Partial plating system

Details Partial plating system Partial plating system

2001-04-24

2003-12-02

Crispino, Richard (Department: 1734)

Coating apparatus

Projection or spray type

With mask or stencil

C118S305000, C118S505000, C438S942000

Reexamination Certificate

active

06656275

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a partial plating system, more particularly relates to a technique useful for partial plating of a TAB tape and a lead frame.
2. Description of the Related Art
In recent years, along with the increasing compactness demanded for electronic apparatuses, the semiconductor packages for mounting in the electronic apparatuses have been made smaller in size. One type of such compacter semiconductor package is the tape carrier package (TCP). A TCP consists of a polyimide film or other support on which copper foil leads are formed. The copper foil leads and the terminals of the semiconductor devices are bonded together, then the entire assembly is sealed by a resin.
FIG. 13A
is a plan view of part of a polyimide film on which such copper foil leads are formed. As shown in
FIG. 13A
, a plurality of copper foil leads
102
,
102
. . . are formed on the polyimide film
101
. Below, the polyimide film
101
on which the plurality of copper foil leads
102
,
102
. . . are formed will be referred to as a tape automated bonding (TAB) tape
106
.
FIG. 133
is an enlarged view of such a copper foil lead. As shown here, the copper foil lead
102
is comprised of an inner lead
102
a
, an outer lead
102
b
, a test pad
102
c
, and parts connecting the same.
Among these, the inner lead
102
a
projects out toward the inside of a device hole
104
formed in the polyimide film
101
. On the other hand, the outer lead
102
b
is formed at a position corresponding to a window hole
105
formed in the polyimide film
101
.
The TAB tape
106
formed in this way is connected with an LSI or other semiconductor device (not shown) by inner lead bonding. In this inner lead bonding, the bumps (not shown) of the semiconductor device and the inner leads
102
a
are hot pressed together for electrical connection of the bumps and inner leads
102
a
. After mounting the semiconductor device in this way, the semiconductor device and the polyimide film
101
at the portion inside from the window holes
105
are sealed by a resin.
When the bumps of the semiconductor device are made of gold, however, it is preferable that the portions of the inner leads
102
a
to be hot pressed with the gold bumps be gold plated. This is because if they are gold plated, the gold plating and the gold contained in the gold bumps fuse with each other and improve the reliability of connection of the inner leads
102
a
and the gold bumps. Therefore, the general practice has been to gold plate the copper foil leads
102
after forming the copper foil leads
102
on the polyimide film
101
.
Next, an explanation will be given, with reference to
FIG. 15
, of a plating system of the related art used in such a plating process.
FIG. 15
is a perspective view of an entire plating system according to the related art. The plating system
107
of the related art is comprised of a sparger tank
108
, a nozzle
109
provided inside the same, and an anodic plate
110
. The TAB tape
106
is transported toward the transport direction shown by the arrow in the figure by driving of a roller (not shown) engaged with sprocket holes
103
,
103
. . . (see
FIG. 13A
) formed in the polyimide film
101
. The TAB tape
106
is transported in a state held with its surface in the vertical plane (called “vertical transport” hereinafter). Note that the sparger tank
108
is formed with slits
108
a
,
108
a
at the portion where the TAB tape
106
is fed in and the portion where it is fed out.
When a TAB tape
106
is transported to the plating system
107
, a plating solution is sprayed from the nozzle
109
to fill the inside of the sparger tank
108
with the plating solution. If current is sent to the copper foil leads
102
and the anodic plate
110
in this state using the copper foil leads
102
of the TAB tape
106
as cathodes, the copper foil leads
102
will be gold plated.
As explained above, however, the portions which require the gold plating in the copper foil leads
102
are the inner leads
102
a
. The rest of the portions do not require gold plating. According to the plating system of the related art, however, all of the portions of the copper foil leads
102
to which current was supplied end up being gold plated. If portions other than those requiring it are gold plated in this way, the expensive gold is used wastefully and the problem arises of a higher cost of the plating process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a partial plating system able to gold plate only the inner leads of a TAB tape.
To achieve the above object, according to a first aspect of the present invention, there is provided a partial plating system provided with a mask having an opening formed to correspond to a plating region of a TAB tape and provided horizontally; an elevating means for lowering the TAB tape toward the mask; and a pressing means for pressing the TAB tape on to the mask; a plating solution being sprayed from below the opening toward the opening to plate the plating region.
According to a second aspect of the invention, there is provided a partial plating system of the first aspect of the invention wherein the mask is provided on its surface with guide pins for engagement with engagement holes of the TAB tape and is placed on a base member so as to be able to slide in a horizontal plane around a predetermined reference position.
According to a third aspect of the invention, there is provided a partial plating system of the second aspect of the invention wherein a biasing member is provided between the elevating means and the base member and wherein the elevating means is biased to move away from the base member.
According to a fourth aspect of the invention, there is provided a partial plating system of any one of the first to third aspects of the invention further provided with a feeding means for transporting the TAB tape in a longitudinal direction by exactly a predetermined length after the partial plating system plates a certain length of the TAB tape in one plating operation.
According to a fifth aspect of the invention, there is provided a partial plating system of any of the first to fourth aspects of the invention wherein the elevating means is provided with a guiding means for use when the TAB tape is being transported in the longitudinal direction.
Next, the mode of operation of the present invention will be explained.
According to the partial plating system of the present invention, provision is made of a mask having an opening formed corresponding to the plating region of the TAB tape and provided horizontally. The TAB tape is lowered by the elevating means toward the mask, then is pressed against the mask by the pressing means, so the tape is pressed against the mask in a state with its surface held in the horizontal plane.
In the state pressed against the mask in this way, the plating region of the TAB tape is exposed from the opening. If the plating solution is sprayed from below the opening toward the opening in this state, the exposed plating region will be plated. At this time, since the portions of the TAB tape other than the plating region are covered by the mask, those portions will not be plated. Therefore, by recycling, the gold or other precious metals in the plating solution will not be used wastefully and the cost of the plating process can be reduced.
Further, by placing the mask horizontally and holding the TAB tape in the horizontal plane, the TAB tape is plated to a uniform thickness. That is, if the TAB tape is held in the horizontal plane, the plating solution will not flow over the surface of the plating solution after being sprayed. The amount of the plating solution deposited will become uniform and the plating thickness will therefore become uniform.
Further, according to the partial plating system of another aspect of the invention, guide pins for engagement with engagement holes of the TAB tape are provided on the surface of the mask. In this case, the mask is placed on a base member

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