1. Field of the Invention
The invention relates to a system for providing conducting pads.
2. Description of the Prior Art
Due to the fast development of electronics, the requirements of displays used as interfaces between machines and human are becoming more and more strict. Because liquid crystal displays (LCD) have light weight, thinness, low energy requirements, no radiation, and other good qualities, they have become the main stream in the market and are widely used in notebooks, personal digital assistants (PDA), digital cameras, cellular phones, and other communication and information equipments. Furthermore, LCDs also tend to replace the traditional cathode ray tube (CRT) monitors and CRT TVs in recent years. On the other hand, organic-light-emitting-diode (OLED) displays also have drawn attention due to the research of organic materials and their advantages of being self-light-emitting, having a high resolution, and having wide viewing angles. As a result, LCD displays, OLED displays and other flat-panel displays have become indispensable for mobile information electronics and have become more popular in people's lives.
A conventional flat display, whether a LCD or an OLED display, contains a pixel array area and a periphery circuit area, wherein a plurality of conducting pads are formed in the periphery circuit area for electrically connecting to external circuits. Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of a top view of a flat display panel 10 according to the prior art, and FIG. 2 is a side view of the flat display panel 10 shown in FIG. 1. The flat display panel 10 is a LCD, comprising two glass substrates 12, 14, and a liquid crystal layer 16 between the glass substrates 12 and 14. As shown in FIG. 1, the upper glass substrate 12 has a smaller size than that of the lower glass substrate 14. Therefore, a portion of the glass substrate 14 is covered by the glass substrate 12 and which defined as a covered region 18, and another portion of the glass substrate 12 is an uncovered region, defined as a periphery circuit area 20. The covered area 18 includes a pixel array area (active area, AA) 11 and a control circuit area 13.
The periphery circuit area 20 has a plurality of periphery circuits and conducting pads 22 for electrically connecting to external circuits and sending signals through internal circuits in the flat display panel 10, such as DC-DC voltage lines or scan control signal lines. A conventional conducting pad structure is illustrated in FIG. 3, which is a cross-section view of the conducting pad 22 shown in FIG. 1. Conventionally, the conducting pad 22 is a multi-layer structure. As shown in FIG. 3, the conducting pad 22 in the periphery circuit area 20 comprises a first insulation layer 24, a first conductive layer 26, a second insulation layer 28, a second conductive layer 30, and a third conductive layer 32 in sequence on the glass substrate 14, wherein the third conductive layer 32 covers the surfaces of the second conductive layer 30, including the top surface and the side surfaces of the second conductive layer 30. In general, the second conductive layer 30 is formed with metal materials with lower impedance, and the third conductive layer 32 is formed with materials with higher impedance while the hardness of the materials of the third conductive layer 32 are harder than that of the materials of the second conductive layer 30.
Since the periphery circuit area 20 on the glass substrate 14 is not covered by the glass substrate 12, it is unavoidable to suffer stresses or forces during the fabrication process, assembling process, or transferring process. However, the material of the third metal layer 32 is usually so brittle that it is easily broken under such stresses or forces. Once the third metal layer 32 is broken by an external force, it may sequentially scratch and cave the second metal layer 30 formed with soft materials, and the third metal layer 32 under the external force may even shift the second metal layer 30 to cause the second metal layer 30 contact another element on the glass substrate 14, resulting in an element short. Also, when the external force scratches the third metal layer 32 and the second metal layer 30, a scratching trace may occur on the surface of the conducting pad 22 such that the flat display panel 10 becomes an inferior product under a visual test.
Accordingly, it is still an important issue for the manufacturer of displays to provide a conducting pad that has preferable structure to avoid traces, shifts or element shorts under external stresses or forces in the uncovered periphery circuit area.