Printed circuit board

Abstract

This printed circuit board comprises a base film and at least one wiring. The base film has a main surface. The at least one wiring is disposed on the main surface. Each of the at least one wiring has an end part, a sloped part, and a central part. The sloped part connects the end part and the central part. The top surface of the sloped part is connected to the top surface of the end part and the top surface of the central part. The central part has a height of 100 μm or more. The sloped part decreases in thickness proceeding away from the end part and toward the central part.

Description

Printed wiring board 【0001】 The present disclosure relates to a printed wiring board. 【0002】 WO 2021 / 140855 (Patent Document 1) describes a printed wiring board. The printed wiring board described in Patent Document 1 has a base film and wiring. The wiring is disposed on the main surface of the base film. The wiring has a winding portion and a land. In the winding portion, the wiring is wound in a spiral shape. The land is connected to the innermost circumference of the winding portion. The winding portion has a first winding portion located at the outermost circumference and a second winding portion connecting the first winding portion and the land. The average height of the wiring in the land is 1.1 times or more and 5 times or less the average height of the wiring in the second winding portion. 【0003】 WO 2021 / 140855 【0004】 The printed wiring board of the present disclosure includes a base film and at least one wiring. The base film has a main surface. The at least one wiring is disposed on the main surface. Each of the at least one wiring has an end portion, an inclined portion, and a central portion. The inclined portion connects the end portion and the central portion. The top surface of the inclined portion is continuous with the top surface of the end portion and the top surface of the central portion. The height of the central portion is 100 μm or more. The thickness of the inclined portion decreases as it moves away from the end portion and approaches the central portion. 【0005】Figure 1 is a plan view of the printed circuit board 100. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 1. Figure 4 is a cross-sectional view of the printed circuit board 100 with the coverlay 30 attached. Figure 5 is a plan view of the printed circuit board 100A. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. Figure 7 is a cross-sectional view taken along line VII-VII in Figure 5. Figure 8 is a manufacturing process diagram of the printed circuit board 100. Figure 9 is a cross-sectional view illustrating the electroless plating process S2. Figure 10 is a cross-sectional view illustrating the resist pattern formation process S3. Figure 11 is a first cross-sectional view illustrating the electrolytic plating process S4. Figure 12 is a second cross-sectional view illustrating the electrolytic plating process S4. Figure 13 is a cross-sectional view illustrating the resist pattern removal process S5. Figure 14 is a plan view of the printed circuit board 200. Figure 15 is a cross-sectional view taken along line XV-XV in Figure 14. Figure 16A is a plan view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 16B is a first cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 16C is a second cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 17A is a plan view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. Figure 17B is a first cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. Figure 17C is a second cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. 【0006】 [Problems this disclosure aims to solve] The printed circuit board described in Patent Document 1 may have an adhesive layer and a protective film, or a coverlay may be attached. The adhesive layer is arranged on the main surface of the base film so as to cover the wiring. The protective film is arranged on the adhesive layer. When the height of the wiring is large, the wiring may fall over when the coverlay is attached. 【0007】This disclosure has been made in view of the above-mentioned problems of the prior art. More specifically, this disclosure provides a printed circuit board capable of suppressing the bending of wiring when a coverlay is applied. 【0008】 [Effects of this disclosure] The printed circuit board of this disclosure makes it possible to suppress the bending of wiring when attaching a coverlay. 【0009】 [Description of Embodiments of the Disclosure] First, embodiments of the disclosure will be listed and described. 【0010】 (1) The printed circuit board according to the embodiment comprises a base film and at least one wiring. The base film has a main surface. At least one wiring is arranged on the main surface. Each of the at least one wiring has an end, an inclined portion, and a central portion. The inclined portion connects the end and the central portion. The top surface of the inclined portion is connected to the top surface of the end and the top surface of the central portion. The height of the central portion is 100 μm or more. The thickness of the inclined portion decreases as it moves away from the end and closer to the central portion. According to the printed circuit board of (1) above, it is possible to suppress the bending of the wiring when attaching a coverlay. 【0011】 (2) In the printed circuit board described in (1) above, the angle of inclination of the top surface of the inclined portion relative to the main surface may decrease as it moves away from the edges and closer to the center. 【0012】 (3) In the printed circuit board described in (1) or (2) above, the width of the inclined portion and the width of the central portion may be 50 μm or less. 【0013】 (4) In the printed circuit boards described in (1) to (3) above, the value obtained by dividing the difference between the height of the edge and the height of the center by the length of the inclined portion may be greater than 0.01 and less than 10. 【0014】 (5) In the printed circuit board described in (4) above, the value obtained by dividing the difference between the height of the edge and the height of the central part by the length of the inclined part may be 0.05 or more. According to the printed circuit board described in (5) above, it is possible to further suppress the bending of the wiring when attaching the coverlay. 【0015】(6) In the printed circuit board described in (4) or (5) above, the value obtained by dividing the difference between the height of the edge and the height of the central part by the length of the inclined part may be 1 or less. According to the printed circuit board described in (6) above, it is possible to suppress the occurrence of voids between the adhesive layer of the coverlay and the main surface of the base film when the coverlay is attached. 【0016】 (7) In the printed circuit boards described in (1) to (6) above, the width of the edges may be greater than the width of the inclined portion and the width of the central portion. 【0017】 (8) The printed circuit boards described in (1) to (7) above may further include an adhesive layer and a protective film. The adhesive layer may be placed on the main surface so as to cover at least one wire. The protective film may be placed on the adhesive layer. 【0018】 [Details of Embodiments of the Disclosure] Next, details of embodiments of the disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals, and redundant descriptions will not be repeated. The printed circuit board according to the embodiment will be referred to as printed circuit board 100. 【0019】 (Configuration of the printed circuit board 100) The configuration of the printed circuit board 100 is described below. 【0020】 Figure 1 is a plan view of the printed circuit board 100. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 1. As shown in Figures 1 to 3, the printed circuit board 100 has a base film 10 and wiring 20. In the example shown in Figures 1 to 3, there are three wirings 20, but the number of wirings 20 can be one or more. The distance between two adjacent wirings 20 is denoted as distance DIS. 【0021】 The base film 10 is made of a flexible, electrically insulating material. For example, the base film 10 is made of polyimide. The base film 10 has a main surface 10a and a main surface 10b. The main surface 10b is the opposite surface of the main surface 10a. 【0022】The wiring 20 is arranged on the main surface 10a. In a plan view (when viewed along the direction normal to the main surface 10a), the wiring 20 extends in a straight line. The wiring 20 has end portions 21, inclined portions 22, and a central portion 23. The end portions 21 are located at both ends of the wiring 20 in a plan view. The inclined portions 22 connect the central portion 23 and the end portions 21. 【0023】 Let the height of the end portion 21 be height H1. Let the height of the inclined portion 22 be height H2. Let the height of the central portion 23 be height H3. Height H1 is greater than height H3. Height H2 is equal to height H1 at the connection point with the end portion 21 and equal to height H3 at the connection point with the central portion 23. From another perspective, the top surface of the inclined portion 22 is connected to the top surface of the end portion 21 and the top surface of the central portion 23. The top surface of the inclined portion 22 is inclined such that height H2 decreases as it moves away from the end portion 21 and approaches the central portion 23. Height H3 is 100 μm or more. Height H3 may be 120 μm or more. 【0024】 Let the inclination angle θ be the angle of inclination of the top surface of the inclined portion 22. The inclination angle θ is the angle between the tangent to the top surface of the inclined portion 22 and the main surface 10a. The inclination angle θ decreases as you move away from the end portion 21 and approach the central portion 23. 【0025】 The width of the end portion 21 is defined as width W1, and the width of the inclined portion 22 is defined as width W2. The width of the central portion 23 is defined as width W3. Width W1 is, for example, greater than widths W2 and W3. In other words, the width of the wiring 20 is partially larger at the end portion 21. The difference between width W1 and width W2 (the difference between width W1 and width W3) is, for example, 5 μm or more. The difference between width W1 and width W2 (the difference between width W1 and width W3) may be 20 μm or more. Widths W2 and W3 are, for example, 50 μm or less. Widths W2 and W3 may be 30 μm or less. 【0026】 Let L be the length of the inclined portion 22. The inclination of the inclined portion 22 is defined as the value obtained by dividing the difference between width W1 and width W2 by length L. The inclination of the inclined portion 22 is, for example, greater than 0.01 and less than 10. The inclination of the inclined portion 22 may be 0.05 or greater. The inclination of the inclined portion 22 may be 1 or less. 【0027】 The wiring 20 has, for example, a base layer 24 and an electroplated layer 25. The base layer 24 has, for example, a seed layer 24a and an electroless plating layer 24b. The base layer 24 is arranged on the main surface 10a. More specifically, the seed layer 24a is arranged on the main surface 10a, and the electroless plating layer 24b is arranged on the seed layer 24a. The seed layer 24a is a layer formed by, for example, sputtering. The seed layer 24a is formed of, for example, a nickel-chromium alloy. The electroless plating layer 24b is a layer formed by electroless plating. The electroless plating layer 24b is formed of copper or a copper alloy. 【0028】 The electroplated layer 25 is placed on the underlayer 24. More specifically, the electroplated layer 25 is placed on the electroless plating layer 24b. The electroplated layer 25 is a layer formed by electroplating. The electroplated layer 25 is formed of, for example, copper or a copper alloy. 【0029】 Figure 4 is a cross-sectional view of the printed circuit board 100 with the coverlay 30 attached. As shown in Figure 4, the coverlay 30 has an adhesive layer 31 and a protective film 32. The adhesive layer 31 is placed on the main surface 10a so as to cover the wiring 20. The adhesive layer 31 is formed of a cured adhesive. The protective film 32 is placed on the adhesive layer 31. That is, the protective film 32 is attached to the printed circuit board 100 by the adhesive layer 31. 【0030】 The modified printed circuit board 100 is referred to as printed circuit board 100A. Figure 5 is a plan view of printed circuit board 100A. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. Figure 7 is a cross-sectional view taken along line VII-VII in Figure 5. As shown in Figures 5 to 7, the wiring 20 has lands 26 and lands 27 and a winding portion 28. 【0031】In the winding section 28, the wiring 20 is wound in a spiral shape in a plan view. Lands 26 and 27 are located at both ends of the wiring 20. Lands 26 and 27 are connected to the innermost and outermost circumferences of the winding section 28, respectively. In the printed circuit board 100A, the end 21 is the land 26 and 27, the portion of the winding section 28 adjacent to land 26 or land 27 is the inclined portion 22, and the portion of the winding section 28 located between the portion adjacent to land 26 and the portion adjacent to land 27 is the central portion 23. In addition, in the printed circuit board 100A, the distance between two adjacent portions of wiring 20 in the winding section 28 is the distance DIS. 【0032】 (Method for manufacturing the printed circuit board 100) The method for manufacturing the printed circuit board 100 will be described below. 【0033】 Figure 8 is a diagram illustrating the manufacturing process of the printed circuit board 100. As shown in Figure 8, the manufacturing method of the printed circuit board 100 includes a preparation step S1, an electroless plating step S2, a resist pattern formation step S3, an electrolytic plating step S4, a resist pattern removal step S5, an etching step S6, and a coverlay application step S7. 【0034】 In preparation step S1, a base film 10 is prepared. In the base film 10 prepared in preparation step S1, a seed layer 24a is placed on the main surface 10a. Figure 9 is a cross-sectional view illustrating the electroless plating step S2. As shown in Figure 9, in the electroless plating step S2, an electroless plating layer 24b is formed on the seed layer 24a by electroless plating. 【0035】Figure 10 is a cross-sectional view illustrating the resist pattern formation process S3. As shown in Figure 10, in the resist pattern formation process S3, a resist pattern 40 is formed on the base layer 24. In the resist pattern formation process S3, firstly, a dry film resist is applied. Secondly, the dry film resist is patterned by exposure and development, and the resist pattern 40 is formed. The resist pattern 40 has openings 41. The openings 41 penetrate the resist pattern 40, exposing the base layer 24. The width of the openings 41 at the positions where the end portions 21 are formed is larger than the width of the openings 41 at the positions where the inclined portions 22 and the central portions 23 are formed. 【0036】 Figure 11 is a first cross-sectional view illustrating the electroplating process S4. As shown in Figure 11, in the electroplating process S4, an electroplated layer 25 is formed on the underlayer 24 exposed from the opening 41 by electroplating. Figure 12 is a second cross-sectional view illustrating the electroplating process S4. 【0037】 As described above, the width of the opening 41 at the position where the end portion 21 is formed is greater than the width of the opening 41 at the positions where the inclined portion 22 and the central portion 23 are formed. At positions where the width of the opening 41 is small, it becomes difficult for the plating solution to enter the opening 41, and there tends to be a shortage of ions (copper ions) necessary for growing the electroplating layer 25. Therefore, as shown in Figure 12, the electroplating layer 25 forming the end portion 21 becomes thicker, the electroplating layer 25 forming the central portion 23 becomes thinner, and the electroplating layer 25 forming the inclined portion 22 becomes thinner as it moves away from the end portion 21 and approaches the central portion 23. 【0038】 Figure 13 is a cross-sectional view illustrating the resist pattern removal process S5. As shown in Figure 13, in the resist pattern removal process S5, the resist pattern 40 is removed. In the etching process S6, the underlayer 24 that was beneath the resist pattern 40 is removed by etching. In this way, the structure of the printed circuit board 100 shown in Figures 1 to 3 is formed. 【0039】In the coverlay application process S7, the coverlay 30 is applied to the printed circuit board 100. In the coverlay application process S7, firstly, the coverlay 30 is prepared. At this stage, the adhesive layer 31 is uncured. Secondly, with the adhesive layer 31 positioned facing the main surface 10a, the coverlay 30 is heated while being pressed toward the printed circuit board 100. As a result, the uncured adhesive layer 31 flows to cover the wiring 20 and hardens, and the coverlay 30 is applied to the printed circuit board 100. 【0040】 (Effects of Printed Wiring Board 100) The effects of printed wiring board 100 will be explained below in comparison with the comparative example. The printed wiring board related to the comparative example will be referred to as printed wiring board 200. 【0041】 Figure 14 is a plan view of the printed circuit board 200. Figure 15 is a cross-sectional view taken along line XV-XV in Figure 14. As shown in Figures 14 and 15, in the printed circuit board 200, the central portion 23 is connected to the end portion 21 without the intervening inclined portion 22, and the wiring 20 has a uniform height regardless of its position (heights H1 and H3 are equal). In this respect, the configuration of the printed circuit board 200 differs from that of the printed circuit board 100. 【0042】 Figure 16A is a plan view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 16B is a first cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 16C is a second cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 200. Figure 17A is a plan view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. Figure 17B is a first cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. Figure 17C is a second cross-sectional view illustrating the flow of the adhesive layer 31 when attaching the coverlay 30 to the printed circuit board 100. In Figures 16A to 16C and Figures 17A to 17C, the flow of the adhesive layer 31 is indicated by arrows. 【0043】As shown in FIGS. 16A to 16C, when the coverlay 30 is attached to the printed wiring board 200, when the adhesive layer 31 flows between adjacent wirings 20, a force in a direction perpendicular to the side surface of the wiring 20 is applied to the side surface of the wiring 20. When the height of the wiring 20 is large (for example, 100 μm or more), a large moment is applied to the wiring 20 by the above-described force, and the wiring 20 may fall down. 【0044】 On the other hand, as shown in FIGS. 17A to 17C, in the printed wiring board 100, since the wiring 20 has an end portion 21, an inclined portion 22, and a central portion 23, a flow of the adhesive layer 31 parallel to the direction in which the wiring 20 extends occurs due to the difference in height of these portions. As a result, the force applied to the side surface of the wiring 20 is reduced, and the fall of the wiring 20 is suppressed. 【0045】 In addition, when the height of the wiring 20 is large, the adhesive layer 31 may not sufficiently enter between adjacent wirings 20, and voids may be formed at the interface between the adhesive layer 31 and the main surface 10a. In the printed wiring board 100, since the flow of the adhesive layer 31 parallel to the direction in which the wiring 20 extends occurs as described above, the adhesive layer 31 easily flows between adjacent wirings 20, and the formation of voids at the interface between the adhesive layer 31 and the main surface 10a is suppressed. 【0046】 As the width of the wiring 20 becomes smaller (more specifically, as the widths W2 and W3 become smaller), the wiring 20 has to support the moment caused by the force applied to the side surface of the wiring 20 in a narrower area, so the wiring 20 becomes more likely to fall. However, according to the printed wiring board 100, it is possible to suppress the fall of the wiring 20 even when the width of the wiring 20 is small. 【0047】 (Example) Samples 1 to 7 were prepared as samples of the printed wiring board. Details of Samples 1 to 7 are shown in Table 1. In Samples 1 to 7, the height H1, the height H3, the width W1, the width W2, the width W3, and the length L were changed. In Samples 1 to 7, the width W2 and the width W3 were made equal. In Samples 1 to 7, the coverlay 30 was attached. In Samples 1 to 7, the distance DIS was set to 30 μm. 【0048】 【0049】 In Samples 1 to 3, height H1 and height H3 were equal. That is, in Samples 1 to 3, wiring 20 did not have an inclined portion 22, and the central portion 23 was directly connected to the end portion 21. In Sample 1, height H1 and height H3 were less than 100 μm, while in Samples 2 to 7, height H1 and height H3 were 100 μm or more. In Sample 2, width W2 and width W3 were more than 50 μm, while in Samples 1 and 3 to 7, width W2 and width W3 were 50 μm or less. 【0050】 The fall rate, void generation rate, and inclination of wiring 20 measured in Samples 1 to 7 are shown in Table 2. The fall rate of wiring 20 was calculated by observing the presence or absence of the fall of wiring 20 using a microscope and multiplying the value obtained by dividing the number of test pieces in which the fall of wiring 20 occurred by the total number of test pieces by 100. The presence or absence of fall was determined to be a fall of wiring 20 when there was a location where the distance between two adjacent wirings 20 was 15 μm or more when wiring 20 was viewed from above. The void generation rate was calculated by observing the presence or absence of voids at the interface between the main surface 10a and the adhesive layer 31 using a microscope and multiplying the value obtained by dividing the number of test pieces in which voids with an equivalent circle diameter of 5 μm or more occurred by the total number of test pieces by 100. In the measurement of the inclination of wiring 20, first, when wiring 20 was viewed from above, the distance by which the upper surface of one wiring 20 moved toward another wiring 20 adjacent to the one wiring 20 was measured. Second, assuming that there was no movement of the bottom surface of wiring 20, the inclination of wiring 20 was calculated based on the above movement distance and height H3. Then, the inclination calculated in this way was averaged by the total number of test pieces to obtain the inclination of wiring 20. 【0051】 【0052】In Sample 1, heights H1 and H3 were less than 100 μm, but widths W2 and W3 were 50 μm or less. In Sample 2, heights H1 and H3 were 100 μm or more, but widths W2 and W3 were greater than 50 μm. In Sample 3, heights H1 and H3 were 100 μm or more, and widths W2 and W3 were 50 μm or more. The tilt rate was 0 percent in Samples 1 and 2, but it was 50 percent in Sample 3. From this comparison, it was found that when heights H1 and H3 are 100 μm or more and widths W2 and W3 are 50 μm or less, the wiring 20 is more likely to tilt. 【0053】 In samples 4 through 7, the heights H1 and H3 were 100 μm or more, and the widths W2 and W3 were 50 μm or more. Also, unlike sample 3, samples 4 through 7 had inclined sections 22 for the wiring 20. The tilt rate of the wiring 20 in samples 4 through 7 was lower than that of the wiring 20 in sample 3. From this comparison, it was found that tilting of the wiring 20 can be suppressed even when the height H3 is 100 μm or more, by inclining the top surface of the inclined section 22 such that the height H2 decreases as it moves away from the end 21 and approaches the central section 23. 【0054】 In sample 4, the inclination of the inclined section 22 was less than 0.05, but in samples 5 to 7, the inclination of the inclined section 22 was 0.05 or greater. The tilting rate of the wiring 20 in samples 5 to 7 was 0 percent, which was lower than the tilting rate of the wiring 20 in sample 4. From this comparison, it was found that tilting of the wiring 20 can be further suppressed by setting the inclination of the inclined section 22 (i.e., the value obtained by subtracting height H3 from height H1 and dividing by length L) to 0.05 or greater. 【0055】 In samples 3 through 6, as the inclination of the inclined section 22 increased, the rate at which the wiring 20 tilted decreased, as did the inclination of the wiring 20. This decrease in the inclination of the wiring 20 as the inclination of the inclined section 22 increased indicates that increasing the inclination of the inclined section 22 suppresses the tilting of the wiring 20. 【0056】 In samples 4 through 6, the inclination of the inclined portion 22 was 1 or less, but in sample 7, the inclination of the inclined portion 22 was greater than 1. The void occurrence rate in samples 4 through 6 was 0 percent, which was lower than the void occurrence rate in sample 7. From this comparison, it was found that the occurrence of voids at the interface between the main surface 10a and the adhesive layer 31 can be suppressed by setting the inclination of the inclined portion 22 to 1 or less. 【0057】 The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and all modifications within the meaning and scope of equivalents of the claims are intended to be included. 【0058】 10 Base film, 10a, 10b Main surface, 20 Wiring, 21 Edge, 22 Inclined part, 23 Center part, 24 Underlayer, 24a Seed layer, 24b Electroless plating layer, 25 Electroplating layer, 26, 27 Land, 28 Winding part, 30 Coverlay, 31 Adhesive layer, 32 Protective film, 40 Resist pattern, 41 Opening, 100, 100A, 200 Printed wiring board, H1, H2, H3 Height, L Length, S1 Preparation process, S2 Electroless plating process, S3 Resist pattern formation process, S4 Electroplating process, S5 Resist pattern removal process, S6 Etching process, S7 Coverlay application process, W1, W2, W3 Width.

Claims

1. A printed circuit board comprising a base film and at least one wiring, wherein the base film has a main surface, the at least one wiring is arranged on the main surface, each of the at least one wiring has an end, an inclined portion, and a central portion, the inclined portion connects the end and the central portion, the top surface of the inclined portion is connected to the top surface of the end and the top surface of the central portion, the height of the central portion is 100 μm or more, and the thickness of the inclined portion decreases as it moves away from the end and closer to the central portion.

2. The printed circuit board according to claim 1, wherein the angle of inclination of the top surface of the inclined portion with respect to the main surface decreases as it moves away from the end and approaches the central portion.

3. The printed circuit board according to claim 1 or claim 2, wherein the width of the inclined portion and the width of the central portion are 50 μm or less.

4. The printed circuit board according to any one of claims 1 to 3, wherein the value obtained by dividing the difference between the height of the end portion and the height of the central portion by the length of the inclined portion is greater than 0.01 and less than 10.

5. The printed circuit board according to any one of claims 1 to 4, wherein the value obtained by dividing the difference between the height of the end portion and the height of the central portion by the length of the inclined portion is 0.05 or more.

6. The printed circuit board according to claim 4 or claim 5, wherein the value obtained by dividing the difference between the height of the end portion and the height of the central portion by the length of the inclined portion is 1 or less.

7. The printed circuit board according to any one of claims 1 to 6, wherein the width of the end portion is greater than the width of the inclined portion and the width of the central portion.

8. The printed circuit board according to any one of claims 1 to 7, further comprising an adhesive layer and a protective film, wherein the adhesive layer is disposed on the main surface so as to cover the at least one wiring, and the protective film is disposed on the adhesive layer.

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