Foldable circuit board and its preparation method

Abstract

This application provides a foldable circuit board, including a substrate and an insulating protective layer. The substrate includes a stacked base material layer and a conductive circuit layer. The insulating protective layer covers a portion of the conductive circuit layer and has an opening. The substrate includes a first region, a second region, and a third region connecting the first and second regions. The first region is bent through the third region and disposed on one side of the second region in a first direction. The conductive circuit layer includes a first pad located in the first region and a second pad located in the second region. The first pad includes a first side, and the second pad includes a second side. Both the first and second sides are disposed away from the base material layer and are exposed through the opening. The second side is soldered to the first side. The foldable circuit board provided by this application can solve the problem of stress concentration, thereby improving the reliability of the foldable circuit board. This application also provides a method for manufacturing a foldable circuit board.

Description

Technical Field

[0001] This application relates to the field of foldable circuit board processing, specifically to a foldable circuit board and its preparation method. Background Technology

[0002] Circuit boards typically consist of a substrate layer and a conductive circuit layer. When fabricating foldable circuit boards, an adhesive layer is usually applied to the board, which is then bent and laminated to bond the folded board to the adhesive layer. However, the adhesive layer is prone to overflow after lamination, and stress concentration occurs at the bends of the board, thus reducing the reliability of the foldable circuit board. Summary of the Invention

[0003] In view of this, this application provides a foldable circuit board that helps to solve the stress concentration problem, thereby improving the reliability of the foldable circuit board.

[0004] In addition, this application also provides a method for manufacturing the circuit board.

[0005] This application provides a foldable circuit board, including a substrate and an insulating protective layer. The substrate includes a base material layer and a conductive line layer stacked along a first direction. The insulating protective layer covers a portion of the conductive line layer and has a window. The substrate includes a first region, a second region, and a third region connecting the first region and the second region. The first region is bent through the third region and disposed on one side of the second region in the first direction. The conductive line layer includes a first pad located in the first region and a second pad located in the second region. The first pad includes a first side, and the second pad includes a second side. Both the first side and the second side are disposed away from the base material layer and are exposed through the window. The second side is soldered to the first side.

[0006] This application also provides a method for manufacturing a foldable circuit board, comprising the following steps: providing a substrate, the substrate comprising a substrate layer and a conductive circuit layer stacked along a first direction, the substrate comprising a first region, a second region, and a third region connected between the first region and the second region, the conductive circuit layer comprising a first pad located in the first region and a second pad located in the second region, the first pad comprising a first side, the second pad comprising a second side, the first side and the second side both being disposed away from the substrate layer; forming an insulating protective layer covering a portion of the conductive circuit layer, the insulating protective layer having an opening, the first side and the second side both being exposed through the opening; bending the first region around the third region and stacking it on one side of the second region in the first direction, such that the first side and the second side are stacked in the first direction; soldering the first side and the second side.

[0007] In this application, a foldable circuit board is formed by soldering a first pad in a first region to a second pad in a second region, with the soldering points avoiding the third region, the boundary between the first and third regions, and the boundary between the second and third regions. Furthermore, the foldable circuit board provided in this application is shaped after soldering with the first and second pads, rather than by bonding the entire surface of the first and second regions together. Therefore, the rigid constraint force of the third region after the soldering points are formed can be reduced (the closer the soldering point is to the third region, the stronger the rigid constraint force of the third region). Thus, the foldable circuit board provided in this application can reduce stress concentration at bending points caused by soldering. Therefore, the foldable circuit board of this application can solve the problem of stress concentration, thereby improving the reliability of the foldable circuit board. At the same time, the method of shaping the foldable circuit board by soldering with pads also facilitates heat conduction within the circuit board. Attached Figure Description

[0008] Figure 1 A top view of a substrate with an insulating protective layer provided in an embodiment of this application;

[0009] Figure 2 for Figure 1 The cross-sectional view of the substrate shown along line V-V is shown.

[0010] Figure 3 for Figure 1 A schematic diagram showing the shape combination of the first side of the first pad and the second side of the second pad on the substrate;

[0011] Figure 4 In order to be in Figure 2 A cross-sectional view of an anti-oxidation layer formed on the first side and first side surface of the first pad of the substrate shown;

[0012] Figure 5 To be Figure 4 The diagram shows a cross-sectional view of the substrate after bending.

[0013] Figure 6 A cross-sectional view of a foldable circuit board provided in an embodiment of this application;

[0014] Figure 7 A top view of a foldable circuit board provided in an embodiment of this application;

[0015] Figure 8 A cross-sectional view of the substrate after the insulating protective layer and the solder layer cover it, according to another embodiment of this application;

[0016] Figure 9 A cross-sectional view of a foldable circuit board provided in another embodiment of this application.

[0017] Explanation of main component symbols

[0018] Foldable circuit board 100, 200, substrate 10

[0019] Substrate layer 11 Conductive circuit layer 12

[0020] First pad 121 First surface 1211

[0021] First side 1212 Second pad 122

[0022] Second side 1221 Second side 1222

[0023] Area 101, Area 202

[0024] Third Zone 103 Insulation Protective Layer 20

[0025] Window opening 21, anti-oxidation layer 30

[0026] Positioning hole 104, weld layer 40

[0027] First direction X, second direction Y

[0028] Third direction Z

[0029] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0031] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. When a component is said to be "set on" another component, it can be directly set on the other component or there may be an intervening component.

[0032] Example 1:

[0033] One embodiment of this application provides a method for fabricating a foldable circuit board 100. Depending on different requirements, the order of steps in the fabrication method can be changed, and some steps can be omitted or combined. The fabrication method includes the following steps:

[0034] Step 1: Refer to Figure 1 and Figure 2A substrate 10 is provided. The substrate 10 includes a substrate layer 11 and a conductive line layer 12 stacked along a first direction X. In some embodiments, the number of conductive line layers 12 is two. The two conductive line layers 12 are respectively disposed on opposite surfaces of the substrate layer 11. The conductive line layer 12 includes a first pad 121 and a second pad 122. In this embodiment, both conductive line layers 12 include a first pad 121 and a second pad 122. The first pad 121 includes a first surface 1211 disposed away from the substrate layer 11 and a first side surface 1212 respectively connected to the substrate layer 11 and the first surface 1211. The second pad 122 includes a second surface 1221 disposed away from the substrate layer 11 and a second side surface 1222 connected to the substrate layer 11 and the second surface 1221. Exemplarily, the number of first pads 121 can be two, three, one, or at least three. Correspondingly, the number of second pads 122 can also be two, three, one, or at least three. For example, the material of the substrate layer 11 can be one of polyimide, liquid crystal polymer, polyethylene terephthalate, or epoxy resin. The material of the conductive circuit layer 12 can be copper. The substrate 10 can be a single-layer conductive plate or a multi-layer conductive plate. The substrate 10 includes a first region 101, a second region 102, and a third region 103 connected between the first region 101 and the second region 102. A first pad 121 is located in the first region 101. A second pad 122 is located in the second region 102. The third region 103 can be bent in a subsequent step, that is, the first region 101 can be bent around the third region 103 and stacked on one side of the second region 102 in the first direction X, so that a first pad 121 is stacked with a second pad 122 in the first direction X. For example, the conductive circuit layer 12 can be prepared by an additive method, a subtractive method, or a semi-additive method.

[0035] In some embodiments, there are two first regions 101 and two third regions 103. Each first region 101 is connected to a second region 102 via a third region 103. Each first region 101 has a first pad 121 at one end connected to the third region 103. Both ends of the second region 102 have second pads 122. Specifically, a third region 103 is connected to the end of a first region 101 and the end of a second region 102. The two first regions 101 are arranged at intervals along a second direction Y perpendicular to the first direction X and are both located on the same side of the second region 102. The angle between the third region 103 and the second direction Y is an acute angle. The shape of the substrate 10 is designed to reduce the volume occupied by the substrate 10 in the second direction Y, thereby facilitating the fabrication of a substrate 10 with a longer extension length.

[0036] In some embodiments, the two first regions 101 are further parallel to each other along the second direction Y. The parallel arrangement of the first regions 101 can further reduce the volume occupied by the substrate 10 in the second direction Y. In some embodiments, both first regions 101 extend along a third direction Z. The third direction Z is perpendicular to the first direction X and the second direction Y. The angle between the third region 103 and the second direction Y can be 45 degrees.

[0037] In another embodiment, the substrate 10 may extend unidirectionally along the second direction Y.

[0038] Reference Figure 2 An insulating protective layer 20 is formed covering a portion of the conductive circuit layer 12. In this embodiment, an insulating protective layer 20 is formed on a conductive circuit layer 12, and each insulating protective layer 20 has a window 21. The first surface 1211 of the first pad 121 and the second surface 1221 of the second pad 122 of each conductive circuit layer 12 are exposed through the window 21. In some embodiments, the first side surface 1212 of the first pad 121 and the second side surface 1222 of the second pad 122 of each conductive circuit layer 12 are also exposed through the window 21. For example, the insulating protective layer 20 with the window 21 can be formed by printing solder resist ink.

[0039] Reference Figure 1 In some embodiments, the surface of the insulating protective layer 20 facing away from the substrate layer 11 may have a positioning hole 104. The positioning hole 104 is located at one end of the first region 101 away from the first pad 121 and penetrates the substrate 10 along the first direction X. The positioning hole 104 facilitates the positioning and fixing of the substrate 10. During the processing of the substrate 10, a positioning block on the operating table can be inserted into the positioning hole 104 to fix the substrate 10.

[0040] Reference Figure 1 and Figure 3 In some embodiments, when viewed along the first direction X, the shapes of the first surface 1211 and the second surface 1221 are combined in one of the following ways: a combination of a trapezoid and an inverted trapezoid, a combination of a square and a rectangle, a combination of intersecting quadrilaterals, or a combination of a circle and an ellipse. Specifically, refer to... Figure 3 In (a), the first face 1211 can be a square, and the corresponding second face 1221 can be a rectangle. Conversely, when the first face 1211 is a rectangle, the second face 1221 is a square. This shape arrangement of the first face 1211 and the second face 1221 facilitates a good contact area between them in subsequent welding steps, thereby improving the welding stability between them. The longer side of the rectangle can be greater than the side length of the square. Alternatively, refer to... Figure 3In (b), the first surface 1211 can be circular, and the corresponding second surface 1221 can be elliptical. Conversely, when the first surface 1211 is elliptical, the second surface 1221 is circular. The major diameter of the ellipse can be larger than the diameter of the circle. In this case, the shape settings of the first surface 1211 and the second surface 1221 are beneficial to improving the stability and tensile strength after welding the first surface 1211 and the second surface 1221. Alternatively, refer to... Figure 3 (c) Both the first face 1211 and the second face 1221 can be tilted quadrilaterals (e.g., rectangles or parallelograms), and when stacked, they form an acute-angled (e.g., 45-degree) intersection. In this case, the shape of the first face 1211 and the second face 1221 is advantageous in improving their tensile or shear resistance after welding. Alternatively, refer to... Figure 3 In step (d), the first surface 1211 can be a trapezoid (e.g., an isosceles trapezoid), and the corresponding second surface 1221 is an inverted trapezoid (e.g., an inverted isosceles trapezoid). The side lengths and included angles between the trapezoid and the inverted trapezoid can be exactly equal. The shape settings of the first surface 1211 and the second surface 1221 ensure a relatively large contact area between them, thereby improving the welding stability between the first surface 1211 and the second surface 1221 in subsequent steps.

[0041] In another embodiment, the first surface 1211 and the second surface 1221 can have the same shape and be the same size. For example, the first surface 1211 and the second surface 1221 can be a combination of both being rectangles, both being squares, both being polygons, or both being circles.

[0042] In this embodiment, both the first surface 1211 and the second surface 1221 are continuous planes. In another embodiment, a first opening (not shown) may be provided in the first pad 121, and the first opening may penetrate the first surface 1211. A second opening (not shown) may be provided in the second pad 122, and the second opening may penetrate the second surface 1221.

[0043] Step Two: Refer to Figure 4 An anti-oxidation layer 30 is formed within the opening 21, covering the first surface 1211, the first side surface 1212, the second surface 1221, and the second side surface 1222. For example, the anti-oxidation layer 30 can be formed by chemical plating (e.g., a chemical gold plating layer). Forming the anti-oxidation layer 30 on the first pad 121 and the second pad 122 prevents both the first pad 121 and the second pad 122 from excessive oxidation in air.

[0044] In another embodiment, step two may be omitted.

[0045] Step 3: Refer to Figure 5 The first region 101 is bent around the third region 103 and then superimposed on one side of the second region 102 in the first direction X, so that the first surface 1211 and the second surface 1221 are superimposed in the first direction X.

[0046] In this embodiment, two first regions 101 are respectively stacked on opposite sides of the second region 102 in the first direction X.

[0047] Step Four: Refer to Figure 6 The overlapping area of ​​the first pad 121 and the second pad 122 can be welded using a spot welding machine, so that the second surface 1221 is welded to the first surface 1211 by metal-to-metal bonding, thereby improving the connection stability between the first pad 121 and the second pad 122. The spot welding machine can be either an ultrasonic spot welding machine (with an acoustic frequency of 15kHz to 20kHz) or a high-frequency spot welding machine (with an acoustic frequency greater than 100kHz). In this embodiment, a high-frequency spot welding machine is used to heat and weld the first surface 1211 and the second surface 1221.

[0048] In some embodiments, after the above soldering, a first pad 121 of a first region 101 is soldered to a second pad 122 on one side of the substrate layer 11, and a first pad 121 of another first region 101 is soldered to a second pad 122 on the other side of the substrate layer 11 to obtain a folded circuit board 100 with a three-layer stacked structure (see reference). Figure 7 This allows for a reduction in the size of the folded circuit board 100 in the second direction Y.

[0049] In some embodiments, after the above welding, the projection of the second region 102 in the first direction X lies within the range of each first region 101.

[0050] In another embodiment, when only one conductive line layer 12 is provided, the two first regions 101 can be stacked on the same side of the second region 102 to obtain a two-layer stacked circuit board, thereby reducing the size of the folded circuit board 100 in the first direction X.

[0051] In some embodiments, during the soldering of the first pad 121 and the second pad 122, the anti-oxidation layer 30 disposed on the first surface 1211 and the second surface 1221 is removed to obtain the folded circuit board 100. The anti-oxidation layer disposed on the first surface 1211 and the second surface 1221 can be removed by melting (high-frequency spot welding) or friction (ultrasonic spot welding).

[0052] Example 2:

[0053] Reference Figure 6This application also provides a foldable circuit board 100 in one embodiment. The foldable circuit board 100 can be prepared by the method of Embodiment 1. The foldable circuit board 100 includes a substrate 10 and an insulating protective layer 20. The substrate 10 includes a substrate layer 11 and a conductive line layer 12 stacked along a first direction X. The substrate 10 can be a single-layer conductive plate or a multi-layer conductive plate. In some embodiments, the number of conductive line layers 12 is two. The two conductive line layers 12 are respectively disposed on opposite surfaces of the substrate layer 11. Referring to reference Figure 1 The substrate 10 includes a first region 101, a second region 102, and a third region 103 connecting the first region 101 and the second region 102. Each conductive line layer 12 includes a first pad 121 located in the first region 101 and a second pad 122 located in the second region 102. The first pad 121 includes a first surface 1211 facing away from the substrate layer 11 and a first side surface 1212 connecting the substrate layer 11 and the first surface 1211. The second pad 122 includes a second surface 1221 facing away from the substrate layer 11 and a second side surface 1222 connecting the substrate layer 11 and the second surface 1221. For example, the number of first pads 121 can be two, three, one, or at least three. Correspondingly, the number of second pads 122 can also be two, three, one, or at least three. An insulating protective layer 20 covers a portion of the conductive line layer 12. The insulating protective layer 20 has an opening 21. Both the first surface 1211 and the second surface 1221 are exposed through the opening 21. In some embodiments, both the first side surface 1212 and the second side surface 1222 are also exposed within the window 21. The first region 101 is bent around the third region 103 and stacked on one side of the second region 102 in the first direction X. The second side surface 1221 is welded to the first side surface 1211.

[0054] In this application, a foldable circuit board 100 is formed by soldering the first pad 121 of the first region 101 to the second pad 122 of the second region 102, and the soldering points avoid the third region 103, the boundary between the first region 101 and the third region 103, and the boundary between the second region 102 and the third region 103. Furthermore, the foldable circuit board 100 provided in this application is shaped after soldering the first pad 121 and the second pad 122, rather than by bonding the entire surface of the first region 101 and the second region 102 together. Therefore, the rigid constraint force of the third region 103 after the soldering points are formed can be reduced (the closer the soldering point is to the third region 103, the stronger the rigid constraint force of the third region 103). Thus, the foldable circuit board 100 provided in this application can reduce stress concentration at the bending points caused by soldering. Therefore, the foldable circuit board 100 of this application can solve the problem of stress concentration, thereby improving the reliability of the foldable circuit board 100. Meanwhile, the foldable circuit board 100 is shaped by soldering pads, which also facilitates heat conduction inside the foldable circuit board.

[0055] In some embodiments, in conjunction with reference Figure 1 There are two first regions 101 and two third regions 103. Each first region 101 is connected to a second region 102 via a third region 103. Each first region 101 has a first pad 121 at one end connected to the third region 103. Both ends of the second region 102 have second pads 122. Before the substrate 10 is bent, the two first regions 101 can be arranged at intervals along a second direction Y perpendicular to the first direction X and both located on the same side of the second region 102. Optionally, both first regions 101 extend along a third direction Z. The third direction Z is perpendicular to the first direction X and the second direction Y. The angle between the third region 103 and the second direction Y is an acute angle. Optionally, the angle between the third region 103 and the second direction Y can be a 45-degree angle. In the folded circuit board 100, the first pad 121 of one first region 101 is soldered to a second pad 122 on one side of the substrate layer 11. The first pad 121 of the other first region 101 is soldered to a second pad 122 on the other side of the substrate layer 11. The first region 101 is stacked on opposite sides of the second region 102, which helps to reduce the size of the folded circuit board 100 in the second direction Y.

[0056] In another embodiment, the two first regions 101 may be stacked on the same side of the second region 102 to reduce the size of the foldable circuit board 100 in the first direction X.

[0057] In some embodiments, the projection of the second region 102 in the first direction X lies within the range of each first region 101 (refer to...). Figure 7 ).

[0058] In some embodiments, refer to Figure 1 and Figure 3 Before the substrate 10 is bent, when viewed along the first direction X, the shapes of the first surface 1211 and the second surface 1221 can be combined in one of the following ways: a combination of a trapezoid and an inverted trapezoid, a combination of a square and a rectangle, a combination of intersecting quadrilaterals, or a combination of a circle and an ellipse. Specifically, refer to... Figure 3 In (a), the first face 1211 can be a square, and the corresponding second face 1221 can be a rectangle. Conversely, when the first face 1211 is a rectangle, the second face 1221 is a square. The length of the longer side of the rectangle can be greater than the side length of the square. This shape arrangement of the first face 1211 and the second face 1221 facilitates a good contact area between them in subsequent welding steps, thereby improving the welding stability between the first face 1211 and the second face 1221. Alternatively, refer to... Figure 3 In (b), the first surface 1211 can be circular, and the corresponding second surface 1221 can be elliptical. Conversely, when the first surface 1211 is elliptical, the second surface 1221 is circular. The major diameter of the ellipse can be larger than the diameter of the circle. In this case, the shape settings of the first surface 1211 and the second surface 1221 are beneficial to improving the stability and tensile strength after welding the first surface 1211 and the second surface 1221. Alternatively, refer to... Figure 3 (c) Both the first face 1211 and the second face 1221 can be tilted quadrilaterals (e.g., rectangles or parallelograms), and when stacked, they form an acute-angled (e.g., 45-degree) intersection. In this case, the shape of the first face 1211 and the second face 1221 is advantageous in improving their tensile or shear resistance after welding. Alternatively, refer to... Figure 3 In (d), the first surface 1211 can be a trapezoid (e.g., an isosceles trapezoid), and the corresponding second surface 1221 is an inverted trapezoid (e.g., an inverted isosceles trapezoid). The side lengths and included angles between the trapezoid and the inverted trapezoid can be exactly equal. The shape settings of the first surface 1211 and the second surface 1221 described above can improve the welding stability between the first surface 1211 and the second surface 1221.

[0059] In another embodiment, the first surface 1211 and the second surface 1221 can have identical shapes and be of equal size. For example, the first surface 1211 and the second surface 1221 can be a combination of both being rectangles, both being squares, both being polygons, or both being circles. The identical shapes of the first surface 1211 and the second surface 1221 facilitate the forming and fabrication of the first pad 121 and the second pad 122.

[0060] In some embodiments, refer to Figure 6 The foldable circuit board 100 also includes an anti-oxidation layer 30. The anti-oxidation layer 30 covers the first side 1212 and the second side 1222.

[0061] Example 3:

[0062] This application also provides a method for fabricating a foldable circuit board 200 in one embodiment. The difference from Embodiment 1 is that the substrate 10 includes a conductive circuit layer 12. In step two, a solder layer 40 (see reference 1) is formed within the window 21, covering the first surface 1211, the first side surface 1212, the second surface 1221, and the second side surface 1222. Figure 8 For example, the solder paste layer. In step four, the first pad 121 and the second pad 122 are connected via the solder layer 40, instead of soldering the first pad 121 to the second pad 122 (see reference). Figure 9 ).

[0063] In another embodiment, the substrate 10 may also include two conductive line layers 12. The two conductive line layers 12 are respectively disposed on opposite surfaces of the substrate layer 11.

[0064] The foldable circuit board 200 provided in this embodiment can also solve the problems of stress concentration and excess adhesive.

[0065] Since the components in Embodiments 2 and 3 are made of the same materials as the corresponding components in Embodiment 1, they will not be described again.

[0066] The above description is merely an optimized implementation of this application, and its application should not be limited to this specific implementation. Other modifications and alterations made by those skilled in the art based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A foldable circuit board, comprising a substrate and an insulating protective layer, the substrate comprising a base material layer and a conductive circuit layer stacked along a first direction, the insulating protective layer covering a portion of the conductive circuit layer, the insulating protective layer having a window, characterized in that, The substrate includes a first region, a second region, and a third region connecting the first region and the second region. The first region is bent through the third region and disposed on one side of the second region in the first direction. The conductive line layer includes a first pad located in the first region and a second pad located in the second region. The first pad includes a first side, and the second pad includes a second side. Both the first side and the second side are disposed away from the substrate layer and are exposed through the opening. The second side is soldered to the first side.

2. The foldable circuit board as described in claim 1, characterized in that, The number of the first region and the third region are both two. Each first region is connected to the second region through a third region. Each first region is provided with a first pad at one end connected to the third region. The second region is provided with a second pad at both ends. The angle between the third region and the second direction perpendicular to the first direction is an acute angle. The number of conductive circuit layers is two. The two conductive circuit layers are respectively disposed on opposite surfaces of the substrate layer and each includes a first pad and a second pad. The first pad of the first region is soldered to the second pad on one side of the substrate layer, and the first pad of the other region is soldered to the second pad on the other side of the substrate layer.

3. The foldable circuit board as described in claim 2, characterized in that, The projection of the second region onto the first direction lies within the range of each of the first regions.

4. The foldable circuit board as described in any one of claims 1 to 3, characterized in that, Before the substrate is bent, when viewed along the first direction, the shapes of the first and second surfaces are a combination of trapezoids and inverted trapezoids, squares and rectangles, quadrilaterals placed in a cross pattern, or circles and ellipses.

5. The foldable circuit board as described in any one of claims 1 to 3, characterized in that, The foldable circuit board further includes an anti-oxidation layer, the first pad further includes a first side connected to the substrate layer and the first surface, the second pad further includes a second side connected to the substrate layer and the second surface, both the first side and the second side are exposed through the opening, and the anti-oxidation layer covers the first side and the second side.

6. A method for manufacturing a foldable circuit board, characterized in that, Includes the following steps: A substrate is provided, the substrate including a substrate layer and a conductive line layer stacked along a first direction, the substrate including a first region, a second region and a third region connected between the first region and the second region, the conductive line layer including a first pad located in the first region and a second pad located in the second region, the first pad including a first side and the second pad including a second side, both the first side and the second side being disposed away from the substrate layer; An insulating protective layer is formed covering a portion of the conductive circuit layer. The insulating protective layer has a window, and both the first side and the second side are exposed through the window. The first region is bent around the third region and then superimposed on one side of the second region in the first direction, so that the first surface and the second surface are superimposed in the first direction; Weld the first surface and the second surface.

7. The preparation method according to claim 6, characterized in that, The first pad further includes a first side surface connected to the substrate layer and the first surface, and the second pad further includes a second side surface connected to the substrate layer and the second surface. Both the first side surface and the second side surface are exposed through the opening. Before the soldering, the preparation method further includes the step of: An anti-oxidation layer is formed inside the window, covering the first surface, the first side surface, the second surface, and the second side surface; Remove the anti-oxidation layer provided on the first surface and the second surface.

8. The preparation method according to claim 6 or 7, characterized in that, There are two first regions and two third regions. Each first region is connected to the second region through a third region. Each first region is provided with a first pad at one end connected to the third region. The second region is provided with second pads at both ends. Before the bending, the two first regions are arranged at intervals along a second direction perpendicular to the first direction and are both located on the same side of the second region. The angle between the third region and the second direction is an acute angle. The number of conductive circuit layers is two. The two conductive circuit layers are respectively disposed on opposite surfaces of the substrate layer and each includes a first pad and a second pad. After bending, the two first regions are respectively stacked on opposite sides of the second region in the first direction. After welding, the first pad of one first region is welded to the second pad on one side of the substrate layer, and the first pad of the other first region is welded to the second pad on the other side of the substrate layer.

9. The preparation method according to claim 8, characterized in that, After the welding, the projection of the second region in the first direction lies within the range of each of the first regions.

10. The preparation method according to claim 7, characterized in that, Before the bending, when viewed along the first direction, the shapes of the first and second surfaces are a combination of a trapezoid and an inverted trapezoid, a square and a rectangle, a combination of intersecting quadrilaterals, or a combination of a circle and an ellipse.

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