Resin sealing type semiconductor device in which a very small semiconductor chip is sealed in package with resin

A lead of a lead frame cannot be made close to a very small semiconductor chip in view of processing dimensions. If a TAB technique is used to directly connect the semiconductor chip and the lead in order to improve in reliability, a device for forming a bump on an electrode of the chip is required, which increases the cost of investment in equipment. A printed circuit board is formed between the lead and bed and a bonding wire is used to shorten the length of wiring and thus to decrease in cost and improve in reliability. Since an electrode pad of the semiconductor chip, the printed circuit board, and the lead are connected to each other using the TAB techique, the productivity of semiconductor device is increased. Using the TAB technique, no bumps are formed anywhere and the cost of investment in equipment is not so increased.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a resin sealing type semiconductor device 
wherein a very small semiconductor chip is sealed in a package with resin. 
2. Description of the Related Art 
Semiconductor chips have been reduced in size in accordance with 
miniaturization of elements. Generally, as the size of a semiconductor 
chip decreases, the mechanical stress thereof lowers, and, thus the 
semiconductor chip is more difficult to break. The small semiconductor 
chip has a more reliable temperature a variation than a large one and it 
can be manufactured at low cost. Using small semiconductor chips, a 
semiconductor device whose operating speed is high, power consumption is 
low, and electrical characteristic are good, can be achieved. 
FIG. 1 is a cross sectional view showing a semiconductor device in which a 
very small semiconductor chip having the above-described features is 
sealed with resin. Semiconductor chip 12 is die-bonded onto bed 11 of a 
lead frame, lead 13 of the lead frame is connected to electrode pad 14 on 
chip 12 by bonding wire 15 and they are sealed in with mold resin 16. 
Since the lead frame to be processed is limited in size, lead 13 cannot be 
arranged sufficiently close to semiconductor chip 12 and inevitably 
bonding wire 15 is lengthened. 
Although bonding wire 15 is in a correct position before the semiconductor 
chip is sealed with resin, it is deformed by the pressure exerted during 
the resin sealing as indicated by broken line A in FIG. 1, and is brought 
into contact with another bonding wire. There is a strong possibility that 
bonding wire 15 becomes defective. 
One method for solving the above problem, is to connect chip 12 and lead 13 
by TAB (Tape Automated Bonding) tape 21 using a TAB technique, as shown in 
FIG. 2. The TAB technique is as follows. TAB tape 21 is formed by sticking 
electrode pad 14 and a thin-film wire made of Cu or the like corresponding 
to lead 13 on a resin film. The TAB tape allows electrode pad 14 and lead 
13 to be bonded together. 
TAB tape 21 resists the pressure exerted when the chip is sealed with resin 
and thus does not deform. Since electrode pad 14 and lead 13 can be 
bonded, the productivity of semiconductor devices is high. According to 
the TAB technique, however, a bump (projected electrode) 22 needs to be 
formed on electrode pad 14 so that the electrode pad does not contact the 
edge of the chip, and the chip is not damaged by the bonding operation, 
and a special device for forming the bump is required. For this reason, an 
equipment investment in manufacturing process increases the manufacturing 
cost and it is economically difficult to apply the TAB technique to the 
semiconductor device of the present invention whose price is low. 
SUMMARY OF THE INVENTION 
It is accordingly a first object of the present invention to provide a 
resin sealing type semiconductor device which prevents defects from being 
caused by deformation of a wire when a semiconductor chip is sealed in 
resin and which can thus be manufactured at relatively low cost. It is a 
second object of the present invention to provide a resin sealing type 
semiconductor device which suppresses an increase in cost of equipment 
investment in manufacturing process and whose manufacturing cost is 
relatively low, reliability is high and productivity is high. 
To attain the first object of the present invention, there is provided a 
resin sealing type semiconductor device comprising: 
a semiconductor chip having a plurality of electrodes; 
a bed fixed to the semiconductor chip; 
a printed circuit board which is fixed to a periphery of a surface and of 
the bed so as to overhang from the bed and on a surface of which a wiring 
pattern is formed; 
a plurality of lead frames arranged so as to surround the bed; 
first connecting means for connecting the electrodes arranged on the 
semiconductor chip and one end of the wiring pattern formed on the printed 
circuit board; and 
second connecting means for connecting the lead frames and the other end of 
the wiring pattern formed on the printed circuit board. 
With the above structure of the semiconductor device, an interval between 
the bed and each of the leads can be supplemented with the printed circuit 
board which is fixed so as to overhang from the bed and on which the 
wiring pattern is formed. The distance between the electrode pads and the 
printed circuit board is thus shortened. Since the semiconductor chip and 
the leads are connected via the substrate, the reliability of the 
semiconductor device becomes high without adopting the TAB technique 
wherein bumps need to be formed on the chip when the chip and leads are 
directly connected to each other. 
To attain the second object of the present invention, there is provided a 
resin sealing type semiconductor device comprising: 
a semiconductor chip on the surface of which a plurality of electrodes is 
arranged; 
a bed fixed to the semiconductor chip; 
a printed circuit board which is fixed on the bed in the vicinity of the 
semiconductor chip and on which a wiring pattern is formed to be connected 
to the electrodes; 
a plurality of lead frames arranged so as to surround the bed; and 
a wiring of a film carrier type connected to the wiring pattern on the 
printed circuit board and to the lead frames. 
According to this structure of the present invention, no bumps need to be 
formed using the TAB technique in order to connect the printed circuit 
board and the leads. The manufacturing cost of semiconductor devices is 
not increased so greatly, which improves the productivity of the devices. 
If a printed circuit board is connected to leads using the TAB technique 
in a multichip package (MCP) semiconductor device, the reliability and 
productivity of the MCP semiconductor device are improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the present invention will be described with reference to 
accompanying drawings. 
FIG. 3 is a cross-sectional view of the configuration of a resin sealing 
type semiconductor device according to the first embodiment of the present 
invention. Semiconductor chip 32 is die-bonded onto bed 31 of a lead frame 
by solder or conductive epoxy resin. Insulation wiring substrate 33 is 
fixed to an end portion on the surface of bed 31 so as to overhang from 
bed 31. A plurality of desired wiring patterns, not shown, are formed on 
printed circuit board 33, and printed circuit board 33 is used to connect 
lead 34 of the lead frame and semiconductor chip 32 which cannot be made 
close to each other because of processing dimensions. Each of a plurality 
of I/O electrode pads 35 formed on chip 32 is connected to connecting 
terminal 36 of substrate 33 by means of bonding wire 37, and lead 34 is 
connected to another connecting terminal 38 of substrate 33 by means of 
TAB tape 39. Semiconductor chip 32, including printed circuit board 33, is 
then covered with mold resin 40, and part of lead 34 is exposed outside as 
an outer lead. 
According to the first embodiment, in a semiconductor device produced by 
sealing very small semiconductor chip 32 in a package with resin, the 
deformation of bonding wire 37 due to pressure applied when the sealing 
operation is performed, neither causes a short circuit nor affects the 
reliability of the semiconductor device since the bonding wire is short. 
Even if such a bonding wire is used, the yield can be improved. Since 
semiconductor chip 32 and printed circuit board 33 are connected by 
bonding wire 37, no special device is required to form bumps (projected 
electrodes) on I/O electrode pad 35 of chip 32. It is thus only an OLB 
(outer lead bonding) apparatus for connecting printed circuit board 33 and 
lead 34 by TAB tape 39 that is required new equipment. The investment in 
equipment in the manufacturing process can thus be reduced. 
In the semiconductor device whose price is low and in which bumps are 
formed on electrode pad 35 and it is economically difficult to connect 
electrode 35 and lead 34 and by the TAB tape, if printed circuit board 33 
is formed, the semiconductor device can be manufactured with high 
reliability and at low cost. 
Furthermore, since the TAB technique is used to connect printed circuit 
board 33 and lead 34, the productivity of semiconductor devices can be 
enhanced. No bumps need to be formed and thus the manufacturing cost of 
the semiconductor devices is not increased. 
The methods of electrically connecting chip 32 and printed circuit board 33 
and electrically connecting printed circuit board 33 and lead 34 are not 
limited to the first embodiment. For example, as shown in FIG. 4, printed 
circuit board 33 and lead 34 can be connected to each other by a bonding 
wire 41. As illustrated in FIG. 5, the electrical connection of printed 
circuit board 33 and lead 34 can be performed by a forming contact portion 
51 on the undersurface of printed circuit board 33 using a wireless 
bonding technique. It is therefore necessary only to perform a bonding 
operation which is the most suitable for a semiconductor chip. If bed 31 
is small and has no space for fixing printed circuit board 33, board 33 
can be fixed onto the undersurface of bed 31, as shown in FIG. 6. Various 
applications can thus be made to the first embodiment. 
FIG. 7 illustrates an MCP (multi chip package) to which the semiconductor 
chip shown in FIG. 3 is applied. 
As illustrated in FIG. 7, semiconductor chips 55-61 are properly arranged 
and die-bonded onto beds 51-54 of lead frames fixed by hanging pins 50. 
Printed circuit boards 62-65 are formed on beds 51-54 so as to surround 
the semiconductor chips. The printed circuit boards 62-65 overhand the 
beds 51-54 near the handing pins 50. A desired wiring pattern is formed on 
each of the printed circuit boards 62-65 and used to electrically connect 
lead 66 and each of chips 55-61, which cannot be made close to each other 
in view of processing dimensions, and to connect chips 55-61 to one 
another. A plurality of I/O electrode pads 67, formed on the surface of 
each of chips 55-61, is connected by bonding wires 69 to connecting 
terminals 68 of the wiring patterns, which are near the semiconductor 
chips. The connecting terminals of the wiring patterns, which are near the 
periphery of the one of printed circuit boards 62-65, are connected to the 
wiring patterns of other printed circuit boards and electrically connected 
to leads 66. The former connection is performed by bonding wires 70, and 
the latter connection is performed by TAB tapes 71 using the TAB 
technique. TAB tape 71 is obtained by forming lead line 73 plated with 
copper on polyamide film 72 so as to correspond to lead 66. The connecting 
terminals of each of the printed circuit boards 62-65 are connected to 
their corresponding leads 66 at the same time. 
FIG. 8 is a cross sectional view of the MCP shown in FIG. 7 which is sealed 
with resin. In FIG. 8, the same elements as those in FIG. 7 are denoted by 
the same reference numerals. The printed circuit boards are connected to 
each other by bonding wires, and the semiconductor chips are connected to 
printed circuit boards by bonding wires. The printed circuit boards are 
connected to their corresponding leads 66 by TAB tapes 71. The MCP is thus 
sealed with mold resin 81. Like the structure shown in FIG. 3, no bumps 
need to be formed, so the manufacturing cost is not increased, and an MCP 
of a multi-pin structure having a large number of leads 66 is improved in 
reliability and productivity. 
As described above, according to the present invention, a resin sealing 
type semiconductor device whose price is low and reliability is high can 
be provided, and an MCP can be improved in reliability and productivity. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices, shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.