Flexible circuit board and display device

Abstract

The invention discloses a flexible circuit board and a display device. The flexible circuit board comprises a circuit board body, wherein the circuit board body comprises a first area and a second area surrounding the first area; the first devices and the glue thickness reference structures are located on the same side of the circuit board body, at least part of the first devices are welded to the first area, and at least part of the glue thickness reference structures are located in the second area; along a first direction, the height of the glue thickness reference structure is greater than that of the first device, and the first direction is perpendicular to a plane where the circuit board body is located; and the insulating rubber layer is arranged on the same side with the first device, the insulating rubber layer is located in the first region and the second region, and the insulating rubber layer covers the first device. By adopting the scheme, the adhesive thickness of the circuit board can be evaluated without destructively slicing the flexible circuit board, so that the adhesive thickness measurement difficulty of the flexible circuit board is reduced, the test cost of the flexible circuit board is reduced, and the test efficiency of the flexible circuit board is improved.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of display technology, and in particular, to a flexible printed circuit board and a display device. Background Art

[0002] Each device (such as capacitors, resistors, and diodes) on a flexible printed circuit board (FPC) is located in a device area. For waterproofing requirements, the device area needs to be sealed with glue. The glue sealing process generally involves coating an insulating glue above and around the device to protect the device. The thickness of the insulating glue on the upper surface of the device determines the waterproof effect of the product. Therefore, it is necessary to measure the glue thickness above the device in the flexible printed circuit board and evaluate the waterproof performance based on the glue thickness. However, in the prior art, the glue thickness measurement scheme for flexible printed circuit boards has a high cost and low test efficiency. Summary of the Invention

[0003] In view of this, the present invention provides a flexible printed circuit board and a display device to reduce the test cost of the flexible printed circuit board and improve the test efficiency of the flexible circuit board.

[0004] In a first aspect, the present invention provides a flexible printed circuit board, comprising:

[0005] A circuit board body, the circuit board body comprising a first area and a second area surrounding the first area;

[0006] A plurality of first devices and a plurality of glue thickness reference structures located on the same side of the circuit board body, at least part of the first devices being soldered to the first area, and at least part of the glue thickness reference structures being located in the second area; along a first direction, the height of the glue thickness reference structure is greater than the height of the first device, and the first direction is perpendicular to the plane of the circuit board body;

[0007] An insulating glue layer, disposed on the same side as the first device, the insulating glue layer being located in the first area and the second area, and the insulating glue layer covering the first device.

[0008] In a second aspect, the present invention provides a display device comprising the flexible printed circuit board according to the first aspect of the present invention.

[0009] The flexible printed circuit board provided by the present invention sets the first device and the glue thickness reference structure on the same side of the circuit board body, and arranges the glue thickness reference structure with a higher height in the edge area of the circuit board body and the first device with a smaller height in the central area of the circuit board body. It is possible to evaluate the glue thickness of the circuit board without performing destructive slicing on the flexible printed circuit board, which is beneficial to reducing the difficulty of measuring the glue thickness of the flexible printed circuit board, reducing the test cost of the flexible printed circuit board, and improving the test efficiency of the flexible printed circuit board. Description of the Drawings

[0010] Figure 1 Schematic structural diagram of a flexible printed circuit board provided by an embodiment of the present invention;

[0011] Figure 2 is Figure 1 Schematic cross-sectional structure diagram along A-A';

[0012] Figure 3 Schematic structural diagram of another flexible printed circuit board provided by an embodiment of the present invention;

[0013] Figure 4 Schematic structural diagram of yet another flexible printed circuit board provided by an embodiment of the present invention;

[0014] Figure 5 is Figure 4 Schematic cross-sectional structure diagram along the B-B' direction;

[0015] Figure 6 Schematic cross-sectional structure diagram of a flexible printed circuit board provided by an embodiment of the present invention;

[0016] Figure 7 Schematic structural diagram of still another flexible printed circuit board provided by an embodiment of the present invention;

[0017] Figure 8 is Figure 7 Schematic cross-sectional structure diagram along the C-C' direction;

[0018] Figure 9 Schematic cross-sectional structure diagram of another flexible printed circuit board provided by an embodiment of the present invention;

[0019] Figure 10 Schematic cross-sectional structure diagram of yet another flexible printed circuit board provided by an embodiment of the present invention;

[0020] Figure 11 is Figure 1 Schematic cross-sectional structure diagram along the D-D' direction;

[0021] Figure 12 Schematic structural diagram of yet another flexible printed circuit board provided by an embodiment of the present invention;

[0022] Figure 13 Schematic structural diagram of a display device provided by an embodiment of the present invention. Detailed implementation manners

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings, rather than all the structures.

[0024] It should be noted that the terms "having", "including", "comprising", etc. described in this application all have an open meaning. That is, when it is described that a module "has", "includes", or "comprises" a first element, a second element, and / or a third element, it means that the module includes other elements in addition to the first element, the second element, and / or the third element. In addition, the ordinal numbers such as "first", "second", and "third" in this application are not intended to limit the specific order, but only to distinguish each part. In this application, when it is described that layer A and layer B are "set on the same layer", it means that layer A and layer B are made of the same material and process.

[0025] For the existing flexible printed circuit board, generally, for glue thickness measurement, each device on the flexible printed circuit board needs to be sliced. After slicing is completed, it is magnified by an electron microscope and then the glue thickness above each device is measured. However, the inventor found that with the above solution, since the flexible printed circuit board product needs to be sliced and damaged, full inspection of the product cannot be achieved, and defective products will flow out; and the test efficiency of measuring after slicing each device is low, and the test cost is high.

[0026] In view of this, the present invention provides a flexible printed circuit board, including:

[0027] A circuit board body, the circuit board body includes a first area and a second area surrounding the first area;

[0028] A plurality of first devices and a plurality of glue thickness reference structures on the same side of the circuit board body. At least part of the first devices are soldered to the first area, and at least part of the glue thickness reference structures are located in the second area; along a first direction, the height of the glue thickness reference structure is greater than the height of the first device, and the first direction is perpendicular to the plane where the circuit board body is located;

[0029] An insulating glue layer, arranged on the same side as the first device, the insulating glue layer is located in the first area and the second area, and the insulating glue layer covers the first device.

[0030] Through the above solution, it is possible to evaluate the glue thickness of the circuit board without performing destructive slicing on the flexible printed circuit board, which is beneficial to reducing the difficulty of glue thickness measurement of the flexible printed circuit board, reducing the test cost of the flexible printed circuit board, and improving the test efficiency of the flexible printed circuit board.

[0031] The above is the core idea of the present invention. Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] The flexible printed circuit board provided by the embodiment of the present invention can be used in the display field and form a display device after being bonded to a display panel. Figure 1A schematic structural diagram of a flexible printed circuit board provided by an embodiment of the present invention Figure 2 is Figure 1 a schematic cross-sectional structure along A-A', refer to Figure 1 and Figure 2 , in the embodiment of the present invention, the flexible printed circuit board includes: a circuit board body 10, the circuit board body 10 includes a first area A1 and a second area A2 surrounding the first area A1; a plurality of first devices 20 and a plurality of glue thickness reference structures 30 located on the same side of the circuit board body 10, at least part of the first devices 20 are soldered to the first area A1, and at least part of the glue thickness reference structures 30 are located in the second area A2; along the first direction X, the height of the glue thickness reference structure 30 is greater than the height of the first device 20, and the first direction X is perpendicular to the plane where the circuit board body 10 is located; an insulating glue layer 40, arranged on the same side as the first device 20, the insulating glue layer 40 is located in the first area A1 and the second area A2, and the insulating glue layer 40 covers the first device 20.

[0033] The circuit board body 10 refers to the main substrate structure of the flexible printed circuit board, etc., which can provide the circuits required for the conduction of the printed circuit board. The specific structure of the circuit board body 10 is not limited, and those skilled in the art can set it according to actual needs. The circuit board body 10 should have the characteristics of high reliability, high wiring density, light weight, thin thickness, and good bendability.

[0034] Optionally, Figure 3 a schematic structural diagram of another flexible printed circuit board provided by an embodiment of the present invention, refer to Figure 3 , in a possible embodiment, the circuit board body 10 may include a base material layer 101, a cover film 102, and a functional layer 103 arranged in a stacked manner; the base material layer 101 is soldered to the first device 20, the cover film 102 is located on the side of the base material layer 101 away from the first device 20, and the functional layer 103 is located on the side of the cover film 102 away from the base material layer 101.

[0035] Exemplarily, the base material layer 101 may be a flexible copper clad laminate (FCCL), which may be formed by laminating a copper foil 1011 and a first insulating film 1012, and is used to provide the circuits required for the conduction of the printed circuit board. The first insulating film 1012 includes, but is not limited to, polyimide film (PI), polyester film (PET), etc., and the embodiment of the present invention does not limit this. Figure 3 Exemplarily, two layers of copper foil 1011 and one layer of first insulating film 1012 between the two layers of copper foil 1011 are shown to form a double-sided copper clad laminate, but the actual situation is not limited to this.

[0036] Continue to refer to Figure 3, The cover film 102 can cover one side surface of the circuit board body 10 where the first device 20 is not provided. The cover film 102 functions as a solder mask insulation to prevent oxidation of the copper foil 1011 and protect the base material layer 101. Exemplarily, the cover film 102 may include a second insulating film 1021 and an adhesive layer 1022. The adhesive layer 1022 is located between the base material layer 101 and the second insulating film 1021 and is used to bond and fix the cover film 102 to the base material layer 101.

[0037] One side surface of the cover film 102 facing away from the base material layer 101 may further include a functional layer 103. The functional layer 103 is bonded and fixed to the cover film 102, for example, by an adhesive (not shown in the figure). The functional layer 103 includes, but is not limited to, a shielding layer and a reinforcing layer, etc. The shielding layer can play an electromagnetic shielding role to protect the flexible circuit board from external electromagnetic interference; the reinforcing layer can play a role in increasing the mechanical strength of the flexible circuit board and provide better support for the circuit board body 10.

[0038] Of course, in actual application, the film layer structure of the circuit board body 10 is not limited to this, and those skilled in the art can increase or decrease the film layer structure according to actual needs.

[0039] Further, continuing to refer to Figures 1 to 3 , the circuit board body 10 includes a first area A1 and a second area A2. The second area A2 surrounds the first area A1. The first area A1 can be the central area of the flexible circuit board, and the second area A2 can be the edge area of the flexible circuit board. The first area A1 is used to arrange a plurality of first devices 20. The first devices 20 can be soldered to the surface of the circuit board body 10 through a conductive connection structure 50 such as solder paste, so as to be electrically connected to the internal conductive circuit of the circuit board body 10. The first devices 20 include electronic devices required to complete the functions of the circuit board, including, but not limited to, at least one of transistors, diodes, capacitors, resistors, and driving chips, etc. The type of the first devices 20 can be set according to actual needs and will not be specifically limited here.

[0040] A plurality of glue thickness reference structures 30 are arranged in the second area A2. The glue thickness reference structure 30 refers to any structure with a certain height, which can be an electronic device or an insulating glue column, etc., but is not limited to this. The glue thickness reference structure 30 and the first devices 20 are located on the same side surface of the circuit board body 10. Exemplarily, the circuit board body 10 may include a first surface 10A and a second surface 10B that are oppositely arranged along its thickness direction (i.e., the first direction X). For Figure 3 the circuit board body 10 shown, the first surface 10A can refer to the side surface of the base material layer 101 facing away from the cover film 102, and the second surface 10B can refer to the side surface of the functional layer 103 facing away from the cover film 102. The glue thickness reference structure 30 and the first devices 20 can be located on the first surface 10A.

[0041] Since the second area A2 surrounds the first area A1, the distance between the glue thickness reference structure 30 arranged in the second area A2 and the edge of the circuit board body 10 is smaller than the distance between the first device 20 in the first area A1 and the edge of the circuit board body 10, that is, compared with the first device 20, at least part of the glue thickness reference structure 30 is closer to the edge of the circuit board body 10.

[0042] Continue to refer Figure 1 and Figure 2 , the insulating adhesive layer 40 can be arranged on one side of the first surface 10A of the flexible circuit board, and the insulating adhesive layer 40 covers part of the first surface 10A of the circuit board body 10 (the area where the first device 20 and the adhesive thickness reference structure 30 are not arranged), the first device 20 and at least part of the adhesive thickness reference structure 30. The insulating adhesive layer 40 is the sealing adhesive of the flexible circuit board, which is used to protect the devices in the flexible circuit board to prevent external impurities such as water vapor from affecting the electrical performance of the devices. In order to clearly show the first device 20 and the adhesive thickness reference structure 30, Figure 1 The insulating glue layer 40 is not shown in the top view.

[0043] Among them, it is worth mentioning that Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the height of the glue thickness reference structure 30 along the first direction X can be set to be greater than the height of the first device 20 along the first direction X. Under this setting mode, when preparing the insulating glue layer 40, the thickness of the insulating glue layer 40 above the first device 20 (the side away from the circuit board body 10) is greater than the thickness of the insulating glue layer 40 above the glue thickness reference structure 30 (the side away from the circuit board body 10). In this way, the upper surface of the glue thickness reference structure 30 with a higher height can form a glue thickness height reference surface, and the overall glue thickness of the flexible circuit board is evaluated with the thickness of the insulating glue layer 40 at the glue thickness reference structure 30 as a reference, so as to determine whether the glue thickness meets the actual requirements of the circuit board. When the thickness of the insulating glue layer 40 at the glue thickness reference structure 30 (also referred to as "glue thickness") meets the glue thickness requirement, the thickness of the insulating glue layer 40 at the first device 20 must meet the thicker requirement.

[0044] In addition, since the glue thickness reference structure 30 with a relatively high height is arranged at the edge of the circuit board body 10, the glue thickness at the glue thickness reference structure 30 can be determined without destructively slicing the flexible circuit board. After evaluating the glue thickness of the flexible circuit board, the flexible circuit board can still be used, which is conducive to reducing the difficulty of measuring the glue thickness of the flexible circuit board, reducing the testing cost of the flexible circuit board, and improving the testing efficiency of the flexible circuit board. In addition, since there is no need to destroy the flexible circuit board, the flexible circuit board can be tested in large quantities to avoid the outflow of defective products.

[0045] Among them, the type, quantity, and specific layout position of the glue thickness reference structure can be set according to actual requirements, which are not limited in the embodiments of the present invention. Any design solution of the glue thickness reference structure that meets the application requirements is within the scope of the technical solutions protected by the embodiments of the present invention.

[0046] The flexible printed circuit board provided by the embodiments of the present invention sets a first device and a glue thickness reference structure on the same side of the circuit board body, and arranges the glue thickness reference structure with a higher height in the edge area of the circuit board body and the first device with a smaller height in the central area of the circuit board body. It is possible to evaluate the glue thickness of the circuit board without performing destructive slicing on the flexible printed circuit board, which is beneficial to reducing the difficulty of measuring the glue thickness of the flexible printed circuit board, reducing the test cost of the flexible printed circuit board, and improving the test efficiency of the flexible printed circuit board.

[0047] Optionally, reference may continue to be made to Figure 1 and Figure 2 , in a possible embodiment, the insulating glue layer 40 also covers the glue thickness reference structure 30, and the surface of the insulating glue layer 40 facing away from the circuit board body 10 is a flat surface.

[0048] As an alternative embodiment, the insulating glue layer 40 also covers the surface of the glue thickness reference structure 30 facing away from the circuit board body 10. In other words, the insulating glue layer 40 covers the first device 20 and the glue thickness reference structure 30, and the insulating glue layer 40 can also protect the glue thickness reference structure 30, thereby improving the packaging reliability of the flexible printed circuit board. At this time, the surface of the insulating glue layer 40 facing away from the circuit board body 10 is a flat surface, which is beneficial to improving the flatness of the flexible printed circuit board.

[0049] Optionally, as shown in Figure 1 and Figure 2 , in a possible embodiment, the flexible printed circuit board further includes an insulating glue paper 60, and the insulating glue paper 60 covers the insulating glue layer 40.

[0050] In this embodiment, an insulating glue paper 60 can be provided on the side of the insulating glue layer 40 facing away from the circuit board body 10, and the insulating glue paper 60 is fixedly attached to the surface of the insulating glue layer 40 facing away from the circuit board body 10. After fixing the first device 20 and the glue thickness reference structure 30 on the first surface 10A of the circuit board body 10, an insulating glue layer 40 is coated on the first surface 10A, and then the insulating glue paper 60 is placed on the upper surface of the insulating glue layer 40, and the insulating glue paper 60 is used to press the glue to ensure the flatness of the insulating glue layer 40. The presence of the insulating glue paper 60 can also better protect the flexible printed circuit board.

[0051] It should be noted that in the drawings of the embodiments of the present invention, the flexible printed circuit board including the insulating glue paper 60 is taken as an example for introduction, and it is not limited that the flexible printed circuit board must include this structure.

[0052] Exemplarily, reference can continue to be made to Figure 1 and Figure 2 , in some embodiments, the glue thickness reference structure 30 includes a second device 31, the second device 31 is soldered to the second area A2, and the second device 31 and the first device 20 are respectively electrically connected to the conductive lines in the circuit board body 10; along the first direction X, the insulating glue layer 40 covering the first device 20 has a first thickness d1, and the insulating glue layer 40 covering the second device 31 has a second thickness d2; d0 ≤ d2 < d1, where d0 is the preset insulating glue thickness of the device.

[0053] In this embodiment, the glue thickness reference structure 30 includes a second device 31, and the second device 31 can be soldered to the first surface 10A of the circuit board body 10 through a conductive connection structure 50 such as solder paste, so as to be electrically connected to the internal conductive lines of the circuit board body 10. The height of the second device 31 is greater than the height of the first device 20. The second device 31 can be an electronic device such as a transistor, a diode, a capacitor, a resistor, or a driving chip. Both the second device 31 and the first device 20 have electrical properties, and they jointly complete the circuit board function.

[0054] Using the second device 31 with electrical properties as the glue thickness reference structure 30, devices with a higher height in the flexible circuit board can be arranged in the second area A2 and used as the second device 31, and devices with a lower height can be arranged in the first area A1 and used as the first device 20, without the need to additionally add a glue thickness reference structure 30, and the size of the flexible circuit board can remain unchanged.

[0055] The insulating glue layer 40 covers the first device 20 and the second device 31. The side surface of the plurality of second devices 31 facing away from the circuit board body 10 forms a glue thickness height reference surface, and the side surface of the second device 31 facing away from the circuit board body 10 can also be used as a support surface for pressing the insulating glue paper 60. As Figure 2 shown, the glue thickness above the first device 20 is the first thickness d1, and the thickness above the second device 31 is the second thickness d2. The first thickness d1 and the second thickness d2 satisfy: d0 ≤ d2 < d1. The preset insulating glue thickness d0 of the device refers to the minimum insulating glue layer thickness that meets the application requirements (such as meeting the waterproof requirements), that is, the insulating glue layer thickness required by the flexible circuit board specification. Since the second device 31 has electrical properties, the glue thickness (second thickness d2) above the second device 31 needs to be greater than or equal to the preset insulating glue thickness d0 of the device; and the height of the second device 31 is greater than the height of the first device 20, so the glue thickness (first thickness d1) above the first device 20 is greater than the glue thickness above the second device 31. Such a setting can ensure that the insulating glue layer 40 above the first device 20 and the second device 31 meets the circuit board specification requirements.

[0056] It should be noted that in the embodiments of the present invention, since the height of the conductive connection structure 50 is very small, the height h2 of the first device 20 can be regarded as the sum of the height h21 of the first device 20 itself and the height h22 of the conductive connection structure 50, that is, h2 = (h21 + h22); the height h5 of the second device 31 can be regarded as the sum of the height h51 of the second device 31 itself and the height h22 of the conductive connection structure 50, that is, h5 = (h51 + h22). In the flexible printed circuit board, the height h21 of the first device 20 itself, the height h51 of the second device 31 itself, the height h22 of the conductive connection structure 50, and the thickness d6 of the insulating adhesive tape 60 (i.e., the height along the first direction X) are all known quantities, and the thickness d7 of the circuit board body 10 and the total thickness d8 of the flexible printed circuit board can be measured. Refer to Figure 2 , according to the positional relationship, the second thickness d2 of the insulating adhesive layer 40 above the second device 31 satisfies: d2 = (d8 - d7 - d6 - h5) = (d8 - d7 - d6 - h51 - h22); the first thickness d1 of the insulating adhesive layer 40 above the first device 20 satisfies: d1 = (d2 + h5 - h2). In this way, the quantitative measurement of the adhesive thickness above the first device 20 and the second device 31 can be realized, and then whether the printed circuit board meets the specification requirements can be judged according to the adhesive thickness above the second device 31 and the height difference between the second device 31 and the first device 20.

[0057] The embodiments of the present invention do not limit the specific value of the preset insulating adhesive thickness d0 of the device, and those skilled in the art can set it according to actual needs. Exemplarily, in some embodiments, 0.05 mm ≤ d0 can be set, for example, d0 = 0.05 mm or d0 = 0.1 mm, but not limited thereto.

[0058] Figure 4 is a schematic structural diagram of another flexible printed circuit board provided by the embodiments of the present invention, Figure 5 is Figure 4 a schematic cross-sectional structure diagram along the B - B' direction, and reference can be made to Figure 4 and Figure 5 , in a possible embodiment, the adhesive thickness reference structure 30 further includes a first insulating column 32, and the first insulating column 32 is located on the surface of the second device 31 facing away from the circuit board body 10; the insulating adhesive layer 40 covers the second device 31 and the first insulating column 32; along the first direction X, the first insulating column 32 has a first height h1, and d0 ≤ h1.

[0059] Figure 4 The shown embodiment is in Figure 2Based on the shown embodiments, improvements can be made. Specifically, a first insulating column 32 can be added to the side of the second device 31 facing away from the circuit board body 10, and the first insulating column 32 is arranged on the side of the second device 31 facing away from the circuit board body 10. In this setting, the surface of the first insulating column 32 facing away from the second device 31 forms a reference surface for the glue thickness height, and at the same time can be used as a support surface for pressing the insulating adhesive tape 60. Figure 4 It is shown in Figure 4 that the first insulating columns 32 and the second devices 31 are arranged in a one-to-one correspondence. In fact, it is not limited to this. In other embodiments of the present invention, multiple first insulating columns 32 can be arranged above one second device 31, so as to improve the flatness of the reference surface for the glue thickness height.

[0060] Among them, in this embodiment, it is defined that the first height h1 of the first insulating column 32 is greater than or equal to the preset insulating glue thickness d0 of the device. Since the insulating glue layer 40 covers the first insulating column 32, the thickness d2 of the insulating glue layer 40 above the second device 31 is greater than or equal to the height h1 of the first insulating column 32. In this way, in the process of coating the insulating glue layer 40, the first insulating column 32 can be used as a reference for glue coating. Controlling the upper surface of the insulating glue layer 40 to be flush with or exceed the upper surface of the first insulating column 32 can ensure that the glue thickness above the second device 31 reaches the preset insulating glue thickness d0 of the device. When the glue thickness above the second device 31 reaches the preset insulating glue thickness d0 of the device, the glue thickness above the first device 20 will surely reach the preset insulating glue thickness d0 of the device, thus ensuring that the glue thickness of the flexible circuit board meets the application requirements.

[0061] In this embodiment, the first insulating column 32 can be made according to the actual application requirements of the flexible circuit board. For example, if the specification requires that the glue thickness on the device is greater than or equal to 0.1 mm, that is, the preset insulating glue thickness d0 of the device is 0.1 mm, then the first insulating column 32 with a first height h1 of 0.1 mm can be made. According to this scheme, the thickness of the insulating glue layer 40 above all devices after glue coating and pressing is greater than or equal to 0.1 mm.

[0062] Among them, the embodiments of the present invention do not limit the shape, size, etc. of the first insulating column 32. Figure 4 and Figure 5 exemplarily shows that the first insulating column 32 is cylindrical, but in fact it is not limited to this. In addition, the material of the first insulating column 32 can be selected according to actual needs, and the embodiments of the present invention do not limit this either.

[0063] Optionally, Figure 6 is a schematic cross-sectional structure diagram of a flexible circuit board provided by an embodiment of the present invention. Figure 6 It can be regarded as Figure 1 another schematic cross-sectional structure diagram of the shown flexible circuit board along the A-A' direction, which can be referred to Figure 6, in a possible embodiment, the glue thickness reference structure 30 includes a third device 33. The third device 33 is soldered to the second area A2. The third device 33 is electrically insulated from the conductive circuit in the circuit board body 10, and the first device 20 is electrically connected to the conductive circuit. Along the first direction X, the insulating glue layer 40 covering the first device 20 has a first thickness d1, and the insulating glue layer 40 covering the third device 33 has a third thickness d3, where 0 < d3 < d1.

[0064] As Figure 6 shown, in this embodiment, the glue thickness reference structure 30 may be the third device 33. The third device 33 may be soldered to the first surface 10A of the circuit board body 10 through a conductive connection structure 50 such as solder paste. The height of the third device 33 is greater than the height of the first device 20. The second device 31 may be an electronic device such as a transistor, a diode, a capacitor, a resistor, or a driving chip. The difference between the third device 33 and the second device 31 in the above embodiment is that the third device 33 is not electrically connected to the conductive circuit in the circuit board body 10, that is, the third device 33 is a dummy device, which does not need to transmit electrical signals, does not have electrical properties, and does not need to perform the corresponding functions that the flexible circuit board needs to perform. The third device 33 only serves as a height reference. The upper surfaces of multiple third devices 33 form a glue thickness height reference surface, which can be used as a support surface when the insulating glue paper 60 is pressed with glue.

[0065] Since the third device 33 does not play a role in transmitting signals, the coverage of the insulating glue layer 40 on the third device 33 does not need to be strictly controlled. In this embodiment, the thickness d3 of the insulating glue layer 40 above the third device 33 can be set to be greater than 0.

[0066] Among them, the height h3 of the third device 33 can be regarded as the sum of the height h31 of the third device 33 itself and the height h22 of the conductive connection structure 50, that is, h3 = (h31 + h22). According to the positional relationship, the thickness d3 of the insulating glue layer 40 above the third device 33 satisfies: d3 = (d8 - d7 - d6 - h3) = (d8 - d7 - d6 - h31 - h22). The parameters represented by d6, d7, and d8 are the same as those in the above embodiment, and will not be elaborated here and below; the thickness d1 of the insulating glue layer 40 above the first device 20 satisfies: d1 = (d3 + h3 - h2). Since h3 is greater than h2, d1 should be greater than d3. The solution in this embodiment can also achieve the quantitative measurement of the glue thickness above the first device 20.

[0067] Use the third device 33 with non-electric properties as the glue thickness reference structure 30, and set the insulating glue layer 40 to cover the third device 33, which can ensure the glue thickness of the insulating glue layer 40 above the first device 20 with lower height and electric properties. In addition, since the third device 33 is also an electronic device, after the insulating glue layer 40 is coated, the covering condition (such as flatness and other parameters) of the insulating glue layer 40 above the third device 33 is similar to that of the first device 20, which is beneficial to ensuring the overall flatness of the insulating glue layer 40.

[0068] Optionally, continue to refer to Figure 6 , along the first direction X, the first device 20 has a second height h2, and the third device 33 has a third height h3; (h3 - h2) ≥ d0, where d0 is the preset insulating glue thickness of the device.

[0069] The height difference between the third device 33 and the first device 20 is (h3 - h2), and the height difference between the two corresponds to the glue thickness difference above. In this embodiment, the height difference between the third device 33 and the first device 20 can be limited to be greater than or equal to the preset insulating glue thickness d0 of the device. In this way, the glue thickness difference above the third device 33 and on the first device 20 is greater than or equal to the preset insulating glue thickness d0 of the device. d1 = (h3 - h2 + d3), ensuring that d1 is greater than d0, and the glue thickness above the first device 20 meets the requirements of the circuit board specifications. In this way, the circuit board can be judged whether it meets the specification requirements according to the height difference between the second device 31 and the first device 20, without measuring the dimensions of each component in the flexible circuit board.

[0070] Optionally, when preparing the flexible circuit board, the selection specifications of the third device 33 and the first device 20 in the flexible circuit board can be determined according to the preset insulating glue thickness d0 of the device. Exemplarily, assuming that the preset insulating glue thickness d0 of the device is 0.05 mm, an electronic device with a height of 0.7 mm can be selected as the third device 33, and an electronic device with a height less than or equal to 0.65 mm can be selected as the first device 20. According to this rule, the glue thickness above all the first devices 20 in the final flexible circuit board meets the requirement of being greater than 0.05 mm.

[0071] Figure 7 This is a schematic structural diagram of another flexible circuit board provided by an embodiment of the present invention. Figure 8 For Figure 7 The cross-sectional structural diagram along the C-C' direction. Optionally, refer to Figure 7 And Figure 8 , in a possible embodiment, the glue thickness reference structure 30 includes a second insulating column 34. Along the first direction X, one side of the second insulating column 34 is in contact with the circuit board body 10, and the other side is in contact with the insulating glue layer 40; along the first direction X, the insulating glue layer 40 covering the first device 20 has a first thickness d1, and the insulating glue layer 40 covering the second insulating column 34 has a fourth thickness d4, where 0 < d4 < d1.

[0072] As Figure 7 and Figure 8 shown, in this embodiment, the third device 33 in the above Figure 6 shown embodiment can be replaced with the second insulating post 34, and the second insulating post 34 is used as the glue thickness reference structure 30. The second insulating post 34 is fixed on the first surface 10A of the circuit board body 10 and is located in the second area A2. The upper surfaces of a plurality of second insulating posts 34 form a glue thickness height reference surface and can be used as a supporting surface for pressing the insulating adhesive tape 60, and the insulating adhesive layer 40 covers the first device 20 and the second insulating post 34.

[0073] Among them, the second insulating post 34 has no electrical property, and the thickness of the insulating adhesive layer 40 above it does not need to be strictly controlled. The thickness of the insulating adhesive layer 40 above the second insulating post 34 can be set to be greater than 0. In this setting method, the thickness d4 of the insulating adhesive layer 40 above the second insulating post 34 satisfies: d4 = (d8 - d7 - d6 - h4), where h4 is the height of the second insulating post 34 along the first direction X; the thickness d1 of the insulating adhesive layer 40 above the first device 20 satisfies: d1 = (d4 + h4 - h2), h4 - h2 is greater than 0, and d1 is greater than d4.

[0074] Among them, the embodiments of the present invention do not limit the shape, size, etc. of the second insulating post 34, Figure 7 and Figure 8 exemplarily shows that the second insulating post 34 is cylindrical, but it is not limited thereto in reality. The material of the second insulating post 34 can be the same as or different from the material of the first insulating post 32, and the embodiments of the present invention also do not limit this. The second insulating post 34 can be prepared before the first device 20 is welded. In this way, the second insulating post 34 can also function as a positioning post to facilitate the layout of the first device 20.

[0075] Further optionally, continuing to refer to Figure 7 and Figure 8 , along the first direction X, the first device 20 has a second height h2, and the second insulating post 34 has a third height h4; (h4 - h2) ≥ d0, where d0 is the preset insulating glue thickness of the device.

[0076] Similar to the above Figure 6 shown embodiment, the height difference between the second insulating post 34 and the first device 20 is (h4 - h2), and the height difference between the two corresponds to the glue thickness difference above. In this embodiment, the height difference between the second insulating post 34 and the first device 20 can be limited to be greater than or equal to the preset insulating glue thickness d0 of the device. In this way, the glue thickness difference above the second insulating post 34 and on the first device 20 is greater than or equal to the preset insulating glue thickness d0 of the device. d1 = (d4 + h4 - h2), ensuring that d1 is greater than d0, and the glue thickness above the first device 20 meets the circuit board specification requirements. In this way, it can be judged whether the circuit board meets the specification requirements according to the height difference between the second insulating post 34 and the first device 20.

[0077] Exemplarily, assume that the preset thickness of the insulating adhesive of the device is 0.05 mm. Then, the height of the second insulating column 34 is set to 0.7 mm, and the height of the first device 20 is less than or equal to 0.65 mm. According to this rule, the thickness of the adhesive above all the first devices 20 in the final flexible printed circuit board meets the requirement of being greater than 0.05 mm.

[0078] Optionally, Figure 9 Another cross-sectional structure diagram of the flexible printed circuit board provided by the embodiment of the present invention can be referred to Figure 9 , Figure 10 Another cross-sectional structure diagram of the flexible printed circuit board provided by the embodiment of the present invention, refer to Figure 9 and Figure 10 In some other embodiments, the insulating adhesive layer 40 covers the side surface of the adhesive thickness reference structure 30, and the surface of the insulating adhesive layer 40 facing away from the circuit board body 10 is flush with the surface of the adhesive thickness reference structure 30 facing away from the circuit board body 10.

[0079] As Figure 9 and Figure 10 shown, in some embodiments of the present invention, the insulating adhesive layer 40 covers the side surfaces of the first device 20 and the adhesive thickness reference structure 30. Along the first direction X, the adhesive thickness reference structure 30 does not overlap with the insulating adhesive layer 40, that is, the upper surface of the adhesive thickness reference structure 30 is not covered by the insulating adhesive layer 40. The surface of the insulating adhesive layer 40 facing away from the circuit board body 10 is flush with the surface of the adhesive thickness reference structure 30 facing away from the circuit board body 10. In other words, the upper surface of the insulating adhesive layer 40 is connected to the upper surface of the adhesive thickness reference structure 30 to form a flat surface. When there is an insulating adhesive paper 60, the insulating adhesive paper 60 is attached to the upper surfaces of the insulating adhesive layer 40 and the adhesive thickness reference structure 30.

[0080] In this setting mode, along the first direction X, the thickness of the insulating adhesive layer 40 above the first device 20 is the height difference between the first device 20 and the adhesive thickness reference structure 30. When preparing the flexible printed circuit board, the height difference between the first device 20 and the adhesive thickness reference structure 30 should be greater than or equal to the preset insulating adhesive thickness d0 of the device. In this way, during the subsequent testing of the flexible printed circuit board, according to the height difference between the adhesive thickness reference structure 30 and the first device 20 being the adhesive thickness above the first device 20, the compliance of the adhesive thickness can be directly determined by comparing the heights of the adhesive thickness reference structure 30 and the first device 20.

[0081] In addition, it should be noted that for the solution where the insulating adhesive layer 40 only covers the adhesive thickness reference structure 30, the adhesive thickness reference structure 30 should not have electrical properties. For example, it can be the above-mentioned third device 33 or the second insulating column 34. Exemplarily, Figure 9 in the shown embodiment, the adhesive thickness reference structure 30 can include the third device 33; in Figure 10In the illustrated embodiment, the glue thickness reference structure 30 may include a second insulating post 34.

[0082] Optionally, Figure 11 For Figure 1 a schematic cross-sectional structure diagram along the D-D' direction, reference may be made to Figure 1 and Figure 1 , in a possible embodiment, the heights of a plurality of glue thickness reference structures 30 located in the second region A2 are equal in the first direction X.

[0083] By setting the heights of the plurality of glue thickness reference structures 30 to be the same, the flatness of the glue thickness height reference plane formed by the plurality of glue thickness reference structures 30 can be ensured, and errors in glue thickness measurement above the first device 20 caused by different heights of the glue thickness reference structures 30 can be avoided.

[0084] Optionally, reference may continue to be made to Figure 1 , Figure 4 and Figure 7 , in a possible embodiment, the connection lines of the orthographic projections of the plurality of glue thickness reference structures 30 on the plane where the circuit board body 10 is located form a virtual closed figure, and the orthographic projection of the first device 20 on the plane where the circuit board body 10 is located is located inside the virtual closed figure.

[0085] The dotted rectangular frame in the figure represents the connection lines of the orthographic projections of the plurality of glue thickness reference structures 30 on the plane where the circuit board body 10 is located. As shown in Figure 1 , Figure 4 and Figure 7 shown, as an optional solution, a relatively large number of glue thickness reference structures 30 may be provided in the second region A2, so that the glue thickness reference structures 30 can surround all the first devices 20, and the first devices 20 are located inside the region surrounded by the glue thickness reference structures 30. For example, as shown in the figure, the glue thickness reference structures 30 are evenly distributed in the second region A2 of the circuit board body 10. In this way, it is beneficial to further improve the flatness of the glue thickness height reference plane, and further improve the flatness of the insulating glue layer 40.

[0086] In the drawings of the embodiments of the present invention, a rectangular flexible circuit board is taken as an example, but it is not limited thereto in reality. For a rectangular flexible circuit board, the glue thickness reference structure 30 may be arranged close to the four sides of the circuit board body 10, Figure 1 , Figure 4 and Figure 7 The number of the glue thickness reference structures 30 shown in the illustrated embodiment is only an example, and it is not limited thereto in reality. In some other embodiments, at least three glue thickness reference structures 30 are provided in the second region A2, and the orthographic projections of the at least three glue thickness reference structures 30 on the plane where the circuit board body 10 is located are not collinear, so as to ensure the formation of a glue thickness height reference plane.

[0087] Exemplarily, Figure 12A schematic structural diagram of another flexible printed circuit board provided by an embodiment of the present invention. Figure 12 In the illustrated embodiment, four glue thickness reference structures 30 are provided in the second region A2, respectively located at the four corners of the rectangular printed circuit board body to ensure the flatness of the insulating glue layer. When the number of the glue thickness reference structures 30 is small, some of the first devices 20 may be located in the second region A2.

[0088] The flexible printed circuit board provided by the embodiment of the present invention may further include any structure known to those skilled in the art, which will not be elaborated or limited in the embodiment of the present invention.

[0089] Based on the same inventive concept, an embodiment of the present invention further provides a display device. Figure 13 A schematic structural diagram of a display device provided by an embodiment of the present invention. As Figure 13 shown, the display device includes the flexible printed circuit board 100 and the display panel 200 provided by any embodiment of the present invention. Therefore, the display device provided by the embodiment of the present invention has the corresponding beneficial effects of the flexible printed circuit board provided by the embodiment of the present invention, which will not be elaborated here. Exemplarily, the display device may be an electronic device such as a mobile phone, a computer, a smart wearable device (for example, a smart watch), and a vehicle-mounted display device, etc., which is not limited in the embodiment of the present invention.

[0090] Note that the above is only the preferred embodiment of the present invention and the applied technical principle. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the inventive concept of the present invention, more other equivalent embodiments may be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A flexible printed circuit board, characterized in that, Comprising: A circuit board body, the circuit board body including a first area and a second area surrounding the first area; A plurality of first devices and a plurality of glue thickness reference structures located on the same side of the circuit board body, at least part of the first devices being soldered to the first area, and at least part of the glue thickness reference structures being located in the second area; In a first direction, the height of the glue thickness reference structure is greater than the height of the first device, the first direction being perpendicular to the plane where the circuit board body is located; An insulating glue layer, arranged on the same side as the first device, the insulating glue layer being located in the first area and the second area, and the insulating glue layer covering the first device.

2. The flexible printed circuit board according to claim 1, characterized in that, The insulating glue layer also covers the glue thickness reference structure, and the surface of the insulating glue layer facing away from the circuit board body is a flat surface.

3. The flexible printed circuit board according to claim 2, characterized in that, The glue thickness reference structure includes a second device, the second device being soldered to the second area, and the second device and the first device being respectively electrically connected to conductive lines in the circuit board body; In the first direction, the insulating glue layer covering the first device has a first thickness d1, and the insulating glue layer covering the second device has a second thickness d2; d0≤d2<d1, where d0 is the preset insulating glue thickness for the device.

4. The flexible printed circuit board according to claim 3, characterized in that The glue thickness reference structure further includes a first insulating post, the first insulating post being located on the surface of the second device facing away from the circuit board body; the insulating glue layer covers the second device and the first insulating post; In the first direction, the first insulating post has a first height h1, d0≤h1.

5. The flexible printed circuit board according to claim 2, characterized in that, The glue thickness reference structure includes a third device, the third device being soldered to the second area, the third device being electrically insulated from the conductive lines in the circuit board body, and the first device being electrically connected to the conductive lines; In the first direction, the insulating glue layer covering the first device has a first thickness d1, and the insulating glue layer covering the third device has a third thickness d3, 0<d3<d1.

6. The flexible printed circuit board according to claim 5, wherein In the first direction, the first device has a second height h2, and the third device has a third height h3; (h3 - h2)≥d0, where d0 is the preset insulating glue thickness for the device.

7. The flexible printed circuit board according to claim 2, characterized in that The glue thickness reference structure includes a second insulating post, in the first direction, one side of the second insulating post is in contact with the circuit board body, and the other side is in contact with the insulating glue layer; In the first direction, the insulating glue layer covering the first device has a first thickness d1, and the insulating glue layer covering the second insulating post has a fourth thickness d4, 0<d4<d1.

8. The flexible printed circuit board according to claim 7, wherein In the first direction, the first device has a second height h2, and the second insulating post has a third height h4; (h4 - h2)≥d0, where d0 is the preset insulating glue thickness for the device.

9. The flexible printed circuit board according to claim 1, wherein The insulating glue layer covers the side surface of the glue thickness reference structure, and the surface of the insulating glue layer facing away from the circuit board body is flush with the surface of the glue thickness reference structure facing away from the circuit board body.

10. The flexible printed circuit board according to claim 2 or 9, characterized in that, The heights of the plurality of glue thickness reference structures located in the second area are equal in the first direction.

11. The flexible printed circuit board according to claim 1, characterized in that, The connecting lines of the orthographic projections of the plurality of adhesive thickness reference structures on the plane where the circuit board body is located form a virtual closed figure, and the orthographic projection of the first device on the plane where the circuit board body is located is located within the virtual closed figure.

12. The flexible printed circuit board according to claim 1, wherein The flexible circuit board also includes insulating adhesive paper, and the insulating adhesive paper covers the insulating adhesive layer.

13. The flexible printed circuit board according to claim 1, wherein The circuit board body comprises a substrate layer, a cover film and a functional layer which are stacked; The substrate layer is welded to the first device, the cover film is located on a side of the substrate layer away from the first device, and the functional layer is located on a side of the cover film away from the substrate layer.

14. A display device, characterized in that, It comprises the flexible circuit board as claimed in any one of claims 1 to 13.

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