Wiring board and manufacturing method of wiring board

Abstract

To provide a wiring board having a wiring that is thicker than a general wiring, and provide a manufacturing method of the wiring board.SOLUTION: A wiring board 1 contains an insulation layer 10 and a patterned wiring layer 20. The wiring layer 20 includes: a titanium layer 21 that has titanium formed onto the insulation layer 10 as a main component; a nickel alloy layer 22 that contains nickel formed onto the titanium layer 21 and a metal other than nickel as the main components; a plating layer 23 that is formed onto the nickel alloy layer 22 by plating processing; and a metal paste sintering layer 24 that is formed onto the plating layer 23. An adhesion of the metal paste sintering layer 24 to the plating layer 23 can be enhanced by integrating the metal paste sintering layer 24 with the plating layer 23 when sintering the metal paste sintering layer 24, especially by making the plating layer 23 the same plating layer, and the metal paste sintering layer 24 a copper paste sintering layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wiring board and a method for manufacturing the wiring board, and more particularly, to a wiring board having wiring thicker than general wiring and a method for manufacturing the wiring board.

Background Art

[0002] Conventionally, a wiring board in which wiring is disposed on an insulating layer has been provided. For example, in Patent Document 1, a seed layer (copper layer) 51 is laminated on an insulating layer made of an insulating resin such as an epoxy resin or a polyimide resin by sputtering, a plating layer 52 by copper plating is laminated on the seed layer 51, and a conductive layer 53 containing conductive particles is laminated on the plating layer 52. A wiring board is disclosed. Further, in Patent Document 2, a wiring board in which a copper plate is joined via a brazing material on a ceramic substrate is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the demand for electronic components capable of passing a large current, called power devices, has been increasing. In order to pass a large current through these electronic components, a wiring board having thick wiring has been in demand. In this regard, for example, in Patent Document 1, when forming a conductive layer 53 that functions as a wiring, a sintered layer 73 is formed by exposing, developing, and sintering a photosensitive conductive material 70 (including a photosensitive organic material and conductive particles), and by repeating the exposure, development, and sintering of the photosensitive conductive material 70, a thick conductive layer 53 capable of passing a large current is configured. However, in Patent Document 1, in order to thicken the wiring, it is necessary to repeat the exposure, development, and sintering of the photosensitive conductive material 70. As a result, there is a problem that the number of processes increases, and the manufacturing time and manufacturing cost increase. Further, in Patent Document 2, by using a copper plate having a sufficient thickness, a wiring board having a wiring with a thickness capable of passing a large current can be provided. However, when etching the copper plate according to the wiring pattern, the thicker the copper plate is used, the deeper it is necessary to etch, and at the same time, the lateral erosion also increases. Therefore, the distance between adjacent wirings increases, and there is a problem that the wirings cannot be formed at a high density.

[0005] An object of the present invention is to provide a power distribution board having a wiring thicker than a general wiring and a method for manufacturing the wiring board.

Means for Solving the Problems

[0006] The gist of the present invention is a wiring board described in the following (1) to (8). (1) A wiring board having an insulating layer and a patterned wiring layer, wherein the wiring layer includes a titanium layer mainly composed of titanium formed on the insulating layer, a nickel alloy layer mainly composed of nickel and a metal other than nickel formed on the titanium layer, a plating layer formed by plating on the nickel alloy layer, and a metal paste sintered layer formed on the plating layer. (2) The wiring board according to (1) above, wherein the metal paste sintered layer has a thickness of 300 μm or more. (3) The wiring layer includes a first wiring and a second wiring adjacent to the first wiring, and the closest distance between the first wiring and the second wiring is less than 1 / 2 of the thickness of the wiring layer. The wiring board according to (1) above. (4) The wiring board according to (3) above, wherein the closest distance is 100 μm or less. (5) The metal paste sintered layer and the plating layer mainly comprise metal particles made of the same metal, and the metal paste sintered layer has a thickness of 2 times or more that of the plating layer. The wiring board according to (1) above. (6) The plating layer is a copper plating layer mainly composed of copper, and the metal paste sintered layer is a copper paste sintered layer mainly composed of copper. The wiring board according to (1) above. (7) The insulating layer is a layer mainly containing aluminum nitride or silicon nitride. The wiring board according to (1) above. (8) The nickel alloy layer is a nickel / titanium alloy layer mainly composed of nickel and titanium. The wiring board according to (1) above.

[0007] Further, the present invention mainly relates to a method for manufacturing a wiring board described in the following (9) to (13). (9) A step of forming a titanium layer mainly composed of titanium on the insulating layer, a step of forming a nickel alloy layer mainly composed of nickel on the titanium layer, a step of forming a plating layer by plating treatment on the nickel alloy layer, and a step of forming a metal paste sintered layer by sintering a metal paste applied in a wiring pattern shape on the plating layer. A method for manufacturing a wiring board. (10) The method for manufacturing a wiring board according to (9) above, wherein the metal paste sintered layer is formed by sintering the metal paste applied on the plating layer by screen printing. (11) The wiring pattern includes a first wiring and a second wiring adjacent to the first wiring. The method for manufacturing a wiring board according to (9) above, wherein the thicknesses of the first wiring and the second wiring are greater than the closest distance between the first wiring and the second wiring. (12) The method for manufacturing a wiring board according to (9) above, wherein the closest distance is 100 μm or less. (13) After forming the metal paste sintered layer in a wiring pattern shape, sequentially performing a step of etching the plating layer, a step of etching the nickel alloy layer, and a step of forming the titanium layer, to form a wiring layer composed of the titanium layer, the nickel alloy layer, the plating layer, and the metal paste sintered layer into a shape corresponding to the wiring pattern. The method for manufacturing a wiring board according to (9) above.

Effect of the Invention

[0008] According to the present invention, it is possible to provide a wiring board having a wiring thicker than a general wiring and a method for manufacturing the wiring board.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0010] An embodiment of the wiring board of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a wiring board 1 according to this embodiment. As shown in FIG. 1, in the wiring board 1, a wiring layer 20 is formed on an insulating layer 10, and the wiring layer 20 is formed by sequentially laminating a titanium layer 21, a nickel alloy layer 22, a plating layer 23, and a metal paste sintered layer 24 from below.

[0011] The insulating layer 10 is a layer that serves as the substrate on which the wiring layer 20 is formed in the wiring substrate 1, and can be composed of an insulating ceramic material. As the insulating layer 10, for example, nitrides such as silicon nitride and aluminum nitride, and oxides such as alumina can be used. Further, in the present embodiment, a pre-sintered insulating layer 10 can be used, but it is also possible to use a configuration in which the insulating layer 10 before sintering is sintered together with the metal paste sintered layer 24 described later.

[0012] The titanium layer 21 is a layer mainly composed of titanium, and is formed, for example, by sputtering titanium particles on the upper surface of the insulating layer 10. In the present invention, "mainly composed of" means occupying more than half (50% by weight or more, or 50% by volume or more) of the total metal components contained in each of the layers 21 to 24. Since the titanium layer 21 is mainly composed of titanium, it means that the titanium layer 21 contains 50% by weight or more or 50% by volume or more of titanium among the metal components (the same applies to the other layers 22 to 24). The titanium layer 21 is thinner than the nickel alloy layer 22, the plating layer 23, and the metal paste sintered layer 24, and for example, the thickness can be set to 0.01 to 0.10 μm. The titanium contained in the titanium layer 21 is an active metal, widely diffuses on the upper surface of the insulating layer 10, and has a property of strongly adhering to the insulating layer 10 made of an oxide or a nitride. Further, when the insulating layer is made of a nitride, titanium can react with the nitrogen contained in the insulating layer 10 to further enhance the adhesion between the upper surface of the insulating layer 10 and the titanium layer 21.

[0013] The nickel alloy layer 22 is a layer mainly composed of nickel and a metal other than nickel such as titanium or chromium, and a material containing nickel alloy particles can be formed on the upper surface of the titanium layer 21 by sputtering. Note that the content ratio of nickel and the metal other than nickel in the nickel alloy layer 22 is not particularly limited. For example, the ratio of nickel in the nickel alloy can be 70% or more and less than 99%, preferably 85% or more and 95% or less. Further, the thickness of the nickel alloy layer 22 is not particularly limited, but it can be made thicker than the titanium layer 21 and thinner than the plating layer 23 and the metal paste sintered layer 24. For example, the thickness of the nickel alloy layer 22 can be set to 0.1 to 5 μm. In this embodiment, a nickel / titanium alloy layer having a thickness of 0.5 to 1.5 μm and mainly composed of nickel and titanium is formed as the nickel alloy layer 22.

[0014] In this embodiment, by laminating the nickel alloy layer 22 on the titanium layer 21, it becomes possible to efficiently perform the plating process when forming the plating layer 23 on the upper surface of the nickel alloy layer 22. That is, when the plating layer 23 is directly formed on the upper surface of the titanium layer 21 by the plating process, since the titanium layer 21 has a property of being easily oxidized, the plating process may not be efficiently performed. On the other hand, in this embodiment, by forming the nickel alloy layer 22 on the titanium layer 21, oxidation of titanium on the surface of the titanium layer can be suppressed, and the nickel alloy layer 22 functions as a seed layer, enabling the plating process for forming the plating layer 23 to be efficiently performed.

[0015] The plating layer 23 is a layer mainly composed of metal particles used for wirings such as copper, aluminum, silver, tungsten, and molybdenum. By performing a plating process on the upper surface of the nickel alloy layer 22, it is formed on the nickel alloy layer 22. In the present embodiment, from the viewpoint of manufacturing cost, a copper plating layer formed by copper plating is to be formed as the plating layer 23. Also, the plating layer 23 may be an electrolytic plating layer formed by electrolytic plating, or may be an electroless plating layer formed by electroless plating. Note that the thickness of the plating layer 23 is not particularly limited, but it can be formed thicker than the titanium layer 21 and the nickel alloy layer 22 and thinner than the metal paste sintered layer 24. For example, the thickness of the plating layer 23 can be set to 5 to 10 μm.

[0016] Similar to the plating layer 23, the metal paste sintered layer 24 is a layer mainly composed of metal particles used for wirings such as copper, aluminum, silver, tungsten, and molybdenum. The metal paste sintered layer 24 is formed to have a certain thickness so that a large current can flow through it. Also, the metal paste sintered layer 24 is formed by laminating a paste containing the above metal particles on the plating layer 23 and sintering it. For example, a configuration can be adopted in which a copper plating layer mainly composed of copper particles is formed as the plating layer 23, and a copper paste sintered layer is formed by laminating and sintering a copper paste mainly composed of copper particles as the metal paste sintered layer 24. Note that by using a paste in which metal particles are added to an organic solvent as the metal paste, the organic solvent volatilizes during sintering, and the metal paste sintered layer 24 composed of metal particles can be formed.

[0017] In addition, the method for applying the metal paste that constitutes the patterned metal paste sintered layer 24 is not particularly limited. For example, it can be laminated by printing methods such as screen printing and offset printing, or by an application method using a dispenser. However, from the viewpoints of the area of the printed surface and the uniformity of the film thickness, it is preferable to perform screen printing. This is because in screen printing, even a metal paste with a relatively high viscosity can be handled, and a predetermined wiring pattern can be formed at once. Also, the thickness of the metal paste sintered layer 24 can be appropriately adjusted according to the desired application. For example, it can be a wiring with a thickness of 100 to 3000 μm (preferably 300 to 1500 μm or 500 to 2000 μm). Thereby, in the wiring board 1 according to the present embodiment, the thickness of the wiring layer 20 can be made 300 μm or more, and it becomes possible to manufacture a wiring board 1 having a wiring capable of passing a large current.

[0018] Note that, in order to increase the thickness of the metal paste sintered layer 24, it can be configured to perform screen printing a plurality of times. In this case, it may be configured such that the metal paste is stacked a plurality of times and then the stacked metal paste layers are sintered at once, or it can also be configured to perform sintering each time the metal paste is applied by screen printing. If a plurality of layers are stacked without sintering the metal paste, the shape of the metal paste sintered layer 24 may collapse. Therefore, within a range where the shape of the metal paste sintered layer 24 does not collapse, it is preferable to perform screen printing and sintering of the metal paste a plurality of times, and then repeat the screen printing and sintering of the metal paste in the same manner.

[0019] Also, in the wiring board 1 according to the present embodiment, as shown in FIG. 1, the thickness H of the wiring layer 20 is larger than the closest distance L between the first wiring 20A and the second wiring 20B adjacent to each other. This is because, in the present embodiment, when manufacturing the patterned metal paste sintered layer 24, in addition to being able to increase the thickness of the metal paste sintered layer 24 by repeatedly laminating the metal paste by screen printing, since an etching process is not required when forming the metal paste sintered layer 24 in a wiring pattern shape, dissolution of each wiring can be suppressed, and the distance from other adjacent pattern wirings does not increase. As a result, in the present embodiment, a wiring board 1 in which thick wirings are formed at high density, specifically, a wiring layer in which the wiring pitch is close to less than 1 / 2 of the thickness of the wiring layer, for example, a wiring pitch of 1 / 3 or less of the wiring thickness, or 1 / 4 or less of the wiring thickness, or a wiring board 1 in which the wiring pitch is close in the range from less than 1 / 4 to about 1 / 6 of the wiring thickness can be provided. For example, in the present embodiment, it is possible to provide a wiring having a thickness of 300 μm with a wiring pattern in which the closest distance between adjacent wirings is 100 μm or less, for example, a closest distance of 50 μm. In the present embodiment, a plating layer 23 is formed on the upper surface of the nickel alloy layer 22 by plating, and a metal paste sintered layer 24 is formed thereon. Compared with the case where the metal paste sintered layer 24 is directly formed on the nickel alloy layer 22, the adhesion of the metal paste sintered layer 24 can be enhanced. In particular, when the same metal is the main component in the plating layer 23 and the metal paste sintered layer 24, when the metal paste sintered layer 24 is sintered, the metal paste sintered layer 24 is integrated with the plating layer 23, so that the adhesion of the metal paste sintered layer 24 to the plating layer 23 can be enhanced.

[0020] [Manufacturing Method] Next, with reference to FIG. 2, a method for manufacturing the wiring board 1 according to the present embodiment will be described. FIG. 2 is a diagram for explaining the method for manufacturing the wiring board 1 according to the present embodiment. In the following, a wiring board 1 having an aluminum nitride substrate as the insulating layer 10, a nickel / titanium layer as the nickel alloy layer 22, a copper plating layer as the plating layer 23, and a copper paste sintered layer as the metal paste sintered layer 24 will be exemplified and described.

[0021] As shown in FIG. 2(A), first, the insulating layer 10 is prepared. In the present embodiment, a sintered aluminum nitride substrate is prepared as the insulating layer 10. Then, as shown in FIG. 2(B), a titanium layer 21 is formed by sputtering a material containing titanium particles over the entire wiring region on the upper surface of the prepared insulating layer 10. Next, as shown in FIG. 2(C), a nickel / titanium alloy layer is formed as the nickel alloy layer 22 by sputtering a material containing titanium particles and nickel particles over the entire wiring region on the upper surface of the titanium layer 21. Further, as shown in FIG. 2(D), using the nickel alloy layer 22 as a seed layer, electrolytic copper plating is performed to form an electrolytic copper plating layer as the plating layer 23 over the entire wiring region on the upper surface of the nickel alloy layer 22. Note that the above-described sputtering process and plating process can be performed by known methods.

[0022] Subsequently, as shown in FIG. 3(A), a copper paste is screen-printed in a wiring pattern on the plating layer 23 and laminated and sintered to form a metal paste sintered layer 24. In the present embodiment, a thick metal paste layer is formed by repeating a plurality of times the formation of a metal paste layer having a film thickness of several tens of μm in one screen printing, and by performing sintering, for example, the thickness of the wiring layer 20 can be made 300 μm or more. Note that, as will be described later, since the upper surface of the formed metal paste layer is dissolved by an etching process, it is necessary to form a metal paste layer with an additional thickness corresponding to the thickness dissolved by the etching process.

[0023] In FIGS. 2(B) to 2(D), for the sputtering process and the plating process, the titanium layer 21, the nickel alloy layer 22, and the plating layer 23 are formed over the entire wiring region on the upper surface of the insulating layer 10. In contrast, in FIG. 3(A), the metal paste sintered layer 24 can be formed in the wiring pattern shape of the wiring layer 20 by screen printing. Subsequently, in FIGS. 3(B) to 3(D), the titanium layer 21, the nickel alloy layer 22, and the plating layer 23 formed over the entire insulating layer 10 are removed according to the wiring pattern of the wiring layer 20.

[0024] That is, first, as shown in FIG. 3(B), by the etching process (copper etching in this embodiment) of the plating layer 23, the exposed portions of the plating layer 23 where the metal paste sintered layer 24 is not laminated are removed. When the plating layer 23 and the metal paste sintered layer 24 are layers mainly composed of copper particles, by performing copper etching, the metal paste sintered layer 24 is also dissolved together with the plating layer 23. However, since the metal paste sintered layer 24 is thicker than the plating layer 23 (having a thickness more than twice that of the plating layer 23), even when the exposed portions of the plating layer 23 are removed, the metal paste sintered layer 24 remains in a state thicker than the plating layer 23 at the lower part of the metal paste sintered layer 24.

[0025] Next, as shown in FIG. 3(C), by performing the etching process of the nickel alloy layer 22 (nickel / titanium etching in this embodiment) and then the etching process of the titanium layer 21, the wiring layer 20 can be formed according to the wiring pattern. Thereby, as shown in FIG. 3(D), the wiring substrate 1 having a predetermined wiring pattern can be manufactured on the insulating layer 10.

[0026] As described above, the wiring board 1 according to the present embodiment is a wiring board 1 having an insulating layer 10 and a wiring layer 20. The wiring layer 20 includes a titanium layer 21 mainly composed of titanium formed on the insulating layer 10, a nickel alloy layer 22 mainly composed of nickel and a metal other than nickel formed on the titanium layer 21, a plating layer 23 formed by plating on the nickel alloy layer 22, and a metal paste sintered layer 24 formed on the plating layer. In particular, since the wiring board 1 according to the present embodiment has a metal paste sintered layer 24 formed by applying and sintering a metal paste in a wiring pattern by screen printing, a thick wiring capable of passing a large current can be efficiently manufactured only by repeating screen printing.

[0027] That is, conventionally, when forming a thick wiring, a method of repeating exposure, development, and sintering of a photosensitive conductive material or a method of laminating a plating film by repeating plating and etching processes has been used. However, in the former method, it is necessary to repeat a plurality of processes such as exposure, development, and sintering of the photosensitive conductive material, and in the latter method, it is necessary to repeat a plurality of processes such as resist formation, plating, and etching processes, resulting in an increase in the number of processes and manufacturing time. On the other hand, in the present embodiment, when increasing the thickness of the wiring, it is only necessary to repeat the screen printing of the metal paste, and compared with the conventional method, the number of processes and manufacturing time can be reduced, and thick wiring can be efficiently manufactured.

[0028] In addition, in the conventional method of repeatedly performing plating and etching processes to laminate plating films, by repeatedly performing the etching process, the side surfaces of the wirings are dissolved, and the distance (distance L shown in FIG. 1) between another wiring layer 20 adjacent to the wiring layer 20 becomes long, resulting in a problem that the wiring layer 20 cannot be formed at a high density. In contrast, in the present embodiment, since the etching process for dissolving the metal paste sintered layer 24 is only performed once when etching the plating layer 23, dissolution of the side surfaces of the wiring layer 20 can be suppressed, and the circuit of the wiring layer 20 can be formed at a high density. Further, conventionally, when configuring a wiring layer using a copper plate, it has been difficult to align the copper plate on the substrate in some cases. However, in the present embodiment, by screen-printing a metal paste in a wiring pattern shape, the metal paste sintered layer 24 corresponding to the wiring pattern can be easily formed. In addition, in the present embodiment, compared with the case of applying a metal paste using a dispenser, by printing the metal paste in a wiring pattern shape by screen printing, the metal paste sintered layer 24 corresponding to the wiring pattern can be laminated at once, and it becomes possible to manufacture the wiring substrate 1 more efficiently.

[0029] In addition, in this embodiment, by forming a titanium layer 21, a nickel alloy layer 22, a plating layer 23, and a metal paste sintered layer 24 in this order on the insulating layer 10, even on the insulating layer 10 made of a ceramic material, the metal paste sintered layer 24 can be laminated with high adhesion. Here, even if a metal paste is directly laminated and sintered on the insulating layer 10 made of a ceramic material to form the metal paste sintered layer 24, the adhesion between the insulating layer 10 and the metal paste sintered layer 24 is low. Therefore, when the thickness of the wiring is increased, the metal paste sintered layer 24 may peel off from the insulating layer 10. On the other hand, the titanium layer 21 can enhance the adhesion between the insulating layer 10 and the titanium layer 21 by widely diffusing titanium into the insulating layer 10 made of a ceramic material. The nickel alloy layer 22 has high affinity between nickel and titanium in the titanium layer 21 and can suppress the oxidation of titanium on the layer surface, thereby enhancing the adhesion with the plating layer 23. Also, the plating layer 23 can enhance the adhesion with the metal paste sintered layer 24 by sintering integrally with the metal paste sintered layer 24. Moreover, by using the same metal as the main component of the plating layer 23 and the metal paste sintered layer 24, the adhesion between the plating layer 23 and the metal paste sintered layer 24 can be further enhanced. Therefore, in the wiring board 1 according to this embodiment, the adhesion of the metal paste sintered layer 24 is high, and it is possible to prevent the wiring layer 20 including the metal paste sintered layer 24 from peeling off from the insulating layer 10.

[0030] As described above, the preferred embodiment examples of the present invention have been described. However, the technical scope of the present invention is not limited to the description of the above embodiment examples. Various changes and improvements can be made to the above embodiment examples, and the forms with such changes or improvements are also included in the technical scope of the present invention.

[0031] For example, in the above-described embodiment, the configuration of forming the nickel alloy layer 22 as the seed layer is illustrated. However, the configuration is not limited to this. For example, instead of nickel, a palladium layer mainly composed of palladium and a metal other than palladium such as titanium or chromium can be formed.

Description of Symbols

[0032] 1…Wiring board 10…Insulating layer 20…Wiring layer 21…Titanium layer 22…Nickel alloy layer 23…Plated layer 24…Metal paste sintered layer

Claims

1. A wiring board having an insulating layer and a patterned wiring layer, The wiring layer is a titanium layer containing titanium as a main component formed on the insulating layer; a nickel alloy layer formed on the titanium layer and containing nickel and a metal other than nickel as main components; a plating layer formed on the nickel alloy layer by plating; and a metal paste sintered layer formed on the plating layer.

2. The wiring board according to claim 1 , wherein the metal paste sintered layer has a thickness of 300 μm or more.

3. the wiring layer includes a first wiring and a second wiring adjacent to the first wiring; The wiring board according to claim 1 , wherein the closest distance between the first wiring and the second wiring is less than half the thickness of the wiring layer.

4. The wiring board according to claim 3 , wherein the closest distance is 100 μm or less.

5. the metal paste sintered layer and the plating layer are mainly composed of metal particles made of the same metal, The wiring board according to claim 1 , wherein the metal paste sintered layer has a thickness at least twice as large as that of the plating layer.

6. The plating layer is a copper plating layer containing copper as a main component, The wiring board according to claim 1 , wherein the metal paste sintered layer is a copper paste sintered layer containing copper as a main component.

7. The wiring board according to claim 1 , wherein the insulating layer is a layer mainly containing aluminum nitride or silicon nitride.

8. 2. The wiring board according to claim 1, wherein the nickel alloy layer is a nickel / titanium alloy layer containing nickel and titanium as main components.

9. forming a titanium layer containing titanium as a main component on the insulating layer; forming a nickel alloy layer containing nickel and a metal other than nickel as main components on the titanium layer; forming a plating layer on the nickel alloy layer by plating; and forming a metal paste sintered layer by sintering a metal paste applied in a wiring pattern on the plating layer.

10. The method for manufacturing a wiring board according to claim 9 , wherein the metal paste sintered layer is formed by sintering the metal paste applied onto the plating layer by screen printing.

11. the wiring pattern includes a first wiring and a second wiring adjacent to the first wiring, 10. The method for manufacturing a wiring board according to claim 9, wherein a thickness of the first wiring and the second wiring is greater than a closest distance between the first wiring and the second wiring.

12. The method for manufacturing a wiring board according to claim 11 , wherein the closest distance is 100 μm or less.

13. 10. The method for manufacturing a wiring board according to claim 9, wherein after the metal paste sintered layer is formed into a wiring pattern, a step of etching the plating layer, a step of etching the nickel alloy layer, and a step of forming the titanium layer are sequentially performed, so that the wiring layer consisting of the titanium layer, the nickel alloy layer, the plating layer, and the metal paste sintered layer is shaped according to the wiring pattern.

Images