Multilayer substrate

Abstract

The present invention provides a multilayer substrate that can suppress the formation of voids in the thermosetting adhesive during the curing process. [Solution] The multilayer substrate 10 comprises a pair of substrates 1 and 2 having opposing surfaces 11a and 21a, and a thermosetting adhesive layer 3 provided between the pair of substrates 1 and 2 to bond the substrates 1 and 2. A conductive layer 12 is formed on the surface to be formed, which is at least one of the opposing surfaces 11a and 21a of the pair of substrates 1 and 2. Inclined regions 14a and 14b are formed on the side surfaces 12c and 12d of the conductive layer 12, inclined with respect to a surface perpendicular to the surface to be formed. The thermosetting adhesive layer 3 is formed of a thermosetting adhesive that does not become liquid at the curing temperature.

Description

Technical Field

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

Background Art

[0002] A multilayer substrate has, for example, a structure in which a plurality of substrates are bonded via a thermosetting adhesive layer. A conductor layer is formed on the surface of the substrate. The multilayer substrate can be manufactured by sandwiching a thermosetting adhesive sheet between the substrates and curing the thermosetting adhesive by heating and pressurization (see, for example, Patent Document 1).

[0003] In the basic curing process of the thermosetting adhesive, when the thermosetting adhesive is heated, it once melts and becomes highly fluid, and then curing proceeds. In the curing process, when the thermosetting adhesive is in a highly fluid state, the temperature, pressure, pressure application time, etc. are adjusted so that the thermosetting adhesive fills the unevenness on the surface of the substrate by the conductor layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If the thermosetting adhesive does not sufficiently fill the unevenness on the surface of the substrate in the curing process and voids remain, delamination, swelling, etc. may occur in the subsequent reflow process.

[0006] One aspect of the present invention aims to provide a multilayer substrate capable of suppressing the formation of voids in the thermosetting adhesive in the curing process.

Means for Solving the Problems

[0007] A multilayer substrate according to a first aspect of the present invention comprises a pair of substrates having opposing surfaces, and a thermosetting adhesive layer provided between the pair of substrates for bonding the substrates, wherein a conductive layer is formed on at least one of the opposing surfaces of the pair of substrates, on the surface to be formed, and an inclined region is formed on at least one side surface of the conductive layer, inclined with respect to a surface perpendicular to the surface to be formed, and the thermosetting adhesive layer is formed of a thermosetting adhesive that does not become liquid at the curing temperature.

[0008] According to the first aspect of the present invention, since an inclined region is formed on the side surface of the conductor layer, the concave portion formed by the side surface of the conductor layer and the surface to be formed becomes shallower compared to the case where the side surface of the conductor layer is not inclined. Therefore, the thermosetting adhesive tends to take on a shape that conforms to the side surface of the conductor layer. Consequently, the formation of voids in the thermosetting adhesive layer can be suppressed. Therefore, delamination, blistering, etc., are less likely to occur in subsequent processes.

[0009] When a thermosetting adhesive is less prone to liquefaction, it becomes less prone to deformation. However, according to the first aspect of the present invention, the thermosetting adhesive tends to conform to the shape of the conductive layer, so even when using a thermosetting adhesive that is less prone to deformation, the formation of voids can be suppressed.

[0010] A second aspect of the present invention is a multilayer substrate according to the first aspect, wherein the thermosetting adhesive constituting the thermosetting adhesive layer has a viscosity at the curing temperature that is not 1.0E+6 Pa·s or less.

[0011] A third aspect of the present invention is a multilayer substrate according to the first or second aspect, wherein at least one of the substrates has a rigid substrate.

[0012] A fourth aspect of the present invention is a multilayer substrate according to any one of the first to third aspects, wherein one of the pair of substrates has a flexible substrate and the other of the pair of substrates has a rigid substrate.

[0013] A fifth aspect of the present invention is a multilayer substrate according to any one of the first to fourth aspects, wherein in a cross section of the conductive layer intersecting the side surface in which the inclined region is formed, the ratio W2 / W1 of the width of the base W1 to the width W2 of the opposite side opposite the base is 9 / 10 or less.

[0014] A sixth aspect of the present invention is a multilayer substrate according to any one of the first to fifth aspects, wherein the thickness of the conductor layer is 10 μm or more and 30 μm or less.

[0015] A seventh aspect of the present invention is a multilayer substrate according to any one of the first to sixth aspects, wherein the thickness of the thermosetting adhesive layer is 15 μm or more and 50 μm or less.

[0016] An eighth aspect of the present invention is a multilayer substrate according to any one of the first to seventh aspects, wherein the relative permittivity of the substrate and the thermosetting adhesive layer is 3.5 or less.

[0017] A ninth aspect of the present invention is a multilayer substrate according to any one of the first to eighth aspects, wherein the conductive layer forms an array antenna. [Effects of the Invention]

[0018] According to one aspect of the present invention, a multilayer substrate is provided that can suppress the formation of voids in the thermosetting adhesive during the curing process. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic cross-sectional view of a multilayer substrate according to the first embodiment. [Figure 2] This is a schematic cross-sectional view of a part of a multilayer substrate according to the first embodiment. [Figure 3] This is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to the first embodiment. [Figure 4] This is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to the first embodiment. [Figure 5] This is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to the first embodiment. [Figure 6] It is a schematic cross-sectional view of a multilayer substrate according to the fifth embodiment. [Figure 7] It is a schematic cross-sectional view of a multilayer substrate according to the sixth embodiment. [Figure 8] It is a schematic cross-sectional view of a multilayer substrate according to the seventh embodiment. [Figure 9] It is a schematic cross-sectional view of a multilayer substrate according to the ninth embodiment. [Figure 10] It is a schematic plan view of the first substrate of the multilayer substrate according to the ninth embodiment. [Figure 11] It is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to a comparative form. [Figure 12] It is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to a comparative form. [Figure 13] It is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to a comparative form. [Figure 14] It is a cross-sectional view showing an example of a method for manufacturing a multilayer substrate according to a comparative form.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a multilayer substrate according to an embodiment of the present invention will be described based on the drawings.

[0021] FIG. 1 is a schematic cross-sectional view of a multilayer substrate according to the first embodiment. FIG. 2 is a schematic cross-sectional view of a part of the multilayer substrate. FIGS. 1 and 2 show cross-sections intersecting the side surface of the conductor layer.

[0022] In the following explanation, the positional relationships of each component will be described with reference to the XYZ Cartesian coordinate system. In Figure 1, the vertical direction is the Z direction. The Z direction is the thickness direction of the multilayer substrate 10. The upper side in Figure 1 is the +Z side. The lower side in Figure 1 is the -Z side. Viewing from the Z direction is called a plan view. In Figure 1, the horizontal direction is the X direction. The X direction is perpendicular to the Z direction. The right side in Figure 1 is the +X side. The left side in Figure 1 is the -X side. The Y direction is perpendicular to the X and Z directions. The X and Y directions are parallel to the opposing surface 11a of the first substrate 1. Note that the positional relationships defined here do not limit the orientation of the multilayer substrate 10 when it is in use.

[0023] [Multilayer substrate] (First embodiment) As shown in Figure 1, the multilayer substrate 10 comprises a first substrate 1 (substrate), a second substrate 2 (substrate), and a thermosetting adhesive layer 3. The first substrate 1 and the second substrate 2 are examples of a "pair of substrates". The first substrate 1 comprises a first base material 11 and one or more conductive layers 12.

[0024] The first substrate 11 is formed in a plate shape. The material of the first substrate 11 is not particularly limited. The first substrate 11 may be, for example, a rigid substrate or a flexible substrate. The first substrate 11 is an insulating substrate. It is desirable that the first substrate 11 be formed of a low dielectric material. The relative permittivity of the first substrate 11 is preferably 3.5 or less at 60 GHz. When the relative permittivity of the first substrate 11 is within this range, the electromagnetic properties of the multilayer substrate 10 can be improved.

[0025] The +Z side of the first substrate 11 is the opposing surface 11a. The opposing surface 11a is the surface on which the conductive layer 12 is formed. The -Z side of the first substrate 11 is the outer surface 11b. The outer surface 11b is the surface opposite to the opposing surface 11a.

[0026] The conductive layer 12 is formed of a conductive material. The conductive material includes, for example, metals such as copper, silver, and gold. The conductive layer 12 may be a metal foil, a plating layer, or the like. The conductive layer 12 may also be formed of a conductive paste (conductive material).

[0027] As shown in Figure 2, the conductor layer 12 has a bottom surface 12a, a top surface 12b, a first side surface 12c, and a second side surface 12d. The bottom surface 12a is the -Z side surface of the conductor layer 12. The bottom surface 12a is in contact with the opposing surface 11a. The top surface 12b is the +Z side surface. The top surface 12b is the surface opposite to the bottom surface 12a. The top surface 12b is parallel to the bottom surface 12a.

[0028] The first side surface 12c is the -X side (one side) of the conductor layer 12. The second side surface 12d is the +X side (the other side) of the conductor layer 12. The first side surface 12c and the second side surface 12d can be collectively referred to as "side surfaces 12c, 12d". Side surfaces 12c, 12d may extend in the Y direction.

[0029] A first inclined region 14a is formed on the first side surface 12c. In this embodiment, the first inclined region 14a is formed over the entire first side surface 12c. That is, the first inclined region 14a is a region formed from the upper end to the lower end of the first side surface 12c.

[0030] The first inclined region 14a is inclined with respect to a plane V1 perpendicular to the opposing plane 11a. The first inclined region 14a is inclined outward, approaching the opposing plane 11a. That is, the first inclined region 14a is inclined downward toward the -X side. "Outward" is the direction in which the first side surface 12c and the second side surface 12d move away from each other. Plane V1 is a plane defined, for example, by the Y direction and the Z direction.

[0031] The inclination angle α1 of the first inclined region 14a with respect to surface V1 is greater than 0° and less than 90°. The inclination angle α1 can be, for example, 20° or more (for example, 30° or more). By setting the inclination angle α1 within this range, it is possible to suppress the formation of voids in the thermosetting adhesive during the curing process of the thermosetting adhesive.

[0032] The inclination angle α1 can be 70° or less (for example, 60° or less). By setting the inclination angle α1 within this range, a large cross-sectional area of ​​the conductor layer 12 can be secured, thereby improving the conductivity of the conductor layer 12.

[0033] A second inclined region 14b is formed on the second side surface 12d. In this embodiment, the second inclined region 14b is formed over the entire second side surface 12d. That is, the second inclined region 14b is a region formed from the upper end to the lower end of the second side surface 12d.

[0034] The second inclined region 14b is inclined with respect to a plane V2 perpendicular to the opposing plane 11a. The second inclined region 14b is inclined outward, approaching the opposing plane 11a. That is, the second inclined region 14b is inclined downward toward the +X side. Plane V2 is, for example, a plane defined by the Y direction and the Z direction.

[0035] The inclination angle α2 of the second inclined region 14b with respect to surface V2 is greater than 0° and less than 90°. The inclination angle α2 can be, for example, 20° or more (for example, 30° or more). By setting the inclination angle α2 within this range, it is possible to suppress the formation of voids in the thermosetting adhesive during the curing process of the thermosetting adhesive.

[0036] The inclination angle α2 can be 70° or less (for example, 60° or less). By setting the inclination angle α2 within this range, the cross-sectional area of ​​the conductor layer 12 can be increased, thereby improving the conductivity of the conductor layer 12. The first inclined region 14a and the second inclined region 14b can be collectively referred to as "inclined regions 14a, 14b".

[0037] The cross-section of the conductor layer 12 is, for example, a trapezoidal shape having a base 13a (lower base), an opposite side 13b (upper base), a first side 13c (first leg), and a second side 13d (second leg). The opposite side 13b is the side opposite to the base 13a. The base 13a and the opposite side 13b are parallel. The base 13a is formed by the bottom surface 12a (surface to be formed). The opposite side 13b is formed by the top surface 12b. The first side 13c is formed by the first side surface 12c. The second side 13d is formed by the second side surface 12d. The bottom surface 12a is the surface that overlaps with the opposing surface 11a (surface to be formed).

[0038] The ratio W2 / W1 of the width W1 (dimension in the X direction) of the bottom side 13a of the conductor layer 12 to the width W2 (dimension in the X direction) of the opposite side 13b is preferably 9 / 10 or less. This increases the inclination angles α1 and α2 of the inclined regions 14a and 14b, thereby suppressing the formation of gaps between the side surfaces 12c and 12d and the thermosetting adhesive sheet 31.

[0039] The ratio W2 / W1 may be, for example, 1 / 10 or more. This allows for a larger cross-sectional area of ​​the conductor layer 12, thereby improving the conductivity of the conductor layer 12.

[0040] The inclination angle α2 may be equal to the inclination angle α1. When the inclination angles α1 and α2 are equal, the cross-section of the conductor layer 12 becomes an isosceles trapezoid.

[0041] The second substrate 2 comprises a second substrate 21. The second substrate 21 is formed in a plate shape. The material of the second substrate 21 is not particularly limited. The second substrate 21 may be, for example, a rigid substrate or a flexible substrate. The second substrate 21 is an insulating substrate. It is desirable that the second substrate 21 be formed of a low dielectric material. If the second substrate 21 is formed of a low dielectric material, the electromagnetic properties of the multilayer substrate 10 can be improved.

[0042] The -Z side of the second substrate 21 is the opposing surface 21a. The +Z side of the second substrate 21 is the outer surface 21b. The outer surface 21b is the surface opposite to the opposing surface 21a.

[0043] As shown in Figure 1, the first substrate 1 and the second substrate 2 are arranged such that their opposing surfaces 11a and 21a face each other. The second substrate 2 is located at a distance from the first substrate 1 to the +Z side (above). The opposing surface 21a is, for example, parallel to the opposing surface 11a.

[0044] The thermosetting adhesive layer 3 is formed of a thermosetting adhesive, such as an epoxy resin. The thermosetting adhesive layer 3 is provided between the first substrate 1 and the second substrate 2. The thermosetting adhesive layer 3 adheres the first substrate 1 and the second substrate 2. The thermosetting adhesive layer 3 is in contact with the opposing surfaces 11a, 21a and the conductive layer 12.

[0045] Thermosetting adhesives have a specific curing temperature. When heated to their curing temperature, thermosetting adhesives initially become highly fluid before curing. The curing temperature of thermosetting adhesives is, for example, 150°C to 200°C.

[0046] Thermosetting adhesives do not become liquid at the curing temperature. For example, the viscosity of a thermosetting adhesive at its highest fluidity at the curing temperature will not be less than, for example, 1.0E+6 Pa·s. In other words, the viscosity of a thermosetting adhesive at its highest fluidity at the curing temperature will exceed 1.0E+6 Pa·s.

[0047] It is desirable that the thermosetting adhesive layer 3 be made of a low dielectric material. When the thermosetting adhesive is made of a low dielectric material, the electromagnetic properties of the multilayer substrate 10 can be improved.

[0048] [Manufacturing method for multilayer substrates] Next, an example of a method for manufacturing the multilayer substrate 10 will be described with reference to Figures 3 to 5. Figures 3 to 5 are cross-sectional views showing an example of a method for manufacturing the multilayer substrate 10.

[0049] <Lamination process> As shown in Figure 3, a thermosetting adhesive sheet 31 is laminated onto the opposing surface 21a of the second substrate 2. The thermosetting adhesive sheet 31 is made of a thermosetting adhesive (for example, epoxy resin). The second substrate 2 with the laminated thermosetting adhesive sheet 31 and the first substrate 1 are placed so that their opposing surfaces 11a and 21a face each other.

[0050] A laminate 5 consisting of a first substrate 1, a second substrate 2, and a thermosetting adhesive sheet 31 is sandwiched between two pressing plates 41 and 42. The +Z side of pressing plate 41 is the pressing surface 41a. The -Z side of pressing plate 42 is the pressing surface 42a.

[0051] <Curing process> (Pressurization process) As shown in Figure 4, the pressing surfaces 41a and 42a of the pressing plates 41 and 42 apply a compressive force in the thickness direction to the laminate 5. The thermosetting adhesive sheet 31 deforms according to the shape of the conductor layer 12 when pressed against it. Since inclined regions 14a and 14b are formed on the sides 12c and 12d of the conductor layer 12, the thermosetting adhesive sheet 31 tends to conform to the shape of the sides 12c and 12d. Therefore, even if a gap 50 is formed between the sides 12c and 12d and the thermosetting adhesive sheet 31, the gap 50 does not tend to become large.

[0052] (Heating process) As shown in Figure 5, the laminate 5 is heated while being pressed by the pressing plates 41 and 42. The heating temperature is, for example, the cure temperature of the thermosetting adhesive that makes up the thermosetting adhesive sheet 31, or a temperature higher than the cure temperature. Upon heating, the thermosetting adhesive becomes highly fluid, then hardens, forming a thermosetting adhesive layer 3.

[0053] The thermosetting adhesive in the portion facing the sides 12c and 12d of the conductor layer 12 deforms in a highly fluid state. Because the void 50 (see Figure 4) is small, the highly fluid thermosetting adhesive deforms along the sides 12c and 12d. As a result, the void between the thermosetting adhesive layer 3 and the conductor layer 12 shrinks or disappears.

[0054] Through the above process, a multilayer substrate 10 is obtained having a first substrate 1, a second substrate 2, and a thermosetting adhesive layer 3.

[0055] <Post-process> Components can be mounted on the multilayer substrate 10. When mounting components on the multilayer substrate 10, a reflow process may be performed to heat the multilayer substrate 10. In the multilayer substrate 10, gaps are less likely to form between the thermosetting adhesive layer 3 and the conductive layer 12, so interlayer delamination and blistering caused by gaps are less likely to occur during the reflow process.

[0056] [Effects of the multilayer substrate according to the embodiment] In the multilayer substrate 10 according to this embodiment, inclined regions 14a and 14b are formed on the side surfaces 12c and 12d of the conductive layer 12, respectively. Therefore, compared to the case where the side surfaces of the conductive layer 12 are not inclined, the concave portion formed by the side surfaces 12c and 12d and the opposing surface 11a becomes shallower. Consequently, the thermosetting adhesive sheet 31 tends to conform to the shape of the side surfaces 12c and 12d. As a result, even if a void 50 is formed between the side surfaces 12c and 12d and the thermosetting adhesive sheet 31, the void 50 will shrink or disappear. Therefore, the formation of voids in the thermosetting adhesive layer 3 can be suppressed (see Figure 5). Consequently, delamination, blistering, etc., are less likely to occur in subsequent processes.

[0057] In the multilayer substrate 10, the thermosetting adhesive layer 3 is formed of a thermosetting adhesive that does not become liquid at the curing temperature. When the thermosetting adhesive is less likely to liquefy, the thermosetting adhesive sheet becomes less likely to deform. However, in the multilayer substrate 10 according to this embodiment, the thermosetting adhesive sheet 31 tends to conform to the shape of the conductive layer 12, so a gap is less likely to form between the thermosetting adhesive layer 3 and the conductive layer 12. Therefore, in the multilayer substrate 10, even though a thermosetting adhesive that is less likely to deform is used, the formation of gaps can be suppressed.

[0058] [Multilayer substrate] (Second embodiment) A multilayer substrate according to the second embodiment will be described using Figure 1. In the multilayer substrate according to this embodiment, the first substrate 11 of the first substrate 1 and the second substrate 21 of the second substrate 2 are rigid substrates. The rigid substrate is a hard substrate having high bending rigidity. The rigid substrate is formed from, for example, a fiber-reinforced resin. The fiber-reinforced resin is formed by impregnating reinforcing fibers with resin. Examples of reinforcing fibers include glass fibers, ceramic fibers, and aramid fibers. Examples of resins impregnated into the reinforcing fibers include epoxy resins, phenolic resins, and urea resins.

[0059] In the multilayer substrate according to this embodiment, similar to the multilayer substrate 10 according to the first embodiment (see Figure 1), the formation of voids in the thermosetting adhesive layer 3 can be suppressed. Therefore, delamination, blistering, and the like are less likely to occur in subsequent processes.

[0060] In the multilayer substrate according to this embodiment, the first substrate 11 and the second substrate 21 are rigid substrates. Since rigid substrates are resistant to deformation even under pressure and heating conditions, voids tend to remain in the concave portions formed by the side surfaces and opposing surfaces of the conductive layer. However, in the multilayer substrate according to this embodiment, because the conductive layer 12 has inclined regions 14a and 14b, the thermosetting adhesive sheet 31 tends to conform to the shape of the conductive layer 12, making it difficult for voids to form. Therefore, even though rigid substrates are used, the formation of voids can be suppressed.

[0061] [Multilayer substrate] (Third embodiment) A multilayer substrate according to the third embodiment will be described using Figure 1. The multilayer substrate according to this embodiment differs from the multilayer substrate according to the second embodiment in that the first substrate 11 of the first substrate 1 is a flexible substrate. That is, in this multilayer substrate, the first substrate 1 has a flexible substrate, and the second substrate 2 has a rigid substrate. The flexible substrate is a soft substrate with lower bending rigidity compared to the rigid substrate. The flexible substrate is formed from, for example, polyimide, polyester, liquid crystal polymer, etc.

[0062] In the multilayer substrate according to this embodiment, voids are less likely to form in the thermosetting adhesive layer 3, similar to the multilayer substrate 10 according to the first embodiment. Therefore, delamination and blistering are less likely to occur in subsequent processes. In the multilayer substrate according to this embodiment, void formation can be suppressed despite the use of a rigid substrate.

[0063] [Multilayer substrate] (Fourth embodiment) A multilayer substrate according to the fourth embodiment will be described using Figure 1. The multilayer substrate according to this embodiment differs from the multilayer substrate according to the second embodiment in that the second substrate 21 of the second substrate 2 is a flexible substrate. That is, in this multilayer substrate, the first substrate 1 has a rigid substrate, and the second substrate 2 has a flexible substrate.

[0064] In the multilayer substrate according to this embodiment, voids are less likely to form in the thermosetting adhesive layer 3, similar to the multilayer substrate 10 according to the first embodiment. Therefore, delamination and blistering are less likely to occur in subsequent processes. In the multilayer substrate according to this embodiment, void formation can be suppressed despite the use of a rigid substrate.

[0065] [Multilayer substrate] (Fifth embodiment) Figure 6 is a schematic cross-sectional view of a multilayer substrate according to the fifth embodiment. Components common to the multilayer substrate according to the other embodiments are denoted by the same reference numerals and their description is omitted.

[0066] As shown in Figure 6, in the multilayer substrate 410 according to this embodiment, the inclination angles α3 and α4 of the inclined regions 14a and 14b of the conductive layer 412 are relatively large. The inclination angles α3 and α4 can be, for example, 45° or more. By setting the inclination angles α3 and α4 within this range, the formation of voids in the thermosetting adhesive can be suppressed. The inclination angles α3 and α4 can be 80° or less. By setting the inclination angles α3 and α4 within this range, a large cross-sectional area of ​​the conductive layer 412 can be secured, and the conductivity of the conductive layer 412 can be improved.

[0067] [Multilayer substrate] (Sixth embodiment) Figure 7 is a schematic cross-sectional view of a multilayer substrate according to the sixth embodiment. Components common to the multilayer substrate according to the other embodiments are denoted by the same reference numerals and their description is omitted.

[0068] As shown in Figure 7, in the multilayer substrate 510 according to this embodiment, the thickness of the conductive layer 512 may be a thickness T1 which is half or less the thickness of the thermosetting adhesive layer 3, or a thickness T2 which is greater than half the thickness of the thermosetting adhesive layer 3. The thickness of the conductive layer 512 may be, for example, 10 μm or more and 30 μm or less.

[0069] If the thickness of the conductive layer 512 is 10 μm or more, the cross-sectional area of ​​the conductive layer 12 can be increased, thereby improving the conductivity of the conductive layer 12. If the thickness of the conductive layer 512 is 30 μm or less, the thermosetting adhesive sheet 31 tends to conform to the shape of the conductive layer 512, thus suppressing the formation of voids.

[0070] [Multilayer substrate] (7th embodiment) Figure 8 is a schematic cross-sectional view of a multilayer substrate according to the seventh embodiment. Components common to multilayer substrates according to other embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0071] As shown in Figure 8, the thickness of the thermosetting adhesive layer 3 is not particularly limited in the multilayer substrate 610 according to this embodiment. The thickness T3 of the thermosetting adhesive layer 3 may be, for example, 15 μm or more and 50 μm or less.

[0072] If the thickness T3 of the thermosetting adhesive layer 3 is 15 μm or more, the thermosetting adhesive material flows more easily during the curing process, which helps to suppress the formation of voids in the thermosetting adhesive layer 3. If the thickness T3 of the thermosetting adhesive layer 3 is 50 μm or less, the multilayer substrate 610 can be made thinner.

[0073] [Multilayer substrate] (8th embodiment) A multilayer substrate according to the eighth embodiment will be described using Figure 1. As shown in Figure 1, in the multilayer substrate according to this embodiment, the first substrate 11, the second substrate 21, and the thermosetting adhesive layer 3 are formed of a low dielectric material.

[0074] In the multilayer substrate according to this embodiment, the first substrate 11, the second substrate 21, and the thermosetting adhesive layer 3 are formed of low dielectric materials, which allows for good electromagnetic properties.

[0075] [Multilayer substrate] (9th embodiment) Figure 9 is a schematic cross-sectional view of a multilayer substrate according to the ninth embodiment. Figure 10 is a schematic plan view of the first substrate. Components common to multilayer substrates according to other embodiments are denoted by the same reference numerals and their description is omitted.

[0076] As shown in Figure 9, the multilayer substrate 810 comprises a first substrate 801, a second substrate 802, a third substrate 803, a fourth substrate 804, and a thermosetting adhesive layer 3 provided between adjacent substrates.

[0077] The first substrate 801 has a first base material 11 and a plurality of conductive layers 12. The second substrate 802 has a second base material 21.

[0078] The third substrate 803 has a third base material 831 and conductive layers 812 and 813. Conductive layer 812 is formed on the +Z side of the third base material 831. Conductive layer 813 is formed on the -Z side of the third base material 831.

[0079] The fourth substrate 804 has a fourth base material 841 and a conductive layer 814. The conductive layer 814 is formed on the -Z side surface of the fourth base material 841.

[0080] As shown in Figure 10, the multiple conductor layers 12 of the first substrate 801 are arranged in a rectangular grid (matrix) on the opposing surface 11a of the first substrate 11. The multiple conductor layers 12 form an array antenna. The conductor layer 12 has a first side surface 12c, a second side surface 12d, a third side surface 12e, and a fourth side surface 12f. The first side surface 12c is the -X side of the conductor layer 12. The second side surface 12d is the +X side of the conductor layer 12. The third side surface 12e is the +Y side of the conductor layer 12. The fourth side surface 12f is the -Y side of the conductor layer 12.

[0081] A first inclined region 14a is formed on the first side surface 12c. A second inclined region 14b is formed on the second side surface 12d. A third inclined region 14c is formed on the third side surface 12e. A fourth inclined region 14d is formed on the fourth side surface 12f.

[0082] [Multilayer board] (comparison form) Examples of comparative multilayer substrates and their manufacturing methods will be described with reference to Figures 11 to 14. Figures 11 to 14 are cross-sectional views showing examples of methods for manufacturing comparative multilayer substrates. Components common to the multilayer substrate according to the embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0083] <Lamination process> As shown in Figure 11, the first substrate 901 differs from the first substrate 1 (see Figure 1) in that the sides 912c and 912d of the conductive layer 912 are not inclined. A thermosetting adhesive sheet 31 is laminated onto the second substrate 2. The laminate 905 of the first substrate 901, the second substrate 2, and the thermosetting adhesive sheet 31 is sandwiched between two pressing plates 41 and 42.

[0084] <Curing process> (Pressurization process) As shown in Figure 12, the pressing plates 41 and 42 apply a compressive force in the thickness direction to the laminate 905. A gap 950 is formed between the side surfaces 912c and 912d and the thermosetting adhesive sheet 31.

[0085] (Heating process) As shown in Figure 13, the laminate 5 is pressed with pressing plates 41 and 42 while the laminate 905 is heated. The heating causes the thermosetting adhesive to harden, and a thermosetting adhesive layer 3 is formed. A gap 951 remains between the thermosetting adhesive layer 3 and the conductive layer 12. Through the above process, a multilayer substrate 910 is obtained having a first substrate 901, a second substrate 2, and a thermosetting adhesive layer 3.

[0086] <Post-process> As shown in Figure 14, when mounting components onto the multilayer substrate 910, a reflow process is performed to heat the multilayer substrate 910. In the multilayer substrate 910, during the reflow process, the voids 951 (see Figure 13) expand, causing delamination 952 to occur.

[0087] The technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0088] In the multilayer substrate 10 shown in Figure 1, gradient regions 14a and 14b are formed on the first side surface 12c and the second side surface 12d of the conductive layer 12, respectively. However, the gradient regions may be formed on only one of the side surfaces 12c and 12d. In other words, it is sufficient for the gradient regions to be formed on at least one side surface. In the multilayer substrate 810 shown in Figure 10, gradient regions 14a to 14d are formed on the side surfaces 12c to 12f of the conductive layer 12, but it is sufficient for the gradient regions to be formed on at least one of the side surfaces 12c to 12f.

[0089] In the multilayer substrate 10 shown in Figure 1, the inclination angles of the inclined regions 14a and 14b are constant throughout the entire region, but the inclination angles of the inclined regions do not have to be constant. For example, the inclined regions may be curved concave or curved convex.

[0090] In the multilayer substrate 10 shown in Figure 1, the conductive layer 12 is formed only on the opposing surface 11a of the first substrate 1 and the second substrate 2, but the configuration of the conductive layer is not particularly limited. For example, the conductive layer may be formed only on the opposing surface 21a, or it may be formed on both of the two opposing surfaces 11a and 21a. In other words, the conductive layer only needs to be formed on at least one of the opposing surfaces 11a and 21a.

[0091] In the multilayer substrate 10 shown in Figure 1, a sloped region is formed over the entire sides 12c and 12d of the conductor layer 12. However, the sloped region may be formed over only a portion of the side surface of the conductor layer. For example, the sloped region may be formed over a portion of the side surface of the conductor layer that includes the upper end but does not reach the lower end. Alternatively, the sloped region may be formed over a portion of the side surface of the conductor layer that includes the lower end but does not reach the upper end.

[0092] Furthermore, without departing from the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments and modifications may be combined as appropriate. [Explanation of symbols]

[0093] 1...First substrate (substrate), 2...Second substrate (substrate), 3...Thermosetting adhesive layer, 10,410,510,610,810...Multilayer substrate, 11a...Opposing surface (formed surface), 12,412,512...Conductor layer, 12c...First side (side), 12d...Second side (Side surface), 12e...Third side surface (Side surface), 12f...Fourth side surface (Side surface), 14a...First slope area (Slope area), 14b... Second slope area (Slope area), 14c... Third slope area (Slope area), 14d... Fourth slope area (Slope area), 21a... Opposing surface

Claims

1. A pair of substrates having opposing surfaces, A thermosetting adhesive layer is provided between a pair of substrates to bond the substrates together, Equipped with, A conductive layer is formed on at least one of the opposing surfaces of the pair of substrates, An inclined region is formed on at least one side surface of the conductive layer, inclined with respect to a plane perpendicular to the surface to be formed. The aforementioned thermosetting adhesive layer is formed of a thermosetting adhesive that does not become liquid at the curing temperature. Multilayer board.

2. The thermosetting adhesive constituting the thermosetting adhesive layer has a viscosity at the curing temperature that is not 1.0E+6Pa·s or less. The multilayer substrate according to claim 1.

3. At least one of the substrates has a rigid substrate, The multilayer substrate according to claim 1.

4. One of the pair of substrates has a flexible substrate, The other of the pair of substrates has a rigid substrate, The multilayer substrate according to claim 1.

5. In the conductor layer, in a cross-section intersecting the side surface where the inclined region is formed, the ratio W2 / W1 of the width W1 of the base to the width W2 of the opposite side opposite the base is 9 / 10 or less. The multilayer substrate according to claim 1.

6. The thickness of the conductor layer is 10 μm or more and 30 μm or less. A multilayer substrate according to any one of claims 1 to 5.

7. The thickness of the thermosetting adhesive layer is 15 μm or more and 50 μm or less. A multilayer substrate according to any one of claims 1 to 5.

8. The relative permittivity of the substrate and the thermosetting adhesive layer is 3.5 or less. A multilayer substrate according to any one of claims 1 to 5.

9. The aforementioned conductor layer forms an array antenna. The multilayer substrate according to claim 8.

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