JP7498680B2 - Wiring Board - Google Patents

Description

The present invention relates to a wiring board having metal pads on its surface.

Some wiring boards on which electronic components such as semiconductor elements are mounted include a ceramic substrate made of ceramic, a non-conductive material, and metal pads (also called metallized layers) formed on the surface of the ceramic substrate using a conductive material. The metal pads are used as connection terminals for connecting to external electronic components and as pads for sealing rings for quartz crystal oscillators.

For example, Patent Document 1 discloses a wiring board having a copper metallized pad for connecting to a lead terminal on the surface of an insulating substrate made of a glass ceramic sintered body. In this wiring board, the peripheral portion of the copper metallized pad is embedded in the insulating substrate. Such a structure is formed, for example, by printing a paste containing a glass ceramic composition so as to cover the peripheral portion of the pattern of the copper metallized pad.

Japanese Patent Application Laid-Open No. 9-293956

When a paste containing a glass ceramic composition is applied to cover the periphery of a metal pad, such as in the wiring board disclosed in Patent Document 1, ceramic steps resulting from the paste are generated on the surface of the wiring board after firing. When a plating layer is formed on the metal pad of such a wiring board, it is not possible to form the plating layer on the entire surface of the metal pad, and there is a possibility that a gap will be formed between the end of the plating layer and the ceramic layer.

If a gap forms between the plating layer and the ceramic layer, the chemicals used in cleaning the surface of the wiring board after the plating process will seep into the metal pads below the plating layer. This can cause the metal components in the metal pads to denature, which is undesirable.

The present invention aims to provide a wiring board that can more reliably protect the metal pads located under the plating layer.

The wiring board according to one aspect of the present invention comprises a ceramic substrate, a metal pad provided on the surface of the ceramic substrate, and a plating layer provided on the metal pad. In this wiring substrate, a portion of the metal pad is embedded in the ceramic substrate, and another portion protrudes from the surface of the ceramic substrate, and the plating layer protrudes onto the surface of the ceramic substrate adjacent to the outer periphery of the metal pad and contacts the ceramic substrate.

The above configuration allows the outer periphery of the plating layer to be in close contact with the surface of the ceramic substrate, reducing the possibility that chemicals used in the manufacture of the wiring substrate will seep into the metal pads underneath the plating layer. This allows the metal pads underneath the plating layer to be more reliably protected.

In the wiring board according to one aspect of the present invention described above, the metal pad may have a tapered portion that tapers toward the surface of the ceramic substrate.

The above configuration makes it possible to make it difficult for the metal pad to come off the ceramic substrate.

In the wiring board according to one aspect of the present invention, the area where the plating layer is disposed may be larger than the area where the maximum diameter portion of the metal pad is disposed when viewed from above.

The above configuration allows the contact area between the outer peripheral edge of the plating layer and the surface of the ceramic substrate to be increased. This improves the adhesion strength of the plating layer to the ceramic substrate.

The wiring board according to one aspect of the present invention described above may further include a metal fitting disposed on the metal pad.

Here, the metal fittings include, for example, pins and studs that serve as connection terminals with external electronic components, as well as a seal ring for a quartz crystal oscillator. For example, by providing pins and studs on a metal pad, electrical connection with external electronic components can be easily achieved.

According to one aspect of the present invention, the wiring board can more reliably protect the metal pads located under the plating layer.

1 is a schematic cross-sectional view showing an internal configuration of a wiring board according to an embodiment of the present invention; 2 is a cross-sectional view showing the configuration of one of the connection pads provided on the wiring board shown in FIG. 1 . 2 is a top view showing the configuration of one of the connection pads provided on the wiring board shown in FIG. 1 . 4 is a flowchart showing a manufacturing process of a wiring board according to an embodiment of the present invention. 5A to 5C are schematic diagrams illustrating an exposure step and a development step in the manufacturing process shown in FIG. 4. 5 is a schematic diagram illustrating a transfer step in the manufacturing process shown in FIG. 4.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

In this embodiment, wiring board 1 will be described as an example of a wiring board according to the present invention. Wiring board 1 is used, for example, as a wiring board for mounting electronic components such as semiconductor elements and quartz oscillators, or as a wiring board for an electrostatic chuck. Wiring board 1 is provided with metal pads (e.g., connection pads 20) to which pins 50 serving as input/output terminals are connected. In the case of wiring board 1 on which a quartz oscillator is mounted, a seal ring is connected to the metal pad. Also, metal fittings such as pins 50 do not have to be attached to wiring board 1.

Figure 1 shows a cross-sectional structure of a portion of wiring board 1. Wiring board 1 is mainly composed of a ceramic substrate 11 and multiple conductive patterns.

The ceramic substrate 11 is a member that serves as the base of the wiring board 1. The ceramic substrate 11 can be formed of, for example, high-temperature fired ceramics containing alumina (Al ₂ O ₃ ) as a main component. In another embodiment, the ceramic sheet may be formed of medium-temperature fired ceramics (MTCC) such as alumina with improved sinterability, or low-temperature fired ceramics (LTCC).

The ceramic substrate 11 is obtained by firing one or more ceramic green sheets. When the ceramic substrate 11 is formed from multiple ceramic green sheets, the ceramic substrate 11 has multiple laminated ceramic layers. Figure 1 shows an example of a configuration in which the ceramic substrate 11 is formed from a single ceramic green sheet.

In this embodiment, for convenience, the surface of the substantially flat ceramic substrate 11 on which the connection pads 20 are provided is referred to as the front surface 11a, and the opposite surface is referred to as the back surface 11b. However, the definitions of the front surface and back surface of the ceramic substrate 11 are not limited to this and can be determined arbitrarily. In this embodiment, the surface direction of the ceramic substrate 11 is referred to as the X direction, and the thickness direction of the ceramic substrate 11 is referred to as the Y direction (see FIG. 2).

In the example shown in FIG. 1, the connection pads 20 are provided only on one side of the wiring board 1 (i.e., the front side 11a), but in another embodiment, the connection pads 20 may be provided on both sides of the wiring board 1 (i.e., the front side 11a and the back side 11b).

The conductive patterns are provided on the front surface 11a, rear surface 11b, and inside of the ceramic substrate 11. Each conductive pattern is formed into a predetermined shape and functions as, for example, wiring, vias, connection pads (specifically, metal pads 21), and electrodes.

The conductive pattern can be formed of, for example, a metal material such as copper (Cu), tungsten (W), silver (Ag), or molybdenum (Mo), or an alloy material mainly composed of these metal materials. When the ceramic substrate 11 is formed of high-temperature fired ceramic, it is preferable that the conductive pattern is mainly composed of, for example, tungsten (W) or molybdenum (Mo). When the ceramic substrate 11 is formed of medium-temperature fired ceramic or low-temperature fired ceramic, it is preferable that the conductive pattern is mainly composed of, for example, copper (Cu) or silver (Ag).

In the example shown in FIG. 1, two connection pads 20, which are an example of a conductive pattern, are provided on the front surface 11a of the ceramic substrate 11. However, the number of connection pads 20 provided on the wiring substrate 1 is not limited to this. Although not shown in FIG. 1, the wiring substrate 1 also has conductive patterns such as wiring, vias, and electrodes.

A pin (metal fitting) 50 is connected to the connection pad 20. The pin 50 is attached to the connection pad 20 by solder material 55.

The connection pad 20 is mainly composed of a metal pad 21 and a plating layer 30 provided on the metal pad 21.

The metal pad 21 is an example of a conductive pattern and is formed using the material described above. A part of the metal pad 21 (e.g., the columnar portion 21b and a part of the tapered portion 21a continuing from the columnar portion 21b) is embedded in the ceramic substrate 11, and another part (e.g., the top of the tapered portion 21a) protrudes from the surface 11a of the ceramic substrate 11.

The plating layer 30 is provided so as to cover the portion of the metal pad 21 protruding from the surface 11a. The plating layer 30 may be composed of a single plating layer, or may be composed of multiple plating layers. When the plating layer 30 is composed of multiple plating layers, the plating layer 30 includes, for example, a Ni plating layer 31 and an Au plating layer 32 (see FIG. 2). The plating layer 30 can be formed, for example, by using a conventionally known electrolytic plating method. By performing the electrolytic plating method, a plating film can be formed on the surface of the metal pad 21 exposed from the surface 11a of the ceramic substrate 11.

Figure 2 shows an enlarged view of one of the connection pads 20 provided on the wiring board 1 according to this embodiment. Also, Figure 3 is a top view of a portion of the wiring board 1 including a location where one of the connection pads 20 is formed. As described above, the connection pad 20 has a metal pad 21 and a plating layer 30.

The metal pad 21 has a generally circular shape when viewed from above. As shown in FIG. 2, the metal pad 21 has a tapered portion 21a and a columnar portion 21b. In FIG. 2, a dashed line is drawn at the boundary between the tapered portion 21a and the columnar portion 21b. The tapered portion 21a is located on the surface side of the ceramic substrate 11 (surface 11a in FIG. 2, etc.).

The tapered portion 21a tapers toward the surface 11a of the ceramic substrate 11. That is, the tapered portion 21a has a shape in which the cross-sectional area in the surface direction (X direction) of the ceramic substrate 11 increases toward the inside of the ceramic substrate 11. In this embodiment, the cross-sectional shape of the tapered portion 21a in the surface direction (X direction) is approximately circular.

The columnar portion 21b is located on the inside of the ceramic substrate 11. Although not shown, the columnar portion 21b may be in contact with a via or wiring arranged inside the ceramic substrate 11. The cross-sectional shape of the columnar portion 21b along the surface direction (X direction) of the ceramic substrate 11 is approximately constant in the thickness direction (Y direction) of the ceramic substrate 11. In this embodiment, the cross-sectional shape of the columnar portion 21b along the surface direction (X direction) is approximately circular.

In this embodiment, when the metal pad 21 is viewed in cross section in the Y direction (thickness direction), the maximum diameter portion (corresponding to the columnar portion 21b in this embodiment) where the width of the metal pad 21 in the X direction (surface direction) is maximum is located inside the ceramic substrate 11.

The metal pad 21 has such a shape that it is difficult for the metal pad 21 to come off the ceramic substrate 11.

As shown in FIG. 2, at least a portion of the metal pad 21 is embedded in the ceramic substrate 11. Another portion of the metal pad 21 (specifically, the top) protrudes from the surface 11a of the ceramic substrate 11.

Specifically, more than half of the dimension of the metal pad 21 in the thickness direction perpendicular to the surface 11a of the ceramic substrate 11 is embedded in the ceramic substrate 11. In other words, as shown in FIG. 2, if the dimension of the metal pad 21 in the thickness direction is H and the dimension of the part of the metal pad 21 embedded in the ceramic substrate 11 (the part below the imaginary extension plane (shown by the dashed line) of the surface 11a of the ceramic substrate 11) in the thickness direction is H1, then H1>1/2×H.

It can also be said that more than 50% of the total surface area of the metal pad 21 is embedded in the ceramic substrate 11. With this configuration, the surface area of the portion of the metal pad 21 embedded in the ceramic substrate 11 (the portion below the surface 11a of the ceramic substrate 11) is larger than the surface area of the portion protruding from the surface 11a of the ceramic substrate 11. In this way, by increasing the surface area of the portion of the metal pad 21 embedded in the ceramic substrate 11, the heat transfer from the metal pad 21 to the ceramic substrate 11 can be improved.

In addition, the proportion of the metal pad 21 that is buried in the ceramic substrate 11 is preferably 60% or more of the thickness dimension H of the metal pad 21, and more preferably 70% or more.

In addition, by having a portion of the metal pad 21 (specifically, the top) protruding from the surface 11a of the ceramic substrate 11, the area of the plating layer 30 provided to cover the metal pad 21 that contributes to bonding with metal fittings such as the pin 50 can be increased. This allows metal fittings such as the pin 50 placed on the connection pad 20 to be fixed in a more stable state. In light of this, it is preferable that the amount by which the top of the metal pad 21 protrudes from the surface 11a is 5% or more of the dimension H in the thickness direction of the metal pad 21.

The plating layer 30 is provided so as to cover the surface of the metal pad 21 protruding from the surface 11a of the ceramic substrate 11. In this embodiment, the plating layer 30 has a laminated structure in which a Ni plating layer 31 and an Au plating layer 32 are laminated. Specifically, it is preferable that the Ni plating layer 31 is provided so as to cover the surface of the metal pad 21, and the Au plating layer 32 is provided so as to cover the Ni plating layer 31. This allows the surface of the connection pad 20 to be covered with the chemically more stable Au plating layer 32.

As shown in FIG. 2, the plating layer 30 extends onto the surface 11a of the ceramic substrate 11 adjacent to the outer periphery of the metal pad 21 and is in contact with the surface 11a of the ceramic substrate 11.

This allows the outer periphery of the plating layer 30 to be in close contact with the surface 11a of the ceramic substrate 11. This reduces the possibility that the chemicals used in manufacturing the wiring substrate 1 (e.g., the chemicals used to clean the surface of the wiring substrate 1 after a plating process, etc.) will seep into the metal pads 21 underneath the plating layer 30. This allows the metal pads 21 underneath the plating layer 30 to be more reliably protected.

In this embodiment, the arrangement area of the plating layer 30 is larger than the arrangement area of the maximum diameter portion of the metal pad 21 (in this embodiment, the columnar portion 21b) when viewed from above the wiring board 1 (see FIG. 3). That is, the size of the plating layer 30 in the X direction (plane direction) (corresponding to the diameter D2 of the plating layer 30 in this embodiment) is larger than the size of the maximum diameter portion of the metal pad 21 in the X direction (plane direction) (corresponding to the diameter D1 of the columnar portion 21b in this embodiment) (see FIGS. 2 and 3). In addition, when viewed from above the wiring board 1, the arrangement area of the maximum diameter portion of the metal pad 21 exists within the arrangement area of the plating layer 30 (see FIG. 3).

This configuration makes it possible to increase the contact area with the surface 11a of the ceramic substrate 11 at the outer periphery of the plating layer 30 located outside the area where the metal pad 21 is arranged when viewed from above. This improves the adhesion strength of the plating layer 30 to the ceramic substrate 11. This results in a connection pad 20 that is less likely to peel off from the substrate.

Next, a method for manufacturing the wiring board 1 will be described. Here, the process for forming the connection pads 20 on the ceramic substrate 11 will be mainly described. For the manufacturing method of the wiring board 1 other than this process, a conventionally known method for manufacturing wiring boards can be applied.

Figure 4 shows part of the manufacturing process for wiring board 1 in the order of steps. Figure 4 mainly shows each step from the pattern formation step (S10) to the plating step (S40).

Figure 5 shows the process of forming a pattern (S10) for forming a conductive pattern for the metal pad 21 in the order of steps. Figure 6 shows the process of transferring the conductive pattern for the metal pad 21 to the ceramic sheet 10 in the order of steps.

4, first, a ceramic sheet 10 is prepared. The ceramic sheet 10 is obtained by kneading a powder of a ceramic material containing, for example, alumina (Al ₂ O ₃ ) or the like with an organic solvent and a binder to prepare a slurry, and then forming the slurry into a sheet.

After preparing the ceramic sheet 10, a conductive pattern for vias is formed at a predetermined location in the ceramic sheet 10 as necessary. In the process of forming the conductive pattern for vias, through holes are formed at predetermined positions in the ceramic sheet 10 (positions where vias will be formed) and conductive paste is embedded in the through holes. This forms areas that will become vias at predetermined positions in the ceramic sheet 10.

Next, the pattern formation process (S10) is performed. Figure 5 shows a schematic diagram of how the pattern formation process (S10) is performed. The pattern formation process (S10) includes an exposure process (S11) and a development process (S12). Figure 5 shows the exposure process (S11) and the subsequent development process (S12) in the order of steps A to C.

When performing the exposure process (S11), first prepare a carrier film 61 and a photosensitive conductive paste 62. As the carrier film 61, for example, a transparent film made of a resin such as PEN (polyethylene naphthalate) or PET (polyethylene terephthalate) can be used.

The conductive paste 62 contains a metal powder containing, for example, copper (Cu), tungsten (W), silver (Ag), or molybdenum (Mo), and a photosensitive resin. The photosensitive resin used is a negative photosensitive material that is photocured when irradiated with ultraviolet light. By including a photosensitive resin in the conductive paste, a conductive pattern of a predetermined shape can be formed by photolithography. Therefore, a conductive pattern having a more precise pattern shape can be formed, compared to, for example, forming a conductive pattern by screen printing.

The conductive paste 62 is applied onto the carrier film 61. The conductive paste 62 can be applied using a conventionally known screen printing device or the like. This results in a conductive paste-adhered film body (hereinafter referred to as the film body).

In the exposure process (S11), light L is irradiated onto the conductive paste 62 applied to the carrier film 61 using an exposure device equipped with, for example, a UV light source.

In the exposure process (S11), light L is irradiated onto the conductive paste 62 on the carrier film 61 using a glass mask 70, and the photosensitive resin in the conductive paste 62 is photocured according to the pattern shape of the metal pads 21 formed on the wiring board 1. In FIG. 5, the surface of the conductive paste 62 farther from the carrier film 61 is the first surface 62a, and the surface in contact with the carrier film 61 is the second surface 62b.

In the exposure process (S11), a glass mask 70 is placed above the conductive paste 62. The glass mask 70 has a flat glass 71 on which a light-shielding film 72 is provided in accordance with the shape of the conductive pattern 25 to be formed. In the exposure process, the conductive paste 62 on the carrier film 61 is irradiated through the glass mask 70 with light L (e.g., ultraviolet light) that photocures the photosensitive resin contained in the conductive paste 62.

Thereby, the light L is irradiated onto the conductive paste 62 in the area where the light-shielding film 72 is not provided, while the light L is not irradiated onto the conductive paste 62 in the area where the light-shielding film 72 is provided. As a result, in the conductive paste 62 on the carrier film 61, only the photosensitive resin present in the area irradiated with the light L is photocured, and the photosensitive resin present in the area where the light is blocked by the light-shielding film 72 remains on the carrier film 61 without being photocured.

When light L is irradiated in this manner, the light is scattered by the metal powder contained in the conductive paste 62, and therefore some of the irradiated light L does not reach the conductive paste 62 on the side closer to the carrier film 61 (i.e., the second surface 62b side). As a result, the photocuring of the photosensitive resin in the conductive paste 62 on the side closer to the carrier film 61 (i.e., the second surface 62b side) tends to be inhibited.

That is, the area of the conductive paste 62 that is photocured becomes narrower as it moves away from the side where the light L is incident (i.e., the first surface 62a side). As a result, a photocured area 25A is formed in the conductive paste 62 that has a shape that tapers toward the contact surface with the carrier film 61.

Then, a development process (S12) is performed. In the development process (S12), a conductive pattern 25 is formed on the carrier film 61. Specifically, the conductive paste 62 is treated with a developer to remove the unexposed portions of the conductive paste 62. As a result, only the photocured areas of the conductive paste 62 remain on the carrier film 61, and the conductive pattern 25 is formed on the carrier film 61 (see process C in FIG. 5). The conductive pattern 25 has a tapered portion 21a located on the carrier film 61 side and a columnar portion 21b located on the side farther from the carrier film 61.

The pattern formation process (S10) is carried out in this manner. This results in the formation of a conductive pattern 25 of a predetermined shape on the carrier film 61.

Then, the transfer step (S20) is performed. FIG. 6 shows a schematic diagram of the transfer step (S20). In the transfer step (S20), the conductive pattern 25 formed in the pattern formation step (S10) is transferred to the prepared ceramic sheet 10, and the conductive pattern 25 is arranged on the ceramic sheet 10.

Specifically, as shown in step A of FIG. 6, an adhesive solvent 75 (e.g., an alcohol-based solvent) is applied to the surface of the ceramic sheet 10, and a portion of the ceramic sheet 10 is turned into a paste. Here, the adhesive material is applied to the surface 10a (corresponding to the surface 11a of the ceramic substrate 11) side of the ceramic sheet 10, and a portion of the ceramic sheet is turned into a paste. In FIG. 6, the pasted ceramic portion of the ceramic sheet 10 is indicated as 10c.

Next, as shown in step B of FIG. 6, the carrier film 61 is placed on the surface 10a of the ceramic sheet 10 with the surface on which the conductive pattern 25 is formed facing the ceramic sheet 10, and pressure and heat are applied using a heat press device 76.

Then, as shown in step C of FIG. 6, the carrier film 61 is peeled off, and the conductive pattern 25 is transferred to the ceramic sheet 10. Here, at least a portion of the conductive pattern 25 is embedded in the ceramic sheet 10.

In this way, a conductive pattern 25 for the metal pad 21 is formed on the ceramic sheet 10.

In the case of a wiring board 1 having multiple ceramic layers, multiple ceramic sheets 10 are formed using the method described above, and then the sheets are stacked in a predetermined order.

Then, a firing step (S30) is performed. In the firing step (S30), the ceramic sheet 10 on which the conductive pattern 25 is formed, or the laminate thereof, is co-fired (co-fired). As a result, the ceramic sheet 10 becomes the ceramic substrate 11. Note that by performing the firing step (S30), the photosensitive resin contained in the conductive pattern 25 is burned away.

After the firing step (S30) is completed, the plating step (S40) is performed. The plating step (S40) is performed, for example, by a conventionally known electrolytic plating method. By performing the electrolytic plating method, a plating film can be formed on the surface of the metal pad 21 exposed from the ceramic substrate 11.

In this plating step (S40), the plating process may be repeated multiple times by changing the components of the plating solution used. This allows a plating layer 30 having multiple plating layers (e.g., Ni plating layer 31 and Au plating layer 32, etc.) to be formed on the surface of the metal pad 21.

After the plating process (S40) is completed, post-processing steps such as cleaning are performed. In this manner, the wiring board 1 having the connection pads 20 is manufactured.

When metal fittings such as pins 50 are attached to the connection pads 20 as in the wiring board 1 shown in FIG. 1, the pins 50 are attached to the connection pads 20 by brazing after the plating step (S40) is completed. This results in a wiring board 1 having pins 50 fixed by the brazing material 55.

As described above, in the method for manufacturing the wiring board 1 according to this embodiment, the carrier film 61 coated with the photosensitive conductive paste 62 is exposed to light and developed to form the conductive pattern 25 having a shape that tapers toward the contact surface with the carrier film 61. This conductive pattern 25 is transferred to the ceramic sheet 10 to form the metal pad 21.

By forming the metal pads 21 using such a manufacturing method, it is possible to form finer metal pads 21. For example, according to the manufacturing method of this embodiment, it is possible to obtain a wiring board 1 equipped with highly fine metal pads 21 in which the diameter D1 of the metal pads 21 is about 30 μm and the spacing between adjacent metal pads 21 is about 60 μm.

In addition, in the exposure step (S11) of the above-mentioned pattern formation step (S10), a tapered portion 21a can be formed in the conductive pattern 25 by utilizing the characteristic that the photocured area of the conductive paste 62 becomes narrower as it moves away from the side where the light L is incident. This tapered portion 21a becomes the tapered portion 21a of the metal pad 21. By forming the tapered portion 21a of the metal pad 21 on the surface 11a side of the ceramic substrate 11, it is possible to make it difficult for the metal pad 21 to come off the ceramic substrate 11.

(Summary of the embodiment)
As described above, the wiring board 1 according to this embodiment includes the ceramic substrate 11, the metal pad 21 provided on the surface 11a of the ceramic substrate 11, and the plating layer 30 provided on the metal pad 21. The metal pad 21 and the plating layer 30 form the connection pad 20 for electrical connection to an external electronic component or the like. A part of the metal pad 21 is embedded in the ceramic substrate 11, and another part of the metal pad 21 protrudes from the surface 11a of the ceramic substrate 11. The plating layer 30 protrudes onto the surface 11a of the ceramic substrate 11 adjacent to the outer periphery of the metal pad 21, and is in contact with the ceramic substrate 11.

In the above configuration, the entire protruding portion of the metal pad 21 from the surface of the ceramic substrate is covered with the plating layer 30. In other words, the plating layer 30 is provided so as to wrap around the protruding portion of the metal pad 21 and cover the outer peripheral end of the metal pad 21.

This allows the outer periphery of the plating layer 30 to be in close contact with the surface 11a of the ceramic substrate 11, reducing the possibility that the chemicals used in manufacturing the wiring substrate 1 will seep into the metal pads 21 underneath the plating layer 30. This allows the metal pads 21 underneath the plating layer 30 to be more reliably protected, and prevents the alteration of metals such as tungsten and molybdenum contained in the metal pads 21.

In addition, in the wiring board 1 according to this embodiment, the metal pad 21 is formed using a transfer method. This allows at least a portion of the metal pad 21 to be embedded in the ceramic substrate 11. This improves the adhesion strength of the metal pad 21 to the ceramic substrate 11. Therefore, after the metal pad 21 is formed on the ceramic substrate 11, it is possible to reduce the need to coat the outer periphery of the metal pad 21 with, for example, an alumina coat.

When the metal pad 21 is formed using the transfer method, the flatness of the surface of the metal pad 21 can be improved compared to when the metal pad 21 is formed using the screen printing method. Therefore, in the wiring board 1 according to this embodiment, when the metal pad 21 formed using the transfer method is used as the connection pad 20, the connection reliability with metal fittings such as the pin 50 arranged on the connection pad 20 can be improved.

In this embodiment, a pin pad for electrical connection (i.e., connection pad 20) is used as an example of a pad having a metal pad and a plating layer, but the use of the pad is not limited to electrical connection. In another embodiment, the pad having a metal pad and a plating layer can be used as a pad for a seal ring in a wiring board on which a quartz crystal oscillator or the like is mounted.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, configurations obtained by combining the configurations of the various embodiments described in this specification are also included in the scope of the present invention.

1: Wiring board 11: Ceramic board 11a: Surface (of ceramic board) 20: Connection pad 21: Metal pad 21a: Tapered portion (of metal pad) 21b: Columnar portion (maximum diameter portion of metal pad)
30: plating layer 50: pin (metal fitting)

Claims (2)

A ceramic substrate;
a metal pad provided on a surface of the ceramic substrate;
A wiring board including a plating layer provided on the metal pad,
a portion of the metal pad is embedded in the ceramic substrate and another portion of the metal pad protrudes from the surface of the ceramic substrate, and the metal pad has a tapered portion that tapers toward the surface of the ceramic substrate;
the plating layer extends onto a surface of the ceramic substrate adjacent to an outer periphery of the metal pad and contacts the ceramic substrate;
When viewed from above, an area where the plating layer is disposed is larger than an area where a maximum diameter portion of the metal pad is disposed.
Wiring board. The wiring board according to claim 1 , further comprising a metal fitting disposed on the metal pad .

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