Multilayer substrate

Abstract

The present invention provides a multilayer substrate which is not susceptible to cracking or separation at a connection part of an electrode that is provided on a ceramic layer and an interlayer connection conductor that is provided in a thermoplastic resin layer even in cases where a thermal stress occurs. A multilayer substrate (1) according to the present invention is provided with: a first thermoplastic resin layer (21) which has a first main surface (21a) and a second main surface (21b) that is opposite to the first main surface (21a), and which has a via hole (21h) that penetrates therethrough from the first main surface (21a) to the second main surface (21b); a ceramic layer (11) which is arranged so as to be in contact with the first main surface (21a); and a second thermoplastic resin layer (22) which is arranged so as to be in contact with the second main surface (21b). A first electrode (31) is formed on a main surface of the ceramic layer (11) which is in contact with the first main surface (21a); a protective layer (40) is additionally formed on the main surface of the ceramic layer (11) so as to cover at least a part of the outline of the first electrode (31); a second electrode (32) is formed on a main surface of the second thermoplastic resin layer (22) which is in contact with the second main surface (21b); an interlayer connection conductor (50), which connects the first electrode (31) and the second electrode (32) to each other, is arranged in the via hole (21h); and an intermetallic compound (61) is formed between the interlayer connection conductor (50) and the first electrode (31).

Description

Multilayer substrate

[0001] The present invention relates to a laminated substrate.

[0002] Conventionally, module components using multilayer substrates with built-in passive elements have been put to practical use. For example, a well-known DC-DC converter module is formed by mounting a switching IC (integrated circuit) chip and a chip capacitor on a multilayer substrate with a built-in coil as the passive element.

[0003] A known multilayer substrate used in such module components is one in which ceramic substrates are stacked. In a multilayer substrate in which ceramic substrates are stacked, warping of the ceramic substrates may occur. To solve this problem, Patent Document 1 discloses a laminated substrate (module component) in which a substrate (thermoplastic resin layer) made of a thermoplastic resin is stacked on a multilayer substrate in which ceramic substrates are stacked.

[0004] That is, Patent Document 1 discloses a ceramic multilayer substrate having a passive element built in and having a first terminal electrode and a second terminal electrode connected to the passive element on one main surface and the other main surface, respectively; a first thermoplastic resin layer provided on the one main surface of the ceramic multilayer substrate and having a first wiring connected to the first terminal electrode and a first land for mounting a surface-mounted component; a second thermoplastic resin layer provided on the other main surface of the ceramic multilayer substrate and having a second wiring connected to the second terminal electrode and a second land serving as a connection terminal to a motherboard; and a thermoplastic resin layer mounted on the first thermoplastic resin layer and having a first thermoplastic resin layer. and a surface-mounted component connected to the first land of a ceramic multilayer substrate, wherein the first thermoplastic resin layer and the second thermoplastic resin layer have different thicknesses, the first thermoplastic resin layer being thicker than the second thermoplastic resin layer, the ceramic multilayer substrate being a substrate made of a non-glass-based low-temperature co-fired ceramic material, and the first terminal electrode of the ceramic multilayer substrate and the interlayer conductor provided in the first thermoplastic resin layer, and the second terminal electrode of the ceramic multilayer substrate and the interlayer conductor provided in the second thermoplastic resin layer are bonded by liquid phase diffusion bonding.

[0005] In Patent Document 1, terminal electrodes provided on a ceramic multilayer substrate and interlayer conductors provided on a thermoplastic resin layer are bonded by transient liquid phase diffusion bonding.

[0006] Patent Document 2 discloses an interlayer connection conductor connected to a conductor wiring layer, and discloses that an intermetallic compound layer containing an intermetallic compound is formed between the conductor wiring layer and the interlayer connection conductor. The intermetallic compound layer is generated when a metal such as Sn or an Sn alloy constituting the interlayer connection conductor melts upon heating and reacts with a metal (e.g., Cu) constituting the conductor wiring layer. That is, the intermetallic compound layer is generated during liquid phase diffusion bonding.

[0007] Patent No. 6819668 International Publication No. 2019 / 003729

[0008] In the laminated substrate (module component) described in Patent Document 1, an intermetallic compound layer such as that disclosed in Patent Document 2 is also formed between an electrode (terminal electrode) provided on a ceramic layer and an interlayer connection conductor (interlayer conductor) provided on a thermoplastic resin layer.

[0009] Because the linear thermal expansion coefficient of the ceramic layer differs from the linear thermal expansion coefficient of the thermoplastic resin layer, when heat is applied to the laminated substrate, thermal stress occurs between the ceramic layer and the thermoplastic resin layer. Such thermal stress is likely to be exerted on the interlayer connection conductor located at the boundary between the ceramic layer and the thermoplastic resin layer. Thermal stress is particularly likely to be exerted on the connection portion of the interlayer connection conductor with the electrode provided on the ceramic layer. As described above, an intermetallic compound layer is formed between the electrode provided on the ceramic layer and the interlayer connection conductor provided on the thermoplastic resin layer. Since the intermetallic compound has low ductility, it is difficult for the intermetallic compound to absorb thermal stress. Therefore, when the interlayer connection conductor is subjected to the thermal stress, cracks and peeling are likely to occur, originating from the intermetallic compound or the surrounding interlayer connection conductor.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a laminated substrate in which cracks and peeling are less likely to occur at the connection between an electrode provided on a ceramic layer and an interlayer connecting conductor provided on a thermoplastic resin layer, even if thermal stress occurs.

[0011] The laminated substrate of the present invention comprises a first main surface and a second main surface opposite the first main surface, a first thermoplastic resin layer having a via hole penetrating from the first main surface to the second main surface, a ceramic layer arranged so as to be in contact with the first main surface, and a second thermoplastic resin layer arranged so as to be in contact with the second main surface, a first electrode formed on the main surface of the ceramic layer in contact with the first main surface, and a protective layer formed so as to cover at least a portion of the outline of the first electrode, a second electrode formed on the main surface of the second thermoplastic resin layer in contact with the second main surface, an interlayer connecting conductor connecting the first electrode and the second electrode arranged in the via hole, and an intermetallic compound formed between the interlayer connecting conductor and the first electrode.

[0012] According to the present invention, it is possible to provide a laminated substrate in which cracks and peeling are less likely to occur at the connection between the electrode provided on the ceramic layer and the interlayer connection conductor provided on the thermoplastic resin layer, even if thermal stress occurs.

[0013] FIG. 1A is a cross-sectional view schematically showing an example of a laminated substrate according to a first embodiment of the present invention. FIG. 1B is an enlarged view of the dashed line portion in FIG. 1A. FIG. 2 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor in a laminated substrate according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor in a laminated substrate according to another aspect of the second embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor in a laminated substrate according to a third embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor in a laminated substrate according to a fourth embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor in a laminated substrate according to another aspect of the present invention. FIG. 7 is a process diagram schematically showing an example of an LTCC green sheet preparation step in a method for producing a laminated substrate according to a fifth embodiment of the present invention. FIG. 8A is a process diagram schematically showing an example of a via hole filling step in an LTCC green sheet in a method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 8B is a process diagram schematically showing an example of a via hole filling step in an LTCC green sheet in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 9 is a process diagram schematically showing an example of an electrode pattern forming step in an LTCC green sheet in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 10 is a process diagram schematically showing an example of a protective layer paste applying step containing a ceramic material in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 11 is a process diagram schematically showing an example of an LTCC green sheet laminating step in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 12 is a process diagram schematically showing an example of an LTCC green sheet laminate firing step in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 13 is a process diagram schematically showing an example of a thermoplastic resin layer preparing step in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 14A is a process diagram schematically showing an example of a thermoplastic resin layer electrode pattern forming step in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 14B is a process diagram schematically showing an example of a thermoplastic resin layer electrode pattern forming step in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 15A is a process diagram schematically illustrating an example of a step of filling a via hole with a thermoplastic resin layer in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention.FIG. 15B is a process diagram schematically showing an example of a step of filling via holes in a thermoplastic resin layer in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 16 is a process diagram schematically showing an example of a step of laminating thermoplastic resin layers in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 17A is a process diagram schematically showing an example of a step of laminating multilayer ceramic layers and multilayer thermoplastic resin layers in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 17B is a process diagram schematically showing an example of a step of laminating multilayer ceramic layers and multilayer thermoplastic resin layers in the method for producing a laminated substrate according to the fifth embodiment of the present invention. FIG. 18A is an explanatory diagram schematically showing an example of a connection between an interlayer connection conductor and a first electrode by liquid phase diffusion bonding. FIG. 18B is an explanatory diagram schematically showing an example of a connection between an interlayer connection conductor and a first electrode by liquid phase diffusion bonding. FIG. 18C is an explanatory diagram schematically showing an example of a connection between an interlayer connection conductor and a first electrode by liquid phase diffusion bonding. FIG. 18D is an explanatory diagram schematically showing an example of a connection between an interlayer connection conductor and a first electrode by liquid phase diffusion bonding. Fig. 19 is a cross-sectional view schematically showing an example of a multilayer ceramic layer prepared in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. Fig. 20 is a cross-sectional view schematically showing an example of a multilayer thermoplastic resin layer prepared in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. Fig. 21 is a process chart schematically showing an example of a protective layer arranging step made of thermoplastic resin in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. Fig. 22A is a process chart schematically showing an example of a lamination step of a multilayer ceramic layer and a multilayer thermoplastic resin layer in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. Fig. 22B is a process chart schematically showing an example of a lamination step of a multilayer ceramic layer and a multilayer thermoplastic resin layer in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention.

[0014] The laminated substrate of the present invention will be described below. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied within the scope that does not change the gist of the present invention. Note that a combination of two or more of the individual desirable configurations of the present invention described below also constitutes the present invention.

[0015] The laminated substrate of the present invention includes a first main surface and a second main surface opposite the first main surface, a first thermoplastic resin layer having a via hole penetrating from the first main surface to the second main surface, a ceramic layer arranged in contact with the first main surface, and a second thermoplastic resin layer arranged in contact with the second main surface, wherein a first electrode is formed on the main surface of the ceramic layer in contact with the first main surface, and a protective layer is formed so as to cover at least a portion of the outline of the first electrode, a second electrode is formed on the main surface of the second thermoplastic resin layer in contact with the second main surface, an interlayer connection conductor is arranged in the via hole connecting the first electrode and the second electrode, and an intermetallic compound is formed between the interlayer connection conductor and the first electrode. That is, in the laminated substrate of the present invention, the protective layer is formed so as to cover at least a portion of the outline of the first electrode. The formation of such a protective layer can prevent the spread and formation of a low-ductility intermetallic compound at the connection portion of the interlayer connection conductor with the first electrode. Therefore, even if thermal stress occurs in the laminated substrate, the area where the intermetallic compound is formed is narrow, so that there are fewer areas where the thermal stress is difficult to alleviate.As a result, even if thermal stress occurs in the laminated substrate, cracks and peeling are less likely to occur at the connection between the electrodes provided on the ceramic layers and the interlayer connection conductors provided on the thermoplastic resin layers.

[0016] The laminated substrate of the present invention can be widely used in electronic devices such as portable information terminals and digital cameras as a laminated substrate with a built-in coil and as a micro DC-DC converter using the laminated substrate.

[0017] Hereinafter, embodiments of a multilayer substrate of the present invention will be described with reference to the drawings. [First Embodiment] First, a multilayer substrate according to a first embodiment of the present invention will be described. Fig. 1A is a cross-sectional view schematically showing an example of a multilayer substrate according to a first embodiment of the present invention. Fig. 1B is an enlarged view of the dashed line portion in Fig. 1A.

[0018] The laminated substrate 1 shown in Fig. 1A includes a multilayer ceramic layer 2 formed by stacking a plurality of ceramic layers 10, and a multilayer thermoplastic resin layer 3 formed by stacking a plurality of thermoplastic resin layers 20. In the laminated substrate 1 shown in Fig. 1A, the multilayer ceramic layer 2 is stacked on the multilayer thermoplastic resin layer 3.

[0019] As shown in FIGS. 1A and 1B, the multilayer thermoplastic resin layer 3 includes a first thermoplastic resin layer 21 in contact with the multilayer ceramic layer 2 .

[0020] 1B , the first thermoplastic resin layer 21 has a first main surface 21 a and a second main surface 21 b facing the first main surface 21 a, and has via holes 21 h penetrating from the first main surface 21 a to the second main surface 21 b. The first main surface 21 a of the first thermoplastic resin layer 21 is in contact with the multilayer ceramic layer 2.

[0021] The multilayer ceramic layer 2 includes a ceramic layer 11 disposed so as to contact the first main surface 21a of the first thermoplastic resin layer 21. A first electrode 31 is formed on the main surface of the ceramic layer 11 that contacts the first main surface 21a, and a protective layer 40 is further formed so as to cover an outline 31c of the first electrode 31. In the laminated substrate of the present invention, the protective layer may be formed so as to cover the entire outline of the first electrode, or may be formed so as to cover a portion of the outline of the first electrode.

[0022] The multilayer thermoplastic resin layer 3 includes a second thermoplastic resin layer 22 arranged so as to be in contact with the second main surface 21 b. A second electrode 32 is formed on the main surface of the second thermoplastic resin layer 22 in contact with the second main surface 21 b.

[0023] An interlayer connection conductor 50 that connects the first electrode 31 and the second electrode 32 is disposed in the via hole 21h. Furthermore, an intermetallic compound 61 is formed between the interlayer connection conductor 50 and the first electrode 31. Furthermore, an intermetallic compound 62 is formed between the interlayer connection conductor 50 and the second electrode 32. The via hole 21h has a tapered shape in which the opening on the first main surface 21a side is larger than the opening on the second main surface 21b side. With such a shape, the connection strength between the interlayer connection conductor 50 and the first electrode 31 can be improved.

[0024] In the laminated substrate 1, a protective layer 40 is formed so as to cover the contour 31c of the first electrode 31. The formation of such a protective layer 40 can prevent the spread and formation of a low-ductility intermetallic compound 61 at the connection portion between the interlayer connection conductor 50 and the first electrode 31. The intermetallic compound 61 has low ductility and is a portion that is difficult to alleviate thermal stress. In the laminated substrate 1, the area where the intermetallic compound 61 is formed is narrow, so there are fewer portions that are difficult to alleviate thermal stress. Therefore, even if thermal stress occurs in the laminated substrate 1, cracks and peeling are unlikely to occur at the connection portion between the first electrode 31 provided on the ceramic layer 11 and the interlayer connection conductor 50 provided on the first thermoplastic resin layer 21.

[0025] 1A and 1B , in the laminate substrate 1, a portion of the protective layer 40 is located inside the opening of the via hole 21h on the first main surface 21a, and the portion of the protective layer 40 located inside the via hole 21h is in contact with the interlayer connection conductor 50. When manufacturing the laminate substrate 1, the via hole 21h is filled with a conductive paste, and then the conductive paste is brought into contact with the first electrode 31, and the conductive paste is melted and then solidified to form the interlayer connection conductor 50. When the laminate substrate 1 has the above structure, the opening of the via hole 21h on the first main surface 21a is large, allowing sufficient contact between the conductive paste and the exposed surface of the first electrode 31. This improves the reliability of electrical connection.

[0026] As shown in FIG. 1A, the multilayer ceramic layer 2 may have an electrode pattern 2a, vias 2b, etc. formed thereon, and the multilayer thermoplastic resin layer 3 may have an electrode pattern 3a, vias 3b, etc. formed thereon.

[0027] Preferred embodiments of each configuration of the laminated substrate 1 will be described below.

[0028] (Interlayer Connection Conductor) The interlayer connection conductor 50 is formed by filling the via hole 21h with a conductive paste containing a first metal powder and a second metal powder having a melting point higher than that of the first metal powder, and then melting and solidifying the conductive paste. During this process, the first metal powder contained in the conductive paste reacts with the first electrode 31 to form an intermetallic compound 61. Preferably, the first metal powder is made of Sn or an Sn alloy, and the second metal powder is made of a Cu—Ni alloy or a Cu—Mn alloy. The conductive paste will be described in detail in the <Method for Manufacturing a Laminated Substrate> section below.

[0029] (Multilayer Ceramic Layer) The multilayer ceramic layer 2 is composed of ceramic layers 10 including a ceramic layer 11. Examples of materials that compose the ceramic layer 10 include low-temperature co-fired ceramic (LTCC) materials. Low-temperature co-fired ceramic materials are ceramic materials that can be sintered at temperatures of 1000°C or less and can be co-fired with Au, Ag, Cu, or other materials that have low resistivity. Specific examples of low-temperature co-fired ceramic materials include glass composite low-temperature co-fired ceramic materials that are obtained by mixing ceramic powders such as alumina, zirconia, magnesia, and forsterite with borosilicate glass, and ZnO-MgO-Al ２ O ３ -SiO ２ Glass-ceramic low-temperature sintering ceramic material using BaO-Al ２ O ３ -SiO ２ Ceramic powder and Al ２ O ３ -CaO-SiO ２ -MgO-B ２ O ３ Examples of suitable materials include non-glass-based low-temperature sintered ceramic materials using ceramic powders.

[0030] The thickness of the ceramic layer 10 is preferably determined appropriately depending on the design, and is preferably, for example, 5 μm or more and 100 μm or less.

[0031] The first electrode 31, the electrode pattern 2a, and the via 2b are preferably sintered bodies of a conductive paste made of a conductive powder, a plasticizer, and a binder. Furthermore, the first electrode 31, the electrode pattern 2a, and the via 2b are more preferably sintered bodies of copper (Cu) and its alloys. The first electrode 31, the electrode pattern 2a, and the via 2b may contain silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), gold (Au), and alloys thereof. The first electrode 31, the electrode pattern 2a, and the via 2b may be made of the same material or different materials.

[0032] The thickness of the first electrode 31 is preferably determined appropriately depending on the design, and is preferably, for example, 3 μm or more and 40 μm or less. In this specification, the "thickness of the first electrode" means the maximum thickness of the first electrode.

[0033] (Protective Layer) The protective layer 40 may be made of the same material as that constituting the first thermoplastic resin layer 21 or the same material as that constituting the ceramic layer 11 .

[0034] The thickness of the protective layer 40 is preferably 2 μm or more and 10 μm or less. If the thickness of the protective layer is less than 2 μm, the first electrode is likely to lift up. If the thickness of the protective layer is more than 10 μm, the protective layer becomes an obstacle when laminating the first thermoplastic resin layer and the ceramic layer, causing gaps to form between the interlayer connection conductor and the first electrode, preventing connection, or making the first electrode, electrode pattern, via, and other internal conductors more likely to deform.

[0035] The protective layer 40 preferably covers an area of ​​30 μm or more and 100 μm or less from the outline of the first electrode 31. By forming the protective layer 40 in such an area, it is possible to prevent the first electrode 31 from lifting up.

[0036] (Multilayer Thermoplastic Resin Layer) The multilayer thermoplastic resin layer 3 is composed of a thermoplastic resin layer 20 including a first thermoplastic resin layer 21 and a second thermoplastic resin layer 22. Examples of materials that can be used to compose the thermoplastic resin layer 20 include liquid crystal polymer (LCP), thermoplastic polyimide resin, polyether ether ketone resin (PEEK), and polyphenylene sulfide resin (PPS). Of these, liquid crystal polymer (LCP) is preferred. Liquid crystal polymer has a lower water absorption rate than other thermoplastic resins, and can prevent variations in electrical properties and a decrease in electrical connection reliability.

[0037] The thickness of the thermoplastic resin layer 20 is preferably determined appropriately depending on the design, and is preferably, for example, 10 μm or more and 100 μm or less.

[0038] As shown in FIG. 1B , the via hole 21h formed in the first thermoplastic resin layer 21 has a tapered shape. The tapered shape preferably has a stepwise inclination angle. In this case, the inclination angle may change in two steps, or in three or more steps. In the laminated substrate of the present invention, the via hole may have a tapered shape in which the opening on the first main surface side is smaller than the opening on the second main surface side, or may have a cylindrical shape in which the opening on the first main surface side and the opening on the second main surface side are the same size.

[0039] The diameter of the opening of the via hole 21h on the first main surface 21a side is preferably 20 μm or more and 200 μm or less, and the diameter of the opening of the via hole 21h on the second main surface 21b side is preferably 20 μm or more and 200 μm or less.

[0040] In the laminate substrate 1 shown in FIG. 1B , the area of ​​the first electrode 31 (the area of ​​the portion in contact with the intermetallic compound 61 and the protective layer 40) is larger than the opening area of ​​the via hole 21 h on the first main surface 21 a side. However, in the laminate substrate 1 of the present invention, the area of ​​the first electrode and the opening area of ​​the via hole on the first main surface side may be the same, or the area of ​​the first electrode may be smaller than the opening area of ​​the via hole on the first main surface side.

[0041] Examples of materials for the second electrode 32 and the electrode pattern 3a include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), and alloys thereof. The second electrode 32 and the electrode pattern 3a can be formed by laminating a metal foil on the thermoplastic resin layer 20 and patterning it using a technique such as etching. The second electrode 32 and the electrode pattern 3a may be made of the same material or different materials. The preferred material for the via 2b is the same as the preferred material for the interlayer connection conductor 50.

[0042] The thickness of the second electrode 32 is preferably determined appropriately depending on the design, and is preferably, for example, 3 μm or more and 40 μm or less.

[0043] [Second Embodiment] Next, a laminated substrate according to a second embodiment of the present invention will be described. Fig. 2 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor of a laminated substrate according to a second embodiment of the present invention. The laminated substrate 101 according to the second embodiment of the present invention shown in Fig. 2 has the same configuration as the laminated substrate 1 according to the first embodiment, except for the shape of the intermetallic compound. The structure of the laminated substrate 101 will be described in detail below with reference to the drawings.

[0044] As shown in Fig. 2 , the end of the protective layer 40 located inside the outline of the first electrode 31 is referred to as the inner end 41, and the main surface of the protective layer 40 that contacts and covers the outline of the first electrode 31 is referred to as the covered surface 40a. In the laminated substrate 101, a portion 161a of the intermetallic compound 161 is formed so as to contact the covered surface 40a on the inner end 41 side of the protective layer 40 and to be continuous with the intermetallic compound 161 formed between the interlayer connection conductor 50 and the first electrode 31. That is, the portion 161a of the intermetallic compound 161 is formed so as to penetrate between the protective layer 40 and the first electrode 31. Furthermore, the shape of the intermetallic compound 161 in Fig. 2 is such that the portion that contacts the covered surface 40a of the protective layer 40 (i.e., the portion indicated by the reference symbol "161a") is raised compared to other portions.

[0045] When manufacturing the laminated substrate of the present invention, the interlayer connection conductor is produced by contacting a conductive paste, which is a precursor of the interlayer connection conductor, with the first electrode, melting the conductive paste, and then solidifying the paste. If a protective layer is formed around the contour of the first electrode, the exposed surface of the first electrode (the surface in contact with the conductive paste) will be narrowed. In the manufactured laminated substrate, the physical connection stability and conductivity between the first electrode and the interlayer connection conductor depend on the contact area between them via the intermetallic compound. Therefore, forming a protective layer around the contour of the first electrode is detrimental to these effects. However, as in the laminated substrate 101, if a portion 161a of the intermetallic compound 161 contacts the coated surface 40a on the inner end 41 side of the protective layer 40 and is formed so as to be continuous with the intermetallic compound 161 formed between the interlayer connection conductor 50 and the first electrode 31, the contact area between the first electrode 31 and the intermetallic compound 161 can be increased. Therefore, the physical connection stability and conductivity between the first electrode 31 and the interlayer connection conductor 50 can be improved.

[0046] In the laminate substrate 101, the thickness of the first electrode 31 is preferably determined appropriately according to the design, and is preferably, for example, 3 μm or more and 40 μm or less. Note that in the laminate substrate 101, the portion of the first electrode 31 that contacts the part 161 a of the intermetallic compound 161 is thin. However, as described above, in this specification, the "thickness of the first electrode" means the maximum thickness of the first electrode, and therefore such a thin portion is not taken into consideration when measuring the "thickness of the first electrode."

[0047] In the laminate substrate 101, the thickness of the protective layer 40 is preferably 2 μm or more and 10 μm or less. If the thickness of the protective layer is less than 2 μm, the first electrode is likely to lift up. If the thickness of the protective layer is more than 10 μm, when an intermetallic compound is formed, the liquid phase in liquid phase diffusion bonding is less likely to exceed the protective layer, and the intermetallic compound is less likely to be formed so as to contact the coated surface on the inner end side of the protective layer.

[0048] Next, another aspect of the laminated substrate according to the second embodiment of the present invention will be described. Fig. 3 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor of a laminated substrate according to another aspect of the second embodiment of the present invention. The laminated substrate 201 shown in Fig. 3 has the same configuration as the laminated substrate 101 according to the second embodiment, except for the shape of the intermetallic compound.

[0049] 3, the shape of the intermetallic compound 261 is such that the surface that comes into contact with the first electrode 31 is flat. When the intermetallic compound 261 has such a shape, the contact area between the first electrode 31 and the intermetallic compound 261 can be increased, similarly to the above-described laminated substrate 101. Therefore, the physical connection stability and conductivity between the first electrode 31 and the interlayer connection conductor 50 can be improved.

[0050] [Third Embodiment] Next, a laminated substrate according to a third embodiment of the present invention will be described. Fig. 4 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor of a laminated substrate according to the third embodiment of the present invention. The laminated substrate 301 according to the third embodiment of the present invention shown in Fig. 4 has the same configuration as the laminated substrate 101 according to the second embodiment, except for the size of the opening of the via hole 21h in the first thermoplastic resin layer 21.

[0051] In the laminate substrate 301 shown in FIG. 4 , the opening area of ​​the via hole 321h on the first main surface 321a of the first thermoplastic resin layer 321 is smaller than the contact area between the intermetallic compound 161 and the first electrode 31. When manufacturing the laminate substrate of the present invention, a conductive paste, which is a precursor of the interlayer connection conductor, is brought into contact with the first electrode, and the conductive paste is melted and then solidified to form the interlayer connection conductor. At this time, the first electrode and the interlayer connection conductor are bonded by liquid-phase diffusion bonding. During this liquid-phase diffusion bonding, the liquid phase flows and covers the entire exposed surface of the first electrode 31. Therefore, the intermetallic compound 161 is formed over the entire exposed surface of the first electrode 31. Therefore, in the laminate substrate 301, no gap is formed between the first electrode 31 and the first thermoplastic resin layer 321, and the physical connection stability and conductivity between the first electrode 31 and the interlayer connection conductor 50 can be sufficiently increased.

[0052] [Fourth Embodiment] Next, a laminated substrate according to a fourth embodiment of the present invention will be described. Fig. 5 is a cross-sectional view schematically showing an example of the vicinity of an interlayer connection conductor of a laminated substrate according to the fourth embodiment of the present invention. The laminated substrate 401 according to the fourth embodiment of the present invention shown in Fig. 5 has the same configuration as the laminated substrate 101 according to the second embodiment, except for the size of the opening of the via hole 21h in the first thermoplastic resin layer 21.

[0053] 5, the opening area of ​​the via hole 421h on the first main surface 421a of the first thermoplastic resin layer 421 is the same as the opening area of ​​the protective layer 40. Even in this embodiment, the physical connection stability and conductivity between the first electrode 31 and the interlayer connection conductor 50 can be sufficiently increased.

[0054] [Other Aspects] In the laminated substrate of the present invention, when the protective layer is made of a ceramic material, pores are formed in the protective layer. Therefore, when the first electrode and the interlayer connection conductor are connected by liquid phase diffusion bonding, a liquid phase may enter the pores of the protective layer. Such an aspect will be described with reference to the drawings. FIG. 6 is a cross-sectional view schematically showing an example of the vicinity of the interlayer connection conductor of a laminated substrate according to another aspect of the present invention. The laminated substrate 501 shown in FIG. 6 has the same configuration as the laminated substrate 101 described above, except that the protective layer 540 is made of a ceramic material and a portion of the intermetallic compound 161 enters the pores 545 of the protective layer 540. The laminated substrate of such an aspect is also included in the laminated substrate of the present invention.

[0055] <Method of Manufacturing a Laminated Substrate> Next, a method of manufacturing a laminated substrate of the present invention will be described, in which the ceramic layers are made of an LTCC material.

[0056] [Fifth Embodiment] <LTCC Green Sheet Preparation Step> Fig. 7 is a process diagram schematically showing an example of an LTCC green sheet preparation step in a method for manufacturing a laminated substrate according to a fifth embodiment of the present invention. When manufacturing a laminated substrate according to the first embodiment of the present invention, first, a plurality of LTCC green sheets 10' are prepared, as shown in Fig. 7. The LTCC green sheets 10' can be prepared by the following method.

[0057] First, a ceramic powder, a binder, and a plasticizer are mixed in desired amounts to prepare a slurry. The ceramic powder may be any of the materials listed above as preferred materials for the ceramic layer 10. Conventionally known binders and plasticizers may be used.

[0058] Next, the slurry is applied onto a carrier film and formed into a sheet to obtain an LTCC green sheet 10'. A lip coater or a doctor blade can be used to apply the slurry. In this case, it is preferable that the thickness of the LTCC green sheet 10' be 5 μm or more and 100 μm or less.

[0059] 8A and 8B are process diagrams schematically illustrating an example of a process of filling a via hole in an LTCC green sheet in a method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 8A, a via hole 10h' is formed in an LTCC green sheet 10'. The method for forming the via hole 10h' is not particularly limited, and may be a mechanical punch, a CO ２ The via hole 10h' can be formed using a laser, a UV laser, etc. The opening diameter of the via hole 10h' is not particularly limited, but is preferably 20 μm or more and 200 μm or less.

[0060] Next, as shown in FIG. 8B , the via holes 10h′ are filled with a conductive paste 2b′ composed of a conductive powder, a plasticizer, and a binder. The ceramic powder that constitutes the LTCC green sheet 10′ may be added to the conductive paste 2b′. When the conductive paste 2b′ contains such ceramic powder, the difference in shrinkage rate between the LTCC green sheet 10′ and the conductive paste 2b′ is reduced. As a result, cracks and other defects can be prevented from occurring during firing of the LTCC green sheet 10′ and the conductive paste 2b′.

[0061] <Step of Forming Electrode Patterns on LTCC Green Sheets> FIG. 9 is a process diagram schematically illustrating an example of the step of forming electrode patterns on LTCC green sheets in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 9 , an electrode pattern 2a′ is printed on the surface of an LTCC green sheet 10′ using a conductive paste containing a conductive powder, a plasticizer, and a binder. Examples of printing methods that can be used include screen printing, inkjet printing, and gravure printing. The conductive paste forming the electrode pattern 2a′ may contain ceramic powder, which also constitutes the LTCC green sheet 10′. When the conductive paste forming the electrode pattern 2a′ contains such ceramic powder, the difference in shrinkage rate between the LTCC green sheet 10′ and the electrode pattern 2a′ is reduced. As a result, cracks and other defects can be prevented from occurring during firing of the LTCC green sheet 10′ and the electrode pattern 2a′.

[0062] In a later step, multiple LTCC green sheets 10' are stacked to form a laminate. In this laminate, a portion of the electrode patterns 2a' of the LTCC green sheets 10' located on the outermost layers (indicated by the reference symbol "31'" in FIG. 9) will become first electrodes connected to interlayer connection conductors in the laminated substrate to be manufactured. Furthermore, the LTCC green sheets 10' on which the electrode patterns 31' are formed will become ceramic substrates in contact with the first main surface of the first thermoplastic resin layer in the laminated substrate to be manufactured.

[0063] <Step of Applying a Protective Layer Paste Containing a Ceramic Material> Figure 10 is a process diagram schematically illustrating an example of a step of applying a protective layer paste containing a ceramic material in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 10, a protective layer paste 40' is applied to the contours of the electrode pattern 31'. The protective layer paste 40' is preferably made of the same material as the LTCC green sheet 10'. If the protective layer paste 40' and the LTCC green sheet 10' are made of the same material, their shrinkage rates during firing will be the same, preventing cracks from occurring during firing of the protective layer paste 40' and the LTCC green sheet 10'.

[0064] The thickness of the protective layer paste 40' is preferably 2 μm or more and 10 μm or less. If the thickness of the protective layer paste is less than 2 μm, the first electrode formed in a later step is likely to lift up. If the thickness of the protective layer paste exceeds 10 μm, the protective layer formed in a later step will be thick. Therefore, the protective layer will become an obstacle when laminating the first thermoplastic resin layer and the ceramic layer in a later step, and gaps will likely occur between the interlayer connection conductor and the first electrode. Furthermore, if the thickness of the protective layer paste exceeds 10 μm, the protective layer formed in a later step will be thick. Therefore, when an intermetallic compound is formed in a later step, the liquid phase reaction will be less likely to cross the protective layer, and the intermetallic compound will be less likely to form so as to contact the coating surface on the inner end side of the protective layer.

[0065] The protective layer paste 40' preferably covers an area of ​​30 μm to 100 μm inward from the outline of the electrode pattern 31'. By forming the protective layer paste 40' in such an area, it is possible to prevent the first electrode 31, which will be formed in a later process, from floating up.

[0066] <LTCC Green Sheet Lamination Step> Figure 11 is a process diagram schematically illustrating an example of the LTCC green sheet lamination step in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 11, a plurality of LTCC green sheets 10' are laminated to form an LTCC green sheet laminate 2'. The number of laminated sheets is preferably determined appropriately depending on the design. Thereafter, the LTCC green sheet laminate 2' is placed in a mold and pressure-bonded. The pressure and temperature are preferably set as desired depending on the design.

[0067] <LTCC Green Sheet Laminate Firing Step> FIG. 12 is a process diagram schematically illustrating an example of an LTCC green sheet laminate firing step in the laminated substrate manufacturing method according to the fifth embodiment of the present invention. Next, as shown in FIG. 12 , the LTCC green sheet laminate 2′ is heated and fired to form a multilayer ceramic layer 2. This step fires the conductive paste 2b′ into vias 2b, and the electrode pattern 2a′ into electrode patterns 2a and first electrodes 31. Firing can be performed using a firing furnace such as a batch furnace or a belt furnace. The firing conditions are not particularly limited, but are preferably 850°C or higher and 1050°C or lower, and 60 minutes or longer and 180 minutes or shorter. When the conductive paste 2b′ or the electrode pattern 2a′ contains copper (Cu), firing in a reducing atmosphere is preferred.

[0068] <Thermoplastic Resin Layer Preparation Step> Figure 13 is a process diagram schematically illustrating an example of the thermoplastic resin layer preparation step in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 13, a plurality of sheet-shaped thermoplastic resin layers 20 are prepared. Since the preferred material for the thermoplastic resin layer 20 has already been described, its description will be omitted here. The thickness of the thermoplastic resin layer 20 is preferably 10 µm or more and 100 µm or less.

[0069] <Step of Forming an Electrode Pattern on a Thermoplastic Resin Layer> FIGS. 14A and 14B are process diagrams schematically illustrating an example of the step of forming an electrode pattern on a thermoplastic resin layer in the manufacturing method of a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 14A, a metal foil 3a' is laminated on the main surface of the thermoplastic resin layer 20. Next, as shown in FIG. 14B, the metal foil 3a' is patterned by etching or the like to form an electrode pattern 3a. Examples of the metal foil 3a' include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), and alloys thereof. It is preferable that one main surface of the metal foil 3a' be a shiny surface and the other be a matte surface. It is preferable that the metal foil 3a' be laminated so that the matte surface is in contact with the main surface of the thermoplastic resin layer 20. The matte surface of the metal foil 3a' is subjected to a roughening treatment, and the surface roughness Rz (JIS B 0601-2001) is preferably 1 μm or more and 15 μm or less.

[0070] In a later step, the plurality of thermoplastic resin layers 20 are stacked to form a laminate. In the laminate, the thermoplastic resin layer 20 located at the outermost layer becomes the first thermoplastic resin layer 21. The thermoplastic resin layer 20 in contact with the second main surface 21b of the first thermoplastic resin layer 21 becomes the second thermoplastic resin layer 22. Furthermore, some of the electrode patterns 3a formed on the main surface of the second thermoplastic resin layer 22 on the second main surface 21b side become second electrodes 32 that connect to interlayer connection conductors in the laminated substrate to be manufactured.

[0071] 15A and 15B are process diagrams schematically illustrating an example of the step of filling via holes in a thermoplastic resin layer in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 15A, via holes 21h, 22h, and 20h are formed in the first thermoplastic resin layer 21, the second thermoplastic resin layer 22, and the other thermoplastic resin layer 20, respectively. The method for forming these via holes is not particularly limited, and may be a mechanical punch, a CO ２The via holes can be formed using a laser, a UV laser, or the like. After forming these via holes, it is preferable to perform a desmear treatment such as oxygen plasma treatment, corona discharge treatment, or potassium permanganate treatment. The opening diameters of the via holes 21h, 22h, and 20h are not particularly limited, but are preferably 20 μm or more and 200 μm or less. In FIG. 15A , for the convenience of showing the internal structure in a plan view, the via holes are formed directly below the electrode pattern 3a, and there are some locations where the via holes do not appear to be formed as through-holes. However, in reality, the positions where the electrode pattern 3a and the via holes are formed are offset in the depth direction, and the via holes are formed as through-holes.

[0072] 15B, via holes 21h, 22h, and 20h are filled with conductive paste 50', which is a precursor of the interlayer connection conductor. The filling method is not particularly limited, but screen printing, vacuum printing, etc. can be used.

[0073] The conductive paste 50' contains a first metal powder and a second metal powder having a melting point higher than that of the first metal powder. The first metal powder contained in the conductive paste 50' is preferably made of Sn or an Sn alloy, and the second metal powder is preferably made of a Cu-Ni alloy or a Cu-Mn alloy. Examples of such conductive paste 50' include the conductive paste described in Japanese Patent No. 5146627. Hereinafter, the metal component contained in the first metal powder will be referred to as the first metal, and the metal component contained in the second metal powder will be referred to as the second metal.

[0074] Examples of Sn or Sn alloys include simple Sn, or alloys containing Sn and at least one element selected from the group consisting of Cu, Ni, Ag, Au, Sb, Zn, Bi, In, Ge, Al, Co, Mn, Fe, Cr, Mg, Mn, Pd, Si, Sr, Te, and P. The Sn alloy preferably contains 70 wt % or more of Sn, more preferably 85 wt % or more.

[0075] The proportion of Ni in the Cu—Ni alloy is preferably 10% by weight or more and 15% by weight or less. Furthermore, the proportion of Mn in the Cu—Mn alloy is preferably 10% by weight or more and 15% by weight or less. This allows for the supply of sufficient Ni or Mn to form the desired intermetallic compound. When the proportion of Ni in the Cu—Ni alloy and the proportion of Mn in the Cu—Mn alloy are less than 10% by weight, all of the Sn tends to remain without forming an intermetallic compound. Furthermore, when the proportion of Ni in the Cu—Ni alloy and the proportion of Mn in the Cu—Mn alloy exceed 15% by weight, all of the Sn tends to remain without forming an intermetallic compound.

[0076] The Cu--Ni alloy or Cu--Mn alloy may contain Mn and Ni simultaneously, or may contain a third component such as P.

[0077] The arithmetic mean particle diameters of the first metal powder and the second metal powder are preferably 3 μm or more and 10 μm or less, respectively. If the mean particle diameters of these metal powders are too small, the manufacturing cost increases. Also, oxidation of the metal powder progresses, which tends to inhibit the reaction. On the other hand, if the mean particle diameters of these metal powders are too large, it becomes difficult to fill each via hole with the conductive paste 50′.

[0078] The proportion of the second metal in the metal components of the conductive paste 50' is preferably 30% by weight or more. That is, the proportion of the first metal in the metal components of the conductive paste 50' is preferably 70% by weight or less. In this case, the residual proportion of the first metal, such as Sn, is further reduced, and the proportion of intermetallic compounds can be increased.

[0079] The proportion of the metal component in the conductive paste 50' is preferably 70% by weight or more and 95% by weight or less. If the metal component exceeds 95% by weight, it becomes difficult to obtain a conductive paste 50' with excellent filling properties and low viscosity. On the other hand, if the metal component is less than 70% by weight, flux components are likely to remain.

[0080] The conductive paste 50' preferably contains a flux component. The flux component may be any of various known flux components typically used in conductive paste materials, including a resin. Examples of components other than the resin include a vehicle, a solvent, a thixotropic agent, and an activator.

[0081] The resin preferably contains at least one thermosetting resin selected from the group consisting of epoxy resin, phenol resin, polyimide resin, silicone resin or modified resin thereof, and acrylic resin, or at least one thermoplastic resin selected from the group consisting of polyamide resin, polystyrene resin, polymethacrylic resin, polycarbonate resin, and cellulose-based resin.

[0082] Examples of the vehicle include rosin-based resins made from rosin and derivatives thereof such as modified rosin, synthetic resins, and mixtures thereof. Examples of the rosin-based resins made from rosin and derivatives thereof such as modified rosin include gum rosin, tall rosin, wood rosin, polymerized rosin, hydrogenated rosin, formylated rosin, rosin ester, rosin-modified maleic acid resin, rosin-modified phenolic resin, rosin-modified alkyd resin, and various other rosin derivatives. Examples of the synthetic resins made from rosin and derivatives thereof such as modified rosin include polyester resin, polyamide resin, phenoxy resin, and terpene resin.

[0083] Known examples of the solvent include alcohols, ketones, esters, ethers, aromatic solvents, and hydrocarbons. Specific examples include benzyl alcohol, ethanol, isopropyl alcohol, butanol, diethylene glycol, ethylene glycol, glycerin, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, butyl benzoate, diethyl adipate, dodecane, tetradecene, α-terpineol, terpineol, 2-methyl-2,4-pentanediol, 2-ethylhexanediol, toluene, xylene, propylene glycol monophenyl ether, diethylene glycol monohexyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diisobutyl adipate, hexylene glycol, cyclohexanedimethanol, 2-terpinyloxyethanol, 2-dihydroterpinyloxyethanol, and mixtures thereof. Preferred are terpineol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.

[0084] Specific examples of the thixotropic agent include hydrogenated castor oil, carnauba wax, amides, hydroxy fatty acids, dibenzylidene sorbitol, bis(p-methylbenzylidene)sorbitols, beeswax, stearic acid amide, hydroxystearic acid ethylene bisamide, etc. Furthermore, if necessary, these can also be used as thixotropic agents to which fatty acids such as caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, hydroxy fatty acids such as 1,2-hydroxystearic acid, antioxidants, surfactants, and amines have been added.

[0085] Examples of the activator include amine hydrohalides, organic halogen compounds, organic acids, organic amines, and polyhydric alcohols.

[0086] Examples of the amine hydrohalides include diphenylguanidine hydrobromide, diphenylguanidine hydrochloride, cyclohexylamine hydrobromide, ethylamine hydrochloride, ethylamine hydrobromide, diethylaniline hydrobromide, diethylaniline hydrochloride, triethanolamine hydrobromide, and monoethanolamine hydrobromide.

[0087] Examples of the organic halogen compounds include chlorinated paraffin, tetrabromoethane, dibromopropanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, and tris(2,3-dibromopropyl)isocyanurate.

[0088] Examples of the organic acids include malonic acid, fumaric acid, glycolic acid, citric acid, malic acid, succinic acid, phenylsuccinic acid, maleic acid, salicylic acid, anthranilic acid, glutaric acid, suberic acid, adipic acid, sebacic acid, stearic acid, abietic acid, benzoic acid, trimellitic acid, pyromellitic acid, and dodecanoic acid.

[0089] Examples of the organic amine include monoethanolamine, diethanolamine, triethanolamine, tributylamine, aniline, and diethylaniline.

[0090] Examples of the polyhydric alcohol include erythritol, pyrogallol, and ribitol.

[0091] 16 is a process diagram schematically illustrating an example of the step of laminating thermoplastic resin layers in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 16, a first thermoplastic resin layer 21, a second thermoplastic resin layer 22, and other thermoplastic resin layers 20 are laminated to form a multilayer thermoplastic resin layer 3.

[0092] 17A and 17B are process diagrams schematically illustrating an example of a lamination process of a multilayer ceramic layer and a multilayer thermoplastic resin layer in a method for manufacturing a laminated substrate according to a fifth embodiment of the present invention. Next, as shown in FIG. 17A , a multilayer ceramic layer 2 is laminated on a multilayer thermoplastic resin layer 3. At this time, the multilayer ceramic layer 2 is aligned so that the conductive paste 50′ filled in the first thermoplastic resin layer 21 of the multilayer thermoplastic resin layer 3 contacts the exposed surface of the first electrode 31 of the ceramic layer 11 arranged on the outermost layer of the multilayer ceramic layer 2.

[0093] 17B, ​​the multilayer thermoplastic resin layer 3 and the multilayer ceramic layer 2 are integrated by applying pressure and heat. At this time, the first thermoplastic resin layer 21 conforms to the irregularities on the surface of the ceramic layer 11, and the multilayer thermoplastic resin layer 3 and the multilayer ceramic layer 2 are closely attached to each other by an anchor effect.

[0094] In this step, for example, the treatment is carried out at 230° C. or higher and 350° C. or lower under normal pressure.

[0095] In this process, the conductive paste 50' melts and then solidifies to become the interlayer connection conductor 50. The interlayer connection conductor 50 and the first electrode 31 are connected by liquid phase diffusion bonding. At this time, an intermetallic compound 61 is formed between the interlayer connection conductor 50 and the first electrode 31.

[0096] This liquid phase diffusion bonding will be described with reference to the drawings. Figures 18A to 18D are explanatory diagrams that schematically show an example of connection between an interlayer connection conductor and a first electrode by liquid phase diffusion bonding.

[0097] 18A , the conductive paste 50′ contains a first metal powder 51 and a second metal powder 52 having a melting point higher than that of the first metal powder 51. The conductive paste 50′ is in contact with the first electrode 31.

[0098] As shown in FIG. 18B, when the conductive paste 50' is heated in this state and reaches the melting point of the first metal powder 51, the first metal powder 51 melts and becomes the first metal 51a in a liquid phase.

[0099] 18C , when heat is further applied, the liquid-phase first metal 51a reacts with the second metal powder 52 to form an intermetallic compound 60. Furthermore, the liquid-phase first metal 51a spreads in a diffusive manner over the first electrode 31, and the liquid-phase first metal 51a reacts with the metal that constitutes the first electrode 31 to form an intermetallic compound 61.

[0100] Thereafter, when the heating is completed and the temperature drops, as shown in Fig. 18D, the liquid-phase first metal 51a solidifies to become the interlayer connection conductor 50. Note that, for convenience, the outline of the intermetallic compound 60 derived from the second metal powder 52 is shown by a broken line in Fig. 18D, but in reality, the boundary is not clear and the intermetallic compound 60 does not appear to be particulate.

[0101] In this step, the interlayer connection conductor and the second electrode are also connected by liquid phase diffusion bonding, so that an intermetallic compound is also formed between the interlayer connection conductor and the second electrode.

[0102] Through the above steps, the laminated substrate 1 can be manufactured.

[0103] In manufacturing the laminated substrate of the present invention, the composition of the conductive paste 50', the composition and thickness of the first electrode 31, the thickness of the protective layer 40, and the pressure and heating temperature in the lamination process of the multilayer ceramic layer and the multilayer thermoplastic resin layer can be adjusted to form an intermetallic compound having the shape shown in Figures 2 to 6. In other words, by making the above adjustments, a part of the intermetallic compound can be brought into contact with the coated surface on the inner end side of the protective layer and formed so as to be continuous with the intermetallic compound formed between the interlayer connection conductor and the first electrode.

[0104] Electronic components such as IC chips and SMD components can be mounted on the manufactured laminated substrate 1 by a reflow process or the like. After this reflow process, the laminated substrate 1 with the mounted electronic components may be cleaned and molded with resin. Furthermore, the molded laminated substrate 1 may be cut into individual pieces by a dicer cutter, laser cutter, or the like. A shielding film may then be formed on the surface of the molded resin. [Sixth Embodiment] Next, another method for manufacturing the laminated substrate of the present invention will be described. Note that the following description will be given of a case in which the ceramic layer is made of an LTCC material. The manufacturing method of the laminated substrate according to the sixth embodiment of the present invention is the same as the manufacturing method of the laminated substrate according to the fifth embodiment of the present invention, except that the above-mentioned <Step of applying a protective layer paste containing a ceramic material> is not performed, and the following <Step of disposing a protective layer made of a thermoplastic resin> is performed after the above-mentioned <Step of filling via holes with a thermoplastic resin layer>. The manufacturing method of the laminated substrate according to the sixth embodiment of the present invention will be described in detail below with reference to the drawings.

[0105] <Preparation of Multilayer Ceramic Layer> Figure 19 is a cross-sectional view schematically showing an example of a multilayer ceramic layer prepared in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. The steps of the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention, namely, the <LTCC green sheet preparation step>, the <LTCC green sheet via hole filling step>, the <LTCC green sheet electrode pattern forming step>, the <LTCC green sheet lamination step>, and the <LTCC green sheet laminate firing step>, are carried out in this order to produce a multilayer ceramic layer 602 as shown in Figure 19. Multilayer ceramic layer 602 has the same structure as multilayer ceramic layer 2, except that protective layer 40 is not formed.

[0106] 20 is a cross-sectional view schematically showing an example of a multilayer thermoplastic resin layer prepared in the method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. The multilayer thermoplastic resin layer 3 is prepared by carrying out the steps of preparing a thermoplastic resin layer, forming an electrode pattern on a thermoplastic resin layer, filling via holes in a thermoplastic resin layer, and laminating a thermoplastic resin layer, which are steps in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention.

[0107] <Step of Arranging a Protective Layer Made of Thermoplastic Resin> Figure 21 is a process diagram schematically illustrating an example of the step of arranging a protective layer made of thermoplastic resin in the manufacturing method of a laminated substrate according to the sixth embodiment of the present invention. Next, a protective layer 640 made of thermoplastic resin is formed on the first thermoplastic resin layer 21, thereby forming the multilayer thermoplastic resin layer 3 into the multilayer thermoplastic resin layer 603. The protective layer 640 is preferably made of the same material as the thermoplastic resin layer 20. Furthermore, the protective layer 640 is formed in a position that covers the outline of the first electrode 31 formed on the multilayer ceramic layer 602 when the subsequent <Step of Laminating the Multilayer Ceramic Layer and the Multilayer Thermoplastic Resin Layer> is performed. Such a position can be determined by prior design.

[0108] 22A and 22B are process diagrams schematically illustrating an example of a process for laminating a multilayer ceramic layer and a multilayer thermoplastic resin layer in a method for manufacturing a laminated substrate according to a sixth embodiment of the present invention. Next, as shown in FIG. 22A , a multilayer ceramic layer 2 is laminated on a multilayer thermoplastic resin layer 603. At this time, the conductive paste 50′ filled in the first thermoplastic resin layer 21 of the multilayer thermoplastic resin layer 603 is aligned so as to contact the exposed surface of the first electrode 31 of the ceramic layer 11 arranged on the outermost layer of the multilayer ceramic layer 602.

[0109] 22B, pressure and heat are applied to integrate the multilayer thermoplastic resin layer 603 and the multilayer ceramic layer 602. Through the above steps, a laminated substrate 601 having a protective layer 640 made of a thermoplastic resin can be manufactured.

[0110] This specification describes the following:

[0111] The present disclosure (1) is a laminated substrate comprising: a first thermoplastic resin layer having a first main surface and a second main surface opposite the first main surface, the first thermoplastic resin layer having a via hole penetrating from the first main surface to the second main surface; a ceramic layer arranged to be in contact with the first main surface; and a second thermoplastic resin layer arranged to be in contact with the second main surface, wherein a first electrode is formed on the main surface of the ceramic layer in contact with the first main surface, and a protective layer is further formed so as to cover at least a part of the outline of the first electrode; a second electrode is formed on the main surface of the second thermoplastic resin layer in contact with the second main surface; an interlayer connecting conductor connecting the first electrode and the second electrode is arranged in the via hole; and an intermetallic compound is formed between the interlayer connecting conductor and the first electrode.

[0112] The present disclosure (2) is the laminated substrate according to the present disclosure (1), in which the protective layer has an inner end portion located inside the contour of the first electrode and a coating surface that is in contact with and covers at least a part of the contour of the first electrode, and a part of the intermetallic compound is in contact with the coating surface on the inner end side of the protective layer and is formed so as to be continuous with the intermetallic compound formed between the interlayer connection conductor and the first electrode.

[0113] The present disclosure (3) is the laminated substrate according to the present disclosure (1) or (2), wherein the protective layer is made of the same material as the material constituting the ceramic layer.

[0114] The present disclosure (4) is the laminated substrate according to any one of the present disclosures (1) to (3), wherein the protective layer is made of the same material as the material constituting the first thermoplastic resin layer.

[0115] The present disclosure (5) is a laminated substrate according to any one of the present disclosures (1) to (4), in which a portion of the protective layer is located inside the opening of the via hole on the first main surface, and the portion of the protective layer located inside the via hole is in contact with the interlayer connecting conductor.

[0116] 1, 101, 201, 301, 401, 501, 601 Laminated substrate 2, 602 Multilayer ceramic layer 2' LTCC green sheet laminate 2a, 2a', 3a Electrode pattern 2b, 3b Via 2b', 50' Conductive paste 3, 603 Multilayer thermoplastic resin layer 3a' Metal foil 10, 11 Ceramic layer 10' LTCC green sheet 10h', 21h, 22h, 321h, 421h Via hole 20 Thermoplastic resin layer 21, 321, 421 First thermoplastic resin layer 21a, 321a, 421a First main surface of first thermoplastic resin layer 21b Second main surface of first thermoplastic resin layer 22 Second thermoplastic resin layer 31 First electrode 31' Electrode pattern 31c Outline of first electrode 32 Second electrode 40, 540, 640 Protective layer 40' Protective layer paste 40a Covered surface of protective layer 41 Inner end of protective layer 50 Interlayer connecting conductor 51 First metal powder 51a Liquid phase first metal 52 Second metal powder 60, 61, 62, 161, 261 Intermetallic compound 161a Part of intermetallic compound 545 Pores

Claims

1. a first thermoplastic resin layer having a first main surface and a second main surface opposite to the first main surface, the first thermoplastic resin layer having a via hole penetrating from the first main surface to the second main surface; a ceramic layer disposed in contact with the first major surface; a second thermoplastic resin layer disposed in contact with the second main surface; a first electrode is formed on a main surface of the ceramic layer in contact with the first main surface, and a protective layer is further formed so as to cover at least a portion of a contour of the first electrode; a second electrode is formed on a principal surface of the second thermoplastic resin layer in contact with the second principal surface; an interlayer connection conductor that connects the first electrode and the second electrode is disposed in the via hole; The laminated substrate further comprises an intermetallic compound formed between the interlayer connection conductor and the first electrode.

2. the protective layer has an inner end portion located inside a contour of the first electrode and a covering surface in contact with and covering at least a portion of the contour of the first electrode; 2. The laminated substrate according to claim 1, wherein a portion of the intermetallic compound is in contact with the coated surface on the inner end side of the protective layer and is formed so as to be continuous with the intermetallic compound formed between the interlayer connection conductor and the first electrode.

3. 3. The laminated substrate according to claim 1, wherein the protective layer is made of the same material as that constituting the ceramic layer.

4. 3. The laminated substrate according to claim 1, wherein the protective layer is made of the same material as that constituting the first thermoplastic resin layer.

5. 3. The laminated substrate according to claim 1, wherein on the first main surface, a portion of the protective layer is located inside the opening of the via hole, and the portion of the protective layer located inside the via hole is in contact with the interlayer connection conductor.