JP2009176907A - Wiring substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate that allows planarization of the surface/rear-face of a ceramic layer of the outermost layer, where the end face of a via conductor is exposed, even if the via conductor continuously penetrates through a plurality of ceramic layers while allowing highly-accurate mounting or the like of each electronic component on the surface/rear-face, and its manufacturing method. <P>SOLUTION: The wiring substrate 1a includes a substrate body 2, which includes the surface 3 and the rear face 4 and is formed by laminating a plurality of ceramic layers S1-S4 including ceramic layers respectively formed with a through-hole h, a via hole 10, which is opened in the surface 3 of the substrate body 2 and in which a plurality of the through-holes h are continuous along in the thickness direction of the substrate body 2, a via conductor V, which is filled in the through-hole, being one of the plurality of through-holes h constituting the via hole 10, in the ceramic layer S1 of the outermost layer forming the surface 3 of the substrate body 2, and a through-hole conductor T that is formed along the inner-wall face of the through-hole, being one of the plurality of through-holes h forming the via hole 10, in the ceramic layer S2 other than the ceramic layer S1 of the outermost layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, a via conductor continuously penetrates a plurality of laminated ceramic layers, and the front and back surfaces of the outermost ceramic layer where the end face of the via conductor is exposed are flat and wiring with which an electronic component or the like can be mounted with high accuracy is provided. The present invention relates to a substrate and a manufacturing method thereof.

  In the manufacturing process of a multilayer ceramic wiring board formed by laminating a plurality of ceramic layers and conductor layers arranged between them, in order to facilitate the conveyance of the green sheet serving as the ceramic layer, a carrier sheet is provided on one surface thereof. In the pasted state, a through hole that becomes a via hole may be drilled, and the through hole may be filled with conductive ink. When a multilayer ceramic wiring board is manufactured by laminating the green sheets, the via conductor extends in the axial direction due to the thickness equivalent to the carrier sheet or excessive filling of the conductive ink into the via hole, In some cases, the surface of the outermost ceramic layer is pushed outward.

For example, a via conductor formed in a via hole having a plurality of insulating layers made of ceramic and a conductor layer disposed between each of them and passing through in the thickness direction of the conductive layer is excessive. In some cases, the filling causes a push-up extending in the axial direction, and the surface conductor formed between the outermost insulating layer and the insulating layer adjacent to the outermost insulating layer is deformed into an outwardly convex shape. In order to avoid the influence of the convex portion and to place the capacitor in the substrate, there is no conductor inside the electrode conductor located immediately above the convex portion and disposed on the surface of the outermost insulating layer. There has been proposed a multilayer substrate in which a part of the hole is formed (for example, see Patent Document 1). The surface conductor, the outermost insulating layer, and the electrode conductor constitute a capacitor in the multilayer substrate.
JP-A-2005-347567 (pages 1 to 13, FIG. 1)

By the way, as described above, when a push-up by a via conductor penetrating a plurality of ceramic layers along their thickness direction occurs, not only the surface of the outermost ceramic layer does not become flat, but also a via exposed on the surface. When an electronic component such as a semiconductor chip is mounted via an external connection pad formed on the end face of the conductor, the pad itself does not become flat. As a result, the electrical connection between the electronic component and the pad becomes unstable, and the operation of the mounted electronic component may be insufficient.
Alternatively, when the via conductor accompanied by the push-up is exposed on the back surface of the outermost ceramic layer, the conductor pin to be connected is soldered at a required position and posture via a pad formed on the end surface of the via conductor. In some cases, it could not be attached.

  The present invention solves the problems described in the background art, and even if the via conductor continuously penetrates the plurality of ceramic layers in the axial direction, the end surface of the via conductor is exposed. It is an object of the present invention to provide a wiring board capable of flattening the back surface and mounting electronic components and the like on the front and back surfaces with high accuracy and a method for manufacturing the same.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problem, the present invention provides a part excluding the ceramic layer which is the outermost layer when forming a via conductor in a via hole including a plurality of through holes penetrating a plurality of ceramic layers along the thickness direction. The idea is to form a through-hole conductor having a space at the center of the through hole of the ceramic layer.
That is, the wiring board of the present invention (Claim 1) is formed by laminating a plurality of ceramic layers including a ceramic layer in which a through hole is formed, and has a substrate body having a front surface and a back surface, and a surface of the substrate body or A via hole that opens in at least one of the back surfaces and has a plurality of through holes continuous along the thickness direction of the substrate body, and of the plurality of through holes that form the via holes, forms the front and back surfaces of the substrate body. A via conductor filled in at least one through-hole of the outermost ceramic layer and a plurality of through-holes forming the via hole along an inner wall surface of the through-hole of the ceramic layer other than the outermost ceramic layer And a through-hole conductor formed.

  According to this, since the through hole conductor is formed in the through hole of any ceramic layer except the outermost layer in the via hole in which the through holes formed for each of the plurality of ceramic layers are continuous, the through hole The conductor absorbs in advance the expansion of the adjacent via conductor due to the push-up in the step of laminating and crimping a plurality of green sheets at the time of manufacture. For this reason, the end surface of the via conductor exposed on at least one of the front surface and the back surface of the outermost ceramic layer is flush with or substantially flush with the front and back surfaces. Therefore, it is possible to mount electronic components with high precision through the end face of the via conductor exposed on the front and back surfaces of the substrate body and the pads formed on the front and back surfaces by connecting to the via conductor and external connection. The conductor pins for use can be fixed in a predetermined position and posture by soldering or the like.

The ceramic of the ceramic layer includes a high-temperature fired ceramic such as alumina, or a low-temperature fired ceramic containing about 50 wt% of a glass component.
For the conductor including the via conductor and the through-hole conductor, W or Mo is used when the ceramic of the ceramic layer is made of high-temperature fired ceramic, and Ag or Cu is used when the ceramic is low-temperature fired ceramic. Is used.
Further, the via hole has a continuous form from the through hole of the ceramic layer on the front surface side or the back surface side of the substrate body to the through hole of the ceramic layer of the middle layer, and all the ceramic layers between the front surface and the back surface of the substrate body. The through holes may be continuous.
Further, the ceramic layer in which the through-hole conductor is formed in the through hole is any one of the ceramic layers excluding the outermost ceramic layer. For example, a ceramic layer adjacent to the inside of the outermost ceramic layer in which the via conductor is filled in the through hole, or a ceramic layer positioned further inside than the ceramic layer may be used. The via conductor is connected to at least one of both end faces in the axial direction of the through-hole conductor, and the via conductor or a wiring layer inside the substrate is connected to the other.
Further, the through-hole conductor is substantially a cylinder that was originally located in the center due to the pressure when laminating and crimping a plurality of ceramic layers including the ceramic layer in which the through-hole conductor is formed in the manufacturing process described later. The space of the shape may have an irregular shape such as a drum shape.
In addition, the through-hole conductor has an outer peripheral portion along the inner wall surface of the through-hole, and a current mainly flows through the surface layer near the outer peripheral portion. Therefore, the electric resistance is almost smaller than that of the via conductor. Do not increase.

The present invention also includes a wiring board (Claim 2) in which the through-hole conductor is formed along an inner wall surface of a through hole that penetrates the ceramic layer having a thickness of 100 μm or more after firing. .
According to this, since the through-hole conductor is formed along the inner wall surface of the through-hole penetrating the relatively thick ceramic layer having a thickness of 100 μm or more after firing, one opening in the through-hole at the time of manufacturing is formed. It can be easily applied and formed while a conductive ink or the like is sucked from the other opening in a state where the portion is at a negative pressure. Moreover, since the through-hole conductor can be formed by sucking and applying conductive ink or the like in the through-hole of the relatively thick ceramic layer, such a manufacturing process is facilitated.
Furthermore, the present invention includes a wiring board (Claim 3) in which a part of the via conductor enters at least one opening in the axial direction of the through-hole conductor.
According to this, since a part of the adjacent via conductor enters one or both openings in the axial direction of the through-hole conductor, the electrical connection between the through-hole conductor and the via conductor can be stabilized. Is possible.

  On the other hand, the method for manufacturing a wiring board according to the present invention (Claim 4) includes a step of forming through holes in a plurality of green sheets having a thickness after firing of 100 μm or more or less than 100 μm, and at least a lamination of the green sheets. A step of filling the through hole formed in the outermost green sheet in the process with a conductive paste to form a via conductor, and an inner wall surface of the through hole formed in the green sheet other than the outermost green sheet And forming a through-hole conductor by disposing a conductive paste in an annular shape, and a plurality of green sheets on which at least the via conductor and the through-hole conductor are formed, the via conductor and the through-hole conductor And laminating so as to be continuous along the axial direction.

According to this, a via conductor is formed in the through hole of the green sheet which is the outermost layer in the lamination process, and a through hole conductor is formed in the through hole of any green sheet of the green sheet other than the outermost layer. A plurality of the green sheets are laminated and pressure-bonded so as to form a via hole having continuous holes. As a result, a through-hole conductor is inserted into any through-hole of the ceramic layer except the outermost ceramic layer in the via hole penetrating along the thickness direction of the plurality of ceramic layers constituting the substrate body, and the other ceramics. Via conductors are formed substantially coaxial with each other in the through-holes of the layers. Accordingly, the via conductor and the through-hole conductor can be sufficiently electrically connected, and the end surface of the via conductor exposed on at least one of the front and back surfaces of the substrate body is substantially flush with the front and back surfaces. The substrate can be reliably manufactured.
In addition, the said green sheet whose thickness after baking is 100 micrometers or more or less than 100 micrometers is what divided | segmented these by relative thickness.
In addition, the through holes formed for each of the plurality of green sheets may include those having different inner diameters as long as they are concentric in the stacking step.
Further, any of the green sheets other than the outermost layer includes one in which a via conductor is formed in the through hole.
In addition, in the through-hole conductor, the substantially cylindrical space originally located in the center portion has an irregular shape such as a drum shape, and the space is reduced to a very small gap. Including.

The present invention also includes a method for manufacturing a wiring board (Claim 5), wherein the green sheet on which the through-hole conductor is formed has a thickness after firing of 100 μm or more.
According to this, along the inner wall surface of the through hole that penetrates a relatively thick green sheet having a thickness of 100 μm or more after firing, the other opening in the through hole has a negative pressure. A through-hole conductor can be easily formed by applying and forming conductive ink or the like from the opening of the substrate. Moreover, since the through-hole conductor can be formed by sucking and applying conductive ink or the like in the through-hole of the relatively thick green sheet, such a manufacturing process is facilitated.

Further, according to the present invention, the green sheet including the carrier sheet attached to one surface and through which the through hole penetrates is filled with the conductive paste to form a via conductor, and then the carrier sheet is peeled off. Also included is a method for manufacturing a wiring board (claim 6).
According to this, since the through hole is formed including the carrier sheet attached to one surface of the green sheet, and the via conductor is formed in the through hole, the carrier sheet is peeled off. Only a part of the via conductor protrudes on one surface of the green sheet. For this reason, as will be described below, by laminating a plurality of ceramic layers while pressing the convex portion of the via conductor against one opening in the axial direction of the adjacent through-hole conductor, Both conductors can be reliably connected in a state where a part of the via conductor enters the opening.
In addition, a carrier sheet is attached to one surface of any of the plurality of green sheets, and the through holes are formed coaxially in the carrier sheet.
Further, a resin film such as polyethylene terephthalate (hereinafter referred to as PET) is used for the carrier sheet.
Furthermore, it is desirable that the carrier sheet is attached to one side of a green sheet having a size of at least less than 100 μm.

In addition, according to the present invention, the green sheet from which the carrier sheet has been peeled is formed by laminating the protruding portion of the via conductor protruding on one side of the green sheet adjacent to the green sheet in the stacking step, and A method for manufacturing a wiring board is also included in which the green sheet on which the through-hole conductor is formed is laminated so as to enter one opening in the axial direction of the through-hole conductor.
According to this, by laminating a plurality of ceramic layers so as to push the convex portion of the via conductor toward one opening in the axial direction of the adjacent through-hole conductor, one opening in the through-hole conductor In a state in which a part of the via conductor has entered, both conductors can be securely and physically connected.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 is a cross-sectional view showing a main part of a wiring board 1a according to an embodiment of the present invention.
As shown in FIG. 1, the wiring board 1 a includes a plurality of ceramic layers S1 to S4, a substrate body 2 having a front surface 3 and a back surface 4, and through holes h formed at the same position for each of the ceramic layers S1 to S3. Are continuous along the thickness direction of the substrate body 2, and one end of the via hole 10 that opens to the surface 3, and among the plurality of through holes h forming the via hole 10, the uppermost layer (outermost layer) ceramic S 1 and the middle layer A via conductor V filled in the through-hole h of the ceramic S3 and a through-hole conductor T formed along the inner wall surface of the through-hole h of the middle-layer ceramic S2 sandwiched therebetween.
The ceramic layers S1 to S4 are mainly composed of alumina, for example, and the outermost ceramics S1 and S4 and the middle ceramic S3 are relatively thin with a thickness of about 50 μm (less than 100 μm), and the middle ceramic S2 is thick. Is relatively thick at about 110 μm (100 μm or more).

As shown in FIG. 1, the through-hole conductor T includes a substantially cylindrical body portion 12 along the inner wall surface of the through-hole h, a substantially hemispherical curved surface portion 13 positioned at both ends in the axial direction, And a space s that is substantially in the shape of a drum.
Further, wiring layers 5, 6, and 7 having a predetermined pattern are formed between the ceramic layers S1 to S4, and a via conductor located in the through hole h of the uppermost ceramic layer S1 is formed on the surface 3 of the substrate body 2. A pad 8 connected to V is formed. An electronic component such as a semiconductor chip mounted above the surface 3 is connected to the pad 8 via solder (none of which is shown). Between the wiring layers 5 and 6 and the via conductor V or the through-hole conductor T, an annular through hole 11 provided in the former is located.

Further, as shown in FIG. 1, a through hole h and a via conductor V are formed in a position different from the via hole 10 in a plan view in the lowermost layer (outermost layer) ceramic S4 and connected to the via conductor V. Pads 9 are formed on the back surface 4 of the substrate body 2. The head 14 of the conductor pin P is joined to the pad 9 in a posture in which the axial direction is orthogonal to the back surface 4 via solder (not shown). The wiring layer 7 connects the lowermost via conductor V via the via hole 10 and the via conductor V penetrating the ceramic layer S4.
The via conductor V, the through-hole conductor T, the wiring layers 5 to 7 and the pads 8 and 9 are made of W or Mo, and the conductor pin P is made of, for example, Fe-42 wt% Ni (42 alloy) or It consists of Cu-Fe-P alloy (194 alloy) etc.

FIG. 2 is a cross-sectional view showing a main part of a wiring board 1b having a different form.
As shown in FIG. 2, the wiring substrate 1 b includes the same substrate body 2 composed of a plurality of ceramic layers S 1 to S 4, the same via hole 10, and the plurality of through holes h forming the via hole 10. Via conductor V filled in through hole h of upper layer (outermost layer) ceramic S1 and middle layer ceramic S2, and through hole conductor T formed along the inner wall surface of through hole h of middle layer ceramic S3, I have.
The ceramic layers S1 to S4 are made of the same ceramic as described above, and the outermost layer ceramics S1 and S4 and the middle layer ceramic S2 have a thickness of about 60 μm (less than 100 μm), and the middle layer ceramic S2 has a thickness of about 120 μm (100 μm). Above).

As shown in FIG. 2, the through-hole conductor T includes a substantially cylindrical body portion 12 along the inner wall surface of the through hole h, a curved surface portion 13 that is located at the upper end in the axial direction and has a substantially hemispherical shape, And a space s surrounded by the wiring layer 7 connected to the lower end of the body portion 12 and having a substantially drum shape.
Further, the same wiring layers 5, 6, and 7 are formed between the ceramic layers S1 to S4, and the same pad 8 is formed on the surface 3 of the substrate body 2. Between the wiring layers 5 and 6 and the via conductor V or the through-hole conductor T, the same through hole 11 is located.
Further, as shown in FIG. 2, the lowermost ceramic S4 is provided with the same through hole h and via conductor V, and a pad 9 connected to the via conductor V is formed on the back surface 4 of the substrate body 2. ing. The wiring layer 7 connects the lowermost through-hole conductor T in the via hole 10 and the via conductor V penetrating the ceramic layer s4.

FIG. 3 is a cross-sectional view showing the main part of a further different form of the wiring board 1c.
As shown in FIG. 3, the wiring board 1c has the same substrate body 2 composed of a plurality of ceramic layers S1 to S4, a large-diameter through hole h formed in the ceramic layer S1, and the same positions of the ceramic layers S2 to S4. And a plurality of through-holes h forming the via holes 10, which are concentrically continuous with each other along the thickness direction of the substrate body 2, have both ends opened to the front surface 3 and the back surface 4. Among them, the via conductor V filled in the through holes h of the outermost layer ceramics S1 and S4 and the middle layer ceramic S2, and the relatively short axis formed along the inner wall surface of the remaining through holes h of the middle layer ceramic S3. Through-hole conductor T.
The ceramic layers S1 to S4 are made of the same ceramic as described above, and the outermost layer ceramics S1 and S4 and the middle layer ceramic S3 have a thickness of about 80 μm (less than 100 μm), and the middle layer ceramic S2 has a thickness of about 150 μm (100 μm). Above).

As shown in FIG. 3, the through-hole conductor T includes a substantially cylindrical short body portion 12 along the inner wall surface of the through hole h, a substantially hemispherical curved surface portion 13 positioned at both ends in the axial direction, A relatively small space s surrounded by these and having a substantially hourglass shape.
Further, the same wiring layers 5, 6, and 7 are formed between the ceramic layers S1 to S4, and the upper end surface of the large-diameter via conductor V is exposed on the surface 3 of the substrate body 2, and the via An electronic component is mounted directly on the upper end surface of the conductor V. Between the wiring layers 5, 6 and 7 and the via conductor V or the through-hole conductor T, the same through hole 11 is located.
Further, as shown in FIG. 3, the same pad 9 as that connected to the via conductor V formed in the lowermost ceramic S <b> 4 is formed on the back surface 4 of the substrate body 2.

FIG. 4 is a cross-sectional view showing a main part of a wiring board 1d which is an applied form of the wiring board 1a.
As shown in FIG. 4, the wiring board 1 d has a through hole h formed in the same position for each of the ceramic body S <b> 2 and the ceramic layers S <b> 2 to S <b> 4 having a plurality of ceramic layers S <b> 1 to S <b> 4. A via hole 10 that is continuous along the direction and has one end opened on the back surface 4, and among the plurality of through holes h that form the via hole 10, the lower layer (outermost layer) ceramic S4 and the middle layer ceramic S2 have a through hole h. And a through-hole conductor T formed along the inner wall surface of the through hole h of the middle-layer ceramic S3 sandwiched between them.
The ceramic layers S1 to S4 are made of the same ceramic as described above, and the outermost layer ceramics S1 and S4 and the middle layer ceramic S2 have a thickness of about 70 μm (less than 100 μm), and the middle layer ceramic S3 has a thickness of about 140 μm (100 μm). Above).

As shown in FIG. 4, the through-hole conductor T has a long-axis body 12 similar to the above, a pair of upper and lower curved surfaces 13, and a space s.
Further, the same wiring layers 5, 6, and 7 are formed between the ceramic layers S1 to S4, and the same pad 8 is formed on the surface 3 of the substrate body 2. Between the wiring layers 6 and 7 and the via conductor V or the through-hole conductor T, the same through hole 11 is located.
Further, as shown in FIG. 4, a through hole h and a via conductor V are formed in a different position from the via hole 10 in the uppermost ceramic S <b> 1, and a pad 8 connected to the via conductor V is a surface 3 of the substrate body 2. Is formed. The wiring layer 5 connects the uppermost via conductor V in the via hole 10 and the via conductor V penetrating the ceramic layer S1.

According to the wiring boards 1a to 1d as described above, in the via hole 10 in which the through holes h formed in the ceramic layers S1 and S4 including at least one outermost layer among the ceramic layers S1 to S4 are continuous, Since the through-hole conductor T is formed in one of the through holes h of the ceramic layers S2 and S3 excluding the outer layer, the through-hole conductor T is formed in a process of laminating and pressing a plurality of green sheets at the time of manufacture. The expansion due to the push-up of the adjacent via conductor V is absorbed in advance. For this reason, the end face of the via conductor V exposed to at least one of the front surface 3 and the back surface 4 of the outermost ceramic layers S1 and S4 is flush with or substantially flush with the front and back surfaces 3 and 4. Therefore, the electronic component can be mounted with high accuracy through the end surface of the via conductor V exposed on the front surface 3 and the back surface 4 of the substrate body 2 and the pads 8 and 9 formed in connection with the via conductor V. The conductor pins P can be joined by soldering or the like with the predetermined positions and postures.
Furthermore, in the wiring boards 1a, 1c, and 1d, the through-hole conductors T partially enter the upper and lower via conductors V adjacent to the openings at both ends in the axial direction, and a pair of upper and lower curved surface portions. 13 is formed, the electrical connection between the through-hole conductor T and the adjacent via conductor V can be stabilized.
Moreover, in the wiring boards 1a, 1b, and 1d, the through-hole conductor T is formed along the inner wall surface of the through hole h of the ceramic layers S2 and S3 having a thickness of 100 μm or more. It can be easily applied and formed.

Below, the manufacturing method of the said wiring board 1a is demonstrated.
A ceramic slurry is prepared by mixing and mixing required amounts of alumina powder, required organic binder, and solvent in advance, and this is formed into a plurality of green sheets s1 to s4 that have a sheet shape by the doctor blade method. did. Among these, the green sheets s1, s3, and s4 have a thickness after firing of about 50 μm (less than 100 μm), and the green sheet s2 has a thickness after firing of about 100 μm (100 μm or more). A carrier sheet cs having a thickness of about 40 μm is attached to one surface of the relatively thin green sheets s1 and s3. The carrier sheet cs is a film made of PET, for example.
Next, the green sheets s1 to s3 including the carrier sheet cs were punched at the same positions, and a plurality of through holes h were formed so as to be coaxial, as shown in FIG. On the other hand, a through hole h was drilled in the green sheet s4 at a position different from the above.

Next, a conductive paste (conductive ink) containing W powder or Mo powder is applied to the through holes h of the green sheets s1, s4, which will be outermost layers, and the green sheet s3, which will be the middle layer, and a metal mask and squeegee (not shown). As shown in FIG. 6, an unfired via conductor v having a substantially cylindrical shape was formed.
On the other hand, air is sucked from one opening to make a negative pressure inside the through-hole h of the relatively thick green sheet s2, which will be an intermediate layer, and the same conductive paste is sucked from the other opening. . As a result, as shown in FIG. 6, an unfired through-hole conductor t having a substantially cylindrical shape along the inner wall surface of the through hole h and having a through hole u at the center was formed.
In addition, on the front and back surfaces of the green sheets s1 to s4 where the end surfaces of the via conductors v and the through-hole conductors t are exposed, a part of the conductive paste (not shown) is around each through hole h, and the plan view is irregular. It protrudes in the form of a thin film so as to exhibit an annular shape.

Further, the same conductive paste as described above was formed in a predetermined pattern by screen printing on at least one of the front and back surfaces of the green sheets s1, s2, and s4.
As a result, as shown in FIG. 7, unfired pads 8 connected to the via conductors v are formed on the surface of the green sheet s1 as the uppermost layer, and on the front and back surfaces of the green sheet s2 as the middle layer, The wiring layers 5 and 6 having a predetermined pattern were formed apart from the through-hole conductor t. Further, a wiring layer 7 having a predetermined pattern and an unfired pad 9 were formed on the front and back surfaces of the green sheet s4 serving as the lowermost layer, connected to the via conductors v penetrating the green sheet s4.
Next, as shown in FIG. 8, the carrier sheet cs attached to one surface of the green sheets s1 and s3 was peeled off. As a result, protrusions p having a height substantially corresponding to the thickness of the carrier sheet cs out of the via conductors v penetrating the green sheets s1 and s3 individually protruded from the back surface or the front surface of the green sheets s1 and s3.

Next, as indicated by the arrows in FIG. 8, the green sheets s1 to s4 were laminated along the thickness direction and pressure-bonded. At this time, the through holes h for each of the green sheets s1 to s3 were substantially coaxially continuous, and the via conductors v and the through-hole conductors t formed thereon were connected to be laminated.
As a result, as shown in FIG. 9, the green sheets s1 to s4 are laminated to form the unfired substrate body 2 having the front surface 3 and the back surface 4, and the through holes h for each of the green sheets s1 to s3 are continuous. The via hole 10 was formed.
At this time, the through-hole conductor t in the relatively thick middle-layer green sheet s2 is provided with convex portions (parts) p of the via conductors v of the green sheets s1 and s3 stacked adjacent to each other. It was approaching while being pushed into the openings at both ends of the through hole u.

As a result, as shown in FIG. 9, the through-hole conductor t is formed along the inner wall surface of the through-hole h and the cylindrical portion 12 having a thick middle portion in the axial direction, and the upper and lower ends of the through-hole u. An unfired through-hole conductor T having a pair of curved surface portions 13 formed by the protrusions p and a space s surrounded by these and having a substantially drum shape was obtained.
The wiring layers 5 and 6 are formed between the green sheets s1 to s3 with the via conductors v and through-hole conductors t in the via holes 10 and the through holes 11 being placed.
Further, the wiring layer 7 and each via conductor v penetrating the green sheets s3 and s4 are connected, and the through-hole conductor t and the via conductor v in the via hole 10 are connected to the surface layer 3 side. The pad 8 and the pad 9 on the back surface 4 side can conduct each other.

In addition, in the vicinity of the position intersecting with the via hole 10 between the green sheets s1 to s4, a part of the conductive paste protrudes in a thin film shape so as to exhibit a ring shape having an irregular shape in plan view.
Then, the unfired substrate body 2 as described above was fired at a predetermined temperature zone. As a result, the wiring board 1a shown in FIG. 1 was obtained.
In the manufacturing method, the wiring board 1b is manufactured by switching the positions of the green sheet s2 and the green sheet s3, laminating and press-bonding the green sheets s1 and s4 in the same manner as described above, and further firing them. Can do.
Moreover, in the said manufacturing method, the said wiring board 1d can be manufactured by changing suitably the position which the said green sheets s1-s4 should laminate | stack, laminating | stacking and crimping | bonding these, and also baking.

Next, an outline of a method for manufacturing the wiring board 1c will be described.
As shown on the left side of FIG. 10, the same green sheet s2 having a thickness after firing of 150 μm and the same green sheets s3 and s4 having a thickness of 80 μm after firing were prepared. The same carrier sheet cs as described above is attached to the entire back surface or front surface of the green sheets s2 and s4. The green sheets s2 to s4 including the carrier sheet cs were punched at the same positions to form through holes h in each. A through hole h having a diameter larger than that of the through hole h was formed at the same position of the green sheet s1 as the uppermost layer (not shown).
Next, as shown on the right side of FIG. 10, each of the through holes h of the green sheets s2 and s4 and the green sheet s1 (not shown) is filled with the same conductive paste as described above to form an unfired via conductor v. . On the other hand, in the through hole h of the green sheet s3, an unfired through-hole conductor t with a short axis having a through hole u along the inner wall surface and in the center portion was formed by the same method as described above.

Further, the carrier sheet cs is peeled from the green sheets s2 and s4, and vias having a height corresponding to the thickness of the carrier sheet cs are formed on the back surface or front surface of the green sheets s2 and s4 as shown on the left side of FIG. The convex part p of the conductor v was protruded.
Next, wiring layers 5 to 7 were printed and formed on the surfaces of the green sheets s2 to s4 at intervals from the via conductors v and the through-hole conductors t.
Next, the green sheets s <b> 2 to s <b> 4 and the green sheet s <b> 1 (not shown) were laminated and pressure-bonded along the arrow on the left side of FIG. 11 so that the through holes h communicate with each other.
As a result, as shown on the right side of FIG. 11, via holes 10 in which through holes h of green sheets s2 to s4 and green sheet s1 (not shown) are concentric and continuous are formed, and the short-axis through-hole conductor t is The upper and lower convex portions p are deformed while being pushed from the axial direction, and have a substantially cylindrical body portion 12, a pair of upper and lower curved surface portions 13, and a space s surrounded by these and having a substantially drum shape. Through-hole conductors T and an unfired substrate body 2 including the conductors were formed.
As a result of firing the substrate body 2 in the same manner as described above, the wiring substrate 1c shown in FIG. 3 was obtained. The above manufacturing method includes a form in which the space s of the through-hole conductor t disappears and becomes a via conductor v in the laminating step.

FIG. 12 is a cross-sectional view showing a main part of a wiring board 1e which is a modification of the wiring board 1c. As shown in FIG. 12, the wiring board 1e has a small-diameter penetration formed in the same position of the large-diameter through hole h formed in the substrate body 2 and the ceramic layer S1 and the small-diameter ceramic layers S2 to S4. The hole h is concentrically continuous along the thickness direction of the substrate body 2, and the outermost layer among the via hole 10 having both ends opened on the front surface 3 and the back surface 4 and the plurality of through holes h forming the via hole 10. Via conductors V filled in the through holes h of the ceramics S1 and S4 and the intermediate ceramic S3, and a relatively long-axis through hole conductor T formed along the inner wall surface of the through holes h of the remaining intermediate ceramic S2. It is equipped with.
As shown in FIG. 12, the through-hole conductor T has the same body portion 12, a pair of upper and lower curved surface portions 13, and a space s as described above. The same wiring layers 5, 6, and 7 are formed between the ceramic layers S1 to S4, and the end surface of the large-diameter via conductor V is exposed and mounted on the surface 3 of the substrate body 2. Used for connection to electronic components. Further, the same pad 9 as described above is formed on the back surface 4 of the substrate main plate 2.

FIG. 13 shows a manufacturing method of the wiring board 1e. As shown in the drawing, a large-diameter via conductor v having the same convex portion p is formed in the through hole h of the green sheet s1 as the uppermost layer, and the through hole h of the green sheet s2 in the middle layer is formed in the through hole h. The same through-hole conductor t is formed, and the via conductor v having the same convex portion p is formed in the through hole h of the other middle-layer green sheet s3, and the through-hole h of the green sheet s4 serving as the lowermost layer is formed. A via conductor v was formed. In addition, the same wiring layers 5 to 7 were printed and formed on the front surfaces of the green sheets s2 to s4, and the pads 9 were formed on the back surface of the green sheets s4.
Then, as indicated by the arrows in FIG. 13, when the green sheets s1 to s4 are pressure-bonded and laminated, the convex portions p of the green sheets s1 and s3 are inserted into the through holes u of the through-hole conductors t of the green sheet s2. The through-hole conductor T was formed by entering, and these were baked to obtain the wiring board 1e.

  According to the method of manufacturing the wiring boards 1a to 1e as described above, the via conductors v are formed in the through holes h of the green sheets s1 and s4 that are the outermost layers in the stacking process, and the green sheets s2 and s3 other than the outermost layers are formed. The green sheets 1a to 1d are laminated and pressure-bonded so that the through-hole conductor t is formed in any one of the through-holes h, and the via-hole 10 in which the through-holes h are continuous is formed. As a result, the ceramic layers S2 excluding the outermost ceramic layers S1 and S4 are inserted into the via holes 10 penetrating along the thickness direction of the plurality of ceramic layers S1 to S3 or the ceramic layers S2 to S4 constituting the substrate body 2. A through-hole conductor T is formed in one of the through holes h of S3, and a via conductor V is formed substantially coaxially in the through-holes h of the other ceramic layers S2 and S3.

Therefore, the electrical connection between the via conductor V and the through-hole conductor T is sufficiently possible, and the wiring substrates 1a to 1e in which the end surfaces of the via conductor V exposed on the front surface 3 and the back surface 4 of the substrate body 2 are flat are reliably provided. Can be manufactured.
Further, in the wiring boards 1a, 1c, 1d, and 1e, the through-hole conductors T have a pair of upper and lower via conductors V that are adjacent to the openings at both ends in the axial direction, and a pair of upper and lower via conductors V enter. Therefore, the electrical connection between the through-hole conductor T and the adjacent via conductor V can be stabilized.
In addition, in the wiring boards 1a, 1b, 1d, and 1e, the through-hole conductor T is formed along the inner wall surface of the through hole h of the ceramic layers s2 and s3 having a thickness of 100 μm or more. It can be formed by easily applying a functional paste or the like.

The present invention is not limited to each form and each manufacturing method described above.
For example, the wiring board of the present invention has a substrate body in which a plurality of ceramic layers each having a thickness after firing of less than 100 μm are laminated, and the through-hole conductor is formed on any middle ceramic layer, A form having a via conductor that is continuous with the through-hole conductor and exposed on at least one of the front surface and the back surface of the substrate body is also included.
Alternatively, the present invention includes a substrate body in which a plurality of ceramic layers each having a thickness after firing of 100 μm or more are laminated, and the through-hole conductor is formed on any middle ceramic layer, and the through-hole conductor And a wiring board having a via conductor exposed to at least one of the front surface and the back surface of the substrate body.
Further, the ceramic of the ceramic layer or the green sheet is not limited to alumina, but may be mullite, aluminum nitride, or the like, or a low-temperature fired ceramic containing about 50 wt% of a glass component.

Furthermore, the ceramic layer and the green sheet may have five or more layers, and the substrate main body may have five or more ceramic layers.
A plurality of sets of the via holes, via conductors, and through-hole conductors may be formed at arbitrary positions along the thickness direction of the substrate body.
Furthermore, a wiring layer formed between the ceramic layers may be sandwiched and connected between via conductors and through-hole conductors formed in the via holes.
In addition, the method of manufacturing the wiring board can be performed using a plurality of green sheets having no carrier sheet attached to one side, and in particular, a relatively thin green having a thickness of less than 100 μm after firing the through-hole conductor. It is suitable when it is formed in the through hole of the sheet.
In addition, the method of manufacturing the wiring board may be performed as a multi-cavity method using a large green sheet.

Sectional drawing which shows the principal part of the wiring board of one form by this invention. Sectional drawing which shows the principal part of the wiring board of a different form. Furthermore, sectional drawing which shows the principal part of the wiring board of a different form. Sectional drawing which shows the principal part of the wiring board which is an application form of the wiring board of FIG. Schematic which shows one manufacturing process for obtaining the wiring board of FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. FIG. 4 is a partial schematic view showing a manufacturing process for obtaining the wiring board of FIG. 3. FIG. 11 is a partial schematic diagram illustrating a manufacturing process subsequent to FIG. 10. Sectional drawing which shows the principal part of the wiring board of the deformation | transformation form of the wiring board of FIG. Schematic which shows one manufacturing process for obtaining the wiring board of FIG.

Explanation of symbols

1a to 1e ... wiring board 2 ..... substrate body 3 ..... front surface 4 ........... back surface 10 ..... via hole S1-S4 ... ceramic layer s1-s4 ... green sheet h .... …… Through hole V, v ……… via conductor T, t ……… through hole conductor cs ………… carrier sheet

Claims (7)

A plurality of ceramic layers including a ceramic layer having through holes formed thereon, and a substrate body having a front surface and a back surface;
A via hole that is opened in at least one of the front surface and the back surface of the substrate body, and the plurality of through holes are continuous along the thickness direction of the substrate body;
Among the plurality of through holes constituting the via hole, via conductors filled in at least one through hole of the outermost ceramic layer forming the front surface and the back surface of the substrate body,
A through-hole conductor formed along the inner wall surface of the through hole of the ceramic layer other than the ceramic layer of the outermost layer among the plurality of through holes forming the via hole,
A wiring board characterized by that. The through-hole conductor is formed along the inner wall surface of the through hole that penetrates the ceramic layer having a thickness of 100 μm or more after firing.
The wiring board according to claim 1. A part of the via conductor enters at least one opening in the axial direction of the through-hole conductor,
The wiring board according to claim 1 or 2, wherein Forming through holes in a plurality of green sheets having a thickness after firing of 100 μm or more or less than 100 μm;
Among the green sheets, at least a step of forming a via conductor by filling a conductive paste into the through-hole formed in the green sheet that is the outermost layer in the lamination step;
A step of forming a through-hole conductor by arranging a conductive paste in an annular shape along the inner wall surface of the through hole formed in a green sheet other than the green sheet as the outermost layer;
Laminating a plurality of green sheets formed with at least the via conductor and the through-hole conductor such that the via conductor and the through-hole conductor are continuous along the axial direction.
A method of manufacturing a wiring board. The thickness after firing of the green sheet on which the through-hole conductor is formed is 100 μm or more.
The method for manufacturing a wiring board according to claim 4. The green sheet including the carrier sheet attached to one surface and penetrating the through hole is filled with the conductive paste to form a via conductor, and then the carrier sheet is peeled off.
The method for manufacturing a wiring board according to claim 4 or 5, wherein: The green sheet from which the carrier sheet has been peeled is formed by forming the via conductor protrusion protruding on one side of the green sheet adjacent to the green sheet and forming the through-hole conductor in the stacking step. Laminated so as to enter one opening in the axial direction of the through-hole conductor of the sheet,
The method for manufacturing a wiring board according to claim 6.

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