JP2013229524A - Multilayer wiring board and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer wiring board having a good connection reliability, capable of preventing surely coming-off of a via.SOLUTION: A multilayer wiring board 10 has a build-up structure formed of a plurality of resin insulation layers 33 to 36 alternately laminated with a plurality of conductor layers 42, thereby forming a multi-layer. The resin insulation layers 33 to 36 contain glass cloths 51 in inner layers of resin insulation materials 50. Via holes 43 are formed on resin insulation materials 50 of resin insulation layers 33 to 36, and a through hole 52 is formed on a position corresponding to the via hole 43 in the glass cloth 51. A part to be an open edge of the through hole 52 on the glass cloth 51, inwardly projects from an inner wall of the via hole 43 and bites into a side part of a via conductor 44. An inner diameter of the via hole 43 has the largest width in a region adjacent to the glass cloth 51 on the inner wall of the via hole 43.

Description

  The present invention relates to a multilayer wiring board having a build-up structure in which a plurality of resin insulation layers and a plurality of conductor layers are alternately laminated to form a multilayer, and a method for manufacturing the same.

  In recent years, with the miniaturization of electrical equipment, electronic equipment, etc., miniaturization and high density are required for multilayer wiring boards and the like mounted on these equipments. As this multilayer wiring board, a wiring board manufactured by a so-called build-up method in which a plurality of resin insulation layers and a plurality of conductor layers are alternately laminated and integrated has been put into practical use (for example, see Patent Document 1). ). In the multilayer wiring board of Patent Document 1, the lower conductor layer and the upper conductor layer of the resin insulation layer are connected via via conductors formed in the resin insulation layer.

  More specifically, in the multilayer wiring board of Patent Document 1, the resin insulating layer includes glass cloth in the resin insulating material. In the resin insulating layer, the glass cloth protrudes from the inner wall surface of the via hole formed through in the thickness direction, and the glass cloth bites into the side portion of the via conductor formed in the via hole. With this configuration, the via conductor is prevented from falling out of the via hole.

JP 2009-246358 A

  However, in the multilayer wiring board of Patent Document 1, the via hole is formed in an inverted truncated cone shape, and the diameter is increased from one opening to the other opening. Therefore, when this multilayer wiring board is warped and excessive stress is applied, especially when a via conductor is stressed from the opening portion having a small diameter toward the opening portion having a large diameter in the via hole, the via There is a concern that a problem of via missing such that the via conductor formed in the hole comes out of the via hole. For this reason, the multilayer wiring board which added the further improvement and improved connection reliability is desired.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a multilayer wiring board that can reliably prevent a via from being removed and has excellent connection reliability. Another object is to provide a method for manufacturing a multilayer wiring board suitable for manufacturing the multilayer wiring board.

  And as a means (means 1) for solving the above-mentioned problem, it has a build-up structure in which a plurality of resin insulation layers and a plurality of conductor layers are alternately laminated to form a multilayer, and at least one of the resin insulation layers One layer includes an inorganic fiber layer in the inner layer portion of the resin insulating material, a via hole is formed in the resin insulating material of the resin insulating layer, and a through hole is formed at a position corresponding to the via hole in the inorganic fiber layer, A multilayer wiring board in which via conductors that electrically connect the conductor layers are formed in the via holes and in the through holes, the portion serving as an opening edge of the through holes of the inorganic fiber layer is formed of the inorganic wiring board. The via hole protrudes inward from the inner wall surface of the via hole adjacent to the fiber layer, and the inner diameter of the via hole is largest in a region adjacent to the inorganic fiber layer of the inner wall surface of the via hole. Multilayer There is a line board.

  According to the invention described in the means 1, since the opening edge of the through hole of the inorganic fiber layer protrudes inward from the inner wall surface of the via hole, the protruding portion of the inorganic fiber layer can be bitten into the side portion of the via conductor. it can. For this reason, it is possible to prevent a via drop such that the via conductor formed in the via hole comes out of the via hole. Furthermore, the inner diameter of the via hole is the largest in the region adjacent to the inorganic fiber on the inner wall surface of the via hole. In this case, since the via hole has a shape in which the outer layer side opening and the inner layer side opening are narrowed, it is possible to reliably prevent the via from being lost and to improve the connection reliability of the multilayer wiring board.

  The resin insulating layer including the inorganic fiber layer may include a granular inorganic material in a weight ratio of 0% or more and less than 40%. Alternatively, the resin insulating layer may be formed without containing an inorganic material by setting the granular inorganic material to 0%. In this way, when laser processing of the via hole is performed, the energy absorption rate of the resin insulating layer is higher than that of the inorganic fiber layer, and the resin insulating layer near the through hole in the inorganic fiber layer is processed efficiently. As a result, it is possible to form the via hole so that the inner diameter becomes the largest in the region adjacent to the inorganic fiber layer.

  The average protrusion length of the inorganic fiber layer protruding inward from the inner wall surface of the via hole adjacent to the inorganic fiber layer may be 1/3 or less of the inner diameter of the via hole (the inner diameter of the maximum diameter portion). Further, the average inner diameter of the through holes may be 1/3 or more of the inner diameter of the maximum diameter portion in the via hole. If it does in this way, an inorganic fiber layer can be made to bite into a side part of a via conductor certainly, and a via omission can be prevented.

  The via conductor may be a filled via conductor formed by filling the via hole and the through hole. Further, the via conductor may be a conformal via conductor formed along the inner wall surface of the via hole and having a depression inside. Furthermore, a part of the resin insulating layer may be filled in the recess inside the conformal via conductor.

  The via hole has an outer layer side opening and an inner layer side opening, a first taper surface that gradually increases in diameter from the outer layer side opening toward the maximum diameter portion in the via hole, and a maximum diameter portion in the via hole. A second tapered surface that gradually decreases in diameter toward the inner layer side opening. In this case, the via hole and the via conductor have a substantially hexagonal cross section (cross section abacus ball shape), and the via can be reliably prevented from coming off. The via hole and via conductor may have a bowl-like shape having curved side surfaces, a plurality of inclined side surfaces having different angles, or a polygonal shape having stepped side surfaces.

  The resin insulating layer may have an inorganic fiber layer at a substantially central portion in the thickness direction. In this way, the inorganic fiber layer is not exposed from the surface of the resin insulating layer, and the inorganic fiber layer can be reliably contained in the inner layer portion of the resin insulating layer. Moreover, since the inorganic fiber layer protrudes from the substantially central portion on the inner wall surface of the via hole, it is possible to reliably prevent the via from coming off. Further, when the inorganic fiber layer is provided at the substantially central portion in the thickness direction of the resin insulating layer, the via hole and the via conductor having a substantially hexagonal cross section (cross section abacus shape) can be reliably formed.

  The size of the through hole formed in the inorganic fiber layer is not particularly limited as long as it is smaller than the via hole. For example, the average inner diameter of the through holes may be smaller than the outer layer side opening diameter and the inner layer side opening diameter of the via hole. If it does in this way, the opening edge of a through-hole can be made to bite into the side part of a via conductor reliably, and a via omission can be prevented reliably.

  The outer layer side opening diameter in the via hole may be larger than the inner layer side opening diameter. In this case, a via conductor can be reliably formed in the via hole through the outer layer side opening when plating.

  The resin insulating material constituting the resin insulating layer can be appropriately selected in consideration of insulation, heat resistance, moisture resistance, and the like. Preferable examples of the resin insulating material include thermosetting resins such as epoxy resins, phenol resins, urethane resins, silicone resins, and polyimide resins, and thermoplastic resins such as polycarbonate resins, acrylic resins, polyacetal resins, and polypropylene resins. .

  Further, as another means (means 2) for solving the above-described problem, the multilayer wiring board manufacturing method according to means 1, wherein the resin insulating material includes a glass cloth as the inorganic fiber layer. An insulating layer disposing step of disposing the resin insulating layer configured on the conductor layer; and applying a laser hole processing to the resin insulating material using a carbon dioxide laser to form the via hole in the resin insulating material. Forming and forming the through hole in the glass cloth, and conducting the processing heat at that time along the plane direction of the glass cloth to burn out the resin insulating material around the opening edge of the through hole. And a via hole forming step for forming the maximum diameter portion of the via hole, and a via conductor forming step for performing plating to form the via conductor in the via hole and the through hole. There is a method of manufacturing the plate.

  Therefore, according to the invention described in the means 2, the via hole forming step is performed after the resin insulating layer including the glass cloth is arranged on the conductor layer in the insulating layer arranging step. In this via hole forming step, laser hole processing using a carbon dioxide laser is performed on the resin insulating layer, whereby via holes are formed in the resin insulating material and through holes are formed in the glass cloth. At this time, the processing heat is conducted along the plane direction of the glass cloth. Since the energy absorption rate of the carbon dioxide laser is higher in the resin insulating material than in the glass cloth, the resin insulating material around the opening edge of the through hole is burned out by the processing heat conducted through the glass cloth. As a result, a maximum diameter portion is formed in a region adjacent to the glass cloth in the via hole. Thereafter, the via conductor is formed in the via hole and the through hole by plating in the via conductor forming step. In this way, it is possible to reliably prevent via disconnection, and it is possible to manufacture a multilayer wiring board having excellent connection reliability.

Sectional drawing which shows schematic structure of the multilayer wiring board in this Embodiment. The expanded sectional view which shows the via hole and via conductor in a resin insulating layer. Explanatory drawing which shows the core board | substrate formation process in the manufacturing method of a multilayer wiring board. Explanatory drawing which shows the insulating layer arrangement | positioning process in the manufacturing method of a multilayer wiring board. Explanatory drawing which shows the via hole formation process in the manufacturing method of a multilayer wiring board. Explanatory drawing which shows the via conductor formation process in the manufacturing method of a multilayer wiring board. Explanatory drawing which shows the buildup process in the manufacturing method of a multilayer wiring board. Explanatory drawing which shows the SEM photograph of the via hole and via conductor of this Embodiment. Sectional drawing which shows schematic structure of the multilayer wiring board in another embodiment.

  Hereinafter, an embodiment in which the present invention is embodied in a multilayer wiring board will be described in detail with reference to the drawings.

  As shown in FIG. 1, the multilayer wiring board 10 of the present embodiment includes a core substrate 11, a first buildup layer 31 formed on the core main surface 12 (upper surface in FIG. 1) of the core substrate 11, and The second buildup layer 32 is formed on the core back surface 13 (the lower surface in FIG. 1) of the core substrate 11.

  The core substrate 11 is made of, for example, a resin insulating material (glass epoxy material) obtained by impregnating a glass cloth as a reinforcing material with an epoxy resin. Through holes 15 (through holes) penetrating in the thickness direction are formed at a plurality of locations in the core substrate 11, and through hole conductors 16 are formed in the through hole 15. The through-hole conductor 16 connects the core main surface 12 side and the core back surface 13 side of the core substrate 11. The inside of the through-hole conductor 16 is filled with a closing body 17 such as an epoxy resin. Further, a conductor layer 41 made of copper is patterned on the core main surface 12 and the core back surface 13 of the core substrate 11, and each conductor layer 41 is electrically connected to the through-hole conductor 16.

  The first buildup layer 31 formed on the core main surface 12 of the core substrate 11 includes a plurality of resin insulating layers 33 and 35 mainly composed of a thermosetting resin (an epoxy resin as a resin insulating material), and copper. A plurality of conductor layers 42 are alternately stacked. Terminal pads 45 are formed in an array at a plurality of locations on the resin insulation layer 35. Further, the upper surface of the resin insulating layer 35 is almost entirely covered with a solder resist 37. An opening 46 for exposing the terminal pad 45 is formed at a predetermined portion of the solder resist 37. And the terminal pad 45 exposed from the opening part 46 is electrically connected to the connection terminal of a semiconductor chip via the solder bump which is not shown in figure. A via hole 43 and a via conductor 44 are formed in the resin insulating layer 33 and the resin insulating layer 35, respectively. Each via conductor 44 electrically connects the conductor layers 41 and 42 and the terminal pad 45 to each other.

  The second buildup layer 32 formed on the core back surface 13 of the core substrate 11 has substantially the same structure as the first buildup layer 31 described above. That is, the second buildup layer 32 is a buildup in which a plurality of resin insulation layers 34 and 36 mainly composed of a thermosetting resin (an epoxy resin as a resin insulation material) and a plurality of conductor layers 42 are alternately laminated. It has a structure. Via holes 43 and via conductors 44 are formed in the resin insulating layer 34 and the resin insulating layer 36, respectively. BGA pads 48 are formed in an array at a plurality of locations on the lower surface of the resin insulating layer 36. The lower surface of the resin insulating layer 36 is almost entirely covered with a solder resist 38. An opening 49 for exposing the BGA pad 48 is formed at a predetermined position of the solder resist 38. The BGA pad 48 exposed from the opening 49 is electrically connected to a mother board (external board) via a solder bump (not shown).

  Each of the resin insulating layers 33 to 36 of the present embodiment includes a glass cloth 51 as an inorganic fiber layer in the inner layer portion of the resin insulating material 50. More specifically, each of the resin insulating layers 33 to 36 is formed using a build-up material including only the glass cloth 51 without including a granular inorganic material such as silica filler. Each resin insulating layer 33 to 36 has a thickness of about 40 μm, and the glass cloth 51 has a thickness of about 15 μm. In each of the resin insulating layers 33 to 36, a glass cloth 51 is provided at a substantially central portion in the thickness direction.

  As shown in FIG. 2, a via hole 43 is formed in the resin insulating material 50 of the resin insulating layer 33, and a through hole 52 is formed at a position corresponding to the via hole 43 in the glass cloth 51. A via conductor 44 that electrically connects the conductor layers 41 and 42 is formed in the via hole 43 and the through hole 52. In the present embodiment, the via conductor 44 is a filled via conductor formed by filling the via hole 43 and the through hole 52, and the via hole 43 and the via conductor 44 have a substantially hexagonal cross section (a cross-section abacus shape). Is formed.

  In the glass cloth 51, the portion that becomes the opening edge of the through hole 52 protrudes inward from the inner wall surface of the via hole 43 adjacent to the glass cloth 51 and bites into the side portion of the via conductor 44. The inner diameter of the via hole 43 is largest in a region adjacent to the glass cloth 51 on the inner wall surface of the via hole 43. More specifically, the via hole 43 includes an outer layer side opening 54 and an inner layer side opening 55, and the first taper gradually increases in diameter from the outer layer side opening 54 toward the maximum diameter portion 56 in the via hole 43. It has a surface 57. The via hole 43 has a second tapered surface 58 that gradually decreases in diameter from the maximum diameter portion 56 toward the inner layer side opening 55.

  In the present embodiment, the average inner diameter of the through holes 52 formed in the glass cloth 51 is smaller than the diameters of the outer layer side opening 54 and the inner layer side opening 55 in the via hole 43. Furthermore, the diameter of the outer layer side opening 54 in the via hole 43 is larger than the diameter of the inner layer side opening 55. Specifically, the average inner diameter of the through holes 52 is about 30 μm, and the diameter of the maximum diameter portion 56 is about 70 μm. The outer layer side opening 54 has a diameter of about 50 μm, and the inner layer side opening 55 has a diameter of about 40 μm.

  In the present embodiment, the average protruding length of the glass cloth 51 protruding inward from the inner wall surface of the via hole 43 is 1/3 or less of the inner diameter of the via hole 43 (the inner diameter of the maximum diameter portion 56). That is, the average inner diameter of the through holes 52 in the glass cloth 51 is not less than 1/3 of the inner diameter of the maximum diameter portion 56 in the via hole 43, and the glass cloth 51 surely bites into the side portion of the via conductor 44. .

  Next, a method for manufacturing the multilayer wiring board 10 of the present embodiment will be described.

  First, a copper clad laminate in which a copper foil is pasted on both sides of a substrate made of glass epoxy is prepared. And drilling is performed using a drill machine, and the through-hole 15 which penetrates the front and back of a copper clad laminated board is previously formed in the predetermined position. And the through-hole conductor 16 is formed in the through-hole 15 by performing the electroless copper plating and the electrolytic copper plating with respect to the inner surface of the through-hole 15 of a copper clad laminated board.

  Thereafter, the cavity of the through-hole conductor 16 is filled with an insulating resin material (epoxy resin) to form the closing body 17. Furthermore, the copper foil of the copper clad laminate and the copper plating layer formed on the copper foil are patterned by, for example, a subtractive method. As a result, as shown in FIG. 3, the core substrate 11 on which the through-hole conductor 16 and the conductor layer 41 are formed is obtained.

  Then, by performing a build-up process, the first build-up layer 31 is formed on the core main surface 12 of the core substrate 11, and the second build-up layer 32 is also formed on the core back surface 13 of the core substrate 11. Form.

  Specifically, as shown in FIG. 4, the resin insulating material 50 includes a glass cloth 51 on the core main surface 12 and the core back surface 13 on which the respective conductor layers 41 are formed in the core substrate 11. The sheet-like resin insulating layers 33 and 34 are arranged, and the resin insulating layers 33 and 34 are attached (insulating layer arranging step).

Thereafter, laser hole machining is performed using a carbon dioxide laser (CO ₂ laser) to form via holes 43 at predetermined positions of the resin insulating layers 33 and 34 and to form through holes 52 in the glass cloth 51 (via holes). Forming step). Here, the energy absorption rate of the carbon dioxide laser is higher in the resin insulating material 50 than in the glass cloth 51. For this reason, the processing heat applied when forming the through holes 52 in the glass cloth 51 conducts the glass cloth 51 in the plane direction, so that the resin insulating material 50 around the opening edge of the through holes 52 is burned out. As a result, as shown in FIG. 5, in the via hole 43, the maximum diameter portion 56 is formed in the region adjacent to the glass cloth 51, and the first tapered surface 57 and the second tapered surface 58 are formed. . Further, since the laser is irradiated and processed from the outer layer side opening 54 side, the diameter D1 (outer layer side opening diameter) of the outer layer side opening 54 in the via hole 43 is equal to the diameter D2 (inner layer side) of the inner layer side opening 55. (Opening diameter).

Next, a desmear process for removing smear in each via hole 43 is performed using an etching solution such as a potassium permanganate solution. As the desmear process, in addition to treatment with an etchant, for example it may perform processing of plasma ashing using O ₂ plasma.

  After the desmear process, via conductors 44 are formed in each via hole 43 by performing electroless copper plating and electrolytic copper plating according to a conventionally known method (via conductor formation process). Further, the conductor layer 42 is patterned on the resin insulating layers 33 and 34 by performing etching by a conventionally known method (for example, a semi-additive method) (see FIG. 6).

  The other resin insulation layers 35 and 36 and the conductor layer 42 are also formed by the same method as the resin insulation layers 33 and 34 and the conductor layer 42 described above, and are laminated on the resin insulation layers 33 and 34. Here, a plurality of terminal pads 45 are formed as the conductor layer 42 on the resin insulating layer 35, and a plurality of BGA pads 48 are formed as the conductor layer 42 on the resin insulating layer 36 (see FIG. 7). .

  Next, solder resists 37 and 38 are formed by applying and curing a photosensitive epoxy resin on the resin insulating layers 35 and 36. Thereafter, exposure and development are performed with a predetermined mask placed, and the openings 46 and 49 are patterned in the solder resists 37 and 38. The multilayer wiring board 10 shown in FIG. 1 is manufactured through the above steps.

  The inventor cut the multilayer wiring board 10 manufactured by the above method in the thickness direction on the axis of the via conductor 44 and observed the cut surface of the via conductor 44 with an electron microscope (SEM). FIG. 8 shows an SEM photograph 60 of the cut surface of the via conductor 44. As shown in FIG. 8, in the via hole 43 having a substantially hexagonal cross section, the glass cloth 51 protrudes and bites into the side of the via conductor 44, and the inner diameter of the via hole 43 is the inner wall surface of the via hole 43. In FIG. 4, the depth is the largest at the depth position where the glass cloth 51 exists. Furthermore, it was confirmed that the via conductors 44 were formed without gaps in the via holes 43 having a substantially hexagonal cross section, and the adhesion of the via conductors 44 was sufficiently ensured.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the multilayer wiring board 10 of the present embodiment, the resin insulating layers 33 to 36 include the glass cloth 51 in the inner layer portion, and the opening edge of the through hole 52 of the glass cloth 51 protrudes from the inner wall surface of the via hole 43. At the same time, it bites into the side of the via conductor 44. For this reason, it is possible to prevent a via drop such that the via conductor 44 formed in the via hole 43 comes out of the via hole 43. Further, the inner diameter of the via hole 43 is the largest in the region adjacent to the glass cloth 51 on the inner wall surface of the via hole 43. In this case, since the via hole 43 has a shape in which the outer layer side opening 54 and the inner layer side opening 55 are narrowed, it is possible to reliably prevent the via from coming off.

  (2) In the multilayer wiring board 10 of the present embodiment, the energy absorption rate of the carbon dioxide laser is higher in the resin insulating material 50 than in the glass cloth 51. For this reason, at the time of laser hole machining, the resin insulating material 50 around the opening edge of the through hole 52 is burned out by the processing heat conducted in the plane direction of the glass cloth 51. As a result, the maximum diameter portion 56 can be reliably formed in a region adjacent to the glass cloth 51 in the via hole 43.

  (3) In the multilayer wiring board 10 of the present embodiment, the average protrusion length of the glass cloth 51 protruding from the inner wall surface of the via hole 43 is 1/3 or less of the inner diameter of the via hole 43. In this way, the glass cloth 51 can be surely bited into the side portion of the via conductor 44, and the via omission can be prevented.

  (4) In the multilayer wiring board 10 of the present embodiment, the average inner diameter of the through holes 52 formed in the glass cloth 51 is smaller than the outer layer side opening diameter D1 and the inner layer side opening diameter D2 in the via hole 43. In this case, the opening edge of the through hole 52 can be surely bited into the side portion of the via conductor 44. Further, the outer layer side opening diameter D1 in the via hole 43 is larger than the inner layer side opening diameter D2. By increasing the outer layer side opening diameter D1 in this manner, the filled via conductor 44 can be reliably formed in the via hole 43 through the outer layer side opening 54 when performing plating.

  (5) In the multilayer wiring board 10 of the present embodiment, the resin insulating layers 33 to 36 have a glass cloth 51 at a substantially central portion in the thickness direction. In this case, the glass cloth 51 can be reliably contained in the resin insulating layers 33 to 36 without exposing the glass cloth 51 from the surfaces of the resin insulating layers 33 to 36. Further, since the glass cloth 51 protrudes from the central portion of the inner wall surface of the via hole 43, it is possible to reliably prevent the via from coming off. Furthermore, in the resin insulating layers 33 to 36, since the glass cloth 51 is provided at the substantially central portion in the thickness direction, the via holes 43 and the via conductors 44 having a substantially hexagonal cross section (cross section abacus ball shape) can be reliably formed. it can. Moreover, the intensity | strength of the resin insulation layers 33-36 is fully securable by including the glass cloth 51. FIG.

  In addition, you may change embodiment of this invention as follows.

  In the multilayer wiring board 10 of the above-described embodiment, the via holes 43 and the via conductors 44 having the same shape having a substantially hexagonal cross section are formed in all the resin insulating layers 33 to 36. The via hole 43 and the via conductor 44 may be formed in at least one of the resin insulating layers 33 to 36. FIG. 9 shows a specific example of the multilayer wiring board 10A. In the multilayer wiring board 10A of FIG. 9, the resin insulating layers 33 and 34 on the core substrate 11 side are insulating layers including the glass cloth 51 as in the above embodiment. Further, the resin insulation layers 35A and 36A on the outer layer side of the resin insulation layers 33 and 34 are resin insulation layers configured without including the glass cloth 51. In the multilayer wiring board 10A, via holes 43 and via conductors 44 having a substantially hexagonal cross section are formed in the resin insulating layers 33 and 34 on the core substrate 11 side. On the other hand, via holes 43A and via conductors 44A having a diameter expanded from the inner layer side toward the outer layer side are formed in the resin insulating layers 35A and 36A on the outer layer side. In this case, laser hole processing is performed by appropriately adjusting the laser irradiation conditions depending on the presence or absence of the glass cloth 51 included in the resin insulating layers 33, 34, 35A, and 36A. Even if manufactured in this way, it is possible to prevent the via conductor 44 from coming off in the multilayer wiring board 10A, and to improve connection reliability.

  In the multilayer wiring board 10 of the above embodiment, the via conductor 44 is a filled via conductor that completely fills the via hole 43 and the through hole 52. However, the present invention is not limited to this. A conformal via conductor may be formed in the through hole 52. In this case, a via conductor having a uniform thickness is formed along the shape of the via hole 43 and the through hole 52, and a recess formed inside the via conductor is filled with a part of the upper resin insulating layer. .

  -In the multilayer wiring board 10 of the said embodiment, although each resin insulating layer 33-36 was formed using the buildup material which contains only the glass cloth 51, without including granular inorganic materials, such as a silica filler. However, the present invention is not limited to this. In addition to the glass cloth 51, the resin insulating layers 33 to 36 may be formed using a build-up material containing a silica filler in a proportion of 20% by weight or less. In this case, the processability of each of the resin insulating layers 33 to 36 is slightly deteriorated by including a silica filler. For this reason, although the inclination of the tapered surfaces 57 and 58 of the via hole 43 is gentle, the inner wall surface of the via hole 43 can be formed to be the largest in the region adjacent to the glass cloth 51.

  In the above embodiment, the present invention is embodied in the multilayer wiring substrate 10 having the core substrate 11. However, the present invention may be embodied in a coreless wiring substrate not having the core substrate 11.

  The form of the multilayer wiring board 10 in the above embodiment is not limited to BGA (ball grid array), but the present invention is applied to a wiring board such as PGA (pin grid array) or LGA (land grid array). May be.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above are listed below.

  (1) The multilayer wiring board according to means 1, wherein the resin insulating layer is formed without containing a granular inorganic material.

  (2) The multilayer wiring board according to (1), wherein the resin insulating layer has the inorganic fiber layer at a substantially central portion in the thickness direction.

  (3) The multilayer wiring board according to means 1, wherein the resin insulating layer has a thickness of 50 μm or less.

  (4) The multilayer wiring board according to (1), wherein an average inner diameter of the through holes is 1/3 or more of an inner diameter of a maximum diameter portion in the via hole.

  (5) The multilayer wiring board according to (1), wherein an average inner diameter of the through holes is smaller than an outer layer side opening diameter and an inner layer side opening diameter in the via hole.

  (6) The multilayer wiring board according to means 1, wherein an outer layer side opening diameter of the via hole is larger than an inner layer side opening diameter.

  (7) The multilayer wiring board according to means 1, wherein the via hole has a substantially hexagonal cross section.

  (8) The multilayer wiring board according to means 1, wherein the via hole has a abacus cross section.

DESCRIPTION OF SYMBOLS 10,10A ... Multilayer wiring board 33-36 ... Resin insulation layer 42 ... Conductor layer 43 ... Via hole 44 ... Via conductor 50 ... Resin insulation material 51 ... Glass cloth as an inorganic fiber layer 52 ... Through-hole 54 ... Outer layer side opening 55 ... Inner layer side opening 56 ... Maximum diameter portion 57 ... First taper surface 58 ... Second taper surface

Claims (6)

It has a build-up structure in which a plurality of resin insulation layers and a plurality of conductor layers are alternately laminated to form a multilayer, and at least one of the resin insulation layers includes an inorganic fiber layer in the inner layer portion of the resin insulation material, Via holes are formed in the resin insulating material of the resin insulating layer, and through holes are formed at positions corresponding to the via holes in the inorganic fiber layer, and the conductor layers are electrically connected in the via holes and the through holes. A multilayer wiring board in which via conductors to be connected are formed,
The portion that becomes the opening edge of the through hole of the inorganic fiber layer protrudes inward from the inner wall surface of the via hole adjacent to the inorganic fiber layer, and
An inner diameter of the via hole is the largest in a region adjacent to the inorganic fiber layer on the inner wall surface of the via hole.   2. The multilayer wiring board according to claim 1, wherein the resin insulating layer including the inorganic fiber layer includes a granular inorganic material in a weight ratio of 0% to less than 40%.   The average protruding length of the inorganic fiber layer protruding inward from the inner wall surface of the via hole adjacent to the inorganic fiber layer is 1/3 or less of the inner diameter of the via hole. 2. The multilayer wiring board according to 2.   4. The multilayer wiring board according to claim 1, wherein the via conductor is a filled via conductor formed by filling the via hole and the through hole. 5.   The via hole has an outer layer side opening and an inner layer side opening, a first tapered surface that gradually increases in diameter from the outer layer side opening toward the maximum diameter portion of the via hole, and the via hole 5. The multilayer wiring board according to claim 1, further comprising: a second tapered surface having a gradually decreasing diameter from the maximum diameter portion toward the inner layer side opening. A method for manufacturing a multilayer wiring board according to any one of claims 1 to 5,
An insulating layer disposing step of disposing on the conductor layer the resin insulating layer configured to include glass cloth as the inorganic fiber layer in the resin insulating material;
The resin insulating layer is subjected to laser hole processing using a carbon dioxide laser to form the via hole in the resin insulating material and the through hole in the glass cloth. A via hole forming step of forming the maximum diameter portion of the via hole by conducting along the plane direction of the cloth and burning out the resin insulating material around the opening edge of the through hole;
And a via conductor forming step of forming the via conductor in the via hole and in the through hole by performing plating.