Electronic table calculator using liquid crystal display

An electronic table calculator is provided having a liquid crystal display and an integrated circuit element defining one or more of the display-driving circuitry or the calculating circuitry thereof. The liquid crystal display is defined by a pair of spaced plates having liquid crystal material therebetween contained by a spacer. At least one of the plates projects beyond the spacer and has formed on the same inner surface thereof, electrode portions within the spacer forming a part of the liquid crystal display and electrode portions outside of the spacer to which the integrated circuit element is coupled by face-down bonding.

BACKGROUND OF THE INVENTION 
This invention relates generally to compact electronic table calculators 
characterized by low power consumption, although the principles of the 
invention herein may be applied to other electronic devices incorporating 
liquid crystal displays and integrated circuit chips. The electronic table 
or pocket calculator has been widely distributed in recent years to 
individual consumers. For this purpose, it has proved necessary to provide 
an electronic table calculator which is portable and which can be driven 
by battery over a long period of time. For the mass consumer market, it is 
necessary that the electronic table calculator be miniaturized, lightened 
and reduced in cost. 
An electronic table calculator generally consists of at least a calculating 
circuit, a display-driving circuit operatively coupled to the calculating 
circuit for driving thereby, a display element for providing a visual 
digital display of the output of the calculating circuit and operatively 
coupled to the display-driving circuit for driving thereby, a keyboard or 
other input arrangement operatively coupled to the calculating circuit, a 
power source such as a battery, and a case for supporting and protecting 
the other elements. 
It has been found that by using a complementary coupled metal oxide 
semiconductor (C-MOS) device for the circuit elements and a liquid 
crystal-type display device, a device having minimum power consumption is 
produced thereby providing a calculator providing maximum battery life. 
Further a unique arrangement for coupling the integrated circuit chip to 
the liquid crystal display device has been provided in furtherance of the 
goals of miniaturization, reduction in weight and reduction of cost. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, an electronic device 
is provided having liquid crystal display means and an integrated circuit 
means, wherein said liquid crystal display means is formed from a pair of 
spaced plates, liquid crystal material, a spacer surrounding said liquid 
crysyal material and first and second electrode means each respectively 
positioned on one of the spaced facing surfaces of each of said plates 
within at least the region defined by said spacer, at least the one of 
said plates bearing said second electrode means extending laterally beyond 
said spacer. Said one plate has third electrode means formed thereon on 
the same surface as said second electrode means. Said integrated circuit 
means is formed with a plurality of contacts on a surface thereof, said 
integrated circuit means being electrically connected to said third 
electrode means by face-down bonding of said contacts thereto. Said 
integrated circuit may be C-MOS. Said face-down bonding may be achieved 
through the use of solder. The electronic device may be a portable 
electronic calculator. 
Accordingly, an object of the invention is to provide an electronic device 
having a liquid crystal display and an integrated circuit chip wherein the 
integrated circuit chip is mounted on an inner face of a plate of the 
liquid crystal display by means of face-down bonding. 
A further object of the invention is to provide an electronic pocket 
calculator wherein miniaturization and cost reduction is enhanced through 
the avoidance of lead contact between the liquid crystal display and the 
integrated circuit elements thereof through the use of face-down bonding. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification and drawings. 
The invention accordingly comprises the features of construction, 
combinations of elements, and arrangement of parts which will be 
exemplified in the constructions hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DESCRPTION OF THE PREFERRED EMBODIMENTS 
Various kinds of metal oxide semiconductors (MOS) and large scale 
integrated circuits (LSI) may be used at the present time as a calculating 
circuit and/or as a display-driving circuit for an electronic calculator. 
The following table illustrates the power consumption and the required 
supply voltage of MOS and LSI for various kinds of electronic calculators: 
______________________________________ 
supply 
voltage (V) 
power consumption (mW) 
______________________________________ 
Al gate E/E MOS 
16 or 8 150 
Si gate E/D MOS 
6 25 
COS - MOS 3.about.6 0.3.about.2 
______________________________________ 
The foregoing table illustrates that a circuit using complementary 
symmetry-metal oxide semiconductor integrated circuits (COS-MOS-IC) is 
best adapted for electronic calculators in view of the voltage required in 
the voltage supply (usually a battery) and the minimum power consumption. 
Display devices for electronic calculators may likewise take a number of 
forms such as digitron, light emitting diodes (LED) and liquid crystal 
displays. The following table illustrates the driving voltage and power 
consumption of such forms of display devices: 
______________________________________ 
driving 
voltage (V) 
power consumption (mW) 
______________________________________ 
digitron 24 100 
light-emitting diode 
3.about.5 80 
liquid crystal display 
3 0.01 
(field-effect type) 
______________________________________ 
From the foregoing, it is apparent that a display based on liquid crystals 
is the most advantageous form of display in view of the low voltage 
required and the low power consumption. 
Referring now to FIG. 1, one method for combining a liquid crystal display 
with a C-MOS-IC chip is depicted. The liquid crystal display depicted 
comprises an upper plate 1 and a lower plate 2 both formed of a 
transparent material such as glass and maintained in spaced relation by a 
spacer S which also serves to retain liquid crystal material 5 between the 
plates. As is illustrated in FIG. 1, plate 2 extends laterally beyond the 
spacer S on at least one side thereof so as to define a support for other 
electronic circuitry related to the liquid crystal display. Mounted on the 
inner surfaces of plates 1 and 2 are first electrodes 3 and second 
electrodes 4 which, together, define the indicia such as numerals to be 
displayed. The selective application of voltages between selected of 
electrodes 3 and 4 orients the liquid crystals to render the region 
therebetween visually distinguishable from the surrounding regions of the 
liquid crystal. The first and second electrodes are positioned in a 
pattern to produce the desired indicia. The liquid crystal display device 
also includes upper polarizing plate 6 and lower polarizing plate 7 
mounted respectively on the outer surfaces of plates 1 and 2 and a 
reflector 8 mounted on the outer surface of lower polarizing plate 7 to 
complete the optical path. First and second electrodes 4 may be thin film 
films and, in any event, each segment of electrode 4 to be energized has a 
portion which extends intermediate spacer S and the surface of lower plate 
2 to a region outside of the region defined by spacer S to permit 
electrical connection to each of said segments. Electrical connecting 
means can be provided for electrically connecting each of the segments of 
first electrodes 3 to segments of second electrodes 4 provided for this 
purpose, which segments would likewise extend outside of spacer S to 
provide electrical connection to segments of first electrodes 3. Thick 
film third electrodes 9 are deposited in a pattern on the upper surface of 
lower plate 2, at least some of the segments of third electrodes 9 making 
electrical connection with the portions of the segments of second 
electrodes 4 extending outside of spacer S. A thick film insulator layer 
10 is disposed in a predetermined pattern on a portion of third electrodes 
9 and thick film fourth electrodes 91 are deposited on the surface of 
insulating film 10. Crossover interconnection between fourth electrodes 91 
and third electrodes 9 is provided in a conventional manner through the 
means of apertures in insulating film 10 and the provision of conductors 
in said apertures. 
A COS-MOS-IC chip 11 including circuitry for performing both calculating 
functions and display-driving functions is mounted on the upper surface of 
lower plate 2. Electrical connection between third electrodes 9 and the 
contacts of the chip 11 is by way of wire-bonding 12. A terminal portion 
14 for connection of the assembly to other circuitry, such as a keyboard 
or a source of electrical power is provided. Terminal 14 is coupled to one 
of the thick film third electrodes 9 by means of solder 13. 
FIG. 2 illustrates a structure similar to that of FIG. 1, like reference 
numerals being applied to like elements. However, in the embodiment of 
FIG. 2, the thick film fourth electrodes 91 define a pattern suitable for 
forming a keyboard contact. Above the fourth electrodes and positioned for 
making selective electrical contact with respective segments thereof are 
keys 151, 152, 153 and 154. This approach minimizes exterior soldering and 
leads to more effective production, miniaturization, reduction in weight 
and thinning of electronic calculators. 
In both FIGS. 1 and 2, a C-MOS-IC chip is bonded to thick film conductors 
by a wire-bonding technique, the thick-film conductors being provided on 
the liquid crystal base plate. However, it is desirable to form most of 
the circuitry of an electronic calculator in a single integrated circuit 
chip including the calculating circuitry, circuitry for generating the 
clock signal and the liquid crystal driver circuitry. This approach 
results in reduced cost and improved reliability but since the number of 
bonding pads or contacts on such a C-MOS-IC may be 36 or more, the number 
of process steps required for assembly increases where the wire-bonding 
method is utilized. Further, wire-bonding machines are fairly expensive 
and the production capability of a single machine is relatively small. 
Accordingly, mass production of electronic devices such as electronic 
calculators results in increased equipment cost which counteract the 
beneficial effects of using a single integrated circuit chip. By utilizing 
an improved face-down bonding method as the method of joining a C-MOS 
integrated circuit to a liquid crystal display cell, the foregoing 
difficulties are avoided. 
Referring to FIG. 3, the liquid crystal display cell structure is similar 
to that of FIGS. 1 and 2 and like reference numerals are applied to like 
elements. In this embodiment, thick film third electrodes 23 are applied 
to the inner surface of lower plate 2, at least portions of said third 
electrodes being in electrical connection with segments of second 
electrodes 4. As in the case of FIGS. 1 and 2, first electrodes 3 and 
second electrodes 4 may be formed of transparent conductive films such as 
tin oxide and indium oxide. If desired, third conductors 23 may be formed 
of a thin film and may be formed by evaporation, plating or the like. An 
LSI chip 24 consisting of a one-chip CPU including one or both of the 
liquid crystal driving circuitry and calculating circuitry is secured to 
the third conductors 23 by a face-down bonding technique. An insulating 
layer 26 is provided on third electrodes 26 formed of a dielectric thick 
film or a thin insulating film and a pattern of fourth electrodes 22 may 
be deposited on insulating film 26 as described above and interconnected 
with third electrodes 23 in the manner described above in connection with 
FIG. 2. A capacitor 29 and a resistor 30 are coupled to fourth electrodes 
22 and define a portion of the circuit for generating the clock pulse of 
the LSI chip or define a part of the circuit for automatic clearing of the 
calculating circuitry. Said resistor and capacitor are preferably secured 
to fourth conductors 22, which may be thick film or thin film electrodes, 
by means of resistance welding. If desired, the resistance and capacitor 
devices can be formed utilizing integrated circuit techniques directly on 
the electrode base plate 2 by means of thick or thin films. The assembly 
is provided with an external terminal 28 for connection to external parts 
such as a keyboard or a power source (battery), terminal 28 taking the 
form of a flexible print wiring base plate, an electric lead wire or the 
like. Said terminal is electrically connected to the third electrodes 23 
by means of solder or resistance welded portion 27. 
The LSI chip is bonded by face-down bonding through bonding portions 25 and 
251. Face-down bonding may be achieved by means of the following procedure 
where the pattern of third electrodes 23 is formed to provide terminal 
pads corresponding in orientation to the terminal pads or contacts of the 
LSI chip. First, thin films of gold, nickel, copper or the like are formed 
on the bonding pad portion of the LSI chip 24 by means of evaporation or 
in the form of solder. Corresponding thin films of similar materials are 
deposited on the bonding pad regions of third electrodes 23. Thereafter, 
the LSI chip 24 is thermobonded to the third electrodes 23 through the 
joining of the deposited thin films. FIG. 4 illustrates an LSI chip 32 
which has been solder plated in the region of contacts 31. 
Third electrodes 23, if in thick-film form, may be formed of silver or 
silver-palladium. If such materials are used, the efficacy of the 
soldering is further improved if a gold paste is utilized. Where the third 
electrodes are formed of a thin film, solders formed of nickel, copper, 
gold, iron or an alloy including them improve soldering. Reliability is 
further improved by applying solder-plating to the contact terminal 
portions of the segments of third electrodes 23. 
A second method of face-down bonding is by applying pressure on the LSI 
chip 24 to engage the chip against third conductors 23 after placing an 
annealed metal of indium, tin, lead or the like on the bonding pad or 
contact portions of the LSI chip 24 by way of vapor deposit, soldering or 
the like. As in the prior method, the bonding power is improved if the 
annealed metal of indium, tin or lead or the like is likewise deposited on 
the bonding portion of third electrodes 23. 
A third method is the application of gold or an alloy including gold in a 
somewhat thick layer to the bonding pad or contact portion of the LSI chip 
by vapor deposit, plating or the like. Bonding is achieved by applying 
pressure to the conductive wiring portion. In this case, as in the other 
cases, bonding is improved if the gold or an alloy including gold is 
applied to the bonding portion of the third electrodes. The bonding of the 
gold film to the contacts of the LSI 24 and to the conductive electrodes 
is enhanced if a layer of aluminum, chromium, nickel, copper or an alloy 
including them is applied before the gold is applied. 
A fourth method for achieving face-down bonding is by subjecting the 
bonding agent to calcination by heat after deposit on the bonding pad 
portion of the LSI chip 24 or on the bonding pad portion of the third 
electrodes. 
A fifth method of face-down mounting of an LSI chip is illustrated in FIG. 
5, where like reference numerals are applied to like elements. In this 
method, the LSI chip is bonded by supersonic waves or heat-pressure to an 
array of thin film electrodes 35 arranged to correspond to the contacts of 
the chip and supported on an insulating film 34 such as a film formed of a 
polyimide or like insulator. This first bonding is followed by bonding the 
other end of each electrode 35 to the third electrodes 36 disposed on the 
liquid crystal lower base plate 2 by means of solder or electric welding. 
The arrangement in accordance with the invention wherein a liquid crystal 
panel is utilized as a display for an electronic calculator, a C-MOS-LSI 
is utilized as an integrated circuit for performing the calculating 
function and/or the display driving function, and said integrated circuit 
chip is mounted on one of the base plates of the liquid crystal by 
face-down bonding, provides the following advantages: 
a. a display device and the calculating circuit portion can be united in 
compact and thin assembly. 
b. the number of bonding processes is reduced and bonding machinery is 
decreased through utilization of the face-down bonding technique. 
c. since the strength of the bond is greater where face-down techniques are 
utilized, reliability is further improved. 
While the embodiments depicted utilize a liquid crystal display cell of a 
particular configuration incorporating polarizens and a reflector, other 
liquid crystal display cell configurations can be used in accordance with 
the invention. Similarly, the arrangement in accordance with the invention 
can be utilized in connection with other electronic devices incorporating 
liquid crystal display cells and integrated circuit elements. 
It will thus be seen that the objects set forth above, and those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above constructions without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein 
described, and all statements of the scope of the invention which, as a 
matter of language, might be said to fall therebetween.