JP2009087965A - Multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer wiring board in which the deformation of the outer shape of the substrate is small and the unevenness of the main surface of the substrate is suppressed.
A multilayer wiring board according to the present invention includes a rectangular plate-like insulating substrate 1 in which a plurality of ceramic insulating layers 11, 12, 13, 14, and 15 are laminated, and a plurality of ceramic insulating layers 11, 12, 13, 14 and 15, the center of gravity of the insulating substrate 1 is located at the center of the insulating substrate 1 of one or a plurality of ceramic insulating layers disposed in the middle of the thickness of the insulating substrate 1 and within 20% or less of the thickness of the insulating substrate 1. The plate-like metal body 2 is embedded at different positions, and the corner metal bodies 3 having two side surfaces parallel to the two side surfaces forming the corners of the insulating base body 1 are embedded in the four corners of the insulating base body 1 when viewed from the stacking direction. To form.
[Selection] Figure 1

Description

  The present invention relates to a multilayer wiring board made of ceramics applicable to a power module board or the like.

  Conventionally, in order to reduce the resistance value of a wiring conductor in a multilayer wiring board and allow a large current to flow, the wiring conductor is formed on the insulating substrate constituting the multilayer wiring board by a thick copper film or electroless plating. It was done.

  However, in such a wiring conductor, the line width of the wiring pattern is limited by the area of the multilayer wiring board in order to increase the density of the wiring, and cannot be formed wider than a certain level. It was difficult to obtain a sufficiently thick wiring conductor at a low cost in a short time without adversely affecting the subsequent processes, and the reduction in resistance was not satisfied.

  Therefore, in order to reduce the resistance value of the wiring conductor and allow a large current to flow, a through groove (through hole) is formed in the ceramic grease sheet serving as an insulating layer constituting the multilayer wiring board, and the through groove is electrically connected. There has been proposed a method of forming a low-resistance wiring conductor by thickly filling and firing a wiring conductor paste made of a low-melting point metal such as copper or silver having a low resistance value (see Patent Document 1). Also, a method has been proposed in which a metal sheet having the same thickness as the ceramic green sheet is embedded in the through groove (through hole) of the ceramic green sheet instead of the wiring conductor paste (see Patent Document 2).

  However, in the multilayer wiring board manufactured by the method described in Patent Document 1 and Patent Document 2, the plate-like metal body formed by firing the wiring conductor paste or the metal sheet is in the center when viewed from the stacking direction. If it is arranged at a position deviated from the above, there is a problem that the shape is distorted and deformed in the plane direction. The problem of this deformation is a problem that can occur if a non-uniform wiring pattern is formed in the plane direction. However, when such a plate-shaped metal body is embedded, it becomes a particularly remarkable deformation. .

  Similarly, the plate-like metal body formed by firing the wiring conductor paste or the metal sheet is not a ceramic insulating layer disposed at substantially the center of the insulating base among a plurality of ceramic insulating layers, but is far from the center. If it is provided on the ceramic insulating layer close to the substrate surface, there is a problem that the substrate is partially warped.

On the other hand, a so-called dummy pattern that does not function as a wiring is formed by metallization in the vicinity of the periphery of the surface of the insulating layer to suppress deformation in the plane direction (see Patent Document 3). Since the dummy pattern formed by metallization has a thin thickness of about 15 μm per layer, it needs to be formed on the surface of each insulating layer in order to obtain a deformation suppressing effect. .
JP-A-5-21635 JP 2004-87990 A JP 2004-153025 A

  However, if the dummy pattern is formed so as to overlap the periphery of the surface of each insulating layer in this way in the stacking direction, the degree of freedom in designing the internal wiring is reduced and the pressure applied during pressure stacking is viewed from the stacking direction. Therefore, there is a problem that delamination is likely to occur near the boundary between the region where the dummy pattern is formed and the region where the dummy pattern is not formed.

  In addition, when the paste made of the same ceramic material as the ceramic green sheet is coated over the area where the dummy pattern is formed and the area where the dummy pattern is not formed in order to prevent the above delamination, the manufacturing cost increases and As the solvent permeates into the ceramic green sheet, there is a problem that the green sheet is elongated in a process where pressure such as lamination is applied, and the substrate is deformed.

  Furthermore, when the dummy patterns are provided by being gradually shifted in the stacking direction in order to prevent the delamination, there is a problem that the degree of freedom in designing the internal wiring is reduced.

  On the other hand, when the area where the dummy pattern is formed is to be discarded, there is a problem that the number of wafers is reduced by excessively increasing the substrate size.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multilayer wiring board in which the deformation of the outer shape of the board when viewed in plan is small and the main surface of the board is less uneven.

  The present invention relates to a rectangular plate-like insulating substrate in which five or more ceramic insulating layers are laminated, a wiring conductor formed inside the insulating substrate, and a position of the center of gravity when viewed from the lamination direction is the center of the insulating substrate. Differently, a plate-like metal body embedded through one or more ceramic insulating layers disposed in the middle of the thickness of the insulating base and within a range of 20% or less of the thickness of the insulating base; , Penetrating through one or more ceramic insulating layers disposed at the four corners of the insulating base as viewed from the stacking direction, at approximately the center of the thickness of the insulating base and within 20% or less of the thickness of the insulating base. And a corner metal body having two side surfaces parallel to the two side surfaces forming the corners of the insulating base.

  Here, the thickness of the plate-like metal body and the corner metal body is preferably 100 μm or more and 1000 μm or less. Further, the plate-like metal body and the corner metal body are embedded in at least one ceramic insulating layer disposed at a substantially center of the thickness of the insulating base and within a range of 20% or less of the thickness of the insulating base. It is preferable.

  According to the present invention, the corner metal bodies having two side surfaces parallel to the two side surfaces forming the corners of the insulating base are embedded in the four corners of the ceramic insulating layer forming the insulating base as viewed from the stacking direction. As a result, a force that uniformly shrinks the four corners of the ceramic green sheet for forming the insulating substrate in the firing process works, so that the position of the center of gravity is different from the center of the insulating substrate when viewed from the stacking direction. Even if the plate-like metal body is disposed on the substrate, it is possible to realize a multilayer wiring board with little deformation of the outer shape of the board when viewed in plan. In addition, since the plate-like metal body is provided in one or more ceramic insulating layers disposed in the middle of the thickness of the insulating base and within 20% or less of the thickness of the insulating base, Among them, the protrusions and depressions formed in the region facing the plate-like metal body can be reduced, and the flatness of the substrate main surface can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan perspective view showing an example of the multilayer wiring board of the present invention, and FIG. 2 is a sectional view taken along line XX of FIG.

  The multilayer wiring board of the present invention shown in FIGS. 1 and 2 includes a rectangular plate-like insulating substrate 1 in which a plurality of ceramic insulating layers 11, 12, 13, 14, 15 having substantially the same thickness are laminated, and an insulating substrate 1. Of the plurality of ceramic insulating layers 11, 12, 13, 14, 15 so that the position of the center of gravity is different from the center of the insulating substrate 1 when viewed from the stacking direction. A plate embedded through one or more ceramic insulating layers (only the ceramic insulating layer 13 in FIGS. 1 and 2) disposed at approximately the center of the thickness and within a range of 20% or less of the thickness of the insulating substrate 1 Of the plurality of ceramic insulating layers 11, 12, 13, 14, 15 at the center of the thickness of the insulating base 1 and at the thickness of the insulating base 1. Within 20% or less A corner having two side surfaces 3a parallel to the two side surfaces forming the corners of the insulating substrate 1, embedded through one or more ceramic insulating layers (only the ceramic insulating layer 13 in FIGS. 1 and 2). And a metal body 3.

The insulating base 1 is formed by laminating a plurality of ceramic insulating layers 11, 12, 13, 14, and 15 and forming a rectangular plate shape. As the ceramic for forming the ceramic insulating layers 11, 12, 13, 14, and 15, an alumina sintered body having excellent chemical resistance and inexpensive Al ₂ O ₃ as a main crystal phase is suitable. Here, the alumina sintered body to the _Al 2 _{O 3} as a main crystal phase, the powder X-ray diffraction, in which the diffraction peak of _Al 2 _{O 3} is detected as the main peak, crystal _Al 2 _{O 3} It is desirable to contain 50 volume% or more by volume ratio.

Such an alumina sintered body is made of, for example, Al ₂ O ₃ powder having an average particle size of 1.0 to 2.0 μm and a purity of 99% or more, Mn ₂ O ₃ having an average particle size of 1.0 to 2.0 μm, It can be obtained by firing a molded body to which at least one kind of sintering aid selected from the group of SiO ₂ , MgO, CaO, and SrO is added in a temperature range of 1300 to 1600 ° C. The addition amount of Al ₂ O ₃ other than the compositions, such as sintering aids, in order to obtain a dense body of the Al ₂ O ₃ as a main crystal, preferably 15 wt% or less, more desirably, 10 wt% The following is desirable. In particular, when the amount of a composition other than Al ₂ O ₃ such as a sintering aid is set to 15% by mass or less, most of the obtained insulating substrate 1 can be formed of Al ₂ O ₃ crystals. . These sintering aids are preferably added in an amount of 5% by mass or more, and more preferably 7% by mass or more in order to lower the firing temperature.

The ceramic for forming the ceramic insulating layers 11, 12, 13, 14, 15 is not limited to the Al ₂ O ₃ sintered body, and for example, a wiring conductor having a low melting point and low resistance is used. Glass ceramics that can be fired at a low temperature of less than 1000 ° C. may be used. Further, a ceramic sintered body mainly composed of magnesium oxide, zirconium oxide, aluminum nitride, silicon nitride, mullite, cordierite, etc. It may be used.

  Of the plurality of ceramic insulating layers 11, 12, 13, 14, and 15, one or more layers of ceramic insulation are arranged in the center of the thickness of the insulating base 1 and within 20% or less of the thickness of the insulating base 1. The plate-like metal body 2 is embedded so as to penetrate through the layers (the ceramic insulating layer 13 in FIGS. 1 and 2) so that the position of the center of gravity is different from the center of the insulating substrate 1 when viewed from the stacking direction. Here, the plate-like metal body 2 has a uniform thickness per layer, and the position of the center of gravity viewed from the stacking direction can be specified by the area of each layer viewed from the stacking direction. When a plurality of plate-like metal bodies 2 are embedded, it is determined whether or not the center of gravity of a virtual figure drawn by connecting the centers of gravity of the respective plate-like metal bodies 2 is different from the center of the insulating substrate 1. . In addition, this plate-shaped metal body 2 can be used as wiring, for example.

  Here, among the plurality of ceramic insulating layers, the ceramic insulating layer disposed at approximately the center of the thickness of the insulating substrate and within 20% or less of the thickness of the insulating substrate is a thickness of 100 μm per ceramic insulating layer. Therefore, for example, when a plurality of ceramic insulating layers have a five-layer structure, the third layer from the top (ceramic insulating layer 13 shown in FIG. 1) is used, and in the case of a six-layer structure, three layers from the top. This refers to the 4th or 4th layer. In the case of the 7-layer structure, it refers to the 3rd or 4th layer from the top or the 4th or 5th layer from the top. In the case of a 9-layer structure, it refers to the 4th or 5th layer or the 5th or 6th layer from the top. In the case of a 10-layer structure, the 5th layer from the top or It means the 6th layer. And as a number of the ceramic insulating layers which comprise an insulating base | substrate, it is required to provide five or more layers from the relationship with thickness per layer.

  The plate-like metal body 2 is composed of one or more ceramic insulating layers (in FIG. 1 and FIG. 2, ceramic insulating layers) which are arranged in the approximate center of the thickness of the insulating base 1 and within a range of 20% or less of the thickness of the insulating base 1. As will be described later, a through hole is formed in a portion of the ceramic green sheet for forming the ceramic insulating layer 13 and a metal sheet piece is embedded in the through hole portion. Thus, it is preferable to form. By embedding the plate-like metal body 2 in the ceramic insulating layer 13 at such a position, irregularities formed on the upper and lower main surfaces of the multilayer wiring board (insulating base 1) can be suppressed.

  The plate-like metal body 2 is embedded so as to penetrate through one or a plurality of ceramic insulating layers disposed in the approximate center of the thickness of the insulating base 1 and within a range of 20% or less of the thickness of the insulating base 1. For example, when the ceramic insulating layer to be laminated has a five-layer structure, the third layer from the top, and when the ceramic insulating layer to be laminated has a six-layer structure, the third or fourth layer from the top, 7 In the case of a layer structure, the third or fourth layer from the top or the fourth or fifth layer from the top, in the case of an eight-layer structure, the fourth or fifth layer from the top, and in the case of a nine-layer structure, the top In the case of the 10-layer structure, it is only necessary to penetrate through either one or both of the 5th layer and the 6th layer from the top to the 4th layer, the 5th layer, the 5th layer, or the 6th layer. .

  The plate-like metal body 2 can be formed of a metal mainly composed of Cu, Cu-W, Ag, Al, W, and Mo or an alloy thereof, and can pass a large current when used as a wiring. . Examples of the shape of the plate-shaped metal body 2 include a rectangular parallelepiped shape and a disk shape. In the case of a rectangular parallelepiped shape, the volume of the plate-shaped metal body 2 can be maximized and a large current can be realized. In the case of a disk shape, it is effective in preventing stress concentration and providing high reliability. Further, a multi-stage shape may be used, and in this case, since the contact area with the insulating base 1 is large, the bonding reliability with the insulating base 1 can be improved. In the case of this multi-stage shape, the plate-like metal body 2 is obtained by penetrating and forming a plurality of ceramic insulating layers disposed almost at the center of the insulating base 1.

  Further, since the plate-like metal body 2 is used for a multilayer wiring board, it is rarely arranged at the center of the insulating substrate 1 as viewed from the lamination direction depending on the designed wiring pattern or the like, and the position of the center of gravity is The insulating substrate 1 is disposed at a position different from the center (a position deviated from the center). And when manufacturing a multilayer wiring board, since the shrinkage | contraction behavior of the ceramic green sheet used as the ceramic insulating layer 13 and the metal sheet piece used as the plate-shaped metal body 2 differs, it is insulated at the time of baking shrinkage by the influence of such arrangement | positioning. The four corners of the base 1 are uniformly shrunk so that the insulating base 1 is not formed, and the outer shape of the insulating base 1 cannot be formed within a predetermined dimension.

  Therefore, at the four corners of one or a plurality of ceramic insulating layers (ceramic insulating layer 13 in FIGS. 1 and 2), which is disposed at approximately the center of the thickness of the insulating substrate 1 and within 20% or less of the thickness of the insulating substrate 1. The corner metal body 3 having two side surfaces parallel to the two side surfaces forming the corners of the insulating substrate 1 is embedded.

  Thus, by providing the corner metal bodies 3 having two side surfaces parallel to the two side surfaces forming the corners of the insulating base 1 at the four corners of the ceramic insulating layer 13, the ceramic green that becomes the ceramic insulating layer during firing shrinkage is provided. Since the shrinkage of the four corners of the sheet can be restricted, the outer shape of the substrate can be prevented from being greatly deformed after firing.

  Here, the ceramic insulating layer disposed at approximately the center of the thickness of the insulating base 1 and within 20% or less of the thickness of the insulating base 1 has a thickness per layer of the ceramic insulating layer of 100 μm to 200 μm. For example, when a plurality of ceramic insulating layers have a five-layer structure, it refers to the third layer from the top (ceramic insulating layer 13 shown in FIG. 1), and in the case of a six-layer structure, the third or fourth layer from the top. In the case of a 7-layer structure, the 3rd or 4th layer from the top or the 4th or 5th layer from the top. In the case of an 8 layer structure, the 4th or 5th layer from the top In the case of a 9-layer structure, the 4th or 5th layer or the 5th or 6th layer from the top. In the case of a 10-layer structure, the 5th or 6th layer from the top. Say.

  The corner metal body 3 is also embedded so as to penetrate the ceramic insulating layer (ceramic insulating layer 13) similarly to the plate-like metal body 2, and the ceramic for forming the ceramic insulating layer 13 is formed in the same manner as the plate-like metal body 2. It is preferable that a through hole is formed in a part of the green sheet, and a metal sheet piece is embedded in the through hole portion. By embedding the corner metal body 3 in the ceramic insulating layer 13 at such a position, unevenness formed on the upper and lower main surfaces of the multilayer wiring board (insulating base 1) can be suppressed.

  The corner metal body 3 is embedded so as to penetrate one layer or a plurality of ceramic insulating layers disposed in the approximate center of the thickness of the insulating base 1 and within a range of 20% or less of the thickness of the insulating base 1. For example, when the ceramic insulating layer to be laminated has a five-layer structure, the third layer from the top, and when the ceramic insulating layer to be laminated has a six-layer structure, the third layer or the fourth layer from the top has seven layers. 3rd or 4th layer or 4th or 5th layer from the top in the case of structure, 4th or 5th layer from the top in the case of 8 layer structure, or from the top in the case of 9 layer structure In the case of a 10-layer structure, the fourth layer, the fifth layer, the fifth layer, or the sixth layer may be formed so as to penetrate either one or both of the fifth layer and the sixth layer from the top.

  The corner metal body 3 is formed of a metal mainly composed of Cu, Cu-W, Ag, Al, W, and Mo or an alloy thereof in the same manner as the plate-like metal body 2 when it functions as a part of the wiring. However, other metal bodies may be used if not used as part of the wiring. However, it is preferable to use the same type of metal or alloy as the plate-like metal body 2 in terms of the ease of designing the multilayer wiring board.

  It is important that the corner metal body 3 has two side surfaces 3a parallel to the two side surfaces forming the corners of the insulating base 1. Since the corner metal bodies 3 having such a shape are embedded in the four corners of the insulating substrate 1, the force for uniformly shrinking the four corners of the ceramic green sheet for forming the insulating substrate 1 in the firing process. Therefore, a multilayer wiring board with less deformation in the plane direction due to the influence of the position of the center of gravity of the plate-like metal body 2 being arranged at a position different from the center of the insulating base 1 can be obtained. Here, the corner metal body 3 shown in FIG. 2 is formed in an L-shape when viewed from the stacking direction, and such a shape is the degree of freedom in designing other wiring patterns (wiring conductors 8). Although it is preferable from the point of view, it is only necessary to have two side surfaces along the two side surfaces forming the corners of the insulating base 1 from the viewpoint of suppressing deformation. It does not matter if you do it.

  The length of each side surface 3a (the length of one side of the corner metal body 3 along one side of the insulating base body 1) parallel to the two side surfaces forming the corners of the insulating base body 1 is determined as follows. The length of one side is preferably 25% or more, and the two corner metal bodies 3 are combined to form a length of 50% or more per side of the insulating substrate 1. It is preferable. Thus, the length of one side (side parallel to the side surface of the insulating substrate 1 when viewed from the stacking direction) of the corner metal body 3 constituting the side surface 3a parallel to the side surface of the insulating substrate 1 is opposed to each other. By setting it to 25% or more of the length of one side of the insulating substrate 1, the effect of suppressing deformation is enhanced.

  In addition, the area of each piece of the corner metal body 3 viewed from the stacking direction is an insulating base viewed from the stacking direction as a range that has a deformation suppressing effect when not functioning as a wiring and has a degree of freedom in designing other wiring patterns. A ratio of 2.5% to 12.5% with respect to the area of 1 is preferable, and when it also serves as a wiring, the ratio may be up to 22.5% as an upper limit.

  In addition, the thickness of the plate-like metal body 2 and the corner metal body 3 is 100 μm or more and 1000 μm or less as a range in which the unevenness formed on the upper and lower surfaces of the insulating substrate 1 is suppressed and the deformation suppressing effect in the planar direction is high. Is preferred. From the viewpoint of the same effect, the total thickness of the ceramic insulating layers 11 and 12 stacked on the upper side of the plate-shaped metal body 2 and the plurality of ceramic insulating layers 14 and 15 stacked on the lower side is respectively set to the plate-shaped metal body. The thickness of the ceramic insulating layers 11 and 12 stacked on the upper side of the corner metal body 3 and the plurality of ceramic insulating layers 14 and 15 stacked on the lower side are preferably 2 to 3 times the thickness of 2, respectively. The thickness of the corner metal body 3 is preferably 2 to 3 times.

  Further, from the viewpoint of suppressing deformation of the outer shape of the substrate and unevenness of the main surface of the substrate, at least one ceramic insulating layer disposed approximately in the center of the thickness of the insulating base 1 and within a range of 20% or less of the thickness of the insulating base 1 Preferably, the plate-like metal body 2 and the corner metal body 3 are formed so as to be embedded.

  Next, the manufacturing method of the multilayer wiring board of this invention is demonstrated concretely.

  FIG. 3 is an explanatory view of a method for manufacturing a multilayer wiring board according to the present invention. FIG. 3 shows a ceramic green sheet 4 that becomes a ceramic insulating layer after firing, and a plate-like metal body 2 and a corner metal body 3 after firing. A metal sheet 5 is shown. In addition, 6 shown to a figure is a metal mold | die.

First, as described below, the ceramic green sheet 4, the metal sheet 5, and the conductor paste are prepared.

  The ceramic green sheet 4 is formed into a sheet shape from a ceramic slurry prepared by mixing ceramic powder, an organic resin, and a solvent at a predetermined ratio by a conventionally known doctor blade method or the like.

  Further, the metal sheet 5 is also formed into a sheet shape by a doctor blade method or the like from a metal slurry prepared by mixing metal powder, an organic resin, and a solvent at a predetermined ratio. The metal slurry may contain ceramic powder as necessary.

  The average particle size of the ceramic powder forming the ceramic green sheet 4 and the metal powder forming the metal sheet 5 is preferably about 0.01 to 10 μm, and in particular, the powder in the range of 1 to 5 μm is handled and sintered. Excellent binding.

  A through hole is formed in the ceramic green sheet 4 by a micro drill or a laser, and the conductive paste is filled into the through hole by a method such as printing, and the conductor paste is printed on the surface of the ceramic green sheet 4 to form the wiring conductor 8. Form.

  Next, a method of embedding a part of the metal sheet 5 that becomes the plate-like metal body and / or a part of the metal sheet 5 that becomes the corner metal body 3 in the ceramic green sheet 4 that becomes the ceramic insulating layer will be described.

  After the through hole 41 is formed at a predetermined position of the ceramic green sheet 4, the metal sheet 5 is laminated on the ceramic green sheet 4 having the through hole 41, and the portion of the ceramic green sheet 4 where the through hole 41 is formed is the metal sheet. By pressing from the 5 side (upper side in FIG. 3), a part of the metal sheet 5 is embedded in the through hole 41, and then the remaining metal sheet 5 is removed, whereby the ceramic green sheet 4 and the metal sheet piece 5a are removed. The composite sheet 7 is formed by integrating. At this time, it is desirable that the ceramic green sheet 4 and the metal sheet piece 5a have substantially the same thickness.

  In addition, about the formation method (the embedding method of the metal sheet piece 5 to the through-hole 41 of the ceramic green sheet 4) of the composite sheet 7, after forming the through-hole 41 in the ceramic green sheet 4 as shown in FIG. The metal sheet 5 is stuck on the ceramic green sheet 4 and the metal sheet 5 is stuck on the ceramic green sheet 4 as shown in FIG. A method of embedding a part of the metal sheet 5 in the through hole 41 by pressing from the metal sheet 5 side (upper side in FIG. 4) in the combined state may be used.

  Separately from the composite sheet 7, a ceramic green sheet 4 printed with a conductor paste on the main surface so as to have a predetermined wiring pattern and a through hole penetrating the upper and lower main surfaces are formed, and the conductor paste is formed in the through hole. A ceramic green sheet 4 or the like having a through-hole conductor filled therein is prepared.

  Then, these ceramic green sheets 4 and the composite sheet 7 are laminated to form a green sheet laminate having five or more layers. At this time, the composite sheet 7 in which the metal sheet piece 5a to be the plate-like metal body 2 and the metal sheet piece 5a to be the corner metal body 3 are embedded is substantially at the center of the thickness of the green sheet laminate, It should be arranged in an area of 20% or less. However, the metal sheet piece 5a to be the plate-like metal body 2 and the metal sheet piece 5a to be the corner metal body 3 are as thick as possible in the center of the thickness of the green sheet laminate from the viewpoint of suppressing warpage and surface irregularities in the firing step described later. It is preferable to design so that it may be arrange | positioned.

Further, if the metal sheet piece 5a to be the plate-like metal body 2 and the metal sheet piece 5a to be the corner metal body 3 are embedded in the same ceramic green sheet 4, the number of molds required for embedding is reduced. Therefore, the work process can be simplified and the cost can be reduced, which is preferable.

  Next, the produced green sheet laminate is fired in an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere, whereby a multilayer wiring board can be produced.

  Here, even when there is almost no gap between the ceramic green sheet 4 and the metal sheet piece 5a, a gap is formed by the difference in contraction between the ceramic green sheet 4 and the metal sheet piece 5a when the composite sheet 7 is fired. Sometimes. Thus, when there is a gap between each other, moisture and oxygen reach the inside through the gap, oxidize the metal layer, promote migration of the wiring layer, discoloration of ceramics forming the insulating base 1, Although corrosion will be caused, such problems can be solved by embedding the plate-like metal body 2 and the corner metal body 3 in the insulating substrate 1 as in the present invention.

  A multilayer wiring board constituting the power module substrate was produced.

As a raw material powder for a ceramic green sheet that becomes an insulating base after firing, 90% by mass of Al ₂ O ₃ powder having a purity of 99% or more and an average particle size of 1.5 μm, SiO having a purity of 99% or more and an average particle size of 1.0 μm 5% by mass of ₂ powders, 5% by mass of Mn ₂ O ₃ powder with a purity of 99% or more and an average particle size of 1.5 μm, and an acrylic binder as a molding organic resin (binder) and toluene as a solvent A slurry was prepared. Using this slurry, a ceramic green sheet having a thickness of 200 μm was prepared by a doctor blade method. The external shape of the ceramic green sheet after firing was designed to be a rectangle with a length of 80 mm and a width of 50 mm.

  Further, as a raw material powder of a metal sheet that becomes a plate-like metal body and a corner metal body after firing, 30% by mass of Cu powder having an average particle size of 2.0 μm and 70% by mass of W powder having an average particle size of 2.0 μm are mixed. Then, an acrylic binder and toluene were added as a forming organic resin (binder) as a solvent, and a metal slurry was prepared in the same manner as the ceramic green sheet 4. And the metal sheet 5 of thickness 200micrometer was produced with the doctor blade method using this metal slurry.

  Further, conductor is obtained by mixing 30% by mass of Cu powder having an average particle size of 2.0 μm and 70% by mass of W powder having an average particle size of 2.0 μm using an acrylic binder and acetone as a solvent and removing the solvent by heating under reduced pressure or the like. A paste was prepared.

  Then, the ceramic green sheet is punched to form a via hole having a diameter of 100 μm. The via hole is filled with a conductive paste by a screen printing method, and a wiring pattern is printed on the surface of the ceramic green sheet. did.

  Next, a through hole was formed at a predetermined location of the ceramic green sheet, and a metal sheet having the same thickness as the ceramic green sheet was embedded in the through hole to produce a composite sheet in which the ceramic green sheet and the metal sheet were integrated. At this time, as shown in FIG. 2, the shape of the metal sheet as the corner metal body inserted into the through hole formed in the vicinity of the corner portion of the ceramic green sheet forms the corner of the ceramic green sheet as viewed from the stacking direction. An L-shape having two side surfaces along the two side surfaces is formed, and the length of the portion along the two side surfaces forming the corner of the ceramic green sheet is 22 mm and the width is 10 mm. In addition, the shape of the metal sheet, which is a plate-like metal body inserted into the through hole formed so that the center of gravity is located at a position different from the center of the ceramic green sheet when viewed from the stacking direction, is the length when viewed from the stacking direction. The rectangular shape was 45 mm and the width was 15 mm, and two were arranged in parallel at a predetermined interval.

  The thus produced ceramic green sheet and composite sheet were combined as shown in Table 1 and laminated and pressed to produce a laminate.

  Thereafter, the substrate was baked at a maximum temperature of 1300 ° C. for 2 hours in a mixed atmosphere of nitrogen and hydrogen to produce a multilayer wiring board. Sample No. Except for 8, a plate-like metal body and a corner metal body were formed in the same ceramic insulating layer. In addition, as a comparative example, a sample having three corner metal bodies as shown in FIG.

  And about the produced multilayer wiring board (each sample), the two main surfaces of a multilayer wiring board are measured with a non-contact type three-dimensional measuring device (made by Combs Co., Ltd.), and the side which has a convex part partially is measured. The main surface of the substrate was the upper surface, and the height of the convex portion on this upper surface was used as the evaluation value. That is, the unevenness on the main surface of the substrate is caused by the embedded position of the plate-like metal body or the corner metal body in the thickness direction of the insulating base, and when there is a partial projection on one main surface of the substrate, the other substrate This is because a concave portion is formed in a region of the main surface that faces the convex portion, and the evaluation can be performed by checking one of the main surfaces of the substrate. In the measurement of the main surface of the substrate, the wiring formed on the main surface of the substrate was removed, or the wiring that was not previously formed on the main surface of the substrate was used.

  As for the deformation of the outer shape viewed from the stacking direction, as shown in FIG. 6, XY coordinates with the origin at the tip of each corner of the multilayer wiring board (insulating base) designed in advance are provided, and after firing The amount of misalignment at each corner tip of the multilayer wiring board was measured. For example, when the corner tip of the lower left corner is at the upper left in the XY coordinates, the X-direction shift is shifted to the minus side, and the Y-direction shift is shifted to the plus side. In this way, the deformation of the four corners of the insulating substrate was measured.

The results are shown in Table 1. Note that the convexity of the upper surface of the multilayer wiring board is 100 μm or less as a non-defective product judgment standard, and for the deformation of the outer shape, each corner tip of the multilayer wiring board is within ± 100 μm or less with respect to the XY coordinate. did.

  Sample No. in which the metal plate and the corner metal are embedded in the first ceramic insulating layer. Sample No. 1 and 2, and the metal plate-like body and the corner metal body are provided in a ceramic insulating layer other than the ceramic insulating layer disposed in the center of the thickness of the insulating base. In 3, 5, and 10, large protrusions were formed on the upper surface of the multilayer wiring board.

  Sample No. with no corner metal embedded in the four corners of the ceramic insulating layer. In Nos. 1, 9, and 13, since there is no corner metal body in the upper right corner of the multilayer wiring board in FIG. 5, the lower left and upper left corners of the fired multilayer wiring board were greatly deformed.

  On the other hand, the number of laminated ceramic insulating layers is 5 or more, and is disposed on one or more ceramic insulating layers arranged in the range of approximately the center of the thickness of the insulating base and 20% or less of the thickness of the insulating base. Sample No. of the present invention having a metal body and a corner metal body. In 4, 6, 7, 8, 11, 12, and 14, the convex amount of the upper surface of the multilayer wiring board is 100 μm or less, and the deformation of the outer shape is such that each corner tip of the multilayer wiring board is ± with respect to the XY coordinates. It could be 100 μm or less.

It is a plane perspective view which shows an example of the multilayer wiring board of this invention. It is the XX sectional view taken on the line of FIG. It is the schematic for demonstrating the manufacturing method of the multilayer wiring board of this invention. It is the schematic for demonstrating the other manufacturing method of the multilayer wiring board of this invention. As a comparative example, it is a plane perspective view of a multilayer wiring board having a configuration excluding one corner metal body of the four corners of the configuration of the present invention. It is a conceptual diagram for measuring the deformation amount of the external shape of a multilayer wiring board.

Explanation of symbols

1: Insulating substrate 2: Plate-shaped metal body 3: Corner metal body 3a: Side surface 4: Ceramic green sheet 5: Metal sheet 5a: Metal sheet piece 6: Mold 7: Composite sheet 8: Wiring conductor

Claims (3)

A rectangular plate-like insulating substrate in which five or more ceramic insulating layers are laminated;
A wiring conductor formed inside the insulating substrate;
A single layer or a plurality of layers arranged at a substantially center of the thickness of the insulating base and within a range of 20% or less of the thickness of the insulating base so that the position of the center of gravity is different from the center of the insulating base as viewed from the stacking direction. A plate-like metal body embedded through the ceramic insulating layer;
As viewed from the stacking direction, through one or a plurality of ceramic insulating layers disposed at the four corners of the insulating base, approximately in the center of the thickness of the insulating base and within a range of 20% or less of the thickness of the insulating base. A multilayer wiring board, comprising: a corner metal body having two side surfaces parallel to two side surfaces forming a corner portion of the insulating base. 2. The multilayer wiring board according to claim 1, wherein a thickness of the plate-like metal body and the corner metal body is 100 μm or more and 1000 μm or less. The plate-like metal body and the corner metal body are embedded in at least one ceramic insulating layer disposed in the middle of the thickness of the insulating base and within 20% or less of the thickness of the insulating base. The multilayer wiring board according to claim 1 or 2, characterized in that

Images