Semiconductor device and method for mounting semiconductor wafer

A semiconductor device comprises a printed circuit board with circuit pattern formed thereon, and a semiconductor wafer having terminals installed on its peripheral portion. Semiconductor chips are mounted on one surface or both surfaces of the semiconductor wafer. A connector is installed on the printed circuit board for electrical connection with the terminals. When the terminals are connected to the circuit pattern, the semiconductor wafer is installed substantially vertically on the printed circuit board. Or a semiconductor wafer member is constituted by two semiconductor wafers, and a closed space is internally formed between the two wafers and heat pipes for heat radiation are inserted in the closed space.

BACKGROUND OF THE INVENTION 
The present invention relates to a semiconductor device including a 
semiconductor wafer and method for mounting a semiconductor wafer. 
A semiconductor device includes a semiconductor wafer with a circuit 
pattern formed thereon which is mounted on a printed circuit board. Such a 
semiconductor device in the prior art is shown in FIG. 13. A semiconductor 
wafer 1301 is mounted horizontally on a printed circuit board 1302, and 
respective terminals of the wafer and board are connected to each other by 
a bonding wires 1303. A device using such a mounting,method is also 
disclosed in Nikkei micro device (December 1989) pp. 99-105. 
In a semiconductor device of the prior art, however, a problem exists in 
that since a semiconductor wafer is mounted horizontally on a printed 
circuit board, the mounting area is extremely large. Also, since the 
terminal connection between the semiconductor wafer and the printed 
circuit board are carried out by bonding wires, time is required for 
bonding and execution of the bonding itself is difficult for a large-size 
semiconductor wafer. 
Further, in a device mounting such semiconductor wafer on a printed circuit 
board, power consumption becomes excessive and radiation becomes a 
problem. Since the semiconductor wafer is mounted horizontally on the 
printed circuit board in the prior art, the radiation property is poor and 
there is the possibility of adversely affecting the electric property. 
SUMMARY OF THE INVENTION 
In view of the above problems, an object of the present invention is to 
provide a semiconductor device including a semiconductor wafer and a 
method for mounting a semiconductor wafer, where the mounting area is 
reduced, high density mounting becomes possible, time is not wasted for 
connections between the semiconductor wafer and the printed circuit board, 
and further the radiation property is improved. 
According to the present invention, a semiconductor device is provided 
which comprises a printed circuit board, with a circuit pattern formed 
thereon, and a semiconductor wafer having a terminal installed a 
peripheral portion thereof and being mounted substantially vertically on 
the printed circuit board with the terminal electrically connected to the 
circuit pattern of the printed circuit board. 
Since the semiconductor wafer is mounted substantially vertically on the 
printed circuit board, the mounting density is improved and the radiation 
property is better in comparison to the horizontally mounted state. 
A semiconductor chip may be mounted on one surface or both surfaces of the 
semiconductor wafer, and also in this case, the mounting density and the 
radiation property are improved. When the semiconductor chip is mounted on 
both surfaces, the location of terminals on both surfaces of the 
peripheral portion of the semiconductor wafer further improves the 
mounting density. 
When a connector is installed on the printed circuit board and the 
peripheral portion with a terminal of the semiconductor wafer installed 
thereon is fitted to this connector, electrical connection between the 
semiconductor wafer and the printed circuit board becomes easier and the 
mounting time can be reduced. 
A bus line formed on the semiconductor wafer comprises main bus lines and 
branch bus lines, and when the main bus lines are connected to the 
terminal through an input/output chip, signal processing can be carried 
out more efficiently and loss and delay of the signal transmission can be 
suppressed. 
A cooling medium flows (e.g. fluorocarbon) flows in or out through a spacer 
and a connector, between a space internally formed in the semiconductor 
wafer member with two semiconductor wafers opposed and piping of the 
printed circuit board, thereby the semiconductor wafer is forcibly cooled 
and the radiation property is improved. 
When the semiconductor chip is mounted at the inside surface with 
semiconductor wafers opposed, since the chip is cooled directly by the 
cooling medium, the radiation property is further improved. 
When a heat pipe is installed between the two opposite semiconductor wafers 
and a radiating fin is installed on the end of the heat pipe, heat 
generated by the semiconductor wafer is transmitted efficiently to the end 
by the heat pipe and radiated from the radiating fin thereby the radiation 
property is excellent. 
If the outside shape of the semiconductor wafer is rectangular, when the 
semiconductor chip is mounted on the semiconductor wafer, there is less 
waste space and the mounting density is improved. 
If a reinforcing plate is installed on a portion of the surface of the 
semiconductor wafer and not having other parts mounted, the strength of 
the semiconductor wafer is increased. 
Such a semiconductor device can be manufactured by a package method for the 
semiconductor wafer of the present invention so that the above-mentioned 
function achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention will be described, with reference to 
the accompanying drawings. 
FIG. 1(a) shows the structure of a semiconductor device according to a 
first embodiment. In this embodiment, a circuit pattern is formed on a 
semiconductor wafer 11, without semiconductor chip parts comprising a WSI 
(wafer scale integration) element. Such a structure is characterized in 
that the semiconductor wafer 11 is mounted vertically on a printed circuit 
board 15. A flat oriented portion 13 at a peripheral portion of the 
semiconductor wafer 11 is provided with terminals 12 for connection with 
the printed circuit board 15. The terminals 12 include a power source 
terminal for supplying power, a signal input/output terminal for inputting 
or outputting signals, and the like. Formation of the terminals 12 may be 
carried out together during the step of forming a metal wiring layer 
during manufacture of the semiconductor wafer 11. 
The terminals 12 are fitted into a connector 14 mounted on the printed 
circuit board 15, thereby mounting the semiconductor wafer 11. In this 
case, the connector 14 functions as a fixture for fixing the semiconductor 
wafer 11 to the printed circuit board 15, and also functions to connect 
both members electrically. However, the semiconductor wafer 11 may be 
fixed onto the printed circuit board 15 using any fixing part, and the 
terminals 12 may be connected to the printed circuit board 15 by means of 
soldering or the like. 
FIG. 1(b) is a right side view when the semiconductor wafer 11 is mounted 
on the printed circuit board 15. As shown in the figure, a plurality of 
connectors 14 can be mounted on the printed circuit board 15, and a 
plurality of semiconductor wafers 11 can be fitted and mounted. According 
to this embodiment, since the package area is reduced, in comparison to 
the device in the prior art shown in FIG. 13, even when the printed 
circuit board 15 of the same area is used, a plurality of semiconductor 
wafers 11 can be mounted, thereby improving the package density. Also, 
since the semiconductor wafer 11 is mounted vertically, the radiation 
property is good. 
FIG. 2 shows structure of a semiconductor device according to a second 
embodiment of the present invention. In this embodiment, semiconductor 
chip parts 22 are mounted on a semiconductor wafer 21 with a wiring 
pattern formed thereon. The semiconductor wafer 21 and the semiconductor 
chips 22 are connected by soldering or bonding wires, and can be 
manufactured using the chip-on-wafer (hereinafter referred to as "COW") 
technology. 
Terminals 24 are also formed on a flat, oriented portion 23 of the 
semiconductor wafer 21, The terminals 24 are formed simultaneously during 
the step of forming a wiring layer connected to the semiconductor chip 
parts 22 on the semiconductor wafer 21, and thereby the number of 
processes can be reduced. 
FIG. 3 shows the process of mounting the semiconductor chip part 22 onto 
the semiconductor wafer 21 by the COW technology. First, as shown in FIG. 
3(a), an insulation layer 32 is on surface of a semiconductor substrate 
31. As shown in FIG. 3(b), a wiring layer 33 is formed at a desired 
location on the surface of the insulation layer 32. As shown in FIG. 3(c), 
the wiring layer 33 and electrode of the semiconductor chip 22 are mounted 
on the semiconductor wafer 21 in the state when they are electrically 
connected by a bump 34. 
Also as shown in FIG. 4, the semiconductor chip 22 can be mounted using a 
tape automatic bonding (TAB) method. As shown in FIG. 4(a), first, a 
wiring layer 43 is formed on a semiconductor substrate 41 over an 
insulation film 42. And then, as shown in FIG. 4(b), a lead 45 formed on 
tape and an electrode of the semiconductor chip 22 are connected by a bump 
44, and the lead 45 and a wiring layer 43 are connected by a bump 46. When 
the TAB method is used, all semiconductor chips 22 can be mounted at the 
same time on the semiconductor wafer 21, thereby high production 
efficiency can be obtained. 
A semiconductor device according to a third embodiment of the present 
invention has structure shown in FIG. 5(a) as a plan view and in FIG. 5(b) 
as a right side view in its package state. The semiconductor chips 22 are 
mounted on both surfaces of a semiconductor wafer 51. Terminals 54 are 
formed on both surfaces at an flat, oriented portion 53 of the 
semiconductor wafer 51. The terminals 54 are fitted to a connector 55 on a 
printed circuit board 56 and mounted. 
FIG. 6 shows an example of a configuration in the case where semiconductor 
chip parts are mounted on a semiconductor wafer and connected by bus 
lines. Semiconductor chips 68 are mounted on a semiconductor wafer 61, and 
input/output chips 67 are mounted at a location close to terminals 63 of a 
flat, oriented portion 62. On the surface of the semiconductor wafer 61, 
bus lines are formed so that signals can be transmitted between chips. The 
bus lines are formed with a characteristic impedance being 50 ohms in 
order to reduce the loss during signal transmission, and further are 
composed of main bus lines 66 and branch bus Lines 65 so that signal 
processing can be carried out efficiently. The main bus lines 66 extend in 
mainstay form on the surface of the semiconductor wafer 61, and the branch 
bus lines 65 are arranged in a branched state to the main bus lines 66. 
The semiconductor chip parts 68 are connected to the branch bus lines 65. 
On the other hand, the main bus lines 66 are connected through the 
input/output chips 67 to the terminals 63. 
FIG. 7 shows an example where the semiconductor chips 68 are arranged on 
the semiconductor wafer 61. A logic operation chip 68a is arranged in the 
vicinity of the main bus line 66, and a control chip 68b and a memory chip 
68c are arranged on the periphery of the semiconductor wafer 61. The logic 
operation chip 68a specifically includes chips of a register arithmetic 
logic operation unit (RALU), a sequence control unit (SQCU), an 
instruction memory unit (IROU) or a data memory unit (DRAU). Thus chips 
are arranged corresponding to respective functions so the delay of signals 
can be effectively suppressed. 
Next, a fourth embodiment will be described where forced cooling is carried 
out so as to improve the radiation property. The structure of a device 
according to this embodiment is shown in FIG. 8(a) being a plan view and 
FIG. 8(b) being a right side view corresponding to this. Two semiconductor 
wafers 81 are joined in the state that a space 90 is internally formed 
through a spacer 82. When the semiconductor chip is to be mounted on the 
semiconductor wafer 81, it is mounted on the outside surface. The spacer 
82 is provided with a cooling medium inlet/outlet member 83 having an 
inlet port 84 and an outlet port 85 for cooling medium at a flat, oriented 
portion 91 of the semiconductor wafer 81. A cooling medium flows in from 
the inlet port 84 in direction of the arrow A and fills the space 90, 
thereby cooling the semiconductor wafer 81. The cooling medium with its 
temperature raised by the heat discharged by the semiconductor wafer 81 
flows from the outlet port 85 in the direction of arrow B. 
Flowing-in or flowing-out of the cooling medium to the space 90 becomes 
possible by packaging on a printed circuit board 86 having structure as 
shown in FIG. 9. A connector 88 to be fitted to the orientation flat 
portion 91 of the two semiconductor wafers 81 is mounted on the printed 
circuit board 86. The connector 88 is provided with two pipes 89 to be 
fitted to the inlet port 84 and the outlet port 85 respectively at the 
center portion. The cooling medium flows in from one pipe 89 in the 
direction of arrow A into the space 90, and flows out from the space 90 
through other pipe 89 (not shown) into piping 87 installed in parallel to 
the surface of the printed circuit board 86. Thus the cooling medium is 
circulated through the inside of the space 90 enclosed by the two 
semiconductor wafers 81 and the piping 87, whereby forced cooling is 
performed. 
For the cooling medium, gas such as air, helium (He), or a liquid such a 
fluorocarbon being a compound of fluorine and carbon, a water can be used. 
In the device in the prior art as shown in FIG. 13, the radiation property 
is poor, and one semiconductor wafer is not allowed to consume power of 
100 W or more. On the contrary, when the forced cooling structure as in 
the fourth embodiment is used, power consumption of 200 W or more becomes 
possible. 
In a fifth embodiment of the present invention shown in FIG. 10, 
semiconductor chips 103 are mounted within a space 104 between two 
semiconductor wafers 101 joined by a spacer 102. Since each element 
package surface of the semiconductor wafer 101 is in an opposed state and 
is enclosed within the space 104, the cooling medium cools the 
semiconductor chips 103 directly, thereby increasing the cooling effect. 
In this embodiment, terminals 106 of the semiconductor wafer 101 are also 
installed to be opposed on the inside. The terminals 106 are contacted 
with both sides of a connector 107 installed on a printed circuit board 
108 and are connected electrically. The cooling medium is circulated 
through a pipe 110 between piping 109 and the space 104 in a similar 
manner to the fourth embodiment. 
In any of the first to fifth embodiments as above described, a circular 
semiconductor wafer is used. However, as in a sixth embodiment shown in 
FIG. 11, a semiconductor wafer 111 worked into a rectangular shape may be 
used. In this case, when semiconductor chips 112 are mounted on the 
surface, wasteful space is eliminated at the periphery and thereby the 
mounting density is improved. Also in such a semiconductor wafer 111, 
terminals 113 are installed on the end surface thereby the wafer 111 can 
be mounted vertically on the printed circuit board. 
Next, the structure of a seventh embodiment of the present invention is 
shown in FIG. 12(b) being a front view and FIG. 12(a) being a right side 
view thereof. This embodiment is characterized in that heat pipes are used 
in order to increase the radiation property. Two semiconductor wafers 1202 
worked into rectangular shape are opposed with a spacer 1201, and in the 
space part, a plurality of heat pipes 1204 are inserted in a contacting 
state. A radiation fin 1203 is provided at the bottom end of each heat 
pipe 1204. The heat generated by the semiconductor wafers 1202 is 
transmitted through the heat pipes 1204 to the radiation fins 1203, and is 
radiated from the radiation fins 1203 whereby air cooling or liquid 
cooling is carried out. Since the heat pipes with a high heat transfer 
rate are used, the heat radiation property can be increased. 
Each of the above-mentioned embodiments is an example, and does not limit 
the present invention. Also on portions of the surface of the 
semiconductor wafer and not having parts such as semiconductor chips 
packaged, a reinforcing plate of stainless steel or the like may be 
installed so as to increase the strength of the structure.