JP2022106325A - Wiring board and method of manufacturing wiring board - Google Patents

Abstract

To provide a wiring board that can suppress a deviation between wiring and a via and makes the via hardly come out from a ceramic substrate.SOLUTION: A wiring board 1 comprises a ceramic substrate 11, at least one conductive via 31, and a wiring part 21 electrically connected to the via 31. The via 31 is embedded in the ceramic substrate 11. The wiring part 21 is provided at least in the ceramic substrate or on its surface. The via 31 has a hollow part 33 which decreases in area in a surface direction X orthogonal to a thickness direction Y toward the wiring part 21, at a connection part of the ceramic substrate 11 for the wiring part 21 in the thickness direction Y of the ceramic substrate 11.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wiring board provided with a ceramic substrate and a method for manufacturing the same.

As a wiring board on which electronic components such as semiconductor elements are mounted, a ceramic substrate made of ceramic, which is a non-conductive material, and a conductive material such as metal are formed inside and on the surface of the ceramic substrate. Some have a conductive pattern. The conductive pattern formed on the wiring board functions as, for example, wiring, vias, connection terminals, and the like. The via is provided so as to penetrate the inside of the ceramic substrate. For example, the wiring layer formed in the lower layer of the substrate and the connection terminal (connection pad) provided in the upper surface of the substrate are electrically connected to each other. Connecting.

In such a wiring board, if the wiring and the via are formed in different processes, a deviation occurs between the wiring formation position and the via formation position, and a connection failure occurs between the wiring and the via. There is. Such poor connection may occur due to the difference in shrinkage rate during firing between the conductive material forming the wiring and the conductive material forming the via. Therefore, Patent Document 1 discloses a method for manufacturing a multilayer ceramic substrate, which comprises a conductor film and a via hole conductor which do not shrink due to firing and therefore have high connection reliability.

Japanese Unexamined Patent Publication No. 2003-347731

In Patent Document 1, a metal foil 17 is integrally provided on a support 16 with a sheet-like portion 18 serving as a conductor film 14 and a bump portion 19 serving as a via hole conductor 15, and the bump portion 19 of the metal foil 17 is formed. The metal foil 17 was transferred from the support 16 to the ceramic green sheet 20 so that the ceramic green sheet 20 was plunged in the thickness direction of the ceramic green sheet 20, and then a plurality of ceramic green sheets 20 were laminated to obtain the raw material. A method for manufacturing a multilayer ceramic substrate is disclosed in which a multilayer ceramic substrate 11 is obtained by firing the laminate 23 of the above.

However, the vias formed by plunging the metal leaf bumps into the ceramic green sheet using this manufacturing method may fall off from the ceramic substrate, causing the vias to peel off.

Therefore, an object of the present invention is to provide a wiring board capable of suppressing the occurrence of misalignment between the wiring and the via and making it difficult for the via to come out from the ceramic substrate.

The wiring board according to one aspect of the present invention is provided on at least one of the ceramic substrate and at least one conductive via, the via embedded in the ceramic substrate, and the inside and the surface of the ceramic substrate. The via is provided with a wiring portion that is electrically connected to the via. In this wiring board, the via is a constricted portion in a connection portion with the wiring portion in the thickness direction of the ceramic substrate, in which the area in the plane direction orthogonal to the thickness direction becomes smaller toward the wiring portion. Have.

According to the above configuration, the via is embedded in the ceramic substrate, and a narrowed portion is provided at the connection portion with the wiring portion in the thickness direction of the ceramic substrate. As a result, the adhesion of the via to the ceramic substrate is improved, and the via can be prevented from coming off from the ceramic substrate.

In the wiring board according to one aspect of the present invention, the wiring portion is formed on the surface of the ceramic substrate, and at least a part thereof is embedded in the ceramic substrate. The embedded portion may be provided with a second constricted portion in which the area in the plane direction decreases as the via approaches.

According to the above configuration, at least a part of the wiring portion is embedded in the ceramic substrate, and a second constricted portion is provided in the portion of the wiring portion embedded in the ceramic substrate. .. As a result, the adhesion of the wiring portion to the ceramic substrate is improved, and the wiring portion can be hard to be peeled off from the ceramic substrate.

In the wiring board according to one aspect of the present invention, the second narrowed portion may be provided at a portion of the ceramic substrate adjacent to the via in the thickness direction.

According to the above configuration, the via and the wiring portion can be joined by the narrowed portion provided in the via and the second narrowed portion provided in the wiring portion. Such a configuration can be formed by a method of forming the via and the wiring portion in one development step. Therefore, the relative positional relationship between the via and the wiring portion can be easily defined, and the positional deviation between the via and the wiring portion can be suppressed.

In the wiring board according to one aspect of the present invention, the surface of the wiring portion may be flush with the surface of the ceramic substrate.

According to the above configuration, it is possible to obtain a wiring portion that is more difficult to peel off from the ceramic substrate.

Further, the method for manufacturing a wiring substrate according to another aspect of the present invention includes a film body forming step of applying a photosensitive conductive paste on a film to form a conductive paste-attached film body, and the film side. The first exposure step of exposing the film body from the above, and the second exposure step of exposing the film body from the conductive paste side after the first exposure step, and the first exposure step. By developing the film body that has undergone the exposure step and the second exposure step, the conductive paste on the side close to the film becomes a conductive pattern of the wiring portion, and the conductive paste on the side far from the film becomes vias. The film body that has undergone the development step is pressed against the development step and the ceramic sheet having at least holes at the locations where the vias are arranged, which becomes the conductive pattern of the above, and the wiring portion and the vias are said to be the same. The process includes a transfer step of transferring the conductive pattern to the ceramic sheet, and a firing step of firing the ceramic sheet after the transfer step.

According to the above manufacturing method, the relative positional relationship between the via and the wiring portion is easily defined by forming the via and the wiring portion from the photosensitive conductive paste provided on one sheet of film. can do. Therefore, it is possible to suppress the misalignment of the wiring pattern with respect to the via, which may occur when the via and the wiring portion are formed by different development steps using different conductive pastes.

Further, according to the above manufacturing method, a narrowed portion can be formed at the connecting portion between the via and the wiring portion. By forming such a narrowed portion, it is possible to make it difficult for the via to come out of the ceramic substrate.

According to the wiring board according to one aspect of the present invention, since the via is provided with the narrowed portion, it is possible to prevent the via from coming off from the ceramic substrate. Further, according to the method for manufacturing a wiring board according to another aspect of the present invention, a wiring board capable of suppressing the occurrence of misalignment between the wiring portion and the via and making it difficult for the via to come out from the ceramic substrate is manufactured. can do.

It is a top view which shows the structure of a part of the wiring board which concerns on one Embodiment of this invention. It is sectional drawing which shows the internal structure of the part AA line part of the wiring board shown in FIG. It is sectional drawing which shows the internal structure of the BB line portion of the wiring board shown in FIG. It is sectional drawing which shows the internal structure of the CC line part of the wiring board shown in FIG. It is a flowchart which shows the manufacturing process of the wiring board which concerns on one Embodiment of this invention. It is a schematic diagram which shows the state in which a conductive pattern forming process is performed in the order of process. It is a schematic diagram which shows the state which a transfer process is performed in the order of a process. It is a schematic diagram explaining the exposure process and the development process in the manufacturing process of a wiring board. It is sectional drawing which shows the shape of the conductive pattern formed by the conductive pattern forming process shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, the detailed description of them will not be repeated.

(Wiring board configuration)
In the present embodiment, the wiring board 1 will be described as an example of the wiring board according to the present invention. FIG. 1 is a schematic plan view showing the configuration of a part of the wiring board 1 on the surface side. 2 to 4 schematically show a cross-sectional configuration of the wiring board 1 shown in FIG.

In the present embodiment, for convenience, the surface of the substantially flat wiring board 1 on the side where the via is provided is the front surface 11a, and the surface on the opposite side is the back surface 11b. However, the definitions of the front surface and the back surface of the wiring board 1 are not limited to this, and can be arbitrarily determined. That is, both the front surface 11a and the back surface 11b of the wiring board 1 can correspond to the front surface of the ceramic substrate 11. Further, as shown in FIGS. 2 to 4, 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.

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 a base for the wiring board 1. The ceramic substrate 11 can be formed of, for example, a high-temperature fired ceramic containing alumina (Al ₂ O ₃ ) as a main component. In another embodiment, the ceramic sheet may be formed of a medium temperature fired ceramic (MTCC) such as alumina having improved sinterability, or a low temperature fired ceramic (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. 2 and 3 show a configuration example in which the ceramic substrate 11 is formed of one ceramic green sheet.

The conductive pattern is provided on the front surface 11a, the back surface 11b, the inside, and the like of the ceramic substrate 11. Each conductive pattern is formed in a predetermined shape, and functions as, for example, a wiring portion, a connection pad, a conductive via, an electrode, and the like.

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

For example, in the example shown in FIG. 1, a via 31 which is an example of a conductive pattern is provided on the surface 11a side of the ceramic substrate 11. The via 31 has a substantially circular shape when viewed from above. A part of the via 31 is exposed on the surface 11a of the ceramic substrate 11, and for example, a connection pad (not shown) is formed on the exposed surface. The connection pad is electrically connected to the via 31.

As shown in FIG. 2, the via 31 is embedded inside the ceramic substrate 11. The via 31 is joined to the wiring portion 21 which is an example of the conductive pattern inside the ceramic substrate 11. As a result, the via 31 and the wiring portion 21 are electrically connected. The wiring portion 21 can transmit an electric signal to and from a connection pad or the like formed on the surface 11a of the ceramic substrate 11 via the via 31.

The wiring portion 21 is stretched around the front surface 11a, the back surface 11b, the inside, and the like of the ceramic substrate 11. In FIG. 1, a plurality of wiring portions 21 extending inside the ceramic substrate 11 are shown by broken lines.

FIG. 2 shows a cross-sectional configuration of the AA line portion of the wiring board 1 shown in FIG. FIG. 3 shows the cross-sectional configuration of the BB line portion of the wiring board 1 shown in FIG. FIG. 4 shows a cross-sectional configuration of the CC line portion of the wiring board 1 shown in FIG.

The wiring portion 21 is provided on the back surface 11b side of the ceramic substrate 11. In the present embodiment, the front surface 21s of the wiring portion 21 is flush with the back surface 11b of the ceramic substrate 11. As shown in FIGS. 2 and 3, the wiring portion 21 is embedded inside the ceramic substrate 11.

As shown in FIG. 1, the joint portion 20 of the wiring portion 21 with the via 31 has a substantially circular shape when viewed from above. Further, the joint portion 20 is arranged so as to overlap the via 31 when viewed from above. The diameter D1 of the substantially circular joint portion 20 in the top view is larger than the diameter D2 of the substantially circular via 31 in the top view. Further, the diameter D1 of the joint portion 20 is larger than the width W of the portion (extended portion) other than the joint portion 20 in the wiring portion 21.

As shown in FIG. 2, the via 31 is mainly composed of a columnar portion 32 and a narrowed portion 33. The columnar portion 32 is located on the surface side (surface 11a in FIG. 2) of the ceramic substrate 11. The columnar portion 32 is a portion where the cross-sectional area in the X direction is substantially constant over the Y direction. The narrowed portion 33 is located on the inner side of the ceramic substrate 11. As shown in FIG. 2, the narrowed portion 33 is located at a connecting portion of the ceramic substrate 11 with the wiring portion 21 in the Y direction. The narrowed portion 33 becomes smaller as the cross-sectional area in the X direction toward the wiring portion 21.

As described above, the via 31 is buried in the ceramic substrate 11, and the narrowed portion 33 is provided at the connecting portion of the ceramic substrate 11 with the wiring portion 21 in the Y direction. As a result, the via 31 can be made difficult to come off from the ceramic substrate 11.

Further, in the wiring board 1 according to the present embodiment, it is preferable that the entire via 31 is buried in the ceramic substrate 11. As a result, the via 31 that is more difficult to come off from the ceramic substrate 11 can be obtained. Further, the surface 31s of the via 31 may be flush with the surface of the ceramic substrate 11 (the surface 11a in the example shown in FIG. 2 and the like).

As shown in FIG. 2, the wiring portion 21 is mainly composed of a main body portion 22 and a second constricted portion 23. The main body 22 is located on the front surface (back surface 11b in FIG. 2) of the ceramic substrate 11. The main body portion 22 is a portion in which the cross-sectional area in the X direction is substantially constant over the Y direction.

The second constricted portion 23 is provided on the upper layer of the main body portion 22. In other words, the second constricted portion 23 is located on the inner side of the ceramic substrate 11 with respect to the main body portion 22. As shown in FIG. 2, the second narrowed portion 23 has a shape at the connection portion of the ceramic substrate 11 with the via 31 in the Y direction so that the cross-sectional area in the X direction becomes smaller as it approaches the via 31. ing. Further, as shown in FIG. 4, the second constricted portion 23 is provided not only at a portion adjacent to the via 31 but also at both ends in a direction intersecting the extending direction of the wiring portion 21. As a result, it is possible to obtain the wiring portion 21 which is hard to be peeled off from the ceramic substrate 11.

In the wiring portion 21, it is preferable that the portion of the second narrowed portion 23 is at least buried in the ceramic substrate 11. As a result, the wiring portion 21 can be made more difficult to peel off from the ceramic substrate 11.

Further, in the wiring board 1 according to the present embodiment, it is preferable that the entire wiring portion 21 is buried in the ceramic substrate 11. That is, it is preferable that the surface 21s of the wiring portion 21 is flush with the surface of the ceramic substrate 11 (in the example shown in FIG. 2 and the like, the back surface 11b). As a result, it is possible to obtain the wiring portion 21 which is more difficult to peel off from the ceramic substrate 11.

When the wiring board 1 is formed by laminating a plurality of ceramic layers, it is preferable that the surface 21s of the wiring portion 21 is flush with the surface of the ceramic layers. As a result, the gap between the ceramic layers when the ceramic layers are laminated can be reduced.

(Manufacturing method of wiring board)
Subsequently, a method of manufacturing the wiring board 1 will be described. Here, the steps of forming a conductive pattern such as the via 31 and the wiring portion 21 will be mainly described. As a manufacturing method of the wiring board 1 other than this step, a conventionally known manufacturing method of the wiring board can be applied.

FIG. 5 shows a part of the manufacturing process of the wiring board 1 in the order of the processes. FIG. 5 mainly shows each step from the conductive pattern forming step (S10) to the firing step (S30). FIG. 6 schematically shows how the conductive pattern forming step (S10) is performed in the order of the steps. FIG. 7 schematically shows how the transfer step (S20) is performed in the order of the steps.

In performing each step shown in FIG. 5, first, the ceramic sheet 10 is prepared. The ceramic sheet 10 can be obtained, for example, by kneading a 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 ceramic sheet into a sheet shape.

After preparing the ceramic sheet, the conductive pattern forming step (S10) is performed. As shown in FIG. 5, the conductive pattern forming step (S10) includes a preparation step (S11), a film body forming step (S12), a first exposure step (S13), a second exposure step (S14), and The development step (S15) and the like are included.

In the preparation step (S11), the carrier film 61 and the 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. Both ends of the carrier film 61 are supported by the film support mechanism 50 and fixed in a horizontal state (see step A in FIG. 6).

The conductive paste 62 contains, for example, a metal powder containing copper (Cu), tungsten (W), silver (Ag), molybdenum (Mo), or the like, and a photosensitive resin. As the photosensitive resin, a negative photosensitive material that photocures when irradiated with ultraviolet light is used. In this embodiment, for example, a bisazido compound is used. Since the conductive paste contains a photosensitive resin, a conductive pattern having a predetermined shape can be formed by photolithography. Therefore, it is possible to form a conductive pattern having a finer pattern shape.

In the film body forming step (S12), the conductive paste 62 is applied onto the prepared carrier film 61. The conductive paste 62 can be applied using a conventionally known screen printing device 51. As a result, a conductive paste-attached film body (hereinafter referred to as a film body) can be obtained.

Subsequently, the first exposure step (S13) and the second exposure step (S14) are sequentially performed. Step B in FIG. 6 shows how the first exposure step (S13) is performed. In the first exposure step (S13), the film body is exposed from the carrier film 61 side.

After the first exposure step (S13), the second exposure step (S14) is performed. Step C in FIG. 6 shows how the second exposure step (S14) is performed. In the second exposure step (S14), the film body is exposed from the conductive paste 62 side.

In the first exposure step (S13) and the second exposure step (S14), the conductive paste 62 coated on the carrier film 61 is irradiated with light using the DI exposure apparatus 52. The DI exposure apparatus 52 includes a UV light source 52a.

In each exposure step, the conductive paste 62 on the carrier film 61 is irradiated with light using a glass mask 70 (not shown in FIG. 6) to match the shape of each conductive pattern formed on the wiring substrate 1. The photosensitive resin in the conductive paste 62 is photocured.

FIG. 8 schematically shows how the first exposure step (S13) is performed. In FIG. 8, the surface of the conductive paste 62 on the side far from the carrier film 61 is referred to as the first surface 62a, and the surface in contact with the carrier film 61 is referred to as the second surface 62b. Further, FIG. 9 schematically shows the cross-sectional shape of the conductive pattern 40 formed by the conductive pattern forming step (S10). In FIG. 9, the glass mask 70 used in the first exposure step (S13) is referred to as a glass mask 70a, and the glass mask 70 used in the second exposure step (S14) is referred to as a glass mask 70b.

In the first exposure step (S13), as shown in “1” of FIG. 8, the glass mask 70 (specifically, the glass mask 70a) is arranged above the conductive paste 62. In the glass mask 70, a light-shielding film 72 is provided on the flat glass 71 according to the shape of the conductive pattern 40 to be formed. In the exposure step, the conductive paste 62 on the carrier film 61 is irradiated with ultraviolet light L through which the photosensitive resin contained in the conductive paste 62 is photocured via the glass mask 70. As described above, in the first exposure step (S13), the film body is irradiated with ultraviolet light L from the carrier film 61 side (that is, the second surface 62b side).

As a result, the conductive paste 62 in the region where the light-shielding film 72 is not provided is irradiated with the ultraviolet light L, while the conductive paste 62 in the region where the light-shielding film 72 is provided is not irradiated with the ultraviolet light L. .. As a result, in the conductive paste 62 on the carrier film 61, only the photosensitive resin existing in the region irradiated with the ultraviolet light L is photocured, and the photosensitive resin existing in the region where the ultraviolet light is blocked by the light-shielding film 72. Remains on the carrier film 61 without photocuring.

When the ultraviolet light L is irradiated in this way, the ultraviolet light is scattered by the metal powder contained in the conductive paste 62, so that a part of the irradiated ultraviolet light L is on the side far from the carrier film 61 ( That is, it does not reach the conductive paste 62 on the first surface 62a side). Therefore, the photosensitive resin in the conductive paste 62 on the side farther from the carrier film 61 (that is, the first surface 62a side) tends to be hindered from photocuring.

That is, the photocurable region of the conductive paste 62 becomes narrower as the distance from the side where the ultraviolet light L is incident (that is, the side of the second surface 62b) is increased. In “2” of FIG. 8, the photocurable region of the conductive paste 62 is shown as 40A. As shown in FIG. 8, the photocurable region 40A has a shape in which the area in the plane direction decreases as the distance from the side where the ultraviolet light L is incident increases. A part of this portion becomes the second narrowed portion 23 of the wiring portion 21 in a later process.

In the second exposure step (S14) performed after the completion of the first exposure step (S13), the glass mask 70b is used with respect to the film body from the side opposite to the carrier film 61 (that is, the first surface 62a side). And irradiate ultraviolet light L.

When the ultraviolet light L is irradiated in this way, the region photocured in the conductive paste 62 is located on the side where the ultraviolet light L is incident (that is, the first one) for the same reason as in the first exposure step (S13). It becomes narrower as the distance from the surface 62a side) increases. As a result, the photocurable region 40A has a shape in which the area in the plane direction becomes smaller as the distance from the side where the ultraviolet light L is incident is increased. This portion becomes the narrowed portion 33 of the via 31 in a later step (see FIG. 9).

In the second exposure step (S14), it is preferable to increase the exposure amount as compared with the case of the first exposure step (S13). In the first exposure step (S13), the conductive paste 62 is irradiated with light through the carrier film 61. Therefore, when the exposure amount in each exposure step is the same, the conductive paste 62 is conductive in the first exposure step (S13). The light energy received by the sex paste 62 is smaller. Further, the region of the photosensitive conductive paste 62 photocured in the second exposure step (S14) is narrower than the region of the photosensitive conductive paste 62 photocured in the first exposure step (S13). ..

After that, the developing step (S15) is performed. In the developing step (S15), the conductive pattern 40 is formed on the carrier film 61. Specifically, the unphotosensitive portion (the portion other than the region 40A) of the conductive paste 62 is removed with a developing solution.

As a result, the portion of the region 40A of the conductive paste 62 containing the photocured photosensitive resin remains, and the conductive pattern 40 is formed on the carrier film 61 (see step D in FIG. 6). The conductive pattern 40 has a wiring portion 21 having a second narrowed portion 23 and the like, and a via 31 having a narrowed portion 33 and the like (see the inside of the broken line frame in FIG. 6).

As described above, in the developing step (S15), the film body that has undergone the first exposure step (S13) and the second exposure step (S14) is developed to develop the wiring portion from the conductive paste 62 on the side closer to the carrier film 61. A portion to be 21 is formed, and a portion where the conductive paste 62 on the side far from the carrier film 61 is to be a via 31 is formed.

As described above, the conductive pattern forming step (S10) is performed. As a result, the conductive pattern 40 having a predetermined shape is formed on the carrier film 61.

Subsequently, the transfer step (S20) is performed. In the transfer step, first, as shown in step E of FIG. 7, a hole processing device 54 provided with a lower mold 54a, a pin 54b, and the like is used to perform a predetermined portion of the ceramic sheet 10 (wiring portion 21 and via in the wiring board 1). A hole 10a is formed in the place where 31 is arranged).

Then, as shown in step F of FIG. 7, an adhesive solvent (for example, an alcohol solvent) is applied to the surface of the ceramic sheet 10 using an inkjet device 55 or the like, and a part of the ceramic sheet 10 is made into a paste. Specifically, the adhesive material is applied from the back surface of the ceramic sheet 10 (corresponding to the back surface 11b of the ceramic substrate 11), and the ceramics located on the back surface and the side surface of the hole 10a are made into a paste. In FIG. 7, in the ceramic sheet 10, the pasted ceramic portion is indicated by 10b.

Next, as shown in step G of FIG. 7, the surface on which the conductive pattern 40 of the film body is formed is on the ceramic sheet 10 side, and the carrier film 61 is placed on the back surface of the ceramic sheet 10 to be a heat pressing device. Pressurize and heat using 56.

Then, as shown in step H of FIG. 7, the conductive pattern 40 is transferred to the ceramic sheet 10 by peeling off the carrier film 61. Here, at least a part of the conductive pattern 40 is embedded in the hole 10a provided in the ceramic sheet 10.

As described above, in the transfer step (S20), the film body that has undergone the development step (S15) is pressed against the ceramic sheet 10 having the holes 10a at the predetermined positions, and the conductive pattern of the wiring portion 21 and the via 31 is pressed. 40 is transferred to the ceramic sheet 10. As a result, the conductive pattern 40 having a predetermined shape is formed on the ceramic sheet 10.

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

Then, the firing step (S30) is performed. In the firing step (S30), the ceramic sheet 10 to which the conductive pattern 40 is transferred or a laminate thereof is cofired (simultaneously fired). As a result, the ceramic sheet 10 becomes the ceramic substrate 11. By performing the firing step (S30), the photosensitive resin contained in the conductive pattern 40 is burnt down.

When the firing step (S30) is completed, a post-process such as a plating step is performed. The plating step is carried out by a conventionally known electrolytic plating method. By performing the electrolytic plating method, a plating film can be formed on the surface of the conductive pattern exposed from the ceramic substrate 11.

As described above, in the method for manufacturing the wiring substrate according to the present embodiment, the carrier film 61 coated with the conductive paste 62 is exposed to the first exposure step (S13) from the second surface 62b side of the conductive paste 62. ), And a second exposure step (S14) from the first surface 62a side, two exposure steps are performed. After that, a developing step (S15) is performed to form a conductive pattern 40 having a portion to be a via 31 on the first surface 62a side of the conductive paste 62 and a portion to be a wiring portion 21 on the second surface 62b side. obtain.

By forming the conductive pattern 40 using such an exposure step and a developing step, a finer conductive pattern can be formed. Therefore, according to the manufacturing method according to the present embodiment, for example, a wiring board 1 having a high-definition conductive pattern having a via diameter and a wiring portion width of 30 μm or less can be obtained.

Further, by forming the via 31 and the wiring portion 21 from the conductive paste 62 provided on one carrier film 61, the relative positional relationship between the via 31 and the wiring portion 21 can be easily defined. Can be done. Therefore, it is possible to suppress the misalignment of the wiring pattern with respect to the via, which may occur when the via and the wiring portion are formed by different development steps using different conductive pastes.

Further, in each exposure step in the above-mentioned conductive pattern forming step (S10), the photocurable region of the conductive paste 62 becomes narrower as the distance from the side where the ultraviolet light L is incident is utilized, and vias are utilized. A narrowed portion 33 and a second narrowed portion 23 can be formed at the connecting portion between the 31 and the wiring portion 21. By forming the narrowed portion 33, it is possible to prevent the via 31 from coming off from the ceramic substrate 11.

In the manufacturing method according to the present embodiment described above, the transfer step (S20) is performed to form the conductive pattern 40 on the ceramic sheet 10. However, the wiring board 1 according to the present embodiment can also be manufactured by using a method different from the transfer step. For example, the conductive pattern 40 can be formed on the ceramic sheet 10 by arranging the conductive pattern 40 in the box-shaped body, pouring a liquid ceramic material (slurry) into the box-shaped body, and hardening the liquid ceramic material (slurry). ..

(Summary of Embodiment)
As described above, the wiring board 1 according to the present embodiment includes a ceramic substrate 11, at least one conductive via 31, and a wiring portion 21 electrically connected to the via 31. The via 31 is embedded in the ceramic substrate 11. The wiring portion 21 is provided on at least one of the inside and the front surface (specifically, the front surface 11a or the back surface 11b of the ceramic substrate 11) of the ceramic substrate 11. The via 31 has a narrowed portion 33 at the connection portion of the ceramic substrate 11 with the wiring portion 21 in the thickness direction Y, in which the area of the plane direction X orthogonal to the thickness direction Y becomes smaller toward the wiring portion 21. ing.

According to the above configuration, since the via 31 has the narrowed portion 33 in the connection portion with the wiring portion 21, the adhesion of the via 31 to the ceramic substrate 11 is improved, and the via 31 is the ceramic substrate 11. It can be configured so that it does not easily come off.

The method for manufacturing the wiring substrate 1 according to the present embodiment includes a film body forming step (S12), a first exposure step (S13), a second exposure step (S14), a development step (S15), and transfer. A step (S20) and a firing step (S30) are included.

In the film body forming step (S12), the photosensitive conductive paste 62 is applied onto the carrier film 61 to form a conductive paste-attached film body. In the first exposure step (S13), the film body is exposed from the carrier film 61 side. In the second exposure step (S14), after the first exposure step (S13), the film body is exposed from the conductive paste 62 side.

In the developing step (S15), the film body that has undergone the first exposure step (S13) and the second exposure step (S14) is developed. As a result, a part of the conductive paste 62 located on the side close to the carrier film 61 becomes the conductive pattern 40 of the wiring portion 21, and a part of the conductive paste 62 located on the side far from the carrier film 61 becomes the via 31. The conductive pattern 40 is obtained.

In the transfer step (S20), the film body that has undergone the developing step (S15) is pressed against the ceramic sheet 10 having at least holes 10a at the location where the via 31 is arranged, and the wiring portion 21 and the via 31 are conductive. The pattern 40 is transferred to the ceramic sheet 10. In the firing step (S30), the ceramic sheet 10 to which the conductive pattern 40 is transferred is fired.

According to this manufacturing method, the via 31 and the wiring portion 21 are simultaneously developed from the conductive paste 62 provided on the carrier film 61, so that the relative positional relationship between the via 31 and the wiring portion 21 can be easily established. Can be specified. Therefore, it is possible to suppress the misalignment of the wiring pattern with respect to the via, which may occur when the via and the wiring portion are formed by different development steps using different conductive pastes.

Further, in the first exposure step (S13) and the second exposure step (S14), the photocurable region of the conductive paste 62 is narrowed as the distance from the side where the ultraviolet light L is incident is utilized. The narrowed portion 33 and the second narrowed portion 23 can be formed at least at the connecting portion between the via 31 and the wiring portion 21. Since the narrowed portion 33 and the second narrowed portion 23 are formed, the via 31 and the wiring portion 21 can be configured to be hard to be peeled off from the ceramic substrate 11.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims. Further, a configuration obtained by combining the configurations of the respective embodiments described in the present specification with each other is also included in the scope of the present invention.

1: Wiring board 10: Ceramic sheet 11: Ceramic board 11a: Surface (of ceramic board) (surface of ceramic board)
11b: Back surface (of ceramic substrate) (front surface of ceramic substrate)
20: Joint (connection between via and wiring)
21: Wiring part 22: Main body part 23: Second narrowed part 31: Via 32: Columnar part 33: Constricted part 40: Conductive pattern 61: Carrier film (film)
62: Conductive paste

Claims (5)

With a ceramic substrate
At least one conductive via, which is embedded in the ceramic substrate, and
A wiring board provided on at least one of the inside and the surface of the ceramic substrate and including a wiring portion electrically connected to the via.
The via has a constricted portion at a connection portion with the wiring portion in the thickness direction of the ceramic substrate, in which the area in the plane direction orthogonal to the thickness direction becomes smaller toward the wiring portion. Wiring board. The wiring portion is formed on the surface of the ceramic substrate, and at least a part thereof is embedded in the ceramic substrate.
A second constricted portion in the wiring portion, which is embedded in the ceramic substrate, is provided so that the area in the plane direction becomes smaller as the via approaches.
The wiring board according to claim 1. The wiring board according to claim 2, wherein the second narrowed portion is provided at a portion adjacent to the via in the thickness direction of the ceramic substrate. The surface of the wiring portion is flush with the surface of the ceramic substrate.
The wiring board according to claim 2 or 3. A film body forming step of applying a photosensitive conductive paste on a film to form a film body adhering to the conductive paste.
The first exposure step in which the film body is exposed from the film side,
After the first exposure step, the film body is exposed from the conductive paste side, and the second exposure step
By developing the film body that has undergone the first exposure step and the second exposure step, the conductive paste on the side close to the film becomes a conductive pattern of the wiring portion, and the conductivity on the side far from the film. The development process, where the paste becomes the conductive pattern of the vias,
The film body that has undergone the developing step is pressed against a ceramic sheet having at least a hole at a position where the via is arranged, and the wiring portion and the conductive pattern of the via are transferred to the ceramic sheet. Transfer process and
A method for manufacturing a wiring board, which comprises a firing step of firing the ceramic sheet after the transfer step.

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