JP2022146221A - wiring board - Google Patents

Abstract

To provide a wiring board capable of more surely protecting a metal pad provided under a plating layer.SOLUTION: A wiring board 1 includes a ceramic substrate 11, a metal pad 21 provided on the surface 11a of the ceramic substrate 11, and a plated layer 30 provided on the metal pad 21, and a part of the metal pad 21 is embedded in the ceramic substrate 11 and the other portion protrudes from the surface 11a of the ceramic substrate 11. The plated layer 30 protrudes from 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.SELECTED DRAWING: Figure 2

Description

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

As wiring boards on which electronic parts such as semiconductor elements are mounted, there are ceramic substrates made of non-conductive ceramics and metal pads (metallized layers) formed on the surface of ceramic substrates using conductive materials. also called). The metal pads are used as connection terminals with external electronic components, pads for sealing rings of crystal oscillators, and the like.

For example, Patent Literature 1 discloses a wiring board having a copper metallized pad for connection with a lead terminal on the surface of an insulating substrate made of a sintered glass ceramic. In this wiring board, the peripheral portion of the copper metallized pad is embedded in the insulating substrate. Such structures are formed, for example, by printing a paste containing a glass-ceramic composition so as to cover the perimeter of a pattern of copper metallization pads.

JP-A-9-293956

As in the wiring board disclosed in Patent Document 1, when a paste containing a glass ceramic composition is provided so as to cover the peripheral portion of the metal pad, the surface of the wiring board after firing has the paste originating from the paste. A ceramic step occurs. If a plated layer is formed on the metal pad of such a wiring board, the plated layer cannot be formed on the entire surface of the metal pad, and a gap may be formed between the edge of the plated layer and the ceramic layer. There is

If a gap is formed between the plated layer and the ceramic layer, a chemical solution used for cleaning the surface of the wiring board after the plating process will enter the metal pad under the plated layer. This may undesirably denature the metal component contained in the metal pad.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a wiring board capable of more reliably protecting the metal pads provided under the plating layer.

A wiring board according to one aspect of the present invention includes a ceramic substrate, a metal pad provided on the surface of the ceramic substrate, and a plated layer provided on the metal pad. In this wiring board, the metal pad is partly embedded in the ceramic substrate and the other part protrudes from the surface of the ceramic substrate, and the plated layer is formed on the outer periphery of the metal pad. It protrudes from the surface of the ceramic substrate adjacent to the portion and is in contact with the ceramic substrate.

According to the above configuration, the outer peripheral edge of the plating layer can be brought into close contact with the surface of the ceramic substrate, so that chemicals used in the manufacture of the wiring board can flow to the metal pad side of the lower layer of the plating layer. It can reduce the possibility of getting in. Therefore, it is possible to more reliably protect the metal pads provided under the plated layer.

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.

According to the above configuration, it is possible to obtain a configuration in which the metal pad is difficult to come off from the ceramic substrate.

In the above-described wiring board according to one aspect of the present invention, the arrangement area of the plated layer may be larger than the arrangement area of the maximum diameter portion of the metal pad when viewed from above.

According to the above configuration, the contact area with the surface of the ceramic substrate can be increased in the outer peripheral portion of the plated layer. Therefore, the adhesion strength of the plated layer to the ceramic substrate can be improved.

The wiring board according to one aspect of the present invention described above may further include metal fittings arranged on the metal pads.

Here, the metal fittings include, for example, pins and studs that serve as connection terminals with external electronic components, seal rings for crystal oscillators, and the like. For example, by providing pins, studs, and the like on the metal pads, electrical connection with external electronic components can be easily achieved.

According to the wiring board according to one aspect of the present invention, it is possible to more reliably protect the metal pads provided under the plating layer.

It is a cross-sectional schematic diagram which shows the internal structure of the wiring board concerning one Embodiment of this invention. 2 is a cross-sectional view showing one configuration of connection pads provided on the wiring substrate shown in FIG. 1; FIG. 2 is a top view showing one configuration of connection pads provided on the wiring board shown in FIG. 1; FIG. 4 is a flow chart showing a manufacturing process of a wiring board according to one embodiment of the present invention; 5 is a schematic diagram illustrating an exposure step and a development step in the manufacturing process shown in FIG. 4. FIG. 5 is a schematic diagram illustrating a transfer step in the manufacturing process shown in FIG. 4; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments 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 description thereof will not be repeated.

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

FIG. 1 shows a cross-sectional configuration of a portion of the wiring board 1. As shown in FIG. The wiring board 1 is mainly composed of a ceramic substrate 11 and a plurality of conductive patterns.

The ceramic substrate 11 is a member that serves as the base of the wiring substrate 1 . The ceramic substrate 11 can be made of, for example, high-temperature sintered ceramic containing alumina (Al ₂ O ₃ ) as a main component. In another embodiment, the ceramic sheets may be formed of medium temperature fired ceramics (MTCC) such as alumina with enhanced 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 a plurality of ceramic green sheets, the ceramic substrate 11 has a plurality of laminated ceramic layers. FIG. 1 shows a configuration example in which the ceramic substrate 11 is formed of one ceramic green sheet.

In this embodiment, 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 thereof is referred to as the back surface 11b. However, the definition of the front surface and the rear surface of the ceramic substrate 11 is not limited to this, and can be arbitrarily determined. In this embodiment, the surface direction of the ceramic substrate 11 is the X direction, and the thickness direction of the ceramic substrate 11 is the Y direction (see FIG. 2).

In the example shown in FIG. 1, the connection pads 20 are provided only on one surface (that is, the surface 11a) of the wiring board 1, but in another embodiment, the connection pads 20 are provided on both sides of the wiring board 1. (that is, the front surface 11a and the rear surface 11b).

The conductive pattern is provided on the surface 11a, the back surface 11b, the inside, and the like of the ceramic substrate 11. As shown in FIG. Each conductive pattern is formed in a predetermined shape, and functions, for example, as wiring, vias, connection pads (specifically, metal pads 21), and electrodes.

The conductive pattern can be formed of, for example, metal materials such as copper (Cu), tungsten (W), silver (Ag), or molybdenum (Mo), or alloy materials containing these metal materials as main components. . If the ceramic substrate 11 is made of high temperature sintered ceramic, the conductive pattern is preferably made mainly of tungsten (W) or molybdenum (Mo), for example. If the ceramic substrate 11 is made of medium-temperature-fired ceramic or low-temperature-fired ceramic, the conductive pattern preferably contains, for example, copper (Cu) or silver (Ag) as a main component.

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

A pin (metal fitting) 50 is connected to the connection pad 20 . Pins 50 are mounted on connection pads 20 by braze material 55 .

The connection pads 20 are mainly composed of metal pads 21 and plated layers 30 provided on the metal pads 21 .

The metal pad 21 is an example of a conductive pattern and is formed using the materials described above. Part of the metal pad 21 (for example, the columnar portion 21b and part of the tapered portion 21a that continues to the columnar portion 21b) is embedded in the ceramic substrate 11, and the other portion (for example, the tapered portion 21a) is embedded in the ceramic substrate 11. ) protrudes from the surface 11 a of the ceramic substrate 11 .

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

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

The metal pad 21 has a substantially 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, the boundary between the tapered portion 21a and the columnar portion 21b is indicated by a dashed line. The tapered portion 21a is located on the surface side of the ceramic substrate 11 (the surface 11a in FIG. 2 and the like).

Tapered portion 21 a tapers toward surface 11 a of ceramic substrate 11 . That is, the tapered portion 21 a has a shape in which the cross-sectional area in the plane direction (X direction) of the ceramic substrate 11 increases toward the inner side of the ceramic substrate 11 . In this embodiment, the cross-sectional shape of the tapered portion 21a in the planar direction (X direction) is substantially circular.

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

In this embodiment, when the metal pad 21 is viewed in cross section in the Y direction (thickness direction), the maximum diameter portion (in this embodiment, a columnar 21b) is located inside the ceramic substrate 11. As shown in FIG.

Since the metal pad 21 has such a shape, the metal pad 21 can be configured to be difficult to come off from the ceramic substrate 11 .

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

Specifically, the metal pad 21 is embedded in the ceramic substrate 11 in more than half of the dimension in the thickness direction perpendicular to the surface 11 a of the ceramic substrate 11 . That is, as shown in FIG. 2, the dimension in the thickness direction of the metal pad 21 is H, and the portion of the metal pad 21 embedded in the ceramic substrate 11 (an imaginary extended plane of the surface 11a of the ceramic substrate 11 (indicated by a dashed line) If the dimension H1 in the thickness direction of the portion below the slab is 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 . According to this configuration, the metal pad 21 is embedded in the ceramic substrate 11 more than the surface area of the portion protruding from the surface 11a of the ceramic substrate 11 (the portion below the surface 11a of the ceramic substrate 11). surface area becomes larger. In this way, the surface area of the portion of the metal pad 21 embedded in the ceramic substrate 11 is increased, so that heat transfer from the metal pad 21 to the ceramic substrate 11 can be improved.

The percentage of the metal pad 21 embedded in the ceramic substrate 11 is preferably 60% or more, more preferably 70% or more, of the dimension H of the metal pad 21 in the thickness direction.

A part (specifically, the top) of the metal pad 21 protrudes from the surface 11 a of the ceramic substrate 11 . It is possible to increase the area that contributes to bonding with As a result, metal fittings such as the pins 50 arranged on the connection pads 20 can be fixed in a more stable state. In view of this point, the amount of protrusion of the top portion of the metal pad 21 from the surface 11a is preferably 5% or more of the dimension H of the metal pad 21 in the thickness direction.

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

As shown in FIG. 2 and the like, the plated layer 30 protrudes from the surface 11a of the ceramic substrate 11 adjacent to the outer peripheral edge of the metal pad 21 and is in contact with the surface 11a of the ceramic substrate 11 .

As a result, the outer peripheral edge of the plated layer 30 is brought into close contact with the surface 11 a of the ceramic substrate 11 . Therefore, a chemical solution used when manufacturing the wiring board 1 (for example, a chemical solution used when cleaning the surface of the wiring board 1 after a plating process or the like) can enter the metal pad 21 side of the lower layer of the plating layer 30. can be reduced. Therefore, the metal pad 21 provided under the plated layer 30 can be protected more reliably.

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

According to this configuration, the contact area with the surface 11a of the ceramic substrate 11 can be increased in the outer peripheral portion of the plated layer 30 located outside the arrangement area of the metal pads 21 in top view. Therefore, the adhesion strength of the plated layer 30 to the ceramic substrate 11 can be improved. As a result, connection pads 20 that are more difficult to peel off from the substrate can be obtained.

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

FIG. 4 shows part of the manufacturing process of the wiring board 1 in order of process. FIG. 4 mainly shows each process from the pattern forming process (S10) to the plating process (S40).

FIG. 5 shows the pattern forming step (S10) for forming the conductive pattern for the metal pad 21 in order of steps. FIG. 6 schematically shows the transfer step (S30) of transferring the conductive pattern for the metal pad 21 to the ceramic sheet 10 in order of steps.

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

After preparing the ceramic sheet 10, conductive patterns for vias are formed at predetermined locations in the ceramic sheet 10, if necessary. In the step of forming a conductive pattern for vias, through holes are formed at predetermined positions (positions where vias are formed) in the ceramic sheet 10, and conductive paste is embedded in the through holes. As a result, a via region is formed at a predetermined position in the ceramic sheet 10 .

Subsequently, a pattern forming step (S10) is performed. FIG. 5 schematically shows how the pattern forming step (S10) is performed. The pattern formation step (S10) includes an exposure step (S11) and a development step (S12). FIG. 5 shows the exposure step (S11) and the subsequent development step (S12) in order from step A to step C. As shown in FIG.

Before performing the exposure step (S11), first, a carrier film 61 and a photosensitive conductive paste 62 are prepared. As the carrier film 61, for example, a transparent resin film such as PEN (polyethylene naphthalate) or PET (polyethylene terephthalate) can be used.

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

A conductive paste 62 is applied onto the carrier film 61 . The application of the conductive paste 62 can be performed using a conventionally known screen printer or the like. As a result, a conductive paste-attached film body (hereinafter referred to as a film body) is obtained.

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

In the exposure step (S11), a glass mask 70 is used to irradiate the conductive paste 62 on the carrier film 61 with light L, and the conductive paste 62 is exposed in accordance with the pattern shape of the metal pads 21 formed on the wiring board 1. The photosensitive resin inside is photo-cured. In FIG. 5, the surface of the conductive paste 62 farther from the carrier film 61 is defined as a first surface 62a, and the contact surface with the carrier film 61 is defined as a second surface 62b.

In the exposure step ( S<b>11 ), a glass mask 70 is arranged above the conductive paste 62 . In the glass mask 70, a light shielding film 72 is provided on a flat glass 71 in conformity with the shape of the conductive pattern 25 to be formed. In the exposure step, the conductive paste 62 on the carrier film 61 is irradiated through the glass mask 70 with light L (for example, ultraviolet light) for photocuring the photosensitive resin contained in the conductive paste 62 . .

As a result, the conductive paste 62 in the region where the light shielding film 72 is not provided is irradiated with the light L, while the conductive paste 62 in the region where the light shielding film 72 is provided is not irradiated with the light L. As a result, in the conductive paste 62 on the carrier film 61, only the photosensitive resin existing in the area irradiated with the light L is photocured, and the photosensitive resin existing in the area blocked by the light shielding film 72 is cured by the light. It remains on the carrier film 61 without curing.

Note that when the light L is irradiated in this way, the light is scattered by the metal powder contained in the conductive paste 62, so part of the irradiated light L is directed toward the side closer to the carrier film 61 (that is, the second side). It does not reach the conductive paste 62 on the second surface 62b side). Therefore, the photo-curing of the photosensitive resin in the conductive paste 62 on the side closer to the carrier film 61 (that is, on the side of the second surface 62b) tends to be hindered.

That is, the area of the conductive paste 62 that is photocured becomes narrower with distance from the side on which the light L is incident (that is, the side of the first surface 62a). As a result, the conductive paste 62 is formed with a photocured region 25A tapered toward the contact surface with the carrier film 61 .

After that, the development step (S12) is performed. In the developing step ( S<b>12 ), the conductive pattern 25 is formed on the carrier film 61 . Specifically, the conductive paste 62 is treated with a developer to remove unexposed portions of the conductive paste 62 . As a result, only the photocured region of the conductive paste 62 remains on the carrier film 61, and the conductive pattern 25 is formed on the carrier film 61 (see step C in FIG. 5). The conductive pattern 25 has a tapered portion 21 a located on the carrier film 61 side and a columnar portion 21 b located on the far side from the carrier film 61 .

The pattern forming step (S10) is performed as described above. Thereby, the conductive pattern 25 having a predetermined shape is formed on the carrier film 61 .

Subsequently, a transfer step (S20) is performed. FIG. 6 schematically shows how the transfer step (S20) is performed. In the transfer step (S20), the conductive pattern 25 formed in the pattern forming 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, the surface of the ceramic sheet 10 is coated with an adhesive solvent 75 (for example, an alcohol-based solvent) to turn part of the ceramic sheet 10 into a paste. Here, the bonding material is applied from the surface 10a (corresponding to the surface 11a of the ceramic substrate 11) side of the ceramic sheet 10, and part of the ceramic sheet is made into a paste. In FIG. 6, the pasted ceramic portion of the ceramic sheet 10 is indicated by 10c.

Next, as shown in step B of FIG. 6, the surface of the carrier film 61 on which the conductive pattern 25 is formed faces the ceramic sheet 10, and the carrier film 61 is placed on the surface 10a of the ceramic sheet 10 and heated. A pressing device 76 is used to apply pressure and heat.

Thereafter, as shown in step C of FIG. 6, the conductive pattern 25 is transferred to the ceramic sheet 10 by peeling off the carrier film 61 . Here, at least part of the conductive pattern 25 is embedded in the ceramic sheet 10 .

Thus, the ceramic sheet 10 is formed with conductive patterns 25 for the metal pads 21 .

In the case of the wiring board 1 having a plurality of ceramic layers, after forming a plurality of ceramic sheets 10 by the above method, the sheets are laminated in a predetermined order.

After that, a baking 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 the photosensitive resin contained in the conductive pattern 25 is burned out by performing the baking step (S30).

After the baking process (S30) is completed, the plating process (S40) is performed. The plating step (S40) is performed, for example, by a conventionally known electroplating method. A plating film can be formed on the surfaces of the metal pads 21 exposed from the ceramic substrate 11 by performing the electrolytic plating method.

In this plating step (S40), the plating process may be repeated multiple times by changing the components of the plating solution used. Thereby, the plated layer 30 having a plurality of plated layers (for example, the Ni plated layer 31 and the Au plated layer 32, etc.) can be formed on the surface of the metal pad 21 .

After the plating step (S40) is finished, a post-treatment step such as cleaning is performed. As described above, the wiring board 1 having the connection pads 20 is manufactured.

In the case where metal fittings such as pins 50 are attached to the connection pads 20 as in the wiring board 1 shown in FIG. 20. As a result, wiring board 1 having pins 50 fixed by brazing material 55 is obtained.

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

By forming the metal pad 21 using such a manufacturing method, a finer metal pad 21 can be formed. For example, according to the manufacturing method of the present embodiment, the wiring substrate is provided with high-definition metal pads 21 in which the diameter D1 of the metal pads 21 is about 30 μm and the interval between the adjacent metal pads 21 is about 60 μm. 1 can be obtained.

In the exposure step (S11) of the pattern formation step (S10) described above, the photo-cured region of the conductive paste 62 becomes narrower as it moves away from the side on which the light L is incident. A tapered portion 21a may be formed in the elastic pattern 25 . This tapered portion 21 a becomes the tapered portion 21 a of the metal pad 21 . Since the metal pad 21 is formed with the tapered portion 21 a on the side of the surface 11 a of the ceramic substrate 11 , the metal pad 21 can be made difficult to come off from the ceramic substrate 11 .

(Summary of embodiment)
As described above, the wiring board 1 according to the present embodiment includes the ceramic substrate 11, the metal pads 21 provided on the surface 11a of the ceramic substrate 11, and the plated layers 30 provided on the metal pads 21. I have. The metal pads 21 and the plated layers 30 form connection pads 20 for electrical connection with external electronic components and the like. A portion of the metal pad 21 is embedded in the ceramic substrate 11 and the other portion protrudes from the surface 11 a of the ceramic substrate 11 . The plated layer 30 protrudes from the surface 11 a 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 projecting portion of the metal pad 21 from the surface of the ceramic substrate is covered with the plated layer 30 . That is, the plated layer 30 is provided so as to cover the outer peripheral edge of the metal pad 21 and wrap around the projecting portion of the metal pad 21 .

As a result, the outer peripheral edge of the plating layer 30 is brought into close contact with the surface 11a of the ceramic substrate 11, so that the chemical solution used in manufacturing the wiring board 1 flows to the metal pad 21 side of the lower layer of the plating layer 30. It can reduce the possibility of getting in. Therefore, the metal pad 21 provided under the plated layer 30 can be more reliably protected, and denaturation of metal such as tungsten and molybdenum contained in the metal pad 21 can be suppressed.

Moreover, in the wiring board 1 according to this embodiment, the metal pads 21 are formed using a transfer method. Thereby, at least part of the metal pad 21 can be embedded in the ceramic substrate 11 . Thereby, the adhesion strength of the metal pad 21 to the ceramic substrate 11 can be improved. Therefore, after the metal pads 21 are formed on the ceramic substrate 11, it is possible to reduce the necessity of coating the outer periphery of the metal pads 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 as compared with the case where the metal pad 21 is formed using the screen printing method. Therefore, in the wiring board 1 according to the present embodiment, if the metal pads 21 formed using the transfer method are used as the connection pads 20, the connection reliability with the metal fittings such as the pins 50 arranged on the connection pads 20 is improved. can be improved.

In this embodiment, a pin pad for electrical connection (that is, the connection pad 20) has been exemplified as a pad having a metal pad and a plated layer, but the use of the pad is not limited to that for electrical connection. . In another embodiment, a pad having a metal pad and a plated layer can be used as a pad for a seal ring in a wiring board on which a crystal oscillator or the like is mounted.

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

Reference Signs List 1: wiring board 11: ceramic substrate 11a: surface 20 (of ceramic substrate): connection pad 21: metal pad 21a: tapered portion 21b (of metal pad): columnar portion (maximum diameter portion of metal pad)
30: plating layer 50: pin (metal fitting)

Claims (4)

a ceramic substrate;
a metal pad provided on the surface of the ceramic substrate;
A wiring board comprising a plated layer provided on the metal pad,
a part of the metal pad is embedded in the ceramic substrate and the other part protrudes from the surface of the ceramic substrate;
The plated layer protrudes from the surface of the ceramic substrate adjacent to the outer peripheral edge of the metal pad and is in contact with the ceramic substrate.
wiring board. 2. The wiring substrate according to claim 1, wherein said metal pad has a tapered portion that tapers toward the surface of said ceramic substrate. 3. The wiring board according to claim 2, wherein an arrangement area of said plated layer is larger than an arrangement area of a maximum diameter portion of said metal pad when viewed from above. 4. The wiring board according to claim 1, further comprising metal fittings arranged on said metal pads.

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