JP2006270082A - Wiring board and electronic device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having an excellent implementation reliability by firmly joining electrodes of electronic components to a plurality of dummy pads. <P>SOLUTION: The wiring board is formed of: wiring conductors 3 arranged inside an insulating base 1 made up by stacking a plurality of ceramic layers; and a lattice-like arrangement of a plurality of connection pads 2 provided on a major surface of the insulating base 1 and electrically connected to the wiring conductors 3 through via conductors 4, and a plurality of dummy pads 5 electrically connected by way of via conductors 6 to junction layers 7 provided between the ceramic layers of the insulating base 1, independently from the wiring conductors 3. The via conductors 6 in connection with the dummy pads 5 are arranged in the ceramic layer that makes up the major surface of the insulating base 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring board used for mounting electronic components such as semiconductor elements and capacitive elements, and an electronic device using the same.

  Conventionally, semiconductor integrated circuit elements such as IC and LSI, LD (semiconductor laser), LED (light emitting diode), PD (photodiode), optical semiconductor elements such as CCD, line sensor, image sensor, piezoelectric vibrator, crystal vibrator As a wiring board on which various vibrators and other electronic components are mounted, a plurality of insulating layers made of ceramic materials such as aluminum oxide sintered bodies and glass ceramic sintered bodies (glass ceramics) are stacked. An insulating base having an electronic component mounting portion on the upper surface, a wiring conductor formed inside the insulating base, and a plurality of connection pads arrayed on the main surface of the insulating base and electrically connected to the wiring conductor. The thing of the structure which comprised was known.

  The electrical connection between the wiring conductor and the connection pad is usually made via a via conductor formed so as to penetrate the insulating layer in the thickness direction from the connection pad to the wiring conductor.

  Electronic parts are mounted on the mounting part, and the electrodes of the electronic parts are connected to the connection pads via connecting materials such as solder and bonding wires, and the electronic parts are sealed with a lid or a sealing resin as required. Thus, an electronic device is manufactured.

  For this electronic device, a part of the wiring conductor is exposed on the side surface and lower surface of the insulating base, and the exposed part is connected to the electric circuit of the external electric circuit board via solder etc., so that the electrodes of the electronic component are connected. It is electrically connected to an external electric circuit through the pad, the via conductor, and the wiring conductor.

  Such an electronic device is used as a component that is mounted on an electronic device such as a mobile phone, for example. In recent years, demands for downsizing and high-density mounting are increasing.

  In order to meet such a demand, flip-chip mounting of electronic components has been studied.

  In flip chip mounting, solder bumps are respectively formed on a plurality of electrodes arranged vertically and horizontally on the main surface of an electronic component, and the electrodes are aligned with a plurality of connection pads formed on the upper surface of an insulating substrate. In this method, the solder bump is melted to connect the electrode and the connection pad.

  Therefore, it is necessary to form the connection pads of the wiring board so as to face the electrodes arranged in a grid pattern on the main surface of the electronic component, and a plurality of grid pads are formed in the center of one main surface of the insulating substrate. An array is formed.

  In this case, the electrodes of the electronic component are basically arranged in a grid pattern, but the number of the electrodes of the electronic component is determined according to the function, application, etc. of the electronic component. It does not necessarily match the number of grid points when arranged in the. Therefore, there may be a lattice point where no connection pad is arranged.

In such a case, since the number of connection pads (that is, the connection area between the electronic component and the wiring board) is reduced and the strength of mechanical connection of the electronic component to the wiring board may be reduced, the connection pads are not formed. It is conceivable that dummy pads (not connected to via conductors or wiring conductors) are arranged at the lattice points to reinforce the connection.
JP 2004-153015 A JP 2002-9444 A Japanese Patent Laid-Open No. 1993-206298

  However, in the conventional wiring board described above, the connection pads are connected to the wiring conductors, via conductors, etc., and are firmly joined to the insulating base via the wiring conductors, etc., whereas the dummy pads are formed on the surface. The dummy pad is peeled off from the main surface of the insulating substrate due to the stress at the time of mounting the electronic component (for example, thermal stress due to the difference in thermal expansion coefficient between the electronic component and the insulating substrate). There was a problem that. When the dummy pad is peeled off, the electrical and mechanical connection between the electronic component and the wiring board through the connection pad cannot be effectively reinforced, and a defect that leads to a decrease in connection reliability is induced.

  The present invention has been devised in view of the above disadvantages, and an object thereof is to provide a wiring board having excellent mounting reliability by firmly bonding a plurality of dummy pads and electrodes of an electronic component. .

  In the wiring board of the present invention, a wiring conductor is disposed inside an insulating base formed by laminating a plurality of ceramic layers, and electrically connected to the main surface of the insulating base via a via conductor. A plurality of connection pads to be connected, and a plurality of dummy pads electrically connected via via conductors to a bonding layer provided between the ceramic layers of the insulating base, in a state independent of the wiring conductors, It is characterized by being arranged in a lattice pattern.

  The wiring board according to the present invention is preferably characterized in that the via conductor connected to the dummy pad is provided only on a ceramic layer which is a main surface of the insulating base.

  In the wiring board of the present invention, preferably, the via conductor connected to the dummy pad has a smaller cross-sectional area in the thickness direction of the insulating base than the via conductor connected to the connection pad. It is characterized by.

  The wiring board of the present invention is preferably characterized in that the ceramic layer having the via conductor connected to the dummy pad has a lower relative dielectric constant than other ceramic layers constituting the insulating base. To do.

  The wiring board of the present invention is preferably characterized in that the bonding layer is disposed between ceramic layers adjacent to a ceramic layer serving as a main surface of the insulating base.

  The wiring board of the present invention is preferably characterized in that the bonding layer is disposed so that at least one of via conductors connected to the connection pad penetrates in a plan view.

  The wiring board of the present invention is preferably an electronic device in which an electronic component element having a plurality of terminals connected to the connection pad and the dummy pad via a brazing material is flip-chip mounted on the wiring board. Device.

  According to the wiring board of the present invention, the wiring conductor is disposed inside the insulating base formed by laminating a plurality of ceramic layers, and the main surface of the insulating base is electrically connected to the wiring conductor via the via conductor. A plurality of connection pads to be connected and a plurality of dummy pads electrically connected to the bonding layer provided between the ceramic layers of the insulating base via via conductors in a state independent of the wiring conductor. Since the dummy pad is firmly bonded to the insulating base by the anchor effect of the via conductor, the via conductor can be firmly fixed between the ceramic layers with the bonding layer, and the thermal stress etc. Even if this stress is applied, the dummy pad can be effectively prevented from peeling off from the main surface of the insulating base.

  For example, if it is a dummy pad with only a pattern formed on the surface, it may be peeled off due to the influence of stress generated during mounting, but it is peeled off by the anchor effect because one end is joined to the via conductor. Can be effectively prevented.

  Further, the other end portion of the via conductor is connected to a bonding layer provided inside the insulating substrate, and the via conductor itself is firmly bonded to the insulating substrate, thereby obtaining a stronger anchor effect. As a result, peeling of the dummy pad is more effectively prevented, and the connection reliability of the wiring board can be further improved.

  Further, according to the wiring board of the present invention, preferably, the via conductor connected to the dummy pad is disposed only in the ceramic layer which is the main surface of the insulating base, so that the dummy pad in the inside of the insulating base is provided. The range in which the via conductor connected to is installed can be kept small. For this reason, it is possible to suppress the influence of the via conductor connected to the dummy pad on the location of the wiring conductor provided inside the insulating base. In other words, since the ceramic layer other than the ceramic layer serving as the main surface of the insulating base is less affected by the location of the wiring conductor, the insulating base does not need to have a large substrate size, and an extra wiring layer is unnecessary. Therefore, it is not necessary to increase the thickness of the insulating substrate. Therefore, according to this configuration, it is possible to provide a wiring board that is excellent in connection reliability of electronic components, does not need to be enlarged, and is effective for downsizing.

  The wiring board of the present invention is connected to the dummy pad because the via conductor connected to the dummy pad has a smaller cross-sectional area in the thickness direction of the insulating substrate than the via conductor connected to the connection pad. The distance between the via conductor connected to the connection pad and the via conductor connected to the connection pad is increased, and the stray capacitance generated between the via conductor connected to the dummy pad and the via conductor connected to the connection pad can be reduced. Therefore, problems such as deterioration of transmission characteristics in the via conductor connected to the connection pad due to the stray capacitance are suppressed, so that a wiring board having excellent electrical characteristics can be provided.

  The wiring board of the present invention is connected to the dummy pad because the ceramic layer having the via conductor connected to the dummy pad has a lower relative dielectric constant than the other ceramic layers constituting the insulating base. The stray capacitance generated between the via conductor and the via conductor connected to the connection pad can be further reduced. For this reason, problems such as deterioration of transmission characteristics in the via conductor connected to the connection pad due to the stray capacitance are suppressed, so that a wiring board having better electrical characteristics can be provided.

  In the wiring board of the present invention, since the bonding layer is disposed between the ceramic layers adjacent to the ceramic layer that is the main surface of the insulating base, the wiring conductor disposed in the insulating base is provided in a location. The influence received can be suppressed lower. In other words, since the arrangement of the bonding layer is limited, the influence of the location of the wiring conductor on the ceramic layer other than the ceramic layer serving as the main surface of the insulating base is low, so there is no need for the insulating base to have a large substrate size. In addition, since an extra wiring layer is unnecessary, it is not necessary to increase the thickness of the insulating base. Therefore, according to this configuration, it is possible to provide a wiring board that is excellent in connection reliability of electronic components, does not need to be enlarged, and is effective for downsizing.

  It is also possible to suppress the occurrence of problems such as inclination (so-called coplanarity degradation) on the main surface of the insulating base due to the plurality of bonding layers scattered between different layers and partially varying the thickness between the layers.

  In the wiring board according to the present invention, since the bonding layer is disposed so that at least one of the via conductors connected to the connection pad penetrates in plan view, the other end of the via conductor bonded to the dummy pad Is connected to a bonding layer having a large area, and an even stronger anchor effect can be obtained. As a result, peeling of the dummy pad is more effectively prevented, and the connection reliability of the wiring board can be further improved.

  In addition, according to the present invention, on the wiring board, an electronic component element having a plurality of terminals connected to the connection pad and the dummy pad via the brazing material is flip-chip mounted to constitute an electronic device. Miniaturization and high-density mounting are possible.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a plan view showing an example of an embodiment of a wiring board according to the present invention, and FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. In FIG. 1, 1 is an insulating substrate, 2 is a connection pad, 3 is a wiring conductor, 4 is a via conductor, 5 is a dummy pad, 6 is a dummy via conductor, and 7 is a bonding layer. The insulating substrate 1, connection pad 2, wiring conductor 3, via conductor 4, dummy pad 5, dummy via conductor 6 and bonding layer 7 basically constitute the wiring substrate 9 of the present invention.

  The insulating substrate 1 is formed by laminating a plurality of ceramic layers 1a made of a ceramic material such as an aluminum oxide sintered body, a glass ceramic sintered body (glass ceramic), an aluminum nitride sintered body, and a mullite sintered body. ing.

  For example, when each ceramic layer 1a is made of an aluminum oxide sintered body, the insulating base 1 is obtained by adding and mixing an appropriate organic binder and solvent to raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide. A plurality of ceramic green sheets (ceramic raw sheets) are obtained by forming a slurry into a slurry by using a sheet forming technique such as a doctor blade method or a calender roll method. The ceramic green sheet is formed into an appropriate shape by cutting or punching, and the ceramic green sheets are laminated to form a laminated body. Finally, the laminated body is fired at a temperature of about 1600 ° C. in a reducing atmosphere. Thus, the insulating substrate 1 is manufactured.

  The insulating base 1 has, for example, a semiconductor integrated circuit element such as an IC or LSI, an optical semiconductor element such as an LD (semiconductor laser), an LED (light emitting diode), a PD (photodiode), a CCD, a line sensor, or an image sensor on the upper surface. And a mounting portion (not shown) for mounting a vibrator such as a piezoelectric vibrator and a crystal vibrator and other various electronic components.

  A connection pad 2 is formed on the main surface (upper surface in the example of FIG. 1) of the insulating base 1, and a wiring conductor 3 is formed inside the insulating base 1 (interlayer of the insulating layer 1a). In the example of FIG. 1, the connection pad 2 and the wiring conductor 3 are electrically connected via a via conductor 4 formed so as to penetrate the ceramic layer 1a in the thickness direction.

  A plurality of electrodes arranged vertically and horizontally on the main surface of an electronic component (not shown) mounted on the mounting portion are opposed to the connection pad 2 and a conductive connecting material (not shown) such as solder is provided. The electrode of the electronic component is connected to the insulating base via the connection pad 2 and the wiring conductor 3 by exposing the part of the wiring conductor 3 to the side surface and the lower surface of the insulating base 1. Derived to the side surface and the lower surface of 1. By electrically connecting the lead-out portion of the wiring conductor 3 to an external electric circuit via solder or the like, the electrode of the electronic component is electrically connected to the external electric circuit via the connection pad 2 and the wiring conductor 3. Connected.

  In addition, the insulating base 1 has a dummy pad 5 that is not electrically connected to the wiring conductor 3 on the main surface (upper surface). The dummy pad 5 has, for example, the same shape and dimensions as the connection pad 2.

  In addition, a via conductor (hereinafter referred to as a dummy via conductor) 6 connected to the dummy pad 5 is formed at one end of the dummy pad 5.

  With this configuration, due to the anchor effect of the dummy via conductor 6, the bonding of the dummy pad 5 to the insulating substrate 1 can be strengthened.

  Further, the other end portion of the dummy via conductor 6 is connected to the bonding layer 7 provided inside the insulating base 1, and the via conductor 6 itself is also strongly bonded by the insulating base, thereby further enhancing the anchor effect. It becomes.

  As a result, peeling of the dummy pad 5 can be effectively suppressed, so that the connection pad 2 and the dummy pad 5 can be firmly bonded to the electrode of the electronic component, and a wiring board having excellent mounting reliability can be obtained. be able to.

  The bonding layer 7 is made of a ceramic material such as an aluminum oxide sintered body, a glass ceramic sintered body (glass ceramic), an aluminum nitride sintered body, a mullite sintered body, tungsten, molybdenum, manganese, copper, A dummy via conductor 6 such as a metal material such as silver, palladium, or gold is formed of a material to which the dummy via conductor 6 is firmly connected by means of simultaneous firing or the like.

  The bonding layer 7 is an insulating material such as a ceramic material in order to prevent the bonding layer 7 itself or the dummy via conductor 6 from being electrically short-circuited with the wiring conductor 3 disposed inside the insulating base 1. It is preferable that it consists of.

  Further, the bonding layer 7 is preferably formed of the same ceramic sintered body as that of the insulating substrate 1 from the viewpoint of bonding strength to the insulating substrate 1 and productivity.

  The dimension of the bonding layer 7 is preferably larger than the outer dimension (diameter) dimension of the dummy via conductor 6.

  In addition, the shape of the bonding layer 7 is preferably substantially circular in order to prevent stress concentration. In this case, a circular shape having irregularities on a part of the outer edge may be used instead of a perfect circle. Moreover, elliptical shape etc. may be sufficient.

  On the other hand, the wiring conductor 3, the connection pad 2, the via conductor 4, the dummy pad 5, and the dummy via conductor 6 are made of a metal material such as tungsten, molybdenum, manganese, copper, silver, palladium, gold, and the like. The insulating layer 1a of the insulating substrate 1 is formed in the form of a metal foil, a plating layer, or the like.

  When the wiring conductor 3, the connection pad 2, the through conductor 4, the dummy pad 5, and the dummy via conductor 6 are made of, for example, a copper metallized conductor, a metal paste prepared by adding an organic solvent, a resin binder, or the like to copper powder. Is formed by printing, filling and filling the surface of the green sheet to be the insulating layer 1a and the inside of the through holes previously punched and formed in the green sheet. The through hole is formed by a forming means such as a mechanical punching process using a metal pin or a hole process using a laser beam.

  Further, as shown in FIG. 2, the wiring board 9 of the present invention is preferably insulated because the via conductor 6 connected to the dummy pad 5 is disposed only on the ceramic layer which is the main surface of the insulating base 1. The range in which the via conductor 6 connected to the dummy pad 5 is installed in the inside of the base 1 can be kept small. For this reason, the influence of the via conductor 6 connected to the dummy pad 5 on the setting of the arrangement location of the wiring conductor 3 arranged inside the insulating substrate 1 can be suppressed low. That is, in the ceramic layers other than the ceramic layer which is the main surface of the insulating base 1, the influence on the location of the wiring conductor 3 is low, so that the insulating base 1 does not need to have a large substrate size and an extra wiring layer is provided. Since it is unnecessary, it is not necessary to increase the thickness of the insulating substrate 1. Therefore, according to this configuration, it is possible to obtain a wiring board 9 that is excellent in connection reliability of electronic components, does not need to be enlarged, and is effective for downsizing.

  2A is a plan view showing an example of another embodiment of the wiring board of the present invention, FIG. 2B is a cross-sectional view of FIG. 2A, and FIG. 3 is FIG. It is a plane perspective view of (a). 2A and 2B, the same parts as those in FIGS. 1A and 1B are denoted by the same reference numerals.

  In the wiring board 9 of the present invention, the via conductor 6 connected to the dummy pad 5 preferably has a smaller cross-sectional area in the thickness direction of the insulating base 1 than the via conductor 4 connected to the connection pad 2. Therefore, the distance between the via conductor 6 connected to the dummy pad 5 and the via conductor 4 connected to the connection pad 2 becomes large, and the via conductor 6 connected to the dummy pad 5 and the via connected to the connection pad 2. The stray capacitance generated between the conductor 4 can be reduced. For this reason, problems such as deterioration of transmission characteristics in the via conductor 6 connected to the connection pad 2 due to stray capacitance are suppressed, so that the wiring board 9 having excellent electrical characteristics can be provided.

  In order to make the via conductor 6 connected to the dummy pad 5 smaller than the via conductor 4 connected to the connection pad 2, the via conductors 4 and 6 are formed by punching or laser processing in a green sheet state. When forming the through hole, the through hole to be the via conductor 6 connected to the dummy pad 5 can be obtained in advance so as to reduce the punching area. The area of the cross section of the through hole can be adjusted to a predetermined area by means such as adjusting the pin diameter of the metal pin used for punching.

  In the wiring substrate 9 of the present invention, the ceramic layer having the via conductor 6 connected to the dummy pad 5 preferably has a lower relative dielectric constant than the other ceramic layers constituting the insulating base 1. The stray capacitance generated between the via conductor 6 connected to the dummy pad 5 and the via conductor 4 connected to the connection pad 2 can be further reduced. For this reason, problems such as deterioration of transmission characteristics in the via conductor 4 connected to the connection pad 2 due to the stray capacitance are suppressed, so that the wiring board 9 having better electrical characteristics can be provided.

  In order to lower the relative dielectric constant of the ceramic layer having the via conductor 6 connected to the dummy pad 5 with respect to the other ceramic layers constituting the insulating base 1, the via conductor 6 connected to the dummy pad 5 is used. It is obtained by adding a metal composite oxide such as Ag, Al, Si or the like to a ceramic material in a larger amount than a ceramic material for a green sheet that becomes another ceramic layer. It is done.

  The relative dielectric constant of the ceramic layer having the via conductor 6 connected to the dummy pad 5 is preferably 80% or less with respect to the relative dielectric constant of the other ceramic layers constituting the insulating substrate 1.

  In the wiring substrate 9 of the present invention, the bonding layer 7 is preferably disposed between the ceramic layers adjacent to the ceramic layer that is the main surface of the insulating base 1. The influence on the setting of the place where the conductor 3 is disposed can be further reduced. That is, since the arrangement of the bonding layer 7 is limited, the influence of the location of the wiring conductor 3 on the ceramic layer other than the ceramic layer serving as the main surface of the insulating base 1 is low. There is no need to increase the thickness of the insulating substrate 1 because no extra wiring layer is required. Therefore, according to this configuration, it is possible to obtain a wiring board 9 that is excellent in connection reliability of electronic components, does not need to be enlarged, and is effective for downsizing.

  It is also possible to suppress the occurrence of problems such as tilting (so-called coplanarity reduction) in the main surface of the insulating base 1 due to the plurality of bonding layers 7 being scattered between different layers and the thickness of the layers partially varying. .

  In the wiring board 9 of the present invention, as shown in FIG. 3, it is preferable that the bonding layer 7 is disposed so that at least one of the via conductors 4 connected to the connection pad 2 penetrates in a plan view. Therefore, the other end portion of the via conductor 6 bonded to the dummy pad 5 is connected to the bonding layer 7 having a large area, and an even stronger anchor effect can be obtained. As a result, the peeling of the dummy pad 5 is more effectively prevented, and the connection reliability of the wiring board 9 can be further improved.

  Then, an electronic component (not shown) is mounted on the insulating substrate 1 of the wiring board 9 described above, and the electrodes of the electronic component are electrically connected to the connection pads 2, and the electronic component is attached to the lid as necessary. The electronic device is formed by sealing with (not shown) or a sealing resin (not shown).

  The electronic component is mounted by, for example, bonding and fixing the electronic component to the mounting portion via an adhesive material such as brazing material, glass, or resin.

  When electronic parts are sealed with a lid, a metal material such as an iron-nickel-cobalt alloy or iron-nickel alloy, a ceramic material such as an aluminum oxide sintered body, a material such as glass or resin is used. A lid is prepared by processing into a predetermined shape, and the lid is joined to the insulating base 1 to close the mounting portion, so that the electronic component is hollow inside the container formed by the lid and the insulating base 1. It is hermetically sealed in the state.

  Further, when it is not necessary to seal the electronic component in a hollow state, the electronic component can be covered with a sealing resin made of an epoxy resin or the like so as to cover the electronic component.

  Such an electronic device is used as a part of an electronic device such as a small and high-precision mobile phone.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

(A) It is a top view which shows an example of embodiment of the wiring board of this invention, (b) is sectional drawing of (a). (A) It is a top view which shows an example of other embodiment of the wiring board of this invention, (b) is sectional drawing of (a). FIG. 3 is a plan perspective view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating base | substrate 1a ... Insulating layer 2 ... Connection pad 3 ... Wiring conductor 4 ... Via conductor 5 ... Dummy pad 6 ... Dummy via conductor 7 ... Bonding layer 9 ... Wiring board

Claims (7)

A plurality of connection pads, wherein a wiring conductor is disposed inside an insulating base formed by laminating a plurality of ceramic layers, and is electrically connected to the main surface of the insulating base via the via conductor to the wiring conductor. And a plurality of dummy pads connected via via conductors to a bonding layer provided between the ceramic layers of the insulating base, in a state independent of the wiring conductor, A characteristic wiring board. 2. The wiring board according to claim 1, wherein the via conductor connected to the dummy pad is provided only on a ceramic layer which is a main surface of the insulating base. The area of the cross section with respect to the thickness direction of the said insulation base | substrate is smaller than the said via conductor connected to the said connection pad, The said via conductor connected to the said dummy pad is characterized by the above-mentioned. Wiring board as described in. The wiring board according to claim 1, wherein a ceramic layer having the via conductor connected to the dummy pad has a lower relative dielectric constant than other ceramic layers constituting the insulating base. The wiring board according to claim 1, wherein the bonding layer is disposed between ceramic layers adjacent to a ceramic layer serving as a main surface of the insulating base. The wiring board according to claim 5, wherein the bonding layer has at least one via conductor connected to the connection pad penetrating in a plan view. An electronic component element having a plurality of terminals connected to the connection pad and the dummy pad via a brazing material is flip-chip mounted on the wiring board according to any one of claims 1 to 6. Electronic equipment.

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