JPS61230364A - Circuit substrate - Google Patents

Abstract

PURPOSE:To obtain a circuit substrate, which is manufactured easily and cost thereof can be reduced largely, by forming an integrated circuit consisting of a large number of thin-film transistors and a dielectric connecting an element connected to the integrated circuit and the integrated circuit onto one organic insulating film. CONSTITUTION:A circuit substrate 10 is manufactured in such a manner that a large number of thin-film transistors constituting each circuit section for an integrated circuit 12 and a solar cell 13 are shaped onto a base film 11, an insulating film 15 coating an integrated circuit 12 section is formed onto the thin-film transistors and the solar cell, and fixed contacts 14, 14... shaping key switches are formed onto the insulating film 15. Each wiring 17-19 shaped onto the base film 11 is formed at the same time as several electrode for the thin-film transistors is shaped, and wirings shaped onto the insulating film 15 are formed at the same time as the fixed contacts 14, 14... are shaped. Accordingly, the circuit substrate can be manufactured in a manner easier than a conventional circuit substrate in which an integrated circuit chip is fitted to a printed wiring substrate, and cost can also be reduced largely.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to a circuit board.

[Technical background of the invention and its problems]

Small electronic calculators, commonly called calculators, electronic clocks,
2. Description of the Related Art Conventionally, circuit boards used in electronic equipment such as radio receivers include printed wiring boards on which wiring in a predetermined pattern is formed and an integrated circuit chip attached thereto.

However, since the above-mentioned conventional circuit boards are attached by bonding (wire bonding or direct bonding) the integrated circuit chip to the printed wiring board, bonding the integrated circuit chip to the printed wiring board is time-consuming. Due to this problem, the above-mentioned conventional circuit board has a problem that it is difficult to manufacture. In addition, since the integrated circuit chip has a large number of transistors densely formed on a silicon substrate of limited size, it requires highly accurate masking for manufacturing, which makes the masking process complicated. Since integrated circuit chips are expensive, conventional circuit boards in which the integrated circuit chips are attached to printed wiring boards also have a problem in that their costs are considerably high.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to make it easier to manufacture and to reduce costs compared to conventional circuit boards in which integrated circuit chips are attached to printed wiring boards. The object of the present invention is to provide a circuit board that can be significantly reduced in width.

[Summary of the invention]

In other words, the present invention provides a method for forming a film on a single organic insulating film.
An integrated circuit consisting of a large number of thin film transistors and a conductor that connects elements connected to this integrated circuit and the integrated circuit are formed. Since it is an integrated circuit made up of a large number of thin film transistors, there is no need to bond and attach the integrated circuit chip as in the past, making it easier to attach the integrated circuit chip to a printed wiring board than the conventional circuit board. can be manufactured. Moreover, the integrated circuit formed on the insulating film can be formed by dispersing it over a wide area on the insulating film.
For this reason, each Wilt' transistor that makes up an integrated circuit can be formed in a large size and without the need for high-precision masking, making it possible to form large numbers of transistors on a silicon substrate with a limited size. Integrated circuits can be formed at low cost, and costs can therefore be significantly reduced.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example a circuit board used in a small electronic calculator.

FIG. 1 shows an exploded view of a small electronic calculator. This small electronic calculator consists of a computer case consisting of a lower case 1 and an upper case 2, and a circuit board 10 to which a liquid crystal display panel 3 is connected. , keyboard sheet 4 are housed therein.

The circuit board 10 has an integrated circuit 12 made of a large number of thin film transistors and a solar cell 13 formed on a single base film 11 made of an organic insulating film such as polyimide, and has a large number of fixed contacts 14.
14. . . . are formed in an array, and the integrated circuit 12
are formed to be dispersed over almost the entire area of the base film 11.

FIG. 2 shows the configuration of the integrated circuit 12, which includes a control section 20 and fixed contacts 14, 14, . . . of the keyboard section 21. ... and an address control section 23a that outputs storage information to the control section 20 in accordance with the input information from the input section 22. , a RAM (random access memory) section 24 that exchanges information with the control section 20, an arithmetic section 25, a display drive section 26 that drives the liquid crystal display panel 3 of the display section 27, and clock pulses to each of the above sections. The operating power for this integrated circuit 12 is supplied from a power supply section 29 connected to the solar cell 13.

As shown in FIG. 1, the integrated circuit 12 includes a control section 20, an input section 22, a ROM section 23, a RAM section 24, a calculation section 25, a display drive section 26, and an oscillation section
The power supply section 29 is also formed on the base film 1.

Further, on the base film 11, a solar cell 13 is provided.
The integrated circuit 12 except for the surface and the connection part of the liquid crystal display panel 3
An insulating film 15 is formed to cover the fixed contacts 14, 14, and 14 of the keyboard section. ... are formed on this insulation 11115.

FIG. 3 is an enlarged cross-sectional view of a portion of the circuit board 10 taken along the line A-A. and these two thin film transistors Ql.

Q2 forms an inverter that constitutes a part of the input section 22.

The sm transistor Q1. Q2 is base film 1
N-type or P-type amorphous silicon 1I30 on 1
P is formed into this silicon film 30 by ion implantation.
At the same time, a gate insulating film 31 is formed on the gate region of the silicon group 30, and gates are formed on the gate insulating film 31 and on the source region and drain region of the silicon film 30, respectively. An electrode 32G, a source electrode 32S, and a drain electrode 32D are formed.
The above inverter is a PNP junction thin film transistor Q1.
and the drain electrode 3 of the NPN junction thin film transistor Q2.
2D is used as a common electrode, and gate electrodes 32G and 32G of the two thin film transistors Q1 and Q2 are connected by a wiring 16 formed on an insulating film 15 thereon.

FIG. 4 shows the circuit of the inverter, in which the source electrode 32S of one thin film transistor Q1 is connected to the Voo side, and the source electrode 32S of the other thin film transistor Q2 is connected to the Voo side.
28 is connected to the Vss side, and both thin film transistors Q
1, the drain electrode 32D of Q2 is connected to the output side 0LJT, and the gate electrode 32G of both thin film transistors Ql, Q2.

The conductive film 16 connecting 32G is connected to the input side (here, the key switch SW of the keyboard section).

As shown in FIGS. 1 and 3, the key switch SW of the keyboard section includes a fixed contact 14 consisting of a pair of contact electrodes 14a and 14b formed on the insulating film 15, and
The pair of contact electrodes 14a.

14b, and the movable contact 5 is formed on the keyboard sheet 4 which is placed over the circuit board 10. This keyboard sheet is made of a single rubber sheet, and elastically deformable key portions 4a that bulge upward are provided at portions of the rubber sheet corresponding to the fixed contacts 14, 14, . 4a,
. . . are formed, and the movable contact 5 is formed at each of these portions 4a, 4a.

It is formed on the bottom surface of the top of... That is, the movable contact 5 is brought into contact with the pair of contact electrodes 14a and 14b by the downward elastic deformation of the key part 4a when the key part 4a is pressed down with a finger, and this causes the key switch SW to is turned ON. Note that the fixed contacts 14, 14. One contact electrode 14a forming the inverter input side of the input section 22 (two thin film transistors Q1).

Wiring 16) connecting gate electrodes 32G and 32G of Q2
The other contact electrode 14b is connected to the reference potential side.

On the other hand, solar cells 13 formed on base film 11
Although the structure is not shown, an amorphous silicon film is formed on an electrode formed on a base film 11, and a transparent electrode is formed on the amorphous silicon film. It is connected to the power supply section 29 by a wiring 17 formed above.

In addition, the power supply section 29 and each circuit section of the integrated circuit 12 (control section 20, input section 22, ROM section 23, RAM section 24, arithmetic section 25, display drive section 26, and oscillation section 28) and these circuit sections are connected to each other by wiring lines 18, 18, . Panel connection wiring 19.19. ... is formed.

The liquid crystal display panel 3 has a film-like flexible connector 6 that connects the terminal arrangement section of the liquid crystal display panel 3 to the arrangement section of display panel connection wiring 19, 19, . . . on the circuit board 10.
The liquid crystal display panel 3 is connected to the display drive section 26 of the integrated circuit 12 by a flexible connector 6.
By bending the solar cell 13, the solar cell 13 and the solar cell 13 are stacked on the circuit board 10.

Incidentally, the upper case 2 of the computer case has each key part 4a of the keyboard sheet 4 in the keyboard section.

4a, ... is inserted into the open lower part, 7. ... are arranged and formed, and the liquid crystal display panel 3 and the solar cell 13
A display window 8 that also serves as a lighting window for the solar cell 13 is formed in a portion corresponding to the solar cell 13 .

Next, a method for manufacturing the circuit board 10 will be explained.

This circuit board 10 has a large number of 'nm transistors and solar cells 13 constituting each circuit section of an integrated circuit 12 formed on a base film 11, and an insulating film 15 covering the integrated circuit 12 section formed thereon. Afterwards, fixed contacts 14.14. forming a key switch are placed on this insulation 1115. The wirings 17, 18, 19 formed on the base film 11 are formed simultaneously with the formation of the electrodes 32G, 328, 320 of the thin film transistor, and The wiring 16 formed in the fixed contacts 14.14. Formed at the same time as...

FIG. 5 shows the method of forming a thin film transistor on the base film 11 in the order of steps, and here shows the step of forming a PNP junction thin film transistor.

To explain the process of forming this thin film transistor, first,
N is deposited on the base film 11 by plasma CVD method.
A type of amorphous silicon is deposited and etched to form an N-type amorphous silicon layer 30 having a predetermined area as shown in FIG. 5(a).

Next, the central part of this N-type silicon layer 30 (the part that will become the gate region) is masked with a resist 40 as shown in FIG. 5(b), and from above, for example, as shown in FIG. Boron ions B+ are implanted to form P-type regions (source and drain regions).

Thereafter, as shown in FIG. 5(d), the resist 40 is peeled off, and SiO2 is deposited on the entire surface of the silicon film 30 by plasma CVD or sputtering to provide gate insulation as shown in FIG. 5(e). 1131 is formed, and then this gate insulating film 31 is etched as shown in FIG. 5(f).
Openings are formed to expose the source and drain regions as shown in FIG.

After this, the base film 11 is sputtered.
Then, a metal bridge is formed on the entire surface of the silicon 1130, and this is patterned by etching to form a gate electrode 3.
2G, a source electrode 328, and a drain electrode 32D are formed.

The surface temperature of the base film 11 during deposition of the amorphous silicon is approximately 200°C, the temperature during boron ion implantation is approximately 150 to 200°C, and the temperature during SiO2 deposition is approximately 300°C. If polyimide having a high heat resistance temperature (heat resistance temperature of about 400 to 450° C.) is used, the base film 11 will not be thermally deformed in the above steps.

However, in this circuit board, since the integrated circuit 12 consisting of a large number of thin film transistors is formed on the base film 11 itself, which is the base material of the circuit board, as described above, the integrated circuit chips cannot be bonded as in the conventional method. There is no need to mount the integrated circuit on a printed circuit board, and therefore it is easier to manufacture than a conventional circuit board in which an integrated circuit chip is mounted on a printed wiring board. Moreover, in this circuit board, the integrated circuits 11 configured on the base film 11 are formed by being dispersed over a wide area on the base film 11.
Each of the thin film transistors constituting each circuit part of the integrated circuit 11 can be formed in a large size without requiring high-precision masking, and therefore a large number of transistors can be formed at high density on a silicon substrate of limited size. Since the integrated circuit 12 can be formed at a lower cost than semiconductor chips, the cost can also be significantly reduced.

Moreover, in this circuit board, the solar cell 13 which is an active element
Since the integrated circuit 12 is formed on the base film 11 itself in connection with the integrated circuit 12, the conventional step of attaching the solar cell to the printed wiring board can be omitted.

In the above embodiment, the liquid crystal display panel 3 as a display element is connected to the base film 1 by the flexible connector 6.
Display panel connection wiring 19 formed on 19.19.・・・
・However, the liquid crystal display element is connected to base film 1.
In that case, the display driving section 26 of the integrated circuit 12 and the liquid crystal display element may be directly connected by a conductor such as a wiring formed on the base film 11.

Further, in the above embodiment, a solar cell is used as the power supply battery, but the power supply battery may be a lithium battery or the like, and in that case, a battery connection electrode is formed on the base 7' ILMCO 1. Just leave it there.

Furthermore, in the case where a temperature sensor made of a 1111 semiconductor, an EL (electroluminescence) backlight that illuminates the liquid crystal display panel 3, etc. are provided as active elements, these active elements are also attached to the base film 11. I explained about the circuit board of the formula calculator,
This invention is applicable not only to small electronic calculators but also to circuit boards of electronic clocks, radio receivers, etc. For example, the present invention can be applied to circuit boards of devices such as radio receivers equipped with sound emitting elements such as speakers. In this case, a conductor for connecting the sound emitting element to the integrated circuit may be formed on the base film.

(Effects of the Invention) This invention forms an integrated circuit including a large number of thin film transistors on a single organic insulating film, and a conductor that connects elements connected to this integrated circuit and the integrated circuit. Therefore, it can be manufactured more easily than a conventional circuit board in which an integrated circuit chip is attached to a printed wiring board, and the cost can be greatly reduced.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; Fig. 1 is an exploded perspective view of a circuit board and a small electronic computer using this circuit board, and Fig. 2 shows an integrated circuit circuit formed on the circuit board. Figure 3 is an enlarged sectional view taken along the line A-A in Figure 1, Figure 4 is a circuit diagram of an inverter consisting of two thin film transistors shown in Figure 3, and Figure 5 is a diagram of the process for forming the thin film transistors. be. DESCRIPTION OF SYMBOLS 1... Lower case, 2... Upper case, 3... Liquid crystal display panel, 4... Keyboard sheet, 10... Circuit board, 11... Base film, 12... Integrated circuit, Ql, Q2... thin film transistor, 13... solar cell, 19... display panel connection wiring, 20...
Kindergarten system department, 22... Input section, 23... ROM section, 24
. . . RAM section, 25 . . . Arithmetic unit 26 . Applicant's representative Patent attorney Takehiko Suzue Figure 2 3mm

Claims (1)

[Claims] A circuit board characterized in that an integrated circuit consisting of a large number of thin film transistors and a conductor connecting elements connected to this integrated circuit and the integrated circuit are formed on a single organic insulating film.