JP2013045900A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board in which a plating layer is well deposited on a surface metal layer and which achieves excellent reliability.SOLUTION: A wiring board 10 of a present embodiment comprises: an insulating base 1; a heat dissipation member 2 containing CuW and provided in the insulating base 1 so as to be partially exposed on the insulating base 1; a first surface metal layer 3a containing Mo as a major ingredient and provided on a surface of the insulating base 1 so as to cover the heat dissipation member 2 in contact with the heat dissipation member 2 and having a surface containing Cu; a metal member 3c composed of CuW and provided on the surface of or inside the insulating base 1 in contact with the second surface metal layer 3b; and plating layers respectively provided on the first surface metal layer 3a and the second surface metal layer 3b. A metal layer can be deposited on each of the surfaces of the first surface metal layer 3a and the second surface metal layer 3b starting from Cu.

Description

  The present invention relates to a wiring board for mounting an electronic component such as a semiconductor element or a light emitting element.

  Conventionally, an insulating substrate made of a ceramic such as an aluminum oxide sintered body (alumina ceramic) is used as a wiring board on which electronic components are mounted and incorporated in an electronic device. Some wiring boards have a heat radiating member embedded in an insulating base for the purpose of improving heat dissipation (see, for example, Patent Document 1).

  The heat dissipating member is used, for example, to release heat generated by an electronic component mounted on a wiring board to the outside and improve heat dissipation. When the insulating substrate is made of ceramics, the heat radiating member is made of a material having a thermal conductivity higher than that of ceramics and a thermal expansion coefficient comparable to that of ceramics.

  Some of such wiring boards include a surface metal layer provided on the surface of an insulating substrate. When the material of the insulating substrate is a ceramic material having a high sintering temperature such as the above-mentioned alumina ceramic, a high melting point metal material may be used as the material of the surface metal layer for the purpose of firing simultaneously with the insulating substrate.

  Such a wiring board may use, for example, a metal containing Cu as the material of the heat dissipation member, and may use, for example, molybdenum (Mo) as the material of the surface metal layer.

JP 2006-066409 A

  When the metal containing Cu is used for the heat dissipating member and the molybdenum (Mo) is used for the surface metal layer as in the wiring board described above, the surface metal layer provided in contact with the heat dissipating member Then, Cu is diffused and Cu is deposited on the surface, so that the plating layer is easily deposited starting from Cu.

  However, when, for example, molybdenum (Mo) is used as the refractory metal material for the surface metal layer that is not in contact with the heat dissipation member, an attempt is made to deposit an electroless plating layer such as nickel on the exposed surface of the surface metal layer. In some cases, the plating layer is difficult to adhere to the surface of the surface metal layer.

  The present invention has been devised in view of the above-mentioned problems of the prior art, and its purpose is to provide a highly reliable wiring board in which a plating layer is deposited on a surface metal layer not in contact with a heat dissipation member. It is to provide.

A wiring board according to an aspect of the present invention includes an insulating base, a first surface metal layer provided on a surface of the insulating base, including Mo as a main component, and having a surface portion including Cu. And a heat radiating member that is in contact with the first surface metal layer, includes Cu, and is provided on the surface of the insulating base, and includes Mo as a main component. A second surface metal layer having a surface portion containing Cu, and a metal member provided on or in the surface of the insulating base, in contact with the second surface metal layer, and containing Cu And a plating layer provided on each of the first and second surface metal layers.

  According to the wiring board according to one aspect of the present invention, the second surface metal layer provided on the surface of the insulating base, containing Mo as a main component, and having a surface portion containing Cu, and the insulating substrate. It is provided on the surface or inside of the substrate, is in contact with the second surface metal layer, and includes a metal member containing Cu and a plating layer provided on each of the second surface metal layers. Since it is such a structure, when the 2nd surface metal layer deposits an electroless plating layer, it becomes easy to deposit a plating layer on the surface of the 2nd surface metal layer from Cu.

(A) is a top view of the wiring board which shows an example of the 1st Embodiment of this invention, (b) is a bottom view of (a). It is sectional drawing in the AA line of Fig.1 (a). It is sectional drawing of the wiring board which shows the other example of the 1st Embodiment of this invention. (A) is a top view of the wiring board which shows an example of the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view of the electronic apparatus which mounted the electronic component in the wiring board which is an example of the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). is there. (A) is a top view of the electronic device which shows the other example of the 1st Embodiment of this invention, (b) is a bottom view of (a). It is sectional drawing in the AA line of Fig.6 (a). (A) is a top view of the electronic device which shows the other example of the 1st Embodiment of this invention, (b) is a bottom view of (a). It is sectional drawing in the AA line of Fig.8 (a). (A) And (b) is sectional drawing of the wiring board which shows an example of the 2nd Embodiment of this invention.

  Several exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
The wiring board 10 in the first embodiment of the present invention is provided on the surface of the insulating base 1 and the insulating base 1 as in the examples shown in FIGS. 1 to 9 and contains Mo as a main component. , A first surface metal layer 3a having a surface portion containing Cu, and provided inside the insulating substrate 1, in contact with the first surface metal layer 3a, and insulated from the heat dissipation member 2 containing Cu. A second surface metal layer 3b provided on the surface of the base body 1 and containing Mo as a main component and having a surface portion containing Cu, and a second surface metal on the surface or inside of the insulating base body 1. In contact with the layer 3b, a metal member 3c containing Cu and a plating layer respectively provided on the second surface metal layer 3b are provided.

  The insulating substrate 1 is made of a ceramic such as an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a mullite sintered body, or the like.

If the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, an appropriate organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to form a slurry. None, this is formed into a sheet shape by a conventionally known doctor blade method, calendar roll method, etc. to obtain a ceramic green sheet, and then a suitable punching process is performed on the ceramic green sheet, and a plurality of these are laminated, Manufactured by firing at a high temperature (about 1300 ° C to 1400 ° C).

  The heat radiating member 2 is embedded in the insulating base 1, and is formed in, for example, a rectangular shape with a corner having an arc shape in a plan view or a column shape having a circular bottom surface. The heat dissipating member 2 is for releasing heat generated by the electronic component to the outside of the wiring board 10 to improve heat dissipation, and is formed larger than the electronic component in plan view. Such a heat radiating member 2 is formed by providing a hole in a ceramic green sheet for the insulating substrate 1 by punching by a die or punching or laser processing, and placing a metal sheet or metal paste to be the heat radiating member 2 in this hole. It is produced by placing.

  When the heat radiating member 2 is exposed from the upper surface of the insulating base 1 as in the examples shown in FIGS. 1 to 9, the heat radiating property of the wiring board 10 is improved as compared with the case where the heat radiating member 2 is not exposed. It is effective. The heat radiating member 2 may be exposed from both surfaces of the insulating base 1 as in the examples shown in FIGS. 1 to 4, or may be exposed only from one main surface of the insulating base 1 as in the example shown in FIG. 7. It may be provided.

  When such a heat radiating member 2 is manufactured using a metal sheet, the metal sheet has the same shape as the hole of the ceramic green sheet for the insulating substrate 1 in plan view and the same depth as the hole of the ceramic green sheet. It suffices if it is formed to have a thickness and is embedded so as to fill the hole of the ceramic green sheet. When the metal sheet is embedded in the ceramic green sheet by punching at the same time, a molded body can be produced efficiently.

  For example, a metal sheet is placed on the upper surface of the ceramic green sheet for the insulating substrate 1 in which the through hole is formed, and the metal sheet and the ceramic are formed from the metal sheet side using a punching die that forms a through hole in the ceramic green sheet. When a through hole is punched into the green sheet, a metal sheet punched to the same size as the through hole can be fitted into the through hole of the ceramic green sheet.

  In such a metal sheet, an organic binder and an organic solvent are added to a metal powder as necessary to obtain a slurry by adding a predetermined amount of a plasticizer or a dispersant, and this is made of a resin such as PET (polyethylene terephthalate) or paper. It is prepared by applying onto a support by a forming method such as a doctor blade method, a lip coater method or a die coater method, forming it into a sheet, and drying it by a drying method such as hot air drying, vacuum drying or far-infrared drying. .

  As the metal powder, a powder made of tungsten (W) and copper (Cu) is used. The metal powder may be mixed or alloyed. When the metal sheet which mixed Cu powder and W powder is used, it can be set as the thermal radiation member 2 which consists of copper tungsten (CuW) excellent in heat dissipation.

  As the organic binder used for the metal sheet and the solvent contained in the slurry, the same materials as those used for the ceramic green sheet can be used.

  The amount of the organic binder added is 10-20% by mass with respect to the metal powder, as long as it is easily decomposed and removed during firing and the metal powder is dispersed and the green sheet is easy to handle and process. Degree is desirable.

The amount of the solvent is 30 to 100% by mass based on the metal powder, so that the slurry can be satisfactorily coated on the support, specifically 3 to 100 cps.
It is desirable to be about s.

  Moreover, when the heat radiating member 2 is manufactured using a metal paste, the metal paste should just be filled and arrange | positioned at the hole of the ceramic green sheet 1. FIG. Further, the metal paste may be adjusted to have a viscosity so as to be held in the hole of the ceramic green sheet 1, but it is preferable that the hole of the ceramic green sheet 1 has a bottom.

  The metal paste for the heat dissipating member 2 is mixed by kneading means such as a ball mill, a three-roll mill or a planetary mixer by adding an organic binder, an organic solvent, and, if necessary, a dispersing agent to the metal powder as the main component. And kneading.

  The amount of the organic binder used in the metal paste for the heat radiating member 2 may be an amount that can be easily decomposed and removed during firing and can disperse the metal powder, and is 5 to 20% by mass with respect to the metal powder. It is desirable that the amount be approximately the same. The solvent is added in an amount of 4 to 15% by mass with respect to the metal powder, and is adjusted to about 15000 to 40000 cps.

  In addition, in order to match the firing shrinkage behavior and shrinkage rate of the ceramic green sheet 1 during firing or to ensure the bonding strength of the wiring conductor 4 after firing, the metal paste is added with glass or ceramic powder. Also good.

  Further, when a metal paste is used as the metal material for the heat radiating member 2, the metal paste may be adjusted to have a viscosity that can be held in the hole of the ceramic green sheet 1. It is preferable to have a bottom.

  Further, as in the example shown in FIG. 7, the heat radiating member 2 is different in size between the upper surface side and the lower surface side of the wiring board 10 in a plan view, and has a step between the upper surface side and the lower surface side. May be. This is effective in securing a region for arranging the wiring conductor 4 on the upper surface side of the insulating substrate 1.

  In order to manufacture the heat dissipation member 2 having such a shape, a laminated body in which a plurality of ceramic green sheets are stacked is formed, a first through hole is formed in the upper ceramic green sheet, and a first ceramic green sheet is formed in the lower ceramic green sheet. A second through hole having a diameter larger than that of the through hole is formed, and a metal sheet or a metal paste serving as a heat radiation member 2 having a size corresponding to each of these through holes is embedded, and the upper and lower ceramic green sheets are embedded. It can be formed by laminating and pressing.

  The first surface metal layer 3a and the second surface metal layer 3b are made of metal powder metallization of molybdenum (Mo). The metal powder may be mixed or alloyed.

  Such a first surface metal layer 3a is formed as follows. The metallized paste for the first surface metal layer 3a using the above metal powder is screen-printed in a predetermined shape so as to cover the metal sheet or metal paste for the heat dissipation member 2 embedded in the ceramic green sheet for the insulating substrate 1 Print by law. Similarly, the metallized paste for the second surface metal layer 3b is printed at a predetermined position on the ceramic green sheet for the insulating substrate 1 in a predetermined shape by a screen printing method or the like. The metallized paste for the second surface metal layer 3b is arranged on the main surface around the region where the first surface metal layer 3a is arranged or on the main surface opposite to the main surface on which the first surface metal layer 3a is arranged. Is done. Thereafter, the ceramic green sheet for the insulating substrate 1 is fired simultaneously. The metallized paste for the first surface metal layer 3a and the second surface metal layer 3b can be produced by the same method as the metal paste for the heat dissipation member 2 described above.

The metallized paste for the first surface metal layer 3a is in contact with the metal material (metal sheet or metal paste) for the heat radiating member 2. From this, for example, when the ceramic green sheet for the insulating base 1 of the aluminum oxide sintered body is fired, by firing at a temperature higher than the melting point of Cu (about 1300 ° C. to 1400 ° C.), Cu and Cu contained in the metal sheet or metal paste serving as the heat radiating member 2 containing W melts, passes between the Mo metal particles of the first surface metal layer 3a, and diffuses to the surface of the first surface metal layer 3a. Thus, the surface of the first surface metal layer 3a can be made of Mo and containing Cu.

  1 to 4, when the heat dissipation member 2 penetrates the insulating base 1, the first surface metal layer 3 a is a portion where the heat dissipation member 2 is exposed on the upper surface of the insulating base 1. And the heat dissipating member 2 are arranged so as to cover the portions exposed on the lower surface of the insulating substrate 1. In such a case, the heat of the electronic component 5 can be radiated from the upper surface side to the lower surface side of the wiring board 10.

  When the heat dissipation member 2 is exposed only on the upper surface of the insulating base 1 as in the example shown in FIG. 7, the first surface metal layer 3 a is a portion where the heat dissipation member 2 is exposed on the upper surface of the insulating base 1. It is arranged to cover. In this case, the heat of the electronic component 5 is easily transmitted to the heat radiating member on the upper surface side of the wiring board 10. Further, it is effective for suppressing a short circuit of the first surface metal layer 3a on the lower surface of the wiring board 10. Further, the second surface metal layer 3b can be formed in a wide area, and the bonding with the external circuit board can be made favorable. As shown in the example of FIG. 6, if one of the second surface metal layers 3 b is widened so as to overlap the heat radiating member 2 in plan view, the wiring board 10 having excellent heat dissipation and bonding properties can be obtained. Can do.

  The metallized paste for the second surface metal layer 3b is in contact with the metal material (metal sheet or metal paste) for the metal member 3c.

  The metal member 3c is manufactured using the same material as the heat dissipation member 2. In the case where it is provided inside the insulating substrate 1, it can be manufactured using the same method as that for the heat dissipating member 2 described above. Moreover, when arrange | positioning on the surface of the insulation base | substrate 1, it can produce by the method similar to the 1st surface metal layer 3a and the 2nd surface metal layer 3b.

  From this, for example, when the ceramic green sheet for the insulating base 1 of the aluminum oxide sintered body is fired, by firing at a temperature higher than the melting point of Cu (about 1300 ° C. to 1400 ° C.), Cu and Cu contained in the metal sheet or metal paste that becomes the metal member 3c containing W melts, passes between the Mo metal particles of the second surface metal layer 3b, and diffuses to the surface of the second surface metal layer 3b. Accordingly, the surface of the second surface metal layer 3b can be made of Mo and containing Cu.

  As in the example shown in FIG. 2, when the metal member 3 c is provided inside the wiring substrate 10, the second surface metal is compared with the case where the metal member 3 c is provided on the surface of the wiring substrate 10. This is effective for providing a large layer 3b.

  Moreover, you may use the metal member 3c as the wiring conductor 4 like the example shown in FIG. In such a case, it is not necessary to secure a region for providing the metal member 3c, which is effective in reducing the size of the wiring board 10.

  As in the example shown in FIG. 4, when the metal member 3 c is provided on the surface of the wiring board 10, the metal member 3 c is provided on the surface of the wiring board 10 as compared with the case where the metal member 3 c is provided inside the wiring board 10. This is effective for increasing the degree of freedom of the internal wiring conductor 4.

When the metal member 3c is provided so as to contact the outer periphery of the second surface metal layer 3b and surround the second surface metal layer 3b as in the example shown in FIG. By increasing the amount of Cu diffusing into the surface metal layer 3b, the surface of the second surface metal layer 3b can be made to contain more Cu.

  Note that ceramic powder may be added to the metal paste for the first surface metal layer 3a and the second surface metal layer 3b in the same manner as the metal paste for the heat dissipation member 2. For example, when the insulating substrate 1 is made of an aluminum oxide sintered body, the first surface metal layer 3a and the second surface metal layer 3b preferably contain an aluminum oxide sintered body.

  Further, a metal plating layer of nickel, gold or the like is applied to the exposed surfaces of the first surface metal layer 3a and the second surface metal layer 3b by an electroless plating method as in the example shown in FIG. The The metal plating layer can be deposited starting from Cu exposed on the surfaces of the first surface metal layer 3a and the second surface metal layer 3b.

  In other words, the surface of the first surface metal layer 3a starts with Cu diffused from the heat dissipation member 2, and the surface of the second surface metal layer 3b starts with Cu diffused from the metal member 3c. Both the layer 3a and the second surface metal layer 3b are well coated with a plating layer.

When the metal plating layer having excellent corrosion resistance such as nickel or gold is applied to the exposed surfaces of the first surface metal layer 3a and the second surface metal layer 3b in this way, the first surface metal layer 3a and the second surface metal layer 3a Corrosion of the two-surface metal layer 3b can be suppressed. In addition, the electronic component 5 can be firmly bonded to the first surface metal layer 3a, and a bonding wire or an external circuit board can be firmly bonded to the second surface metal layer 3b. For example, a nickel plating layer having a thickness of about 1 to 10 μm and a gold plating layer having a thickness of about 0.1 to 3 μm are sequentially deposited on the exposed surfaces of the first surface metal layer 3a and the second surface metal layer 3b. .

  For the wiring conductor 4, for example, a metal material such as tungsten (W), molybdenum (Mo), manganese (Mn), or the like can be used. In addition, the wiring conductor 4 is electrically connected to the wiring conductor disposed between the insulating layers of the insulating base 1 and the second surface metal layer 3b positioned vertically through the insulating layer and the wiring layer conductors 4 between the insulating layers. There are through conductors connected to. For the wiring conductors arranged between the insulating layers, a metallized paste for the wiring conductor 4 is printed on the ceramic green sheet for the insulating substrate 1 by printing means such as a screen printing method, and fired together with the ceramic green sheet for the insulating substrate 1. Formed by. Further, the through conductor is formed with a through hole for the through conductor in the ceramic green sheet for the insulating substrate 1 by a die or punching process by punching or laser processing, and a metallized paste for the through conductor is formed in the through hole. Is formed by firing together with the ceramic green sheet for the insulating substrate 1.

  What is necessary is just to produce a metallized paste by the method similar to the metal paste for the above-mentioned heat radiating member 2. FIG. The metallized paste for the through conductor is adjusted to a viscosity higher than that of the metallized paste for the wiring conductor 4 so as to be suitable for filling by changing the kind and addition amount of the organic binder and the organic solvent.

  An electronic component 5 is mounted and mounted on the upper surface of the wiring board 10 so as to overlap the heat radiating member 2 in plan view. The electronic component 5 is a semiconductor element, a light-emitting element, or the like. The first surface metal layer 3a is joined. In addition, the electrode of the electronic component 5 and the second surface metal layer 3b are electrically connected via a connection member 6 such as a bonding wire mainly composed of Au.

When a light emitting element is mounted as the electronic component 5, the insulating substrate 1 has a cavity 8 as in the example shown in FIGS. 6 and 7, and reflects light emitted from the light emitting element on the inner wall surface of the cavity 8. A reflective layer 9 may be provided. The reflective layer 9 is formed by, for example, sequentially depositing a metallized layer and a plating layer on the inner wall surface of the cavity 8, or depositing a resin film or a metal film. A metal such as nickel, gold or silver is deposited on the exposed surface of the reflective layer 9.

  In the wiring substrate 10 of the present embodiment, the second surface metal layer 3b has a surface portion containing Cu, so that when the electroless plating layer is deposited, the second surface metal layer 3b starts from Cu. The plating layer can be satisfactorily applied to the surface of the film.

(Second Embodiment)
Next, a wiring board 10 according to a second embodiment of the present invention will be described with reference to FIG.

  In the wiring substrate 10 according to the second embodiment of the present invention, the portions different from the wiring substrate 10 according to the first embodiment described above are provided in contact with the second surface metal layer 3b as in the example shown in FIG. The metal body 7 is provided on the surface or inside of the insulating base 1, and the metal member 3 c made of CuW is in contact with the metal body 7. Other configurations are the same as those of the wiring board 10 according to the first embodiment.

  Also in the wiring substrate 10 of the present embodiment, the second surface metal layer 3b has a surface portion containing Cu, so that when the electroless plating layer is deposited, the second surface metal layer starts from Cu. A plating layer can be satisfactorily applied to the surface of 3b.

  The metal body 7 contains Mo as a main component, for example. Such a metal body 7 is manufactured in the same manner as the wiring conductor 4 described above. Thereby, Cu contained in the metal sheet or metal paste to be the metal member 3c containing Cu and W is melted and passes between the metal particles of Mo of the surface metal layer 3b and the metal body 7, and the surface metal layer 3b Diffuses to the surface. As a result, the surface of the surface metal layer 3b can be made of Mo and containing Cu.

  The wiring board 10 according to the second embodiment only needs to be provided with the metal member 3c in contact with the metal body 7 as in the example shown in FIG. In the example shown in FIG. 10, the wiring conductor 4 is used as the metal body 7. Further, as in the example illustrated in FIG. 10B, the metal member 3 c may be in contact with the plurality of wiring conductors 4 to electrically connect the wiring conductors 4. When the metal member 3c is provided inside the insulating base 1 as in the example shown in FIG. 10, the distance between the second surface metal layer 3b and the metal member 3c is preferably 0.2 mm or less.

  In addition, it is not limited to the example of said embodiment, A various change is possible. For example, a so-called castellation conductor in which a conductor is formed on the inner surface of a groove formed on the side surface of the wiring substrate 10 as the second surface metal layer 3b may be formed.

  Alternatively, the second surface metal layer 3b bonded to the external circuit board may be led out only to the upper surface side of the insulating base 1. In this case, a heat dissipator made of CuW, aluminum (Al) or the like and having excellent heat dissipation can be bonded to the lower surface of the wiring board 10. In such a case, if the material of the radiator on the lower surface of the wiring board 10 is CuW, it is possible to suppress the wiring board 10 from being greatly distorted due to a difference in thermal expansion.

Further, as in the example shown in FIGS. 8 and 9, a structure in which a plurality of electronic components 5 are mounted on the wiring board 10 may be used. In this case, a plurality of electronic components 5 may be mounted on one first surface metal layer 3 a, or a plurality of first surface metal layers 3 a may be disposed in the insulating substrate 1. When the plurality of first surface metal layers 3a are disposed, it is only necessary that the heat dissipating member 2 be disposed so as to be in contact with each of the plurality of first surface metal layers 3a. In this case, the heat of each electronic component 5 is radiated by each heat radiating member 2.

  A plurality of metal members 3c may be provided in contact with one second surface metal layer 3b. Such a configuration is effective for ensuring that the surface of the second surface metal layer 3b contains Cu evenly.

DESCRIPTION OF SYMBOLS 1 ... Insulating base | substrate 2 ... Heat dissipation member 3a ... 2nd surface metal layer 3b ... Surface metal layer 3c ... Metal member 4 ... Wiring conductor 5 ... Electronic component 6 ... Connection member 7 ... Metal body 8 ... Cavity 9 ... Reflective layer
10 ... Wiring board

Claims (2)

An insulating substrate;
A first surface metal layer provided on the surface of the insulating substrate, containing Mo as a main component, and having a surface portion containing Cu;
A heat dissipating member that is provided inside the insulating substrate, is in contact with the first surface metal layer, and contains Cu;
A second surface metal layer provided on the surface of the insulating substrate, containing Mo as a main component, and having a surface portion containing Cu;
A metal member which is provided on the surface or the inside of the insulating base, is in contact with the second surface metal layer, and contains Cu;
A wiring board comprising: a plating layer provided on each of the first and second surface metal layers. An insulating substrate;
A first surface metal layer provided on the surface of the insulating substrate, containing Mo as a main component, and having a surface portion containing Cu;
A heat dissipating member that is provided inside the insulating substrate, is in contact with the first surface metal layer, and contains Cu;
A second surface metal layer provided on the surface of the insulating substrate, containing Mo as a main component, and having a surface portion containing Cu;
A metal body provided in contact with the second surface metal layer;
A metal member that is provided on the surface or the inside of the insulating base, is in contact with the metal body, and contains Cu;
A wiring board comprising: a plating layer provided on each of the first and second surface metal layers.

Images