JP5409236B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring board in which a groove is formed on a side surface of an insulating substrate having an electronic component mounting portion on a main surface, and a conductor layer is attached to the groove, and in particular, a conductor through a conductive connecting material. The present invention relates to a wiring board having high connection reliability to an external electric circuit of a layer.

  Conventionally, as a general wiring board used for mounting electronic components such as semiconductor elements and crystal resonators, an electronic component mounting portion is provided on the main surface (usually the upper surface) of an insulating base such as a rectangular parallelepiped. In the vicinity of the mounting portion, a connection pad to which the mounted electronic component is electrically connected is formed.

  Various configurations are employed for electrical connection from the connection pad to the external electric circuit. However, in a wiring board that has been downsized in recent years, a groove (so-called castellation) is formed vertically on the side surface of the insulating base. A structure is adopted in which a conductor layer for external connection is attached to the surface (inner surface) of the groove and connected to an external electric circuit via the conductor layer.

  The conductor layer deposited in the groove is electrically connected to the connection pad via, for example, a wiring conductor formed inside the insulating base. Then, the electronic component is mounted on the mounting portion of the main surface of the insulating base, the electrode is electrically connected to the connection pad, and the conductive layer on the side surface is connected to the external electric circuit via a conductive connecting material such as solder. Thus, the electrode of the electronic component and the external electric circuit are electrically connected.

JP 2003-152298 A Japanese Utility Model Publication No. 1-70293

  However, with the recent demand for miniaturization of wiring boards, the size of the groove on the side surface for electrical connection has been reduced and the height has been reduced, and the conductor layer attached to the groove and the external electrical circuit have been reduced. There is a problem that it is difficult to increase the connection reliability with the circuit.

  In particular, in electronic devices for portable use typified by mobile phones in recent years, problems such as disconnection of the conductor layer attached to the groove of the wiring board and the external electric circuit due to a large impact when dropped are generated. It is becoming easier to do this, and it is important to improve connection reliability.

  The present invention has been devised in view of the problems in the prior art, and the object thereof is to provide a conductor layer and external electrical power deposited in a groove (castellation) formed in the vertical direction on the side surface of the insulating base. An object of the present invention is to provide a wiring board that can be mounted with good and reliable connection to a circuit.

The wiring board of the present invention has an electronic component mounting portion on the main surface and an insulating base having a groove extending in the vertical direction on the outer surface, and the electronic component formed on the mounting portion is electrically connected. A wiring comprising a connection pad and a conductor layer attached to the inner surface of the groove and electrically connected to the connection pad, the conductor layer being connected to an external electric circuit via a conductive connection material The substrate has a recess formed in the groove across the width direction of the groove, and the conductor layer is deposited along the recess so that a part of the surface of the conductor layer is recessed. And
The depth of the groove is gradually deeper from the upper end and the lower end of the groove toward the center in the vertical direction, and the concave portion of the groove is formed according to the difference in depth. To do.

  According to the wiring board of the present invention, the recess extending across the widthwise direction of the groove is formed in the vertically extending groove of the insulating base on the outer surface, and the conductor layer is covered along the recess. Since a part of the surface of the conductor layer is concave and attached, for example, when the socket is mounted, the surface is attached along the concave part extending across both ends in the width direction of the groove, and the surface is concave. When the spring terminal as the conductive connecting material of the socket is fitted to the conductor layer of the part, the conductor layer can be firmly joined and securely connected. In addition, when a conductor layer having a concave surface is joined to an external electric circuit board as a conductive connecting material via solder, the solder is formed along the concave surface of the conductor layer. By spreading wet, the bonding area between the conductor layer and the solder in the concave portion is increased, so that the conductor layer can be firmly bonded and securely connected.

  Further, according to the wiring board of the present invention, the depth of the groove gradually becomes deeper from the upper end and the lower end of the groove toward the central portion in the vertical direction, and the concave portion of the groove is formed according to the difference in depth. For example, when a conductor layer whose surface is partially concaved by the concave portion is joined to the external electric circuit board as a conductive connecting material via solder, the depth of the groove is Since the depth gradually increases from the upper end and the lower end toward the central portion in the vertical direction, the bonding area between the concave portion of the conductor layer in which a part of the surface is concave and the solder increases, and an appropriate Because of the amount of solder, the solder meniscus angle is always smaller at the point where the solder spreads along the concave conductor layer, so that the stress applied to the conductor layer is dispersed by soldering. Will be dropped Etc. can also be less likely to fracture at the solder joint portion if a shock is applied by, it is possible to connect high reliability wiring board to an external electrical circuit.

(A) is a top view showing a reference example of the embodiment of the wiring substrate, (b) is a well bottom view, along line A-A 'shown in (c) (a) and (b) It is sectional drawing. (A) is an enlarged view of a portion B shown in a circle in FIG. 1 (c), and (b) is a cross-sectional view of an example in which the portion is socket-mounted. (A) is an enlarged view similar to FIG. 2 (a), showing an example of the embodiment of the wiring board of the present invention, and (b) is a cross-sectional view of an example in which the portion is solder-mounted. (A) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), a cross-sectional view of (b) the example soldered portions thereof. (A) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), a cross-sectional view of (b) the example socket implement portion thereof. (A) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), a cross-sectional view of (b) the example socket implement portion thereof.

  An example of an embodiment of a wiring board according to the present invention will be described with reference to the accompanying drawings.

Figure 1 (a) ~ (c) are those showing a reference example of the embodiment of the wiring substrate, respectively therewith, (a) shows the top view, (b) is a bottom view, (c) it is (a) It is sectional drawing in the AA 'line shown to (b). In these drawings, 1 is an insulating substrate, 2 is a mounting portion for the electronic component 6, 3 is a connection pad formed on the mounting portion 2, 3 'is a mounting connection pad formed on the outer periphery of the lower surface of the insulating substrate 1, 4 is a groove (castellation), 4a is a recess, 5 is a conductor layer, 6 is an electronic component, 7 is a metal layer, 8 is a bonding wire, and 10 is a wiring board.

  The insulating base 1, the mounting part 2 of the electronic component 6, the connection pad 3 formed on the mounting part 2, the groove 4 formed on the outer surface of the insulating base 1 so as to extend in the vertical direction, and the groove 4 in the width direction A wiring substrate 10 for mounting the electronic component 6 is formed by the recess 4a formed over both ends and the conductor layer 5 deposited on the inner surface of the groove 4.

  The insulating substrate 1 is made of an electrically insulating material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body. The main surface, on the upper surface in the example shown in FIG. The electronic component 6 is provided with a mounting portion 2 on which the electronic component 6 is mounted.

  If the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, a suitable organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to form a mud-like shape. A ceramic slurry is prepared, and then the ceramic slurry is formed into a sheet shape by a sheet forming technique such as a doctor blade method or a calender roll method to obtain a ceramic green sheet (ceramic green sheet) having a predetermined shape. A plurality of ceramic green sheets are laminated and fired at a temperature of about 1600 ° C. in a reducing atmosphere.

  In addition, a connection pad 3 to which the electronic component 6 is electrically connected is formed on the mounting portion 2 on which the electronic component 6 on the upper surface (main surface) is mounted. A plurality of conductor layers 5 are formed on the lower surface of the insulating substrate 1 through the grooves 4 formed on the outer surface through the inside of the substrate 1. The conductor layer 5 functions as a conductive path for connecting each signal or ground electrode of the electronic component 6 connected to the connection pad 3 to the mounting connection pad 3 ′, and one end on the mounting portion 2 side is connected. Connected to the pad 3, the signal or ground electrodes of the electronic component 6 are electrically connected to the connection pad 3 via bonding wires 8.

  The conductor layer 5 is made of a sintered metal powder such as tungsten, molybdenum, manganese, copper, silver, gold or palladium, and is obtained by adding and mixing an appropriate organic binder and solvent to the metal powder such as tungsten. The conductor paste is printed and applied in a predetermined pattern to a predetermined portion of the ceramic green sheet to be the insulating base 1 in advance by a well-known screen printing method, so that it is removed from the upper surface of the insulating base 1 through the inside of the insulating base 1. It is deposited from the side to the bottom.

  A frame-shaped metal layer 7 is attached to the upper surface of the insulating substrate 1 so as to surround the mounting portion 2 on which the electronic component 6 is mounted. This frame-shaped metal layer 7 functions as a base metal layer when a metal lid (not shown) to be described later is attached to the insulating base 1, and is made of tungsten, molybdenum, manganese, copper, silver, It is formed by sintering metal powder such as gold or palladium.

  A metal lid is brazed to the frame-shaped metal layer 7 via a brazing material, so that the electronic component 6 mounted on the mounting portion 2 of the insulating base 1 is hermetically sealed from the external environment such as the atmosphere. It will be stopped.

  The frame-shaped metal layer 7 is formed on the outer peripheral portion of the upper surface of the insulating base 1 so as to surround the mounting portion 2 of the electronic component 6 by the same method as that for the conductor layer 5 described above.

  Furthermore, a plurality of mounting connection pads 3 ′ that are electrically connected to the connection pads 3 are formed on the outer periphery of the lower surface of the insulating substrate 1. The mounting connection pad 3 'is connected to the wiring conductor of the external electric circuit board together with the conductor layer 5 through a lead-free solder, for example, as a conductive connection material (not shown), for signal or grounding of the electronic component 6 These electrodes are electrically connected to an external electric circuit through the connection pad 3 and the conductor layer 5.

  The connection pad 3 and the mounting connection pad 3 ′ are made of sintered metal powder such as tungsten, molybdenum, manganese, copper, silver, gold, or palladium, and are respectively formed in the same manner as the conductor layer 5 described above. The insulating base 1 is formed in a predetermined shape on the mounting portion 6 on the upper surface and the outer peripheral portion on the lower surface.

  Furthermore, a plurality of grooves 4 extending in the vertical direction are attached to the outer surface of the insulating substrate 1, and a conductor layer 5 is formed on the inner surface of the grooves 4.

  The groove 4 is formed by forming a circular or semi-circular through hole in the ceramic green sheet to be the insulating substrate 1 by a punching method or a laser processing method, and then suitable for metal powder such as tungsten on the inner surface in the portion to be the groove 4. A conductor paste obtained by adding and mixing an organic binder and a solvent is preliminarily printed and applied while being sucked by a screen printing method or the like, whereby the conductor layer 5 is formed into a predetermined shape on the inner surface of the groove 4 on the outer surface of the insulating substrate 1. Then, by stacking a plurality of these ceramic green sheets, the ceramic green sheet is formed in a through-hole extending in the vertical direction to be a groove 4 formed on the outer surface of the insulating substrate 1. Next, the insulating substrate 1 is cut along a dividing line passing through the through hole by a slicing method, a laser processing method, or the like, so that a groove 4 extending in the vertical direction is formed on the outer surface of the insulating substrate 1. It should be noted that the cutting along the dividing line passing through the through-hole serving as the groove 4 may be performed before or after the insulating substrate 1 is fired.

  Here, when the through holes are formed in the ceramic green sheet to be the insulating base 1 by a punching method or a laser processing method, the size of the through holes formed in a part of the ceramic green sheets located in the middle of the stacking direction is set. When a through-hole extending in the vertical direction to be a groove 4 is formed by stacking a plurality of ceramic green sheets by changing (enlarging), insulation as shown in FIGS. 2 (a) and 2 (b) A groove 4 extending in the vertical direction can be formed on the outer surface of the substrate 1, and a recess 4 a extending across both ends in the width direction can be formed in the middle of the groove 4. Then, by applying the conductor layer 5 along the grooves 4 and the recesses 4a, a part of the surface of the conductor layer 5 can be made concave according to the recesses 4a. 2A is an enlarged view of a portion B shown in a circle in FIG. 1C, and FIG. 2B is a cross-sectional view of an example in which that portion is socket-mounted. Here, since the conductor layer 5 is formed in the shape of the groove 4 and the recess 4a, the conductor layer 5 is not shown.

In addition, when forming the through hole to be the groove 4, a plurality of ceramic green sheets with the through hole size gradually changed for each layer are stacked, and the upper and lower sides that become castellations on the outer surface of the insulating substrate 1 are stacked. When the groove 4 extending in the direction is formed, as shown in FIGS. 3A and 3B, the depth of the groove 4 gradually increases from the upper end and the lower end of the groove 4 toward the central portion in the vertical direction. The recess 4a can be formed at the center of the groove 4 in accordance with the difference in depth of the groove 4. FIG. 3 (a) is an enlarged view similar to FIG. 2 (a), showing an example of the embodiment of the wiring board of the present invention, and FIG. 3 (b) is a sectional view of an example in which the portion is solder mounted. .

  Note that the recess 4a is formed in the central portion of the groove 4 in accordance with the difference in the depth of the groove 4 because the shape of the groove 4 and the recess 4a as shown in FIGS. 3 (a) and 3 (b). This means a state where the shapes match.

  At this time, when the through hole is formed in the ceramic green sheet by a punching method, the shape of the pin of the punching die is a trapezoidal shape or a cylindrical shape, and the size is changed by the layer of the ceramic green sheet. It is possible to form the concave portion 4 a having a beautiful curved shape whose cross section corresponds to the depth of the groove 4.

  It should be noted that the connection pad 3, the mounting connection pad 3 ', the conductor layer 5 and the frame-like metal layer 7 have an exposed surface with corrosion resistance such as nickel or gold, bonding property of the bonding wire 8, and solder wettability. If a plating layer made of a metal having good properties is applied, it is possible to effectively prevent oxidative corrosion of the connection pad 3, the mounting connection pad 3 ', the conductor layer 5, the frame-like metal layer 7, and the like. In addition, the attachment of a metal lid (not shown) to the frame-shaped metal layer 7 and the connection of the mounting connection pad 3 ′ to the external electric circuit board can be made reliable and strong.

  Therefore, the connection pad 3, the mounting connection pad 3 ', the conductor layer 5 and the frame-like metal layer 7 have good corrosion resistance such as nickel or gold, bonding property and solder wettability on the exposed surface. It is preferable to deposit a suitable metal by a plating method. In particular, for example, it is preferable to sequentially deposit a nickel plating layer having a thickness of 1 μm to 10 μm and a gold plating layer having a thickness of 0.05 μm to 3 μm.

  In this case, the thickness of the gold plating layer may be different depending on the portion to be deposited, the crystal orientation of the gold plating layer, and the like. For example, the crystal orientation in the X-ray diffraction of the gold plating layer is made as uniform as possible to the (111) plane, and the thickness is set to about 0.3 μm to 1 μm throughout the region including the region where the bonding wire 8 is connected. Alternatively, the thickness of only the soldering region may be as thin as about 0.3 μm or less, and the generation of brittle intermetallic compounds of tin-gold may be suppressed to further increase the reliability of soldering. .

  Thus, according to the wiring board 10 of the present invention, the electronic component 6 is mounted on the mounting portion 2 provided on the main surface (upper surface) of the insulating base 1, and the signal and ground electrodes of the electronic component 6 are connected to the connection pad 3. Then, a metal lid made of iron-nickel-cobalt alloy, iron-nickel alloy or the like is attached to the frame-like metal layer 7 on the outer peripheral portion of the upper surface of the insulating base 1. And the electronic component 6 is hermetically sealed to the mounting portion 2 with a metal lid, thereby completing an electronic device as a product (a semiconductor device when the electronic component 6 is a semiconductor element).

  In this electronic device, the mounting connection pad 3 ′ on the outer periphery of the lower surface of the insulating base 1 is joined via a spring terminal of a socket mounted on the surface of the wiring conductor of the external electric circuit board, or an external electric circuit. It is mounted on the external electric circuit board by bonding to the wiring conductor of the board via solder, and at the same time, the signal and ground electrodes of the electronic component 6 are connected to the connection pad 3, the conductor layer 5, and the mounting connection pad 3 '. Is electrically connected to the wiring conductor of the external electric circuit board.

  Alternatively, as shown in FIG. 2 (b), the electronic device uses a conductor layer 5 deposited on the inner surface of the groove 4 on the outer surface of the insulating base 1 as a wiring conductor of an external electric circuit board. The electrodes for signal and ground of the electronic component 6 are electrically connected to the wiring conductor of the external electric circuit board by being joined via the spring terminal 12 as the conductive connecting material of the socket 11 mounted on the circuit board. May be connected to each other.

In the wiring board 10 of the present invention, the groove 4 is formed with a recess 4a extending across both ends of the groove 4 in the width direction, and the conductor layer 5 is deposited along the recess 4a. It is important that a part of the surface of 5 is concave.

  According to the wiring board 10 of the present invention, the groove 4 is thus formed with the recesses 4a extending across both ends in the width direction, and the conductor layer 5 is deposited along the recesses 4a. Since a part is concave, it is assumed that the mounting connection pad 3 ′ and the conductor layer 5 on the outer periphery of the lower surface of the insulating base 1 are joined to the wiring conductor of the external electric circuit using solder as a conductive connecting material. However, when the solder wets and spreads on the conductor layer 5 attached to the groove 4, the groove 4 has a small diameter and a small depth by entering the recess 4 a across the both ends in the width direction of the groove 4. Even so, a large contact area between the solder and the conductor layer 5 can be obtained. As a result, a sufficient amount of solder can be interposed between the conductor layer 5 whose surface is partly concave and the wiring conductor of the external electric circuit board, and the wiring board 10 constituting the electronic device is externally connected. It can be bonded very firmly while being electrically connected to the electric circuit board.

  In addition, as a conductive connecting material for the socket 11 mounted on the external electric circuit board, the wiring conductor of the external electric circuit board is connected to the conductor layer 5 attached to the groove 4 on the outer surface of the insulating substrate 1. When joining via the spring terminal 12, the groove | channel 4 is formed with the recessed part 4a over the both ends of the width direction, and the conductor layer 5 is adhere | attached along this recessed part 4a, The surface of the conductor layer 5 Since a part of the concave portion 4 has a concave shape corresponding to the concave portion 4, the spring terminal 12 of the socket 11 is fitted into the concave portion 4 a and becomes a concave shape of the conductor layer 5 as in the example shown in FIG. By reliably contacting the existing portion, even if the groove 4 has a small diameter and a small depth, it is possible to make an electrical connection and a strong connection.

Further, in the wiring board 10 of the present invention, as for the groove 4, as shown in the example shown in FIG. 3, the depth of the groove 4 gradually increases from the upper end and the lower end of the groove 4 toward the center in the vertical direction. and it has a recess 4a of the groove 4 that is formed in accordance with the difference in depth.

  Here, in the case where the groove 4 is formed so as to become the groove 4 that becomes gradually deeper from the upper end and the lower end toward the central portion in the vertical direction, each ceramic that becomes an insulating layer constituting the insulating base 1. The size of the through hole formed in the green sheet is, for example, a circle or ellipse having a diameter of 0.8 mm to 1 mm, and the size of the through hole formed in the ceramic green sheet serving as the insulating layer to be the recess 4a is other than the recess 4a. It is desirable that the diameter of the through hole formed in the ceramic green sheet to be the groove 4 is larger by 10 μm to 100 μm. If the size of the diameter of the through-hole of the part to be the recess 4a is less than 10 μm with respect to the diameter of the other part, the recess 4a becomes shallow, so that the bondability when solder mounting or socket mounting is improved. The effect is thin. On the other hand, when the thickness exceeds 100 μm, when the groove 4 extending in the vertical direction is formed on the outer surface of the insulating substrate 1 to be the groove 4 by stacking the ceramic green sheets, the step between the groove 4 and the recess 4a is large. The conductor layer 5 may be disconnected at the time of manufacture, and the yield may be reduced.

The number of the recesses 4a is formed in the groove 4, in the example shown in FIGS. 1 to 3 is one place either, in the case of forming a concave portion 4a of the plurality of locations in one groove 4, constituting the insulating substrate 1 By changing the size of the through hole of each layer formed in each ceramic green sheet to be an insulating layer, a continuous recess 4a may be provided as in the example shown in FIGS. 4 (a) and (b), Further, the number of the recesses 4a may be increased by narrowing the width (shortening the length in the vertical direction). By increasing the number of the recesses 4a in this way, the contact area between the solder and the conductor layer 5 when joined using solder can be further increased. As a result, a sufficient amount of solder can be interposed between the conductor layer 5 whose surface is partly concave and the wiring conductor of the external electric circuit board, and the wiring board 10 constituting the electronic device is externally connected. It can be bonded very firmly while being electrically connected to the electric circuit board. Incidentally, FIG. 4 (a) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), the is a cross-sectional view of the example in which soldered to (b) the portion thereof .

Further, as in the example shown in FIGS. 5A and 5B, when the concave portion 4a continuous from below is formed in a state of being biased to the lower side of the groove 4, the concave portion 4a can be provided deeper. Therefore, the contact area between the conductor layer 5 in the groove 4 and the spring terminal 12 is increased when the socket 11 mounted on the external electric circuit board is joined via the spring terminal 12 as a conductive connecting material. As a result, the connection reliability becomes higher. Further, the combination of the shape of the spring terminal 12 and the shape of the recess 4a in the groove 4 makes it possible to have stronger connection reliability in the drop test. Incidentally, FIG. 5 (a) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), the is a cross-sectional view of (b) the example socket implement portion thereof .

  Further, it is desirable that the vertical length of the recess 4a in the groove 4, that is, the width of the recess 4a is at least 10 μm. When the width of the recess 4a is less than 10 μm, the effect of improving the bonding property by the recess 4a when the wiring board 10 having the groove 4 in which the recess 4a is formed is mounted by soldering or socket mounting becomes thin. On the other hand, while the length of the groove 4 in the vertical direction is, for example, 200 μm, the width of the recess 4a may be the same size as 200 μm as in the example shown in FIG. Therefore, the width of the recess 4a is 5% to 100% of the length of the groove 4, and the specific size is 10 μm while the length of the groove 4 is 200 μm to 800 μm. It is preferable to set it to -800 micrometers.

  The depth of the recess 4a in the groove 4 is 10% to 100% with respect to the depth of the groove 4, and the specific depth is that the depth of the groove 4 is 100 μm to 500 μm. The depth of the recess 4a including the depth of the groove 4 is preferably 110 μm to 1000 μm (the depth of the recess 4a from the groove 4 is 10 μm to 500 μm). The cross-sectional shape of the concave portion 4a is not limited to a flat bottom surface such as a square shape, but may be a curved or bent shape such that the bottom surface is deepest in the central portion, such as a semicircular shape. . The depth of the recess 4a is set so that the depth of the deepest portion falls within the above range when the cross-sectional shape of the recess 4 is deepest at the center, such as a semicircular shape. do it.

  Further, as in the example shown in FIG. 3A, the depth of the groove 4 gradually becomes deeper from the upper end and lower end of the groove 4 toward the central portion in the vertical direction, and according to the difference in depth. When the concave portion 4a of the groove 4 is formed, when the mounting connection pad 3 ′ on the outer peripheral portion of the lower surface of the insulating substrate 1 and the wiring conductor of the external electric circuit board are joined using solder, the solder is not grooved. When the conductor layer 5 deposited on the substrate 4 is wetted and spread, a large contact area between the solder and the conductor layer 5 can be obtained, so that the two can be more firmly bonded. Also, the solder wets and spreads along the recess 4a of the groove 4, and the meniscus 13 is formed in the solder in the same shape as the recess 4a of the groove 4 as shown in FIG. Since the stress applied to the layer 5 and the stress generated in the solder are dispersed throughout the recess 4a of the groove 4, the wiring is more reliable even when used in electronic devices that require impact resistance such as portable use. The substrate 10 can be obtained.

  Here, as in the example shown in FIG. 3A, the depth of the groove 4 gradually becomes deeper from the upper end and the lower end of the groove 4 toward the central portion in the vertical direction, and according to the difference in depth. When the recess 4a of the groove 4 is formed, the depth of the recess 4a is preferably 10% to 50% with respect to the difference in the depth of the groove 4. If the depth of the recess 4a is less than 10% with respect to the difference in depth of the groove 4, the recess 4a becomes shallow, so that the effect of improving the bondability when mounted by solder or socket is thin. Become. On the other hand, when it exceeds 50%, when the grooves 4 extending in the vertical direction are formed on the outer surface of the insulating base 1, the entrance portions located at the upper and lower ends of the grooves 4 are circled in FIG. In the location indicated by C, chipping may occur at the portion where the insulating base 1 is the thinnest, and there is a possibility that the bonding reliability may be lowered. Specifically, the depth difference of the groove 4 is 100 μm to 500 μm, whereas the depth of the recess 4a including the depth of the groove 4 is 110 μm to 750 μm (the depth of the recess 4a from the groove 4). 10 μm to 250 μm).

  Examples of the wiring board of the present invention will be described below.

( Reference example )
First, an acrylic resin is used as an organic binder with respect to 100% by weight of ceramic powder prepared by mixing 96% by weight of aluminum oxide and 4% by weight of silicon oxide, magnesium oxide and calcium oxide as a sintering aid. Further, 9% by mass in solid content and 0.1% by mass of dibutyl phthalate as a plasticizer were added, and toluene was used as a solvent and mixed for 40 hours by a ball mill to prepare a ceramic slurry. This ceramic slurry is formed into a sheet by the doctor blade method and becomes an insulating substrate 1 after firing. The thickness is 0.2 mm.
A ceramic green sheet was prepared.

  Next, with respect to the first ceramic green sheet, a through hole is not formed at a predetermined position where the groove 4 is formed, and a cross-sectional shape is formed at a position where the electronic component 6 is mounted. A rectangular through hole was formed by punching.

  Next, on the second ceramic green sheet, a through hole having a diameter of 300 μm that finally becomes the groove 4 was formed by punching at a predetermined position where the groove 4 was formed. Further, in addition to this through hole, a rectangular through hole similar to the above was formed by punching at a position to be the mounting portion 2 on which the electronic component 6 is mounted.

  Next, with respect to the through-hole which becomes the groove 4 of the ceramic green sheet, the cellulose nitrate is used in an amount of 0.8% by mass with 100% by mass of tungsten (W) powder having an average particle size of 1.90 μm as an organic binder. In addition to the addition, conductive paste obtained by adding and mixing diethylene glycol monobutyl ether acetate and dibutyl phthalate as solvents for viscosity adjustment, by screen printing method, sucking from the lower surface side of the ceramic green sheet, around the opening of the through hole And the conductor paste layer used as the conductor layer 5 after baking was formed by printing on the inner wall surface of the through hole.

  Next, with respect to the third ceramic green sheet serving as the bottom surface of the mounting portion 2, a through hole having a diameter of 400 μm that finally becomes the groove 4 is formed by punching at a predetermined position where the groove 4 is formed. The conductor paste was printed and applied to the periphery of the through hole and the inner wall surface of the through hole while being sucked from the lower surface side by screen printing, to form a conductor paste layer that becomes the conductor layer 4 after firing. Also, using the same conductive paste, a conductive paste layer is printed and applied in a pattern to be a connection pad 3 on a portion to be the mounting portion 2 on the upper surface, and a conductive layer 5 is printed and applied to a through hole to be a groove 4 Connected to the paste layer.

  Next, in the fourth ceramic green sheet, a through hole having a diameter of 300 μm that finally becomes the groove 4 is formed by punching at a predetermined position where the groove 4 is formed, and using the above-described conductor paste, While being sucked from the lower surface side by screen printing, printing was applied to the periphery of the opening of the through hole and the inner wall surface of the through hole to form a conductor paste layer to be the conductor layer 5 after firing. In addition, a conductor paste layer is printed and applied to a pattern that becomes a mounting connection pad 3 ′ after firing by screen printing using the above-described conductor paste at a position that becomes an outer peripheral portion of the lower surface of the ceramic green sheet, It was made to connect with the conductor paste layer used as the conductor layer 5 apply | coated to the through-hole which becomes this.

  The first ceramic green sheet is sintered by screen printing using the above-described conductor paste on the outer peripheral portion of the upper surface of the frame-shaped portion surrounding the through-hole serving as the mounting portion 2. A frame-shaped conductor paste layer that later becomes the frame-shaped metal layer 7 was formed.

  Then, these four ceramic green sheets are laminated and pressure-bonded to form a laminate, and after removing organic components by heating at a temperature of about 1000 ° C. for about 3 hours in a nitrogen atmosphere containing water vapor, Firing was performed in a nitrogen atmosphere containing about 6 hours at a temperature of about 1500 ° C.

  Further, after firing, the connection pad 3 formed on the mounting portion 2, the mounting connection pad 3 ′ formed on the outer periphery of the lower surface, the frame-shaped metal layer 7 formed on the outer periphery of the upper surface, and the outer surface of the insulating substrate 1. A nickel plating layer having a thickness of 3 μm is applied by electroplating to the conductor layer 4 on the inner surface of the groove 4 extending in the vertical direction, and the thickness is formed by electroplating on the nickel plating layer. Were sequentially deposited with a 0.5 μm gold plating layer.

Furthermore, the slicing method, by cutting the insulating base 1 along a parting line passing through the center of the through hole as a groove 4, to prepare a reference example of wiring substrate 10, such as in the example shown in FIG. In this reference example , the vertically extending groove 4 formed on the outer surface of the insulating substrate 1 has a vertical length of 400 μm, a cross-sectional shape of a semicircle, and a basic width of 200 μm. Depth is 100μm
Met. The recess 4a formed at the center of the groove 4 and extending at both ends in the width direction of the groove 4 has a width (length in the vertical direction) of 250 μm and a depth including the depth of the groove 4 of 120 μm. Met. The conductor layer 5 has a thickness of 8 μm and is uniformly and satisfactorily applied to the inner surface of the groove 4 and the recess 4a, and a part of the surface, in this example, the central part is concave. It was.

With respect to the reference example which is the wiring board 10 in which the recess 4a is formed in the center of the groove 4, the reference example and the comparative example which is a wiring board in which the recess 4a is not formed are socket-mounted. In accordance with the above, after the natural fall from the height of 500 mm on the concrete was performed 100 times, it was confirmed whether or not the socket has dropped. As a result, there was no dropping from reference example in the socket, in the comparative example has from dropping from the socket, it was found that the wiring substrate 10 is excellent in connection reliability.

( Example)
Similarly to the reference example , first, with respect to 100% by mass of ceramic powder prepared at a ratio of 96% by mass of aluminum oxide and 4% by mass of silicon oxide, magnesium oxide and calcium oxide as a sintering aid, An acrylic resin as an organic binder was further added in an amount of 9% by mass in solid content and dibutyl phthalate as a plasticizer in a proportion of 0.1% by mass, and mixed with a ball mill for 40 hours using toluene as a solvent to prepare a ceramic slurry. This ceramic slurry was formed into a sheet by a doctor blade method, and a ceramic green sheet having a thickness of 0.2 mm, which becomes the insulating substrate 1 after firing, was produced.

  Next, with respect to the first ceramic green sheet, a through-hole is not formed at a predetermined position where the groove 4 is formed, but a rectangular through-hole is formed at a position where the electronic component 6 is mounted. Holes were formed by punching.

  Next, with respect to the second ceramic green sheet, the cross-sectional shape with the upper surface diameter of 300 μm and the lower surface diameter of 500 μm, which finally becomes the groove 4 at a predetermined position where the groove 4 is formed, is a table Shaped through holes were formed by punching. Further, in addition to this through hole, a rectangular through hole similar to the above was formed by punching at a position to be the mounting portion 2 on which the electronic component 6 is mounted.

  Next, with respect to the through-hole which becomes the groove 4 of the ceramic green sheet, the cellulose nitrate is used in an amount of 0.8% by mass with 100% by mass of tungsten (W) powder having an average particle size of 1.90 μm as an organic binder. In addition to the addition, conductive paste obtained by adding and mixing diethylene glycol monobutyl ether acetate and dibutyl phthalate as solvents for viscosity adjustment, by screen printing, sucking from the lower surface side of the ceramic green sheet, around the opening of the through hole And the conductor paste layer used as the conductor layer 5 after baking was formed by printing on the inner wall surface of the through hole.

  Next, with respect to the third ceramic green sheet serving as the bottom surface of the mounting portion 2, a through hole having a diameter of 500 μm that finally becomes the groove 4 is formed by punching at a predetermined position where the groove 4 is formed. The conductor paste was printed and applied to the periphery of the through hole and the inner wall surface of the through hole while being sucked from the lower surface side by screen printing, to form a conductor paste layer that becomes the conductor layer 4 after firing. Also, using the same conductive paste, a conductive paste layer is printed and applied in a pattern to be a connection pad 3 on a portion to be the mounting portion 2 on the upper surface, and a conductive layer 5 is printed and applied to a through hole to be a groove 4 Connected to the paste layer.

  Next, the fourth ceramic green sheet has a trapezoidal cross section with a diameter of the upper surface of 500 μm and a diameter of the lower surface of 300 μm, which finally becomes the groove 4 at a predetermined position where the groove 4 is formed. A through-hole is formed by punching, and is applied to the periphery of the through-hole and the inner wall surface of the through-hole while sucking from the lower surface side by the screen printing method using the above-mentioned conductor paste, A conductive paste layer was formed. In addition, a conductor paste layer is printed and applied to a pattern that becomes a mounting connection pad 3 ′ after firing by screen printing using the above-described conductor paste at a position that becomes an outer peripheral portion of the lower surface of the ceramic green sheet, It was made to connect with the conductor paste layer used as the conductor layer 5 apply | coated to the through-hole which becomes this.

  The first ceramic green sheet is sintered by screen printing using the above-described conductor paste on the outer peripheral portion of the upper surface of the frame-shaped portion surrounding the through-hole serving as the mounting portion 2. A frame-shaped conductor paste layer that later becomes the frame-shaped metal layer 7 was formed.

  Then, these four ceramic green sheets are laminated and pressure-bonded to form a laminate, and after removing organic components by heating at a temperature of about 1000 ° C. for about 3 hours in a nitrogen atmosphere containing water vapor, Firing was performed in a nitrogen atmosphere containing about 6 hours at a temperature of about 1500 ° C.

  Further, after firing, the connection pad 3 formed on the mounting portion 2, the mounting connection pad 3 ′ formed on the outer periphery of the lower surface, the frame-shaped metal layer 7 formed on the outer periphery of the upper surface, and the outer surface of the insulating substrate 1. A nickel plating layer having a thickness of 3 μm is applied by electroplating to the conductor layer 4 on the inner surface of the groove 4 extending in the vertical direction, and the thickness is formed by electroplating on the nickel plating layer. Were sequentially deposited with a 0.5 μm gold plating layer.

Further, the insulating substrate 1 is cut along a dividing line passing through the center of the through hole serving as the groove 4 by a slicing method, thereby producing an embodiment of the wiring board 10 of the present invention as shown in FIG. . Oite in this example, a groove 4 extending in the vertical direction formed on the outer surface of the insulating base 1 is the length in the vertical direction 400 [mu] m, the cross-sectional shape in a semicircular shape, the top and bottom surface of the The narrowest width was 200 μm and the depth was 100 μm. The widest width of the recess 4a at the center of the groove 4 was 330 μm, and the depth of the recess 4a including the depth of the groove 4 was 165 μm. The conductor layer 5 has a thickness of 8 μm and is uniformly and satisfactorily applied to the inner surface of the groove 4 and the recess 4a, and a part of the surface, in this example, the central part is concave. It was.

The depth of the groove 4 gradually becomes deeper from the upper end and the lower end of the groove 4 toward the central portion in the vertical direction, and the wiring board 10 is formed with the recess 4a of the groove 4 according to the difference in depth. for example, and this embodiment, in a state that was soldered with Comparative example is a wiring substrate 10 not forming a recess 4a on the motherboard, the concrete on 500mm in accordance with JIS C0044
After the natural fall from the height of 100 times, it was confirmed that there was no drop off from the motherboard. As a result, there was no dropout from the motherboard in the example, but there was a dropout from the motherboard in the comparative example, and it was found that the wiring board 10 of the present invention was excellent in connection reliability.

  As a result of the above, according to the wiring board of the present invention, the groove (castellation) formed in the vertical direction on the side surface of the insulating base is formed with the concave portions extending at both ends in the width direction of the groove. Since the attached conductor layer and the external electric circuit can be firmly bonded and securely connected, it was confirmed that they can be connected and mounted satisfactorily and with high reliability.

The wiring board of the present invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from the gist of the present invention. For example, the groove 4 may have a shape that does not penetrate the outer surface of the insulating base 1 in the vertical direction as in the examples shown in FIGS. 1 to 4, or is insulated as in the examples shown in FIGS. 5 and 6. You may penetrate the outer surface of the base | substrate 1 to the up-down direction. According to this, since the groove 4 penetrates the outer surface of the insulating base body 1 in the vertical direction, the connection state between the spring terminal 12 and the recess 4a of the groove 4 when the socket 11 is mounted is determined. It can be easily seen from above. In addition, the groove 4 is formed on the outer surface of the insulating substrate 1 when mounted on the mother board using solder via the mounting connection pads 3 ′ (not shown in FIG. 6) located on the lower surface of the insulating substrate 1. Since it penetrates in the vertical direction, it is easy to see the position where the mounting connection pad 3 ′ is joined, and it is also easy to confirm the state of solder wetting and spreading to the mounting connection pad 3 ′, the groove 4 and the recess 4a. Therefore, it is possible to improve the mounting yield. Incidentally, FIG. 6 (a) shows a reference example of the embodiment of the wiring substrate, an enlarged view similar to FIG. 2 (a), the is a cross-sectional view of (b) the example socket implement portion thereof . The example shown in FIG. 6 is an example in which a groove 4 in which a recess 4 a similar to the example shown in FIG. 2 is formed is penetrated to the upper end of the outer surface of the insulating substrate 1.

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 2 ... Electronic component mounting part 3 ... Connection pad 3 '... Connection pad 4 for mounting ... Groove (castellation)
4a ... concave portion 5 ... conductor layer 6 ... electronic component 7 ... frame-shaped metal layer 8 ... bonding wire
10 ... wiring board
11 ... Socket
12 ... Spring terminal
13 ... Meniscus

Claims (1)

An insulating substrate having a mounting portion for electronic components on the main surface and a groove extending in the vertical direction on the outer surface;
A connection pad formed on the mounting portion to which an electronic component is electrically connected;
A conductor layer deposited on the inner surface of the groove and electrically connected to the connection pad;
A wiring board in which the conductor layer is connected to an external electric circuit via a conductive connecting material,
In the groove, a recess is formed across both ends of the groove in the width direction, the conductor layer is deposited along the recess, and a part of the surface of the conductor layer is concave ,
The depth of the groove is gradually deeper from the upper end and the lower end of the groove toward the center in the vertical direction, and the concave portion of the groove is formed according to the difference in depth. Wiring board.

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