Wiring substrate

A Wiring substrate includes a substrate body that is formed from ceramics, and that includes a front surface, a back surface, and side surfaces positioned between peripheral sides of the front surface and the back surface; a frame-shaped metalized layer (surface conductor portion) that is formed on the front surface of the substrate body, a surface of the frame-shaped metalized layer being covered with a metal plating film; and an electroplating conductor layer that is formed in the substrate body, an end of the electroplating conductor layer being electrically connected to the frame-shaped metalized layer, the other end of the electroplating conductor layer being formed at the front surface of the substrate body, the other end of the electroplating conductor layer being electrically independent of different conductor portions that differ from frame-shaped metalized layer, the electroplating conductor layer being separated from the side surfaces of the substrate body. An opening portion for exposing at least a portion of the electroplating conductor layer at a bottom surface is formed in the front surface of the substrate body.

TECHNICAL FIELD

The present invention relates to a wiring substrate in which, even if, for example, a surface of a ceramic substrate body is provided with, for example, a non-conducting surface conductor portion that is not electrically connected to an external connection conductor, a surface of, for example, the surface conductor portion is reliably covered with an electrolytic metal plating film.

BACKGROUND ART

For example, an invention pertaining to a method for producing a semiconductor-device accommodating package that is described below is proposed (refer to, for example, Patent Literature 1). In the method, at least one of a single long pad that has been short-circuited in its entirety or a plurality of pads is/are formed at a side surface of an insulating body. In the method, by bringing a plurality of external lead terminals provided vertically from the same frame member into contact with either the pad or the pads, surfaces of a plurality of wiring metallized layers can be covered with metal plating films by electroplating, the wiring metallized layers being provided at the side of a bottom surface of a cavity that opens at a surface of the insulating body and being individually electrically connected to the pad or the pads.

However, in the case of the semiconductor-device accommodating package having the above-described structure, after the plating, the unnecessary plurality of pads that are formed on the side surface of the insulating body need to be ground and removed. However, end surfaces of respective internal wirings are exposed at the side surface of the insulating body after the pads have been removed. This may cause, for example, electrically unintentional short circuits to occur.

On the other hand, when there are metalized layers which are formed on a surface of a ceramic substrate body, which have the shape of a rectangular frame in plan view, which have a relatively small width, and which are used for sealing a cavity, and a non-conducting pad in which electric current does not flow among relatively small pads that are provided at the surface of the base body or at the side of the bottom surface of the cavity that opens at the surface of the base body, Ni plating films and Au plating films are successively applied to the surfaces of the metalized layers and the surface of the non-conducting pad by electroplating while an electrode pin, which is pointed at one end, point-contacts the surfaces of the metalized layers and the surface of the non-conducting pad.

However, when the electrode pin is brought into point-contact or a peripheral surface of the electrode pin is brought into line-contact with the surfaces of the metallized layers and the surface of the pad, the surfaces of the metallized layers and the surface of the pad are scratched when portions of contact are unintentionally shifted. Moreover, when the width of the metalized layers is small and the non-conducting pad is small, if the electrode pin is dislodged, electroplating sometimes can no longer be performed. Further, when an electrode conductor portion for contact with the electrode pin separately protrudes from the surface of the substrate body at the outer side of the metalized layers, the size of the substrate body is increased.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

It is an object of the prevent invention to provide a wiring substrate that can solve the problems described in the background art, and in which, even if, for example, a surface of a ceramic substrate body is provided with a surface conductor portion that is not electrically connected to an external connection conductor, and a bottom-surface side of a cavity that opens at the surface of the substrate body is provided with a surface conductor portion that is not electrically connected to an external connection conductor, these surfaces are reliably covered with metal plating films by electroplating, scratches on such surfaces caused by contact with an electrode pin are less likely to be conspicuous, and the substrate body can be reduced in size.

Solution to Problem and Advantageous Effects of Invention

To this end, the present invention is achieved based on the idea of forming an opening portion in which an electrode pin can be inserted in at least one of a front surface or a back surface of a ceramic substrate body, and causing an electroplating conductor layer whose one portion is exposed at a bottom surface defining the opening portion and a surface conductor portion that needs to be covered with a metal plating film to be capable of being electrically conductive with each other.

That is, a first wiring substrate according to the present invention (Claim1) includes a substrate body that is formed from ceramic, and that includes a front surface, a back surface, and side surfaces positioned between the front surface and the back surface; a surface conductor portion that is formed on at least one of the front surface or the back surface of the substrate body, a surface of the surface conductor portion being covered with a metal plating film; and an electroplating conductor layer that is formed in the substrate body, an end of the electroplating conductor layer being electrically connected to the surface conductor portion, the other end of the electroplating conductor layer being formed at the front surface or the back surface of the substrate body, the other end of the electroplating conductor layer being electrically independent of a different conductor portion that differs from the surface conductor portion, the electroplating conductor layer being separated from the side surfaces of the substrate body. An opening portion for exposing at least a portion of the electroplating conductor layer is formed in at least one of the front surface or the back surface of the substrate body.

In the foregoing description, the phrase “an electroplating conductor layer that is formed in the substrate body, an end of the electroplating conductor layer being electrically connected to the surface conductor portion, the other end of the electroplating conductor layer being formed at the front surface or the back surface of the substrate body, the other end of the electroplating conductor layer being electrically independent of a different conductor portion that differs from the surface conductor portion, the electroplating conductor layer being separated from the side surfaces of the substrate body” may also be expressed by the phrase “an electroplating conductor layer that is formed in the substrate body, an end of the electroplating conductor layer being electrically connected to the surface conductor portion, the other end of the electroplating conductor layer being formed at the front surface or the back surface of the substrate body, the other end of the electroplating conductor layer being electrically independent of a different conductor portion that differs from the surface conductor portion, the electroplating conductor layer not being exposed at the side surfaces of the substrate body”.

According to this structure, the surface conductor portion is electrically connected to the end portion of the electroplating conductor layer having the portion that is exposed at the opening portion formed in at least one of the front surface or the back surface of the substrate body. Therefore, even if, for example, the front surface of the substrate body is largely occupied by a different conductor portion, the surface conductor portion can be electrically conductive with the electroplating conductor layer through, for example, a via conductor. Therefore, by inserting an end portion of an electrode pin, which is used for electroplating, from the opening portion, and by bringing the end portion of the electrode pin into contact with the portion of the electroplating conductor layer that is exposed at the opening portion, the surface of the surface conductor portion is reliably covered with a metal plating film, such as an Ni plating film or an Au plating film. Consequently, the Wiring substrate is one in which the surface of the surface conductor portion that is electrically independent of a different conductor layer, such as an external connection conductor, when in use is reliably covered with a metal plating film.

Moreover, since the portion of the electroplating conductor layer is exposed at the opening portion, it is less likely for the end portion of the electrode pin, used for electroplating, that is inserted in the opening portion to be shifted and dislodged from the opening portion; and, even if scratches, such as indentations, are produced by the pin, since such scratches are positioned at the side of the bottom surface defining the opening portion, these scratches are less likely to be conspicuous. Further, since the electroplating conductor layer is formed in the substrate body and the portion thereof is exposed at the opening portion, it is possible to prevent unintentional short circuits, which occurred in the past, from occurring, and to easily reduce the size of the substrate body.

The word “ceramic” refers to high-temperature fired ceramic, such as alumina, mullite, and aluminum nitride, and low-temperature fired ceramic, such as glass-ceramic.

In addition to having the shape of a plate having a flat surface, the substrate body may have a cavity that opens at the front surface towards the center of the surface.

Further, when in use, the surface conductor portion is a non-conducting conductor portion that is electrically independent of a different conductor layer, such as an external connection conductor, that is electrically connected to a terminal formed on a mother board. Examples of the surface conductor portion include a frame-shaped metalized layer (cavity sealing metalized layer) for mounting a metallic cover plate or a metallic frame member for sealing a cavity, and a non-conducting external connection terminal that is electrically independent of a different conductor layer. In contrast, when in use, the different conductor portion is a conductor portion that is electrically connected to the terminal of the mother board.

For the surface conductor portion, the electroplating conductor layer, a via conductor, wiring layers which are conductor portions different from the surface conductor portion, and a connection wiring, the following materials are used. For example, W, Mo, or an alloy based on either one of W and Mo is used when the ceramic of the substrate body is a high-temperature fired ceramic; and, for example, Ag or Cu is used when the ceramic of the substrate body is a low-temperature fired ceramic.

a pointed end portion of a power-feeding pin for feeding electric current for electroplating to the surface of the surface conductor portion point-contacts the portion of the electroplating conductor layer that is exposed at a bottom surface defining the opening portion (exposed surface).

Further, the opening portion is formed so as to extend in a thickness direction through an outermost ceramic layer that forms the front surface or the back surface of the substrate body or the ceramic layer and a ceramic that is adjacent to the ceramic layer.

In addition, examples of the metal plating film include an Ni plating film and an Au plating film.

According to the Wiring substrate of the present invention (Claim2), the surface conductor portion may be a frame-shaped metalized layer for sealing a cavity that opens at the front surface of the substrate body, the frame-shaped metalized layer being formed along an opening portion of the cavity, or may be a portion of an external connection conductor that is formed on the front surface or the back surface of the substrate body.

According to this structure, even if the width of the frame-shaped metalized layer is relatively small, and the area of the external connection conductor that is non-conducting when in use is relatively small, it is possible to provide a Wiring substrate in which the surfaces thereof are reliably covered with required metal plating films through the electroplating conductor layer and a conductor portion that is electrically conductive with the electroplating conductor layer.

The external connection conductor is one in which electric current does not flow when in use. For example, the external connection conductor is used as a dummy pad that forms part of a pattern used in image processing, a dummy element mounting pad for stabilizing the orientation of an element to be mounted, or an alignment mark for positioning the Wiring substrate.

Further, according to the Wiring substrate of the present invention (Claim3), the substrate body may have a cavity that opens at the front surface thereof, and a non-conducting pad may be formed at a bottom-surface side of the cavity, the non-conducting pad being the surface conductor portion.

According to this structure, even if the non-conducting (dummy) pad is relatively small, for example, even if the area of the non-conducting pad is relatively smaller than the area of the element mounting pad for mounting, for example, an electronic component to be mounted, it is possible to provide a Wiring substrate in which a surface thereof is reliably covered with a required metal plating film through the electroplating conductor and a conductor that is electrically conductive therewith.

The bottom-surface side of the cavity refers to, in addition to the bottom surface defining the cavity, a horizontal surface of a stepped portion that is located relatively close to the periphery of the bottom surface.

A single element mounting pad for mounting, for example, an electronic component to be mounted in the cavity is formed at the central portion of the bottom surface defining the cavity. When the surface area of the mounting pad is relatively wide, the mounting pad is not regarded as the surface conductor portion according to the present invention. However, when a plurality of element mounting pads are provided and when one or more of the plurality of element mounting pads are non-conducting (dummy) element mounting pads, the non-conducting element mounting pad or pads are regarded as the surface conductor portion.

According to the Wiring substrate of the present invention (Claim4), the surface conductor portion and the electroplating conductor layer are capable of being electrically conductive with each other through at least one of a via conductor or a connection wiring.

According to this structure, in the thickness direction of the front and back surface of the substrate body or in the direction along the front and back surface, separation of the surface conductor portion and the electroplating conductor layer according to arrangement positions thereof is reliably prevented, so that they can be electrically connected to each other. Therefore, it is possible to reliably cover the surface of the surface conductor portion with the metal plating film.

The surface conductor portion and the electroplating conductor layer may be capable of being electrically conductive with each other through one via conductor or a plurality of the via conductors and one connection wiring (wiring layer) or a plurality of the connection wirings formed in the substrate body, on the front surface of the substrate body, or on the back surface of the substrate body.

According to the Wiring substrate of the present invention (Claim5), the opening portion may be a bottomed hole, and a portion of the electroplating conductor layer is exposed at a bottom surface defining the bottomed hole.

According to this structure, it is possible to insert an end portion of an electrode pin, which is used for electroplating, from the opening portion, and to easily bring the end portion of the electrode pin into contact with the portion of the electroplating conductor layer (plating surface electrode) that is exposed at the bottom surface defining the bottomed hole. In addition, even if the electrode pin is shifted in a radial direction of the bottomed hole, the state of contact between the end portion and the exposed surface of the electroplating conductor layer is easily maintained. Therefore, a Wiring substrate in which the surface of the surface conductor portion is reliably covered with a required metal plating film is provided.

Examples of the shapes of the bottomed hole that becomes the opening portion include a circular shape in plan view and a circular cylindrical shape as a whole; an elliptical shape in plan view and an elliptical cylindrical shape as a whole; an oblong shape in plan view and a long circular cylindrical shape as a whole; an inverted conical shape, an inverted elliptical conical shape, and an inverted long conical shape in which the bottom-surface side of the bottomed hole is narrow; and a polygonal shape having three or more sides in plan view and the shape of a polygonal prism that is at least a triangular prism as a whole. The portion, which is flat, of the electroplating conductor portion is exposed at the bottom surface defining the bottomed hole having any of the shapes mentioned above.

According to the Wiring substrate of the present invention (Claim6), a wall surface conductor layer that is electrically connected to the electroplating conductor layer may be formed at an inner wall surface defining the bottomed hole.

According to this structure, even if, for example, an electrode pin is shifted in the radial direction of the bottomed hole by an external force that is unintentionally applied, since the end portion reliably contacts the wall-surface conductor layer, it is possible to provide a Wiring substrate in which the surface of the surface conductor portion is reliably covered with a required metal plating film.

According to the Wiring substrate of the present invention (Claim7), the surface conductor portion and the electroplating conductor layer may be electrically connected to each other through the wall surface conductor layer and the connection wiring formed on the front surface or the back surface of the substrate body.

According to this structure, for example, at the front surface or the back surface of the substrate body, the surface conductor portion and the electroplating conductor layer can be electrically conductive with each other through the connection wiring having a relatively small width and the wall surface conductor layer formed on the inner wall surface defining the bottomed hole. Therefore, by forming the connection wiring at any location on the back surface or between other conductors at the front surface or the back surface of the substrate body, it is possible to minimize the volume (region) of the inside of the substrate body that is occupied to provide a Wiring substrate in which the surface of the surface conductor portion is reliably covered with a required metal plating film.

DESCRIPTION OF EMBODIMENTS

Embodiments for carrying out the invention are hereunder described.

FIG. 1is a plan view of a Wiring substrate1according to an embodiment of the present invention.FIG. 2is a partial sectional view along line X-X inFIG. 1in the direction of the arrows.FIG. 3is a partial sectional view along line Y-Y inFIG. 1in the direction of the arrows.

As shown inFIGS. 1 to 3, the Wiring substrate1includes a substrate body2having the shape of a plate as a whole, a frame-shaped metalized layer (surface conductor portion)15formed on a front surface3of the substrate body2, an electroplating conductor layer16formed in the substrate body2, and a bottomed hole (opening portion)19formed near the upper right corner of the front surface3of the substrate body2.

The substrate body2has the front surface3and a back surface4that are square-shaped (rectangular) in plan view, and four side surfaces5that are positioned between the peripheral sides of the front surface3and the back surface4. The substrate body2is one in which ceramic layers C1to C4are integrally laminated upon each other.

The ceramic of the ceramic layers C1to C4is a high-temperature fired ceramic, such as alumina, or a low-temperature fired ceramic, such as glass-ceramic.

As shown inFIGS. 1 to 3, a cavity6that is square-shaped in plan view opens at a center side in the front surface of the substrate body2. The cavity6is defined by a bottom surface7that is square-shaped in plan view, side surfaces9that are formed vertically from the peripheral sides of the bottom surface7and that have the shape of a quadrangular column as a whole, and a stepped portion8that is close to a bottom-surface-7side of each side wall9and that has the shape of a rectangular frame in plan view. A single element mounting pad10that is rectangular in plan view is formed on substantially the entire bottom surface7excluding the peripheral portions of the bottom surface7. A semiconductor device20and the like are mounted later on a top surface of the element mounting pad10with an adhesive.

A plurality of element connection terminals (different conductor portions)11are formed on a surface (horizontal surface) of the stepped portion8. The element connection terminals11and the semiconductor device20can be electrically conductive with each other through a plurality of bonding wires wi. The frame-shaped metalized layer15is formed along the vicinity of an open portion of the cavity6.

A plurality of external connection conductors (different conductor portions)14are formed at the peripheral sides of the front surface3of the substrate body2. One side of each external connection conductor14is exposed at its corresponding side surface5. Each external connection conductor14is rectangular in plan view. As shown inFIG. 1, an end portion of each of a plurality of leads Li is later individually joined to its corresponding external connection conductor14by, for example, brazing.

Further, as shown inFIG. 2, a portion of each element connection terminal11is formed between the ceramic layer C2and the ceramic layer C3, and a wiring layer12is formed between the ceramic layer C3and the ceramic layer C4. Portions of the element connection terminals11and the wiring layer12are electrically connected to the external connection conductors14through via conductors13that individually extend through the ceramic layer C3or the ceramic layer C4. The remaining portions of the element connection terminals11and portions of the external connection conductors14may be electrically independent of each other.

In addition, as shown inFIGS. 1 and 3, the bottomed hole19, which is circular in plan view, opens in the vicinity of the upper right corner of the front surface3of the substrate body2; and a portion (plating electrode surface)18at the other end side of the electroplating conductor layer16, which is formed between the ceramic layer C3and the ceramic layer C4, is exposed at a bottom surface defining the bottomed hole19. One end side of the electroplating conductor layer16is connected to a via conductor17that is connected to a lower surface of the frame-shaped metalized layer15in the vicinity of the upper right corner.

Moreover, as shown inFIGS. 1 and 3, the electroplating conductor layer16is separated from all of the side surfaces5of the substrate body2including the upper side surface and the right side surface so as not to be exposed at these side surfaces5. Further, the electroplating conductor layer16is electrically independent of the element connection terminals (different conductor portions)11and the external connection conductors (different conductor portions)14.

The element mounting pad10, the element connection terminals11, the wiring layer12, the via conductors13, the via conductor17, the external connection terminals14, the frame-shaped metalized layer15, and the electroplating conductor layer16are primarily made of, for example, W or Mo or an alloy based on either one of W and Mo when the ceramic forming the ceramic layers C1to C4is a high-temperature fired ceramic, such as alumina; and are primarily made of, for example, Cu or Ag or an alloy based on either one of Cu and Ag when the ceramic forming the ceramic layers C1to C4is a low-temperature fired ceramic, such as glass-ceramic. The element mounting pad10, an end side (element-mounting-pad-10side) of each element connection terminal11, each external connection conductor14, the frame-shaped metalized layer15, and a surface of a portion18of the electroplating conductor layer16that is exposed to the outside are successively coated with two layers including an Ni plating film and an Au plating film (metal plating films (not shown)), each having a required thickness.

A Wiring substrate1such as that described above is generally formed as follows.

For example, four green sheets made of alumina powder are previously provided. After punching required portions of each green sheet, performing pattern printing with conductor paste containing W powder or the like thereon, and filling the through holes, these four green sheets are laminated upon each other and are contact-bonded to each other. Then, the laminated and contact-bonded green sheets are fired to a predetermined temperature zone to form a fired Wiring substrate1that is substantially the same as that shown inFIGS. 1 to 3.

Next, as shown by an alternate long and two short dash line inFIG. 3, a pointed end portion of an electrode pin Pi, which is L-shaped as a whole when viewed from a side, is inserted into the bottomed hole19from a front-surface-3side of the substrate body2, and is brought into point-contact with a surface of the portion18of the electroplating conductor layer16that is exposed at the bottom surface defining the bottomed hole19when a slight pressure is applied. Here, the portion18of the conductor layer16is a plating electrode surface.

In such a state, the Wiring substrate1is, along with the electrode pin Pi, successively immersed in an electrolytic Ni plating bath and an electrolytic Au plating bath (not shown), to successively perform electrolytic Ni plating and electrolytic Au plating. As a result, it is possible to successively coat a surface of the frame-shaped metalized layer15, which is a surface conductor portion that is not electrically connected to the different conductor layers11and the different conductor layers14, with an Ni plating film and an Au plating film.

A different electrode pin Pi is brought into contact with a surface of the element mounting pad10having a relatively wide area. The different electrode pin Pi is brought into contact with either of an end side of each element connection element11, which is a different conductor portion, and a surface of each external connection conductor14, which is a different conductor portion, to perform electrolytic metal plating, which is similar to that mentioned above, at the same time that the electrolytic metal plating mentioned above is performed.

As a result of performing these steps described above, a Wiring substrate1, such as that described above, can be provided.

According to the above-described Wiring substrate1, through the via conductor17, the frame-shaped metalized layer15, which is a surface conductor portion, is electrically connected to an end portion of the electroplating conductor layer16whose portion18is exposed at the bottomed hole (opening portion)19formed in the front surface3of the substrate body2. Therefore, the external connection terminals (different conductor portions)14occupy a wide region of the peripheral sides of the front surface3of the substrate body2, and the width and area of the frame-shaped metalized layer are small. Therefore, even if the electrode pin Pi, which is used for electroplating, does not easily directly contact the frame-shaped metalized layer15, the surface of the frame-shaped metalized layer15can be electrically conductive with the electroplating conductor layer16through the via conductor17. Therefore, by inserting the end portion of the electrode pin Pi, which is used for electroplating, from the opening portion of the bottomed hole19and bringing the end portion of the electrode pin Pi, which is used for electroplating, into contact with the portion (plating electrode surface)18of the electroplating conductor layer16that is exposed at the bottomed hole19, the surface of the frame-shaped metalized layer15is reliably covered with metal plating films, that is, an Ni plating film and an Au plating film. Therefore, the Wiring substrate1is one in which the surface of the frame-shaped metalized layer15, which is not electrically conductive with the different conductor portions11and14when in use, is reliably covered with metallic plating films.

Moreover, since the portion18of the electroplating conductor layer16is exposed at the bottomed hole19, it is less likely for the end portion of the electrode pin Pi that is inserted in the bottomed hole19to be shifted and dislodged from the bottomed hole19; and, even if scratches, such as indentations, are produced by the pin Pi, since such scratches are positioned in a bottom portion defining the bottomed hole19, these scratches are less likely to be conspicuous.

Further, since the electroplating conductor layer16is formed in the substrate body2and the portion18thereof is exposed at the bottom surface defining the bottomed hole19, it is possible to prevent unintentional short circuits from occurring, and to easily reduce the size of the entire Wiring substrate1including the substrate body2.

FIG. 4(A)is a partial plan view of the vicinity of a bottomed hole19rhaving a different form in the Wiring substrate1. As shown inFIG. 4(A), in plan view, in the vicinity of one corner of the front surface3of the substrate body2, the bottomed hole19rhas an elliptical shape having a long axis extending along a diagonal passing through a central portion of the front surface3; and the plating electrode surface (portion)18of the electroplating conductor layer16is elliptically exposed at a bottom surface defining the bottomed hole19r. The bottomed hole19rmay have an oblong shape in plan view. The long axis of the bottomed hole19rin the front surface3may extend along any direction.

FIG. 4(B)is a partial plan view of the vicinity of a bottomed hole19shaving still another form in the Wiring substrate1. As shown inFIG. 4(B), in plan view, in the vicinity of one corner of the front surface3of the substrate body2, the bottomed hole19shas a rectangular shape having a pair of long sides extending along a diagonal passing through the central portion of the front surface3, and the plating electrode surface (portion)18of the electroplating conductor layer16is exposed in a rectangular form at a bottom surface defining the bottomed hole19s. The bottomed hole19smay be square-shaped in plan view. Each long side and each side of the bottomed hole19sin the front surface3may extend along any direction.

Further,FIG. 5is a partial vertical sectional view of the vicinity of a bottomed hole19thaving still another form in the Wiring substrate1. As shown inFIG. 5, the bottomed hole19tis defined by an inclined inner wall surface (tapered surface) that gradually becomes narrower from the front-surface-3side of the substrate body2towards the plating electrode surface (portion)18of the electroplating conductor layer16that is positioned between the ceramic layer C3and the ceramic layer C4. Therefore, the bottomed hole19thas a conical shape when it is circular in plan view, has an elliptical conical shape or a long conical shape when it is elliptical or has an oblong shape in plan view, and has a the shape of a quadrangular prism when it is rectangular or square-shaped in plan view.

Even if any of the bottomed holes19rto19tis formed, similar advantages as those provided by the bottomed hole19can be provided. In particular, when the bottomed hole19tthat is defined by the inclined inner wall surface is used, as shown inFIG. 5, the end portion of the electrode pin Pi can be easily inserted into the bottomed hole19t.

FIG. 6is a partial vertical sectional view of the vicinity of the bottomed hole19that is applied in the Wiring substrate1. As shown inFIG. 6, a circular cylindrical wall surface conductor layer21whose bottom surface is connected to the plating electrode surface18of the electroplating conductor layer16, is further formed at an inner wall surface defining the bottomed hole19that is circular in plan view. According to the bottomed hole19that is provided with such a wall surface conductor layer21, even if the end portion of the electrode pin Pi is unintentionally dislodged from the plating electrode surface18, since the end portion of the electrode pin Pi point-contacts an inner peripheral surface of the wall surface conductor layer21, the electrode pin Pi and the electroplating conductor layer16can be electrically connected to each other.

An inner wall surface defining any of the bottomed holes19rto19tmay also be further provided with the wall surface conductor layer21.

The bottomed holes19rto19tin the Wiring substrate1may be formed in any location in the front surface3of the substrate body2. For example, any of the bottomed holes19rto19tmay be disposed between the external connection terminals14and14at the peripheral side(s) of the front surface3.

FIG. 7is a partial vertical sectional view of the vicinity of a bottomed hole19in a Wiring substrate1aaccording to another embodiment.

As shown inFIG. 7, the Wiring substrate1asimilarly includes, for example, a substrate body2, a cavity6, a frame-shaped metalized layer15, and a plurality of external connection terminals14(not shown), which are similar to those described above. In the Wiring substrate1a, the bottomed hole19, which is similar to that described above, is formed in the vicinity of one corner of or any peripheral side of a front surface3of the substrate body2; a wall surface conductor21, which is similar to that described above, is formed at an inner wall surface defining the bottomed hole19; and a plating electrode surface18of an electroplating conductor layer16is exposed at a bottom surface defining the bottomed hole19and the wall surface conductor layer21. A top surface of the wall surface conductor layer21and the frame-shaped metalized layer15formed along an open portion of the cavity6are electrically connected to each other by a connection wiring22formed along the front surface3of the substrate body2. The connection wiring22is disposed within a relatively small width so as to extend between the external connection terminals14and14.

The Wiring substrate1adescribed above is one that, in addition to the advantages provided by the Wiring substrate1, provides the advantage of making it possible to, by forming the connection wiring22on any location of the front surface3of the substrate body2, such as any location between external connection conductors14and14that are different conductor portions, minimizing the volume (region) of the inside of the substrate body2that is occupied, and reliably cover a surface of the frame-shaped metalized layer15, which is a surface conductor portion, with required metal plating films.

In place of the bottomed hole19, any of the bottomed holes19rto19swhere the wall surface conductor layer21is formed at its inner wall surface may be applied.

Even a surface conductor portion (not shown) formed on the back surface4of the substrate body2can be electrically conductive with the plating electrode surface18of the electroplating conductor layer16through the bottomed hole19that opens at the back surface4, the wall surface conductor layer21formed at the inner wall surface defining the bottomed hole19, and the connection wiring22formed along the back surface4so as to be interposed therebetween.

FIG. 8is a partial plan view of the vicinity of the bottomed hole19in a Wiring substrate1baccording to another embodiment.FIG. 9is a partial vertical sectional view as seen in the direction of arrow Z inFIG. 8.

As shown inFIGS. 8 and 9, the Wiring substrate1bincludes, for example, a substrate body2, a cavity6, a frame-shaped metalized layer15, and a plurality of external connection conductors14, which are similar to those described above. In the Wiring substrate1b, of a plurality of element connection terminals11formed on a surface of a stepped portion8in the cavity6, at least one thereof when in use is not electrically connected to the different conductor portions11and14and a terminal formed on a mother board (not shown), that is, is formed as an electrically independent dummy element connection terminal (surface conductor portion)11a.

As shown inFIGS. 8 and 9, the bottomed hole19, which is similar to that described above, is formed in the vicinity of the upper right corner of a front surface3of the substrate body2; and a plating electrode surface18of the electroplating conductor layer16formed along a portion between a ceramic layer C3and a ceramic layer C4is exposed at a bottom surface defining the bottomed hole19. Even such an electroplating conductor layer16is electrically independent of the different conductor portions11and14, and is separated from side surfaces5of the substrate body2.

Further, a base end side of the element connection terminal11ais connected to one end side of a connection wiring24formed between a ceramic layer C2and the ceramic layer C3. The other end side of the connection wiring24is electrically connected to the electroplating conductor layer16through a via conductor25extending through the ceramic layer C3.

Therefore, as shown inFIG. 9, by bringing an end portion of an electrode pin Pi, which is similar to that described above, into contact with the plating electrode surface (portion)18in the bottomed hole19, and by performing electrolytic Ni plating and electrolytic Au plating, which are similar to those mentioned above, it is possible to reliably cover a surface (exposed surface) of the electrically independent element connection terminal11awith an Ni plating film and an Au plating film. Consequently, it is possible for the Wiring substrate1bto be one in which even the surface of the element connection terminal11ahaving a relatively small area is covered with predetermined metal plating films.

FIG. 10is a partial vertical sectional view that illustrates a different form of the Wiring substrate1b.

As shown inFIG. 10, the Wiring substrate1bincludes, for example, a substrate body2, a cavity6, a frame-shaped metalized layer15, and a plurality of external connection conductors14(not shown), which are similar to those described above. An element connection terminal11a, which is at least one surface conductor portion, is formed on a surface of a stepped portion8in the cavity6. As shown inFIG. 10, a bottomed hole19that opens at a back surface4of the substrate body2is formed in any position at a peripheral side of the back surface4so as to extend through a relatively thick ceramic layer C1. A plating electrode surface18of an electroplating conductor layer16formed between the ceramic layer C1and a ceramic layer C2is exposed at a bottom surface defining the bottomed hole19. Even such an electroplating conductor layer16is electrically independent of different conductor portions11and the different conductor portions14, and is separated from side surfaces5of the substrate body2.

Further, when in use, a base end side of the electrically independent element connection terminal11ais connected to one end side of a connection wiring24formed between the ceramic layer C2and a ceramic layer C3, and the other end side of the connection wiring24is electrically connected to the electroplating conductor layer16through a via conductor25extending through the ceramic layer C2.

Therefore, as shown inFIG. 10, by bringing an end portion of an electrode pin Pi, which is similar to that described above, into contact with the plating electrode surface (portion)18in the bottomed hole19from a back-surface-4side of the substrate body2, and by performing electrolytic Ni plating and electrolytic Au plating, which are similar to those mentioned above, it is possible reliably cover a surface (exposed surface) of the electrically independent element connection terminal11awith an Ni plating film and an Au plating film.

FIG. 11is a partial vertical sectional view that is similar to that above and that illustrates a Wiring substrate1bthat is applied as shown inFIG. 10.

In the Wiring substrate1b, a relatively thick ceramic layer C1, which is the lowest layer of a substrate body2, is divided into an upper ceramic layer C11and a lower ceramic layer C12, a bottomed hole19that opens at a back surface4of the substrate body2is formed, and a plating electrode surface18of an electroplating conductor layer16, which is formed between the ceramic layer C11and the ceramic layer C12and which is similar to those described above, is exposed at a bottom surface defining the bottomed hole19.

Further, a base end side of the element connection terminal11a, which is a surface conductor portion, is connected to one end side of a connection wiring24formed between a ceramic layer C2and a ceramic layer C3; the other end side of the connection wiring24is connected to one end side of a connection wiring26through a via conductor25extending through the ceramic layer C2, the connection wiring26being formed between the ceramic layer C12and the ceramic layer C2; and the other end side of the connection wiring26is electrically connected to the electroplating conductor layer16through a via conductor25extending through the ceramic layer C12.

As described above, by causing the element connection terminal11a, which is a surface conductor portion, and the electroplating conductor layer16to be electrically conductive with each other through the two layers, that is, the upper connection wiring24and the lower connection wiring26, and two via conductors25, that is, the upper and lower via conductors25, the bottomed hole19having a relatively small inside diameter easily opens at the back surface4of the substrate body2.

Even the Wiring substrate1bhaving such a form described above becomes one in which a surface of the element connection terminal11ahaving a relatively small area is covered with predetermined metal plating films.

In the forms of the Wiring substrates1bshown inFIGS. 9 to 11, in place of the bottomed hole19, any one of the bottomed holes19rto19smay be formed. The wall surface conductor layer21may be formed on the inner wall surface of any one of such bottomed holes19and19rto19s.

In each of the forms of the Wiring substrates1bshown inFIGS. 8 to 11, it is possible to form, in place of the single element mounting pad10, a plurality of element mounting pads on the bottom surface7defining the cavity6; form a portion of each element mounting pad as an electrically independent surface conductor portion when in use; and cover surfaces of the element mounting pads, which are the surface conductor portions, with predetermined metal plating films by any of the ways shown inFIGS. 8 to 11.

The present invention is not limited to the embodiments and forms described above.

For example, the front surface of the substrate body may be a flat surface, or a cavity, which is similar to that described above, may open in a reverse direction in the back surface of the substrate body.

The surface conductor portion according to the present invention also refers to a portion of an external connection conductor formed at any location on the front surface or the back surface of the ceramic substrate body. For example, the external connection terminals refer to, in addition to a plurality of external connection conductors that are different conductor portions, those that form portions of a certain pattern to be subjected to image recognition on the front surface or the back surface in plan view; and positioning alignment marks on the front surface or the back surface of the substrate body in plan view.

Further, it is possible to form a plurality of the bottomed holes, which are opening portions according to the present invention, in the front surface or the back surface of the same Wiring substrate, and individually expose portions of the electroplating conductor layer at the bottom surfaces defining the respective bottomed holes.

In addition, the bottomed hole may have a small opening diameter at the front surface or the back surface of the substrate body, and may have a wide bottom in cross section in which the diameter of a bottom-surface side is larger than the opening diameter.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to reliably provide a Wiring substrate in which, even if, for example, the front surface of the ceramic substrate body is provided with an electrically independent surface conductor portion, or even if the bottom-surface side of the cavity that opens at the front surface of the substrate body is provided with an electrically independent surface conductor portion, a surface of each of these surface conductor portions is reliably covered with metal plating films; scratches on these surfaces caused by contact with an electrode pin are less likely to be conspicuous; and the substrate body can be reduced in size.

REFERENCE SIGNS LIST