Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Reexamination Certificate
2002-03-13
2004-03-16
Nhu, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
C257S787000
Reexamination Certificate
active
06707158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a method for producing the same, and an anisotropic conductive circuit board. In particular, the present invention relates to a semiconductor device employing a circuit board including a bonding pad portion on which a semiconductor element is to be mounted on its upper surface and electrode pads connected to electrode terminals of the semiconductor element via a connecting member, and a method for producing such a semiconductor device, and relates to a semiconductor device having good electrical and thermal characteristics and a method for producing such a semiconductor device.
2. Description of Related Art
Hereinafter, a semiconductor device employing a commonly used printed circuit board used as a component of a semiconductor package will be described.
FIGS. 8A
to
8
E are views illustrating the production process of a conventional LGA (lard grid array) type semiconductor device in the order of the production.
FIG. 8A
is a plan view,
FIGS. 8B
to
8
E are cross-sectional views of a relevant part taken along line A-A
1
of FIG.
8
A.
First, to produce a printed circuit board as shown in
FIG. 8A
, an insulating substrate
2
to which copper foils having a thickness of 6 to 35 &mgr;m are attached to its upper and lower surfaces is prepared. This insulating substrate
2
is a substrate in which glass fabrics have been incorporated into an epoxy resin.
Next, via holes are formed having a predetermine diameter in predetermined positions of the insulating substrate with a drill or a laser. Then, thick copper films are formed on the side walls of the formed via holes by electroless plating or electrolytic plating. At this point, the copper foils on the upper and the lower surfaces of the insulating substrate are connected by the thick copper films.
Next, dry films are attached onto the surfaces of the copper foils on the upper and the lower surfaces of the insulating substrate by heating and pressing. The dry films are made of a material that causes a reaction with respect to light having a specific wavelength, and the surfaces of the dry films are irradiated with light having a wavelength for a reaction via a photomask on which a predetermined circuit pattern has been formed. Thereafter, in the circuit pattern formed on the dry films on the copper foil surface on the upper and the lower surfaces of the insulating substrate, the portions to be removed of the dry films are dissolved with a developer and removed after exposure to the light. Then, after the removal, the dry films are heated or irradiated with ultraviolet rays so that the remaining portions of the dry films are cured. Using these dry films as masks, exposed copper film portion is removed by allowing the copper foil erosion chemicals such as nitric acid, sulfuric acid or hydrochloric acid to be in contact with the surface of the copper foils, for example, by dipping or spraying.
Finally, the dry films that have been exposed to the chemicals and cured are removed by using a detaching agent, dissolving it in oxygen plasma, or converting it to carbon dioxide. Solder resist films are formed on the upper and the lower surfaces of the thus obtained printed circuit board
1
by screen printing, and the pattern is formed on the solder resist film via a photomask by an exposure machine. Then, the portion to be dissolved of the solder resist film is dissolved with a developer and removed, and then heated and cured. Then, nickel and gold are deposited in this order in predetermined thicknesses by electrolytic plating on the surface of the copper foil portion corresponding to the opening of the pattern from which the solder resist film is removed. Thereafter, the printed circuit board is divided so as to form a frame shape or divided into individual segments by stamping with a pressing machine or a cutting machine.
The printed circuit board
1
for use in a conventional board structure package, which includes bonding pads, electrode pads, and through-holes connecting the bonding pads and the electrode pads on the upper surface to those on the lower surface, has been produced in this manner.
As shown in
FIG. 8A
, on each of the upper and the lower surfaces of the insulating substrate
2
, the produced printed circuit board
1
includes a bonding pad
3
, electrode pads
4
and through-holes
6
connecting the pads
3
and
4
on the upper surface to the corresponding pads on the lower surface. The surface of each of the pads on the printed circuit board
1
is coated with a thin film made of gold or silver. The bonding pad
3
consists of the upper bonding pad and the lower bonding pad, and the electrode pad
4
consists of the upper electrode pad and the lower electrode pad. A solder resist film
5
is formed on the substrate in such a manner that the pads
3
and
4
are exposed.
Next, referring to
8
A to
8
E, a method for producing a semiconductor device (for a LGA type package) including the printed circuit board
1
will be described below.
First, the circuit board
1
as shown in
FIG. 8A
is prepared. In the prepared circuit board
1
, as shown in
FIG. 8B
, an upper bonding pad
3
a,
a lower bonding pad
3
b,
upper electrode pads
4
a,
and lower electrode pads
4
b
are formed on an insulating substrate
2
, and through-holes
6
for connecting the bonding pads
3
a
and
3
b
and the electrode pads
4
a
and
4
b
on the upper surface of the substrate to the corresponding pads on the lower surface are provided.
Then, as shown in
FIG. 8C
, a die bonding process is performed, in which a semiconductor element
7
is attached onto the upper bonding pad
3
a
with a conductive adhesive
8
such as silver paste, and then heating is performed at 150° C. for one hour in the air for strong adhesion.
Then, as shown in
FIG. 8D
, a wire bonding process is performed, in which electrode terminals (not shown) on the semiconductor element
7
mounted on the substrate are connected to the upper electrode pads
4
a
with connecting members
9
such as metal fine lines (wires) using a wire bonder. This connection is performed under the following conditions: The heating temperature of the printed circuit board
1
is 200° C., the load for connection between the connecting members
9
and the electrode terminals of the semiconductor element
7
is 20 gf, and the load for connection between the connecting members
9
and the upper electrode pads
4
a
on the printed circuit board
1
is 100 gf. This connection is performed using ultrasonic vibration as well.
Next, as shown in
FIG. 8E
, an outline molding process is performed, in which a sealing resin
10
is molded to a predetermined package outline with a transfer mold or a print sealing so that the semiconductor element
7
and the connecting members
9
provided on the upper surface of the printed circuit board
1
are sealed and formed into one piece.
In this manner, a semiconductor device for an LGA type package including a conventionally commonly used printed circuit board as a component is produced. Furthermore, if metal ball terminals are provided on the lower electrode pads
4
b
(land portions) on the bottom surface of the printed circuit board
1
, a BGA (ball grid array) type semiconductor package can be achieved.
However, the conventional semiconductor device has the following problems. In the conventional printed circuit board type package including a glass epoxy substrate, the connection between the upper electrode pads and the lower electrode pads or the connection between the upper bonding pad and the lower bonding pad are established via the via holes, so that variations in the structure of the via holes or the plating thickness in the via holes may cause variations in the electrical resistance or the inductance of the wiring portions. Furthermore, since the substrate material is an organic substance, a dielectric constant of the printed circuit board is large, so that it is not suitable to a semiconductor package that requires a high frequency perform
Matsushita Electric - Industrial Co., Ltd.
Nhu David
Nixon & Peabody LLP
Studebaker Donald R.
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