Metal deforming – With cutting – By shearing tool-couple
Reexamination Certificate
2001-07-18
2003-06-03
Crane, Daniel C. (Department: 3725)
Metal deforming
With cutting
By shearing tool-couple
C072S324000, C072S340000
Reexamination Certificate
active
06571595
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cavity shaped package having a recessed portion for accommodating electronic parts such as an integrated circuit, hybrid circuits and so on, in particular, a method of forming a package for electronic parts which is made from a metal plate.
2. Description of Related Art
Through the progress of information devices such as personal computers and so on in recent years, electronic parts such as semiconductor IC circuits or hybrid circuits have been advanced into higher density and higher processing speed, and the information devices using these electronic parts are becoming more precise and more miniaturized. On the other hands, higher density and higher processing speed of these electronic parts increases the amount of heat generated therein. Thus, heat sink means having high efficiency of heat radiation is required. However, the problem is that such miniaturized devices incorporating electronic parts cannot secure enough space for heat sink means that have necessary efficiency of heat radiation due to the miniaturization thereof.
In order to solve the problem, a cavity type package comprising a metal plate called “stiffener”, which has a window or a recess at the center for accommodating electronic parts, has been occurred. The package allows the amount of heat generated from the electronic parts to be evacuated by the metal plate of the stiffener. Such package has in one body both functions as a heat spreader and as a stiffener for reinforcing the package. The package made from a metal plate will be an alternative to a conventional package, for example, made from ceramics since the former is superior to the latter in the heat sink function,
FIGS. 7 and 8
show a package of a semiconductor IC circuit as an example applying abovementioned package. The raw materials of the package
1
is selected from one of metal materials, which has a high thermal conductivity required as a heat spreader and for which plastically deforming processing is applicable, such as cupper alloy stainless steel, aluminum and so on.
An approximately rectangular recess portion
2
having a bottom portion
1
c
with a predetermined thickness is formed at the center of the surface on one side
1
a
of the package
1
. That is, this package
1
is formed in a cavity shape as a whole. A wiring board
4
, which is a TAB or flexible printed board, a usual pointed board, etc., is stuck and secured to the one side
1
a
of the package
1
by means of an adhesive. The wiring board
4
may be a layer on which a wiring circuit is formed and by which the wiring circuit is insulated from the package
1
. An opening
4
a
having an approximately same size as the recess portion
2
is formed in this wiring board
4
. A terminal portion
4
t
having a number of terminals is formed by printed wiring on the periphery of this opening
4
a
with a wire width and a pitch of about 37 nm. The terminals of the terminal portion
4
t
are electrically connected by printed wiring to externally connecting terminals (not indicated in the figures), which are formed on an outer periphery of the wiring board
4
.
Further a chip
5
of electronic parts such as a semiconductor integrated circuit is accommodated in the recess portion
2
formed on the one side
1
a
of the package
1
. The chip
5
is stuck to the bottom portion
1
c
of the recess portion
2
by means of an adhesive in a state where a surface of the chip
5
and that of the bottom portion
1
c
are tightly fitted. What is important in this sticking using an adhesive is that no bubbles should be produced between the chip
5
and the bottom portion
1
c
of the recess portion
2
. This is because the bubbles are expanded and the chip
5
may be thereby peeled off in case where heat is produced during working of the electronic parts in the chip
5
and in case where heat is subjected to the package
1
during its assembling to an apparatus. Thus, the bottom portion
1
c
of the recess portion
2
should be formed in such an evenness that warp is smaller than 30 nm.
On the upper surface of the chip
5
there are disposed a number of terminals
5
t
with a same wire width and a same pitch as those in the terminal portion
4
t
formed on the wiring board
4
. Each of the terminals
5
t
of the chip
5
and each terminal of the terminal portion
4
t
of the wiring board
4
are electrically connected by bonding wires
7
, as indicated in FIG.
7
. Further sealing agent
8
is injected into the recess portion
2
of the package
1
to seal the chip
5
and the bonding wires
7
.
When the electronic parts such as an integrated circuit packed in the package
1
as described above is mounted onto a circuit board of an electronic apparatus not indicated in the figure, solder balls
9
are placed on the externally connecting terminals formed on an outer periphery of the wiring board
4
and they are melted by heating in a state where the package
1
is provisionary fixed at predetermined position on the circuit board of the electronic apparatus. In this way the electronic parts packed in the package
1
and the circuit board of the electronic apparatus are connected electrically via the wiring board
4
without any damages to the package
1
and its electronic parts due to expanding the bubbles between the chip
5
and the bottom portion
1
c.
On the other hand, when a semiconductor IC circuit is exothermic in operating, the package
1
itself has a function of heat spreader, thereby, heat is conducted the package
1
and is released.
In a forming method of above constituted cavity type package, for example, there is a method that a concave part is pressing processed using a pressing punch by press machine or by chemically etching process, a concave part is formed in a metal plate so that keep a bottom of a thin plate.
However, in a pressing process by press machine metal part of volume of the recess part is pushed into a bottom part and periphery. The periphery metal part is curled, then the flatness of the part is not able to correct state. Thereby, a package acquired necessity flatness has a fatal problem. The chemically etching process takes long time, so there are troublesome that the method is not suited in mass production and takes more cost in necessity. Moreover, precision by limiting to control etching process is worth, there is troublesome that practical use has a limit.
Inventors have proposed in U.S. Pat. No. 6,145,365 a preferred method for forming above mentioned type package made from a metal plate. FIGS.
9
(A) to
9
(D) shows the proposed method in summary. The method will be described herein below.
FIG.
9
(A) shows a metal plate
100
that is positioned with respect to a die
104
of a press machine. FIG.
9
(B) shows a pressing process, where the metal plate
100
is pressed recessed by a punch
105
of the press machine onto one side surface
100
a
so that the recessed part
102
is formed. At the same time, a protruding part
103
is formed in ledge shape on another side surface
100
b
of the metal plate
100
.
FIGS.
9
(C) and
9
(D) show cutting process, wherein a cutter
106
shaves off the protruding part
103
formed on the surface
100
b
so as to form a thin bottom
100
c
and to make the surface
100
b
flat. In this cutting process, to avoid displacement of the bottom plate
100
c
in the direction to the recessed part
102
, the bottom plate
100
c
is pressivelly supported by a supporting tool
107
. According to the abovementioned processes, the recessed part
102
for accommodating a chip of electronic parts is formed in the metal plate
100
, which has a bottom plate
100
c
having a predetermined comparatively thin thickness as the bottom of the recessed part
102
. Thereby, the recessed part
102
of predetermined depth is formed by pressing and cutting without any damages to the bottom plate
100
c.
In the above methods, it is possible to form the recessed part
102
having a predetermined shape only on one side of the metal plate without giving the metal
Crane Daniel C.
Flynn ,Thiel, Boutell & Tanis, P.C.
Nakamura Seisakusho Kabushikigaisha
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