Display module, preparation method thereof and display device

Abstract

The application provides a display module, a detection method thereof and a display device. The output pad area of the non-display area of the display substrate of the display module comprises a plurality of spaced binding points. The output pad area is divided into a center area located in the middle and a peripheral area located at the periphery of the center area. The center area comprises a plurality of binding points, and the peripheral area comprises a plurality of binding points. The display module further comprises an impedance detection structure. The impedance detection structure comprises a conductive trace, a lead wire and an impedance detection point. The conductive trace is arranged on the display substrate and is arranged in the same layer as the binding points. The conductive trace surrounds or is electrically connected with the binding points of the center area. One end of the lead wire is electrically connected with the free end of the conductive trace, and the other end of the lead wire is electrically connected with the impedance detection point. The application achieves the purpose of more efficient and comprehensive detection of whether the output pad area has a photoresist peeling defect by arranging the impedance detection structure.

Description

Technical Field

[0001] This application belongs to the field of display panel manufacturing technology, and more specifically, relates to display modules and their preparation methods, and display devices. Background Technology

[0002] After the production of flexible OLED (Organic Light-Emitting Diode) modules, high-temperature and high-humidity long-term reliability testing is required to verify product quality. During reliability testing, S-shaped bright lines are a common defect. This defect is usually caused by photoresist peeling from the IC bump (Integrated Circuit Bump) extending to the COP (Chip on Panel) Output Pad area. Currently, the method for detecting COP peeling problems is to measure the COP bonding impedance. However, the number of COP bonding impedance measurement points is limited, such as... Figure 1 As shown, in existing detection methods, impedance measurement points are only distributed at both ends of the COPOutputPad. Therefore, it is limited to detecting whether peeling occurs at both ends of the COP OutputPad, and cannot comprehensively detect whether peeling occurs in the COP Output area. Furthermore, the detection efficiency is low. Summary of the Invention

[0003] The purpose of this application is to provide a display module to solve the technical problem that the output pad area of ​​the display module in the prior art cannot efficiently and comprehensively detect photoresist peeling.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows: a display module, including a display substrate, the display substrate including a non-display area and a display area surrounded by the non-display area, the non-display area including an output pad area packaged by COP, the output pad area including a plurality of spaced bonding points, the output pad area being divided into a central area located in the middle and a peripheral area located around the central area, the central area including a number of bonding points, and the peripheral area including a plurality of bonding points; the display module further includes an impedance detection structure, the impedance detection structure including conductive traces, leads and impedance measuring points; the conductive traces are disposed on the display substrate and disposed on the same layer as the bonding points;

[0005] The conductive trace surrounds or is electrically connected to the binding point of the central area. One end of the lead is electrically connected to the free end of the conductive trace, and the other end of the lead is electrically connected to the impedance measurement point.

[0006] Optionally, the conductive trace is in the shape of a ring, which is arranged around the periphery of the central region, and there are gaps between the conductive trace and the bonding point of the innermost ring in the outer periphery region and the bonding point of the outermost ring in the central region.

[0007] The conductive trace has a notch, forming a first free end and a second free end; the lead includes a first lead and a second lead, and the impedance measuring point includes a first impedance measuring point and a second impedance measuring point; one end of the first lead is electrically connected to the first free end, and the other end of the first lead is electrically connected to the first impedance measuring point; one end of the first lead is electrically connected to the first free end, and the other end of the first lead is electrically connected to the first impedance measuring point.

[0008] Optionally, the central area includes the bonding points located in the middle row of the output pad area; or,

[0009] The central area includes at least a portion of the bonding points located in the middle column of the output pad area;

[0010] The shape formed by the conductive traces surrounding the central area can be one of the following: rectangle, triangle, trapezoid, or irregular polygon.

[0011] Optionally, the outer perimeter region consists of the outermost ring of bonding points of the output pad region, and the central region consists of the remaining bonding points.

[0012] Optionally, the bonding point located at the center of the output pad area is taken as the center bonding point, and the central area is taken as the center bonding point; one end of the conductive trace is electrically connected to the center bonding point, and the other end of the conductive trace extends out of the output pad area and is electrically connected to the lead.

[0013] Optionally, the conductive traces and impedance measurement points are arranged in a staggered manner. A line-changing hole is provided on the outer periphery of the output pad area on the display substrate. One end of the lead is electrically connected to a free end of the conductive trace, and the other end of the lead passes through the line-changing hole and is electrically connected to the impedance measurement point.

[0014] This application also proposes a method for detecting a display module, used to detect the impedance of the display module as described above. The method for detecting the display module includes the following steps:

[0015] Place the display module, which has undergone impedance detection preprocessing, on the testing platform;

[0016] Impedance detection is performed on the output pad area of ​​the display module;

[0017] After the host obtains the impedance value measured at the impedance measurement point, it determines whether there is photoresist peeling in the output pad area based on the change in impedance value.

[0018] Optionally, before placing the display module that has undergone impedance detection preprocessing on the testing stage, the process further includes a step of performing impedance detection preprocessing on the display module in the TP process section. The step of performing impedance detection preprocessing on the display module includes the following sub-steps:

[0019] After depositing a metal thin film layer in the output pad area of ​​the display substrate, photoresist is coated.

[0020] The output pad area is exposed and developed to form a patterned adhesive layer for conductive traces.

[0021] The output pad area is etched with metal and then processed to form a conductive metal circuit pattern.

[0022] Optionally, the impedance detection step for the output pad area of ​​the display module includes the following sub-steps:

[0023] The probe of the detection device is in electrical contact with the impedance measurement point;

[0024] The detection device acquires the impedance value at the impedance measurement point;

[0025] The detection device transmits the impedance value to the host computer;

[0026] The steps to determine whether there is photoresist peeling in the output pad area based on the change in impedance value include the following:

[0027] The host compares the acquired impedance value with a pre-stored preset threshold.

[0028] If the impedance value is greater than the preset threshold, it is determined that there is a problem of photoresist peeling in the output pad area;

[0029] If the impedance value is equal to or less than the preset threshold, it is determined that there is no photoresist peeling in the output pad area.

[0030] This application also proposes a display device comprising the display module as described above.

[0031] The beneficial effects of the display module provided in this application are as follows: Compared with the prior art, this application adds conductive traces to the output pad area, and the conductive traces are electrically connected to impedance measurement points through leads to form an impedance detection structure. If photoresist peeling occurs in the output pad area, moisture will invade the bonding point of the output pad area from the photoresist peeling point, and at the same time, it will cause corrosion of the conductive traces located on the periphery of the central area of ​​the output pad area, thereby causing a change in the impedance of the conductive traces. In this way, after the detection device is electrically connected to the impedance measurement point, the impedance change of the conductive traces can be obtained, thereby determining whether photoresist peeling or other defects have occurred in the pad area. Compared with the current common solutions that can only test whether photoresist peeling has occurred at both ends of the output pad area, in the technical solution of this application, the added conductive traces are not connected to any circuit, or are only connected to a bonding point in the central area, so they will not couple with other overlapping lines, and thus will not cause other defects. Furthermore, the technical solution of this application has the advantage of high feasibility. It does not increase the number of photomasks, and it does not require setting multiple impedance measurement points for bonding points as in the prior art. The impedance detection structure of this application only requires two or one impedance measurement point to achieve efficient and comprehensive impedance detection of the output pad area, thereby better knowing whether there are defects such as photoresist peeling in the output pad area, and effectively improving the product yield of the display module. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A simplified structural diagram of impedance detection for the output pad area in existing technology;

[0034] Figure 2 A simplified structural diagram of a display module provided in one embodiment of this application;

[0035] Figure 3 A simplified structural diagram of a display module provided in another embodiment of this application;

[0036] Figure 4 A simplified structural diagram of a display module provided in another embodiment of this application;

[0037] Figure 5 A flowchart illustrating a method for detecting a display module according to an embodiment of this application;

[0038] Figure 6This is a flowchart of impedance detection in a detection method for a display module provided in an embodiment of this application.

[0039] Explanation of icon numbers:

[0040]

[0041] Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In this application, unless otherwise expressly specified and limited, the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this application and simplifying the description. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0043] This application provides a display module.

[0044] Please refer to Figures 1 to 4 In one embodiment, the display module includes a display substrate, which includes a non-display area and a display area surrounded by the non-display area. The non-display area includes an output pad area 100 that is COP-packaged. The output pad area 100 includes a plurality of spaced bonding points 110. The output pad area 100 is divided into a central area 120 located in the middle and a peripheral area 130 located around the central area 120. The central area 120 includes a plurality of bonding points 110, and the peripheral area 130 includes a plurality of bonding points. 110; The display module also includes an impedance detection structure, which includes a conductive trace 210, a lead 220, and an impedance measuring point 230. The conductive trace 210 is disposed on the display substrate and is disposed on the same layer as the bonding point 110. The conductive trace 210 surrounds the bonding point 110 of the central region 120 or is electrically connected to the bonding point 110 of the central region 120. One end of the lead 220 is electrically connected to the free end of the conductive trace 210, and the other end of the lead 220 is electrically connected to the impedance measuring point 230.

[0045] After the display module, such as the flexible OLED module in this embodiment, is produced, a high-temperature, high-humidity, long-term reliability test is required to verify the product quality. During reliability testing, common defects include S-shaped bright lines caused by photoresist peeling. This defect is usually caused by photoresist peeling extending to the output pad area 100 due to IC bump; currently, the method for detecting photoresist peeling problems is to measure the impedance of the bonding point 110. However, in existing testing solutions, specifically... Figure 1 As shown, since the impedance measurement points 230 of the bonding point 110 are limited and are only distributed at both ends of the output pad area 100, it is only possible to detect whether photoresist stripping has occurred at both ends of the output pad area 100, and it is not possible to comprehensively detect whether photoresist stripping has occurred in the output pad area 100. Furthermore, since there are many impedance measurement points 230 that need to be detected, its detection efficiency is also low.

[0046] To address the aforementioned technical problems, based on the aforementioned design, in this embodiment, a conductive trace 210 is added to the output pad area 100, and the conductive trace 210 is electrically connected to the impedance measurement point 230 via a lead 220 to form an impedance detection structure. If photoresist peeling occurs in the output pad area 100, moisture will invade the bonding point 110 of the output pad area 100 from the photoresist peeling point, and will also cause corrosion of the conductive trace 210 located around the central area 120 of the output pad area 100, thereby causing a change in the impedance of the conductive trace 210. Thus, by electrically connecting the detection device to the impedance measurement point 230, the impedance change of the conductive trace 210 can be obtained, thereby determining whether photoresist peeling or other defects have occurred in the pad area. Compared to current common solutions that only test whether photoresist stripping has occurred at both ends of the output pad area 100, the technical solution of this application adds conductive traces 210 that are not connected to any circuits, or are only connected to a bonding point 110 in the central area 120, thus avoiding coupling with other overlapping lines and preventing other defects. Furthermore, the technical solution of this application has the advantage of high feasibility, does not increase the number of photomasks, and does not require multiple impedance measurement points 230 at bonding points 110 as in existing technologies. The impedance detection structure of this application only requires two or one impedance measurement point 230 to achieve efficient and comprehensive impedance detection of the output pad area 100, thereby better identifying whether photoresist stripping or other defects exist in the output pad area 100, effectively improving the product yield of the display module.

[0047] It should be noted that the impedance testing of this display module was conducted during or after the high-temperature and high-humidity long-term reliability test. The high-temperature and high-humidity long-term reliability test mainly involves dynamic bending at high and low temperatures within a temperature range of -40℃ to 85℃ and a humidity of 85% to verify the encapsulation layer's resistance to water and oxygen permeation. The impedance detection structure of this application includes two scenarios: In the first scenario, the conductive trace 210 surrounds the central region 120 of the output pad area 100, enabling comprehensive photoresist stripping detection. This is because photoresist stripping in the output pad area 100 is typically formed by the extension of photoresist stripping from the integrated circuit bumps in adjacent areas to this region. If the photoresist stripping has extended to the outer region 130 of the output pad, it indicates that moisture has invaded the outer region 130. Since the conductive trace 210 is located inside the outer region 130, it will also be able to sense the moisture intrusion to a certain extent, thereby causing a change in the impedance value measured by the impedance measuring point 230, thus enabling the detection of defects such as photoresist stripping in the pad area. If moisture has invaded the central region 120, the central region 120 will directly detect the change in its impedance, also enabling the detection of defects such as photoresist stripping in the pad area. In the second case, since the conductive trace 210 is directly electrically connected to the bonding point 110 of the central region 120, if an abnormal change in the impedance value of the bonding point 110 is detected during testing, it can be directly determined that moisture has invaded the bonding point 110, that is, the photoresist peeling has extended to the bonding point 110 of the central region 120, thereby efficiently detecting defects such as photoresist peeling in the pad area.

[0048] It should also be noted that in this embodiment, the display module is specifically a flexible OLED (Organic Light-Emitting Diode) module, and the corresponding display substrate is a flexible substrate. Of course, in other embodiments, the display module can also be other types of modules, and the display substrate can also be a rigid glass substrate, etc. The conductive trace 210 is specifically a TP-M2 (Touch Panel-Metal Mesh 2nd Generation) trace. Since the display module is a flexible OLED module, it is more suitable to use TP-M2 traces for conductive traces 210, because TP-M2 traces replace the traditional ITO conductive layer by forming a micron-level metal mesh (such as silver or copper alloy) through nanoimprinting or photolithography, thereby improving the conductivity stability and touch response speed when the screen is bent. In addition, the resistance change of TP-M2 traces is smaller in dynamic bending tests, and it has better flexibility. Furthermore, the display module in this embodiment, especially the output pad area 100, adopts a COP bonding packaging process. The material of the conductive trace 210 can preferably be a humidity-sensitive resistor material, so as to better sense whether moisture enters the display area through the packaging area.

[0049] Furthermore, such as Figure 2 As shown, in one embodiment, the conductive trace 210 is looped around the periphery of the central region 120. Gaps exist between the conductive trace 210 and the innermost binding point 110 in the outermost ring of the peripheral region 130 and the outermost binding point 110 in the central region 120. This ensures that the added conductive trace 210 does not connect to any circuit; that is, the conductive trace 210 will not couple with other overlapping lines, thus preventing other defects. It is particularly important to note that, due to the small spacing between adjacent binding points 110, to ensure that the conductive trace 210 does not connect to any circuit, when designing the wiring position of the conductive trace 210, it is best to ensure that the spacing between the conductive trace 210 and its adjacent binding points 110 on both sides is equal. This avoids electrical connections caused by excessively small spacing between the conductive trace 210 and the binding point 110 on one side.

[0050] Specifically, in such Figure 2 and Figure 3 In both embodiments shown, the conductive trace 210 is looped. The conductive trace 210 has a notch, forming a first free end and a second free end; the lead 220 includes a first lead 220 and a second lead 220, and the impedance measuring point 230 includes a first impedance measuring point 230 and a second impedance measuring point 230; one end of the first lead 220 is electrically connected to the first free end, and the other end of the first lead 220 is electrically connected to the first impedance measuring point 230. In other words, for the looped conductive trace 210, to ensure the formation of a detection loop, two free ends are required, and each free end is electrically connected to an impedance measuring point via a lead 220. Of course, if the conductive trace 210 is a single line, for example in… Figure 4 In another embodiment shown, the conductive trace 210 has no notch. One free end of the conductive trace 210 is directly electrically connected to a bonding point 110, and the other free end of the conductive trace 210 is directly electrically connected to an impedance measurement point 230 via a lead 220. Here, to allow the ring-shaped conductive trace 210 to surround more bonding points 110, thereby achieving more comprehensive impedance detection, the notch in the conductive trace 210 should be as narrow as possible, such as... Figure 2 and Figure 3As shown, the notches of the conductive traces 210 are all located below a bonding point 110, and the width of the notch is only slightly larger than the width of the bonding point 110. That is, the first free end and the second free end of the conductive trace 210 extend out of the gap space on the left and right sides of the bonding point 110, respectively. Of course, in other embodiments, the notches of the conductive traces 210 may also be larger than the width of multiple bonding points 110, that is, the first free end and the second free end of the conductive trace 210 are separated by multiple bonding points 110.

[0051] Further, the scope of the central region 120 includes the bonding points 110 located in the middle row of the output pad region 100; or, the scope of the central region 120 includes at least a portion of the bonding points 110 located in the middle column of the output pad region 100. Specifically, as shown in... Figure 2 In one embodiment shown, multiple bonding points 110 are arranged in 3 rows and 34 columns at intervals. The central region 120 includes most of the bonding points 110 in the middle row. Thus, for this long strip-shaped arrangement of bonding points 110 extending horizontally in this embodiment, by setting the central region 120 to the middle row, the conductive trace 210 can surround as many bonding points 110 as possible, thereby further improving the comprehensiveness of impedance detection. Figure 3 In another embodiment shown, the range of its central region 120 can be viewed as the middle portion of the bonding points 110 in the middle row of the output pad region 100.

[0052] However, this design is not limited to this; the conductive traces 210 enclosing the central region 120 can form a shape that is rectangular, triangular, trapezoidal, or an irregular polygon. For example, in... Figure 2 In one embodiment shown, the shape formed by the conductive traces 210 surrounding the central region 120 is trapezoidal; in such... Figure 3 In another embodiment shown, the shape formed by the conductive trace 210 surrounding the central region 120 is rectangular. The shape formed by the conductive trace 210 surrounding the central region 120 can be determined according to actual testing requirements and is not particularly limited here. Of course, considering that the conductive trace 210 does not form an electrical connection with any bonding point 110 when it is in a loop, the shape formed by the conductive trace 210 surrounding the central region 120 is actually also related to the pattern formed when all bonding points 110 are arranged at intervals. For example, in... Figure 2 and Figure 3In the two embodiments shown, the three rows of bonding points 110 are actually divided into three regions in the left-right direction. The arrangement of bonding points 110 in each region is different. The bonding points 110 in the left region are all inclined to the right in the upward direction, the bonding points 110 in the right region are all inclined to the left in the upward direction, and the multiple bonding points 110 in the middle are vertically arranged in the up-down direction. The bonding points 110 of the entire output pad area 100 are symmetrically arranged along the central axis. Therefore, as Figure 2 In one embodiment shown, when the central region 120 is defined as the bonding point 110 of the middle row of the output pad region 100, the shape formed by the conductive trace 210 surrounding the central region 120 is an isosceles trapezoid; while in... Figure 3 In another embodiment shown, when the central region 120 is defined as the middle portion of the bonding point 110 in the middle row of the output pad region 100, the shape formed by the conductive trace 210 surrounding the central region 120 is a rectangle. That is, in different embodiments, different arrangements of the bonding points 110 and different definitions of the central region 120 can all result in different shapes formed by the conductive trace 210 surrounding the central region 120. These shapes should be specifically set according to the actual situation and should not be subject to special restrictions.

[0053] Here, the positions of lead 220 and impedance measuring point 230 can be on the left, right, or in the middle, mainly depending on the actual circuit settings on the display substrate. For example, in Figure 2 In one embodiment shown, for the purpose of avoiding related components or circuits, the lead 220 and the impedance measurement point 230 are preferably located on the left side of the lower region of the output pad area 100, away from the display area. However, in... Figure 3 and Figure 4 In the other two embodiments shown, for the sake of convenient wiring and minimizing the length of the conductive lead 220, the lead 220 and the impedance measurement point 230 are preferably located in the middle of the lower region of the output pad area 100 away from the display area, that is, below the central region 120 in the corresponding embodiment.

[0054] Furthermore, such as Figure 2 As shown, in one embodiment, the peripheral region 130 is composed of the outermost bonding points 110 of the output pad region 100, and the central region 120 is composed of the remaining bonding points 110. In this way, the central region 120 surrounded by the conductive traces 210 will be as large as possible, and the number of bonding points 110 that can be directly detected will be as large as possible. This is beneficial for further improving the comprehensiveness of the detection, making the detection of photoresist peeling defects in the output pad region 100 more accurate, comprehensive, and efficient.

[0055] Furthermore, such as Figure 4As shown, in another embodiment, the bonding point 110 located at the center of the output pad area 100 is designated as the center bonding point 110, and the central area 120 is designated as the center bonding point 110. One end of the conductive trace 210 is electrically connected to the center bonding point 110, and the other end of the conductive trace 210 extends out of the output pad area 100 and is electrically connected to the lead 220. In other words, in this embodiment, the conductive trace 210 only tests one bonding point 110 in the central area 120, namely the center bonding point 110. It can be understood that by testing the impedance of the center bonding point 110, the photoresist peeling situation at the center of the output pad area 100 can be directly determined. If the impedance value measured at the center bonding point 110 changes abnormally, it can be directly determined that the photoresist peeling has extended to the center bonding point 110, thereby efficiently and conveniently and immediately identifying defects such as photoresist peeling in the pad area. Here, to facilitate the conductive lead 220 extending out of the output pad area 100 with the shortest possible distance, i.e., to minimize the trace length of the conductive lead 220, the conductive trace 210, lead 220, and impedance measuring point 230 are preferably located in the middle. Of course, in other embodiments, the positions of the lead 220 and impedance measuring point 230 can also be located in other places, such as, but not limited to, the left or right side of the lower region of the output pad area 100 away from the display area, mainly determined according to the actual circuit layout on the display substrate.

[0056] Furthermore, such as Figure 2 As shown, in one embodiment, the conductive trace 210 and the impedance measuring point 230 are staggered. A line-changing hole 240 is provided on the outer periphery of the output pad area 100 on the display substrate. One end of the lead 220 is electrically connected to a free end of the conductive trace 210, and the other end of the lead 220 passes through the line-changing hole 240 and is electrically connected to the impedance measuring point 230. It is understandable that, since the output pad area 100 is COP packaged, and to facilitate subsequent impedance testing, the conductive traces 210 and impedance measurement points 230 are preferably staggered, that is, the conductive traces 210 and impedance measurement points 230 are respectively located on different layers. In this way, a wire replacement hole 240 needs to be set at the corresponding position on the display substrate. The lead 220 can pass through the wire replacement hole 240, and its two ends are electrically connected to the free end of the conductive trace 210 and the impedance measurement point 230, respectively. This realizes the electrical connection between the conductive traces 210 and the impedance measurement points 230 located on different layers, ensuring that the photoresist peeling test of the output pad area 100 can be performed smoothly. Here, the position of the wire-changing hole 240 can follow the position of the impedance measuring point 230. For example, in one embodiment shown in Figure 2, the impedance measuring point 230 is located on the left side, and the loop notch of the conductive trace 210, i.e., the two free ends, is also located on the left side of the output pad area 100. Therefore, to facilitate wiring, the wire-changing hole 240 is also located on the left side, in front of the two impedance measuring points 230. This minimizes the bending of the wiring and helps ensure the smooth flow of the entire impedance detection circuit. Another example is shown in Figure 2. Figure 3 and Figure 4 In the other two embodiments shown, since the impedance measuring point 230 and the free end of the conductive trace 210 are both located in the middle, the replacement hole 240 is also preferably located in the middle. Of course, in other embodiments, depending on the actual circuit layout on the display substrate, the position of the replacement hole 240 may not be consistent with the position of the impedance measuring point 230 and / or the free end of the conductive trace 210 to avoid other components or circuits. Of course, if there are existing replacement holes 240 on the display substrate that can be used, these existing replacement holes 240 can be used directly without setting up replacement holes 240 separately. In this case, only the wiring design of the conductive line and the lead 220 needs to be changed.

[0057] This application also proposes a method for detecting a display module, which is used to detect the impedance of the display module as described above. Figure 5 As shown, the detection method for this display module includes the following steps:

[0058] S1. Place the display module, which has undergone impedance detection preprocessing, on the testing platform;

[0059] S2. Perform impedance detection on the output pad area 100 of the display module;

[0060] S3. After the host obtains the impedance value measured at impedance measurement point 230, it determines whether there is photoresist peeling in the output pad area 100 based on the change in impedance value.

[0061] Specifically, the testing method for this display module is performed in a high-temperature and high-humidity environment. Since the display module has undergone impedance detection preprocessing as described above, compared to the currently common solutions that can only test whether photoresist peeling has occurred at both ends of the output pad area 100, in this application's technical solution, the conductive trace 210 is electrically connected to the impedance measurement point 230 via the lead 220 to form an impedance detection structure, which can more comprehensively and efficiently detect the defect of photoresist peeling in the output pad area 100. Furthermore, the added conductive trace 210 does not connect to any circuit, or only connects to a bonding point 110 in the central area 120, thus avoiding coupling with other overlapping lines and preventing other defects. Meanwhile, the technical solution of this application does not increase the number of photomasks, and it does not require setting multiple impedance measurement points 230 for bonding points 110 as in the prior art. The impedance detection structure of this application only requires two or one impedance measurement point 230 to achieve efficient and comprehensive impedance detection of the output pad area 100, thus having the advantage of high feasibility. It can better detect whether there are defects such as photoresist peeling in the output pad area 100, and effectively improve the product yield of the display module.

[0062] Specifically, if photoresist peeling occurs in the output pad area 100, moisture will penetrate the bonding points 110 of the output pad area 100 from the peeling point. This will also cause corrosion of the conductive traces 210 located around the central area 120 of the output pad area 100, resulting in a change in the impedance of the conductive traces 210. By electrically connecting the detection device to the impedance measurement point 230, the impedance change of the conductive traces 210 can be obtained, thereby determining whether photoresist peeling or other defects have occurred in the pad area.

[0063] Furthermore, before placing the display module that has undergone impedance detection preprocessing on the testing stage, the process includes a step of performing impedance detection preprocessing on the display module in the TP process section. The step of performing impedance detection preprocessing on the display module includes the following sub-steps:

[0064] After depositing a metal thin film layer in the output pad area 100 of the display substrate, photoresist is coated.

[0065] The output pad area 100 is exposed and developed to form a metal patterned adhesive layer for the conductive traces 210.

[0066] The metal circuit pattern of conductive trace 210 is formed by metal etching and subsequent processing of the output pad area 100.

[0067] Specifically, the step of impedance detection preprocessing for the display module is the process of forming a metal circuit model pattern of conductive trace 210. This mainly involves adding conductive trace 210, i.e., a ring of TP-M2 trace, to the output pad area 100 through processes such as exposure and etching in the TP (Touch Panel) process segment of the display module.

[0068] The process of coating photoresist after depositing a metal thin film layer in the output pad area 100 of the display substrate specifically includes substrate preparation and photoresist coating processes. First, an insulating layer needs to be pre-coated on the flexible substrate to enhance surface flatness and insulation; then, a metal thin film layer is formed on the substrate through processes such as sputtering or evaporation; then, photoresist is uniformly coated and cured at 80-120℃ to remove solvent and form a stable photoresist film.

[0069] The process of exposing and developing the output pad area 100 to form the patterned metal resist layer of the conductive traces 210 specifically includes exposure and development processes. First, a photomask is aligned with the substrate, and the photomask pattern corresponds to the metal grid design of the conductive traces 210 in the relevant areas. Then, ultraviolet or deep ultraviolet light is used for exposure, and the exposure energy is adjusted according to the type of photoresist to ensure pattern clarity. Then, the photoresist in the exposed area or the unexposed area is dissolved by the developer, thereby forming the patterned resist layer of the metal traces.

[0070] The process of metal etching of the output pad area 100 and subsequent processing to form the metal circuit pattern of the conductive trace 210 specifically includes metal etching, resist removal and cleaning, and post-processing. First, wet etching can be used to selectively dissolve the exposed metal layer, or dry etching can be used to bombard the metal layer under high vacuum. Then, photoresist is removed to remove residual resist layers, rinsed with ultrapure water, and dried with nitrogen to avoid metal oxidation or contamination. Finally, the so-called post-processing includes using low-temperature annealing to eliminate etching stress to improve metal conductivity and adhesion, or depositing an insulating layer to cover the metal circuit to prevent oxidation and mechanical damage.

[0071] It should be noted that, for the sake of saving on the production process, the formation of the conductive trace 210 does not need to be completed separately, but can be completed together with the metal model patterning of other circuits.

[0072] Furthermore, such as Figure 6 As shown, in one embodiment, the step of impedance detection of the output pad area 100 of the display module includes the following sub-steps:

[0073] S21, The probe of the detection device is in electrical contact with the impedance measuring point 230;

[0074] S22. The detection device acquires the impedance value at impedance measurement point 230;

[0075] S23. The detection device transmits the impedance value to the host.

[0076] It should be noted that various detection devices can be used, such as, but not limited to, detection using a detection chip or probe. After the detection chip or the detection device equipped with a probe obtains the impedance value at impedance measurement point 230, the detection device transmits the impedance value to the relevant host computer connected to it, and then the host computer performs the result determination. Here, the information connection between the detection device and the host computer is accomplished using a communication system, which can be implemented in various ways. It can be wireless transmission, such as, but not limited to, 5G industrial IoT, Wi-Fi and industrial wireless sensor networks, HS-LINK, etc., or wired transmission via cable connection, such as, but not limited to, Gigabit Ethernet, USB3Vision, Camera Link, and CoaXPress, etc. The communication system can include, but is not limited to, a signal receiving module and a signal transmitting module, or a signal transceiver module integrating both.

[0077] In one specific embodiment, a detection chip is used to detect the impedance measurement point 230. Two corresponding pins of the detection chip are electrically connected to the two impedance measurement points 230, respectively; that is, the probe of the detection device corresponds to the pin of the detection chip. When the two are electrically in contact, the detection chip can obtain the impedance value of the impedance measurement point 230. Specifically, this test chip can be a lighting chip. Of course, in other embodiments, the test chip can be other suitable chips. However, in this embodiment, using a lighting chip as the test chip only requires adding a program to the lighting program to obtain the impedance value of the impedance measurement point 230. Then, the obtained impedance value of the impedance measurement point 230 can be displayed on the display screen of the lighting device, thereby achieving efficient detection of defects such as photoresist peeling in the output pad area 100. This method of setting a lighting chip compatible with impedance detection can effectively save detection costs.

[0078] The steps to determine whether there is photoresist peeling in the output pad area 100 based on the change in impedance value include the following:

[0079] S31. The host compares the acquired impedance value with the pre-stored preset threshold.

[0080] S32. If the impedance value is greater than the preset threshold, it is determined that there is a problem of photoresist peeling in the output pad area 100.

[0081] S33. If the impedance value is equal to or less than the preset threshold, it is determined that there is no photoresist peeling defect in the output pad area 100.

[0082] It should be noted that the preset threshold can be obtained by impedance testing at impedance measurement point 230 of the qualified output pad area 100. However, the preset threshold may differ for different display module models. In this case, before making a judgment, it is necessary to confirm the type of display module and compare it with the corresponding preset threshold to obtain the correct judgment result.

[0083] This application also proposes a display device comprising the display module as described above. Specifically, in one embodiment, the display module is a flexible OLED module, and the display panel is a flexible OLED panel. It is understood that since flexible OLED modules typically use flexible substrates made of materials such as, but not limited to, polyimide (PI), i.e., the flexible OLED module display substrate is a flexible substrate that is easily bent, defects such as photoresist peeling are more likely to occur during the manufacturing process. Especially in the output pad area 100 located in the non-display area, defects such as photoresist peeling extending to the output pad area 100 due to IC bump are more likely to occur. Therefore, it is essential to detect photoresist peeling in the output pad area 100. In the technical solution of this application, if photoresist peeling occurs in the output pad area 100, moisture will invade the bonding point 110 of the output pad area 100 from the photoresist peeling point. At the same time, it will also cause corrosion of the conductive trace 210 located around the central area 120 of the output pad area 100, thereby causing a change in the impedance of the conductive trace 210. By setting up an impedance detection structure, after impedance detection at the impedance measurement point 230, the impedance change of the conductive trace 210 can be obtained, thereby determining whether photoresist peeling or other defects have occurred in the pad area.

[0084] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A display module, comprising a display substrate, the display substrate including a non-display area and a display area surrounded by the non-display area, the non-display area including a COP-packaged output pad area, the output pad area including a plurality of spaced bonding points, characterized in that, The output pad area is divided into a central area in the middle and an outer area around the central area. The central area includes several bonding points, and the outer area includes multiple bonding points. The display module also includes an impedance detection structure, which includes conductive traces, leads, and impedance measurement points. The conductive traces are disposed on the display substrate and are disposed on the same layer as the bonding points. The conductive trace surrounds or is electrically connected to the binding point in the central region. One end of the lead is electrically connected to the free end of the conductive trace, and the other end of the lead is electrically connected to the impedance measurement point.

2. The display module as described in claim 1, characterized in that, The conductive trace is in a loop and is arranged around the periphery of the central region. There are gaps between the conductive trace and the bonding point at the innermost ring of the peripheral region and the bonding point at the outermost ring of the central region. The conductive trace has a notch, forming a first free end and a second free end; the lead includes a first lead and a second lead, and the impedance measuring point includes a first impedance measuring point and a second impedance measuring point; one end of the first lead is electrically connected to the first free end, and the other end of the first lead is electrically connected to the first impedance measuring point; one end of the first lead is electrically connected to the first free end, and the other end of the first lead is electrically connected to the first impedance measuring point.

3. The display module as described in claim 2, characterized in that, The central region includes the bonding points located in the middle row of the output pad region; or, The central region includes at least a portion of the bonding points located in the middle column of the output pad region; The shape formed by the conductive traces surrounding the central region is one of a rectangle, triangle, trapezoid, or irregular polygon.

4. The display module as described in claim 2, characterized in that, The peripheral region is composed of the outermost bonding points of the output pad region, and the central region is composed of the remaining bonding points.

5. The display module as described in claim 1, characterized in that, The center bonding point is located at the center of the output pad area, and the central area is the center bonding point; one end of the conductive trace is electrically connected to the center bonding point, and the other end of the conductive trace extends out of the output pad area and is electrically connected to the lead.

6. The display module as described in claim 1, characterized in that, The conductive traces and the impedance measurement points are arranged in a staggered manner. A line-changing hole is provided on the display substrate around the output pad area. One end of the lead is electrically connected to a free end of the conductive trace, and the other end of the lead passes through the line-changing hole and is electrically connected to the impedance measurement point.

7. A method for detecting a display module, characterized in that, The method for detecting the impedance of a display module as described in any one of claims 1 to 6 includes the following steps: The display module, which has undergone impedance detection preprocessing, is placed on the testing platform; Impedance detection is performed on the output pad area of ​​the display module; After the host obtains the impedance value measured at the impedance measurement point, it determines whether there is photoresist peeling in the output pad area based on the change of the impedance value.

8. The method for detecting a display module as described in claim 7, characterized in that, Before placing the display module, which has undergone impedance detection preprocessing, on the testing stage, the process further includes a step of performing impedance detection preprocessing on the display module in the TP process section. This impedance detection preprocessing step includes the following sub-steps: After depositing and forming a metal thin film layer in the output pad area of ​​the display substrate, photoresist is coated. The output pad area is exposed and developed to form a metal patterned adhesive layer for the conductive traces. The metal circuit pattern of the conductive trace is formed by metal etching and subsequent processing of the output pad area.

9. The method for detecting a display module as described in claim 7, characterized in that, The step of performing impedance detection on the output pad area of ​​the display module includes the following sub-steps: The probe of the detection device is in electrical contact with the impedance measurement point; The detection device acquires the impedance value of the impedance measurement point; The detection device transmits the impedance value to the host computer; The step of determining whether there is photoresist peeling in the output pad area based on the change in impedance value includes the following steps: The host compares the acquired impedance value with a pre-stored preset threshold. If the impedance value is greater than the preset threshold, it is determined that there is a problem of photoresist peeling in the output pad area; If the impedance value is equal to or less than the preset threshold, it is determined that there is no photoresist peeling in the output pad area.

10. A display device, characterized in that, Includes the display module as described in any one of claims 1 to 9.

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