Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Insulative housing or support
Reexamination Certificate
2002-06-14
2004-04-13
Zarnehe, David A. (Department: 2829)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Insulative housing or support
Reexamination Certificate
active
06720209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a circuit device, and in particular, a method for fabricating a thin type circuit device that utilizes a conductive plated layer and conductive layer and is able to achieve multi-layer connection.
2. Description of the Prior Arts
Recently, IC packages have been actively employed in portable devices, and small-sized and high density assembly devices. Conventional IC packages and assembly concepts tend to greatly change. For example, this is described in, for example, Japanese Laid-Open Patent Publication No. 2000-133678. This pertains to a technology regarding a semiconductor apparatus in which a polyimide resin-sheet being a flexible sheet is employed as one example of insulation resin sheets.
FIG.
12
through
FIGS. 14A
,
14
B and
14
C show a case where a flexible sheet
50
is employed as an interposer substrate. Also, the views illustrated upside of the respective drawings are plan views, and the views illustrated downside thereof are longitudinally sectional views taken along the lines A—A of the respective drawings.
First, copper foil patterns
51
are prepared to be adhered to each other via an adhesive resin on the flexible sheet
50
illustrated in FIG.
12
. These copper foil patterns
51
have different patterns, depending upon cases where a semiconductor element to be assembled is a transistor or an IC. Generally speaking, a bonding pad
51
A and an island
51
B are formed. Also, an opening
52
is provided to take out an electrode from the rear side of the flexible sheet
50
, from which the above-described copper foil pattern
51
is exposed.
Subsequently, the flexible sheet
50
is transferred onto a die bonder, and as shown in
FIG. 13
, a semiconductor element
53
is assembled or mounted. After that, the flexible sheet
50
is transferred onto a wire bonder, wherein the bonding pads
51
A are electrically connected to the pads of the semiconductor elements
53
by thin metal wires
54
.
Finally, as shown in
FIG. 14A
, sealing resin
55
is provided on the surface of the flexible sheet
50
, and the surface thereof is completely sealed with the sealing resin
55
. Herein, the bonding pads
51
A, island
51
B, semiconductor elements
53
and thin metal wires
54
are transfer-molded so as to be completely overcoated.
After that, as shown in
FIG. 14B
, connecting means
56
such as solder and a soldering ball is provided, wherein spherical solder
56
deposited to the bonding pad
51
A is formed via the opening
52
by passing through a solder reflow furnace. Further, since semiconductor elements
53
are formed in the form of a matrix on the flexible sheet
50
, these are diced to be separated from each other as shown in FIG.
14
.
In addition, the sectional view of
FIG. 14C
shows electrodes
51
A and
51
D on both sides of the flexible sheet
50
as the electrodes. The flexible sheet
50
is generally supplied from a maker after both sides thereof are patterned.
Since a semiconductor apparatus that employs the above-described flexible sheet
50
does not utilize any publicly known metal frame, the semiconductor apparatus has a problem in that a multi-layer connection structure cannot be achieved while it has an advantage by which a remarkably thin package structure can be brought about, wherein path is carried out with one layer of copper foil pattern
51
, which is provided substantially on the surface of the flexible sheet
50
.
It is necessary to make the flexible sheet
50
sufficiently thick, for example, approx. 200 &mgr;m, in order to retain supporting strength to achieve a multi-layer connection structure. Therefore, there is a problem of retrogression with respect to thinning of the sheet.
Further, in the method for fabricating a circuit device, a flexible sheet
50
is transferred in the above-described fabrication apparatus, for example, a die bonder, wire bonder, a transfer mold apparatus, and a reflow furnace, etc., and the flexible sheet
50
is attached onto a portion called a “stage” or a “table”.
However, if the thickness of the insulation resin that becomes the base of the flexible sheet
50
is made thin, for example, 50 &mgr;m, the flexible sheet
50
may be warped as shown in
FIG. 15
or its transfer performance may be remarkably worsened where the thickness of the copper foil pattern
51
formed on the surface thereof is thin to be 9 through 35 &mgr;m. In addition, another problem arises in that the flexible sheet
50
is defectively attached to the above-described stage or table. This is because it is considered that the resin is warped since the insulation resin itself is very thin, and the resin is warped due to a difference in the thermal expansion coefficient between the copper foil pattern
51
and the insulation resin. Particularly, if a hard insulation material in which no glass cloth fibers are used as a core material is warped as shown in
FIG. 15
, there was a problem in that the insulation material could easily collapse due to compression from above.
Since the portion of the opening
52
is compressed from above when being molded, a force by which the periphery of the bonding pad
51
A is warped upward is brought about, the adhesion of the bonding pad
51
A is worsened.
Also, the resin material that constitutes a flexible sheet
50
has less flexibility, or if a filler to increase the thermal conductivity is blended, the flexible sheet
50
is made hard. In such a case, where bonding is carried out by a wire bonder, there may be a case where the bonded portion is cracked. Also, when performing transfer molding, there is a case where the portion with which a metal die is brought into contact is cracked. This remarkably occurs if any warping shown in
FIG. 15
is provided.
Although the flexible sheet
50
described above is such a type that no electrode is formed on the rear side thereof, there are cases where an electrode
51
D is formed on the rear side of the flexible sheet
50
as shown in FIG.
14
C. At this time, since the electrode
51
D is brought into contact with the above-described fabrication apparatus or is brought into contact with the transfer plane of transfer means between the fabrication apparatuses, another problem occurs in that damage and scratches arise on the rear side of the electrode
51
D, wherein the electrode is established with such damage and scratches retained, the electrode
51
itself may be cracked due to application of heat later on.
Also, if an electrode
51
D is provided on the rear side of the flexible sheet
50
, a problem occurs in that, when carrying out transfer molding, no facial contact with the stage can be secured. In this case, if the flexible sheet
50
is composed of a hard material as described above, the electrode
51
D becomes a fulcrum and the periphery of the electrode
51
D is compressed downward, wherein the flexible sheet
50
is cracked.
The present inventor proposed use of an insulation resin sheet for which the first thin conductive layer and the second thick conductive layer are adhered by insulation resin.
SUMMARY OF THE INVENTION
A method for fabricating a circuit device according to the invention comprises the steps of: preparing an insulation resin sheet having the surface of a conductive layer overcoated with insulation resin; forming through holes in the above-described insulation resin at appointed points on the above-described insulation resin sheet, and selectively exposing the rear side of the above-described conductive layer; forming a conductive plated layer in the above-described through holes and on the surface of the above-described insulation resin; forming a first conductive path layer by etching the above-described conductive plated layer to an appointed pattern; adhering and fixing semiconductor elements on the above-described first conductive path layer with the same electrically insulated therefrom; overcoating the above-described first conductive path layer and the above-described semiconductor elements with a sealing resin layer
Igarashi Yusuke
Kobayashi Yoshiyuki
Nakamura Takeshi
Sakamoto Noriaki
Fish & Richardson P.C.
Geyer Scott B.
Sanyo Electric Co,. Ltd.
Zarnehe David A.
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