and the via pad and the metallic ball can be positively joined to each other even if the diameter of the metallic ball is increased to as large as possible.
In order to accomplish the above object, the present invention is composed as follows.
A tape carrier comprises: a metallic wiring formed on one side of a tape base material through an adhesive layer; and a plurality of via holes are formed on the other side of the tape base material, the via pads of the metallic wiring being exposed to bottom portions of the plurality of via holes, wherein internal wall surfaces of the via holes, which have been formed by punching the tape material, on one side of which the adhesive layer is formed, are subjected to a coining press operation from the other side of the tape base material, so that the via holes are formed into tapered holes, the diameters of the opening portions of which are extended.
The tape material is punched from the side on which the adhesive layer is formed, and sags of the adhesive layer into the via holes, which have been formed in the process of punching, may be pushed back and corrected by the coining press tool.
The internal wall surfaces of the via holes are formed by hot setting of the tape base material when ultrasonic vibration is given to the coining press tool when a coining press operation is conducted from the other side of the tape base material.
Metallic bumps may be joined to the via pads exposed to the bottom porti
Hayashi Mamoru
Miyajima Yoshinori
Sato Kiyokazu
Uchida Hirofumi
Pennie & Edmonds LLP
Sands Ronda E
Shinko Electric Industries Co. Ltd.
Shoap Allan N.
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