Display panel assembly having a plurality of film carrier tapes on each of which a semiconductor divice is mounted

A display panel assembly has a display panel, a printed circuit board, a plurality of semiconductor devices, and a plurality of film carrier tapes. The display panel has a plurality of electrodes. The printed circuit board is mounted on the display panel. The semiconductor devices are disposed between the electrodes of the display panel and the printed circuit board. Each film carrier tape has an opening and first and second lead group which extend from the tape in two opposite directions. Each lead group has a plurality of leads. One end of each lead group projects from the tape, and other end of each lead group projects into the opening. Each semiconductor device is mounted on a tape and is pressed to contact the electrodes. The one end of the second lead group is connected to the printed circuit board.

BACKGROUND OF THE INVENTION 
This invention relates to a display device using liquid crystal, 
electroluminescence, or the like, and more particularly to a thin type 
display device on which a driving circuit for the liquid crystal, the 
composition exhibiting electroluminescence or the like is mounted. 
Recently, display panels using liquid crystal or electroluminescence are 
being developed and commercialized. These display panels are so thin that 
they are easily assembled into a thin type appliance. However it is 
necessary to connect a semiconductor device for driving the display panel 
to a group of electrodes extending from the end of display panel. The 
number of these electrodes ranged, depending on the size of display panel, 
from hundreds to thousands. Such a semiconductor device for driving was 
assembled in a package such as a flat pack, and mounted on a printed 
circuit board nearly the same size as that of the display panel. The leads 
of this package are soldered to the wiring pattern formed on said printed 
circuit board. This wiring pattern is connected to the electrode disposed 
on the opposite side of the printed circuit board by way of a through-hole 
provided in the printed circuit board. The electrodes of the printed 
circuit board and those of the display panel are formed at equal 
intervals. Furthermore, the electrodes of the printed circuit board and 
those of the display panel are connected by elastic connectors alternately 
laminating conductive regions and insulating regions. 
In such a method of construction, the package of the semiconductor device 
must increase in size as the number of leads is increased, making it hard 
to mount on the printed circuit board, and as a result, the entire display 
panel must be made larger. In addition, the electrodes of the printed 
circuit board must be formed one by one corresponding to those of the 
display panel. Actually, since electrodes must be formed at pitches of 
hundreds of micrometers (.mu.m) on a side of tens of centimeters, and the 
electrode interval on the printed circuit board is subject to cumulative 
errors due to thermal expansion and other factors, a perfect connection 
could not be obtained, which led to connection troubles. Furthermore, 
there were many points of connection. For example, there were at least 
four points of connection, that is, wire bonding in the package of the 
semiconductor device, soldering of the package, and two connections of 
elastic connectors, which was a major cause in lowering the reliability. 
In such a conventional construction, the structure of the display panel was 
extremely large, or the number of connections was too many, which causes a 
lower reliability of the connection. This occurs because there were too 
many constituent parts in the structure, and the true structure of the 
display panel could not be realized. 
SUMMARY OF THE INVENTION 
It is hence a primary object of this invention to present a display device 
which has a relatively small number of constituent parts and a relatively 
small number of connections. 
This and other objects of the invention are accomplished by a display 
device which comprises a display panel having plural electrodes connected 
to an external circuit, an external printed circuit board provided to the 
display panel, a semiconductor device for driving the display panel 
disposed between the external circuit and the display panel, a support 
member for mounting the semiconductor device, and first and second lead 
groups composed of plural leads provided on the support member and 
extending in at least two directions, wherein the first lead group is 
connected to the electrodes on the display panel and the second lead group 
is connected to the external printed circuit board. 
In the preferred embodiments, the first lead group is fixed to the 
electrodes on the display panel by soldering or adhering. The interval of 
the plural electrodes on the display panel is equal to that of the leads 
in the first lead group. The support member is a carrier tape used in a 
film carrier system or a tape automated bonding system. This support 
member has an opening, in which one-side ends of the leads of the first 
and second lead groups project and these lead groups are fixed to the 
support member. The electrodes of said semiconductor device are connected 
to the projected ends of these leads in the opening. The first lead group 
is press-fitted to the electrodes on the display panel by means of an 
elastic body, thereby electrically connecting the electrodes on the 
display panel and the first lead group. This elastic body is shaped like a 
bar. This bar elastic body is either a Viton rod or a silicon rod. The 
electric body is supported at the end of display panel by a C-shaped 
frame. Since the electric body is shaped like a bar, a groove to receive 
this bar elastic body is provided in the frame. Furthermore, the frame is 
composed of a first structure having the groove to receive the elastic 
body and a second structure which is engaged with the principal plane of 
the display panel, and integrally coupling these two structures, the frame 
presses down the elastic body and is supported at the end of the display 
panel. These two structures are integrally coupled by screws. A cover is 
provided at the back of the display panel, and said printed circuit board 
and a support member mounting said semiconductor device are attached to 
the cover. Grooves for disposition of the support member are provided at 
the side of the cover. 
This invention provides various advantages, among which are as follows: 
(1) Since the semiconductor device for driving is mounted by employing film 
carrier method or a tape automated bonding method and is disposed in the 
specified region of the display panel and the leads extended from the 
electrodes of said semiconductor device are joined to the electrodes on 
the display panel directly, there are only two points of connection, that 
is, at the electrode of the semiconductor device for driving and at the 
electrode of display panel, and the reliability associated with the 
connections is extremely high. Moreover, since the semiconductor device is 
mounted by the film carrier method, a thin and small packaged structure is 
realized. 
(2) Since the leads extending from the semiconductor device for driving are 
directly connected to the electrodes on the display panel, the number of 
constituent parts is extremely decreased, while the number of 
manufacturing processes are reduced, so that the cost of the packaged 
structure may be lowered. 
(3) At the junction of the electrodes of the display panel and the leads 
from the semiconductor device, since the positioning may be achieved over 
a short distances at every film carrier of each semiconductor device, 
conventional problems associated with a deviation in the interval of the 
electrodes on the printed circuit board and with dislocation of the 
electrodes on display panel are avoided. 
(4) In case, incidentally, the semiconductor device is broken, it may be 
easily replaced only by removing the soldering of the lead to the film 
carrier. 
(5) Positioning of the display panel electrodes and leads may be easily 
attained because there is no intervening object. 
While the novel features of the invention are set forth particularly in the 
appended claims, the invention, both as to organization and content, will 
be better understood and appreciated, along with other objects and 
features thereof, from the following detailed description taken in 
conjunction with the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The display device of a first embodiment of this invention is described 
below in reference to FIG. 1, wherein plural electrodes 14 are disposed 
parallel at the end of the back side of a flat display panel 10 comprised 
of liquid crystal, or exhibiting electroluminescence, or the like (the 
front display surface is 12). The back side of the display panel 10 is 
masked with a cover 16, and a printed circuit board 18 is attached to this 
cover 16. In case of an electroluminescence display panel, wet absorbing 
agent is accommodated in cover 16. 
A semiconductor device 20 for driving the display panel 10 is mounted on a 
film tape 21, which is made of polyimid, using a film carrier system or a 
tape automated bonding system and is disposed in a specified region at the 
back side of the display panel 10. The electrodes 22 of semiconductor 
device 20 and leads 24 and 26 provided on the film tape 21 are joined 
together, and the interval between the electrodes 14 on display panel 10 
and the interval between leads 24, to be connected, is the same so that 
the leads 24 contact the electrodes 14 on the display panel 10. An 
insulating layer (e.g., polyimid tape) 23 is disposed on the backside of 
leads 24, 26. Semiconductor device 20 is molded in synthetic resin 27. The 
other lead 26 on the film tape 21 is joined to the wiring board 18 
disposed in a specified region on the back side of the display panel 10. 
That is, the lead 26 extending from the semiconductor device 20 is an 
input terminal for supplying an input signal and power for driving the 
semiconductor device 20, while the lead 24 is an output terminal for 
delivering signals to drive the display panel 10. In the display device, a 
plurality of semiconductor devices 20 mounted on said film tape 21 are 
disposed in at least one row. 
Further describing the semiconductor device for driving mounted by 
employing the film carrier method as illustrated in FIG. 2, the 
semiconductor device 20 is joined with the ends 25 of leads 24, 26 
projected into an opening 28 of the film tape 21. An Au protrusion or 
so-called bump having a thickness of 10 to 30 .mu.m is formed on the 
electrode 22 of said semiconductor device 20 by way of a multiple metal 
layer such as Ti-Pd-Au and Cr-Cu-Au. A copper foil is adhered to the film 
tape 21, and this copper foil is etched, and leads 24, 26 are formed, and 
these leads are plated with Sn, and said lead ends 25 and the bump are 
joined together by an Au-Sn alloy. The semiconductor device 20 may be 
disposed on the underside of leads 24, 26. Incidentally, in this 
embodiment, the thickness of tape 21 is 0.125 mm and the thickness of the 
semiconductor device 20 is 0.3 mm. 
The lead 26 which is the input terminal to the semiconductor device 20 and 
the lead 24 which is the output terminal project from the semiconductor 
device in mutually different directions (that is, in two directions), and 
the leads 24 are spaced at the same interval as are the electrode interval 
on the display panel. In the construction shown in FIG. 2, a plurality of 
leads formed on a long film 30 are cut to extend in a specified direction. 
Or, one lead 24 contacting the electrode of the display panel in FIG. 2 
does not have any film carrier left over at its end. Rather, the film 
carrier may be left over so as to fix the lead end to the end of said lead 
24. 
The electrode 14 of display panel 10 and lead 24 are joined either by 
soldering or by means of adhesive or the like. 
FIG. 3 shows another embodiment of the method of joining the electrode 14 
of display panel 10 and lead 24, in which the electrode 14 of display 
panel 10 and lead 24 are positioned, and an elastic body 32 made of 
silicone or the like is placed on said lead 14 and is press-fitted by 
means of a C-shaped frame 34. 
A further embodiment of the display device of this invention is described 
in FIGS. 4 to 6, in which, for the sake of simplicity, the same 
constituent parts as in FIGS. 1 to 3 are identified with the same numbers 
and are not specifically explained herein. In the device shown in FIGS. 4 
to 6, a plurality of film carriers 21 having leads 24, 26 extending in two 
directions are disposed on an end oblique plane 36 of a cover 16 provided 
on the back side of the display panel 10. Two semiconductor devices 20 are 
mounted on one film carrier 21, and these semiconductor devices are 
mutually electrically connected by being wired along the circuit pattern 
on the film carrier 21. One of the leads, 26, is connected to a circuit 
pattern 38 formed on a printed circuit board 18, while another lead 24 has 
its bottom contacting an electrode group 14 on display panel 10 and its 
top contacting an elastic body 42 of a frame 30 and is press-fixed by a 
frame 44. The two frames 44, 46 are fastened by means of screw 46. 
As the display panel 10, an electroluminescent display panel having 256 
scanning electrodes at a pitch of 0.32 mm and 1024 external lead-out 
electrodes 14 for signal electrodes is used. The material comprising the 
electrodes 14 is either Cr or ITO. The material comprising cover 16 and 
frames 40, 44 is Al. A groove 47 is provided in the frame 40, and an 
elastic body 42 comprised of a Viton rod (2 mm.phi.) or silicone is 
inserted into this groove. 
The film carrier 21 is prepared by forming a copper foil pattern 37 on a 
polyimide film and plating with tin or Au. Bumps comprised of a Ti-Pd-Au 
composition are formed on the electrodes 22 of the semiconductor device 
20, and are connected with the leads of the film carrier 21 by means of an 
Au-Sn or Au-Au alloy 
Forty film carriers (8 pieces at a scanning side and 32 pieces at a signal 
side) are buried in the grooves 37 provided in the cover 16, and one end 
of lead 24 is mounted on the external lead-out electrode 14, and the end 
of lead 26 is connected to the printed circuit board 18 while the frames 
40 and 44 are secured by means of the screw 46 by press-fitting the lead 
group 24 and electrode group 14 by means of the elastic body 42 of the 
frame 40. 
When thus packaged, and when the electroluminescent display panel was 
driven with a driving voltage of 100 V and a maximum current of 80 mA, 
satisfactory driving was achieved. At this time, the connection resistance 
was not more than 1 ohm regardless of the electrode material, and it was 
not more than twice the intial value after 1000 hours of withstanding 
125.degree. C. and 80.degree. C. storage temperatures, 85% storage. 
In the embodiments, the film carrier tape 21 is fixed to the groove 37 
provided in the cover 16, but it may be also possible to fix the film 
carrier tape by forming a protrusion on the frame 40, making a hole to be 
matched with this protrusion in the film carrier 21, and putting the film 
carrier hole over this protrusion of the frame 40. Or, since the position 
at which the lead group 26 is connected on the printed circuit board 18 
can be predetermined, the lead group 24 and electrode group 14 on the 
display panel may be automatically positioned when connecting the lead 
group 26 to the printed circuit board 18 without providing a groove or 
protrusion to define the position of film carrier 21 on the cover 16 of 
the display panel as mentioned above. 
Moreover, in the embodiments, the frames 40, 44 are joined together by 
means of screw, but they may also be joined by fit-in type or by means of 
a fixing jig. Incidentally, the material comprising the frames 40, 44 and 
cover 16 are Al, but this is not required, and the material may also be 
Cu, SUS, Fe, ceramics, resins or the like. As the elastic body, in 
addition, silicone rubber and other elastic materials having a relatively 
good heat resistance may be used. Leads 24 are position-controlled by a 
part 21A of film tape 21. By use of this part 21A, deviation of leads 24 
in sideways direction is prevented. 
In such a construction, facilities for the treatment of electrodes of the 
display panel, heating jig and for soldering are not necessary. 
While specific embodiments of the invention have been illustrated and 
described herein, it is realized that modifications and changes will occur 
to those skilled in the art. It is therefore to be understood that the 
appended claims are intended to cover all modifications and changes as 
fall within the true spirit and scope of the invention.