CA1038964A - Calculator construction and method for making calculator - Google Patents

Abstract

ABSTRACT
An electronic calculator comprises mainly a multi-digit liquid crystal display unit, a mechanical contact-type keyboard unit and a semiconductor circuit unit including a computation circuit, logical control circuit, storage circuit, program memory circuit, etc, these units all being provided on a single plate of electrically insulating material. The plate is one of a pair of spaced-apart electrically insulating plates forming a capacity for the liquid crystal composition, is of a length sufficient to support all the constitutional units, and has two major surfaces, one for supporting the keyboard unit and the other for supporting the semiconductor circuit unit. Connec-tion between the keyboard unit and semiconductor circuit unit is accomplished by any conventional method, for example, multi-terminal connectors, conductively material printing, through holes, wire bonding, etc.

Description

This invention relates generally to an electronic calcu-lator and more particularly to the construction and fabrication of an electronic calculator.
In prio~ art calculator design, constitutional functional units of a calculator, namely, a display unit employing fluores-cence indicator tubes, light-emitting diodes, etc. a semiconduc-tor circuit unit including various arithmetic and logic circuit elements, and a key input unit for manually introducing func-tional commands into the semiconductor circuit unit, are clearly distinct components and the individual components or units are connected together by a number of lead wires. The components or units coupled in such manner are then housed in a single case, thereby completing fabrication of the calculator. Although the calculator thus fabricated can be viewed as a unitary system from the outside, these components in practice are physically indepen-dent from each other except at their electrical connections.
- Furthermore, an unnecessary area is required to enable wiring and soldering of the connections between the individual components.
For these reasons, difficulties have been encountered in arriving at an electronic calculator construction having not only the re-quired reliability of electrical connections but also a suffici-ently small size to be practical for use in a battery-powered calculator. In addition, the manufacturing processes therefor -are complex and not well suited for mass production.
;~ It is therefore an obiect of this invention to provide a , novel electronic calculator which provides a reduction in size, an improvement in reliability and greater simplicity in fabrica- -. ~ . .
~ tion.
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i According to one aspect of this invention, there is pro-,. , vided an electronic calculator comp~ising a first functional ~nit ~ ~

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for introducing into the calculator input signals associated with desired calculations, a second functional unit for performing the desired calculations in response to the introduced input signals, a third functional unit for displaying the results of the calcu-lations, and a common substrate on which the third functional units and at least part of the first functional units are direct-ly formed and on which the second functional unit is directly mounted.
According to another aspect of this invention there is provided an electronic calculator comprising a dielectric sub-strate, a display unit directly formed on the dielectric sub-strate, a semiconductor circuit unit including at least one com-putation function circuit, the semiconductor circuit unit being directly mounted on the dielectric substrate, and a keyboard unit including stationary contacts directly formed on the dielectric substrate.
- This invention also provides a method of making an elec-tronic calculator, comprising the steps of preparing a dielectric substrate, forming a liquid crystal display unit directly on the dielectric substrate, mounting a semiconductor circuit unit in-cluding at least a computation circuit directly on the dielectric substrate, and forming at least part of a keyboard unit directly on the dielectric substrate.
The invention will be more readily understood from the following description of preferred embodiments thereof given by way of example with reference to the accompanying drawings, in which:
Figure 1 is a sectional side view of an electronic calcu-lator embodying the present invention;
Figures 2 and 3 are perspective views of spaced-apart i - 2 -, .

-. ~038964 components of the electronic calculator of Figure l;
Figure 4 is a plan view of the electronic calculator during a manufacturing process;
Figure 5 is a sectional view of a keyboard unit employed in the electronic calculator.
Figure 6 is a flow chart showing a sequence of fabrica-tion processes for making the electronic calculator in accordance with the teachings of this invention.
Referring now to Figure 1 which illustrates one form of an electronic calculator embodying this invention, a substrate 1 is constituted by a portion of an electrode supporting plate ex-tending from within a liquid crystal display unit 2 and is made of dielectric material, for example, such as glass, ceramic, plastics and so forth. A semiconductor circuit unit 3 containing ' various circuit elements and interconnections therebetween is directly mounted on a major surface or rear surface A of the sub-strate 1, while a keyboard unit 4 is directly mounted on the other major surface or front surface B. The liquid crystal dis-play unit 2, the semiconductor circuit unit 3 and the keyboard -unit 4, which are unified as a single component on the same plate 1, are accommodated in a housing or casing 5 of, for example, plastics material. The housing 5 has an upper portion 6, a lower -- portion 7 and a hood 8 for opening and closing an indication sur-face of the display unit 2 when necessary. A plurality of open-; ings are formed in the housing upper portion 6 to accommodate ~- -- push buttons therein.
The hood 8 may rotate within a predetermined angle (e.g. - ;
45) about an end portion of the housing 5 connecting the upper ~ -and lower portions 6, 7 and, in the illustrated embodiment, is -provided with a window or transparent portion ~ to ensure that .:

ambient light beams are enabled to irradiate the indication sur- -face of the display unit 2 when the hood 8 is in the open posi-tion. The transparent portion 9 preferably consists of plastics ~ -material with a lens shape. Surrounded by the housing upper and lower portions 6, 7, at the other end of the calculator system there is a cavity 10 to accommodate a power cell 11 therein. In order to reduce power dissipation, provision is made for automa-tically enabling power supply to the circuit unit 3 and the dis- -play unit 2 when the hood 8 is in the open position and automati-cally inhibiting power supply when the desired arithmetic opera-tions are completed and the hood 8 is closed. This provision is accomplished by installation of a switch (not shown) associated with opening and closing movements of the hood 8. ~-Details of the liquid crystal display unit 2, the semicon-ductor circuit unit 3 and the keyboard unit 4 generally illu-strated in Figure 1 will be clParer from the following detailed `,t~ ' description with reference to Figures 2 to 5, inclusive, thereby -' to facilitate understanding of the present calculator.
Figure 2 is a perspective view illustrating the liquid crys-tal display unit 2 and the semiconductor circuit unit 3 directly formed on the rear surfaces A of the substrate 1. As previously described, the multi-digit display unit 2 comprises a plurality of liquid crystal display elements of the known construction which has, for example, a layer of nematic liquid crystal composition of a type that scatters light due to turbulence in the layer cre- -ated by the application of a voltage across the layer. On the transparent substrate 1 there are formed individual segment elec-' trodes 12 each consisting of a transparent conductive film such as SnO2, In203 and provided with electrode leads 13. In this manner, the substrate 1 also forms a transparent electrode sup-porting plate for the liquid crystal display mit.

~;. ~ - ,, , : , ~0;~8964 Interconnections 14 between the liquid crystal display unit 2 and the circuit unit 3 are made in the desired intercon-nection pattern over the whole surface of the substrate 1 by the use of thick film printing technology known in the art. It is preferable that multi-layer interconnections (two layers) 15 are employed with a dielectric material interposed therebetween to increase the density of interconnection. These multi-layer in-terconnections can be seen from the outside because the dielec-tric material is of, for example, semi-transparent low melting-point glass. Connection holes 16 serve to enable connection be-tween the upper and lower films within the multi-layer intercon-nection. It is, in fact, difficult for the electrode leads 13 for the individual segment electrodes 12 to be arranged side by side so as to extend in only one direction in view of the align-ment and the number of the segment electrodes 12. Consequently, a space 17 is disposed at one end of the display unit are~ in -~
- which space the electrode leads 13 are formed, which are con-nected to the semiconductor circuit unit 3 at both sides 18 of the display area. The interconnections extending through both - 20 sides are formed of transparent conductive film.
After such formation of the individual segment electrodes 12 and interconnections 14 (interconnections within the circuit unit 3 will be described later) on the substrate l, a glass plate 21 is attached and adhered through a spacer 20 in a position cor-responding to the display unit area. The substrate l having the :
segment electrodes 12 formed thereon serves as a first electrode supporting plate while the glass plate 21 as a second electrode supporting plate. Conventio~Al vapor deposition and other methods can be used in applying a common reflective electrode 22 for e:ch digit display element on the glas~ plate 21. The first : .: ' . , - : . : . .

and second electrode plates 1, 21 and the spacer member 20 toge- -ther form a cavity for the nematic liquid crystal composition.
The reflection-type liquid crystal display unit 2 is provided in this way. The spacer member 20 may be either dielectric material such as mica, polyethylene telephthal film, or a bonding agent such as glass frit. The common electrodes 22 deposited on the second plate 21 extend to the predetermined interconnections 15 on the substrate 1 through electrode leads 23 on the glass plate 21 and silver paste on connection pins 24. In the illustrated embodiment of this invention, the electrode leads for the liquid crystal display unit 2 are all introduced on the same substrate 1 `~
and are appropriately connected to various other components or units. The liquid crystal display unit provides, for example, eight-digit digital indication as well as indicating sign symbols +, - or constant calculation symbols K at the extreme right (or left) position. With such arrangement, the display unit 2 will provide a visual indication of operation results in response to enable signals from the semiconductor circuit unit 3.
On the other hand, the semiconductor circuit unit 3 com-prises several LSI (large-scale integrated circuit) element 25, 25' and interconnections 26 formed in a desired pattern on the substrate 1 by thick layer printing. Provision for the intercon-; nections 26 can be accomplished by printing and sintering gold paste on the substrate 1. Also, multi-layer interconnections may be employed if necessary. The LSI elements 25, 25' are installed on the substrate 1 by soldering in such a manner that the indivi-dual leads thereof are connected to previously plated solder lay ers 27, which in turn are connected to the interconnections.
More specifically, in contrast with convention LSI packages, the LSI element 25 illustrated in Figure 2 has non-projecting signal , : ; . ' . ' ~' ~ .

leads 28 which are previou ~y3c~t6e~ with solder. The LSI ele-ment 25 is first deposited on the substrate 1 in such a way that the individual leads 28 are in physical contact with the solder layers 27. Joint points are coated with soldering paste and heated by a soldering iron so that the solder is well melted about the points of contact to provide electrical good connec-tions therebetween. A sequence of these treatments needs a less-er amount of solder and allows for easy soldering connections.
The interconnections associated with the liquid crystal -display unit 2 and the semiconductor circuit unit 3 are formed at the same time by utilizing thick-layer printing with gold paste or other materials. It is therefore not necessary to form these interconnections in separate processes. If thick layer printing -~
is performed after adhesion of low melting-point glass frits on the substrate 1, then very tight coupling will be resulted be-tween the printed interconnection layers and the substrate. In addition, the interconnection layers can be sealed with low melting-point glass for ensuring improvements in electrical iso- ~ ;~
lation and resistance to wear. Check terminals 29 are provided -.
for sensing signals which occur in the semiconductor circuit unit 3.
Figure 3 is a perspective view illustrating the construc-tion and arrangement of the keyboard unit 4 directly formed on the front surface B of the substrate 1. The keyboard unit 4 illustrated there comprises comb-shaped electrodes 31 for key `
switches or contacts formed by thick layer printing using gold paste, silver paste or other proper materials, a plurality of - signal terminals 32 for key coupling to the circuit unit 3, seve-ral power accepting terminals 33 and ground terminals 34 for a common spring plate to be described later. Guide lines may be .' ~ ~' .

-, ' '' ' written in the course of the thick layer printing for the deposi-tion of contact electrodes 31 to assist installation of rubber switch contacts to be described later on the substrate 1. Need-less to say, the contact electrodes 31, the signal terminals 32 - and the power accepting terminals, but not shown in the drawing, are connected together by the thick layer printing, and directly formed on the substrate together with the ground potential termi-nal 34 and the guide lines 35 at the same time after the printing - and sintering procedures. One way of forming connections between individual units directly formed on both surfaces A, B of the substrate 1 is to employ a multi-pin connector 36 comprised of a diaelectric film 36 and a set of "U"-shaped shunting pins 38 each being in contact with the individual signal terminals 32. Provi-sion of such connector 36 enables arithmetic instruction signals originated in response to key depression to be transferred to the -- semiconductor circuit unit 3 directly formed on the rear surface A of the substrate 1 via the individual shunting side pins 38.
It will be noted that other conventional methods, for example, such as conductive material printing, through holes, wire bonding may be employed. A power supply circuit (in this example, AC-DC
- converter) until board 39 is positioned adjacent one side of the substrate 1 and serves as a carrier to which various power cir-cuit parts or elements associated with the cell 11 are secured, these power circuit parts or elements being electrically con-nected by a coupling arrangement including a dielectric film 40 and conductive pins 41 inserted in holes 43 in the board 39, such that the specified points in the power supply circuit are elec-~rically coupled to the power accepting terminals 33 on the ront s~rface B and to predetermined points on the rear surface A.
Scl~er welding is carried out about ln~ holes 43 for c~p'ina . .

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~0;~8964 between the pins 41 and the power board 39. In the illustrated embodiment, one end portion of the power board 39 extends, as shown in Figure 4, beyond the substrate 1, and the cavity 10 which the power cell 11 and holder 44 are housed in is formed by a space adjacent such extension portion of the board 39. The re- :
lative positions of the cell 11 and the power board 39 with res- -pect to the substrate 1 will be best understood from Figure 4, wherein the key electrode areas are all covered with a single rubber plate 45.
The rubber plate 45, which comprises a dielectric rubber ;
base 46 having a predetermined number of dome-shaped projections ~ :
46' (Figure 3) and conductive rubbers 47 (Figure 5) tightly affixed to the inner wall of the projections 46', cooperates with the comb-shaped electrodes directly formed on the front surface B
to constitute a predetermined number of key switches of the key-board unit 4. The rubber plate 4S is precisely positioned by utilizing the guide lines 35 and directly adhered to the major surfac~ ~ of the substrate 1 except at the dome-shaped projec-tions 46'. In addition to these parts or elements, the keyboard unit 4 includes a common spring plate 48, a common reinforcement plate 49 and push buttons 50. The common spring plate 48 is made ..
of thin and elastic steel plate and spring areas 51 thereof are .
each of spiral configuration having a pair of pivot axes to .
afford snap action thereto. Each push button 50 has a downwardly directed leg 52 which is movably inserted in a central hole with~
in the spring area, as illustrated in Figure 5.
The individual spring areas 51 are provided at positions corresponding to the dome-shaped projections 46' of the rubber plate 45. With this arrangement, when one of the push buttons 50 is manually operated, the corresponding dome-shaped projection - :
' .. ,,, ,.. -_ g _ ., ;: :

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` ' :b ' . ~ - it~ f ,: ~
. ... ' ' . ' " '.. ' .
. . ', . ', .' ', ' . . ,' , ' , ' . ' 46' is pressed downwardly by the corresponding leg 52 with spring snap action, so that the pair of comb-shaped electrodes 31 is electrically shunted by the conductive rubber 47. Afterward, when the push button 50 is free from manual depression, it is re-turned to the original position under the snap action and the pair of key electrodes 31 comes to the non-shunted state. The -reason for employing the key springs incorporated as a single component rather than separate components is to prevent electro- ~ -static charge stored in human body from being transmitted and in-10 troduced to the semiconductor circuit unit 3 through a key arrangement. To this end, a connection is provided between a ground portion 53 of the spring plate 48 and the ground terminal 34 on the substrate 1. The pivot axes within the spring areas 51 are oriented in different directions in order that the extremely ~ -thin spring plate 48 is not curved in one direction. The common spring plate 48 and the reinforcement plate 49 are secured toge-- ther to the upper cabinet 6 by screws 55 or the like passing through holes 54. -As noted earlier, in the illustrated example of this in-vention the display unit 2, the semiconductor circuit unit 3 and the keyboard unit 4 are each directly formed on the major sur-faces of the substrate 1. Upon depression of one of the push buttons 50, an arithmetic instruction signal originated from the corresponding key electrode pair 31 is entered into the semicon-ductor circuit unit 3 on the rear of the substrate via the shunt-ing connector 36 to carry out the desired arithmetic operation.
The result of the operation will be visually indicated by turbu-lence created within the nematic liquid crystal upon the applica-tion of a voltage between the liquid crystal display electrodes.
Figure 6 illustra~es a sequence of procedures for making . . -- 1 0 , .

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the calculator of the construction described above.
First of all, small and large pieces of glass are pre-pared as the glass plate 21 and the substrate 1. The segment electrodes 12 and the electrode leads for the liquid crystal dis-play unit 2 are simultaneously applied to the substrate 1 by em-ploying transparent conductive film deposition technology (step I) and then various thick layer interconnections are formed at the same time on both major surfaces by the known thick layer -printing method (step II). It should be noted that such formed -interconnections include interconnections within the semiconduc-tor circuit unit 3 and the predetermined number of the key con-tact electrodes within the keyboard unit 4. In the practice of the thick layer printing method, for example, conductive pastes for both the major surfaces are respectively printed at different times and then the conductive pastes on both the surfaces are sintered at the same time through a furnace. Meanwhile, the alu-minum deposition is used to form the common electrodes 22 on the glass plate 21 (step III).
- The thus-prepared glass plates 1, 21 are then coupled and adhered to each other with interposition of the spacer 20 (step IV) and the nematic liquid crystal composition is filled therebe-tween to produce the reflection mode liquid crystal display cells ; of multi-digit configuration (step V). The liquid crystal cells , are sealed against the external environment.
After the formation of the liquid crystal display unit, various electronic components or elements, including the LSI im-plementation blocks 25, 25' are electrically bonded on the rear A
of the substrate 1 in the desired interconnection pattern (step VI). The rubber plate 45 for the keyboard unit 4 is then mounted on the upper surface B of the substrate 1 (step VII) and the ~ -. . .'' ' .

-- 1 1 -- ~"
.' - .

~ , .. . . - . . , . - - .

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103896~ -power supply circuit board 39 is secured adjacent the side of the substrate (step VIII).
For the purpose of housing the units thus formed on the same substrate 1, a set of the push buttons 50 are set on the housing upper portion 6, and the substrate 1 additionally carry-ing the power circuit and the battery cell 11 is enclosed in the housing upper and lower portions 6, 7. At this time, the indivi-dual push buttons are secured in a manner to correspond in posi-tion to the respective key contact electrode pairs.
As discussed above, the present electronic calculators may be.fabricated within a very shortened period of time, as com-pared to that required for conventional calculators, since the components or elements necessary for operation of the present .
electronic calculators are simultaneously formed on the same sub- - -strate and further because of the methods as used for fabrication of semiconductor elements.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An electronic calculator comprising a first functional unit for introducing into the calculator input signals associated with desired calculations, a second functional unit for performing the desired calculations in response to the introduced input signals, a third functional unit for displaying the results of the calculations, and a common substrate on which the third functional units and at least part of the first functional unit are directly formed and on which the second functional unit is directly mounted.

2. An electronic calculator as claimed in claim 1 wherein the substrate is a dielectric substrate having two major surfaces, the third functional unit comprises a multi-digit display unit directly formed on one of the major surfaces of the dielectric substrate, the second functional unit comprises a semiconductor circuit unit including at least one computation circuit, the semiconductor circuit unit being directly mounted on said one of the major surfaces of the dielectric substrate, and the first functional unit comprises a keyboard unit including stationary contacts directly formed on the other of the two major surfaces of the dielectric substrate.

3. An electronic calculator comprising a dielectric substrate, a display unit directly formed on the dielectric sub-strate, a semiconductor circuit unit including at least one com-putation function circuit, the semiconductor circuit unit being directly mounted on the dielectric substrate, and a keyboard unit including stationary contacts directly formed on the dielectric substrate.

4. An electronic calculator as claimed in claim 3 wherein the display unit comprises at least one liquid crystal display cell.

5. An electronic calculator as claimed in claim 4 wherein the or each liquid crystal display cell comprises a pair of electrodes, a liquid crystal composition filled between the electrodes, and a pair of electrode supporting plates one of which is constituted by the dielectric substrate.

6. An electronic calculator comprising a multi-digit liquid crystal display unit having a plurality of individual digit cells each including a pair of electrodes and a liquid crystal composition filled between the electrodes, the display unit additionally including a pair of dielectric plates for sup-porting in common all the ones of the electrode pairs for the individual digit cells and in common all the others of the electrode pairs for the individual digit cells, respectively, one of the dielectric plates having an extension; a semiconductor circuit unit including at least one integrated computation circuit block directly mounted on the extension of the dielectric plate, and a keyboard unit including a combination of a movable contact made of elastic material and a stationary contact of conductive material for each of a plurality of key switches, the individual stationary contacts being directly formed on the extension of the dielectric plate.

7. An electronic calculator as claimed in claim 6 wherein the keyboard unit comprises a spring plate formed with spring action areas for all of the key switches, each of the spring action areas being of spiral configuration with a pair of pivot axes.

8. An electronic calculator as claimed in claim 7 wherein the spring plate is made of an electrically conductive material and is connected to a reference voltage point.

9. An electronic calculator comprising:
a pair of substantially planar dielectric substrates constructed and arranged to define a cavity therebetween, one of said substrates being larger than the other in the provision of an extension of said one substrate beyond said cavity;
a liquid crystal display unit, a liquid crystal com-position being contained in said cavity, said liquid crystal display unit including electrode means formed on said dielectric substrates;
semiconductor circuit means including at least a computation function circuit having an input and an output, said semiconductor circuit means being directly mounted on said exten-sion of said one substrate, said computation function circuit output being coupled to said electrode means of said display unit, and keyboard switch means for feeding data into said cal-culator having stationary switch contacts directly formed on said extension of said one substrate, said stationary switch contacts being electrically coupled to the input of said computation function circuit.

10. An electronic calculator comprising a single con-tinuous substrate; an integrated circuit unit directly mounted on said substrate, said integrated circuit unit containing at least a computation circuit; a keyboard unit including a plurality of keys, each key comprising a fixed contact electrode directly deposited on the substrate and a movable member operatively associated with said electrode, said unit serving for entering into said calculator digit and function specifying information for calculations to be performed by said computation circuit;
a display unit having a plurality of display elements, each dis-play element comprising first and second electrodes at least one of which is directly deposited on the substrate; a first connection directly deposited on said substrate and disposed between said keyboard unit and said integrated circuit unit for transmission of said information from said keyboard unit to said integrated circuit unit; and a second connection directly deposited on said substrate and disposed between said integrated circuit unit and said display unit for transmission of computation results derived from said integrated circuit unit to said display unit; said substrate providing a structural support for all of said units and connections.

11. A method of making an electronic calculator, compris-ing the steps of preparing a dielectric substrate, forming a liquid crystal display unit directly on the dielectric substrate, mounting a semiconductor circuit unit including at least a computation circuit directly on the dielectric substrate, and forming at least part of a keyboard unit directly on the dielectric substrate.

12. A method as claimed in claim 11, including the steps of preparing a further dielectric substrate, depositing electrodes on each of the dielectric substrates, depositing simultaneously thick-layer interconnections and a predetermined number of stationary contacts for the keyboard unit on major surfaces of the one of the dielectric substrates, adhering the dielectric substrates carrying the electrodes to each other to form a cavity between the electrodes on the dielectric sub-strates, filling the cavity with a liquid crystal composition, mounting a semiconductor circuit unit containing at least one computation circuit on the one of the dielectric substrates, installing a rubber plate having the predetermined number of movable contacts above the dielectric substrate formed with the stationary contacts with the movable contacts registering with the stationary contacts, and housing the dielectric substrate directly carrying the liquid crystal display unit, the semi-conductor circuit unit and a portion of the keyboard unit in a casing.

13. A method as claimed in claim 12 wherein thick layer printing is applied by utilization of conductive paste in depositing the interconnections.