Display device and system for inspecting bonding resistance and inspecting method thereof

A system for inspecting bonding resistance of a display device includes a display panel, at least one circuit board, at least one driving chip and a testing board. The display panel includes at least one testing conductive line and connecting conductive lines. The circuit board is connected with the testing conductive line and the connecting conductive lines. The driving chip includes at least one testing pad and connecting pads, respectively electrically connected to the testing conductive line and the connecting conductive lines; at least one comparator connected to the testing pad; and at least one logic circuit connected to the comparator. The testing board is connected to the circuit board and provides a test signal to the testing pad through the circuit board and the testing conductive line. The test signal is compared with a reference signal in the comparator, and the logic circuit determines a comparing result.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 99136994, filed on Oct. 28, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

1. Field of the Disclosure

The present invention relates to a display device, and more particularly to a system for inspecting bonding resistance and an inspecting method.

2. Description of Related Art

Generally speaking, asides from a display panel, a display device also includes a circuit board and a driving chip for driving an image display of the display panel. After the fabrication of a display device, a series of inspection procedures is performed to ensure that the display quality of the display device conforms to standards.

Currently, the method of inspecting the bonding resistance between the display panel and the circuit board, and the bonding resistance between the display panel and driving chip is performed with an automated optical inspection apparatus. The automated optical inspection apparatus, however, can only determine whether the pressed conductive particle number and the relative position between the display panel and the circuit board and between the display panel and driving chip are normal. Alternatively speaking, the automated optical inspection apparatus is unable to inspect the actual bonding resistance between the display panel and the circuit board, and between the display panel and the driving chip.

Another approach to inspect the bonding resistance is to additionally provide a voltage to two neighboring conductive lines on the display panel and to determine whether a short circuit occurs in order to ensure whether there is any bonding abnormality. With this inspection approach, any bonding defect would directly reflect as a white spot on the display panel (for example, with flickering or excessive current consumption, etc.). However, not all bonding defects can be determined with this inspection method. Hence, defective products are often not identified. Moreover this inspection method is more complicated and time consuming.

SUMMARY OF THE DISCLOSURE

The following disclosure is directed to a display device and a system for inspecting bonding resistance and a method for inspecting bonding resistance.

An exemplary embodiment of the disclosure provides a system for inspecting bonding resistance of a display device, and the system includes a display panel, at least one circuit board, at least one driving chip and a testing board. The display panel includes at least one testing conductive line and a plurality of connecting conductive lines. The circuit board and the testing conductive line of the display panel are electrically connected to the connecting conductive lines. The driving chip includes a plurality of connecting contact points and at least one testing contact point that are respectively electrically connected the connecting conductive lines of the display panel and the testing conductive line; at least one comparator electrically connected with the testing contact point; and at least one logic circuit electrically connected with the comparator. The testing board and the circuit board are electrically connected. More specifically, the testing board provides a test signal, and after the test signal is transmitted to the test contact of the driving chip through the circuit board and the testing conductive line, the test signal in the comparator is compared with a reference signal, and the logic circuit determines the comparison result of the comparator.

An exemplary embodiment of the disclosure provides a method for inspecting a display device, and the method includes providing a display device which includes a display panel, at least one circuit board and at least one driving chip that are electrically connected with the display panel, and a testing board that is electrically connected with the circuit board. The above-mentioned display panel includes at least one testing conductive line and a plurality of connecting conductive lines. Thereafter, a bonding resistance inspection procedure is performed, and the inspection procedure includes providing a test signal by the testing board, wherein the test signal is transmitted to the driving chip through the circuit board and the testing conductive line. The test signal is compared with a reference signal. If the test signal is greater than the reference signal, a first signal is output through one of the connecting conductive lines. If the test signal is smaller than the reference signal, a second signal is output through one of the connecting conductive lines.

An exemplary embodiment of the disclosure further provides a display device that includes a display panel, at least one circuit board and at least one driving chip. The display panel includes at least one testing conductive line and a plurality of connection conductive lines. The circuit board is electrically connected with the test conductive line of the display panel and the connecting conductive lines. The driving chip includes a plurality of connecting contact points and at least one testing contact point respectively electrically connected with connecting conductive lines of the display panel and the testing conductive line; at least one comparator electrically connected with the testing contact point; and at least one logic circuit electrically connected with the comparator.

According to the exemplary embodiments of the disclosure, the testing pads and the corresponding comparator and logic circuit are disposed on the driving chip. The acceptability of the bonding resistance may be determined based on the output signal of the comparator and the logic circuit. Hence, according to the inspection system and the inspection method of the exemplary embodiments of the disclosure, the acceptability of the bonding resistance can be more accurately determined than the conventional approaches, and the inspection of bonding resistance can be more readily achieved.

In order to the make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures are described in detail below.

DESCRIPTION OF EMBODIMENTS

FIG. 1is a schematic diagram of an inspection system for bonding resistance of a display device according to an exemplary embodiment of the disclosure.

FIG. 2is a schematic diagram of the display panel ofFIG. 1.FIG. 3is a side-view diagram of the display panel, the circuit board and the driving chip ofFIG. 1. Referring concurrently toFIGS. 1,2and3, the inspection system for bonding resistance of a display device according to an exemplary embodiment includes a display panel100, at least one circuit board200, at least one driving chip300and a testing board400.

The display panel100includes a plurality of connecting conductive lines110and at least one testing conductive line112, wherein the connecting conductive lines110are used for inputting or outputting various signals, and the testing conductive lines112are used for inputting the testing conductive signal, as shown inFIG. 2. More specifically, the display panel100includes a substrate102, a plurality of scan lines SL, a plurality of data lines DL, a plurality of pixel structures P, a plurality of connecting conductive lines110and at lest one testing line112. The display panel is, for example, a liquid crystal (LC) display panel, an organic light emitting diode (OLED) display panel, an electrophoretic display panel or a plasma display panel, etc.

The substrate102is constituted with a material that includes, but not limited to, glass, quartz, organic polymer, or an opaque/reflective material (for example, a conductive material, metal, wafer, ceramic, or other appropriate materials) or other appropriate materials. The substrate102includes a bonding region108, a display region106, and a non-display region104.

The scan lines SL and the data lines DL are configured on the substrate102, extending from the display region106to the non-display region104. According to an exemplary embodiment, the scan lines SL and the data lines DL cross each other, and an isolation layer is disposed between the scan lines SL and the data lines DL. Alternatively speaking, the extension direction of the data lines DL is not parallel to the extension direction of the scan lines SL. More specifically, the extension direction of the data lines D is perpendicular to the extension direction of the scan lines SL. Moreover, the scan lines SL and the data lines DL belong to different film layers. For the consideration of conductivity, the scan lines SL and the data lines DL are formed with a metal material. However, it is to be understood that these exemplary embodiments are presented by way of example and not by way of limitation. In other exemplary embodiments, other conductive materials may be applied for the scan lines SL and the data lines DL. For example, alloy, metal nitride, metal oxide, metal oxynitride or other appropriate materials or a stacked layer of metal material and other conductive materials which may provide sufficient conductivity.

The pixel structure P is disposed in the display region106of the substrate102, and each pixel structure P is electrically connected with the corresponding scan line SL and the corresponding data line DL. According to an exemplary embodiment, the pixel structure P includes a switching device T and a pixel electrode PE, and the switching device T is electrically connected with the scan line SL and the data line DL, while the pixel electrode PE is electrically connected with the switching device T. The aforementioned switching device T could be a bottom gate thin film transistor or a top gate thin film transistor. The pixel electrode PE may be transmissive pixel electrode, a reflective pixel electrode or a transflective pixel electrode.

Moreover, the scan lines SL and the data lines DL extend from the display region106to the non-display region104to electrically connect with the driving chip300, and each of the scan lines SL and each the data lines DL are respectively connected with a corresponding connecting conductive line110. The connecting conductive lines110include conductive lines110aand pads110b. Further, in an exemplary embodiment, the testing conductive line112is disposed between the above plurality of connecting conductive lines110, and the testing conductive line112is not electrically connected with the pixel structure P in the display region106. In an exemplary embodiment of the disclosure as shown inFIGS. 1 and 2, one testing conductive line112is illustrated. However, the number of the testing conductive line should not be construed as limited to the embodiment set forth herein; in other exemplary embodiments, the number of the testing conductive line could be one or a plurality thereof. In this exemplary embodiment of the disclosure, the testing conductive line112may include a conductive line112aand a testing pad112b. The bonding region108inFIG. 2depicts a chip press bonding region; in other words, the driving chip300is actually bonded in the bonding region108.

According to an exemplary embodiment of the disclosure, if the above display panel is a liquid crystal display panel, the substrate102may further dispose with an opposite substrate and a liquid crystal layer (not shown). If the above display panel is an organic light emitting display panel, the substrate102may further dispose with an organic light emitting layer and an opposite substrate (not shown). If the above display panel is an electrophoretic display panel, the substrate102may further disposed with an opposite substrate and an electrophoretic display layer (not shown). In other words, the invention may be embodied in many different types of display panel.

The driving chip300includes a plurality of connecting contact points302and at least one testing contact point304, such as conductive balls or conductive pins, that are respectively electrically connected with the connecting conductive lines110and the testing conductive line112of the display panel100. According to an exemplary embodiment, the connecting contact points302of the driving chip300is electrically connected with the connecting conductive lines110via the connecting pads110bof the display panel100, and the testing contact point304of the driving chip300is electrically connected with the testing conductive line112via the testing pads112bof the display panel100.

Additionally, the driving chip300also includes a comparator306and a logic circuit308integrated in the driving chip300. The comparator306and the testing pad304are electrically connected, and the logic circuit308and the comparator306are electrically connected. According to an exemplary embodiment of the disclosure, the driving chip300further includes a register310for temporary storing the information of the logic circuit308.

Although certain illustrated embodiment herein refers one driving chip300, it is to be understood that these embodiments are presented by way of example and not by way of limitation, and the number of driving chip300is not to be limited. Actually, the number of the driving chip300is related to the dimension of the display panel100. Hence, the driving chip300may include at least one gate driving chip, at least one source driving chip, at least one integrated circuit integrated chip or a combination thereof.

Although the circuit board200is electrically connected with the testing conductive line112(and the connecting conductive line110) of display panel100. In an exemplary embodiment, the circuit board200includes at least one flexible printed circuit board (FPC) or other types of circuit board. Further, an anisotropic conductive film (ACF)500bis typically used to electrically connect the circuit board200with the testing conductive line112(and the connecting conductive lines110). More specifically, the circuit board200includes a plurality of conductive lines202, and the plurality of conductive lines202respectively electrically connect with the testing conductive line112(and the connecting conductive lines110).FIG. 3is a schematic diagram illustrating the electrically connection of the testing conductive line112(and the connecting conductive lines110).

It is worthy to point out that, according to an exemplary embodiment, the driving chip300and the circuit board200are bonded on the display panel100via anisotropic conductive films500aand500b, respectively, and the testing contact point304(and the connecting contact points302) of the driving chip300is electrically connected with the testing conductive line112(and the connecting conductive lines110) of the display panel100. More specifically, after the fabrication of the display panel100, anisotropic conductive films500a,500bare disposed in specific regions on the display panel100. Thereafter, the driving chip300and the circuit board200are placed on the anisotropic conductive films500a,500b. Further, via a thermal compression bonding process, the driving chip300and the circuit board200are bonded on the display panel100through the anisotropic conductive films500a,500b, and the driving chip300(the connecting contact point302and the testing contact points304) and the circuit board200(conductive lines202) are only electrically connected with the display panel100(testing conductive line112and the connecting conductive lines110) in the vertical direction. Since this technique is known in the art, it will not be further disclosed herein.

Generally speaking, if abnormality occurs during the above thermal compression bonding process, the bonding resistance (R3) between the driving chip300and the display panel100and/or the bonding resistance (R1) between the circuit board200and the display panel100become too high. Hence, an inspection system of an exemplary embodiment of the disclosure is further disposed with a testing board400, which is electrically connected with the circuit board200.

As shown inFIGS. 1 and 3, the above testing board400may provide a test signal (voltage value Vx), and the test signal (Vx) is transmitted to the testing contact point304of the driving chip300through the circuit board200and the testing conductive line112of the display panel100. During the transmission of the test signal (Vx), a voltage drop is resulted from the contact resistance (R3) between the driving circuit300and the display panel100, the resistance (R2) of the testing conductive line112, and the contact resistance (R1) between the circuit board200and the display panel100, and the ultimate voltage of the test signal (Vx) is Vin. Thereafter, this test signal Vin is compared with a reference signal (voltage value Vref) in the comparator306, and the logic circuit308determines the comparison result, which could be further transformed into digital signal for output, of the comparator306.

According to an exemplary embodiment of the disclosure, after the above logic circuit308determines the comparison result of the comparator306, the logic circuit308also outputs the above comparison result to the testing board400through one of the connecting conductive lines110of the display panel100. According to another exemplary embodiment of the disclosure, if the driving chip300further includes a register310, the comparison result is temporarily stored in the register310after the logic circuit308determines the comparison result of the comparator306, and then the comparison result is output to the testing board400via one of the connecting conductive lines110of the display panel100.

More particularly, if the logic circuit308determines the test signal (voltage value Vin) in the comparator306being greater than the reference signal (Vref), the logic circuit308outputs a first signal (for example, output 1) based the comparative result through one of the connecting conductive lines100to indicate the test result is normal. Thereafter, the entire bonding resistance could be rapidly interpreted as normal through the microprocessor that is electrically connected with the testing board400.

Conversely, if the logic circuit308determines the test signal (voltage Vin) in the comparator306being smaller than the reference signal (Vref), the voltage drop to the test signal may also result from other additional resistance (Rx), aside from the contact resistance (R3) between the driving chip300and the display panel100, the contact resistance (R2) of the testing line112, and the contact resistance between the circuit board200and the display panel100. The so-called additional resistance (Rx) may be a value calculated based on an atypical bonding between the driving chip300and the display panel100and/or an atypical bonding between the circuit board200and the display panel100. Hence, the logic circuit308outputs as a second signal (for example, output 0) based on the above-mentioned comparison result through one of the connecting conductive lines110to indicate the test result being abnormal. Thereafter, the entire bonding resistance could be rapidly interpreted as abnormal through the microprocessor that is electrically connected with the testing board400.

FIG. 4is a schematic diagram of an inspection system for bonding resistance of a display device according to another exemplary embodiment of the disclosure. The exemplary embodiment inFIG. 4is similar to the exemplary embodiment inFIG. 1, and wherever possible, the same reference numbers are used to refer to the same or like parts in both Figures. The difference between the exemplary embodiment inFIG. 4and the exemplary embodiment inFIG. 1is that the driving chip300in this exemplary embodiment is also disposed with three testing contact points304, aside from the plurality of testing contact points302. The three testing contact points304are respectively disposed at the left side, the center and the right side of the driving chip300. The display panel100, which is configured under the driving chip300, is also disposed with three testing conductive lines112(testing pads112b) corresponding to the three testing pads304above. More specifically, the above three testing pads304and the comparator306are electrically connected. The exemplary embodiments of the disclosure may include, according the testing requirements, one or multiple testing pads304disposed on the driving chip300, and one or multiple corresponding testing conductive lines112(testing pads112b) disposed on the display panel100. The above arrangements of the testing contact points304and testing conductive lines112can be adjusted according actual requirements, and are not to be construed as limiting the scope of the invention.

During the bonding inspection, the testing board400outputs test signals (voltage Vx) to the three testing pads304. Thereafter, the test signal (Vin) in the comparator306is compared with the reference signal Vref, and then the logic circuit308determines the comparison result of the comparator306.

With the three testing pads304disposed at the left side, the center and the right side of the driving chip300, it is feasible to inspect the bonding resistance between the driving chip300and the display panel100at different positions. More specifically, for a display device using a driving chip300with a larger dimension, the design as disclosed in the exemplary embodiments is particularly useful in enhancing the inspection accuracy of the bonding resistance.

Although the illustrated embodiments ofFIG. 4refer to the application of three testing pads304disposed at the left side, the center and the right side of the driving chip300, it is to be understood that these embodiments are presented by way of example and not by way of limitation. According to other exemplary embodiments, two testing contact points may be disposed on the right side and on the left side of the driving chip300, respectively, or more than three testing contact points may be disposed on the driving chip300.

Moreover, if the driving chip300is disposed with a plurality of testing contact points304, a set of comparator306and logic circuit308, in addition to the one set of commonly used comparator306and logic circuit308, may also be disposed correspondingly to each testing pad.

FIG. 5is a flow diagram of steps in an exemplary inspection method of a display device according to one exemplary embodiment of the disclosure. Referring toFIG. 5, the inspection method for a display device in the exemplary embodiments includes providing a display device (S10). The above-mentioned display device includes, a liquid crystal (LC) display panel, an organic light emitting diode (OLED) display panel, an electrophoretic display panel or a plasma display panel, etc.

Thereafter, a light on test (Step S12) is performed. The light on test is performed on the display device to inspect the entire image of the display device for abnormal testing pattern or defect. If abnormality is identified in the light on test (step S12), the display device is considered as a defective product (step S13). The above defective product, depending on the degree of defectiveness, may be discarded as scrap or reworked.

If the light on test (step S12) result is normal, a bonding resistance test (step S14) is performed. In an exemplary embodiment, the bonding resistance test (step S14) is performed with the bonding resistance inspection system as shown inFIG. 1or the bonding resistance inspection system as shown inFIG. 4.

If abnormality is being detected in the bonding resistance test (step S14), the display device is considered as a detective product (step S15). In other words, the product is defective probably because the bonding resistance between the driving chip and the display panel is too high or the bonding resistance between the circuit board and the display panel is too high. Generally speaking, when the bonding resistance between the driving chip and the display panel or the bonding resistance between the circuit board and the display panel is determined to be too high, the bonding procedure between the driving chip of the display device and the display panel or the bonding procedure between the circuit board and the display panel is reworked. After the rework process is completed, the bonding resistance test (step S14) is repeated.

If the result of the bonding resistance test (step S14) result is normal, it implies the display device is a good product (step S16), and the criteria for product shipment is achieved.

In the above step S16, when the display device is determined be a good product, prior to the shipment of products, the testing board in the inspection system (FIGS. 1 and 4) of bonding resistance is removed to form the display device as shown inFIGS. 6A and 6B. More particularly, the display device inFIG. 6Ais a schematic diagram of a display device after a bonding test using the inspection system inFIG. 1. The display device inFIG. 6Bis a schematic diagram of a display device after a bonding test using the inspection system inFIG. 4. In the display devices shown inFIGS. 6A and 6B, the testing pad304, the comparator306and the logic circuit308(even the register310) remain inside the driving chip300. Since the above devices used in the testing only have an electrical connection with the conductive lines112of the display panel100, the presence of these devices used in the testing does not affect the display operation of the display device.

According to the above exemplary embodiments of the disclosure, testing contact points are disposed on, and a comparator and a logic circuit are also correspondingly disposed on the driving chip of the display device. Based on the signals output from the comparator and the logic circuit, whether or not the bonding resistance between the display panel and the logic circuit in the display device or/and the bonding resistance the display panel and the circuit board is in the acceptable range can be promptly determined. Hence, according to the inspection system and the inspection method of the exemplary embodiments of the disclosure, the acceptability of the bonding resistance can be more accurately determined than the conventional approaches, and the inspection of bonding resistance can be more readily achieved.