JP5855936B2 - Wiring board and mounting structure thereof - Google Patents

Description

  The present invention relates to a wiring board used for electronic devices (for example, various audiovisual devices, home appliances, communication devices, computer devices, and peripheral devices thereof) and a mounting structure thereof.

  2. Description of the Related Art Conventionally, as a mounting structure used for an electronic device, a structure in which an electronic component is mounted on a wiring board is known.

  As this wiring board, for example, a wiring board having an insulating layer made of a resin material, such as that disclosed in Patent Document 1, is used.

  By the way, in the conventional wiring board, since a resin material having a larger thermal expansion coefficient than that of the electronic component is used for the insulating layer, there is a difference in thermal expansion coefficient between the wiring board and the electronic component mounted on the wiring board. It gets bigger.

  As a result, when heat is applied to the mounting structure during mounting or operation of the electronic component, thermal stress is likely to be applied between the wiring board and the electronic component mounted on the wiring board due to the difference in thermal expansion. . Therefore, there is a problem that the connection reliability between the wiring board and the electronic component to be mounted is lowered, and the electrical reliability of the mounting structure is easily lowered.

JP-A-8-116174

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a wiring board that meets the demand for improving the electrical reliability of a mounting structure and the mounting structure.

  The wiring board of the present invention includes an insulating layer and a conductive layer formed on one main surface of the insulating layer, and the insulating layer includes a plurality of first inorganic insulating particles connected to each other, and A plurality of second inorganic insulating particles having a particle size larger than that of the first inorganic insulating particles, connected to the first inorganic insulating particles at a part of each other, and connected to each other via the first inorganic insulating particles; A gap formed around the plurality of first inorganic insulating particles and the plurality of second inorganic insulating particles, and a resin portion disposed in the gap, and the one main surface of the insulating layer Are a plurality of first protrusions in which a part of the second inorganic insulating particles protrude from the one main surface of the insulating layer, and a plurality of first recesses formed between the plurality of first protrusions. And part of the conductive layer is disposed in the first recess.

  The mounting structure of the present invention includes the above-described wiring board of the present invention and an electronic component mounted on the wiring board.

According to the wiring board of the present invention, the insulating layer includes a plurality of first inorganic insulating particles and a plurality of second inorganic insulating particles having a particle size larger than the first inorganic insulating particles, and the plurality of first inorganic insulating particles. The inorganic insulating particles are connected to each other at a part thereof, and the plurality of first inorganic insulating particles are interposed between the plurality of second inorganic insulating particles, and the plurality of second inorganic insulating particles are connected to each other. Thus, since the first inorganic insulating particles and the second inorganic insulating particles constitute a structure in which the first inorganic insulating particles and the second inorganic insulating particles are bound to each other, the thermal expansion coefficient of the insulating layer can be reduced. As a result, the thermal stress applied to the connection portion between the wiring board and the electronic component mounted on the wiring board can be reduced, and as a result, the connection reliability between the wiring board and the electronic component can be improved.

  Furthermore, one main surface of the insulating layer has a plurality of first protrusions formed by protruding a part of the second inorganic insulating particles from one main surface of the insulating layer, and a plurality of first protrusions formed between the plurality of first protrusions. 1st recessed part, and a part of conductive layer is distribute | arranged to the 1st recessed part. As a result, it is possible to improve the adhesive strength between the insulating layer and the conductive layer by exerting an anchor effect between a part of the conductive layer and the first recess, and the occurrence of peeling between the insulating layer and the conductive layer is prevented. Can be reduced. Therefore, the electrical reliability of the wiring board can be improved.

  The mounting structure of the present invention includes the above-described wiring board of the present invention and an electronic component mounted on the wiring board. As a result, the electrical reliability of the mounting structure can be improved.

FIG. 1 is a cross-sectional view taken along the thickness direction showing an example of an embodiment of a mounting structure according to the present invention. FIG. 2 is a diagram obtained by inverting the top and bottom of the cross section showing the R1 portion of FIG. FIG. 3 is a view rotated to the right by 90 ° in the cross section showing the R2 portion of FIG. 2 in an enlarged manner. FIG. 4 is a view rotated 90 degrees to the left of the cross section showing the R3 portion of FIG. 3 in an enlarged manner. 5A to 5D are cross-sectional views for explaining a manufacturing process of the mounting structure shown in FIG. 6A to 6C are cross-sectional views for explaining a manufacturing process of the mounting structure shown in FIG. FIG. 7 is a cross-sectional view illustrating a manufacturing process of the mounting structure shown in FIG. FIG. 8 is a cross-sectional view taken in the thickness direction, showing an example of an embodiment of the mounting structure of the present invention different from FIG.

(First embodiment)
<Mounting structure>
Hereinafter, a mounting structure including a wiring board according to a first embodiment of the present invention will be described in detail with reference to the drawings.

  The mounting structure 1 shown in FIG. 1 is used for electronic devices such as various audiovisual devices, home appliances, communication devices, computer devices or peripheral devices thereof. The mounting structure 1 includes an electronic component 2 and a wiring board 3 on which the electronic component 2 is mounted on one main surface.

  The electronic component 2 is flip-chip mounted via bumps 4 including a conductive material such as solder, and a semiconductor element such as an IC or LSI can be used, for example. The electronic component 2 is made of a semiconductor material such as silicon, germanium, gallium arsenide, gallium arsenide phosphorus, gallium nitride, or silicon carbide. The thickness of the electronic component 2 is set to, for example, 0.05 mm or more and 1 mm or less, and the thermal expansion coefficient of the electronic component 2 is set to, for example, 3 ppm / ° C. or more and 5 ppm / ° C. or less.

  The thickness of the electronic component 2 is determined by observing the fracture surface of the electronic component 2 with a scanning electron microscope or a transmission electron microscope, measuring the length along the thickness direction (Z direction) at 10 or more points, and calculating an average value thereof. It is measured by calculating The thermal expansion coefficient is measured by a measuring method according to JISK7197-1991 using a commercially available TMA apparatus. Hereinafter, the thickness and the coefficient of thermal expansion of each member are measured in the same manner as the electronic component 2.

  The wiring substrate 3 includes a plurality of insulating layers 5, a plurality of resin layers 6 interposed between the insulating layers 5, and a plurality of conductive layers 7 spaced in the thickness direction via the insulating layers 5 and the resin layers 6. And via conductors 8 that penetrate the insulating layer 5 and the resin layer 6 in the thickness direction and electrically connect the conductive layers 7 separated in the thickness direction. The thickness of the wiring board 3 is set to 0.1 mm or more and 0.8 mm or less, for example. Further, the thermal expansion coefficient of the wiring board 3 is set to 5 ppm / ° C. or more and 10 ppm / ° C. or less.

  The insulating layer 5 functions as a supporting member that supports the conductive layer 7 and an insulating member that suppresses a short circuit between the conductive layers 7. The insulating layer 5 is formed, for example, in a flat plate shape, and the thickness thereof is set to, for example, 5 μm or more and 30 μm or less, for example, 30% or more and 80% or less of the thickness of the resin layer 6. In addition, the Young's modulus of the insulating layer 5 is set to, for example, 10 GPa or more and 100 GPa or less, and is set to, for example, 10 to 100 times the Young's modulus of the resin layer 6. Furthermore, the coefficient of thermal expansion in the thickness direction and the plane direction (XY plane direction) of the insulating layer 5 is set to, for example, 0 ppm / ° C. or more and 5 ppm / ° C. or less, and the dielectric loss tangent is set to, for example, 0.0001 or more and 0.01 or less. Has been.

  In addition, Young's modulus is measured by the measuring method according to ISO527-1: 1993 using a nanoindenter. Further, the dielectric loss tangent is measured by a resonator method according to JIS R1627-11996. Hereinafter, the Young's modulus and dielectric loss tangent of each member are measured in the same manner as the insulating layer 5.

  Moreover, the arithmetic mean roughness (Ra) of one main surface in which the conductive layer 7 of the insulating layer 5 is formed is set to, for example, not less than 100 nm and not more than 500 nm. The arithmetic average roughness (Ra) is determined according to JISB0601-2001, for example, by observing the fracture surface of the insulating layer 5 with a scanning electron microscope or a transmission electron microscope, and at the interface between the insulating layer 5 and the conductive layer 7. It is measured by drawing a straight line, selecting 10 points from the points having the largest deviation from the straight line, measuring the amount of deviation, and calculating the average value. Hereinafter, the arithmetic average roughness (Ra) of each member is measured in the same manner as one main surface of the insulating layer 5.

  Such an insulating layer 5 includes first inorganic insulating particles 9a, second inorganic insulating particles 9b having a larger particle diameter than the first inorganic insulating particles 9a, and a resin portion 10. As shown in FIGS. 2, 3, and 4 (particularly FIG. 4), the plurality of first inorganic insulating particles 9a, and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are part of each other. Connected with. Further, the first inorganic insulating particles 9a and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are connected to form a gap G, and the resin portion 10 is disposed in the gap G. As a result, the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are connected to each other to form a structure (skeleton structure) in which the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are bound to each other, thereby increasing the Young's modulus of the insulating layer 5. Can do.

  As a result, since the Young's modulus of the resin portion 10 is larger than the Young's modulus of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, the resin portion 10 disposed in the gap G has the first inorganic insulating particles 9a and By relaxing the stress applied to the second inorganic insulating particles 9b, the occurrence of cracks in the insulating layer 5 can be reduced.

  The insulating layer 5 includes the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, for example, 62 volume% or more and 75 volume% or less, and the resin portion 10 includes 25 volume% or more and 38 volume% or less. The insulating layer 5 includes 20% by volume to 90% by volume of the first inorganic insulating particles 9a with respect to the total volume of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. 2 Inorganic insulating particles 9b are contained in an amount of 10% by volume to 80% by volume.

  The first inorganic insulating particles with respect to the volume ratio of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b and the resin portion 10 of the insulating layer 5 and the total volume of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. The volume ratio of 9a and the second inorganic insulating particles 9b is measured as follows. First, the cross section of the insulating layer 5 is image | photographed with the transmission electron microscope, and each area ratio (area%) is measured using the image analysis apparatus etc. from the image | photographed image. Next, the volume ratio is calculated by calculating the average value of the measured values. Hereinafter, the volume ratio of each member is measured by the method described above.

  The first inorganic insulating particles 9a are made of an inorganic insulating material such as silicon oxide, aluminum oxide, magnesium oxide, or calcium oxide. The coefficient of thermal expansion of the first inorganic insulating particles 9a is set to, for example, 0.5 ppm / ° C. or more and 15 ppm / ° C. or less. The Young's modulus of the first inorganic insulating particles 9a is set to 10 GPa or more and 100 GPa or less. Furthermore, the dielectric loss tangent of the first inorganic insulating particles 9a is set to 0.0001 or more and 0.001 or less.

  The average particle diameter of the first inorganic insulating particles 9a is preferably 3 nm or more and 110 nm or less. As a result, since the particle diameter of the first inorganic insulating particles 9a is very small, the specific surface area is increased. Accordingly, the surface energy is increased and the surface atoms actively move, so that the first inorganic insulating particles 9a can be firmly connected to the other first inorganic insulating particles 9a.

  The average particle size of the first inorganic insulating particles 9a is measured as follows. First, the fracture surface of the insulating layer 5 is observed with a field emission electron microscope, and an enlarged cross section is photographed so as to include particles having a particle number of 20 or more and 50 or less. Next, the average particle diameter is measured by measuring and averaging the maximum diameter of each particle in the enlarged cross section. Hereinafter, the average particle diameter of each member is measured in the same manner as the first inorganic insulating particles 9a.

  The first inorganic insulating particles 9a are preferably made of an amorphous material. By making the first inorganic insulating particles 9a amorphous, it is possible to reduce the anisotropy of the thermal expansion coefficient due to the crystal structure, and to reduce the occurrence of racks in the insulating layer 5.

  On the other hand, the second inorganic insulating particles 9b are made of an inorganic insulating material such as silicon oxide, aluminum oxide, magnesium oxide, or calcium oxide. Similarly to the first inorganic insulating particles 9a, the second inorganic insulating particles 9b made of these materials have a coefficient of thermal expansion set to, for example, 0.5 ppm / ° C. or more and 15 ppm / ° C. or less. The Young's modulus is set to 10 GPa or more and 100 GPa or less, and the dielectric loss tangent is set to 0.0001 or more and 0.001 or less.

  The second inorganic insulating particles 9b are preferably formed of the same material as the first inorganic insulating particles 9a. As a result, the connection between the particles is strengthened, and the occurrence of cracks in the insulating layer 5 can be favorably reduced. The second inorganic insulating particles 9b may be formed of a material different from that of the first inorganic insulating particles 9a.

  The second inorganic insulating particles 9b are preferably made of an amorphous material. As a result, generation of cracks in the insulating layer 5 due to the crystal structure of the second inorganic insulating particles 9b can be reduced.

  Here, the second inorganic insulating particles 9b have a larger particle size than the first inorganic insulating particles 9a. As a result, in the extension of the crack in the insulating layer 5 generated by breaking the connection between the first inorganic insulating particles 9a, the crack extends around the second inorganic insulating particle 9b having a large particle size, Large energy is required for expansion. Therefore, the extension of cracks in the insulating layer 5 can be satisfactorily reduced by the second inorganic insulating particles 9b having a larger particle diameter than the first inorganic insulating particles 9a. In addition, the average particle diameter of the second inorganic insulating particles 9 is set to, for example, 0.5 μm or more and 5 μm or less.

  As described above, the resin portion 10 is arranged in the gap G of the insulating layer 5 and relieves stress applied to the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. The resin portion 10 is made of, for example, epoxy resin, bismaleimide triazine resin, cyanate resin, polyparaphenylene benzbisoxazole resin, wholly aromatic polyamide resin, polyimide resin, aromatic liquid crystal polyester resin, polyether ether ketone resin, or polyether ketone. It is formed of a resin material such as resin. Such a resin portion 10 has a Young's modulus smaller than that of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, and the Young's modulus is set to, for example, 0.2 GPa or more and 10 GPa or less. Is set to 0.005 or more and 0.02 or less, for example, and the coefficient of thermal expansion in the planar direction and thickness direction of the resin portion 10 is set to 20 ppm / ° C. or more and 100 ppm / ° C. or less, for example.

  On the other hand, the resin layer 6 functions as a support member that supports the conductive layer 7 and an insulating member that suppresses a short circuit between the conductive layers 7, and contains 40% by volume to 100% by volume of the resin material. Therefore, since the resin layer 6 has a lower Young's modulus than the insulating layer 5 inorganic insulating material, the stress applied to the insulating layer 5 can be reduced. Therefore, generation of cracks along the thickness direction of the insulating layer 5 can be reduced, and disconnection of the conductive layer 7 due to the cracks can be reduced.

  The resin material of the resin layer 6 is, for example, epoxy resin, bismaleimide triazine resin, cyanate resin, polyparaphenylene benzbisoxazole resin, wholly aromatic polyamide resin, polyimide resin, aromatic liquid crystal polyester resin, polyether ether ketone resin, or poly What was formed with resin materials, such as ether ketone resin, can be used.

  Moreover, it is desirable that the resin layer 6 does not include a base material made of, for example, fibers. As a result, the increase in thickness due to the base material is reduced to reduce the thickness of the wiring board 3, and the unevenness on the upper surface of the wiring board 3 due to the base material is reduced to flatten both main surfaces of the wiring board 3. can do. The base material is a woven fabric or non-woven fabric or fiber arranged in one direction.

  The thickness of the resin layer 6 is set to, for example, 5 μm or more and 30 μm or less, the Young's modulus of the resin layer 6 is set to, for example, 0.2 GPa or more and 20 GPa or less, and the dielectric loss tangent of the resin layer 6 is, for example, 0.01 or more. The coefficient of thermal expansion in the planar direction and the thickness direction of the resin layer 6 is set to 20 ppm / ° C. or more and 100 ppm / ° C. or less, for example.

  In addition, it is desirable that an inorganic insulating filler 9c formed of an inorganic insulating material is dispersed and disposed in the resin layer 6. As a result, the Young's modulus of the resin layer 6 can be set lower than the Young's modulus of the insulating layer 5, and the thermal expansion coefficient of the resin layer 6 can be reduced. Moreover, the difference in material characteristics between the resin layer 6 and the inorganic insulating layer 5 can be reduced, and the occurrence of peeling between the resin layer 6 and the inorganic insulating layer 5 can be reduced.

As such an inorganic insulating filler 9c of the resin layer 6, for example, a material formed of an inorganic insulating material such as silicon oxide, aluminum oxide, aluminum nitride, aluminum hydroxide, or calcium carbonate can be used. In particular, it is desirable to use the same inorganic insulating material as the inorganic insulating material constituting the insulating layer 5. As a result, the difference in material characteristics between the resin layer 6 and the insulating layer 5 can be further reduced.

  In addition, the average particle diameter of the inorganic insulating filler 9c is set to, for example, 0.5 μm or more and 5.0 μm or less, and the thermal expansion coefficient of the inorganic insulating filler 9c is set to, for example, 0 ppm / ° C. or more and 15 ppm / ° C. or less. Moreover, the resin layer 6 contains the inorganic insulating filler 9c, for example, 10 volume% or more and 60 volume% or less.

  The conductive layer 7 functions as a ground wiring, a power supply wiring, and / or a signal wiring. The conductive layer 7 has one main surface in contact with the insulating layer 5 and the other main surface and side surfaces in contact with the resin layer 6. As the conductive layer 7, for example, a layer formed of a conductive material such as copper, silver, gold, aluminum, nickel, or chromium can be used, the thickness is set to 3 μm or more and 20 μm or less, and the thermal expansion coefficient is, for example, 5 ppm. / ° C. or more and 25 ppm / ° C. or less.

  Moreover, the thickness of the conductive layer 7 is set to 2 μm or more and 30 μm or less, and the distance between the adjacent conductive layers 7 is set to 2 μm or more and 30 μm or less. The distance between the adjacent conductive layers 7 is determined by, for example, observing the fractured surface of the conductive layer 7 with a scanning electron microscope or a transmission electron microscope, and measuring the distance between the adjacent conductive layers 7 at a plurality of locations in the enlarged cross section. It is measured by measuring and averaging. Hereinafter, the distance between adjacent members is measured in the same manner as the conductive layer 7.

  The via conductor 8 connects the conductive layers 7 separated from each other in the thickness direction to each other, and is formed in a columnar shape that becomes narrower from the lower surface side to the upper surface side of the wiring substrate 3. Therefore, the wiring density can be increased by miniaturizing the wiring on the upper surface of the wiring substrate 3. As the via conductor 8, for example, a conductor formed of a conductive material such as copper, silver, gold, aluminum, nickel, or chromium can be used. The thermal expansion coefficient of the via conductor 8 is set to, for example, 14 ppm / ° C. or more and 18 ppm / ° C. or less.

  By the way, compared with the resin layer 6, the insulating layer 5 in this embodiment contains many 1st inorganic insulating particles 9a and 2nd inorganic insulating particles 9b which consist of inorganic insulating materials, and has an inorganic insulating material as a main component. Therefore, since the inorganic insulating material has a smaller thermal expansion coefficient than the resin material, the thermal expansion coefficient of the insulating layer 5 is reduced, and the thermal expansion between the wiring board 3 including the insulating layer 5 and the electronic component 2 is reduced. The amount difference can be reduced. As a result, the connection reliability between the electronic component 2 and the wiring board 3 can be improved, and consequently the electrical reliability of the mounting structure 1 can be improved.

  The insulating layer 5 has a skeleton structure as described above. Therefore, when heat is applied to the insulating layer 5, the first inorganic insulating particles 9a and the second inorganic insulating particles 9b restrain each other and suppress thermal expansion of the resin portion 10 without flowing. Compared with the case where the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are dispersed, the thermal expansion of the insulating layer 5 can be favorably reduced. As a result, the thermal expansion coefficient of the wiring board 3 can be reduced.

  Further, as shown in FIGS. 2 and 3, in the insulating layer 5, one main surface on which the conductive layer 7 is formed has a plurality of first convex portions 11a formed by protruding part of the second inorganic insulating particles 9b. The first concave portions 11b formed between the plurality of first convex portions 11a are provided, and a part of the conductive layer 7 is disposed in the first concave portions 11b. Therefore, by exerting an anchor effect between part of the conductive layer 7 and the first recess 11b, the adhesive strength between the insulating layer 5 and the conductive layer 7 can be improved, and the insulating layer caused by thermal stress. The occurrence of peeling between the conductive layer 5 and the conductive layer 7 can be reduced.

Moreover, it is desirable that the conductive layer 7 is in direct contact with the second inorganic insulating particles 9b. as a result,
Since the second inorganic insulating particles 9b are made of an inorganic insulating material having a dielectric loss tangent smaller than that of the resin material, the conductive layer 7 can reduce dielectric loss as compared with a conventional resin substrate. Therefore, the conductive layer 7 can transmit a high frequency signal satisfactorily.

  In addition, the second inorganic insulating particles 9b particularly preferably contain silicon oxide. Since silicon oxide has a lower dielectric loss tangent than other inorganic insulating materials, the signal transmission characteristics of the conductive layer 7 formed on the insulating layer 5 can be improved. In this case, the second inorganic insulating particle 9b contains 97% by mass to 100% by mass of silicon oxide, for example.

  In addition, the height of the 1st convex part 11a is 50 nm or more and 1 micrometer or less, for example, and the distance between the 1st convex parts 11a is set to 0.5 micrometer or more and 5 micrometers or less, for example.

  In addition, the height of the 1st convex part 11a observes the torn surface of the conductive layer 7 with a scanning electron microscope or a transmission electron microscope, the height of the 1st convex part 11a of several places, and the adjacent 1st convex part. It is measured by measuring and averaging the distance of 11a. Hereinafter, the height of each member and the distance between adjacent members are also measured in the same manner.

  As shown in FIGS. 3 and 4, in the insulating layer 5, the bottom surface of the first recess 11b has a plurality of second protrusions 12a made of a plurality of first inorganic insulating particles 9a and the second protrusions 12a. It is desirable that a part of the conductive layer 7 is disposed in the first recess 11b and the second recess 12b. As a result, a part of the conductive layer 7 is arranged so as to be held not only by the first concave portion of the insulating layer 5 but also by the second concave portion 12b. Between the two, an additional anchor effect can be obtained, and the adhesive strength between the insulating layer 5 and the conductive layer 7 can be improved.

  The conductive layer 7 is preferably in direct contact with the first inorganic insulating particles 9a. As a result, since the second inorganic insulating particles 9a are made of an inorganic insulating material having a dielectric loss tangent smaller than that of the resin material, the conductive layer 7 can reduce dielectric loss compared to a conventional resin substrate. Therefore, the conductive layer 7 can transmit a high frequency signal satisfactorily.

  The first inorganic insulating particles 9a particularly preferably contain silicon oxide. Since silicon oxide has a lower dielectric loss tangent than other inorganic insulating materials, the signal transmission characteristics of the conductive layer 7 formed on the insulating layer 5 can be improved. In this case, the first inorganic insulating particles 9a contain 97% by mass or more and 100% by mass or less of silicon oxide, for example.

  The shape of the first inorganic insulating particles 9a is preferably spherical as in this embodiment. As a result, the filling density of the first inorganic insulating particles 9a can be increased, and the internal structure of the insulating layer 5 can be made dense and uniform. As a result, the 2nd convex part 12a and the 2nd recessed part 12b can be formed more uniformly, the dielectric loss of the conductive layer 7 distribute | arranged to the said location can be reduced, and a high frequency signal can be transmitted favorably.

  The arithmetic average roughness (Ra) of the bottom surface of the first part 11b is, for example, 30 nm or more and 0.5 μm or less, and the distance between the second protrusions 12a is set to, for example, 10 nm or more and 200 nm.

  Thus, since the 2nd convex part 12a and the 2nd recessed part 12b can form very fine unevenness | corrugation compared with the conventional resin substrate, the conductive layer 7 can also be refined | miniaturized.

The second inorganic insulating particles 9b constituting the first convex portion 11a have a first portion 13a that forms the first convex portion 11a and a second portion 13b that has entered the insulating layer 5, and the first portion The surface of 13 a has a plurality of protrusions 14, and a part of the conductive layer 7 is desirably disposed between the plurality of protrusions 14. As a result, since the conductive layer 7 is arranged so as to be held between the protrusions 14 of the second inorganic insulating particles 9b, an anchor effect is exerted between the conductive layer 7 and the protrusions 14, and the second 2 Adhesive strength between the inorganic insulating particles 9b and the conductive layer 7 can be increased.

  In addition, since a part of the second inorganic insulating particles 9b is arranged in the insulating layer 5, it is held by the plurality of first inorganic insulating particles 9a and the resin portion 10 so that the insulating layer 5 and the conductive layer 7 It is possible to satisfactorily reduce the separation of the second inorganic insulating particles 9b from the insulating layer 5 due to the thermal stress applied to the connection portion.

  In addition, the height of the protrusion 14 of the second inorganic insulating particle 9b is set to, for example, 10 nm or more and 300 nm or less. The second portion 13b is set to, for example, 5% by volume or more and 50% by volume or less with respect to the second inorganic insulating particles 9b.

  The surface of the second portion 13b of the second inorganic insulating particle 9b constituting the first convex portion 11a is preferably curved. As a result, the stress applied to the second portion 13b side of the second inorganic insulating particle 9b can be dispersed. Therefore, the generation of cracks starting from the surface of the second inorganic insulating particles 9b can be reduced. As a result, the disconnection of the conductive layer 7 caused by the extension of the cracks can be satisfactorily reduced.

  In addition, among the second inorganic insulating particles 9b, some of the second inorganic insulating particles 9b constitute the first convex portion 11a on one main surface of the insulating layer 5, and the other part of the second inorganic insulating particles 9b. The particles 9b are preferably disposed in the insulating layer 5 and spherical. As a result, the adhesive strength between the insulating layer 5 and the conductive layer 7 can be improved on one main surface of the insulating layer 5, and the surface of the second inorganic insulating particles 9 b becomes smooth in the insulating layer 5. The stress on the surface is dispersed, and the generation of cracks starting from the surface of the second inorganic insulating particles 9b can be reduced.

  The gap G of the insulating layer 5 preferably has a first region 15a where the resin portion is disposed and a second region 15b where a part of the conductive layer 7 is disposed. As a result, not only the anchor effect in the plane direction but also the anchor effect in the thickness direction can be expected at the connection surface between the insulating layer 5 and the conductive layer 7.

  That is, the gap G is formed in the insulating layer 5 as described above. The gap G is formed in the x, y, and z directions because the plurality of first inorganic insulating particles 9a and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are partially connected to each other. Each can be formed as an open pore and a network. Then, a structure in which a part of the conductive layer 7 enters the gap G extending in a mesh shape may be possible.

  Therefore, since the first inorganic insulating particles 9 a in the insulating layer 5 are arranged on a part of the conductive layer 7 and a part of the conductive layer 7 is arranged in the insulating layer 5, the insulating layer 5 And the conductive layer 7 are formed so as to be intertwined with each other. As a result, not only the planar direction but also the stress in the thickness direction can be counteracted, and the occurrence of peeling of the conductive layer 7 due to thermal stress can be reduced satisfactorily. In addition, since the adhesion area between the conductive layer 7 and the first inorganic insulating particles 9a is also increased, the occurrence of peeling between the conductive layer 7 and the first inorganic insulating particles 9a can be reduced. Generation | occurrence | production of peeling with the layer 7 can be reduced favorably.

Note that the width of the gap G of the insulating layer 5 is set to, for example, not less than 10 nm and not more than 300 nm. The width of the gap G is formed by observing a cross section of the insulating layer 5 with a transmission electron microscope and forming the plurality of first inorganic insulating particles 9a with each other and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. A cross-section enlarged so as to include the gap G between 20 and 50 is photographed, and the average value of the maximum gaps of the gap G in the photographed magnified cross-section is referred to, and this average value is regarded as the width of the gap G.

  Further, the ratio of the conductive layer 7 disposed in the gap G of the insulating layer 5 is desirably 0.1% or more and 10% or less of the thickness of the conductive layer, for example. As a result, it is possible to improve the high-frequency signal transmission characteristics of the conductive layer 7 while reducing the insulation between the insulating layers 5 and to reduce the occurrence of peeling of the conductive layer 7. The ratio of the conductive layer 7 disposed in the gap G of the insulating layer 5 is determined by, for example, observing the fracture surface of the insulating layer 5 with a transmission electron microscope and conducting the conductive layer 7 disposed in the gap G of the insulating layer 5. Is taken as an average of the ratio of the ratio of the enlarged section taken in the gap G of the conductive layer 7 to the gap G of the insulating layer 5. It is regarded as a ratio of the conductive layer 7 to be formed.

  The boundary surface between the conductive layer 7 disposed in the gap G and the resin portion 10 is preferably curved. As a result, the stress concentration on the resin part 10 can be relaxed, and the generation and progress of cracks in the insulating layer 5 can be reduced.

  Further, the bottom surface of the first recess 11a has a recess 16 having a curved inner surface, and the radius of curvature of the recess 16 is the same as the radius of curvature of the surface of the second portion 13b of the second inorganic insulating particle 9b. It is desirable that As a result, an anchor effect is exhibited between the conductive layer 7 and the recess 16, the adhesive strength between the two is improved, and the occurrence of peeling of the conductive layer 7 can be reduced satisfactorily. In addition, such a hollow part 16 is formed by peeling the second inorganic insulating particles 9b.

  Thus, the mounting structure 1 described above exhibits a desired function by driving or controlling the electronic component 2 based on the power supply and signals supplied via the wiring board 3.

<Method for manufacturing mounting structure>
Next, a method for manufacturing the mounting structure 1 described above will be described with reference to FIGS.

  (1) An inorganic insulating sol 5x having a solid content including the first inorganic insulating particles 9a and the second inorganic insulating particles 9b and a solvent in which the solid content is dispersed is prepared.

  The inorganic insulating sol 5x includes, for example, a solid content of 10% to 50% by volume and a solvent of 50% to 90% by volume. By setting the solid content to 10% by volume or more, the viscosity of the inorganic insulating sol 5x is kept low, and by setting the solid content to 50% by volume or less, the productivity of the insulating layer formed from the inorganic insulating sol 5x is improved. Highly maintainable.

  The solid content of the inorganic insulating sol 5x includes, for example, the first inorganic insulating particles 9a of 20% by volume to 90% by volume and the second inorganic insulating particles 9b of 10% by volume to 80% by volume. Thereby, generation | occurrence | production of the crack in the insulating layer 5 can be effectively reduced in the process of (3) mentioned later.

  In addition, the 1st inorganic insulating particle 9a can be produced by refine | purifying silicic acid compounds, such as sodium silicate aqueous solution (water glass), and depositing a silicon oxide chemically, for example. In this case, since the first inorganic insulating particles 9a can be produced under low temperature conditions, the first inorganic insulating particles 9a in an amorphous state can be produced.

On the other hand, if the second inorganic insulating particles 9b are made of silicon oxide, for example, a silicate compound such as a sodium silicate aqueous solution (water glass) is purified, and a solution in which silicon oxide is chemically deposited is sprayed into the flame. And it can produce by heating 800 degreeC or more and 1500 degrees C or less, reducing formation of an aggregate. Therefore, since the second inorganic insulating particles 9b have a larger particle size than the first inorganic insulating particles 9a, it is easy to reduce the formation of aggregates during high temperature heating,
It can be easily produced by high-temperature heating, and consequently the hardness can be easily increased.

  Moreover, it is desirable that the heating time for producing the second inorganic insulating particles 9b is set to 1 second or more and 180 seconds or less. As a result, by shortening the heating time, the crystallization of the second inorganic insulating particles 9b can be suppressed and the amorphous state can be maintained even when heated to 800 ° C. or higher and 1500 ° C. or lower.

  On the other hand, the solvent contained in the inorganic insulating sol 5x is, for example, methanol, isopropanol, n-butanol, ethylene glycol, ethylene glycol monopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, xylene, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethyl An organic solvent containing acetamide and / or a mixture of two or more selected from these may be used.

  (2) As shown in FIG. 5A, a support sheet 17 formed of a resin material or a metal foil is prepared, and an inorganic insulating sol 5 x is applied to the main surface of the support sheet 17.

  The inorganic insulating sol 5x can be applied using, for example, a dispenser, a bar coater, a die coater, or screen printing. At this time, as described above, since the solid content of the inorganic insulating sol 5x is set to 50% by volume or less, the viscosity of the inorganic insulating sol 5x is set low, and the flatness of the coated inorganic insulating sol 5x is increased. can do.

  Moreover, since the particle diameter of the first inorganic insulating particles 9a is set to 3 nm or more as described above, the viscosity of the inorganic insulating sol 5x is also reduced favorably by this, and the applied inorganic insulating sol 5x Flatness can be improved.

  (3) The inorganic insulating sol 5x is dried to evaporate the solvent.

  Here, the inorganic insulating sol 5x contracts as the solvent evaporates, and the solvent is contained in the gap G between the first and second inorganic insulating particles 9a and 9b, and the first and second inorganic insulating particles 9a. 9b itself is not included. For this reason, if the inorganic insulating sol 5x contains the second inorganic insulating particles 9b having a large particle size, the area filled with the solvent is reduced correspondingly, and the inorganic insulating sol is evaporated when the solvent of the inorganic insulating sol 5x evaporates. The 5x shrinkage is reduced. That is, the contraction of the inorganic insulating sol 5x is regulated by the second inorganic insulating particles 9b. As a result, the generation of cracks due to the shrinkage of the inorganic insulating sol 5x can be reduced. Even if a crack occurs, the extension of the crack can be prevented by the second inorganic insulating particles 9b having a large particle diameter.

  The inorganic insulating sol 5x is dried by heating and air drying, for example. The drying temperature is set to, for example, 20 ° C. or more and lower than the boiling point of the solvent (the boiling point of the lowest boiling solvent when two or more solvents are mixed), and the drying time is, for example, 20 seconds to 30 minutes. Set to As a result, the boiling of the solvent is reduced, the extrusion of the first and second inorganic insulating particles 9a and 9b is suppressed by the pressure of the bubbles generated during the boiling, and the distribution of the particles can be made more uniform. It becomes.

  (4) An inorganic insulating structure in which the solid content of the remaining inorganic insulating sol 5x is heated so that the first inorganic insulating particles 9a and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are connected to each other by a part of each other. A body 5 'is produced.

Here, the inorganic insulating sol 5x in the present embodiment has the first inorganic insulating particles 9a having a small particle size. As a result, even if the heating temperature of the inorganic insulating sol 5x is relatively low, for example, below the crystallization start temperature of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, the first inorganic insulating particles 9a It can be firmly connected.

  The temperature at which the first inorganic insulating particles 9a can be firmly connected is, for example, about 250 ° C. when the particle diameter of the first inorganic insulating particles 9a is set to 110 nm or less, and the particle diameter is 15 nm or less. Is set to about 150 ° C. The crystallization start temperature of silicon oxide contained in the first and second inorganic insulating particles 9a and 9b is about 1300 ° C.

  The heating temperature of the inorganic insulating sol 5x is preferably set to be lower than the crystallization start temperature of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. As a result, the crystallized particles can be prevented from shrinking due to phase transition, and the occurrence of cracks in the insulating layer 5 can be reduced.

  Further, by heating at such a low temperature, the first inorganic insulating particles 9a and the second inorganic insulating particles 9b maintain the shape of the particles, while the first inorganic insulating particles 9a and the first inorganic insulating particles 9a and the first inorganic insulating particles 9a 2 The inorganic insulating particles 9b can be connected only in the proximity region. As a result, the first inorganic insulating particles 9a and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b can be connected. As a result, the gap G between the first inorganic insulating particles 9a can be easily formed. Can be formed.

  In addition, as for the heating of the inorganic insulating sol 5x, it is desirable that the temperature is set to, for example, 100 degrees to less than 700 degrees, and the time is set to, for example, 0.5 hours to 24 hours.

  (5) As shown in FIG. 5B, a resin precursor 6x made of uncured resin is formed on the main surface of the inorganic insulating structure 5 ′ opposite to the support sheet 17, and the support sheet 17 and the inorganic insulation are formed. A laminated sheet 18 including the structure 5 ′ and the resin precursor 6x is created. Next, the laminated sheet 18 is laminated on one main surface of the support 19, and the laminated body 20 is heated and pressurized to cure the resin precursor 6x, whereby a resin layer is obtained as shown in FIG. 6 is formed. At this time, the insulating layer 5 in which the resin material of the resin precursor 6 x is filled in the gap G of the inorganic insulating structure 5 ′ is formed on the resin layer 6. Thereafter, the support sheet 17 is peeled from the insulating layer 5 to expose one main surface of the insulating layer 5.

  In addition, the resin precursor 6ax can make the 1st resin layer 6a desired thickness by adjusting the thickness suitably. The uncured resin is in an A-stage or B-stage according to ISO 472: 1999.

  Moreover, as for the heat pressurization of the laminated body 20, it is desirable that the temperature is set to be equal to or higher than the curing start temperature of the resin contained in the resin layer 6 and lower than the thermal decomposition temperature. Specifically, the heat and pressure of the laminate 20 is set such that the temperature is set to 170 ° C. or higher and 230 ° C. or lower, the pressure is set to 2 MPa or higher and 3 MPa or lower, and the time is set to 0.5 hours or longer and 2 hours or shorter, for example. Is set.

  Here, in order to fluidize the resin material of the resin precursor 6x by heating and pressurizing, the gap G of the inorganic insulating structure 5 'is satisfactorily filled.

  The curing start temperature is a temperature at which the resin becomes a C-stage according to ISO 472: 1999. The thermal decomposition temperature is a temperature at which the mass of the resin is reduced by 5% in thermogravimetry according to ISO11358: 1997.

(6) As shown in FIG. 5D, a via hole 8x that penetrates the insulating layer 5 and the resin layer 6 in the thickness direction is formed. Specifically, a via hole 8x penetrating the insulating layer 5 and the resin layer 6 is formed by irradiating one main surface of the insulating layer 5 with laser light using, for example, a YAG laser device or a carbon dioxide gas laser device.

  (7) The exposed main surface of the insulating layer 5 is polished. As a result, a plurality of first protrusions 11a formed by projecting part of the second inorganic insulating particles 9b from one main surface of the insulating layer 5 and a plurality of first protrusions formed between the plurality of first protrusions 11a. A recess 11b can be formed. The bottom surface of the first recess 11b of the insulating layer 5 has a plurality of second protrusions 12a made of the first inorganic insulating particles 9b and a plurality of second protrusions formed between the plurality of second protrusions 12a. A recess 12b can be formed. Furthermore, the protrusion 14 can be formed on the surface of the second inorganic insulating particle 9b.

  Polishing of one main surface of the insulating layer 5 is performed using, for example, a buff. Specifically, a mixture of an abrasive and water is applied on one main surface of the insulating layer 5 and then mechanically polished using a buff, for example, for 20 seconds to 5 minutes. The buff is made of a flexible material such as cloth, leather, or rubber, and the abrasive is made of, for example, alumina or silicon carbide having an average particle diameter of 0.2 μm or more and 1 μm or less. As a result, since the buff is soft and the abrasive is fine, fine irregularities can be formed when polished, and the fine conductive layer 7 can be satisfactorily formed in the formation of the conductive layer 7 described later. Can do.

  (8) One main surface of the insulating layer 5 and the via hole are desmeared.

  Specifically, the desmear treatment is performed by impregnating the laminate 20 with the permanganic acid solution within 2 minutes to 10 minutes, for example. In this step, since the permanganic acid solution dissolves the resin material, not only the desmearing process is favorably performed in the via hole 8x but also a part of the resin portion 10 disposed in the gap G of the insulating layer 5 can be dissolved. it can. As a result, the conductive layer can be satisfactorily formed in the gap G in the subsequent formation of the conductive layer 7.

  Here, since the first inorganic insulating particles 9a and the second inorganic insulating particles 9b are hardly soluble in the permanganic acid solution, when the laminate 20 is impregnated in the permanganic acid solution, in the insulating layer 5, Only the resin portion 10 in the gap G is removed. As a result, fine irregularities similar to the size of the gap G can be formed on one main surface of the insulating layer 5. That is, desmearing can be sufficiently performed in the via hole 8x, and fine unevenness can be satisfactorily formed on one main surface of the insulating layer 5.

  Further, since the first inorganic insulating particles 9a are formed in a spherical shape, the insulating layer 5 is densely formed. Therefore, when the laminate 20 is impregnated with a permanganic acid solution, it is possible to suppress the removal of the resin portion 10 extremely. As a result, it is possible to satisfactorily reduce an electrical short circuit between the conductive layers 7 formed with the insulating layer 5 interposed therebetween by extremely removing the resin portion 10.

  (9) As shown in FIG. 6A, the conductive layer 7 and the via conductor 8 are formed on one main surface of the insulating layer 5 and the via hole 8x.

  The conductive layer 7 is deposited by using, for example, a photolithography technique, an etching method, or the like after depositing a conductive material using, for example, an electroless plating method, an electroplating method, a vapor deposition method, a CVD method, or a sputtering method. The conductive material can be formed by patterning.

  The via conductor 8 can be formed by depositing a conductive material on the inner wall of the via hole 8x using, for example, an electroless plating method, an electroplating method, a vapor deposition method, a CVD method, or a sputtering method.

  (10) Thereafter, if necessary, the steps (1) to (9) are repeated as shown in FIG. 6B, and the support 19 is peeled off as shown in FIG. The wiring board 3 having the number of layers can be manufactured.

(Mounting structure)
(11) As shown in FIG. 7, the electronic component 2 is flip-chip mounted on the wiring board 3 via the bumps 4 on the surface of the wiring board 3 where the resin layer 5 is exposed, as shown in FIG. The mounting structure 1 can be produced.

(Second Embodiment)
Next, a second example (second embodiment) of the embodiment of the wiring board and the mounting structure of the present invention will be described in detail below. In addition, description is abbreviate | omitted regarding the structure similar to 1st Embodiment mentioned above.

<Mounting structure>
In the insulating layer 5 according to the mounting structure of the second embodiment, the resin portion 10 disposed in the gap G of the insulating layer 5 is disposed in the first resin portion disposed in the gap G and the gap G. A plurality of first inorganic insulating particles 9a, a connection portion between the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, and a surface of the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. Second resin portion. The conductive layer 7 is in contact with the first resin portion 10 and the second resin portion, and the second resin portion is a boundary surface between the conductive layer 7, the first inorganic insulating particles 9a, and the second inorganic insulating particles 9b. Is intervening.

  As a result, the second convex portions 11a and the second resin portions are arranged at the connection portions between the plurality of first inorganic insulating particles 9a and between the first inorganic insulating particles 9a and the second inorganic insulating particles 9b. Since the second convex portion 12a is reinforced, a part of the conductive layer 7, the first concave portion 11b formed by the plurality of first convex portions 11a and the second concave portion 12b formed by the plurality of second convex portions 12a. Further anchor effect is exhibited between the two. In addition, since the conductive layer 7 has the second resin portion on the boundary surface between the conductive layer 7 and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, it can be bonded well.

  The first resin portion is made of a resin material similar to that of the resin layer 6, and the second resin portion is made of a resin material such as an epoxy resin, a cyanate resin, or a bismaleimide triazine resin.

  In particular, if the second resin portion is formed of a cyanate resin or a bismaleimide triazine resin, the adhesive strength between the conductive layer 7 and the first inorganic insulating particles 9a and the second inorganic insulating particles 9b can be improved.

  Further, it is desirable that the first resin portion be included in the gap G of the insulating layer 5 by 80 volume% or more and 95 volume% or less, and the second resin section be included by 5 volume% or more and 20 volume% or less.

  As a result, the conductive layer 7 not only adheres well to the first inorganic insulating particles 9a and the second inorganic insulating particles 9b, but also can transmit high frequency signals.

<Method for manufacturing mounting structure>
Next, the manufacturing method of the mounting structure 1 of the second embodiment described above will be described. In addition, description is abbreviate | omitted regarding the method similar to 1st Embodiment mentioned above.

In the step (5) described above, the gap G of the inorganic insulating structure 5 ′ is filled with a liquid resin,
It is desirable to dry this liquid resin.

  As described above, if the liquid resin is dried after being impregnated with the liquid resin, when the liquid content of the liquid resin evaporates during the drying process of the liquid resin, the liquid content is reduced to the first inorganic insulating particles 9a and the first inorganic resin particles 9a. 2 Since the surface of the inorganic insulating particle 9b flows and evaporates, the resin component that flows together with the liquid component adheres to the periphery of the gap G. And since resin part has good wettability with respect to particle | grains, such as an inorganic insulation particle | grains especially, several 1st inorganic insulation particles 9a of inorganic insulation structure 5 'and several 1st inorganic insulation particles 9a and It intervenes in the connecting portion between the plurality of second inorganic insulating particles 9 b and the connecting portion between the first inorganic insulating particles 9 a, the second inorganic insulating particles 9 b, and the support sheet 17. As a result, the second resin portion can be formed in the connecting portion by thermosetting the resin component. After that, by laminating the resin precursor 6x, the first resin part can be formed by filling the remaining part of the gap G with the resin material.

  As described above, by forming the second resin portion in advance in the inorganic insulating structure 5 ′, the adhesive strength between the inorganic insulating structure 5 ′ and the support sheet 17 is improved, and a plurality of first inorganic insulations are provided. It is possible to reinforce the connecting portions between the particles 9a and the plurality of first inorganic insulating particles 9a and the plurality of second inorganic insulating particles 9b, to improve the handling property and to improve the yield.

  Such a 2nd resin part is formed with the resin material which consists of cyanate resin and bismaleimide triazine resin, for example. Examples of the liquid resin include a resin material mixed with a solvent at 50% or less with respect to the solvent, or a liquid resin only.

  In addition, liquid resin is resin in the state of the A-stage according to ISO472: 1999.

  Of these, if the resin material is a cyanate resin or a bismaleimide triazine resin, these resins are hardly soluble in the permanganic acid solution. Therefore, in the desmear process, the first inorganic insulating particles 9a and the second inorganic insulating particles 9a and 2b are used. This is desirable in that it remains on the surface of the inorganic insulating particles 9b and can improve the adhesive strength between the conductive layer 7, the first inorganic insulating particles 9a, and the second inorganic insulating particles 9b to be formed later.

  The present invention is not limited to the above-described embodiments, and various modifications, improvements, combinations, and the like can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment of the present invention, the configuration using the coreless substrate as the wiring substrate has been described as an example. However, as shown in FIG. 8, the wiring substrate may include the core substrate.

  Further, in the above-described embodiment of the present invention, description of the solder resist layer is omitted, but the wiring board may have a solder resist layer containing a resin material on the upper and lower surfaces.

  Moreover, although description about the underfill was abbreviate | omitted in embodiment of this invention mentioned above, you may have an underfill between a wiring board and an electronic component.

  In the embodiment of the present invention described above, the electronic component is mounted on the main surface where the resin layer of the wiring board is exposed, but the electronic component is mounted on the main surface where the insulating layer of the wiring board is exposed. It doesn't matter.

DESCRIPTION OF SYMBOLS 1 Mounting structure 2 Electronic component 3 Wiring board 4 Bump 5 Insulating layer 5 'Inorganic insulating structure 5x Inorganic insulating sol 5
6 resin layer 6x resin precursor 7 conductive layer 8 via conductor 8x via hole 9a first inorganic insulating particle 9b second inorganic insulating particle 10 resin part 11a first convex part 11b first concave part 12a second convex part 12b second concave part 13a 1st part 13b 2nd part 14 Protrusion part 15a 1st area | region 15b 2nd area | region 16 Recessed part 17 Support sheet 18 Laminated sheet 19 Support body 20 Laminated body

Claims (8)

An insulating layer, and a conductive layer formed on one main surface of the insulating layer,
The insulating layer has a plurality of first inorganic insulating particles connected in part to each other, a particle size larger than the first inorganic insulating particles, and connected to the first inorganic insulating particles in part from each other, A plurality of second inorganic insulating particles connected to each other via the first inorganic insulating particles, a plurality of the first inorganic insulating particles and a gap formed around the plurality of the second inorganic insulating particles, and the gap And a resin part arranged in the
The one principal surface of the insulating layer is formed between a plurality of first protrusions in which a part of the second inorganic insulating particles protrudes from the one principal surface of the insulation layer and the plurality of first protrusions. A plurality of first recesses formed,
A part of the conductive layer is a wiring board disposed in the first recess. The wiring board according to claim 1,
The bottom surface of the first concave portion includes a plurality of second convex portions made of the first inorganic insulating particles, and a plurality of second concave portions formed between the plurality of second convex portions,
A part of the conductive layer is a wiring board disposed in the first recess and the second recess. The wiring board according to claim 1,
The second inorganic insulating particles constituting the first convex portion have a first portion forming the first convex portion, and a second portion entering the insulating layer,
The surface of the first portion has a plurality of protrusions,
A part of the conductive layer is a wiring board disposed between the plurality of protrusions. The wiring board according to claim 3,
A wiring board in which a surface of the second portion in the second inorganic insulating particles constituting the first convex portion is curved. The wiring board according to claim 3,
Among the plurality of second inorganic insulating particles, some of the second inorganic insulating particles constitute the first convex portion on the one main surface of the insulating layer, and the other part of the second inorganic insulating particles. The inorganic insulating particles are disposed inside the insulating layer and have a spherical shape. The wiring board according to claim 1,
The gap has a first area in which the resin portion is disposed and a second area in which a part of the conductive layer is disposed. The wiring board according to claim 1,
The second inorganic insulating particles constituting the first convex portion have a first portion forming the first convex portion, and a second portion entering the insulating layer,
The surface of the second portion is curved.
The bottom surface of the first recess has a recess 16 whose inner surface is curved,
The wiring board in which the radius of curvature of the recess 16 is the same as the radius of curvature of the surface of the second portion of the second inorganic insulating particle.   A mounting structure comprising the wiring board according to claim 1 and an electronic component mounted on the wiring board.

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