Circuit film utilizing a power supply and ground connections

In a semiconductor device constituted by a film circuit, a semiconductor element, a reinforcement plate adhered to the film circuit, for surrounding this semiconductor element, and also a heat sink adhered to this reinforcement plate, which are sealed by employing resin, a stray capacitance between power supply terminals (between power supply and ground) is increased so as to increase the noise withstanding characteristic. Both the reinforcement plate and the heat sink own conductivity characteristics, a wiring film on the ground side among wiring films of the film circuit is electrically connected to one of the reinforcement plate and the heat sink, and a wiring film on the power supply side among these wiring films is electrically connected to the other of these reinforcement plate and heat sink. The heat sink is connected to the wiring film via, for instance, a conductive ring.

BACKGROUND OF THE INVENTION 
The present invention generally relates to a semiconductor device, and more 
specifically to a semiconductor device, a method for manufacturing this 
semiconductor device, and an electronic appliance with employment of this 
semiconductor device comprised of a film circuit on which a plurality of 
wiring films are formed while using an insulating layer as a base, one end 
of the wiring films are used as semiconductor element-sided terminals to 
be connected to electrodes of a semiconductor element, and an external 
terminal is formed on the other end of the wiring film; a semiconductor 
element, the respective electrodes of which are connected to the 
semiconductor element-sided terminals of the wiring films; a reinforcement 
plate adhered to the film circuit, for surrounding the semiconductor 
element; and a heat sink adhered to the reinforcement plate; in which the 
reinforcement plate, the film circuit, and the semiconductor element are 
sealed with each other. 
As a semiconductor device, there is such a semiconductor device that the 
respective electrodes of a semiconductor element are bonded to tip 
portions of the respective leads (wiring films) of a film circuit, a space 
between this semiconductor element and the film circuit is sealed by using 
resin, and a ring-shaped reinforcement plate for surrounding the 
semiconductor element is adhered to a rear surface of the film circuit. 
FIG. 1A and FIG. 1B are sectional views for indicating these conventional 
semiconductor devices. First, a description will now be made of the 
conventional semiconductor device shown in FIG. 1A. In this drawing, 
symbol "a" indicates a film circuit, symbol "b" shows a polyimide tape 
which may constitute a base of this film circuit, symbol "c" represents a 
wiring film which constitutes a lead, and symbol "d" shows an insulating 
layer for selectively covering a surface of the film circuit "a", which is 
located opposite to the base. This insulating layer is made of, for 
example, solder resist. Also, symbol "e" is a soldering ball formed in an 
opening "f" of the insulating layer "d", and this opening "f" exposes the 
surface of the lead "c". Also, this soldering ball constitutes an external 
terminal of the semiconductor device. 
Symbol "g" indicates a semiconductor element, and an electrode of this 
semiconductor element "g" is bonded to a tip portion of such a portion 
projected into a device hall "h" of the lead "c". Symbol "i" indicates 
resin used to seal a space between the semiconductor element "g" and the 
film circuit "a". Symbol "j" represents a rectangular ring-shaped 
reinforcement plate. This reinforcement plate "j" is adhered via adhesive 
agent "k" to a position for surrounding the semiconductor element "g" of 
the rear surface of the film circuit "a". 
Next, the conventional semiconductor device shown in FIG. 1B will now be 
explained. Symbol "a'" shows a film circuit constructed by a wiring film 
"c" which constitutes a lead that is formed on a rear surface of a 
polyimide tape "b" which constitutes a base of this film circuit. An 
opening "f" exposes the lead "c" formed in this polyimide tape "b", and a 
soldering ball "e" which constitutes an external terminal is formed in 
this opening "f". Similar to the semiconductor device shown in FIG. 5A, 
the semiconductor element "g" is connected to the lead "c" of the film 
circuit "a'", and a space between the semiconductor element "g" and the 
film circuit "a'" is sealed by using resin "i". Then, a rectangular 
ring-shaped reinforcement plate "j" is adhered via adhesive agent "k" to 
the rear surface of the film circuit "a'". 
A description will now be made of an assembling method. First, the 
semiconductor element "g" is assembled on the film circuit a (a'). Next, 
the space between the film circuit a (a') and the semiconductor element 
"g" is sealed by using the resin "i". Thereafter, the reinforcement plate 
"j" is adhered to the rear surface of the film a (a'). Subsequently, the 
soldering ball "e" which constitutes the external terminal is formed. 
On the other hand, according to the related art shown in FIG. 1A and FIG. 
1B, no electric connection is made between the film circuit a (a') and the 
reinforcement plate "j". As a result, it is practically difficult to 
prevent the external noise from being entered. Also, a problem exists in 
that this conventional semiconductor device may not effectively prevent 
the external noise producing source. 
Also, conventionally, after the semiconductor element "g" has been 
assembled to the film circuit a (a'), the space between the semiconductor 
element and the film circuit is sealed by using the resin. Thereafter, the 
reinforcement plate "j" is adhered to the film circuit a (a'). As a 
result, there is another problem that since the adhesive agent "i" is 
largely extruded, the reinforcement plate "j" can be hardly mounted. As a 
consequence, as indicated in FIG. 1B, such a plate having a large hole "l" 
must be employed as the reinforcement plate "j". However, this may cause 
the reinforcement effect to be deteriorated, resulting in an unfavorable 
effect. In other words, the reinforcement effect of the semiconductor 
device shown in FIG. 1B should be deteriorated. 
To solve such a problem, the applicant has developed the following 
techniques as proposed Japanese Patent Application No. 8-54478 (which is 
laid-open in Japanese Unexamined Patent Application No. 9-246315). That 
is, the noise withstanding characteristics of the semiconductor device can 
be increased, and further the reinforcement plate can be mounted on the 
film circuit without problems. This proposed semiconductor device is 
featured by that the wiring film which constitutes the ground line formed 
on the peripheral portion thereof is provided on the film circuit, and the 
reinforcement plate owns the conductivity characteristics. Then, the 
wiring film which constitutes this ground line is electrically connected 
to this conductive reinforcement plate at the above-described peripheral 
portion of the film circuit. As a consequence, the reinforcement plate for 
surrounding the semiconductor element may be used as the ground line, 
namely may electrostatically shield other elements. 
This semiconductor device may be manufactured as follows: The reinforcement 
plate is adhered to the film circuit. Thereafter, the semiconductor 
element is located at the position surrounded by the reinforcement plate, 
and the respective electrodes of this semiconductor element are bonded on 
the semiconductor element-sided terminal of the film circuit. 
Subsequently, the reinforcement plate, the film circuit, and the 
semiconductor element are sealed with each other. In other words, in 
accordance with such a semiconductor device manufacturing method, after 
the reinforcement plate has been adhered to the film circuit, the 
semiconductor element is assembled to the film circuit, and then is 
sealed. As a consequence, there is completely no risk that the sealing 
agent for sealing the space between the semiconductor element and the film 
circuit blocks adhesion of the reinforcement plate to the film circuit. As 
a consequence, the reinforcement plate can be mounted without any problem. 
Also, there is no need to employ such a reinforcement plate having the 
large hole as in the semiconductor device shown in FIG. 1B, taking account 
of the assembling condition. Accordingly, there is no risk that the 
reinforcement effect is deteriorated. 
FIG. 2A and FIG. 2B represent the above-described semiconductor device. 
This semiconductor device will now be simply explained. The wiring films 
3E and 3e which constitute the ground line extended on the peripheral 
portion of the film circuit 1, and while using the conductive 
reinforcement plate 25, the wiring film which constitutes this ground line 
3E is electrically connected to this conductive reinforcement plate 25 at 
the peripheral portion of the film circuit 1 by using, for example, 
conductive paste 26. The heat sink 27 is adhered to the rear surface of 
the film circuit 1 and the semiconductor element 4, if necessary. 
Then, this semiconductor device is manufactured as follows. The 
reinforcement plate 25 is adhered to the film circuit 1. Thereafter, the 
semiconductor element 4 is located at the position surrounded by the 
reinforcement plate 25, and the respective electrodes of this 
semiconductor element 4 are bonded with the semiconductor element-sided 
terminals of the film circuit 1. Subsequently, the reinforcement plate 25, 
the film circuit 1, and the semiconductor element 4 are sealed with each 
other by using sealing agent 24. It should be understood that in the 
drawings, reference numeral 2 indicates an insulating film, reference 
numeral 3 denotes a wiring film (lead), reference numeral 6 shows an 
electrode of the semiconductor element 4, reference numeral 7 is elastic 
adhesive agent for adhering the conductive reinforcement plate 25 to the 
film circuit 1, reference numeral 16 indicates a bump of the wiring film 
(lead), and reference numeral 28 shows a dam for blocking a flow of the 
sealing resin 24 to the peripheral portion. 
On the other hand, in accordance with the above-explained related art shown 
in FIG. 2A and FIG. 2B, the reinforcement plate can be surely used as the 
electrostatic shielding means, which may achieve the superior feature. 
However, there is a limit to suppress the noise generation. This is 
because the following limitation exists in increasing of the stray 
capacitance straying between the power supply line and the ground line 
(between power supply terminals, for example, between V.sub.DD and 
V.sub.SS, or between V.sub.CC and V.sub.EE). As a consequence, it is 
difficult to absorb the generated noise by the stray capacitance. This 
reason will now be described more in detail. 
The level at the power supply terminal, and the ground level are varied due 
to the load variation and the like, which may directly cause the noise. 
Although this noise may be absorbed by the stray capacitance existing 
between the power supply and the ground, if this stray capacitance is 
small, then the noise cannot be sufficiently absorbed. As a consequence, 
the larger the stray capacitance between the power supply and the ground 
is increased, the better the noise absorption becomes. However, in 
accordance with the conventional semiconductor device shown in FIG. 2 FIG. 
2A and FIG. 2B, this stray capacitance is constructed only of the stray 
capacitance between the power supply wiring film and the ground wiring 
film, and also of the stray capacitance between the reinforcement plate 
connected to the ground (or power supply) and the power supply wiring film 
(or ground wiring film). 
SUMMARY OF THE INVENTION 
The present invention has been made to solve such a problem, and therefore, 
has an object to increase a stray capacitance between power supply 
terminals (between power supply and ground) so as to increase a noise 
withstanding characteristic of a semiconductor device comprised of: a film 
circuit on which a plurality of wiring films are formed while using an 
insulating layer as a base, one ends of the wiring films are used as 
semiconductor element-sided terminals to be connected to electrodes of a 
semiconductor element, and an external terminal is formed on the other end 
of the wiring film; a semiconductor element, the respective electrodes of 
which are connected to the semiconductor element-sided terminals of the 
wiring films; a reinforcement plate adhered to the film circuit, for 
surrounding the semiconductor element; and a heat sink adhered to the 
reinforcement plate; in which the heat sink, the reinforcement plate, the 
film circuit, and the semiconductor element are sealed with each other. 
To achieve the above-described object, a semiconductor device, according to 
a first aspect of the present invention, is featured by that both the 
reinforcement plate and the heat sink own conductivity characteristics; a 
ground terminal among the semiconductor element-sided terminals of the 
wiring film is also, electrically connected to one of the conductive 
reinforcement plate and the conductive heat sink; and a power supply 
terminal among the semiconductor element-sided terminals of the wiring 
film is also, electrically connected to the other of the conductive 
reinforcement plate and the conductive heat sink. 
As a result, in accordance with the semiconductor device of the first 
aspect, since the ground terminal is connected to one of the conductive 
reinforcement plate and the conductive heat sink, and also the power 
supply terminal is connected to the other thereof, the stray capacitance 
straying between the reinforcement plate and the heat sink may also stray 
between the power supply line and the ground line. As a consequence, the 
stray capacitance straying between the power supply and the ground is 
increased, so that the noise can be effectively absorbed. 
A method for manufacturing a semiconductor device, according to a second 
aspect of the present invention, is featured by that in a method for 
manufacturing the above-described semiconductor device as described in the 
first aspect, after the conductive reinforcement plate has been adhered to 
the film circuit, the semiconductor element is located to a position 
surrounded by the reinforcement plate and the respective semiconductor 
element-sided terminals of the wiring films of the film circuit are bonded 
with the respective electrodes of the semiconductor element; and at the 
same time, the ground terminal among the semiconductor element-sided 
terminals is also bonded on one of the conductive reinforcement plate and 
the conductive heat sink, and further the power supply terminal is also 
bonded on the other of the conductive reinforcement plate and the 
conductive heat sink; and thereafter, the conductive heat sink, the 
conductive reinforcement plate, the film circuit, and the semiconductor 
element are sealed with each other by using resin. 
As a result, in accordance with the method for manufacturing the 
semiconductor device of the second aspect, since the power supply terminal 
of the wiring film of the film circuit and the ground terminal thereof are 
connected not only to the electrodes of the semiconductor element, but 
also to either the reinforcement plate, or the heat sink (double-bonding), 
the capacitance straying between the reinforcement plate and the heat sink 
can exist between the power supply terminal and the ground terminal. 
An electronic appliance, according to a third aspect of the present 
invention, is featured by comprising the semiconductor device as recited 
in the first aspect. 
As a result, in accordance with the electronic appliance of the third 
aspect, since the semiconductor device of the first aspect is used, the 
noise can be reduced. 
In a semiconductor device of the present invention, a ground terminal may 
be connected to a reinforcement plate and a power supply terminal may be 
connected to a heat sink. Conversely, the ground terminal may be connected 
to the heat sink, and the power supply terminal may be connected to the 
reinforcement plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to drawings, the present invention will be described in 
conjunction with embodiment modes shown in these drawings. FIG. 3 is a 
sectional view for showing a semiconductor device according to a first 
embodiment of the present invention. 
In the drawing, reference numeral 1 shows a film circuit. A large number of 
wiring films 3 which constitute leads are formed on the side of a rear 
surface of an insulating layer 2. Reference numeral 3e indicates a wiring 
film (lead) which constitutes a ground line connected to a ground 
electrode of a semiconductor element 4 (will be explained later) among the 
wiring films 3. Reference numeral 3d similarly shows a wiring film (lead) 
which constitutes a power supply line connected to an electrode of a power 
supply terminal. The inner edges of the respective wiring films 3, 3e, 3d 
are projected into a device hole 1h of an insulating layer 2, and 
constitute connection terminals to be connected to electrodes of the 
semiconductor element 4. For the sake of easy understanding, in FIG. 3, 
the wiring film (lead) 3d which constitutes the power supply line is 
indicated by a hatching of an inclined lattice, whereas the wiring film 3e 
which constitutes the ground line is painted in black. Reference numeral 6 
shows a ball electrode 6 is formed on the insulating layer 2 and is formed 
in an opening 21 which exposes the lead 3 by way of the plating. This ball 
electrode 6 has a two layer structure made of, for instance, nickel and 
either solder or gold. 
Reference numeral 25 is a rectangular ring-shaped reinforcement plate made 
of, for example, aluminum. The rectangular ring-shaped reinforcement plate 
25 is adhered to the rear surface of the film circuit 1 via elastic 
adhesive agent 7. This reinforcement plate 25 is manufactured in such a 
manner that at least a portion of this reinforcement plate 25 is sticking 
out from the film circuit 1. Then, a portion deviated from the inner edges 
of the respective wiring films 3d which constitute the above-described 
ground line is bonded to an upper surface of this stick-out portion, so 
that the wiring films 3d are under connection condition to the 
reinforcement plate 25. 
Reference numeral 29 is a rectangular conductive ring made of a conductive 
material. The rectangular conductive ring 29 is positioned apart from the 
reinforcement plate in such a manner that this rectangular conductive ring 
29 is not made in contact with the inside of the reinforcement plate 25. A 
portion deviated from the inner edge of the wiring film 3d which 
constitutes the power supply line is bonded to an upper surface inner 
peripheral portion of this conductive ring 29. 
Reference numeral 4 is a semiconductor element whose electrodes are bonded 
to bumps 16 of tip portions of the wiring films 3, 3d, 3e. Reference 
numeral 27 is a heat sink which is adhered to the semiconductor element 4, 
the reinforcement plate 25, and the rear surface of the conductive ring 
29. The heat sink 27 is made of, for example, aluminum. This heat sink 27 
is adhered to the reinforcement plate 25 via insulating adhesive agent 30, 
so that this heat sink 27 is electrically insulated from the reinforcement 
plate 25. To the contrary, the heat sink 27 is adhered to the conductive 
ring 29 via conductive adhesive agent 31. This heat sink 27 is 
electrically connected via the conductive ring 29 to the wiring film 3e 
which constitutes the ground line of the film circuit 1. 
It should be noted that although the semiconductor element 4, the film 
circuit 1, the reinforcement plate 25, the heat sink 27, and the 
conductive ring 29 are sealed with each other by using resin, the sealing 
resin is not shown in this drawing. On the other hand, in such a case that 
the potential at the rear surface of the element may become equal to the 
power supply level, the semiconductor element 4 may be adhered to the heat 
sink 27 by using the conductive adhesive agent. To the contrary, when the 
potential at the rear surface of the element is not equal to the power 
supply level, the semiconductor element 4 must be adhered to the heat sink 
27 by employing the insulating adhesive agent. However, this never 
constitutes the essential subject of the present invention. 
In such a semiconductor device, the reinforcement plate 25 for surrounding 
the semiconductor element 4 may be used as the power supply line, and also 
the heat sink 27 may be employed as the ground line. Both the 
reinforcement plate 25 and the heat sink 27 can electrostatically shield 
the semiconductor element 4 from other elements. As a consequence, it is 
possible to highly effectively prevent the noise from being entered from 
the outer portion of the semiconductor device into the semiconductor 
element 4. Also, it is possible to highly effectively prevent the noise 
produced within the semiconductor element 4 from being irradiated outside 
this semiconductor element 4, resulting in improvements of the 
electrostatic shield effects. 
Moreover, a large electrostatic capacitance straying between the 
reinforcement plate 25 and the heat sink 27 is added to the stray 
capacitance defined between the power supply line and the ground line, the 
stray capacitance between the power supply and the ground is extremely 
increased. As a result, even when a potential variation occurs in either 
the power supply line or the ground line and thus noise is produced, this 
noise may be absorbed by presence of such a large stray capacitance, so 
that the noise can be hardly produced. Assuming now that the noise occurs, 
this noise becomes low. As a result, the noise withstanding characteristic 
of the semiconductor device is increased. 
It should be noted that in the semiconductor device shown in FIG. 3, the 
reinforcement plate 25 is connected to the power supply line, and the heat 
sink 27 is connected to the ground line. Conversely, the reinforcement 
plate 25 may be connected to the ground line, whereas the heat sink 27 may 
be connected to the power supply line. There is no large difference in the 
effects achieved by the embodiment case, and the alternative case. 
FIG. 4A to FIG. 4I are sectional views for indicating sequential steps for 
forming the film circuit and also for adhering the reinforcement plate. 
First, as indicated in FIG. 4A, a metal stacked layer plate 11 having a 
three layer structure is prepared. This stacked layer plate 11 is made by 
stacking a copper layer 12 having a thickness of, for example, 150 .mu.m; 
an aluminum layer 13 having a thickness of 3 .mu.m, which plays a role as 
an etching stopper; and a plating underlayer 14 having a thickness of 2 
.mu.m and made of either copper or nickel. It should be understood that 
the plating underlayer 14 may be made of such a multilayer structure that, 
for instance, a nickel layer (thickness being, e.g., 2 .mu.m) is formed on 
a chrome layer (thickness being, e.g., 0.2 .mu.m). 
Next, as indicated in FIG. 4B, the wiring films (leads) 3, 3d, 3e are 
formed on the plating underlayer 14. Concretely speaking, resist of 
negative patterns is coated with respect to patterns used to form these 
wiring films 3, 3d, 3e. While this resist is used as a mask, the 
underlayer 14 is plated by using copper (otherwise nickel) and the plating 
thickness is selected to be, for example, 30 .mu.m. When this forming 
method is carried out, since there is no side etching, very fine loads can 
be manufactured in high precision. 
On the other hand, the important factor to form these wiring films 3, 3d, 
3e is such that the wiring films 3d and 3e should be double-bonded 
(namely, wiring films are bonded to electrodes of semiconductor element, 
and wiring films are bonded to either reinforcement plate or conductive 
ring). As a consequence, lengths of these wiring films 3d and 3e which are 
projected to the inside must be made longer than that of the remaining 
wiring film 3. In FIG. 4, a portion indicated by the inclined lattice of 
the lead is an inner edge portion of the wiring film 3d which constitutes 
the power supply line. This power supply line can be observed being 
sticking from the normal wiring film 3. It should be noted that since the 
wiring film 3e which constitutes the ground line is hidden from the above 
wiring film 3d, this wiring film 3e does not appear in FIG. 4. 
Next, as indicated in FIG. 4C, a lead frame shape to which a plurality of 
film circuits are integrally coupled is formed by selectively etching both 
surfaces of the metal stacked layer plate 11 in such a manner that this 
etching process may penetrate through this metal stacked layer plate 11. 
This etching process is carried out by employing, for example, an etching 
fluid of ferric chloride. Reference number 30 shows an outer hole formed 
by the etching process. 
Next, an insulating layer (insulating film) 2 is selectively formed on a 
surface of the above-described stacked layer plate 11 on the side of a 
lead forming surface thereof. This insulating layer 2 is formed in a 
desirable pattern in such a manner that while a resin material having a 
photosensitivity characteristic is used, this photosensitive resin 
material is coated, exposed, and then developed. Reference numerals 21, 
21, . . . are openings used to expose such a portion where the ball 
electrodes 6 of the respective wiring films 3, 3d, 3e of the insulating 
layer 2 are formed. The insulating layer 2 is selectively formed so as to 
have these openings 21, 21, . . . As a result, it is not required that the 
insulating layer 2 is patterned by way of, for example, the laser process. 
Thereafter, a ring-shaped dam 28 made of a resin film is formed. Concretely 
speaking, this dam 28 plays a role to dam that sealing resin is overflown 
out from the wiring films 3, 3d, 3e in the case that after the respective 
electrodes of the semiconductor element 4 are bonded on the inner edges of 
the wiring films 3, 3d, 3e of the film 1, these wiring films and the 
electrodes are sealed by using resin (not shown). However, this dam 28 is 
not necessarily required. FIG. 4D indicates such a condition that the dam 
28 has been formed. 
Next, as indicated in FIG. 4E, while the insulating layer 2 is used as a 
mask, the soldering balls 6, 6, . . . , which constitute external 
terminals are formed on the surfaces of the wiring films 3, 3d, 3e. The 
soldering balls 6, 6, . . . , are formed by way of the nickel plating 
process (thickness is selected to be, for example, 80 to 110 .mu.m), and 
either the soldering process or the gold plating process (thickness is 
selected to be, for example, 10 to 30 .mu.m). 
Next, as shown in FIG. 4F, a portion corresponding to a major portion 15 of 
the film circuit 1 of the thick copper layer 12 located on the rear side 
of the stacked layer 11 is removed by way of the selective etching from 
the rear side. This selective etching process is carried out by employing 
an etching fluid of, for example, H.sub.2 SO.sub.4 /H.sub.2 O.sub.2. The 
reason why such an etching fluid is employed is given as follows: This 
etching fluid may etch away copper, but may not etch away aluminum, and 
thus can cause the aluminum layer 13 to play a role as an etching stopper. 
Next, as shown in FIG. 4G, while the above-explained wiring layers 3, 3d, 
3e are used as a mask, both the plating underlayer 14 which constitutes an 
underlayer of these wiring films, and also the aluminum layer 13 which has 
constituted the etching stopper are etched away. As a result, the 
respective wiring films 3, 3d, and 3e are independently provided, and are 
brought into such a condition that these wiring films are not electrically 
shortcircuited with each other. 
Next, as indicated in FIG. 4H, a rectangular ring-shaped reinforcement 
plate 25 is adhered to a rear surface of the major portion of the film 
circuit 1 via adhesive agent 7 having a cushion characteristic. In this 
case, there is an important factor for the reinforcement plate 25. That 
is, an inner peripheral portion of this reinforcement plate 25 is smaller 
than an inner peripheral portion (device hole) of the film circuit 1, and 
when the film circuit 1 is overlapped over the reinforcement plate 25, the 
inner peripheral portion of the reinforcement plate 25 is sticking into 
the device hole 1h of the film circuit 1. This is because the portion 
deviated from the inner edge of the wiring film 3d which constitutes the 
power supply line can be bonded to the reinforcement plate 25. 
Next, as indicated in FIG. 4I, bumps 16, 16, . . . , are formed on the edge 
portions of the respective wiring films 3, 3d, and 3e. It should be 
understood that these bumps may be formed on the side of the semiconductor 
element 4, otherwise none of these bumps is formed thereon. 
In this embodiment mode, the lead 3 is formed in such a manner that while 
the resist film selectively formed on the plating underlayer film is used 
as the mask, the plated film is grown. Alternatively, while the layer 14 
made of either copper or nickel is made thicker, the lead may be formed by 
patterning this layer by way of the selective etching process. 
Next, referring now to FIG. 5A to FIG. 5C, a description will be made of 
sequential steps for assembling the semiconductor element to the film 
circuit equipped with the reinforcement plate, and also for assembling a 
conductive ring and the heat sink. 
As indicated in FIG. 5A, a conductive ring 29 is positioned within the 
rectangular ring-shaped reinforcement plate 25. This conductive ring 29 is 
surface-processed in order that the bumps can be fastened to this 
conductive ring 29. 
Subsequently, as shown in FIG. 5B, the bumps 16, 16, . . . , of the tip 
portions of the respective wiring films 3, 3d, 3e are connected to the 
electrode pads 5, 5, . . . , of the semiconductor element 4 by way of the 
single point bonding. In connection with this single point bonding, as to 
the wiring film 3d which constitutes the power supply line, after the tip 
portion of this wiring film 3d has been bonded to the electrode pads 5 
which constitute the power supply terminal of the semiconductor element 4, 
a portion which is slightly separated from the tip portion is also bonded 
on the upper surface of the reinforcement plate 25. Further, as to the 
wiring film 3e which constitutes the ground line, after the tip portion of 
this wiring film 3e has been bonded to the electrode pads 5 which 
constitute the ground terminal of the semiconductor element 4, a portion 
which is slightly separated from the tip portion is also bonded on the 
upper surface of the conductive ring 29. Alternatively, it is of course 
possible to connect the wiring film 3d to the conductive ring 29, and also 
to connect the wiring film 3e to the reinforcement plate 25. 
Next, as shown in FIG. 5C, the heat sink 27 is adhered to the semiconductor 
element 4, the reinforcement plate 25, and the rear surface of the 
conductive ring 29. In this case, there is such an important factor that 
the reinforcement plate 25 is adhered to the heat sink 27 by using 
insulating adhesive agent 30, whereas the conductive ring 29 is adhered to 
the heat sink 27 by employing conductive adhesive agent 31. Then, the 
stray capacitance between the reinforcement plate 25 and the heat sink 27, 
and thus the stray capacitance between the power supply terminal and the 
ground terminal can be controlled based upon the material (dielectric 
constant) of the insulating adhesive agent 30, or the thickness of this 
insulating adhesive agent 30. 
Thereafter, the shapes of the soldering electrodes 6, 6, . . . , which 
constitute external terminals are shaped in dome shapes by way of the 
reflow fusing. Subsequently, these soldering electrodes 6, 6, . . . , are 
sealed by resin. Next, an unnecessary portion of the lead-frame-shaped 
metal stacked layer body 11 is cut away, and the respective film circuits 
1 are independently separated from each other. As a result, the 
semiconductor device according to the present invention as shown in FIG. 3 
can be manufactured (note that indication of resin is omitted in FIG. 3). 
The above-described semiconductor device indicated in FIG. 3 may be 
employed in each of electronic appliances. In particular, when this 
semiconductor device is used in, for example, a portable telephone and the 
like which require noise withstanding characteristics, such a low noise 
merit owned by the semiconductor device can be effectively realized. FIG. 
6 represents an example A of such an electronic appliance (portable 
telephone). In this electronic appliance, a semiconductor device C 
according to the present invention is present which is mounted on a mother 
board B, and this semiconductor device C constitutes at least a portion of 
the internal circuit of this electronic appliance. 
In accordance with the semiconductor device of the first aspect, the ground 
terminal is connected to one of the conductive reinforcement plate and the 
conductive heat sink, and the power supply terminal is connected to the 
other of the conductive reinforcement plate and the conductive heat sink. 
As a consequence, the electrostatic capacitance straying between the 
reinforcement plate and the heat sink may stray between the power supply 
and the ground. As a result, the stray capacitance existing between the 
power supply and the ground can be increased. Therefore, the noise can be 
effectively eliminated by such a large stray capacitance, and thus the 
noise withstanding characteristic of the semiconductor device can be 
increased. 
In accordance with the method for manufacturing the semiconductor device of 
the second aspect, both the power supply terminal and the ground terminal 
of the wiring films of the film circuit are connected not only to the 
electrodes of the semiconductor element, but also to either the 
reinforcement plate or the heat sink (double-bonding). As a consequence, 
such a capacitance straying between the reinforcement plate and the heat 
sink can be located between the power supply terminal and the ground 
terminal. 
In accordance with the electronic appliance of the third aspect, since such 
a semiconductor device having the large stray capacitance between the 
power supply and the ground is employed and this stray capacitance is 
capable of effectively absorbing the noise, the noise can be further 
reduced.