CA1037149A - Electronic apparatus equipped on a flexible substratum - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The electronic apparatus disclosed comprises a display unit, a mechanical contact type keyboard unit and several LSI
(large-scale integrated circuit) elements including a computation circuit, a logical control circuit, a storage circuit, a program memory circuit, and other components. These units and elements are all incorporated on a single flexible plate of electrically insulating material such as a film of polyethylene-terephthal or polyamide. The metal depositing technology or the etching tech-nology is applied to form a wiring pattern on the flexible plate.
The LSI elements are directly mounted on the single flexible plate by utilizing the wireless bonding method, for example, such as flip chip bond or beam lead bond before these elements are packed and sealed. The substratum may be secured inside the apparatus in a serpentine fashion in order to make the best use of the inside space of the apparatus. Since the display units are mounted on the flexible plate, it is easy to adjust the angle or position of the display units with respect to the keyboard unit.

Description

~037~49 The present invention relates generally to an elec-tronic apparatus. More specifically the invention relates to an electronic calculator of convenient size.
This is a divisional application of serial number 201,557 filed June 4, 1974.
Recently, the technology of integrated circuits has achieved great advances and the size of electronic calculators has been substantially reduced. A computation circuit, a logical control circuit, a storage circuit, a program memory ; 10 circuit, and other components were included in the LSI (large-scale integrated circuitl. The LSI elements, a display unit and a mechanical contact type keyboard unit were incorporated on a single solid plate of electrically insulating material and in this way an electronic calculator was fabricated on a single plate such as a glass plate.
The conventional substratum, for example, made from cera-mics or epoxy resin was basically inflexible. However, a flex-ible film of polyethylene-terephthal or polyamide has been found most useful as a substratum. For example, the flexible substratum is suitable for apparatus which requires a substantial reduction in size. A number of wiring members on the flexible film is formed in a desired pattern by utilizing the metal depositing ; technology such as that which precipitates or plates metal on such films, the etching technology which eliminates metal attached to such films, and other techniques.
A new method has been developed as an advance over the conventional IC package method, wherein an IC chip is mounted on a film plate by utilizing the bonding method, and the output sig-1037~49 nals therefrom or the input signals thereto are transported viaa wiring pattern provided on the film plate. By utilizing the combinations of the above-mentioned technologies, an electronic calculator may be equipped on a single film when the various kinds of chips are directly mounted on the single film, if a good yield is achieved in the chip bonding technology. The manu-facturing processes are therefore suited for mass production at relatively low cost since the processes may be automatically controlled by utilizing conventional technology such as technol-ogies of chip bonding and film catting.
A concept of the electronic apparatus equipped on the flexiblesubstratum was described in THE E~ECTRONIC SCIENCE, Vol. 22, No. 2 issued in Japan. However, in accordance with the conventional concept, the components mounted on the flexible substratum were IC packages or discrete elements, and the mounting thereof was performed by soldering. The soldering positions had to be fixed by the addition of reinforcing plates.
An object of the present invention is to provide an elect-ronic apparatus wherein various kinds of chips are mounted directly on small film plates, that is to say, daughter boards, respectively, and the daughter ~Joards are physically connected to a single film plate, that is to say, a mother board, which is provided with a wiring pattern thereon.
According to the present invention an electronic apparatus includes a flexible mother board carrying a wiring pattern formed thereon; a plurality of flexible daughter boards connected to the mother board; a plurality of function units, necessary for the desired function of the apparatus, formed directly onto the flexible daughter boards; and a keyboard unit formed on the mother board.

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IC chips may be directly mounted on a film plate by utilizing the wireless bonding method such as the method of flip chip bond or beam lead bond. It is possible to bend the film plate even at the peripheral position on which the chip is mounted. In addition, it is desirable in order to put the con-cept of the present invention into a mass production form that certain problems be considered. For example, it is necessary to determine how to incorporate the mechanical contact type keyboard unit on the flexible plate as one body. Additionally, it should be determined how to make the best use of the advantages of using the flexible film for the substratum. Furthermore, one should decide how to construct the apparatus taking the yield of the chip bonding into consideration.
Approacheq which seek to overcome the above-mentioned problems will be disclosed in greater detail hereinafter.
Other objects and the further scope of applicability of the present invention will become apparent from the following description. It should be understood, however, that the descrip-tion and specific examples, while indicating preferred embodi-~ ments of the invention, are given by way of illustration only,since variou$ changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The accompanying drawings are given by way of illustra-tion only of examples of the present invention and in which:
FIGURE 1 is a cross-sectional view of an embodiment of an electronic desk-top calculator;
FIGURE 2 is a plan view showing the embodiment of Figure l;

FIGURE 3 is a cross-sectional view of another embodiment of an electronic desk-top calculator;
FIGURE 4 is a perspective view of an embodiment of a flexible substratum carrying a wiring pattern formed thereon;
FIGURE S is a partially enlarged perspective view of the part V of Figure 4;
FIGURE 6 is a cross-sectional view showing an embodiment of chip bonding technology;
FIGURE 7 is a partially enlarged plan view of the wiring pattern on the substratum; and FIGURES 8 through 11 are cross-sectional views showing ways of connecting the two wiring patterns on different substrata.
Referring now to Figures 1 and 2, an electronic desk-top calculator is comprised mainly of three major components, a mechanical contact type keyboard unit 10 including a plurality of key tops 102 and their associated key contacts 104, a cell ca5e 12, and a flexible substratum 14 including key contact patterns 142, IC chips 144, 146 and display units 148 thereon.
These components are secured in a housing 16. A flexible film is used for the substratum. Both the key contact patterns and a wiring pattern among the elements are simultaneously formed on a single plate in continuous fashion and in this way effective electrical connection may be obtained therebetween without a multi-'æin terminal. Moreover, the portion of the sub-stratum 14 where the IC chips 144 and 146 or the display units 148 (preferably LED chips) are mounted, is flexible in the hous-ing 16, although the other portion where the key contact patterns are mounted should be fixed in order to make good contact with 103~7i49 the key contacts 104. More particularly, the display units 148 are adjustable as regards their place and their angle with res-pect to the position of the operating panel of the keyboard unit 10. The display unit 148 is provided with a transparent window-pane 18. The flexible substratum 14 is connected to the power source via pins 161 provided at one end of the substratum.
Figure 3 shows another embodiment of a calculator where-in like elements corresponding to those of Figure 1 are indicated by like numerals. The configurations of the apparatus of Figure 3 is adapted to make good use of the advantage of using the flex-ible film as the substratum. A casing cover 162 is rotatably mounted about a shaft 164, while the display units 148 are fix~d at the casing cover 162, thereby making a display angle thereof adjustable. The casing cover 162 is turned to close and open the casing 16 when necessary, since the substratum 14 is flexible, even though the substratum 14 is continuous and made of a single film., Figure 4 shows a wiring pattern formed on the flexible substratum. The key contact patterns 142 are of a configuration 20 suited for making good contacts with the key contacts 104 of the keyboard unit 10. , When the key tops 102 are manually depressed, the key contacts 104, which are made of conductive rubber or phosphor bronze springs, come into contact with the key contact patterns 142. A suitable configuration of the key contact pat-terns 142 is shown in Figure 5 which is a partially enlarged perspective view of the part V of Figure 4.
Manually introduced information is applied to the comput-ation circuit chip 144 (CPU LSI) via the key contact patterns 142, 10371~9 and the operation outputs thereof are applied to the decoder and driver chip 146 for display. The control chip 147 for controll-ing, for example, the timing signals for the computation circuit chip 144 and the decoder and driver chip 146 is unavoidable even with the present day technology, although the necessary number of the chips is not a matter of importance in view of the prin-ciple of the invention. Outputs of the driver chip 146 are applied to the display units 148.
Pins 161 are provided at the one end of the substratum 14 for connecting the wiring on the substratum to the power source secured within the cell case 12. The substratum 14 is fixed to the casing 16 with the use of holes 152. Perforations 154 are provided at both sides of the substratum 14 for assisting in conveying the substratum during the process of mass production.
The belt of the substratum i9 wound as a roll. The belt is prop-erly fed from the roll and the computation circuit chip 144, the decoder and driver chip 146, the display units 148, etc. are dir-ectly mounted thereon by utilizing the wireless bonding method at the appropriate positions on the substratum. Thereafter, the elements are packed and the belt is cut to separate the individual substratum }4.
Referr$ng now to Figure 6 ~howing an embodiment of a chip bonding, a wiring pattern 30 has been formed on the substratum 14 by utilizing the metal depositing technology. The face down bonding technology is applied to mount the IC chip 144 on the substratum and to connect the IC chip to the wiring pattern via bumps 32. Thereafter, the surface of the chip is sealed with the use of molded resin 34 for protecting the chip from damage from the outside.

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1037~49 Although there are some technical problems associated with manufacture of the individual components, these problems can be solved one by one by virtue of present developments and manu-facturing processes. Therefore, in a situation where all the functional units are fabricated on a single flexible substratum in accordance with the teachings herein, only the total yield of the manufacturing of the apparatus should be consid~red.
Figure 7 shows a wiring pattern suited for making substi~
tution of defective chips easy.
Wiring patterns formed on two different substrata are able to be ea~ily connected in a manner that the two films are lapped or the wiring patterns are so arranged as to make salients from both substrata and the corresponding salients are connected respectively, since the wiring patterns on the film are formed by utilizing the metal depositing technology, compression bonding technology, etc. Moreover, the defective portion is removable by cutting the film at the appropriate position.
It will be noted that a boundary area 26 between a film 22 ~ecures a chip 20 thereon which corresponds to the bottom of a conventional IC package. As previously described, the substratum film 24 is provided with a wiring pattern formed thereon. ~oth the films 22 and 24 may be physically separated from each other, the former bein~ referred to hereinafter as a "daughter board"
and the latter as a "mother board". Test pads 220 and 240 are provided on both films in such a manner that they face each other. The test pads 220 and 240 are used for putting the IC
chips into the test conditions in a manner similar to that used for the conventional IC packages provided on an inflexible plate.

; If the film lapping technology is applied for connecting the two films, the boundary area 26 and machine sewed lines 260 will be-come unnece~ary.

1~3 7149 ~
The machine sewn lines 260 are provided for the purpose of removing the daughter board carrying the defective IC chip from the mother board, when necessary. The lines 260 may prove very useful in those situations when it is necessary to remove the daughter board with considerable frequency.
It will be apparent that the positions of the test pads 240, 220 are not limited to the peripheral area where the IC
chips are mounted. It is appropriate for maintaining and check-ing the apparatus, to provide each pair of facing test pads at the desired points suitable for checking within the actual appar-atus.
Under these circumstances, it is suitable for the fabric-ation of the apparatus to use a mother board having a wiring p~t-tern formed thereon and a daughter board on which IC chips are mounted. Figures 8 through 11 inclusive show various ways for establishing connection between the mother board and the daughter board wherein like elements corresponding to those of Figure 7 are indicated by like num~rals.
In some cases the above-described test pads are not suit-able for the apparatus since they occupy large areas. In prac-tical use special test pads are not provided, and the wiring paths are enlarged to a width sufficient to provide room for soldering or painting conductive adhe~ive.
The electrical connection between the mother board 24 and the daughter board 22 may be achieved, for example, in any one of a number of ways. For example, one way is the provision of con-ductive salients 231 formed by extensions of the wiring pattern 241 on the mother board 24 or the wiring pattern 221 on the daughter board 22. The salients are connected to the correspond-~037149 ing wiring pattern, as shown in Figure 8. Another way consistsof the positioning of the daughter board 22 adjacent the mother board 24 and the connecting of the wiring patterns 241 and 221 on both boards together with the use of solder or conductive adhe-sive 230, as shown in Figure 9. Figures 10 and 11 show another method of coupling the both boards to each other, wherein both boards are overlapped in a manner that the wiring patterns on the boards are directed to each other as shown in Figure 10 or dir-ected in the same direction as shown in Figure 11. The electrical connection is achieved via the solder or conduc~tive adhesive 230.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations should not be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included wlthin the scope of the following claim.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electronic apparatus including a flexible mother board carrying a wiring pattern formed thereon; a plurality of flexible daughter boards connected to the mother board; a plurality of function units necessary for the desired function of the apparatus, formed directly onto the flexible daughter boards and a keyboard unit formed on the mother board.