JP2022122386A - wiring board - Google Patents

Abstract

To reduce the diameter of a connection terminal portion and suppress the peeling of the connection terminal portion in a wiring board in which at least a part of the connection terminal portion is exposed on the surface of an insulating board.SOLUTION: A wiring board 1 includes a ceramic board 11, via 31, and a connection pad 21. The ceramic board 11 has a front surface 11a (first surface) and a back surface 11b (second surface). The vias 31 are arranged in the ceramic board 11. The connection pads 21 are arranged in the ceramic board 11 and connected to the vias 31. At least a part of the connection pad 21 is exposed from the front surface 11a. Moreover, the connection pad 21 has a maximum width portion at a portion that enters inside the ceramic board 11. An equivalent circle diameter D1 of the end surface of the connection pad 21 exposed from the surface 11a is within the range of 30 μm or more and 100 μm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wiring board provided with connection terminal portions for external connection.

As a wiring board on which electronic parts such as semiconductor elements are mounted, a ceramic substrate formed 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 conductive patterns. The conductive pattern formed on the wiring board functions, for example, as wiring, vias, connection terminals, and the like. The connection terminals are also called connection pads, and are electrically connected to external electronic components.

Patent Document 1 discloses a ceramic wiring board on which electronic components such as semiconductor elements and crystal oscillators are mounted. This ceramic wiring board has a ceramic insulating layer, a through conductor provided to penetrate the ceramic insulating layer in the thickness direction, and a conductor layer joined to the end surface of the through conductor in the thickness direction. is doing. The conductor layer serves as a terminal for connection with an electronic component when the electronic component is mounted on the ceramic substrate.

JP 2016-115795 A

In the ceramic wiring board disclosed in Patent Document 1, the conductor layer 3 is embedded in the ceramic insulating layer 1 in a partially exposed state when viewed in cross section in the thickness direction, and the exposed surface of the conductor layer 3 is When the surface on the side of the first surface 3a and the penetrating conductor 5 is defined as the second surface 3b, the width w1 of the first surface 3a is larger than the width w2 of the second surface 3b. is an inclined surface 7 from the first surface 3a side to the second surface 3b side, and the angle between the inclined surface 7 and the side surface 5s of the penetrating conductor 5 is larger than 90°.

However, if the shape of the conductor layer exposed on the surface of the ceramic wiring board is made to have a shape that decreases in diameter from the surface toward the inner layer side, the conductor layer tends to come off from the ceramic insulating layer. In recent years, there has been an increasing demand for miniaturization of wiring substrates, and the conductor layers are also required to have a small diameter as well. However, the smaller the diameter, the smaller the contact area with the ceramic substrate. Therefore, there is a problem that the conductor layer tends to come off from the ceramic insulating layer even when the diameter is reduced (miniaturized).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the diameter of a connection terminal portion and to suppress peeling of the connection terminal portion in a wiring substrate in which at least a portion of the connection terminal portion is exposed on the surface of an insulating substrate. do.

A wiring board according to one aspect of the present invention includes an insulating substrate having a first surface and a second surface opposite to the first surface in the thickness direction of the wiring substrate; and a connection terminal portion disposed in the insulating substrate and connected to the via. In this wiring board, at least a portion of the connection terminal portion is exposed from the first surface, and a portion of the connection terminal portion that enters into the insulating substrate extends from the thickness of the connection terminal portion. A maximum width portion of the connection terminal portion having a maximum width in a plane direction perpendicular to the thickness direction when viewed in a cross-sectional view in the direction is located inside the insulating substrate. The width in the plane direction is larger than the width in the plane direction of the connection terminal portion at the position of the first plane. Further, the equivalent circle diameter of the end surface of the connection terminal portion exposed from the first surface is in the range of 30 μm or more and 100 μm or less.

According to the above configuration, it is possible to reduce the diameter of the connection terminal portion and obtain a wiring board with high definition. In addition, even when the diameter of the connection terminal portion is reduced, by configuring the connection terminal portion as described above, it is possible to obtain the connection terminal portion that is difficult to peel off from the insulating substrate.

In the above-described wiring board according to one aspect of the present invention, the via may have a shape that tapers toward the connection terminal portion.

According to the above configuration, the entire end surface of the via can be easily brought into contact with the end surface of the connection terminal portion. As a result, it is possible to suppress an increase in the resistance value that can occur when the via and the connection terminal are electrically connected in a positionally displaced state.

In the above wiring board according to one aspect of the present invention, the end surface of the connection terminal portion exposed from the first surface of the insulating substrate is flush with the first surface of the insulating substrate. may be

According to the above configuration, an electronic component such as a semiconductor chip can be stably placed on the connection terminal portion.

In the above-described wiring board according to one aspect of the present invention, the connection terminal portion includes a tapered portion that tapers toward the first surface of the insulating substrate and a tapered portion along the surface direction of the insulating substrate. and a columnar portion having a substantially constant shape in the thickness direction of the insulating substrate.

According to the above configuration, it is possible to obtain the connection terminal portion that is more difficult to peel off from the insulating substrate.

Another aspect of the present invention relates to a wiring board manufacturing method. The wiring board includes a ceramic substrate, conductive vias arranged in the ceramic substrate, and connection terminal portions arranged in the ceramic substrate and electrically connected to the vias. . This wiring board manufacturing method includes a hole forming step of irradiating a ceramic sheet before firing with a laser to form a hole where the via is to be arranged; Conductivity for the connection terminal portion having a shape tapering toward the contact surface with the film by a filling step, and exposing and developing a film coated with a photosensitive conductive paste The conductive pattern formed in the pattern forming step is transferred to the ceramic sheet that has undergone the pattern forming step and the filling step to form a pattern, and the conductive ink and the conductive pattern are transferred. It includes a transfer step of electrically connecting, and a firing step of firing the ceramic sheet after the transfer step.

According to the above-described method, it is possible to manufacture a wiring board capable of suppressing peeling of the connection terminal portion while reducing the diameter of the connection terminal portion.

In the method for manufacturing a wiring board according to one aspect of the present invention, in the hole forming step, the laser is irradiated from the opposite side of the ceramic sheet to the side to which the conductive pattern is transferred to form the holes. may

According to the above method, it is possible to form a via having a shape that tapers toward the connection terminal portion. As a result, the entire end surface of the via can be easily brought into contact with the end surface of the connection terminal portion, so the possibility of electrical connection between the via and the connection terminal portion being misaligned can be reduced.

According to the wiring board according to one aspect of the present invention, it is possible to reduce the diameter of the connection terminal portion while suppressing peeling of the connection terminal portion. In addition, according to the method of manufacturing a wiring board according to another aspect of the present invention, it is possible to manufacture a wiring board capable of suppressing peeling of the connection terminal portion while reducing the diameter of the connection terminal portion. .

1 is a schematic plan view showing the configuration of a wiring board according to one embodiment; FIG. 2 is a schematic cross-sectional view showing the configuration of the AA line portion of the wiring substrate shown in FIG. 1; FIG. 3 is an enlarged cross-sectional view showing vias and connection pads shown in FIG. 2; FIG. 4 is a flow chart showing each step of a wiring board manufacturing method according to one embodiment. 5 is a schematic diagram for explaining a hole forming step and a filling step in the method of manufacturing the wiring board shown in FIG. 4; FIG. 5 is a schematic diagram for explaining a pattern forming step in the method of manufacturing the wiring board shown in FIG. 4; FIG. 5 is a schematic diagram for explaining a transfer step in the method of manufacturing the wiring board 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.

(Structure of wiring board)
In this embodiment, a 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 front side. FIG. 2 schematically shows a cross-sectional configuration of the wiring board 1. As shown in FIG. FIG. 2 is a cross-sectional view of the wiring substrate 1 shown in FIG. 1 cut along line AA.

The wiring board 1 is mainly composed of a ceramic substrate (insulating substrate) 11 and a conductive pattern. The conductive pattern includes, for example, connection pads (connection terminal portions) 21, vias 31, wiring portions 41, and the like.

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. 2 shows a structural example in which the ceramic substrate 11 is formed of one ceramic green sheet.

In this embodiment, for convenience, the surface of the substantially flat ceramic substrate 11 on which the connection pads 21 are provided is referred to as the front surface (first surface) 11a, and the opposite surface is referred to as the rear surface (second 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. The surface direction of the ceramic substrate 11 is defined as the X direction, and the thickness direction of the ceramic substrate 11 is defined as the Y direction (see FIG. 2).

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 as, for example, a wiring portion, a connection pad, a via, an electrode, and the like.

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.

A connection pad 21, which is an example of a conductive pattern, is used as a connection terminal with another electronic component (for example, a semiconductor chip, etc.). The connection pads 21 are preferably used as connection terminals, for example, when another electronic component is mounted on the wiring board 1 by a flip-chip method. When a semiconductor chip is connected to the wiring board 1 by the lip chip method, bumps are formed on the connection pads 21 with solder or the like, and the connection pads 21 are electrically connected to the connection terminals of the semiconductor chip through the bumps. be done.

In this embodiment, as shown in FIG. 2, a plurality of connection pads 21 are provided on the surface 11a side of the ceramic substrate 11 . Moreover, in this embodiment, most of the connection pads 21 are embedded inside the ceramic substrate 11 , and some of them are exposed from the surface 11 a of the ceramic substrate 11 . That is, the surfaces 21 s of the connection pads 21 are exposed from the surface 11 a of the ceramic substrate 11 .

A via 31 , which is an example of a conductive pattern, is embedded inside the ceramic substrate 11 . In this embodiment, a plurality of vias 31 are provided on the back surface 11b side of the ceramic substrate 11 . Each connection pad 21 is arranged on each via 31 , and the via 31 and the connection pad 21 are electrically connected. As shown in FIG. 2, one connection pad 21 and one via 31 connected thereto are provided so as to penetrate the inside of the ceramic substrate 11 (that is, from the front surface 11a to the rear surface 11b).

A wiring portion 41, which is an example of a conductive pattern, is stretched over the surface 11a, the back surface 11b, the inside, and the like of the ceramic substrate 11. As shown in FIG. Some of these wiring portions 41 are connected to vias 31 inside the ceramic substrate 11 . Thereby, the via 31 and the wiring portion 41 are electrically connected. The wiring portion 41 can transmit and receive electrical signals to and from connection pads 21 formed on the surface 11 a side of the ceramic substrate 11 through the vias 31 .

Next, more detailed configurations of the connection pads 21 and the vias 31 will be described. FIG. 3 shows the cross-sectional shape of one of the connection pads 21 shown in FIG. 2 and one via 31 connected to this connection pad 21 .

As shown in FIG. 1, the connection pad 21 has a substantially circular shape when viewed from above. The connection pads 21 are arranged so as to overlap the vias 31 when viewed from above. As shown in FIG. 3 , the connection pad 21 has a tapered portion 22 and a columnar portion 23 . The tapered portion 22 is located on the surface side of the ceramic substrate 11 (the surface 11a in FIG. 3 and the like).

The tapered portion 22 tapers toward the surface 11 a of the ceramic substrate 11 . That is, the tapered portion 22 has a shape in which the cross-sectional area in the plane direction (X direction) of the ceramic substrate 11 increases with increasing distance from the surface 11 a of the ceramic substrate 11 . In this embodiment, the cross-sectional shape of the tapered portion 22 in the planar direction (X direction) is substantially circular.

The columnar portion 23 is positioned inside the ceramic substrate 11 . The columnar portion 23 is in contact with the via 31 . The columnar portion 23 has a substantially constant cross-sectional shape along the surface direction (X direction) of the ceramic substrate 11 in the thickness direction (Y direction) of the ceramic substrate 11 . In this embodiment, the cross-sectional shape of the columnar portion 23 in the planar direction (X direction) is substantially circular.

In the present embodiment, the diameter D1 of the surface 21s of the connection pad 21, which is substantially circular in top view, is smaller than the diameter D2 of the columnar portion 23 of the connection pad 21, which is substantially circular in top view (see FIG. 1). ).

That is, the shape of the connection pad 21 is such that when the connection pad 21 is viewed in cross section in the Y direction (thickness direction), the width of the connection pad 21 in the X direction (surface direction) is the maximum width portion (this embodiment In terms of form, it corresponds to the columnar portion 23 ) is located inside the ceramic substrate 11 . The width of the maximum width portion in the X direction (plane direction) (corresponding to the diameter D2 of the columnar portion 23 in this embodiment) is the X direction (plane direction) of the connection pad 21 at the position of the surface 11a of the ceramic substrate 11. ) (corresponding to the diameter D1 of the surface 21s of the tapered portion 22 in this embodiment).

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

In addition, in this embodiment, the side surface of the tapered portion 22 located in the surface layer portion of the ceramic substrate 11 has a curved shape (R shape) in a cross-sectional view (see FIG. 3, etc.). Thereby, the contact area between the tapered portion 22 and the ceramic layer can be increased in the portion where the connection pad 21 is embedded in the ceramic substrate 11 . Therefore, the bonding strength of the connection pads 21 to the ceramic substrate 11 is increased, and the connection pads 21 are more difficult to come off from the ceramic substrate 11 .

The via 31 has a shape that tapers toward the connection pad 21 . That is, the cross-sectional area of the via 31 in the planar direction (X direction) of the portion located on the back surface 11 b side of the ceramic substrate 11 is equal to the cross-sectional area of the portion in the planar direction (X direction) in contact with the connection pad 21 . is larger than In this embodiment, the cross-sectional shape of the via 31 in the planar direction (X direction) is substantially circular.

As will be described later, the vias 31 can be formed by filling holes 10a formed in the ceramic sheet 10 with a conductive material using a laser or the like. As a result, the cross-sectional diameter of the via 31 in the plane direction (X direction) can be reduced to about 30 μm or less, for example. Moreover, it is possible to obtain the wiring substrate 1 in which the plurality of vias 31 are arranged at narrow intervals (for example, about 50 μm).

Further, by forming the hole 10a for forming the via in the ceramic substrate 11 using a laser, the via 31 can be formed in a shape tapered toward the connection pad 21. FIG. By making the via 31 tapered toward the connection pad 21 , the entire end surface of the via 31 can be easily brought into contact with the end surface of the connection pad 21 . As a result, it is possible to suppress an increase in the resistance value that may occur when the via 31 and the connection pad 21 are electrically connected in a positionally displaced state.

Moreover, most of the connection pads 21 are buried in the ceramic substrate 11 , and at least a portion of the connection pads 21 are exposed from the surface 11 a of the ceramic substrate 11 .

The equivalent circle diameter D1 of the top surface (end surface) of the connection pad 21 exposed from the surface 11a of the ceramic substrate 11 is in the range of 30 μm to 100 μm. When the diameter D1 is 30 μm or more, the holes 10a having a uniform diameter can be stably formed in the hole forming step (S10) of the manufacturing method of the wiring board 1 to be described later. Further, since the diameter D1 is 100 μm or less, it is possible to achieve high definition of the connection pad 21 .

Furthermore, in the wiring board 1 according to this embodiment, it is preferable that the connection pads 21 are entirely buried in the ceramic substrate 11 . As a result, connection pads 21 that are more difficult to come off from ceramic substrate 11 can be obtained. Also, the surface 21s of the connection pad 21 may be flush with the surface of the ceramic substrate 11 (the surface 11a in the example shown in FIG. 3, etc.). Thereby, an electronic component such as a semiconductor chip can be placed on the connection pads 21 in a stable state.

(Method for manufacturing wiring board)
Next, a method for manufacturing the wiring board 1 will be described. Here, the process of forming conductive patterns such as connection pads 21 and vias 31 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 step from the hole forming step (S10) to the firing step (S50). FIG. 5 schematically shows, in order of steps, a hole forming step (S10) and a filling step (S20) mainly for forming vias 31 and the like. FIG. 6 schematically shows the pattern formation step (S30) for forming the connection pads 21 in order of steps. FIG. 7 schematically shows the transfer step (S40) of transferring the conductive pattern for the connection pad 21 to the ceramic sheet 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 , first, conductive patterns for vias 31 are formed at predetermined locations in the ceramic sheet 10 . Specifically, a hole forming step (S10) and a filling step (S20) are performed. FIG. 5 schematically shows how the hole forming step (S10) and the filling step (S20) are performed.

In the hole forming step (S10), as in step A shown in FIG. A hole 10a is formed. As shown in FIG. 5, a masking film 52 is arranged on the back surface 10d of the ceramic sheet 10 (the surface opposite to the laser irradiation surface 10c). In the subsequent filling step (S20), the conductive ink is filled from the surface side where the masking film 52 is arranged.

Further, in the hole forming step (S10), the hole 10a is formed by irradiating the laser 51 from the opposite side of the ceramic sheet 10 to the side to which the conductive pattern is transferred in the subsequent transfer step (S40). As a result, as shown in FIG. 5, the hole 10a is formed such that the diameter of the hole 10a in the surface direction of the ceramic sheet 10 gradually decreases from the laser irradiation surface 10c toward the back surface 10d.

As the laser 51, for example, a _CO2 laser, a UV laser, or the like can be used. By forming holes in the ceramic sheet 10 using the laser 51, the diameter of the holes 10a can be reduced and the distance between adjacent holes can be reduced.

After the hole forming step (S10), the filling step (S20) is performed. In the filling step (S20), like step B shown in FIG. Fill the hole 10a. As a result, the conductive pattern 30 for the via 31 can be formed in a shape that tapers from the laser irradiation surface 10c of the ceramic sheet 10 toward the back surface 10d (laser emission surface).

Subsequently, a pattern forming step (S30) is performed. FIG. 6 schematically shows how the pattern forming step (S30) is performed. The pattern formation step (S30) includes an exposure step (S31) and a development step (S31). Process A in FIG. 6 shows the exposure process (S31). Process B in FIG. 6 shows the development process (S31).

Before performing the exposure step (S31), 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. In this embodiment, for example, a bisazide compound 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 (S31), for example, the conductive paste 62 applied on the carrier film 61 is irradiated with light L using an exposure device equipped with a UV light source.

In the exposure step (S31), 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 connection pads 21 formed on the wiring substrate 1. The photosensitive resin inside is photo-cured. In FIG. 6, 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>31 ), 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 plate of glass in conformity with the shape of the conductive pattern 20 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 on the side closer to the carrier film 61 (that is, on the side closer to the carrier film 61). 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 tapered toward the contact surface with the carrier film 61 .

After that, the development step (S32) is performed. In the developing step ( S<b>32 ), the conductive pattern 20 is formed on the carrier film 61 . Specifically, the conductive paste 62 is treated with a developer 75 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 20 is formed on the carrier film 61 (see step B in FIG. 6). The conductive pattern 20 has a tapered portion 22 located on the carrier film 61 side and a columnar portion 23 located on the far side from the carrier film 61 .

The pattern forming step (S30) is performed as described above. Thereby, the conductive pattern 20 having a predetermined shape is formed on the carrier film 61 .

Subsequently, a transfer step (S40) is performed. FIG. 7 schematically shows how the transfer step (S40) is performed. In the transfer step (S40), the conductive pattern 20 formed in the pattern forming step (S30) is transferred to the ceramic sheet 10 that has undergone the filling step (S20), thereby forming the conductive pattern 30 for the via 31 and the connection pad. The conductive pattern 20 for 21 is electrically connected.

Specifically, as shown in step A of FIG. 7, an inkjet device 55 or the like is used to apply an adhesive solvent (for example, an alcohol-based solvent) to the surface of the ceramic sheet 10, and part of the ceramic sheet 10 is paste. become Here, the bonding material is applied from the rear surface 10d (corresponding to the front surface 11a of the ceramic substrate 11) side of the ceramic sheet 10, and a portion of the ceramic sheet is made into a paste. In FIG. 7, the pasted ceramic portion of the ceramic sheet 10 is indicated by 10b.

Next, as shown in step B of FIG. 7, the surface of the carrier film 61 on which the conductive pattern 20 is formed faces the ceramic sheet 10, and the carrier film 61 is placed on the back surface 10d of the ceramic sheet 10 and heated. A pressing device 56 is used to apply pressure and heat. At this time, the position of each conductive pattern 30 formed on the ceramic sheet 10 side and the position of each conductive pattern 20 formed on the carrier film 61 side are aligned with each other with respect to the ceramic sheet 10 . A carrier film 61 is aligned. This enables electrical connection between the conductive pattern 30 and the conductive pattern 20 .

Thereafter, as shown in step C of FIG. 7, the conductive pattern 20 is transferred to the ceramic sheet 10 by peeling off the carrier film 61 . Here, at least part of the conductive pattern 20 is embedded in the ceramic sheet 10 .

Thus, in the transfer step (S40), the film body that has undergone the developing step (S32) is pressed against the ceramic sheet 10 having the conductive pattern 30 formed at a predetermined location, thereby transferring the conductive pattern 20. Transfer to the ceramic sheet 10 . Thereby, the conductive pattern 20 connected to the conductive pattern 30 is formed on the ceramic sheet 10 .

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 (S50) is performed. In the firing step (S50), the ceramic sheet 10 on which the conductive patterns 20 and 30 are 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 20 is burned out by performing the baking step (S50).

After the firing process (S50) is completed, post-processes such as a plating process are performed. The plating process is performed by a conventionally known electroplating method. By performing the electroplating method, a plating film can be formed on the surface of the conductive pattern (for example, the connection pad 21) exposed from the ceramic substrate 11. FIG.

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 20 having a tapered shape is formed. This conductive pattern 20 is transferred to the ceramic sheet 10 on which the conductive pattern 30 for vias 31 is formed, and the conductive pattern 30 and the conductive pattern 20 are electrically connected.

By forming the conductive pattern 20 using such a manufacturing method, a finer conductive pattern can be formed. Therefore, according to the manufacturing method according to the present embodiment, for example, the diameter of the connection pad 21 is approximately 30 μm, and the interval between the adjacent connection pads 21 is approximately 60 μm. A substrate 1 can be obtained.

Further, in the exposure step (S31) of the pattern formation step (S30) 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 22 may be formed in the sexual pattern 20 . This tapered portion 22 becomes the tapered portion 22 of the connection pad 21 . Since the connection pad 21 has the tapered portion 22 on the side of the surface 11 a of the ceramic substrate 11 , the connection pad 21 can be made difficult to come off from the ceramic substrate 11 .

Further, in the hole forming step (S10), by forming the holes 10a in the ceramic sheet 10 using the laser 51, the diameter of the holes 10a can be reduced and the distance between adjacent holes can be reduced. can. For example, by forming the hole 10a using a CO ₂ laser, the diameter of the hole 10a can be reduced to about 30 μm. Further, by forming the hole 10a using a UV laser, the diameter of the hole 10a can be reduced to about 20 μm. Also, by using a CO ₂ laser or a UV laser, the interval between adjacent holes 10a can be narrowed to about 50 μm.

As described above, in the hole forming step (S10), the laser 51 is emitted from the side opposite to the side of the ceramic sheet 10 to which the conductive pattern 30 is transferred (that is, the back surface 10d side) (that is, the laser irradiation surface 10c side). Preferably, the holes 10a are formed by irradiation.

Thereby, the hole 10a can be formed so that the diameter of the hole 10a in the surface direction of the ceramic sheet 10 gradually decreases from the laser irradiation surface 10c toward the back surface 10d (see FIG. 5). By filling the hole 10 a having such a shape with the conductive ink 54 , the via 31 having a shape that tapers toward the connection pad 21 can be formed. As a result, the area of the via 31 at the contact portion with the connection pad 21 is reduced, and the entire end surface of the via 31 can be easily brought into contact with the connection pad 21 . Therefore, it is possible to suppress an increase in the resistance value that may occur due to mutual positional displacement at the contact portion between the via 31 and the connection pad 21 .

Further, in the hole forming step (S10), there is a possibility that the diameter of the hole 10a may vary on the back surface 10d side of the ceramic sheet 10, which is the emission surface of the laser 51, compared to the laser irradiation surface 10c side. As a result, the diameter of the via 31 may also become unstable on the back surface 10d side. In this embodiment, the conductive pattern 20 of the connection pad 21 is transferred to the side of the via 31 where the diameter may be unstable, and is embedded in the ceramic substrate 11 . On the other hand, variations in the diameter of the vias 31 exposed on the back surface 11b of the ceramic substrate 11, which is on the side of the laser irradiation surface 10c, can be reduced.

(Summary of embodiment)
As described above, the wiring board 1 according to this embodiment includes the ceramic substrate 11, the vias 31, and the connection pads 21. As shown in FIG. The ceramic substrate 11 has a front surface 11a (first surface) and a back surface 11b (second surface). Vias 31 are arranged in the ceramic substrate 11 . The connection pads 21 are arranged inside the ceramic substrate 11 and connected to the vias 31 . At least part of the connection pad 21 is exposed from the surface 11a. Moreover, the connection pad 21 has a maximum width portion (specifically, a columnar portion 23 ) at a portion that enters inside the ceramic substrate 11 . The width of the maximum width portion in the X direction (surface direction) (specifically, the diameter D2 of the columnar portion 23) is the width of the connection pad 21 in the X direction (surface direction) at the position of the surface 11a of the ceramic substrate 11 ( Specifically, it is larger than the diameter D1) of the surface 21s of the tapered portion 22 .

According to the above configuration, since the maximum width portion of the connection pad 21 is embedded in the ceramic substrate 11, peeling of the connection pad 21 can be suppressed.

Further, in the method for manufacturing the wiring board 1 according to the present embodiment, the conductive pattern 20 for the connection pad 21 is formed by photolithography including the above-described exposure step (S31) and development step (S32). As a result, the equivalent circle diameter D1 of the end face of the connection pad 21 exposed from the surface 11a can be, for example, within the range of 30 μm or more and 100 μm or less.

As described above, according to the present embodiment, it is possible to obtain the wiring substrate 1 with the diameter of the connection pads 21 reduced and the definition increased. Further, according to the present embodiment, even if the diameter of the connection pad 21 is reduced, by forming the connection pad 21 into the shape described above, it is possible to form the connection pad 21 that is difficult to peel off from the ceramic substrate 11. can.

Note that when the connection pads 21 are formed using the transfer step (S40) as in the manufacturing method of the present embodiment, the flatness of the surface of the connection pads is higher than when the connection pads are formed using the screen printing method. can be improved. Therefore, by using the conductive pattern formed by the manufacturing method of the present embodiment as the connection pad 21, the reliability of connection with the connection terminal of the semiconductor chip can be improved. Therefore, the wiring board 1 according to the present embodiment is preferably used as a wiring board to which a semiconductor chip or the like is connected by a flip-chip method.

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. In addition, configurations obtained by combining the configurations of the embodiments described in this specification are also included in the scope of the present invention.

Reference Signs List 1: wiring board 10: ceramic sheet 10a: hole formed in ceramic sheet 11: ceramic substrate (insulating substrate)
11a: Surface of ceramic substrate (first surface)
11b: back surface of ceramic substrate (second surface)
20: Conductive pattern for connection pad 21: Connection pad (connection terminal portion)
21s: surface of connection pad 22: tapered portion 23: columnar portion (maximum width portion)
30: Conductive pattern for vias 31: Vias 51: Laser 54: Conductive ink 61: Carrier film (film)
62: conductive paste

Claims (6)

an insulating substrate having a first surface and a second surface opposite to the first surface in its thickness direction;
a conductive via disposed within the insulating substrate;
A connection terminal portion disposed in the insulating substrate and connected to the via,
At least part of the connection terminal portion is exposed from the first surface,
Width of the connection terminal portion in a plane direction orthogonal to the thickness direction when the connection terminal portion is viewed in a cross section in the thickness direction in a portion of the connection terminal portion that is inserted into the insulating substrate is located inside the insulating substrate, and the width of the maximum width portion in the surface direction is greater than the width of the connection terminal portion in the surface direction at the position of the first surface. is also increasing,
The equivalent circle diameter of the end surface of the connection terminal portion exposed from the first surface is in the range of 30 μm or more and 100 μm or less.
wiring board. The via has a shape that tapers toward the connection terminal,
The wiring board according to claim 1. 3. The wiring board according to claim 1, wherein said end surface of said connection terminal portion exposed from said first surface of said insulating substrate is flush with said first surface of said insulating substrate. . The connection terminal portion is
a taper that tapers toward the first surface of the insulating substrate;
The wiring board according to any one of claims 1 to 3, further comprising a columnar portion whose shape along the plane direction of the insulating substrate is substantially constant in the thickness direction of the insulating substrate. . a ceramic substrate;
a conductive via disposed within the ceramic substrate;
A method for manufacturing a wiring board including a connection terminal section disposed in the ceramic substrate and electrically connected to the via,
a hole forming step of irradiating a ceramic sheet before firing with a laser to form a hole where the via is to be arranged;
a filling step of filling the holes of the ceramic sheet with a conductive ink;
A pattern forming step of forming a conductive pattern for the connection terminal portion having a shape tapered toward a contact surface with the film by exposing and developing the film coated with the photosensitive conductive paste. When,
a transfer step of transferring the conductive pattern formed in the pattern forming step to the ceramic sheet that has undergone the filling step, and electrically connecting the conductive ink and the conductive pattern;
and a firing step of firing the ceramic sheet after the transferring step. In the hole forming step, the hole is formed by irradiating the laser from the side of the ceramic sheet opposite to the side on which the conductive pattern is transferred.
A method for manufacturing a wiring board according to claim 5 .

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