JP2007095727A - Ceramic substrate and electron device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable ceramic substrate where peeling and a crack are difficult to occur when a wiring layer and the like are formed on a substrate. <P>SOLUTION: The ceramic substrate is provided with a single ceramic layer 1 which is constituted of inorganic filler such as alumina and of glass with a low melting point in a remaining part, and in which a first region 1a and a second region 1b are formed in a plane direction. Young's modulus of ceramic which constitutes the first region 1a is made smaller than that of ceramic constituting the second region 1b. A wiring layer 2 formed of a metal having a prescribed pattern is formed on the first region 1a of the ceramic layer 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ceramic substrate and an electronic device using the same, and more particularly to a ceramic substrate on which an electronic component or the like is mounted on the surface and an electronic device using the same.

  Conventionally, as a substrate for an electronic device, a ceramic substrate in which the mechanical strength of the entire substrate is increased by forming a ceramic layer having high mechanical strength on the surface of the substrate is known (for example, Patent Documents 1 and 2). reference).

  FIG. 10 is a cross-sectional view for explaining the structure of a conventional ceramic substrate on which a ceramic layer having high mechanical strength is formed. With reference to FIG. 10, the structure of a conventional ceramic substrate having a ceramic layer with high mechanical strength formed on the surface will be described.

  As shown in FIG. 10, a conventional ceramic substrate 101 having a ceramic layer with high mechanical strength is laminated with a plurality of first ceramic layers 102a made of an inorganic filler such as alumina and the balance being low-melting glass. An inner layer 102 is formed.

  The upper surface and the lower surface of the inner layer 102 are made of an inorganic filler and a low-melting glass in a proportion different from that of the first ceramic layer 102a, and have higher mechanical strength such as bending strength and tensile strength than the first ceramic layer. A surface layer 103 in which a plurality of two ceramic layers 103a are stacked is formed. In this way, the conventional ceramic substrate 101 having a ceramic layer having a high mechanical strength formed on the surface is configured.

  FIG. 11 is a cross-sectional view for explaining a conventional process for producing a ceramic substrate having a ceramic layer having a high mechanical strength formed on the surface thereof. With reference to FIG. 11, a conventional process for manufacturing a ceramic substrate having a ceramic layer having a high mechanical strength formed on the surface thereof will be described.

  First, as shown in FIG. 11, the first ceramic green sheet 102p and the first ceramic green sheet 102p formed by mixing an inorganic filler, a low-melting glass, a solvent and a binder at a predetermined ratio and formed into a sheet shape are as follows. After forming the second ceramic green sheets 103p containing the inorganic filler and the low-melting glass at different ratios, a plurality of the first ceramic green sheets 102p are superposed, and the second ceramic green sheets 102p are stacked on the uppermost surface and the lowermost surface. Formed body 101p is formed by stacking a plurality of ceramic green sheets 103p.

  Next, the molded body 101p is sintered in the air or the like, thereby forming the ceramic substrate 101 having the surface layer 103 on the upper surface and the lower surface of the inner layer 102 as shown in FIG.

  Since the ceramic substrate 101 is laminated with the inner layer 102 and the surface layer 103 having higher mechanical strength than the inner layer 102, the mechanical strength can be increased as compared with the case of the inner layer 102 alone.

  Such a ceramic substrate can be used as a substrate for an electronic device such as a high-frequency filter or a composite module (see, for example, Patent Document 3).

  In this case, electronic components such as semiconductor devices and chip capacitors and wiring layers are formed on the surface of the ceramic substrate, and further, a wiring layer having a predetermined wiring pattern is formed inside the ceramic substrate.

The surface of the ceramic substrate and the internal wiring layer are formed by firing a metal paste such as silver paste into a predetermined wiring pattern on the upper surface of the ceramic green sheet that becomes the ceramic layer by firing, and the ceramic green on which these metal pastes are formed It can be formed by sintering a molded body on which sheets are stacked. Moreover, the electronic component surface-mounted on the ceramic substrate can be fixed by soldering on a wiring layer formed on the upper surface of the ceramic substrate.
JP-A-6-29664 JP-A-10-194828 JP 2003-171174 A

  However, even when the above-described conventional ceramic substrate 101 having a high mechanical strength ceramic layer is formed on the surface, when the wiring layer and the electronic component are formed on the surface and inside of the ceramic substrate 101, the first The heat shrink characteristics of the ceramic green sheet 102p and the second ceramic green sheet 103p are different from those of the metal paste that becomes the wiring layer and the solder that fixes the electronic component by firing. A stress acts locally on the surrounding first ceramic layer 102a and second ceramic layer 103a. As a result, cracks are likely to occur in the first ceramic layer 102a and the second ceramic layer 103a, and peeling may occur between the first ceramic layer 102a, the second ceramic layer 103a, the wiring layer, and the electronic component. There was a problem that the performance decreased.

The present invention has been made to solve the above problems,
One object of the present invention is to provide a highly reliable ceramic substrate that is less prone to peeling and cracking.

  Another object of the present invention is to provide a highly reliable electronic device.

  To achieve the above object, a ceramic substrate according to a first aspect of the present invention includes a ceramic layer in which a first region and a second region are formed in a planar direction, and constitutes a first region. The Young's modulus of the ceramic is smaller than the Young's modulus of the ceramic constituting the second region.

  In the ceramic substrate according to the first aspect, as described above, the first region and the second region made of ceramics having different Young's moduli in the plane direction of the ceramic layer, that is, in the direction perpendicular to the thickness direction of the ceramic layer. For example, by forming a wiring layer or the like on this ceramic layer, even if local stress acts on the ceramic layer around the wiring layer, for example, a region with a small Young's modulus is formed. This stress can be relieved when the region 1 is slightly deformed. Further, even when a local stress is applied to the ceramic layer around the wiring layer at the time of the falling collision of the ceramic substrate, the stress concentration can be similarly reduced. Thereby, since it can suppress that the whole ceramic substrate deform | transforms largely, peeling with a ceramic layer, a wiring layer, etc. and generation | occurrence | production of the crack in a ceramic layer can be suppressed. As a result, a highly reliable ceramic substrate can be obtained.

  In the present invention, the “ceramic substrate” is a broad concept including a substrate composed of a single ceramic layer and a substrate composed of a laminate including a plurality of ceramic layers. In the substrate, a wiring layer or the like may be further formed on the surface of the ceramic layer.

  In the ceramic substrate according to the first aspect, preferably, the composition of the ceramic constituting the first region and the ceramic constituting the second region are different. That is, at least one of the types and ratios of the ceramics included in the ceramic constituting the first region and the ceramic constituting the second region are different. If comprised in this way, the Young's modulus of the ceramic which comprises a 1st area | region and the ceramic which comprises a 2nd area | region can be easily varied. Thereby, the stress which acts locally on a ceramic substrate can be eased easily.

  In order to obtain a sufficient stress relaxation effect, the Young's modulus of the ceramic constituting the first region is preferably about 90% or less of the Young's modulus of the ceramic constituting the second region. It is done.

  The ceramic substrate according to the first aspect preferably further includes a wiring layer on the ceramic layer, and the wiring layer is formed on the first region. With this configuration, the local stress generated by the formation of the wiring layer mainly acts on the first region where the Young's modulus is small and is easily deformed. Therefore, the stress can be more effectively reduced. it can.

  An electronic device according to a second aspect of the present invention uses the ceramic substrate according to the first aspect. That is, this electronic device includes a ceramic layer in which a first region and a second region are formed in a planar direction, and the Young's modulus of the ceramic constituting the first region constitutes the second region. A ceramic substrate smaller than the Young's modulus of ceramic is used.

  In the electronic device according to the second aspect, as described above, the first region and the second region made of ceramics having different Young's moduli in the plane direction of the ceramic layer, that is, in the direction perpendicular to the thickness direction of the ceramic layer. For example, by forming a wiring layer or the like on this ceramic layer, even if local stress acts on the ceramic layer around the wiring layer, for example, a region with a small Young's modulus is formed. This stress can be relieved when the region 1 is slightly deformed. Further, even when a local stress is applied to the ceramic layer around the wiring layer at the time of the falling collision of the ceramic substrate, the stress concentration can be similarly reduced. Thereby, since it can suppress that the whole ceramic substrate deform | transforms largely, peeling with a ceramic layer, a wiring layer, etc. and generation | occurrence | production of the crack in a ceramic layer can be suppressed. As a result, a highly reliable electronic device can be obtained.

  In the electronic device according to the second aspect, the ceramic layer is preferably disposed on the outermost surface of the ceramic substrate. With this configuration, even when an electronic component or the like is formed on the surface of the ceramic substrate, even if a local stress acts on the periphery of the ceramic substrate around the electronic component, this stress can be easily obtained. Can be relaxed. As a result, the entire ceramic substrate after the surface mounting of the electronic component can be prevented from being greatly deformed, so that the separation of the ceramic layer from the wiring layer and the electronic component and the generation of cracks in the ceramic layer are suppressed. can do. As a result, an electronic device with higher reliability can be obtained.

  The “electronic device” in the present invention is a broad concept including, for example, an electronic circuit such as a high-frequency filter, a semiconductor chip and a capacitor or inductor that is a passive component, or a composite module component combining these.

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

(First embodiment)
FIG. 1 is a cross-sectional view for explaining the structure of a ceramic substrate according to a first embodiment of the present invention. A structure of a ceramic substrate according to a first embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the ceramic substrate according to the first embodiment of the present invention includes a single ceramic layer 1 composed of an inorganic filler such as alumina and the balance being low melting point glass.

In the ceramic layer 1, a first region 1a and a second region 1b are formed in a plane direction, that is, a direction perpendicular to the thickness direction of the ceramic layer 1, and constitutes the first region 1a. The ceramic to be contained contains alumina and amorphous glass (SiO ₂ —Al ₂ O ₃ —CaO—B ₂ O ₃ ) in a weight ratio of about 45: about 55 and has a Young's modulus of about 100 GPa to about 120 GPa. have. The ceramic constituting the second region 1b contains alumina and crystalline glass (CaO—MgO—SiO ₂ —ZnO ₂ ) in a weight ratio of about 35: about 65, and has a Young's modulus of about 140 GPa. have. As described above, the Young's modulus of the ceramic constituting the first region 1a is made smaller than the Young's modulus of the ceramic constituting the second region 1b.

  On the first region 1a of the ceramic layer 1, a wiring layer 2 made of metal having a predetermined pattern is formed. Thus, the ceramic substrate according to the first embodiment of the present invention is configured.

  2 to 5 are cross-sectional views for explaining a ceramic substrate manufacturing process according to the first embodiment of the present invention. A ceramic substrate manufacturing process according to the first embodiment of the present invention will be described with reference to FIGS.

[Production of ceramic green sheet material]
First, raw material powder containing an inorganic filler such as alumina and low melting point glass at the same ratio as the composition of the ceramic constituting the first region 1a of the ceramic layer 1 is prepared, and alcohol such as IPA is prepared in this raw material powder. A first ceramic mixture is formed by adding and mixing a solvent such as butyl acetate and thinner, a binder such as polyvinyl butyral (PVB), and a plasticizer.

  Similarly, a raw material powder containing an inorganic filler such as alumina and a glass having a low melting point in the same proportion as the composition of the ceramic constituting the second region 1b of the ceramic layer 1 is prepared, and an alcohol such as IPA is prepared in this raw material powder. A second ceramic mixture is formed by adding and mixing a solvent such as butyl acetate and thinner, a binder such as PVB, and a plasticizer.

[Production of ceramic green sheets]
Next, as shown in FIG. 2, a mask layer 51 made of a heat-dissipating resin such as polyalkylene glycol having an opening 51a or a copolymer containing polyalkylene glycol as a segment is formed on a substrate 50 having heat resistance. To do. The opening 51a can be formed by locally heating the mask layer 51 by laser light irradiation or the like.

  Next, as shown in FIG. 3, after filling the opening 51 a with the first ceramic mixture, the mask layer 51 is heated from about 150 ° C. to about 300 ° C. to thereby form the mask layer 51 from above the substrate 50. Remove. Thereby, pattern 1ap which consists of the 1st ceramic mixture is formed.

  Next, as shown in FIG. 4, a second ceramic mixture is applied on the substrate 10 from which the mask 51 has been removed to form a pattern 1 bp made of the second ceramic mixture, and then separated from the substrate 50. Thus, the ceramic green sheet 1p having the pattern 1ap made of the first ceramic mixture and the pattern 1bp made of the second ceramic mixture in the plane direction is formed.

[Production of wiring layer]
Next, as shown in FIG. 5, a metal paste 2p such as a silver paste having a predetermined pattern is formed on the upper surface of the ceramic green sheet 1p. The metal paste 2p having this predetermined pattern can be formed by screen printing or the like.

[Production of ceramic substrate]
Next, the ceramic green sheet 1p on which the metal paste 2p is formed is baked at about 800 ° C. to about 1000 ° C. in the atmosphere or the like, so that the first region 1a and the second region 1b are shown in FIG. A ceramic layer 1 is formed, and a wiring layer 2 having a predetermined pattern is formed on the first region 1 a of the ceramic layer 1. In this way, the ceramic substrate according to the first embodiment of the present invention is formed.

  In the first embodiment, as described above, the first region 1 a and the second region made of ceramics having different Young's moduli in the plane direction of the ceramic layer 1, that is, in the direction perpendicular to the thickness direction of the ceramic layer 1. Therefore, local stress acting on the ceramic layer 1 can be effectively relieved. That is, with respect to local stress acting on the ceramic layer 1 due to the formation of the wiring layer 2, the first region 1a having a small Young's modulus is slightly deformed, so that the entire ceramic substrate is prevented from being greatly deformed. Therefore, peeling between the ceramic layer 1 and the wiring layer 2 and the occurrence of cracks in the ceramic layer 1 can be suppressed. As a result, a highly reliable ceramic substrate can be obtained.

  In the first embodiment, the Young's modulus (about 100 GPa to about 120 GPa) of the ceramic constituting the first region 1a is about 71% to the Young's modulus (about 140 GPa) of the ceramic constituting the second region 1b. Since it has a value of about 86%, it is considered that local stress acting on the ceramic substrate can be sufficiently relaxed without significantly reducing the mechanical strength of the ceramic layer 1.

  In the first embodiment, since the wiring layer 2 is formed on the first region 1a having a small Young's modulus, local stress generated by the formation of the wiring layer 2 mainly has a small Young's modulus. It acts on the first region 1a that is easily deformed. Thereby, this stress can be relieved more effectively.

(Second Embodiment)
FIG. 6 is a cross-sectional view for explaining the structure of the electronic device according to the second embodiment of the present invention. The structure of the electronic device according to the second embodiment of the present invention will be described with reference to FIG.

In the electronic device according to the second embodiment of the present invention, the ceramic substrate 20 has a structure in which a plurality of ceramic layers 11 to 17 are laminated. Each ceramic layer 11 to 17 is formed with a first region 1a and a second region 1b in the planar direction, and the ceramic constituting the first region 1a is made of alumina and amorphous glass. (SiO ₂ —Al ₂ O ₃ —CaO—B ₂ O ₃ ) at a weight ratio of about 45: about 55 and has a Young's modulus of about 100 GPa to about 120 GPa. The ceramic constituting the second region 1b contains alumina and crystalline glass (CaO—MgO—SiO ₂ —ZnO ₂ ) in a weight ratio of about 35: about 65, and has a Young's modulus of about 140 GPa. have. As described above, the Young's modulus of the ceramic constituting the first region 1a is made smaller than the Young's modulus of the ceramic constituting the second region 1b.

  In addition, wiring layers 2 made of metal having a predetermined pattern are formed on at least one of the upper and lower surfaces of the first region 1a of the ceramic layers 11 to 17, respectively.

  Further, the ceramic layers 11 to 15 and 17 are formed with connection portions 2 a that connect the wiring layers 2 formed on the ceramic layers 11 to 17 in the thickness direction of the ceramic substrate 20.

  On the wiring layer 2 formed on the upper surface of the ceramic substrate 20, an electronic component 3 such as a chip capacitor or a semiconductor device is fixed by solder. The wiring layer 2 formed on the lower surface of the ceramic substrate 1 is used for connection with other electronic circuit boards. In this way, the electronic device according to the second embodiment of the present invention is configured.

  7 to 9 are cross-sectional views for explaining a manufacturing process of an electronic device according to the second embodiment of the present invention. With reference to FIGS. 7-9, the manufacturing process of the electronic device by 2nd Embodiment of this invention is demonstrated.

[Production of ceramic substrate]
First, as shown in FIG. 7, as in the first embodiment, the upper surfaces of ceramic green sheets 11p to 17p having a pattern 1ap made of the first ceramic mixture and a pattern 1bp made of the second ceramic mixture in the plane direction. A metal paste 2p having a predetermined pattern is formed on at least one of the upper and lower surfaces. The ceramic green sheets 11p to 17p are formed in the same manner as the ceramic green sheet 1p used in the first embodiment. Further, for the ceramic green sheets 11p to 15p and 17p, after forming a through hole 2ap opened by a punch or the like at a predetermined position, the metal paste 2p is formed on the ceramic green sheets 11p to 17p. At the same time, the metal paste 2p is filled into the through hole 2ap.

  Next, as shown in FIG. 8, a laminated body 20p in which the ceramic green sheets 11p to 17p are overlapped is formed. Then, by firing this laminated body 20p at about 800 ° C. to about 1000 ° C. in the atmosphere or the like, as shown in FIG. 9, the ceramic layers 11 to 17 composed of the first region 1a and the second region 1b. Is formed. By this firing, the wiring layer 2 having a predetermined pattern is formed on the first region 1a of the ceramic layer 1, and the wiring formed on the ceramic layers 11 to 17 in the thickness direction of the ceramic substrate 20 A connecting portion 2a connecting the layers 2 is formed.

[Surface mounting of electronic components]
Finally, as shown in FIG. 6, after the electronic component 3 such as a chip capacitor or a semiconductor device is bonded to the wiring layer 2 on the upper surface of the ceramic substrate 20 by a solder paste, the solder paste is heated and melted, The electronic component 3 is fixed on the ceramic substrate 20. Thus, the electronic device according to the second embodiment of the present invention is manufactured.

  In the second embodiment, as described above, a ceramic substrate in which a plurality of ceramic layers 11 to 17 in which the first region 1a and the second region 1b made of ceramics having different Young's moduli in the planar direction are formed are laminated. Since 20 is used, the local stress which acts on each layer 11-17 can be relieved effectively. That is, the first region 1a having a small Young's modulus is slightly deformed with respect to local stress acting on each of the layers 11 to 17 due to the formation of the wiring layer 2 on each of the layers 11 to 17, and thus the entire ceramic substrate 20 Can be prevented from being greatly deformed. As a result, peeling between the ceramic layers 11 to 17 and the wiring layer 2 and the like and generation of cracks in the ceramic layers 11 to 17 can be suppressed, so that a highly reliable ceramic substrate can be obtained.

  Further, in the second embodiment, since the ceramic layer 11 is disposed on the outermost surface (upper surface) of the ceramic substrate 20, the local area that acts on the periphery by the electronic component 3 that is surface-mounted on the upper surface of the ceramic substrate 20. Stress can be relieved. In the second embodiment, since the ceramic layer 17 is disposed on the outermost surface (lower surface) of the ceramic substrate 20, when the ceramic substrate 20 is fixed and connected to another electronic circuit substrate by soldering, soldering is performed. It is possible to relieve local stress acting on the periphery of the formed portion. Accordingly, it is possible to prevent the entire ceramic substrate 20 from being largely deformed after the electronic component 3 is surface-mounted or fixed and connected to another electronic circuit board or the like by soldering. Peeling from the wiring layer 2 and the electronic component 3 and the occurrence of cracks in the ceramic layers 11 to 17 can be suppressed. As a result, an electronic device with higher reliability can be obtained.

  In the second embodiment, in the ceramic layers 11 to 17 formed on the outermost surface of the ceramic substrate 20, the first region 1 a is also formed around the region where the electronic component 3 is disposed. Thereby, the stress which arises when the electronic component 3 is mounted can be relieved effectively.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and all modifications within the meaning and scope equivalent to the scope of claims for patent are included.

  For example, in the said embodiment, the ceramic layers 1 and 11-17 change the kind of glass and the mixing ratio of an inorganic filler and glass for the composition of the ceramic which comprises the 1st area | region 1a and the 2nd area | region 1b. However, the present invention is not limited to this, and at least one of the mixing ratio of the inorganic filler and glass, the type of inorganic filler, and the type of glass may be changed. For example, the Young's modulus can be reduced by reducing the composition ratio of the alumina constituting the first region 1a (weight ratio of alumina: crystallized glass) from about 35:65 to about 20:80. Can be small.

  Moreover, in the said embodiment, although the ceramic layers 1 and 11-17 contained the low melting glass, this invention is comprised not only by this but by the ceramic which consists of an inorganic filler which does not contain a low melting glass. May be. In this case, the first region 1a and the second region 1b are formed in the ceramic layers 1 and 11 to 17 by changing the type of inorganic filler such as oxide, nitride, boride and the mixing ratio thereof. Can be formed. As a result, a ceramic substrate having higher mechanical strength can be formed.

  Moreover, in the said embodiment, although the wiring layer 2 was formed on the 1st area | region 1a of the ceramic layers 1 and 11-17, this invention is not restricted to this, The 1st around the wiring layer 2 is 1st. You may arrange | position the 1st area | region 1a so that the area | region 1a may be distributed.

  Moreover, in the said embodiment, although the ceramic layers 1 and 11-17 had two area | regions, the 1st area | region 1a and the 2nd area | region 1b, this invention is not restricted to this, Each is a Young's modulus. You may have three or more area | regions comprised from different ceramics.

It is sectional drawing for demonstrating the structure of the ceramic substrate by 1st Embodiment of this invention. It is sectional drawing for demonstrating the 1st process of the manufacturing process of the ceramic substrate by 1st Embodiment of this invention. It is sectional drawing for demonstrating the 2nd process of the manufacturing process of the ceramic substrate by 1st Embodiment of this invention. It is sectional drawing for demonstrating the 3rd process of the manufacturing process of the ceramic substrate by 1st Embodiment of this invention. It is sectional drawing for demonstrating the 4th process of the manufacturing process of the ceramic substrate by 1st Embodiment of this invention. It is sectional drawing for demonstrating the structure of the electronic device by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the 1st process of the manufacturing process of the electronic device by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the 2nd process of the manufacturing process of the electronic device by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the 3rd process of the manufacturing process of the electronic device by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the structure of the conventional ceramic substrate in which the ceramic layer with a large mechanical strength was formed in the surface. It is sectional drawing for demonstrating one process of the manufacturing process of the conventional ceramic substrate in which the ceramic layer with large mechanical strength was formed in the surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic layer 1a 1st area | region 1b 2nd area | region 2 Wiring layer

Claims (5)

Comprising a ceramic layer in which a first region and a second region are formed in a planar direction;
The ceramic substrate in which the Young's modulus of the ceramic constituting the first region is smaller than the Young's modulus of the ceramic constituting the second region.   The ceramic substrate according to claim 1, wherein a composition of the ceramic constituting the first region and the ceramic constituting the second region are different. Further comprising a wiring layer on the ceramic layer,
The ceramic substrate according to claim 1, wherein the wiring layer is formed on the first region.   An electronic device using the ceramic substrate according to claim 1.   The electronic device according to claim 4, wherein the ceramic layer is disposed on an outermost surface of the ceramic substrate.

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