Printed wiring board and method for manufacturing printed wiring board

Abstract

To provide a printed wiring board that includes a flying lead part having excellent electrical connection reliability.SOLUTION: A printed wiring board according to one aspect of the present disclosure includes: a base layer; and a conductive pattern on the base layer, having a conductive core, the conductive pattern having a flying lead part protruding from the base layer in a plan view, the flying lead part including the conductive core and a plating layer covering an entire outer surface of the conductive core.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to printed wiring boards and methods for manufacturing printed wiring boards. [Background technology]

[0002] Printed wiring boards are widely used to configure circuits in electronic devices, etc. Printed wiring boards having flying leads connected to terminals of other electronic circuits, etc. are well known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-144913 Summary of the Invention

[0004] A printed wiring board according to one aspect of the present disclosure is a printed wiring board comprising a base layer and a conductive pattern disposed on the base layer and having a conductive core, wherein the conductive pattern has a flying lead portion protruding from the base layer in a planar view, and the flying lead portion has the core and a plating layer covering the entire outer surface of the core. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic plan view showing a printed wiring board according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a cross section taken along line II-II of the printed wiring board of FIG. [Figure 3] 3 is a partially enlarged cross-sectional view showing the tip portion of a flying lead portion in the printed wiring board of FIG. [Figure 4] 4 is a schematic cross-sectional view showing a cross section taken along line IV-IV in the flying lead portion of the printed wiring board of FIG. [Figure 5] FIG. 5 is a flow diagram showing a method for manufacturing a printed wiring board according to an embodiment of the present disclosure. [Figure 6] 6A to 6C are schematic cross-sectional views showing the procedure for forming the conductive pattern in the forming step of FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a subsequent step of forming the conductive pattern in the forming step of FIG. 6. In FIG. [Figure 8] FIG. 8 is a schematic cross-sectional view showing a subsequent step of forming the conductive pattern in the forming step of FIG. 7. In FIG. [Figure 9] 9A to 9C are schematic cross-sectional views showing the procedure for arranging the insulating layer in the arranging step of FIG. [Figure 10] 10A to 10C are schematic cross-sectional views showing a procedure for removing a portion of the base layer in the removing step of FIG. [Figure 11] 11A to 11C are schematic cross-sectional views showing the plating procedure in the plating step of FIG. [Figure 12] FIG. 12 is a schematic cross-sectional view showing a procedure for forming a flying lead portion in a conventional method for manufacturing a printed wiring board. [Figure 13] FIG. 13 is a schematic cross-sectional view showing the next step of forming a flange lead portion in the conventional method of manufacturing a printed wiring board, following the step shown in FIG. [Figure 14] FIG. 14 is a schematic cross-sectional view showing the next step of forming a flange lead portion in the conventional method of manufacturing a printed wiring board, following the step shown in FIG. [Figure 15] FIG. 15 is a schematic cross-sectional view showing the next step of forming a flange lead portion in the conventional method of manufacturing a printed wiring board, following the step shown in FIG. [Figure 16] FIG. 16 is a schematic cross-sectional view showing the next step of forming a flange lead portion in the conventional method of manufacturing a printed wiring board, following the step shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] Patent Document 1 describes a printed wiring board having a flying lead portion, one side of which is supported by a second insulating resin layer and the other side of which terminates within an opening. Patent Document 1 also describes that the flying lead portion is formed by a subtractive method.

[0007] 12 to 16, a procedure for forming a flying lead portion by a subtractive method will be described. First, as shown in FIG. 12, openings 101a are formed partially in a base layer 101 using a mold, and then a metal foil 102a such as copper foil is laminated on the base layer 101. Next, as shown in FIG. 13, the metal foil 102a is etched using an etching method using a resist pattern to form a conductive pattern 102. Next, as shown in FIG. 14, an insulating layer 103 is applied to the conductive pattern 102 and to areas of the base layer 101 where the conductive pattern 102 is not disposed, so as to sandwich the conductive pattern 102 between the base layer 101 and the insulating layer 103. Next, as shown in FIG. 15, a plating layer 104 is formed on the portions of the conductive pattern 102 exposed in the openings 101a of the base layer 101 and on the portions not covered by the insulating layer 103. Then, as shown in FIG. 16, the conductive pattern 102 is cut at the portion exposed in the opening 101a to form a flying lead portion 110 that protrudes from the base layer 101 in a plan view.

[0008] However, this conventional formation procedure leaves the tip surfaces (cut surfaces) of the flying lead portions 110 unplated, which means that the flying lead portions 110 are susceptible to rust, posing a problem in terms of ensuring sufficient electrical connection reliability.

[0009] The present disclosure has been made in light of the above circumstances, and has an object to provide a printed wiring board having a flying lead portion that has excellent electrical connection reliability.

[0010] [Effects of this disclosure] A printed wiring board according to one aspect of the present disclosure has excellent electrical connection reliability of the flying lead portion.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] (1) A printed wiring board according to one embodiment of the present disclosure is a printed wiring board comprising a base layer and a conductive pattern disposed on the base layer and having a conductive core, the conductive pattern having a flying lead portion protruding from the base layer in a planar view, and the flying lead portion having the core and a plating layer covering the entire outer surface of the core.

[0013] In the printed wiring board, the flying lead portion has a plating layer that covers the entire outer surface of the core, and therefore the flying lead portion has excellent electrical connection reliability.

[0014] (2) In the above (1), the conductive pattern has a wiring portion supported by the base layer, and the wiring portion has a continuous portion continuing to the flying lead portion, and the continuous portion may consist of only the core, or the plating layer may be formed only on the outer peripheral surface of the core that is not supported by the base layer. With this configuration, the plating layer can be selectively formed on the flying lead portion, which is prone to a decrease in electrical connection reliability. As a result, manufacturing costs can be kept low while maintaining the electrical connection reliability of the flying lead portion.

[0015] (3) In the above (2), an insulating layer may be further provided on the wiring portion, and the insulating layer may sandwich the core body between the insulating layer and the base layer. With this configuration, the insulating layer protects the core body, thereby improving the electrical connection reliability of the entire conductive pattern.

[0016] (4) In any one of (1) to (3) above, the plating layer may include a gold plating layer. This configuration improves the electrical conductivity and rust resistance of the flying lead portion.

[0017] (5) In any of (1) to (4) above, the flying lead portion may have a bottom surface extending continuously from the base layer in a side view and a top surface facing the bottom surface, and both ends of the top surface in the width direction may be rounded. The printed wiring board can easily achieve the above configuration by using a semi-additive method. That is, the flying lead portion is suitable for being formed by the semi-additive method.

[0018] (6) In any of (1) to (5) above, the flying lead portion may have a bottom surface extending continuously from the base layer in a side view and a top surface facing the bottom surface, and the top surface may have a rounded tip end in the protruding direction. The printed wiring board can easily achieve the above configuration by using a semi-additive method. That is, the flying lead portion is suitable for being formed by the semi-additive method.

[0019] (7) A method for manufacturing a printed wiring board according to one embodiment of the present disclosure includes the steps of forming a core pattern on a base layer, removing a portion of the base layer so that a portion of the core pattern protrudes from the base layer in a planar view, and plating the entire outer surface of the portion of the core pattern protruding from the base layer.

[0020] The method for manufacturing the printed wiring board includes a step of plating the entire outer surface of the portion of the core pattern that protrudes from the base layer, so that the flying lead portion can be formed with excellent electrical connection reliability.

[0021] (8) In the above (7), the method may further include a step of disposing an insulating layer on the core pattern before the plating step. With this configuration, the core pattern is protected by the insulating layer, thereby improving the electrical connection reliability of the entire conductive pattern.

[0022] [Details of the embodiments of the present disclosure] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings are schematic and may not correspond to actual shapes, dimensions, ratios, etc.

[0023] [First embodiment] <Printed wiring board> The printed wiring board 10 shown in FIGS. 1 and 2 includes a base layer 1 and a conductive pattern 2 disposed on the base layer 1 and having a conductive core 21. The conductive pattern 2 has a flying lead portion 11 protruding from the base layer 1 in a plan view. As shown in FIG. 2, the flying lead portion 11 includes the core 21 and a plating layer (hereinafter also referred to as a "surface plating layer 22") that covers the entire outer surface of the core 21. The flying lead portion 11 is supported in a cantilevered manner by the base layer 1. That is, in this disclosure, the "flying lead portion" refers to a portion of the conductive pattern of the printed wiring board that is held in the air. Also, in this disclosure, the tip portion of the flying lead portion 11 is a free end portion that is held in the air.

[0024] In the printed wiring board 10, the flying lead portion 11 has a surface plating layer 22 that covers the entire outer surface of the core 21, and therefore the flying lead portion 11 has excellent electrical connection reliability. More specifically, the flying lead portion 11 has the surface plating layer 22 formed on the tip surface as well as the peripheral surface, which prevents the core 21 from being exposed to the outer surface. As a result, the flying lead portion 11 easily maintains the quality of the core 21 and has excellent electrical connection reliability.

[0025] The configuration of the printed wiring board 10 is not otherwise limited as long as the conductive pattern 2 disposed on the base layer 1 has flying lead portions 11. As an example, in Figures 1 and 2, the printed wiring board 10 includes an insulating layer 3 disposed on the conductive pattern 2 and in an area of ​​the base layer 1 where the conductive pattern 2 is not disposed, so as to sandwich the conductive pattern 2 between the base layer 1 and the insulating layer 3.

[0026] (base layer) The base layer 1 has insulating properties. The base layer 1 may be flexible or may not be flexible. When the base layer 1 is flexible, examples of the main component of the base layer 1 include polyimide, polyethylene terephthalate, liquid crystal polymer, and fluororesin. When the base layer 1 is not flexible, examples of the main component of the base layer 1 include glass epoxy, paper phenol, paper epoxy, glass composite, and glass. The printed wiring board 10 may be a flexible printed wiring board, a rigid printed wiring board, or a flex-rigid printed wiring board. Note that the term "main component" refers to the component with the largest content in terms of mass, for example, a component with a content of 50 mass% or more.

[0027] The lower limit of the average thickness of the base layer 1 may be 3 μm, 5 μm, or 10 μm from the viewpoint of increasing the insulating strength and mechanical strength. On the other hand, the upper limit of the average thickness may be 200 μm, 150 μm, or 100 μm from the viewpoint of reducing the thickness of the printed wiring board 10. In the present disclosure, the "average thickness" refers to the average value of thicknesses at any 10 points.

[0028] (Conductive pattern) The conductive pattern 2 has a flying lead portion 11 and a wiring portion 12 supported by the base layer 1. The conductive pattern 2 has the above-mentioned core 21, and a portion of the outer surface of the core 21 is covered with a surface plating layer 22. The core 21 has a conductive base layer 23 and a core plating layer 24 disposed on the conductive base layer 23. The core 21 can be formed, for example, by a semi-additive method.

[0029] The conductive underlayer 23 is conductive. The conductive underlayer 23 can be formed by, for example, sputtering or electroless plating, and may be formed by sputtering. That is, the conductive underlayer 23 may be a sputtered layer. Examples of materials for forming the conductive underlayer 23 include copper (Cu), silver (Ag), gold (Au), nickel (Ni), titanium (Ti), chromium (Cr), or alloys thereof. In particular, the conductive underlayer 23 may contain one or both of nickel and chromium, or may contain a nickel-chromium alloy. By containing one or both of nickel and chromium, the conductive underlayer 23 can easily maintain adhesion to the base layer 1.

[0030] The conductive base layer 23 may have a single-layer structure or a multi-layer structure. When the conductive base layer 23 has a single-layer structure, the conductive base layer 23 may be the sputtered layer described above. When the conductive base layer 23 has a multi-layer structure, the conductive base layer 23 may be a two-layer structure, for example, a sputtered layer and an electroless plating layer. The electroless plating layer may be, for example, an electroless copper plating layer containing copper as a main component.

[0031] The core plating layer 24 is an electroplated layer formed by, for example, electroplating. The core plating layer 24 may be, for example, an electrolytic copper plating layer containing copper as the main component. The core plating layer 24 and the conductive underlayer 23 may be layers containing different components.

[0032] (Wiring section) The wiring portion 12 may be supported directly by the base layer 1, or indirectly via another insulating member. The wiring portion 12 has a continuous portion 12a that is continuous with the flying lead portion 11. The continuous portion 12a is connected to the base end edge of the flying lead portion 11.

[0033] The continuous portion 12a may be composed only of the core 21. The continuous portion 12a may have a surface plating layer 22 only on the outer peripheral surface of the core 21 that is not supported by the base layer 1. When the continuous portion 12a of the printed wiring board 10 is covered with the insulating layer 3, the continuous portion 12a can be composed only of the core 21. When the continuous portion 12a of the printed wiring board 10 is not covered with the insulating layer 3, the continuous portion 12a can have a surface plating layer 22 on the outer peripheral surface of the continuous portion 12a that is not supported by the base layer 1. This configuration of the printed wiring board 10 allows the surface plating layer 22 to be selectively formed on the flying lead portion 11, which is prone to a decrease in electrical connection reliability. As a result, the electrical connection reliability of the flying lead portion 11 can be maintained while keeping manufacturing costs low. The "continuous portion" refers to a portion that continues from the base end edge of the flying lead portion 11, and its length is not particularly important. However, if there is a portion continuing from the base end edge of the flying lead portion 11 that is not covered by the insulating layer 3, this portion may be considered to be a continuous portion. Also, if there is no portion continuing from the base end edge of the flying lead portion 11 that is not covered by the insulating layer 3, the continuous portion may be a range of 1000 μm or less from the base end edge of the flying lead portion 11, or a range of 500 μm or less from the base end edge.

[0034] The core body 21 of the flying lead portion 11 is formed by extending the core body 21 of the continuous portion 12a. In other words, the core body 21 in the continuous portion 12a and the core body 21 of the flying lead portion 11 connected to the continuous portion 12a may extend linearly with the same width and thickness overall.

[0035] (Flying lead section) As shown in FIG. 1 , the flying lead portion 11 protrudes into the opening 13 of the base layer 1 in a plan view. The flying lead portion 11 is provided as a terminal to be connected to the terminal of another electronic circuit or the like. The flying lead portion 11 can have a shape including a core 21 formed by a semi-additive method and a surface plating layer 22 that covers the entire outer surface of the core 21. With this configuration, the flying lead portion 11 has excellent electrical connection reliability, is fine, and is easy to handle.

[0036] The surface plating layer 22 coats the outer surface of the core 21 in the flying lead portion 11 to improve rust resistance. Examples of metals contained in the surface plating layer 22 include gold, nickel, lead, tin, and palladium, and gold, which has excellent conductivity and rust resistance, may be used. In other words, the surface plating layer 22 may include a gold plating layer.

[0037] The surface plating layer 22 can be formed using, for example, electroless plating or electroplating. For example, the surface plating layer 22 may be a gold plating layer in which gold plating is applied directly to the outer surface of the core 21, a solder plating layer in which solder plating is applied directly to the outer surface of the core 21, or a tin plating layer in which tin plating is applied directly to the outer surface of the core 21. The surface plating layer 22 may also be a nickel-gold plating layer in which a nickel plating layer and a gold plating layer are laminated in this order on the outer surface of the core 21, a nickel-palladium-gold plating layer in which a nickel plating layer, a palladium plating layer, and a gold plating layer are laminated in this order on the outer surface of the core 21, a palladium-gold plating layer in which a palladium plating layer and a gold plating layer are laminated in this order on the outer surface of the core 21, or a gold-palladium-gold plating layer in which a gold plating layer, a palladium plating layer, and a gold plating layer are laminated in this order on the outer surface of the core 21.

[0038] The upper limit of the protruding length L of the flying lead portion 11 (the protruding length of the portion held in the air; see FIG. 2) may be 800 μm or 700 μm from the viewpoint of improving the handleability of the flying lead portion 11. On the other hand, the lower limit of the protruding length L is not particularly limited and may be any value greater than 0 μm, and may be 200 μm or 400 μm from the viewpoint of facilitating connection to terminals of other electronic circuits, etc.

[0039] The lower limit of the average thickness T (see FIG. 2) of the flying lead portion 11 may be 12 μm or 15 μm from the viewpoint of maintaining the necessary strength, etc. On the other hand, the upper limit of the average thickness T may be 50 μm, 30 μm, or 20 μm from the viewpoint of reducing the thickness of the printed wiring board 10, etc.

[0040] The lower limit of the average width W of the flying lead portion 11 (see FIG. 1) may be 20 μm or 25 μm from the viewpoint of maintaining the necessary strength. On the other hand, the upper limit of the average width W is not particularly limited, but may be 100 μm, 70 μm, or 50 μm from the viewpoint of miniaturizing the terminal. In this disclosure, "average width" means the average value of the widths at any 10 points.

[0041] The printed wiring board 10 has a plurality of flying lead portions 11 arranged in parallel with a gap therebetween. The lower limit of the pitch P (distance between center lines; see FIG. 2) between adjacent flying lead portions 11 may be 50 μm or 60 μm, from the viewpoint of facilitating connection to terminals of other electronic circuits, etc. On the other hand, the upper limit of the pitch P is not particularly limited, but may be 250 μm, 150 μm, or 100 μm, from the viewpoint of miniaturizing the terminals.

[0042] As shown in FIGS. 2 to 4, the flying lead portion 11 has a bottom surface 11a extending continuously from the base layer 1 in a side view and a top surface 11b facing the bottom surface 11a. The flying lead portion 11 also has a pair of side surfaces 11c connected to the bottom surface 11a and the top surface 11b at both widthwise edges, and a tip surface 11d located at the tip end in the protruding direction. Because the flying lead portion 11 is formed using the semi-additive method as described above, its cross-sectional shape perpendicular to the protruding direction (transverse cross-section) is rectangular, as shown in FIG. 4. That is, the pair of side surfaces 11c are parallel to each other and do not slope toward or away from each other from the bottom surface 11a to the top surface 11b. More specifically, the transverse cross-section of the flying lead portion 11 has a flat rectangular shape with an average thickness T smaller than the average width W. This configuration allows the flying lead portion 11 to bend easily when pressed in the thickness direction, and prevents unintended stress from being applied when pressed. This improves the ease of handling of flying lead portion 11. Note that the term "rectangular" is not limited to a strict rectangle, but includes, for example, a shape in which top surface 11b has a rounded portion as described below, or a shape in which top surface 11b is arched.

[0043] As shown in FIG. 4, both ends of the top surface 11b in the width direction may be rounded. The printed wiring board 10 can be easily formed in the above shape by using a semi-additive method, and for example, the above shape can be obtained due to the plating solution used to form the core 21. By rounding both ends of the top surface 11b in the width direction, the flying lead portion 11 can be easily connected to terminals of other electronic circuits, etc. For example, this shape can improve the wettability of the solder. Note that both ends of the bottom surface 11a of the flying lead portion 11 do not have to be rounded.

[0044] 4, the top surface 11b may have a generally gentle arch shape in cross section. That is, the height of the top surface 11b may increase from both ends in the width direction toward the center. The above shape of the printed wiring board 10 can be obtained, for example, due to the plating solution used to form the core 21. This shape makes it easier to improve the wettability of the solder.

[0045] As shown in FIG. 3, the top surface 11b may have a rounded tip in the protruding direction. The printed wiring board 10 can be easily formed in this shape by using a semi-additive method, and the shape can be obtained, for example, by using a plating solution to form the core 21. The flying lead portion 11 can be easily connected to terminals of other electronic circuits by having the top surface 11b have a rounded tip in the protruding direction. For example, this shape can improve the wettability of the solder.

[0046] (insulating layer) The insulating layer 3 may be, for example, a solder resist or a coverlay. Examples of the solder resist include photosensitive solder resist, thermosetting solder resist, and dry film solder resist. Examples of the coverlay include a two-layer structure having an insulating film and an adhesive layer. The main component of the insulating film may be, for example, the resin listed as the main component of the base layer 1.

[0047] The insulating layer 3 covers a part of the conductive pattern 2 other than the flying lead portion 11. The insulating layer 3 is disposed on the wiring portion 12. The insulating layer 3 may be disposed directly on the wiring portion 12.

[0048] The insulating layer 3 sandwiches the core 21 between itself and the base layer 1. With this configuration, the core 21 is protected by the insulating layer 3, thereby improving the electrical connection reliability of the entire conductive pattern 2. The insulating layer 3 and the base layer 1 may sandwich the core 21 so as to be in direct contact with each other.

[0049] <Printed wiring board manufacturing method> An example of a method for manufacturing the printed wiring board 10 will be described with reference to Figures 5 to 11. Below, a procedure for forming the core 21 by a semi-additive method will be described. As shown in Figure 5, the method for manufacturing the printed wiring board includes step S1 of forming a core pattern 31 on the base layer 1, step S3 of removing a part of the base layer 1 so that a part of the core pattern 31 protrudes from the base layer 1 in a plan view, and step S4 of plating the entire outer surface of the part of the core pattern 31 protruding from the base layer 1.

[0050] The method for manufacturing the printed wiring board includes a step S4 of plating the entire outer surface of the portion of the core pattern 31 that protrudes from the base layer 1, so that flying lead portions 11 with excellent electrical connection reliability can be formed.

[0051] The method for manufacturing a printed wiring board is not particularly limited as long as it includes the forming step S1, the removing step S3, and the plating step S4. However, the method for manufacturing a printed wiring board may further include the step S2 of arranging an insulating layer 3 on the core pattern 31 before the plating step S4. By including the arranging step S2, the method for manufacturing a printed wiring board can protect the core pattern 31 with the insulating layer 3 and improve the electrical connection reliability of the entire conductive pattern 2.

[0052] The disposing step S2 may be performed between the forming step S1 and the removing step S3, or between the removing step S3 and the plating step S4. Below, a procedure for performing the disposing step S2 between the forming step S1 and the removing step S3 will be described. In the following description, the same reference numerals may be used to designate components similar to those of the printed wiring board 10 described above, and a description thereof may be omitted.

[0053] (Forming process) In the forming step S1, a laminate 32 is first prepared, in which a conductive underlayer 23a is laminated on a base layer 1a, as shown in FIG. 6. Then, in the forming step S1, a resist pattern 41 is disposed on the conductive underlayer 23a of the laminate 32. The components and average thickness of the base layer 1a may be the same as those of the base layer 1 in FIG. 1. The conductive underlayer 23a may contain, for example, one or both of nickel and chromium, or may contain a nickel-chromium alloy. The conductive underlayer 23a may have either a single-layer structure or a multilayer structure. When the conductive underlayer 23a has a single-layer structure, the conductive underlayer 23a may be a sputtered layer. When the conductive underlayer 23a has a multilayer structure, the conductive underlayer 23a may be a two-layer structure consisting of a sputtered layer and an electroless plating layer. The resist pattern 41 may be formed using, for example, a photosensitive dry film resist.

[0054] 7, in the forming step S1, electroplating is performed on the conductive base layer 23a after the resist pattern 41 is disposed, thereby forming the core plating layer 24. The electroplating may be, for example, copper electroplating.

[0055] Next, in forming step S1, as shown in Fig. 8, after the electroplating, the resist pattern 41 and the conductive underlayer 23a overlapping the resist pattern 41 are removed. As a result, a core pattern 31 in which the conductive underlayer 23 and the core plating layer 24 are laminated in this order is formed on the base layer 1a. Note that the "core pattern" refers to the entire patterned core 21 in the conductive pattern 2 of the resulting printed wiring board 10.

[0056] (Placement process) 9, in the placing step S2, the insulating layer 3 is placed so as to cover a portion of the core pattern 31. In the placing step S2, the insulating layer 3 is placed on part or all of the area of ​​the core pattern 31 excluding the portion that constitutes the flying lead portion 11. In the placing step S2, in addition to the core pattern 31, the insulating layer 3 is also placed on part or all of the area of ​​the base layer 1 where the core pattern 31 is not placed.

[0057] (Removal process) In the removing step S3, a portion of the base layer 1a is removed as shown in Fig. 10. By removing a portion of the base layer 1a in the removing step S3, the base layer 1 shown in Fig. 1 is formed. In the removing step S3, a laser may be used to remove a portion of the base layer 1a. This configuration makes it possible to selectively and easily remove only the base layer 1a.

[0058] In the removing step S3, a region of the base layer 1a that supports at least the portion that will become the flying lead portion 11 is removed. That is, in the removing step S3, a portion of the base layer 1a is removed so that a portion of the core pattern 31 is cantilevered on the base layer 1. In the removing step S3, an opening 13 may be formed in the base layer 1a by removing a portion of the base layer 1a.

[0059] (Plating process) 11, in the plating step S4, a surface plating layer 22 is formed on the outer surface of the core pattern 31 that is exposed to the outside after the removing step S3. That is, in the plating step S4, the surface plating layer 22 is formed in an area of ​​the core pattern 31 that is not supported by the base layer 1 and is not covered by the insulating layer 3. As a result, the conductive pattern 2 of FIG. 2 is formed, which has a flying lead portion 11 that protrudes from the base layer 1 in a plan view and has the core 21 and the surface plating layer 22 that covers the entire outer surface of the core 21.

[0060] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0061] In the present disclosure, the flying lead portion only needs to have a core and a surface plating layer covering the entire outer surface of the core, and other configurations of the printed wiring board are not particularly limited. For example, the printed wiring board may be a single-layer body in which the conductive pattern is formed on only one side of the base layer, or a multi-layer body in which multiple base layers are stacked with the conductive pattern sandwiched between them. Furthermore, the printed wiring board may be configured without the insulating layer, depending on the application, arrangement, etc.

[0062] In the above embodiment, the core has been described as having a two-layer structure consisting of the conductive underlayer and the core plating layer. However, the core may have a structure other than that described in the above embodiment. For example, in the above embodiment, the conductive underlayer is formed using a sputtering method or an electroless plating method. However, the conductive underlayer may be attached to the base layer using an adhesive, or may be composed of a sintered body using copper nanoparticles. Furthermore, the core plating layer may be composed of two or more plating layers.

[0063] The printed wiring board only needs to have the surface plating layer on the entire outer surface of the flying lead portion, and the presence or absence and arrangement of the surface plating layer in portions other than the flying lead portion are not limited. The printed wiring board may have the surface plating layer in portions other than the flying lead portion so that the core is not exposed to the outside, or may have the surface plating layer only on the outer surface of the flying lead portion.

[0064] In the above embodiment, the flying lead portion has a rectangular cross section. However, the present disclosure does not intend to limit the specific shape of the flying lead portion to the shape in the above embodiment. [Explanation of symbols]

[0065] 1, 1a, 101 base layer 2, 102 Conductive pattern 3, 103 insulating layer 10 Printed wiring board 11, 110 Flying lead section 11a Bottom 11b Top 11c side 11d Tip surface 12 Wiring section 12a Continuous section 21 Core body 22 Surface plating layer 23, 23a Conductive underlayer 24 Core plating layer 31 Core pattern 32 Laminate 41 Resist Pattern 13, 101a opening 102a metal foil 104 plating layer L Flying lead projection length P Pitch between adjacent flying leads T Average thickness of flying lead W Average width of flying lead

Claims

1. A printed wiring board comprising a base layer and a conductive pattern disposed on the base layer and having a conductive core, the conductive pattern has a flying lead portion protruding from the base layer in a plan view, The flying lead portion of the printed wiring board has the core body and a plating layer that covers the entire outer surface of the core body.

2. the conductive pattern has a wiring portion supported by the base layer, the wiring portion has a continuous portion that is continuous with the flying lead portion, 2. The printed wiring board according to claim 1, wherein the continuous portion is made of only the core body, or the plating layer is provided only on the outer peripheral surface of the core body that is not supported by the base layer.

3. The wiring portion further includes an insulating layer disposed on the wiring portion, 3. The printed wiring board according to claim 2, wherein the insulating layer sandwiches the core body between the insulating layer and the base layer.

4. The printed wiring board according to claim 1 , wherein the plating layer includes a gold plating layer.

5. the flying lead portion has a bottom surface extending continuously from the base layer in a side view and a top surface facing the bottom surface, 4. The printed wiring board according to claim 1, wherein both widthwise ends of the top surface are rounded.

6. the flying lead portion has a bottom surface extending continuously from the base layer in a side view and a top surface facing the bottom surface, 4. The printed wiring board according to claim 1, wherein the top surface has a rounded tip in the protruding direction.

7. forming a core pattern on a base layer; removing a portion of the base layer so that a portion of the core pattern protrudes from the base layer in a plan view; a step of plating the entire outer surface of the portion of the core pattern that protrudes from the base layer; A method for manufacturing a printed wiring board comprising:

8. The method for manufacturing a printed wiring board according to claim 7 , further comprising the step of disposing an insulating layer on the core pattern prior to the step of plating.

Images