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

Technical Field

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

Background Art

[0002] Conventionally, module components using a multilayer substrate incorporating passive elements have been put into practical use. For example, a DCDC converter module in which a switching IC (integrated circuit) chip and a chip capacitor are mounted on a multilayer substrate incorporating a coil as the passive element is well known.

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

[0004] In other words, Patent Document 1 includes: a ceramic multilayer substrate having a passive element built in and 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 surface mount components; 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 that serves as a connection terminal to a motherboard; and a first thermoplastic resin mounted on the first thermoplastic resin layer. A module component is disclosed, comprising a surface mount component connected to the first land of a layer, wherein the thickness of the first thermoplastic resin layer and the second thermoplastic resin layer are different, the thickness of the first thermoplastic resin layer is greater than the thickness of the second thermoplastic resin layer, the ceramic multilayer substrate is a substrate made of a non-glassy low-temperature co-fired ceramic material, and the first terminal electrode of the ceramic multilayer substrate and an interlayer conductor provided in the first thermoplastic resin layer, and the second terminal electrode of the ceramic multilayer substrate and an interlayer conductor provided in the second thermoplastic resin layer are joined by liquid-phase diffusion bonding, respectively.

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

[0006] Patent Document 2 discloses an interlayer connecting conductor for connecting 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 connecting conductor. The intermetallic compound layer is formed when the metal constituting the interlayer connecting conductor, such as Sn or a Sn alloy, is heated and melts, then reacts with the metal constituting the conductor wiring layer (e.g., Cu). In other words, the intermetallic compound layer is formed when liquid-phase diffusion bonding is performed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6819668 [Patent Document 2] International Publication No. 2019 / 003729 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0009] Since the linear thermal expansion coefficients of the ceramic layer and the thermoplastic resin layer are different, when heat is applied to the laminated substrate, thermal stress is generated between the ceramic layer and the thermoplastic resin layer. Such thermal stress is particularly likely to occur in the interlayer connecting conductor located at the boundary between the ceramic layer and the thermoplastic resin layer. Thermal stress is especially likely to occur at the connection point between the interlayer connecting conductor and the electrode provided in the ceramic layer. As described above, an intermetallic compound layer is formed between the electrode provided in the ceramic layer and the interlayer connecting conductor provided in the thermoplastic resin layer. Since the intermetallic compound has low ductility, it does not easily absorb thermal stress. Therefore, when the interlayer connecting conductor is subjected to the above-mentioned thermal stress, there is a problem in that cracks and delaminations are likely to occur, starting from the intermetallic compound and the surrounding interlayer connecting conductor.

[0010] The present invention was made to solve the above problems, and the 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 the electrode provided in the ceramic layer and the interlayer connecting conductor provided in the thermoplastic resin layer, even when thermal stress is generated. [Means for solving the problem]

[0011] The laminated substrate of the present invention comprises a first thermoplastic resin layer having a first main surface and a second main surface facing the first main surface, and having via holes penetrating from the first main surface to the second main surface; a ceramic layer disposed in contact with the first main surface; and a second thermoplastic resin layer disposed in contact with the second main surface. 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 contour 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 disposed in the via hole, and an intermetallic compound is formed between the interlayer connecting conductor and the first electrode. [Effects of the Invention]

[0012] According to the present invention, even if thermal stress occurs, 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 in the ceramic layer and the interlayer connecting conductor provided in the thermoplastic resin layer. [Brief explanation of the drawing]

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

[0014] The laminated substrate of the present invention will be described below. However, the present invention is not limited to the following configurations and can be modified and applied as appropriate without altering the essence of the invention. Furthermore, 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 comprises a first thermoplastic resin layer having a first main surface and a second main surface facing the first main surface, and having via holes penetrating from the first main surface to the second main surface; a ceramic layer disposed in contact with the first main surface; and a second thermoplastic resin layer disposed in contact with the second main surface. 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 contour 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 disposed in the via hole, and an intermetallic compound is formed between the interlayer connecting conductor and the first electrode. In other words, in the laminated substrate of the present invention, a protective layer is formed so as to cover at least a portion of the contour of the first electrode. When such a protective layer is formed, it is possible to prevent the formation of a low-ductility intermetallic compound at the connection portion between the interlayer connecting conductor and the first electrode. Therefore, even if thermal stress occurs in the laminated substrate, the area where intermetallic compounds are formed is narrow, resulting in fewer areas where thermal stress is difficult to relieve. As a result, even when thermal stress occurs in the laminated substrate, cracks and delamination are less likely to occur at the connection between the electrodes provided in the ceramic layer and the interlayer connecting conductors provided in the thermoplastic resin layer.

[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, or as an ultra-compact DC-DC converter using the laminated substrate.

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

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

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

[0020] As shown in Figure 1B, the first thermoplastic resin layer 21 comprises a first main surface 21a and a second main surface 21b facing the first main surface 21a, and has via holes 21h that penetrate from the first main surface 21a to the second main surface 21b. Furthermore, the first main surface 21a 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 positioned in contact with 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 formed to cover the contour 31c of the first electrode 31. In the laminated substrate of the present invention, the protective layer may be formed to cover the entire contour of the first electrode, or it may be formed to cover a part of the contour of the first electrode.

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

[0023] An interlayer connecting conductor 50 is placed in the via hole 21h, connecting the first electrode 31 and the second electrode 32. Furthermore, an intermetallic compound 61 is formed between the interlayer connecting conductor 50 and the first electrode 31. In addition, an intermetallic compound 62 is formed between the interlayer connecting conductor 50 and the second electrode 32. The beer hole 21h has a tapered shape, with the opening on the first main surface 21a side being larger than the opening on the second main surface 21b side. This shape allows for improved connection strength between the interlayer connecting conductor 50 and the first electrode 31.

[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 prevents the formation of a low-ductility intermetallic compound 61 at the connection point between the interlayer connecting conductor 50 and the first electrode 31. The intermetallic compound 61 has low ductility and is a region where thermal stress is difficult to relieve. In the laminated substrate 1, the area where the intermetallic compound 61 is formed is narrow, resulting in fewer areas where thermal stress is difficult to relieve. Therefore, even if thermal stress occurs in the laminated substrate 1, cracks and peeling are less likely to occur at the connection between the first electrode 31 provided in the ceramic layer 11 and the interlayer connecting conductor 50 provided in the first thermoplastic resin layer 21.

[0025] As shown in Figures 1A and 1B, in the laminated 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 connecting conductor 50. When manufacturing the laminated substrate 1, conductive paste is filled into via holes 21h, and then the conductive paste is brought into contact with the first electrode 31, melting the conductive paste and then solidifying it to form the interlayer connecting conductor 50. When the laminated 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. Therefore, electrical connection reliability can be improved.

[0026] As shown in Figure 1A, the multilayer ceramic layer 2 may have electrode patterns 2a, vias 2b, etc., and the multilayer thermoplastic resin layer 3 may have electrode patterns 3a, vias 3b, etc.

[0027] The following describes preferred embodiments of each configuration of the laminated substrate 1.

[0028] (Interlayer connecting conductor) The interlayer connecting conductor 50 is formed when a conductive paste containing a first metal powder and a second metal powder having a higher melting point than the first metal powder is filled into a via hole 21h, and the conductive paste melts and then solidifies. At this time, 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 consists of Sn or a Sn alloy, and the second metal powder consists of a Cu-Ni alloy or a Cu-Mn alloy. The conductive paste will be described in detail later in the section on "Method for Manufacturing Laminated Substrates".

[0029] (Multilayer ceramic layer) The multilayer ceramic layer 2 is composed of a ceramic layer 10 which includes a ceramic layer 11. Examples of materials constituting the ceramic layer 10 include low-temperature sintered ceramic (LTCC) materials. Low-temperature sintered ceramic materials are ceramic materials that can be sintered at temperatures below 1000°C and can be co-fired with materials with low resistivity such as Au, Ag, and Cu. Specifically, examples of low-temperature sintered ceramic materials include glass composite low-temperature sintered ceramic materials made by mixing ceramic powders such as alumina, zirconia, magnesia, and forsterite with borosilicate glass; crystallized glass low-temperature sintered ceramic materials using ZnO-MgO-Al2O3-SiO2 crystallized glass; and non-glass low-temperature sintered ceramic materials using BaO-Al2O3-SiO2 ceramic powder or Al2O3-CaO-SiO2-MgO-B2O3 ceramic powder.

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

[0031] The first electrode 31, electrode pattern 2a, and via 2b are preferably sintered bodies of a conductive paste consisting of conductive powder, plasticizer, and binder. Furthermore, it is more preferable that the first electrode 31, electrode pattern 2a, and via 2b are sintered bodies of copper (Cu) and its alloys. The first electrode 31, electrode pattern 2a, and via 2b may contain silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), gold (Au), and alloys thereof. Furthermore, 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 according to the design, for example, it is preferably 3 μm or more and 40 μm or less. In this specification, "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 the material constituting the first thermoplastic resin layer 21, or it may be made of the same material as the material 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 more likely to lift up. If the thickness of the protective layer exceeds 10 μm, the protective layer becomes an obstacle when laminating the first thermoplastic resin layer and the ceramic layer, causing a gap to form between the interlayer connecting conductor and the first electrode, making connection impossible, or making the internal conductors such as the first electrode, electrode pattern, and vias more susceptible to deformation.

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

[0036] (Multi-layer 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 constituting the thermoplastic resin layer 20 include liquid crystal polymer (LCP), thermoplastic polyimide resin, polyetheretherketone resin (PEEK), and polyphenylene sulfide resin (PPS). Among these, liquid crystal polymer (LCP) is preferred. Compared to other thermoplastic resins, liquid crystal polymer has a lower water absorption rate, which 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 according to the design, for example, it is preferably 10 μm or more and 100 μm or less.

[0038] As shown in Figure 1B, the via holes 21h formed in the first thermoplastic resin layer 21 have a tapered shape. Furthermore, the tapered shape is preferably characterized by gradually varying inclination angles. In this case, the inclination angle may change in two stages, or it may change in three or more stages. In the laminated substrate of the present invention, the via holes may have a tapered shape where the opening on the first main surface side is smaller than the opening on the second main surface side, or they may have a cylindrical shape where the openings on the first main surface side and the openings 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. 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 laminated substrate 1 shown in Figure 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 21h on the first main surface 21a side. However, in the laminated 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 electrode pattern 3a include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), and alloys thereof. The second electrode 32 and electrode pattern 3a can be formed by laminating a metal foil onto a thermoplastic resin layer 20 and patterning it using methods such as etching. Furthermore, the second electrode 32 and the electrode pattern 3a may be made of the same material or different materials. Furthermore, the preferred material for via 2b is the same as the preferred material for the interlayer connecting conductor 50.

[0042] The thickness of the second electrode 32 is preferably determined appropriately according to the design, for example, it is preferably 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. Figure 2 is a schematic cross-sectional view showing an example of the vicinity of an interlayer connecting conductor in 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 Figure 2, has the same configuration as the laminated substrate 1 according to the first embodiment, except that the shape of the intermetallic compound is different. The structure of the laminated substrate 101 is described in detail below with reference to the drawings.

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

[0045] In manufacturing the laminated substrate of the present invention, an interlayer connecting conductor is produced by bringing a conductive paste, which is a precursor of the interlayer connecting conductor, into contact with the first electrode, melting the conductive paste, and then allowing it to solidify. In this case, if a protective layer is formed on the contour of the first electrode, the exposed surface of the first electrode (the contact surface with the conductive paste) becomes smaller. In manufactured laminated substrates, the physical connection stability and conductivity between the first electrode and the interlayer connecting conductor depend on the contact area between them via the intermetallic compound. Therefore, the formation of a protective layer around the contour of the first electrode is detrimental to these effects. However, if, as in the laminated substrate 101, a portion 161a of the intermetallic compound 161 is in contact with the covering surface 40a on the inner end 41 side of the protective layer 40, and is formed to be continuous with the intermetallic compound 161 formed between the interlayer connecting 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 connecting conductor 50 can be improved.

[0046] In the laminated substrate 101, the thickness of the first electrode 31 is preferably determined appropriately according to the design, for example, it is preferably 3 μm or more and 40 μm or less. In the laminated substrate 101, the portion of the first electrode 31 that contacts a part 161a of the intermetallic compound 161 is thinner. However, as stated above, in this specification, "thickness of the first electrode" refers to the maximum thickness of the first electrode, so these thinner portions are not considered when measuring the "thickness of the first electrode".

[0047] In the laminated 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 more likely to lift up. When the thickness of the protective layer exceeds 10 μm, the liquid phase in the liquid-phase diffusion bonding process becomes less likely to penetrate the protective layer when intermetallic compounds are formed, making it less likely for the intermetallic compounds to form in contact with the coating surface on the inner end side of the protective layer.

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

[0049] In the laminated substrate 201 shown in Figure 3, the shape of the intermetallic compound 261 is such that the surface in contact with the first electrode 31 is flat. If the intermetallic compound 261 has this shape, the contact area between the first electrode 31 and the intermetallic compound 261 can be increased, similar to the laminated substrate 101. Therefore, the physical connection stability and conductivity between the first electrode 31 and the interlayer connecting conductor 50 can be improved.

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

[0051] In the laminated substrate 301 shown in Figure 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 area in contact between the intermetallic compound 161 and the first electrode 31. In manufacturing the laminated substrate of the present invention, an interlayer connecting conductor is produced by bringing a conductive paste, which is a precursor of the interlayer connecting conductor, into contact with the first electrode, melting the conductive paste, and then allowing it to solidify. At this time, the first electrode and the interlayer connecting conductor are joined by liquid-phase diffusion bonding. When this liquid-phase diffusion bonding occurs, 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 laminated substrate 301, no gap is created 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 connecting conductor 50 can be sufficiently high.

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

[0053] In the laminated substrate 401 shown in Figure 5, the opening area of ​​the via holes 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 configuration, the physical connection stability and conductivity between the first electrode 31 and the interlayer connecting conductor 50 can be sufficiently high.

[0054] [Other forms] In the laminated substrate of the present invention, if the protective layer is made of a ceramic material, pores will be formed in the protective layer. Therefore, when connecting the first electrode and the interlayer connecting conductor by liquid-phase diffusion bonding, the liquid phase may enter the pores of the protective layer. This embodiment will be explained with reference to the drawings. Figure 6 is a schematic cross-sectional view showing an example of the vicinity of an interlayer connecting conductor in a laminated substrate according to another aspect of the present invention. The laminated substrate 501 shown in Figure 6 has the same configuration as the laminated substrate 101, except that the protective layer 540 is made of a ceramic material and a portion of the intermetallic compound 161 is embedded in the pores 545 of the protective layer 540. Laminated substrates of this type are also included in the laminated substrate of the present invention.

[0055] <Manufacturing method for laminated substrates> Next, the method for manufacturing the laminated substrate of the present invention will be described. In the following description, the case in which the ceramic layer is made of LTCC material will be explained.

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

[0057] First, ceramic powder, a binder, and a plasticizer are mixed in an arbitrary amount to prepare a slurry. As the ceramic powder, the materials mentioned above as the preferable materials for the ceramic layer 10 can be used. The binder and the plasticizer can be those conventionally known.

[0058] Next, the slurry is applied onto a carrier film to form a sheet, resulting in the LTCC green sheet 10'. For slurry application, a lip coater or a doctor blade can be used. At this time, the thickness of the LTCC green sheet 10' is preferably 5 μm or more and 100 μm or less.

[0059] <Via Hole Filling Process of LTCC Green Sheet> FIGS. 8A and 8B are process diagrams schematically showing an example of the via hole filling process of the LTCC green sheet of the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 8A, via holes 10h' are formed in the LTCC green sheet 10'. The method for forming the via holes 10h' is not particularly limited, and they can be formed using a mechanical punch, a CO2 laser, a UV laser, or the like. The opening diameter of the via holes 10h' is not particularly limited, but is preferably 20 μm or more and 200 μm or less.

[0060] Next, as shown in FIG. 8B, a conductive paste 2b' composed of conductive powder, a plasticizer, and a binder is filled into the via holes 10h'. Note that ceramic powder constituting 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 rates between the LTCC green sheet 10´ and the conductive paste 2b´ becomes small. As a result, it is possible to prevent cracks and the like from occurring during firing of the LTCC green sheet 10´ and the conductive paste 2b´.

[0061] <Electrode Pattern Forming Process of LTCC Green Sheet> FIG. 9 is a process diagram schematically showing an example of an electrode pattern forming process of 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. 9, an electrode pattern 2a´ is printed on the surface of the LTCC green sheet 10´ using a conductive paste composed of a conductive powder, a plasticizer, and a binder. As the printing method, screen printing, inkjet, gravure printing, or the like can be adopted. Note that ceramic powder constituting the LTCC green sheet 10´ may be added to the conductive paste for forming the electrode pattern 2a´. When the conductive paste for forming the electrode pattern 2a´ contains such ceramic powder, the difference in shrinkage rates between the LTCC green sheet l0´ and the electrode pattern 2a´ becomes small. As a result, it is possible to prevent cracks and the like from occurring during firing of the LTCC green sheet 10´ and the electrode pattern 2a´.

[0062] Note that in a later process, a plurality of LTCC green sheets 10´ are laminated to form a laminate. In the laminate, among the electrode patterns 2a´ of the LTCC green sheet 10´ located on the outermost layer, some electrode patterns (indicated by reference numeral "31´" in FIG. ) become the first electrodes connected to the interlayer connection conductors in the manufactured laminated substrate. In addition, the LTCC green sheet 10´ on which the electrode pattern 31´ is formed becomes a ceramic substrate that contacts the first main surface of the first thermoplastic resin layer in the manufactured laminated substrate.

[0063] <Coating Process of Paste for Protective Layer Containing Ceramic Material> FIG. 10 is a process diagram schematically showing an example of a step of applying a paste for a protective layer containing a ceramic material in a method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 10, a paste 40' for a protective layer is applied to the contour of the electrode pattern 31'. The paste 40' for the protective layer is preferably made of the same material as the LTCC green sheet 10'. If the paste 40' for the protective layer is made of the same material as the LTCC green sheet 10', the shrinkage rate during firing will be the same, so cracking during firing of the paste 40' for the protective layer and the LTCC green sheet 10' can be prevented.

[0064] The thickness of the paste 40' for the protective layer is preferably 2 μm or more and 10 μm or less. If the thickness of the paste for the protective layer is less than 2 μm, the first electrode formed through subsequent steps is likely to lift up. If the thickness of the paste for the protective layer exceeds 10 μm, the protective layer formed in subsequent steps will become thick. Therefore, when laminating the first thermoplastic resin layer and the ceramic layer in subsequent steps, the protective layer becomes an obstacle, and a gap is likely to occur between the interlayer connection conductor and the first electrode. Also, if the thickness of the paste for the protective layer exceeds 10 μm, the protective layer formed in subsequent steps will become thick. Therefore, when an intermetallic compound is formed in subsequent steps, the liquid-phase reaction is less likely to exceed the protective layer, and it becomes difficult for the intermetallic compound to be formed so as to contact the coating surface on the inner end side of the protective layer.

[0065] The paste 40' for the protective layer preferably covers a range of 30 μm or more and 100 μm or less from the contour of the electrode pattern 31' to the inside. By forming the paste 40' for the protective layer within such a range, it is possible to prevent the first electrode 31 formed through subsequent steps from lifting up.

[0066] <LTCC green sheet lamination step> FIG. 11 is a process diagram schematically showing an example of the LTCC green sheet lamination process in the method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in FIG. 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 according to the design. Thereafter, the LTCC green sheet laminate 2' is placed in a mold and crimped. The pressure and temperature are preferably set arbitrarily according to the design.

[0067] <LTCC Green Sheet Laminate Firing Process> FIG. 12 is a process diagram schematically showing an example of the LTCC green sheet laminate firing process in the method for manufacturing a laminated substrate 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. By performing this process, the conductive paste 2b' is fired into the via 2b, and the electrode pattern 2a' is fired into the electrode pattern 2a and the first electrode 31. For firing, a firing furnace such as a batch furnace or a belt furnace can be used. The firing conditions are not particularly limited, but it is preferable that the temperature be 850°C or higher and 1050°C or lower, and the time be 60 minutes or longer and 180 minutes or shorter. In addition, when the conductive paste 2b' or the electrode pattern 2a' contains copper (Cu), it is preferable to fire in a reducing atmosphere.

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

[0069] <Electrode Pattern Forming Process of Thermoplastic Resin Layer> Figures 14A and 14B are schematic process diagrams illustrating an example of the electrode pattern formation process of a thermoplastic resin layer in a method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 14A, a metal foil 3a' is laminated onto the main surface of the thermoplastic resin layer 20. Then, as shown in Figure 14B, the metal foil 3a' is patterned by etching or the like to form an electrode pattern 3a. Examples of metal foil 3a' include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), and alloys thereof. Furthermore, it is preferable that one main surface of the metal foil 3a' is a shiny surface and the other is a matte surface. It is preferable that the metal foil 3a' is 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 process, the multiple thermoplastic resin layers 20 are laminated together to form a laminate. In this laminate, the outermost thermoplastic resin layer 20 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 the interlayer connecting conductor in the manufactured laminated substrate.

[0071] <Via hole filling process for thermoplastic resin layer> Figures 15A and 15B are schematic process diagrams illustrating an example of the via hole filling process in the thermoplastic resin layer of a method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 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 layers 20, respectively. The method for forming these via holes is not particularly limited and they can be formed using mechanical punches, CO2 lasers, UV lasers, etc. After forming these via holes, it is preferable to perform desmear treatment such as oxygen plasma treatment, corona discharge treatment, or potassium permanganate treatment. The opening diameters of via holes 21h, 22h, and 20h are not particularly limited, but are preferably between 20 μm and 200 μm. Note that in Figure 15A, for the convenience of showing the internal structure in plan view, there are areas where via holes are formed directly below the electrode pattern 3a and appear not to be formed as through holes. However, in reality, the formation positions of the electrode pattern 3a and the via holes are offset in the depth direction, and the via holes are formed as through holes.

[0072] Next, as shown in Figure 15B, via holes 21h, 22h, and 20h are filled with conductive paste 50', which is a precursor for the interlayer connecting 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 higher melting point than the first metal powder. Preferably, the first metal powder contained in the conductive paste 50' consists of Sn or a Sn alloy, and the second metal powder consists of a Cu-Ni alloy or a Cu-Mn alloy. As such a conductive paste 50', for example, the conductive paste described in Japanese Patent Publication No. 5146627 can be used. Hereinafter, the metal component contained in the first metal powder will also be referred to as the first metal, and the metal component contained in the second metal powder will also be referred to as the second metal.

[0074] Examples of Sn or Sn alloys include elemental 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. Sn alloys preferably contain 70% by weight or more of Sn, and more preferably 85% by weight 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. Similarly, the proportion of Mn in the Cu-Mn alloy is preferably 10% by weight or more and 15% by weight or less. This ensures that a sufficient amount of Ni or Mn is supplied to form the desired intermetallic compound. If the ratio of Ni in the Cu-Ni alloy and the ratio of Mn in the Cu-Mn alloy are less than 10% by weight, Sn is more likely to remain without forming an intermetallic compound. Similarly, if the ratio of Ni in the Cu-Ni alloy and the ratio of Mn in the Cu-Mn alloy exceed 15% by weight, Sn is also more likely to remain without forming an intermetallic compound.

[0076] Furthermore, Cu-Ni alloys or Cu-Mn alloys may contain both Mn and Ni, and may also contain a third component such as P.

[0077] The arithmetic mean particle sizes of the first and second metal powders are preferably 3 μm or more and 10 μm or less, respectively. If the average particle size of these metal powders is too small, the manufacturing cost will increase. Also, oxidation of the metal powder will progress, making it easier to inhibit the reaction. On the other hand, if the average particle size of these metal powders is too large, it will be difficult to fill each via hole with the conductive paste 50'.

[0078] The proportion of the second metal in the metal component of the conductive paste 50' is preferably 30% by weight or more. That is, the proportion of the first metal in the metal component 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, can be further reduced, and the proportion of intermetallic compounds can be increased.

[0079] The proportion of metal components 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 low-viscosity conductive paste 50' with excellent filling properties. On the other hand, if the metal component is less than 70% by weight, flux components tend to remain.

[0080] The conductive paste 50' preferably contains a flux component. Various known flux components commonly used in conductive pastes can be used as the flux component, and it may contain a resin. Other components include, for example, a vehicle, solvent, thixotropic agent, and activator.

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

[0082] Examples of the above-mentioned vehicles include rosin-based resins, synthetic resins, or mixtures thereof, which consist of rosin and derivatives thereof such as modified rosin. Examples of rosin-based resins consisting of rosin and derivatives thereof such as modified rosin include gum rosin, tall rosin, wood rosin, polymerized rosin, hydrogenated rosin, formylated rosin, rosin esters, rosin-modified maleic acid resins, rosin-modified phenolic resins, rosin-modified alkyd resins, and various other rosin derivatives. Examples of synthetic resins consisting of rosin and derivatives thereof such as modified rosin include polyester resins, polyamide resins, phenoxy resins, terpene resins, and the like.

[0083] Known solvents include alcohols, ketones, esters, ethers, aromatics, hydrocarbons, and others. 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. Preferably, terpineol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether are used.

[0084] Specific examples of the above-mentioned thixotropic agents include hydrogenated castor oil, carnauba wax, amides, hydroxy fatty acids, dibenzylidene sorbitol, bis(p-methylbenzylidene) sorbitols, beeswax, stearic acid amide, and hydroxystearate ethylenebisamide. In addition, these can be used as thixotropic agents if they contain fatty acids such as caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, as well as hydroxy fatty acids such as 1,2-hydroxystearic acid, antioxidants, surfactants, and amines, as needed.

[0085] Examples of the above-mentioned activators include amine hydrohalides, organic halogen compounds, organic acids, organic amines, and polyhydric alcohols.

[0086] Examples of the above-mentioned 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 above-mentioned organic halogen compounds include paraffin chloride, 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 above-mentioned 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 above-mentioned organic amines include monoethanolamine, diethanolamine, triethanolamine, tributylamine, aniline, and diethylaniline.

[0090] Examples of the polyhydric alcohols mentioned above include erythritol, pyrogallol, and ribitol.

[0091] <Lamination process of thermoplastic resin layer> Figure 16 is a schematic process diagram showing an example of the thermoplastic resin layer lamination process in the manufacturing method of a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 16, the first thermoplastic resin layer 21, the second thermoplastic resin layer 22, and the other thermoplastic resin layers 20 are laminated to form a multilayer thermoplastic resin layer 3.

[0092] <Lamination process of multilayer ceramic layer and multilayer thermoplastic resin layer> Figures 17A and 17B are schematic process diagrams illustrating an example of the lamination process of a multilayer ceramic layer and a multilayer thermoplastic resin layer in a method for manufacturing a laminated substrate according to the fifth embodiment of the present invention. Next, as shown in Figure 17A, a multilayer ceramic layer 2 is laminated on top of the multilayer thermoplastic resin layer 3. At this time, the conductive paste 50' filled in the first thermoplastic resin layer 21 of the multilayer thermoplastic resin layer 3 is positioned so that it contacts the exposed surface of the first electrode 31 of the ceramic layer 11 located on the outermost layer of the multilayer ceramic layer 2.

[0093] Subsequently, as shown in Figure 17B, the multilayer thermoplastic resin layer 3 and the multilayer ceramic layer 2 are integrated by applying pressure and heating. In this process, the first thermoplastic resin layer 21 conforms to the surface irregularities of the ceramic layer 11, and the multilayer thermoplastic resin layer 3 and the multilayer ceramic layer 2 adhere tightly together due to the anchoring effect.

[0094] In this process, for example, one method is to process the material at a temperature of 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 connecting conductor 50. Furthermore, the interlayer connecting conductor 50 and the first electrode 31 are connected by liquid-phase diffusion bonding. In this process, an intermetallic compound 61 is formed between the interlayer connecting conductor 50 and the first electrode 31.

[0096] This liquid-phase diffusion bonding will be explained using diagrams. Figures 18A to 18D are schematic diagrams illustrating an example of connection between an interlayer conductor and a first electrode by liquid-phase diffusion bonding.

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

[0098] As shown in Figure 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 liquid phase of the first metal 51a.

[0099] Subsequently, as further heating continues, as shown in Figure 18C, the liquid phase of the first metal 51a reacts with the second metal powder 52 to form an intermetallic compound 60. Furthermore, the liquid phase first metal 51a spreads diffusively around the first electrode 31, and the liquid phase first metal 51a reacts with the metal constituting the first electrode 31 to form an intermetallic compound 61.

[0100] Subsequently, as heating ends and the temperature drops, the liquid-phase first metal 51a solidifies, forming the interlayer connecting conductor 50, as shown in Figure 18D. Note that in Figure 18D, for convenience, the outline of the intermetallic compound 60 derived from the second metal powder 52 is shown with a dashed line; however, in reality, the boundary is not clearly defined, and the intermetallic compound 60 does not appear as particulate matter.

[0101] Furthermore, in this process, since both the interlayer connecting conductor and the second electrode are connected by liquid-phase diffusion bonding, an intermetallic compound is also formed between the interlayer connecting conductor and the second electrode.

[0102] The laminated substrate 1 can be manufactured through the above process.

[0103] Furthermore, when manufacturing the laminated substrate of the present invention, by adjusting 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 of pressurization and heating temperature during the lamination process of the multilayer ceramic layer and the multilayer thermoplastic resin layer, an intermetallic compound with the shape shown in Figures 2 to 6 can be formed. In other words, by performing the above adjustments, a portion of the intermetallic compound can be brought into contact with the coating surface on the inner end side of the protective layer, and formed to be continuous with the intermetallic compound formed between the interlayer connecting conductor and the first electrode.

[0104] On the manufactured laminated substrate 1, electronic components such as IC chips and SMD components can be mounted by a reflow process or the like. After this reflow process, the laminated substrate 1 on which the electronic components are mounted may be washed and molded with resin. Further, the molded laminated substrate 1 may be singulated by dicing cut or laser cut or the like. Thereafter, a shield film may be formed on the surface of the mold resin. [Sixth Embodiment] Next, another manufacturing method of the laminated substrate of the present invention will be described. In the following description, a case where the ceramic layer is made of an LTCC material will be described. 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 <coating step of the paste for the protective layer containing the ceramic material> is not performed, and the following <protective layer arrangement step made of thermoplastic resin> is performed after the above <via hole filling step of the 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] FIG. 19 is a cross-sectional view schematically showing an example of the multilayer ceramic layer prepared in the manufacturing method of the laminated substrate according to the sixth embodiment of the present invention. Perform the <LTCC green sheet preparation step>, <via hole filling step of LTCC green sheet>, <electrode pattern forming step of LTCC green sheet>, <LTCC green sheet lamination step> and <LTCC green sheet laminate firing step> in the manufacturing method of the laminated substrate according to the fifth embodiment of the present invention in order to manufacture a multilayer ceramic layer 602 as shown in FIG. 19. The multilayer ceramic layer 602 has the same configuration as the multilayer ceramic layer 2, except that the protective layer 40 is not formed.

[0106] [Preparation of Multilayer Thermoplastic Resin Layer] FIG. 20 is a cross-sectional view schematically showing an example of the multilayer thermoplastic resin layer prepared in the manufacturing method of the laminated substrate according to the sixth embodiment of the present invention. The multilayer thermoplastic resin layer 3 is prepared by performing the <thermoplastic resin layer preparation step>, <thermoplastic resin layer electrode pattern formation step>, <thermoplastic resin layer via hole filling step>, and <thermoplastic resin layer lamination step> in the manufacturing method of the laminated substrate according to the fifth embodiment of the present invention described above.

[0107] <Protective layer placement process made of thermoplastic resin> Figure 21 is a schematic process diagram showing an example of a protective layer placement step made of thermoplastic resin in a method for manufacturing 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, and the multilayer thermoplastic resin layer 3 becomes a 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 contour of the first electrode 31 formed on the multilayer ceramic layer 602 during the subsequent lamination process of the multilayer ceramic layer and the multilayer thermoplastic resin layer. Such a position can be determined in advance through design.

[0108] <Lamination process of multilayer ceramic layer and multilayer thermoplastic resin layer> Figures 22A and 22B are schematic process diagrams illustrating an example of the lamination process of a multilayer ceramic layer and a multilayer thermoplastic resin layer in a method for manufacturing a laminated substrate according to the sixth embodiment of the present invention. Next, as shown in Figure 22A, a multilayer ceramic layer 2 is laminated on top of the 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 positioned so that it contacts the exposed surface of the first electrode 31 of the ceramic layer 11 located on the outermost layer of the multilayer ceramic layer 602.

[0109] Subsequently, as shown in Figure 22B, the multilayer thermoplastic resin layer 603 and the multilayer ceramic layer 602 are integrated by applying pressure and heating. Through the above process, a laminated substrate 601 in which the protective layer 640 is made of thermoplastic resin can be manufactured.

[0110] This specification contains the following information:

[0111] (1) The present disclosure is a laminated substrate comprising: a first thermoplastic resin layer having a first main surface and a second main surface facing the first main surface, and having via holes penetrating from the first main surface to the second main surface; a ceramic layer disposed in contact with the first main surface; and a second thermoplastic resin layer disposed 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 contour 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 disposed 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 a laminated substrate according to the present disclosure (1), wherein the protective layer has an inner end located inside the contour of the first electrode and a covering surface that contacts and covers at least a portion of the contour of the first electrode, and a portion of the intermetallic compound is in contact with the covering surface on the inner end side of the protective layer and is formed to be continuous with the intermetallic compound formed between the interlayer connecting conductor and the first electrode.

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

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

[0115] Disclosure (5) is a laminated substrate according to any of Disclosures (1) to (4), wherein in 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 connecting conductor. [Explanation of Symbols]

[0116] 1, 101, 201, 301, 401, 501, 601 Multilayer substrates 2,602 Multilayer ceramic layer 2' LTCC green sheet laminate Electrode patterns 2a, 2a', 3a 2b, 3b via 2b', 50' conductive paste 3, 603 multilayer thermoplastic resin layer 3a' Metal foil 10, 11 Ceramic layer 10' LTCC Green Sheet 10am, 9pm, 10pm, 3pm, 2pm, 4pm, Beer Hall 20 Thermoplastic resin layer 21, 321, 421 1st thermoplastic resin layer 21a, 321a, 421a First main surface of the first thermoplastic resin layer 21b Second main surface of the first thermoplastic resin layer 22 Second thermoplastic resin layer 31 1st electrode 31' Electrode Pattern 31c Contour of the first electrode 32 2nd electrode 40, 540, 640 protection layer 40' Protective layer paste 40a Protective layer coating surface 41 Inner edge of protective layer 50 Interlayer connecting conductors 51 First metal powder 51a Liquid phase first metal 52 Second metal powder 60, 61, 62, 161, 261 Intermetallic compounds 161a Part of intermetallic compounds 545 Stomata

Claims

1. A first thermoplastic resin layer having a first main surface and a second main surface opposite to the first main surface, and having via holes penetrating from the first main surface to the second main surface, A ceramic layer arranged to be in contact with the first main surface, The device comprises a second thermoplastic resin layer disposed in contact with the second main surface, A first electrode is formed on the main surface of the ceramic layer that is in contact with the first main surface, and a protective layer is formed so as to cover at least a portion of the contour of the first electrode. A second electrode is formed on the main surface of the second thermoplastic resin layer that is in contact with the second main surface. An interlayer connecting conductor connecting the first electrode and the second electrode is placed in the via hole. A laminated substrate in which an intermetallic compound is formed between the interlayer connecting conductor and the first electrode.

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

3. The laminated substrate according to claim 1 or 2, wherein the protective layer is made of the same material as the material constituting the ceramic layer.

4. The laminated substrate according to claim 1 or 2, wherein the protective layer is made of the same material as the material constituting the first thermoplastic resin layer.

5. The laminated substrate according to claim 1 or 2, wherein in 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 connecting conductor.

Images