GB2201295A

GB2201295A - Planar display construction

Info

Publication number: GB2201295A
Application number: GB08803651A
Authority: GB
Inventors: Antti Piippo; Karl-Henrik Sallmen
Original assignee: Lohja Oy AB
Current assignee: Lohja Oy AB
Priority date: 1987-02-23
Filing date: 1988-02-17
Publication date: 1988-08-24
Anticipated expiration: 2008-02-17
Also published as: FI870775A0; FI80821C; DE3805598A1; FR2611294A1; GB2201295B; FR2611294B1; GB8803651D0; JPH0712107B2; FI870775A; FI80821B; JPS63233595A

Description

1 1 1; 2 22 0 12 9 PLANAR DISPLAY CONSTRUCTION The present invention

relates to a planar display construction, in particular an electroluminescent display construction, in accordance with the preamble of claim 1.

A typical display construction of the prior art conventionally comprises a printed circuit board with driver IC's and a planar display panel appropriately spaced from the PCB. The display panel is attached to the PCB by a mounting fixture construction between the board and the panel. Appropriate wiring between the display panel and the board is provided by means of jumper wiring.

FI patent publication 71860 describes a display construction of the aforementioned type based on the use of doublesided, resilient selfadhesive tape to provide attachment of the PCB to the panel.

Figure 1 diagrammatically illustrates a display construction conventionally applied in the art. According to the figure, a PCB (1) is attached to a display panel (3) with a copper finger strip (15) preplated with a layer of Sn60/Pb40 solder alloy and having its number of conductors equal to the number of contacts on the display panel (3), or as well, to the number of contacts on the PCB (1). In this case, integrated circuits (7) are located on the PCB (1). A hatched area (A) indicates the area allocated for the functional electronic components on the PCB (1). Thence, because the IC's (7) require a considerable proportion of the available area, the remaining area (A) is relatively small.

\1 2 i Further disadvantages of the prior art technology described above are: complicated mounting unreliable bonding delicate handling diffi.cult automation of production.

The aim of the present invention is to overcome the disadvantages Of the prior art technology and achieve a totally new kind of display construction. The invention is based on placement of the IC's outside the PCB so as to make them easily applicable circuit components, which are connected to the PCB on one side and to the display panel on the other side through their appropriate leads. More specifically, the display construction in accordance with the invention is characterized by what is stated in the characterizing part of claim 1.

In a preferred embodiment of the invention, the IC's are attached by their leads onto a film carrier tape to form TAB components in accordance with the TAB (Tape Automated Bonding) method.

The invention provides outstanding benefits, including: easy replacement of IC1s, - simplified PCB layout and reduced PCB area, while still offering an increase in the area A reserved for functional circuit components (see Fig. 2), reduction of bonding steps by two (due to the avoidance of IC mounting on the PCB), - easier automation of TAB component placement on the PCB and simplified adaptation to mass production by virtue of wider solder pad areas on the PCB in comparison to TAB component lead widths, easier implementation of elastic bonding required by the thermal excursions imposed on the bonds, and higher overall reliability of the bonding.

1 1 1 1 111 3 4 1 The invention is next examined in detail with help of the following exemplifying embodiment illustrated in the attached Figures 2... 6.

Figure 2 shows an electroluminescent (EL) display in accordance with the invention in a diagrammatically outlined view from the PCB side.

Figure 3 shows a detail of the construction illustrated in Fig. 2 in an enlarged ide view.

Figure 4 shows half of a TAB component illustrated in Fig. 2 in a partly cross-sectioned top view from the PCB side.

Figure 5 shows the connections of the TAB component illustrated in Fig 4 to the PCB.

Figure 6 shows the connections of the TAB component illustrated in Fig 4 to the display panel.

In the illustrated embodiment, an EL display panel glass plate 3 and a printed circuit board (PCB) 1 are attached to each other by means of a double-sided adhesive foam sheet 5 and an encapsulation glass plate 6 (Fig. 3).

fl Q A TAB component 7, 10 is designed to allow leads 9 of an IC package 7 to be directly bondable to contact pads H (Fig. 4) on the rear side of the EL display panel glass plate 3. Similarly, leads 8 of the IC package 7 are directly bonded to contact pads G on the printed circuit board 1. Thus, the number of leads (12 pcs.) of the TAB component 7, 10 connected to the printed circuit board 1 is appreciably smaller than the number of leads (64 pcs.) connected to the EL display panel glass plate 3. Consequently, the invention is advantageously-implemented with help of the TAB component 7, 10 which incorporates an integrated circuit (IC) 7.

Z 4 The integrated circuit 7 located in the center of the TAB component 7, 10 (Fig. 4) has a total number of 2 x 36 leads exiting the IC, with a set of 2 x 32 leads (leads 9) as the signal conductors proper and a set of 2 x 4 leads (leads 16, 17) serving as ground leads. Contact pads E of the exiting leads 9 have a pitch of 62 x 0.762 mm + 2 x 0.381 mm which is equal to the pitch of contact pads on the EL display panel glass plate 3. In turn, rectangular contact pads E of the exiting leads 9 with a pad area of 0.406 x 2.000 mm2 are compatible in size with the solder pads of the EL display panel 3 which are preplated with a Sn60/Pb4O solder alloy.

The number of conductors entering the integrated circuit 7 is 2 x 4 leads (leads 8), which leads are appropriately bonded. In turn, leads 15 (2 x 2 leads) are used as ground leads. Contact pads C and D of the leads 8 and 15 are again rectangular with an area of 0.5 x 2.0 mm2 (C) and 1.0 x 2.0 mm2 (D), respectively. Leads 8 and 15 in Fig. 4 are driven by the following drive signals (from left to right):

- Vs c (GND) - Power OK - DATA OUT - POL - HVcc - Vss (GND).

Drive signals connected to the leads of the other half (not shown) of the symmetrical TAB component 6 are correspondingly (from right to left):

- Vccl (12 V) - LE - DATA IN - BL - HVcc Vss (GND).

-1b, o,z 1 i Y 01 119 41 The TAB component 7, 10 is entirely supported by a Kapton film carrier tape 10, 11 which is used for placement of the component to a desired position. The material of the Kapton film is polyimide plastic with an average thickness of 150 um. The leads of the TAB component 7, 10'are 35 um thick copper foil, plated with a 0.5 um thick layer of Sn60/Pb40 solder alloy. The leads 8 are 0.5 mm. wide, leads 15 are 1.0 mm. wide, and leads 9 are 0.406 mm wide. The smallest width of leads 8 and 9 entering the IC 7 in a tapering manner is 0.0965 mm.

The TAB component mounting technology applied in the invention is based on.the conventional film carrier tape approach, in which a film carrier tape is produced in the first stage. This phase involves the perforation of sprocket holes 16 to the tape edge and punching of perforations 12. 13, and 14, which ease the detachment of the TAB component 7, 10 from the carrier tape. The second stage involves the lamination of the carrier film with a copper foil and etching of conductor pattern for the leads 8, 9, 15, 16, and 17 of the TAB component. In the third stage the conductors are plated with tin/lead alloy and punched. The next phase is the ILB (Inner Lead Bonding) operation, which bonds the integrated circuit to the TAB component leads. The fifth stage is the encapsulation of the IC 7, and the sixth stage, or the OLB (Outer Lead Bonding) operation includes the placement and bonding of the TAB component 7, 10 with its encapsulated IC 7 to connect the EL display panel glass plate 3 to the PCB 1.

For bonding, the leads 8 and 15 of the TAB component 7, 10 are appropriately aligned over the contact pads G (Fig. 5) of the PCB 1 yet avoiding the coincidence of the edges of the carrier tape 10 and the PCB 1. The pitch of the rectangular contact pads G on the PCB 1 is 2.0 mm, and the pad area is 2.0 mm2. This allows for a wide margin in the placement of the bonding pads C of the leads 8 over the board contact pads G.

1 1 6 The pitch of leads 9 of the TAB component 7, 10 is equal to the pitch of preplated contact pads H on the EL display panel glass plate 3 (Fig. 6). The area of contact pads H of the EL display panel glass plate 3 is larger than the area of the contact pads E of the leads 9, having a width of 0.5.mm"and a length of approx. 3.0 mm. The length of contact pads of leads 9 is 2. 0 mm. The black border line shown in Fig. 6 depicts a silicone strip 18 necessary in the production of the EL display panel 3.

When the TAB component 7, 10 is detached from the carrier film tape along its oblong perforations 12... 14 (Fig. 4), its shape is essentially that of a trapezoid with the entering leads 8 protruding from the shorter and the exiting leads 9 from the longer of the parallel sides. This shape of the TAB components 7, 10 makes possible an easy placement of adjacent components in accordance with the illustration of Fig. 2.

Without departing from the scope of the invention, constructions different from the exemplifying embodiment described in the foregoing are conceivable. Thus, in addition to the illustrated application of contacting an EL display panel glass plate to a printed circuit board, the TAB component construction with an integral IC can be utilized in general for any application of connecting a component to a PCB. Further, several IC's can be combined into a single TAB component.

i c Z, 7 T, t f 11

Claims

1. A planar display construction, such as an electra luminescent display, including integral integrated circuits, comprising a printed circuit board having an edge provided with a first set of contact pads, a display panel which is arranged substantially parallel to and spaced from the printed circuit board and which has an edge provided with a second set of contact pads, a mounting means between the printed circuit board and the display panel for physically attaching the printed circuit board and the display panel, and a contact assembly with leads for electrically connecting the first and second sets of contact pads, characterized in that the contact assembly comprises at least one of the integrated circuits, entering leads which connect the integrated circuit to the first set of contact pads, and exiting leads which connect the integrated circuit to the second set of contact pads, wherein the number of the entering leads is equal to the X 8 number of contact pads in the first set and is substantially smaller than the number of the exiting leads, which is equal to the number of contact pads in the second set.

2. A display construction according to claim 1, in which - the integrated circuit, the entering leads, and the exiting leads of the contact assembly are attached to a thin film foil to form a single TAB component in accordance with the TAB (Tape Automatic Bonding) method.

3. A display construction according to claim 2, in which the TAB component is formed generally in the shape of a trapezoid, with the entering leads protruding from the shorter of the parallel sides and the exiting leads protruding from the longer of the parallel sides.

4. A display construction according to any one of the preceding claims, in which the contact assembly is one of a number of s imilar assemblies similarly conne cted between the printed circuit board and the display panel at positions therearoUnd.

5. A display construction according to any one of the z 9 O preceding claims, in which the display panel is made of glass.

1

6. A display construction. according to claim 1, substantially as described with reference to Figures 2 to 6 of the accompanying drawings.

(0104W f' i Published 1988 at The Patent Office, State House, 66171 Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Offtw.