Composite substrate

Abstract

Provided is a composite substrate in which delamination at a bonding interface between a ceramic substrate and a resin substrate and the occurrence of cracks in the resin substrate are reduced. This composite substrate comprises a resin substrate 20 and a low-temperature fired ceramic 10 bonded to the resin substrate 20 in a thickness direction. The low-temperature fired ceramic 10 is a substantially rectangular parallelepiped having a first main surface 10a, a second main surface 10b facing the first main surface 10a, and side surfaces 10c connecting the first main surface 10a and the second main surface 10b. The first main surface 10a is directly bonded to the resin substrate 20, the corners from the first main surface 10a to the side surfaces 10c are rounded with a radius R1, the corners of the adjacent side surfaces 10c are rounded with a radius R2, and the radius R2 is larger than the radius R1.

Description

Composite PCB

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

[0002] In recent years, wireless communication modules used in wireless communication devices, primarily mobile devices such as mobile phones, have become more sophisticated, and as a result, the mounting area within the housing has been shrinking, resulting in a demand for smaller, thinner wireless communication modules.

[0003] For example, Patent Document 1 discloses an antenna module in which a ceramic dielectric such as LTCC equipped with a patch antenna is joined to a resin substrate with a solder layer. This antenna module has a high resistance of the solder layer, which results in poor antenna characteristics, and the module height increases by the thickness of the solder layer, which is disadvantageous for miniaturization.

[0004] As a means for solving this problem, for example, Patent Document 2 discloses a laminated circuit board in which a ceramic laminated board and a resin multilayer board are integrated together.

[0005] US Patent No. 11670870 JP 2020-047688 A

[0006] When a structure in which a resin multilayer substrate and a ceramic substrate are directly bonded is manufactured by thermocompression bonding, the resin multilayer substrate may warp after cooling, causing delamination at the interface between the ceramic substrate and the resin multilayer substrate, or cracks may occur in the resin multilayer substrate.

[0007] In view of the above, an object of the present invention is to provide a composite substrate that is less susceptible to delamination at the bonding interface between the ceramic substrate and the resin substrate and to cracking in the resin substrate.

[0008] One aspect of the composite substrate of the present invention comprises a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in the thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface, and the first main surface is directly bonded to the resin substrate. Corners from the first main surface to the side surface are rounded with a radius R1, and the corners of the adjacent side surfaces are rounded with a radius R2, and the radius R2 is greater than the radius R1.

[0009] Another aspect of the composite substrate of the present invention comprises a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in the thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, and the first main surface is directly bonded to the resin substrate, and a chamfered portion is formed with a chamfered corner extending from the first main surface to the side surface, and a raised portion is formed in which the resin of the resin substrate is raised from the first main surface to the side surface including the chamfered portion.

[0010] According to the present invention, it is possible to provide a composite substrate that is less susceptible to delamination at the bonding interface between the ceramic substrate and the resin substrate and to cracks in the resin substrate.

[0011] FIG. 1A is a cross-sectional view schematically showing an example of a composite substrate according to a first embodiment of the present invention. FIG. 1B is a plan view of the composite substrate of FIG. 1A. FIG. 2A is a cross-sectional view schematically showing another example of a composite substrate according to the first embodiment of the present invention. FIG. 2B is a partially enlarged view of the dotted line portion A of the composite substrate of FIG. 2A. FIG. 3 is a plan view schematically showing an example of a composite substrate according to a second embodiment of the present invention. FIG. 4A is a cross-sectional view schematically showing an example of a composite substrate according to a third embodiment of the present invention. FIG. 4B is a plan view of the composite substrate of FIG. 4A. FIG. 5A is a cross-sectional view schematically showing an example of a composite substrate according to a fourth embodiment of the present invention. FIG. 5B is a plan view of the composite substrate of FIG. 5A. FIG. 6 is a process diagram schematically showing an example of an LTCC green sheet cutting step in a manufacturing process for a composite substrate according to the present invention. FIG. 7 is a process diagram schematically showing another example of an LTCC green sheet cutting step in a manufacturing process for a composite substrate according to the present invention. FIG. 8 is a process diagram schematically showing an example of a bonding step between a low-temperature co-fired ceramic and a resin substrate in a manufacturing process for a composite substrate according to the present invention. FIG. 9 is a process diagram schematically showing an example of a resin substrate cutting process in the manufacturing process of the composite substrate of the present invention. FIG. 10 is a cross-sectional view schematically showing an example of an antenna module using the composite substrate of the present invention. FIG. 11 is a cross-sectional view schematically showing another example of an antenna module using the composite substrate of the present invention. FIG. 12 is a partially enlarged view of an antenna module using the composite substrate of the present invention. FIG. 13 is a schematic view of an antenna module using the composite substrate of the present invention mounted on a motherboard. FIG. 14 is a schematic view of another antenna module using the composite substrate of the present invention mounted on a motherboard. FIG. 15A is a cross-sectional view schematically showing an example of a composite substrate according to the fifth embodiment of the present invention. FIG. 15B is a partially enlarged view of the dotted line portion B of the composite substrate in FIG. 15A. FIG. 16A is a cross-sectional view schematically showing an example of a composite substrate according to the sixth embodiment of the present invention and an antenna module using the composite substrate. FIG. 16B is a partially enlarged view of the dotted line portion C of the composite substrate in FIG. 16A. FIG. 17A is a process diagram schematically showing an example of a manufacturing process of low-temperature co-fired ceramic used in the composite substrate of the sixth embodiment. FIG. 17B is a process diagram schematically showing an example of a manufacturing process for the low-temperature co-fired ceramic used in the composite substrate of the sixth embodiment.Fig. 17C is a process diagram schematically showing an example of a manufacturing process of low-temperature co-fired ceramic used in the composite substrate of the sixth embodiment. Fig. 18A is a process diagram schematically showing an example of a manufacturing process of the composite substrate of the fifth and sixth embodiments. Fig. 18B is a process diagram schematically showing an example of a manufacturing process of the composite substrate of the fifth and sixth embodiments. Fig. 18C is a process diagram schematically showing an example of a manufacturing process of the composite substrate of the fifth and sixth embodiments.

[0012] The composite substrate of the present invention will be described below. Note that the present invention is not limited to the following configurations, and may be modified as appropriate within the scope of the present invention. In addition, a combination of multiple individual preferred configurations described below also constitutes the present invention. Preferred embodiments of the composite substrate of the present invention will be described below with reference to the drawings.

[0013] [First embodiment to fourth embodiment] The composite substrate according to the first embodiment to the fourth embodiment is a composite substrate according to one aspect of the composite substrate of the present invention, and includes a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in the thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface, and the first main surface is directly bonded to the resin substrate, and corners from the first main surface to the side surface are rounded with a radius R1, and the corners of the adjacent side surfaces are rounded with a radius R2, and the radius R2 is greater than the radius R1.

[0014] A composite 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 the composite substrate according to the first embodiment of the present invention. Fig. 1B is a plan view of the composite substrate of Fig. 1A.

[0015] In this specification, the length direction, thickness direction, and width direction are defined as directions defined by L, T, and W, respectively, as shown in Fig. 1A etc. The length direction L, thickness direction T, and width direction W are perpendicular to one another. Furthermore, a direction perpendicular to the thickness direction T and including the length direction L and width direction W is defined as a planar direction (LW planar direction).

[0016] The composite substrate 100 includes a low-temperature co-fired ceramic (LTCC) 10 and a resin substrate 20. As shown in FIGS. 1A and 1B , the low-temperature co-fired ceramic 10 is a substantially rectangular parallelepiped having a first main surface 10a, a second main surface 10b opposite to the first main surface 10a, and a side surface 10c connecting the first main surface 10a and the second main surface 10b. The low-temperature co-fired ceramic 10 may also be substantially cubic. As shown in FIG. 1B , the low-temperature co-fired ceramic 10 is a substantially rectangular shape having a length dimension L1 and a width dimension W1 when viewed in the thickness direction T.

[0017] The low-temperature co-fired ceramic 10 is bonded to the resin substrate 20 in the thickness direction T. The first main surface 10a of the low-temperature co-fired ceramic 10 is directly bonded to the resin substrate 20.

[0018] As shown in Fig. 1A, the low-temperature co-fired ceramic 10 has corners rounded at a radius R1 from the first main surface 10a to the side surface 10c. Preferably, the low-temperature co-fired ceramic 10 is rounded at a radius R1 from the entire outer edge of the first main surface 10a to the thickness direction T. As shown in Fig. 1A, the low-temperature co-fired ceramic 10 has a constant radius R1. The radius R1 does not have to be constant, but is preferably constant.

[0019] 1A , the low-temperature co-fired ceramic 10 also has corners rounded at a radius R1 from the second main surface 10b to the side surface 10c. Preferably, the low-temperature co-fired ceramic 10 is rounded at a radius R1 from the entire outer edge of the second main surface 10b in the thickness direction T. The rounding of the corners from the second main surface 10b to the side surface 10c may be of any size, but is preferably radius R1.

[0020] As shown in Fig. 1B, the low-temperature co-fired ceramic 10 has corners of adjacent side surfaces 10c that are rounded with a radius R2. The low-temperature co-fired ceramic 10 is a substantially rectangular parallelepiped and has four side surfaces 10c, with the four corners rounded with a radius R2. As shown in Fig. 1B, the low-temperature co-fired ceramic 10 has a constant radius R2. The radius R2 does not have to be constant, but is preferably constant.

[0021] The low-temperature co-fired ceramic 10 has a radius R2 greater than the radius R1. Since the radius R2 is greater than the radius R1, delamination at the bonding interface between the low-temperature co-fired ceramic and the resin substrate and cracks in the resin substrate are less likely to occur.

[0022] The size of R1 is not particularly limited, but is preferably 0.020 mm or more and 0.400 mm or less. The size of R2 is not particularly limited, but is preferably 0.500 mm or more and 1.20 mm or less. When R1 and R2 are each within the above ranges, delamination at the bonding interface between the low-temperature co-fired ceramic and the resin substrate and cracks in the resin substrate are less likely to occur. The sizes of R1 and R2 can be determined by exposing each corner by cross-section polishing and then measuring the length using known methods such as a microscope or metallurgical microscope.

[0023] The ratio of the radius R2 to the radius R1 is not particularly limited, but it is preferable that the radius R2 / radius R1 is 1.1 or more and 50 or less, for example.

[0024] The resin substrate 20 is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and side surfaces connecting the first and second main surfaces. As shown in FIG. 1B , the resin substrate 20 is substantially rectangular, having a length L2 and a width W2 when viewed in the thickness direction T. The length L2 and width W2 are greater than the length L1 and width W1 of the low-temperature co-fired ceramic 10, respectively. The difference between the length L1 and L2 is not particularly limited, but is preferably, for example, 0.1 mm or more and 2.0 mm or less. The difference between the width W1 and W2 is not particularly limited, but is preferably, for example, 0.1 mm or more and 2.0 mm or less.

[0025] 1B , the resin substrate 20 has a rectangular shape with rounded corners when viewed from the thickness direction T. The resin substrate 20 does not need to have rounded corners, and may have a rectangular or square shape when viewed from the thickness direction T.

[0026] In the composite substrate 100, the thickness T1 of the low-temperature co-fired ceramic 10 and the thickness T2 of the resin substrate 20 are the same. The thicknesses T1 and T2 may be different.

[0027] Low-temperature co-fired ceramic (LTCC) materials are examples of materials that can be used to form low-temperature co-fired ceramics. 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, and 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 fired 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 ceramic materials include non-glass-based low-temperature fired ceramic materials using ceramic powders.

[0028] The thermal expansion coefficient of the low-temperature co-fired ceramic in the thickness direction T and in the LW plane direction (also referred to as the thermal expansion coefficient in the plane direction) is, for example, 1 ppm / ° C. or more and 20 ppm / ° C. or less, respectively. The thermal expansion coefficient is a value measured by thermomechanical analysis (TMA).

[0029] The resin forming the resin substrate may be either a thermosetting resin or a thermoplastic resin. Examples of thermosetting resins include phenolic resin, epoxy resin, polyester resin, silicone resin, and polyimide resin. Examples of thermoplastic resins include thermoplastic liquid crystal polymer (LCP), thermoplastic polyimide resin, polyether ether ketone resin (PEEK), and polyphenylene sulfide resin (PPS). Among these, thermoplastic resins are preferred, and liquid crystal polymer (LCP) is more preferred. Thermoplastic resins regain their plasticity upon heating, making them particularly suitable for forming the raised resin portions described below. Liquid crystal polymers have a lower water absorption rate than other thermoplastic resins, preventing variations in electrical properties and reduced electrical connection reliability.

[0030] The resin may have a thermal expansion coefficient in the thickness direction T of 10 ppm / °C or more, or 200 ppm / °C or more. The upper limit of the thermal expansion coefficient in the thickness direction T is not particularly limited, but is, for example, 300 ppm / °C or less. The resin may have a thermal expansion coefficient in the LW plane direction (also referred to as the thermal expansion coefficient in the plane direction) of 5 ppm / °C or more, or 10 ppm / °C or more. The upper limit of the thermal expansion coefficient in the LW plane direction is not particularly limited, but is, for example, 100 ppm / °C or less.

[0031] Next, a modified example of the composite substrate according to the first embodiment of the present invention will be described with reference to Figures 2A and 2B. Figure 2A is a cross-sectional view schematically showing another example of the composite substrate according to the first embodiment of the present invention. Figure 2B is a partially enlarged view of the dotted line portion A of the composite substrate in Figure 2A.

[0032] 2A and 2B , the resin of the resin substrate 20 is raised in the thickness direction T at the joint end with the low-temperature co-fired ceramic 10. The raised portion 20a, which is the raised portion of the resin, extends from the first main surface 10a to the middle of the curve from the first main surface 10a to the side surface 10c of the low-temperature co-fired ceramic 10. The raised portion 20a is formed along the entire outer edge of the first main surface 10a of the low-temperature co-fired ceramic 10.

[0033] It is preferable that a raised portion 20 a is formed in the composite substrate 100. When the raised portion 20 a is formed, the resin forming the resin substrate 20 is preferably a thermoplastic resin. The raised portion 20 a can suppress delamination at the bonding interface between the low-temperature co-fired ceramic and the resin substrate and the occurrence of cracks in the resin substrate, even if the thermal expansion coefficient in the thickness direction T of the resin forming the resin substrate 20 is 200 ppm / °C or higher.

[0034] Next, a composite substrate according to a second embodiment of the present invention will be described with reference to Fig. 3. Only the differences from the composite substrate 100 according to the first embodiment will be described, and a description of the common features will be omitted.

[0035] 3 is a plan view schematically illustrating an example of a composite substrate according to a second embodiment of the present invention. As shown in FIG. 3, the resin substrate 20 of the composite substrate 110 has a composite portion 25 that overlaps with the low-temperature co-fired ceramic 10 and an extension portion 26 that does not overlap with the low-temperature co-fired ceramic 10.

[0036] The composite portion 25 has the same shape as the resin board 20 in the first embodiment.

[0037] As shown in FIG. 3 , the extension portion 26 is a substantially rectangular shape with a portion thereof protruding in the width direction W from the composite portion 25. The extension portion 26 has a dimension X in the length direction L and a dimension Y in the width direction W. The dimension X of the extension portion 26 is approximately 1 / 3 of the length dimension L2 of the resin substrate 20. The dimension X of the extension portion 26 may be approximately 1 / 5 to 1 / 2 of the length dimension L2 of the resin substrate 20. The dimension Y of the extension portion 26 is approximately the same as the width dimension W2 of the resin substrate 20. The dimension Y of the extension portion 26 is not particularly limited as long as it is 1 / 3 or more of the width dimension W2 of the resin substrate 20.

[0038] The extension portion 26 may partially protrude from the composite portion 25 in the length direction L. The composite substrate 110 has one extension portion 26. Two or more extension portions 26 may be provided, but one extension portion is preferred.

[0039] As shown in FIG. 3, the composite portion 25 also has a region that does not overlap with the low-temperature co-fired ceramic 10 around the region that overlaps with the low-temperature co-fired ceramic 10, but this region that does not overlap with the low-temperature co-fired ceramic 10 is not an extension portion.

[0040] The corners of the extension 26 are rounded when viewed in the thickness direction T. The corners of the extension 26 do not have to be rounded.

[0041] The resin substrate 20 of the composite substrate 110 may or may not have a protrusion of resin in the thickness direction T at the joint end portion with the low-temperature co-fired ceramic 10 .

[0042] Next, a composite substrate according to a third embodiment of the present invention will be described with reference to Figures 4A and 4B. Only differences from the composite substrate 100 according to the first embodiment will be described, and descriptions of common features will be omitted.

[0043] Fig. 4A is a cross-sectional view schematically illustrating an example of a composite substrate according to a third embodiment of the present invention. Fig. 4B is a plan view of the composite substrate of Fig. 4A. In the composite substrate 120, the length dimension L1 and width dimension W1 of the low-temperature co-fired ceramic 10 are the same as the length dimension L2 and width dimension W2 of the resin substrate 20. When viewed from the thickness direction T, the resin substrate 20 has rectangular corners that are rounded with a radius R2. When viewed from the thickness direction T, the resin substrate 20 may also have a rectangular shape with unrounded corners.

[0044] In the resin substrate 20 of the composite substrate 120, the resin does not bulge in the thickness direction T at the joint end with the low-temperature co-fired ceramic 10, but the resin may bulge in the thickness direction T.

[0045] Next, a composite substrate according to a fourth embodiment of the present invention will be described with reference to Figures 5A and 5B. Only differences from the composite substrate 100 according to the first embodiment will be described, and a description of common features will be omitted.

[0046] FIG. 5A is a cross-sectional view schematically illustrating an example of a composite substrate according to a fourth embodiment of the present invention. FIG. 5B is a plan view of the composite substrate of FIG. 5A. As shown in FIGS. 5A and 5B, in the composite substrate 130, the length dimension L1 and width dimension W1 of the low-temperature co-fired ceramic 10 are larger than the length dimension L2 and width dimension W2 of the resin substrate 20. The resin substrate 20 has a substantially rectangular shape with rounded corners when viewed from the thickness direction T and is similar in shape to the low-temperature co-fired ceramic 10. The resin substrate 20 is smaller than the low-temperature co-fired ceramic 10 and has the same center position as the low-temperature co-fired ceramic 10 when viewed from the thickness direction T, so the resin substrate 20 does not appear in FIG. 5B. The resin substrate 20 may also have a rectangular shape without rounded corners when viewed from the thickness direction T.

[0047] Next, an example of a method for producing a composite substrate of the present invention will be described.

[0048] <LTCC Green Sheet Preparation Step> First, a low-temperature fired ceramic material, a binder, and a plasticizer are mixed in desired amounts to prepare a slurry. The low-temperature fired ceramic material may be any of the materials listed above as constituting low-temperature fired ceramics. Conventionally known binders and plasticizers may be used.

[0049] Next, the slurry is applied to a carrier film and formed into a sheet to obtain an LTCC green sheet. The slurry can be applied using a lip coater, a doctor blade, or the like. In this case, it is preferable that the thickness of the LTCC green sheet is 5 μm or more and 100 μm or less.

[0050] <LTCC Green Sheet Lamination Process> Next, multiple LTCC green sheets are laminated to form an LTCC green sheet laminate. The number of layers can be determined appropriately depending on the design. The compositions of the multiple LTCC green sheets may be the same or different, but are preferably the same. The LTCC green sheet laminate is then placed in a mold and pressure-bonded. The pressure and temperature can be set as desired depending on the design.

[0051] 6 is a process diagram schematically illustrating an example of an LTCC green sheet cutting step in the manufacturing process of the composite substrate of the present invention. As shown in FIG. 6, the LTCC green sheet laminate 30 is cut with a laser along cutting line CL1 to produce pre-fired pieces 31 of low-temperature co-fired ceramic. At this time, the LTCC green sheet laminate 30 is cut so that the corners of adjacent side surfaces of the low-temperature co-fired ceramic are rounded with a radius R2 after firing.

[0052] Next, the pre-fired pieces 31 are subjected to barrel processing or the like to process them so that after firing, the corners between the first main surface and the side surface of the low-temperature fired ceramic and the corners between the second main surface and the side surface are rounded with a radius R1, thereby obtaining unfired low-temperature fired ceramic.

[0053] FIG. 7 is a process diagram schematically illustrating another example of an LTCC green sheet cutting process in the manufacturing process of the composite substrate of the present invention. Another method for cutting the LTCC green sheet laminate 30 into pre-fired pieces 31 includes the following method. First, as shown in the upper diagram of FIG. 7 , cutting is performed along the cutting line CL2 with a laser. The cutting line CL2 is a rounded shape with a radius R2 formed at the corner of adjacent side surfaces of the low-temperature co-fired ceramic. Next, as shown in the lower diagram of FIG. 7 , the straight portion (cutting line CL3) that will become the side surface is cut. The cutting line CL3 can be cut using a general-purpose method such as dicing. This method can shorten processing time and reduce costs compared to cutting entirely with a laser. After producing the pre-fired pieces 31, barrel processing or the like is performed in the same manner as described above to obtain unfired low-temperature co-fired ceramic.

[0054] <LTCC Firing Step> The unfired low-temperature fired ceramic obtained by the above procedure is fired to produce the low-temperature fired ceramic (LTCC) used in the composite substrate of the present invention. 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 a temperature of 800°C or higher and 1000°C or lower is preferred.

[0055] <Resin Sheet Preparation Step> Next, a plurality of resin sheets that will become the material for the resin substrate are prepared. Since the preferred material for the resin substrate has already been described, the description will be omitted here. The thickness of the resin sheet is preferably 10 μm or more and 100 μm or less.

[0056] <Laminating step of resin sheets> Next, resin sheets are laminated to prepare a resin substrate sheet. The number of laminated sheets can be determined appropriately depending on the design. The compositions of the multiple resin sheets may be the same or different, but are preferably the same. If necessary, the resin sheets may be laminated and placed in a mold to be pressure-bonded to prepare a resin substrate sheet.

[0057] <Step of Bonding Low-Temperature Co-fired Ceramic and Resin Substrate> Fig. 8 is a process diagram schematically illustrating an example of a step of bonding a low-temperature co-fired ceramic and a resin substrate in the manufacturing process of the composite substrate of the present invention. Next, as shown in Fig. 8, the fired low-temperature co-fired ceramic 10 is placed on a resin substrate sheet 40. At this time, the low-temperature co-fired ceramic 10 is placed so that the first main surface 10a of the low-temperature co-fired ceramic 10 is in contact with the surface of the resin substrate sheet 40.

[0058] The low-temperature fired ceramic and the resin substrate sheet are then heated and pressed together to integrate them. After bonding, the cooled resin substrate sheet typically warps. However, by rounding the corners of the low-temperature fired ceramic from the first main surface to the side surfaces with a radius R1 and rounding the corners of the adjacent side surfaces with a radius R2, delamination between the low-temperature fired ceramic and the resin substrate sheet and cracking of the resin substrate sheet are suppressed. This bonding process can be performed, for example, at a temperature of 230°C or higher and 350°C or lower and a pressure of 3 MPa or higher and 20 MPa or lower. When the resin forming the resin substrate is a thermosetting resin, the fired low-temperature fired ceramic is placed on an uncured resin substrate sheet and pressed together to harden the thermosetting resin, thereby integrating the low-temperature fired ceramic and the resin substrate sheet. The pressure pressing conditions are preferably lower in temperature and pressure than those of the bonding process in the composite substrate manufacturing methods of the fifth and sixth embodiments of the present invention, which will be described later.

[0059] When forming a raised portion on a resin substrate, a thermoplastic resin is used as the material of the resin substrate, and the heating temperature and / or pressure of the press are set high in this bonding step.

[0060] <Resin Substrate Cutting Process> Figure 9 is a process diagram schematically showing an example of a resin substrate cutting process in the manufacturing process of the composite substrate of the present invention. After bonding the low-temperature co-fired ceramic 10 and the resin substrate sheet 40, the resin substrate sheet 40 is cut along the cutting line CL4 with a laser from the back side of the surface bonded to the first main surface of the low-temperature co-fired ceramic 10. In Figure 9, (A) shows the composite substrate 100 of the first embodiment, (B) shows the composite substrate 120 of the third embodiment, and (C) shows the composite substrate 130 of the fourth embodiment.

[0061] The resin substrate conforms to the unevenness of the surface of the low-temperature co-fired ceramic, and the resin substrate and the low-temperature co-fired ceramic are closely attached to each other by an anchor effect. If the resin substrate and the low-temperature co-fired ceramic are directly bonded by thermocompression bonding, the resin substrate may warp after cooling, causing delamination at the interface between the low-temperature co-fired ceramic and the resin substrate, or cracks may occur in the resin substrate.

[0062] In the composite substrate of the present invention, the corners of the low-temperature co-fired ceramic in the thickness direction and planar direction are rounded on the surface that is directly bonded to the resin substrate, and the roundness in the planar direction is greater than the roundness in the thickness direction, i.e., the radius R2 is greater than the radius R1, which makes it easier to distribute stress at the joint end between the low-temperature co-fired ceramic and the resin substrate, and makes it possible to suppress delamination at the interface between the low-temperature co-fired ceramic and the resin substrate and the occurrence of cracks in the resin substrate.

[0063] Furthermore, if the resin of the resin substrate bulges in the thickness direction at the joint end with the low-temperature co-fired ceramic, stress is easily dispersed even if the thermal expansion coefficient in the thickness direction of the resin forming the resin substrate is large, and the occurrence of delamination and cracks can be suppressed.

[0064] The composite substrate of the present invention can be, for example, an antenna module equipped with a patch antenna.

[0065] Fig. 10 is a cross-sectional view showing a schematic example of an antenna module using the composite substrate of the present invention. As shown in Fig. 10, the antenna module 200 includes a low-temperature co-fired ceramic 10 formed by laminating a plurality of low-temperature co-fired ceramic layers 11 (nine layers in Fig. 10), a resin substrate 20 formed by laminating a plurality of resin layers 21 (five layers in Fig. 10), and a plurality of antennas 15 (three in Fig. 10) built into the low-temperature co-fired ceramic 10.

[0066] Electrode patterns 13, vias 14, and the like are formed on the low-temperature co-fired ceramic 10. The electrode patterns 13 are arranged at the interfaces between the low-temperature co-fired ceramic layers 11 and on the first main surface 10a of the low-temperature co-fired ceramic 10. The vias 14 are arranged to penetrate the low-temperature co-fired ceramic layers 11 and serve to electrically connect the antennas 15 and the electrode patterns 13 to each other, and to electrically connect the electrode patterns 13 on different layers to each other. In Figure 10, there are antennas 15 that are not connected to the vias 14, but they may be connected at a location other than this cross section.

[0067] Electrode patterns 23, vias 24, etc. are formed on the resin substrate 20. The electrode patterns 23 are arranged at the interfaces between the resin layers 21 and on the main surface of the resin substrate 20 on the side to which the low-temperature co-fired ceramic 10 is not bonded. The vias 24 are arranged to penetrate the resin layer 21 and serve to electrically connect the electrode patterns 23 to the electrode patterns 13 arranged on the first main surface 10a of the low-temperature co-fired ceramic 10, and to electrically connect the electrode patterns 23 on different layers to each other.

[0068] Fig. 11 is a cross-sectional view showing another example of an antenna module using the composite substrate of the present invention. As shown in Fig. 11, the antenna module 210 includes a low-temperature co-fired ceramic 10 formed by laminating a plurality of low-temperature co-fired ceramic layers 11 (nine layers in Fig. 11), a resin substrate 20 formed by laminating a plurality of resin layers 21 (five layers in Fig. 11), and a plurality of antennas 15 (two in Fig. 11) built into the low-temperature co-fired ceramic 10.

[0069] In the antenna module 210, the antenna 15 is connected to a plurality of vias 14 (two in FIG. 11).

[0070] The antenna module is manufactured, for example, as follows.

[0071] <LTCC Green Sheet Preparing Step> The LTCC green sheet preparing step can be carried out in the same manner as in the method for producing a composite substrate of the present invention.

[0072] <Step of filling via holes in LTCC green sheet> Next, via holes are formed in the LTCC green sheet. The method for forming the via holes is not particularly limited, and may be a mechanical punch, CO ２ It can be formed using a laser, a UV laser, or the like.

[0073] Next, the via holes are filled with a conductive paste P1 consisting of a conductive powder, a plasticizer, and a binder. The conductive powder preferably contains copper (Cu) and its alloys. The conductive powder may also contain silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), gold (Au), and alloys thereof.

[0074] <Step of Forming Electrode Pattern and Antenna on LTCC Green Sheet> Next, a pattern is printed on the surface of the LTCC green sheet using a conductive paste consisting of conductive powder, plasticizer, and binder. Printing methods that can be used include screen printing, inkjet printing, and gravure printing. The conductive paste is preferably the same as the conductive paste P1 filled in the via holes, but may be different. A patch antenna is then placed at a predetermined position on the surface of the LTCC green sheet.

[0075] <LTCC Green Sheet Laminating Step> and <LTCC Green Sheet Cutting Step> The LTCC green sheet laminating step and the LTCC green sheet cutting step can be performed in the same manner as in the method for producing a composite substrate of the present invention.

[0076] <LTCC firing step> The LTCC firing step can be performed in the same manner as in the manufacturing method of the composite substrate of the present invention. By performing this step, the conductive paste P1 filled in the via holes is fired to form vias, and the conductive paste pattern is fired to form an electrode pattern. Note that if the conductive paste contains copper (Cu), firing is preferably performed in a reducing atmosphere.

[0077] <Resin Sheet Preparing Step> The resin sheet preparing step can be carried out in the same manner as in the method for producing a composite substrate of the present invention.

[0078] <Step of forming an electrode pattern on a resin sheet> When the resin substrate is made of a thermoplastic resin, a metal foil is laminated on the main surface of the resin sheet. Then, the metal foil is patterned by etching or the like to form an electrode pattern. Examples of metal foil include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), stainless steel (SUS), and alloys thereof. When the resin substrate is made of a thermosetting resin, a conductive layer is formed on the main surface of the resin substrate sheet by successively performing electroless plating and electrolytic plating, and this conductive layer is then patterned to form an electrode pattern. Examples of plating include copper (Cu), silver (Ag), aluminum (Al), nickel (Ni), and alloys thereof.

[0079] <Step of filling via holes in resin sheet> Next, via holes are formed in the resin sheet. The method for forming the via holes is not particularly limited, and may be a mechanical punch, a CO ２ They can be formed using a laser, a UV laser, etc. After the via holes are formed, it is preferable to carry out a desmear treatment such as an oxygen plasma treatment, a corona discharge treatment, or a potassium permanganate treatment.

[0080] Next, the via holes are filled with a conductive paste P2, which is a precursor of the vias. The conductive paste P2 contains a first metal powder and a second metal powder having a higher melting point than the first metal powder. The first metal powder contained in the conductive paste P2 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 P2 include the conductive paste described in Japanese Patent No. 5146627.

[0081] The conductive paste P2 preferably contains a flux component. The flux component may be any of various known flux components commonly 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. The filling method is not particularly limited, but may include screen printing, vacuum printing, or the like.

[0082] <Step of Laminating Resin Sheets> The step of laminating resin sheets can be carried out in the same manner as in the method for producing a composite substrate of the present invention.

[0083] <Step of Bonding Low-Temperature Co-fired Ceramic to Resin Substrate> Next, the step of bonding the low-temperature co-fired ceramic to the resin substrate is performed in the same manner as in the method for manufacturing a composite substrate of the present invention. At this time, the conductive paste P2 filled in the resin substrate is aligned so as to contact the exposed surface of the electrode pattern arranged on the outermost layer of the low-temperature co-fired ceramic layer.

[0084] In this process, the conductive paste P2 melts and then solidifies to form vias.

[0085] Fig. 12 is a partially enlarged view of an antenna module using the composite substrate of the present invention. As shown in Fig. 12, at the interface between the low-temperature co-fired ceramic 10 and the resin substrate 20 of the antenna module, there are a portion (i) where the low-temperature co-fired ceramic 10 and the resin substrate 20 are bonded, a portion (ii) where the electrode pattern 13 of the low-temperature co-fired ceramic is bonded to the resin substrate 20, and a portion (iii) where the electrode pattern 13 of the low-temperature co-fired ceramic is bonded to a via 24 of the resin substrate 20.

[0086] In the above (i), as with the composite substrate, the resin substrate conforms to the unevenness of the surface of the low-temperature co-fired ceramic, bonding the resin substrate and the low-temperature co-fired ceramic by an anchor effect. In the above (ii), the unevenness of the electrode pattern on the surface of the low-temperature co-fired ceramic creates an anchor effect between the resin substrate and the resin substrate, resulting in bonding. In the above (iii), a metal such as Sn or an Sn alloy contained in the via of the resin substrate melts when heated during bonding and reacts with the metal (e.g., Cu) constituting the electrode pattern on the surface of the low-temperature co-fired ceramic, forming an alloy layer, bonding the resin substrate and the low-temperature co-fired ceramic and electrically connecting them.

[0087] The antenna module can be mounted on a motherboard, for example, as follows. Fig. 13 is a schematic diagram of an antenna module using the composite substrate of the present invention mounted on a motherboard. As shown in Fig. 13, the composite substrate 100 according to the first embodiment of the present invention is used in an antenna module 220. Solder 50 is provided between the motherboard 60 and an electrode pattern 23 arranged on the main surface of the resin substrate 20 on the side to which the low-temperature co-fired ceramic 10 is not bonded, thereby electrically connecting the antenna module 220 and the motherboard 60.

[0088] 14 is a schematic diagram showing another antenna module using the composite substrate of the present invention mounted on a motherboard. As shown in FIG. 14 , the composite substrate 110 according to the second embodiment of the present invention is used in the antenna module 230. In the extension portion 26 of the composite substrate 110, solder 50 and a connector 70 are provided between the electrode pattern 23 arranged on the main surface on the side where the low-temperature co-fired ceramic 10 is not bonded and the motherboard 60, thereby electrically connecting the antenna module 230 and the motherboard 60.

[0089]

[0033] The composite substrates according to the fifth to sixth embodiments are composite substrates according to other aspects of the composite substrate of the present invention, and include a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in the thickness direction, the low-temperature co-fired ceramic being a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, the first main surface being directly bonded to the resin substrate, a chamfered portion having a chamfered corner extending from the first main surface to the side surface, and a raised portion in which the resin of the resin substrate is raised from the first main surface to the side surface including the chamfered portion.

[0090] A composite substrate according to a fifth embodiment of the present invention will now be described. FIG. 15A is a cross-sectional view schematically illustrating an example of a composite substrate according to the fifth embodiment of the present invention. FIG. 15B is a partially enlarged view of the dotted line B in the composite substrate of FIG. 15A. The composite substrate 140 includes a low-temperature co-fired ceramic (LTCC) 10 and a resin substrate 20. The low-temperature co-fired ceramic and resin substrate of the composite substrate according to the fifth embodiment may be the same as the low-temperature co-fired ceramic and resin substrate of the composite substrate according to the first embodiment, except for the features described below. The low-temperature co-fired ceramic 10 is a substantially rectangular parallelepiped having a first main surface 10a, a second main surface 10b opposite the first main surface 10a, and a side surface 10c connecting the first main surface 10a and the second main surface 10b. The first main surface 10a is directly bonded to the resin substrate 20.

[0091] A chamfered portion 10d is provided at a corner from the first main surface 10a to the side surface 10c of the low-temperature co-fired ceramic 10. As shown in Fig. 15B , when an extension line Ea of the first main surface 10a and an extension line Ec of the side surface 10c are drawn and the intersection point of the extension lines Ea and Ec is designated as Ep, the chamfered portion 10d refers to a portion of the surface of the low-temperature co-fired ceramic 10 located inside (on the low-temperature co-fired ceramic side) of the extension lines Ea and Ec.

[0092] The shape of the chamfered portion 10d may be either an R-chamfer or a C-chamfer, and the shape is not limited. Fig. 15B shows an example in which the shape of the chamfered portion 10d is an R-chamfer. When the chamfered portion 10d is an R-chamfer, the corners are rounded with a radius R1, as in the composite substrate according to the first embodiment, and the corners of the adjacent side surfaces are rounded with a radius R2, and the radius R2 may be larger than the radius R1.

[0093] That is, the composite substrate of this embodiment includes a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in the thickness direction, and the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, the first main surface is directly bonded to the resin substrate, corners from the first main surface to the side surface form chamfered portions, the corners from the first main surface to the side surface are rounded with a radius R1, the corners of the adjacent side surfaces are rounded with a radius R2, the radius R2 is greater than the radius R1, and a raised portion is formed in which the resin of the resin substrate is raised from the first main surface to the side surface including the chamfered portion.

[0094] In addition, in this embodiment, it is not essential to satisfy the relationship between radius R2 and radius R1 defined in the composite substrate according to the first embodiment, and therefore radius R2 and radius R1 may be the same or may be smaller than radius R1. Furthermore, the corners of the side surfaces adjacent to the chamfered portion do not have to be rounded.

[0095] 15B, in the composite substrate of this embodiment, the resin of the resin substrate 20 rises from the first main surface 10a to the side surface 10c including the chamfered portion 10d, forming a raised portion 20a. The raised portion "to the side surface" means that the upper end 20a1 of the raised portion 20a is located above the upper end 10d1 of the chamfered portion 10d, and the upper end 20a1 of the raised portion 20a is in contact with the side surface 10c.

[0096] There is no limitation on how far the raised portion 20a rises on the side surface 10c, but it is preferable that the upper end 20a1 of the raised portion 20a be located below half the thickness of the low-temperature co-fired ceramic 10 on the side surface 10c of the low-temperature co-fired ceramic 10.

[0097] In the composite substrate of this embodiment, a chamfered portion is provided from the first main surface of the LTCC to the side surface, which reduces stress concentration at the edge when subjected to temperature cycling, making it less likely for delamination to occur at the bonding interface between the LTCC and the resin substrate. Furthermore, a raised portion of resin is provided from the first main surface to the side surface including the chamfered portion, which protects the corners of the LTCC, which are the starting points for delamination, with the resin, making it less likely for delamination to occur at the bonding interface between the LTCC and the resin substrate.

[0098] Next, a composite substrate according to a sixth embodiment of the present invention will be described with reference to Fig. 16A and Fig. 16B. Fig. 16A is a cross-sectional view schematically showing an example of the composite substrate according to the sixth embodiment of the present invention and an antenna module using the composite substrate. Fig. 16B is a partially enlarged view of the dotted line portion C of the composite substrate in Fig. 16A.

[0099] The antenna module 240 shown in Fig. 16A includes a composite substrate 140. The configurations of the antenna module 240 and the composite substrate 140 are basically the same as the configurations of the antenna module 200 and the composite substrate 100 shown in Fig. 10. The fact that the low-temperature co-fired ceramic has a constraining layer and that the low-temperature co-fired ceramic has recesses and protrusions on its side surfaces and chamfered portions will be described.

[0100] FIG. 16A shows the layer structure of the composite substrate 140 in detail. The low-temperature co-fired ceramic 10 included in the composite substrate 140 has a structure in which low-temperature co-fired ceramic layers 11 and constraining layers 16 are alternately stacked. The low-temperature co-fired ceramic layers 11 can be the same as the low-temperature co-fired ceramic layers 11 described above with reference to FIG. 10. The constraining layers 16 are formed by forming a slurry into a sheet using a doctor blade method, in which a ceramic powder, a material that does not sinter during the LTCC firing process, is mixed with a resin, a dispersant, a plasticizer, and a solvent. Alumina powder is preferred as the ceramic powder used for the constraining layers. The thickness of the sheet is preferably 1 μm or more and 5 μm or less, with 2 μm being particularly preferred. The provision of the constraining layers can control the amount of shrinkage of the LTCC green sheet during the firing process, thereby improving the dimensional accuracy of the low-temperature co-fired ceramic.

[0101] The side surface 10c of the low-temperature co-fired ceramic 10 has a recess 10c1 and a protrusion 10c2. The recess 10c1 is a curved recessed portion of the side surface of the low-temperature co-fired ceramic layer 11. The protrusion 10c2 is a portion where the side surface (end) of the constraining layer 16 protrudes beyond the side surface of the low-temperature co-fired ceramic layer 11.

[0102] Figure 16B shows the chamfered portion 10d. As in Figure 15B, Figure 16B also shows an extension line Ea of the first main surface 10a, an extension line Ec of the side surface 10c, and an intersection point Ep of the extension line Ea and the extension line Ec. At the corner of the low-temperature co-fired ceramic 10, the surface of the low-temperature co-fired ceramic 10 is located inside the extension line Ec and the extension line Ea, and it can be said that the surface of the low-temperature co-fired ceramic 10 forms a chamfered portion. The chamfered portion 10d of the low-temperature co-fired ceramic 10 also has a recess 10d2 and a protrusion 10d3. The recess 10d2 is a portion where the side surface of the low-temperature co-fired ceramic layer 11 is recessed in a curved shape. The protrusion 10d3 is a portion where the side surface (end) of the constraining layer 16 protrudes beyond the side surface of the low-temperature co-fired ceramic layer 11.

[0103] In the composite substrate of this embodiment, the side surfaces and chamfered portions of the low-temperature co-fired ceramic have a shape with concave and convex portions, which increases the bonding strength between the side surfaces and chamfered portions of the low-temperature co-fired ceramic and the raised portions of the resin, making it less likely that delamination will occur at the bonding interface between the low-temperature co-fired ceramic and the resin substrate.

[0104] The composite substrates of the fifth and sixth embodiments may be antenna modules including a patch antenna, for example. Similarly to the composite substrate of the second embodiment shown in FIG. 3, the resin substrate of the composite substrate may have a composite portion that overlaps with the low-temperature co-fired ceramic and an extension portion that does not overlap with the low-temperature co-fired ceramic.

[0105] An example of a method for manufacturing the low-temperature co-fired ceramic used in the composite substrate of the sixth embodiment of the present invention will be described below. Figures 17A, 17B, and 17C are process diagrams schematically showing an example of a manufacturing process of the low-temperature co-fired ceramic used in the composite substrate of the sixth embodiment.

[0106] 17A , LTCC green sheets 311 and constraining layer green sheets 316 are alternately stacked and pressed together using a mold to produce laminate 310. LTCC green sheets 311 are formed by sheeting a slurry containing low-temperature co-fired ceramic material, binder, and plasticizer in desired amounts using a doctor blade method. Constraining layer green sheets 316 are formed by sheeting a slurry containing ceramic powder, a material that does not sinter during the LTCC firing process, to which resin, dispersant, plasticizer, and solvent have been added and mixed using a doctor blade method.

[0107] The laminate is cut into individual pieces before firing, and then fired to obtain low-temperature fired ceramic 10. 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 a temperature of 800°C or higher and 1000°C or lower is preferable. FIG. 17B shows the low-temperature fired ceramic 10 obtained by firing. In the obtained low-temperature fired ceramic 10, the portion that was the LTCC green sheet 311 becomes the low-temperature fired ceramic layer 11, and the portion that was the constraining layer green sheet 316 becomes the constraining layer 16.

[0108] The LTCC green sheet 311 shrinks upon firing, but shrinkage is suppressed on the upper and lower surfaces in contact with the constraining layer green sheet 316, while shrinkage occurs in the center of the thickness direction away from the constraining layer green sheet 316. As a result, the side surface 10c of the low-temperature co-fired ceramic layer 11 is curved and recessed, forming a recess 10c1. Because the constraining layer green sheet 316 does not shrink during firing, the side surface 10c of the low-temperature co-fired ceramic layer 11 forms a protrusion 10c2 that protrudes beyond the recess 10c1. By forming the low-temperature co-fired ceramic into individual pieces before firing, the individual pieces of the low-temperature co-fired ceramic have recesses and protrusions on their side surfaces. On the other hand, unlike the process described above, when the low-temperature co-fired ceramic is fired as a sheet and then singulated, the side surfaces of the low-temperature co-fired ceramic do not have recesses or protrusions, and are flat.

[0109] By performing barrel processing or the like on the low-temperature co-fired ceramic, a chamfered portion is formed in which the corners are chamfered from the first main surface to the side surface of the low-temperature co-fired ceramic after sintering. Fig. 17C shows the chamfered portion 10d. It is preferable to adjust the strength of the processing so that a recess 10d2 and a protrusion 10d31 remain in the chamfered portion 10d even after the chamfered portion 10d is formed.

[0110] An example of a method for manufacturing the composite substrates according to the fifth and sixth embodiments of the present invention will be described below. Figures 18A, 18B, and 18C are process diagrams schematically showing an example of a manufacturing process for the composite substrates according to the fifth and sixth embodiments. As shown in Figure 18A, the low-temperature co-fired ceramic 10 is arranged so that the first main surface 10a of the low-temperature co-fired ceramic 10 is in contact with the surface of the resin substrate sheet 40.

[0111] Thereafter, as shown in FIG. 18B , the low-temperature co-fired ceramic and the resin substrate sheet are heated while being pressed under pressure, thereby integrating the low-temperature co-fired ceramic and the resin substrate sheet. This integration process forms a raised portion 20a. For example, this bonding process may be performed at a temperature of 230°C or higher and 350°C or lower, and at a pressure of 3 MPa or higher and 20 MPa or lower. By using a thermoplastic resin as the resin substrate sheet and setting the heating temperature and / or pressure of the pressure press high during integration, the height of the raised portion can be increased. By increasing the heating temperature and pressure of the pressure press, a raised portion is formed in which the resin of the resin substrate bulges from the first main surface to the side surface, including the chamfered portion. The pressure press conditions are preferably higher in temperature and pressure than those of the bonding process in the composite substrate manufacturing methods of the first to fourth embodiments of the present invention.

[0112] 18C , after bonding the low-temperature co-fired ceramic 10 and the resin substrate sheet 40, the resin substrate sheet 40 is cut along a cutting line with a laser from the back side of the surface bonded to the first main surface 10 a of the low-temperature co-fired ceramic 10. In this way, a composite substrate 140 is obtained.

[0113] The present specification discloses the following:

[0114] <1> A composite substrate comprising: a resin substrate; and a low-temperature co-fired ceramic bonded to the resin substrate in a thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite to the first main surface, and a side surface connecting the first main surface and the second main surface, wherein the first main surface is directly bonded to the resin substrate, wherein corners from the first main surface to the side surface are rounded with a radius R1, and wherein corners of adjacent side surfaces are rounded with a radius R2, and wherein the radius R2 is greater than the radius R1.

[0115] <2> The composite substrate according to <1>, wherein the resin forming the resin substrate is a thermoplastic resin.

[0116] <3> The composite substrate according to <2>, wherein the resin of the resin substrate bulges in the thickness direction at a joint end with the low-temperature co-fired ceramic, and the bulging portion where the resin bulges extends halfway from the first main surface to the side surface.

[0117] <4> The composite substrate according to any one of <1> to <3>, wherein the resin constituting the resin substrate has a thermal expansion coefficient in the thickness direction of 200 ppm / °C or more.

[0118] <5> The composite substrate according to any one of <1> to <4>, wherein the resin substrate has a composite portion overlapping the low-temperature co-fired ceramic and an extension portion not overlapping the low-temperature co-fired ceramic.

[0119] <6> The composite substrate according to any one of <1> to <5>, wherein the radius R1 is 0.020 mm or more and 0.400 mm or less, and the radius R2 is 0.500 mm or more and 1.20 mm or less.

[0120] <7> A composite substrate comprising: a resin substrate; and a low-temperature co-fired ceramic bonded to the resin substrate in a thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, wherein the first main surface is directly bonded to the resin substrate, and a chamfered portion is formed by chamfering corners from the first main surface to the side surface, and wherein resin of the resin substrate is raised from the first main surface to the side surface including the chamfered portion.

[0121] <8> The composite substrate according to <7>, wherein the side surface and the chamfered portion of the low-temperature co-fired ceramic have a shape having a concave portion and a convex portion, and the concave portion is recessed in a curved shape.

[0122] <9> The composite substrate according to <8>, wherein the low-temperature co-fired ceramic has a configuration in which a low-temperature co-fired ceramic layer and a constraining layer are laminated, the low-temperature co-fired ceramic layer forming the recessed portions and the constraining layer forming the protruding portions.

[0123] EXAMPLES Hereinafter, examples will be given that more specifically disclose the composite substrate of the present invention, but the present invention is not limited to these examples.

[0124] Example 1 <Preparation of LTCC> First, a slurry is prepared by mixing ceramic powder, binder, and plasticizer in desired amounts. The ceramic powder may be any of the ceramic powders described above as materials for forming low-temperature co-fired ceramics. Conventional binders and plasticizers may be used. Next, the slurry is applied to a carrier film and formed into a sheet to produce an LTCC green sheet. A lip coater or doctor blade may be used to apply the slurry. In this case, it is preferable that the thickness of the LTCC green sheet be 5 μm or more and 100 μm or less. Via holes were formed and filled, and an electrode pattern was printed on the obtained LTCC green sheet using the method described above.

[0125] The processed green sheets were stacked in the number required for the design, placed in a mold, and pressed using a press. The resulting pressed body was cut into individual pieces using a laser to have the shape shown in Figures 1A and 1B and the dimensions shown in Table 1. The individual green sheets were then barrel-cut to form a curve with a radius R1 (0.120 mm) from the first main surface of the LTCC toward the side. The barrel-cut individual pieces were fired at 900°C or higher and 1000°C or lower to obtain LTCC of the desired shape. The thermal expansion coefficient of the LTCC was 8.0 ppm / °C in both the planar direction (LW direction) and the thickness direction (T direction).

[0126] <Preparation of Resin Substrate> Next, the preparation of the resin substrate will be described. A resin sheet was prepared by laminating a liquid crystal polymer (LCP), which is a thermoplastic resin, onto a metal foil. Next, the metal foil was patterned by etching to form an electrode pattern on the resin sheet. Subsequently, via holes were formed in the resin sheet by a known method, and the via holes were filled with a conductive paste. After that, multiple resin sheets filled with the conductive paste were stacked to prepare a resin substrate sheet with a thickness of 0.3 mm. The thermal expansion coefficient of the liquid crystal polymer was 30 ppm / °C in both the planar direction (LW direction) and the thickness direction (T direction).

[0127] <Lamination of LTCC and Resin Substrate Sheet> The LTCC prepared above was arranged on a resin substrate sheet as shown in FIG. 8, and the LTCC and the resin substrate sheet were bonded together by hot pressing.

[0128] <Formation of Composite Substrate> After the bonded LTCC and resin substrate sheet were cooled, the resin substrate was cut from the back side of the resin substrate sheet with a laser to obtain a composite substrate having the shape shown in FIGS. 1A and 1B and the dimensions shown in Table 1.

[0129] Example 2 A composite substrate having an extension was obtained in the same manner as in Example 1, except that the size of R1 of the LTCC was changed and, when the resin sheet laminated with the LTCC was cut with a laser, an extension was provided in the shape shown in FIG. 3 and with the dimensions shown in Table 1.

[0130] Example 3 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1 and a liquid crystal polymer (LCP) having a thermal expansion coefficient of 40 ppm / °C in both the planar direction (LW direction) and the thickness direction (T direction) was used as the resin.

[0131] Example 4 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1, a liquid crystal polymer (LCP) with a thermal expansion coefficient of 16 ppm / °C in the planar direction (LW direction) and 250 ppm / °C in the thickness direction (T direction) was used as the resin, and hot pressing was performed at different temperatures and pressures. A raised portion of the resin was formed at the joint edge by pressing.

[0132] Example 5 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1 and a liquid crystal polymer (LCP) having a thermal expansion coefficient of 30 ppm / °C in the planar direction (LW direction) and 40 ppm / °C in the thickness direction (T direction) was used as the resin.

[0133] Example 6 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrates were changed to the values ​​shown in Table 1 and a liquid crystal polymer (LCP) having a thermal expansion coefficient of 15 ppm / °C in the planar direction (LW direction) and 270 ppm / °C in the thickness direction (T direction) was used as the resin. A raised portion of the resin was formed at the joint edge by pressing.

[0134] Example 7 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1, and a liquid crystal polymer (LCP) having a thermal expansion coefficient of 25 ppm / °C in the planar direction (LW direction) and 35 ppm / °C in the thickness direction (T direction) was used as the resin.

[0135] Example 8 A composite substrate having an extension was obtained in the same manner as in Example 3, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1, and when the resin substrate sheet laminated with the LTCC was cut with a laser, an extension was provided in the shape shown in FIG. 3 and with the dimensions shown in Table 1.

[0136] Example 9 LTCC was obtained in the same manner as in Example 1, except for changing the dimensions to the values ​​shown in Table 1. Next, a 0.90 mm-thick thermosetting resin substrate sheet was prepared using polyimide resin as the resin. To fabricate the resin substrate sheet, a mixture of polyimide resin and inorganic filler was first molded into a sheet on a carrier film to obtain a semi-cured polyimide sheet. The polyimide sheet was then heat-treated to adjust the viscosity to a level that prevented it from flowing off the carrier film. Via holes were formed in the polyimide sheet using a laser or other method, and a desmearing process was performed. The formed vias were then filled with a conductive paste. Subsequently, a conductive layer was formed on the surface of the polyimide sheet by sequential electroless copper plating and electrolytic copper plating, and this conductive layer was patterned to form an electrode pattern. The carrier film was then peeled off, and a predetermined number of polyimide sheets were stacked to form a resin substrate sheet. Next, LTCC was arranged on the resin substrate sheet as shown in Figure 8, and the resin substrate sheet was fully cured using a hot and press to form a composite substrate of LTCC and polyimide resin. After laminating the LTCC and the resin substrate sheet, the resin substrate sheet was cut from the back side with a laser to obtain a composite substrate having the shape shown in FIGS. 4A and 4B and the dimensions shown in Table 1.

[0137] Example 10 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 1 and a liquid crystal polymer (LCP) having a thermal expansion coefficient of 15 ppm / °C in the planar direction (LW direction) and 30 ppm / °C in the thickness direction (T direction) was used as the resin.

[0138] Example 11 A composite substrate was obtained in the same manner as in Example 7, except that the dimensions of the LTCC and resin substrates were changed to the values ​​shown in Table 1.

[0139] Comparative Example 1 A composite substrate was obtained in the same manner as in Example 1, except that the dimensions of the LTCC and resin substrates were changed to the values ​​shown in Table 2.

[0140] Comparative Example 2 A composite substrate was obtained in the same manner as in Example 5, except that the dimensions of the LTCC and resin substrates were changed to the values ​​shown in Table 2.

[0141] Comparative Example 3 A composite substrate with an extended portion was obtained in the same manner as in Example 3, except that the dimensions of the LTCC and resin substrate were changed to the values ​​shown in Table 2, and when the resin substrate sheet laminated with the LTCC was cut with a laser, an extended portion was provided in the shape shown in Fig. 3 and with the dimensions shown in Table 2. No roundness (R1) in the thickness direction was formed in the LTCC.

[0142] Comparative Example 4 A composite substrate was obtained in the same manner as in Example 9, except that the LTCC was not rounded.

[0143]

[0144]

[0145] The composite substrates obtained above were evaluated by visual inspection and cross-sectional polishing to check for delamination between the LTCC and the resin substrate and cracks in the resin substrate. For each example and comparative example, 100 composite substrates were evaluated. In the composite substrates of Examples 1 to 11, in which the LTCC was rounded in the planar and thickness directions and the radius R2 was greater than the radius R1, delamination between the LTCC and the resin substrate and cracks in the resin substrate were less frequent than in the composite substrates of Comparative Examples 1 to 4. Among Examples 1 to 11, the composite substrates of Examples 1 to 9, in which the radius R1 was 0.020 mm or more and 0.400 mm or less and the radius R2 was 0.500 mm or more and 1.20 mm or less, showed even less delamination between the LTCC and the resin substrate and cracks in the resin substrate than in the composite substrates of Examples 10 and 11.

[0146] 10 Low-temperature co-fired ceramic (LTCC) 10a First main surface 10b Second main surface 10c Side surface 10c1 Concave portion of side surface 10c2 Convex portion of side surface 10d Chamfered portion 10d1 Upper end of chamfered portion 10d2 Concave portion of chamfered portion 10d3 Convex portion of chamfered portion 11 Low-temperature co-fired ceramic layer 13 Electrode pattern 14 Via 15 Antenna 16 Constraint layer 20 Resin substrate 20a Protruding portion 20a1 Upper end of protruding portion 21 Resin layer 23 Electrode pattern 24 Via 25 Composite portion 26 Extension portion 30 LTCC green sheet laminate 31 Pre-fired piece 40 Resin substrate sheet 50 Solder 60 Motherboard 70 Connector 100, 110, 120, 130, 140 Composite substrate 200, 210, 220, 230, 240 Antenna module 310 Laminate 311 LTCC green sheet 316 Constraining layer green sheet CL1, CL2, CL3, CL4 Cutting lines

Claims

1. A composite substrate comprising a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in a thickness direction, the low-temperature co-fired ceramic being an approximately rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, the first main surface being directly bonded to the resin substrate, corners from the first main surface to the side surface being rounded with a radius R1, corners of adjacent side surfaces being rounded with a radius R2, and the radius R2 being greater than the radius R1.

2. The composite substrate according to claim 1, wherein the resin forming the resin substrate is a thermoplastic resin.

3. The composite substrate according to claim 2, wherein the resin of the resin substrate bulges in the thickness direction at the joint end with the low-temperature co-fired ceramic, and the bulging portion where the resin bulges extends halfway from the first main surface to the side surface.

4. The composite substrate according to any one of claims 1 to 3, wherein the thermal expansion coefficient of the resin constituting the resin substrate in the thickness direction is 200 ppm / °C or more.

5. A composite substrate according to any one of claims 1 to 4, wherein the resin substrate has a composite portion overlapping the low-temperature co-fired ceramic and an extension portion not overlapping the low-temperature co-fired ceramic.

6. A composite substrate according to any one of claims 1 to 5, wherein R1 is 0.020 mm or more and 0.400 mm or less, and R2 is 0.500 mm or more and 1.20 mm or less.

7. A composite substrate comprising a resin substrate and a low-temperature co-fired ceramic bonded to the resin substrate in a thickness direction, wherein the low-temperature co-fired ceramic is a substantially rectangular parallelepiped having a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, the first main surface being directly bonded to the resin substrate, a chamfered portion having a corner chamfered from the first main surface to the side surface, and a raised portion formed by the resin of the resin substrate extending from the first main surface to the side surface including the chamfered portion.

8. The composite substrate according to claim 7, wherein the side surface and the chamfered portion of the low-temperature co-fired ceramic have a shape having a concave portion and a convex portion, and the concave portion is recessed in a curved shape.

9. The composite substrate according to claim 8, wherein the low-temperature co-fired ceramic is configured by laminating a low-temperature co-fired ceramic layer and a constraining layer, the low-temperature co-fired ceramic layer forming the recessed portion and the constraining layer forming the protruding portion.

Images