JP2018170486A - Method for manufacturing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cracks from being generated in an insulating resin layer in through hole processing of the insulating resin layer by a drill.SOLUTION: A method includes the steps of: preparing at least one laminated board 1 in which a metal 12 is adhered to at least one surface of an insulating resin layer 11 not including an insulating cloth material; forming an inner layer land forming member 21 on a surface located at least at an upstream side in a penetration direction of a through hole 5 on a surface out of surfaces of the insulating resin layer 11 in a printed wiring board 100 on which the through hole 5 is formed; sandwiching the laminated board 1 by an insulating layer 3; forming the through hole 5 so as to penetrate the inner layer land forming member 21 adhered to the insulating resin layer 11; and forming an inner layer land 2 on a peripheral edge portion of the through hole 5.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a method for manufacturing a printed wiring board.

  Conventionally, a printed wiring having a multilayer structure including a laminated board in which a conductive layer such as a metal foil is formed on at least one surface of an insulating resin layer including an insulating cloth material such as glass cloth as a reinforcing material, and the insulating layer and the conductive layer A plate is used (see Patent Document 1).

JP 2003-204010 A

  A method for manufacturing a printed wiring board according to the present disclosure includes: a laminate having at least one laminate in which a metal is deposited on at least one surface of an insulating resin layer not including an insulating cloth material; The inner land land-forming member is formed on at least the upstream surface of the insulating resin layer in the through direction of the through hole, and the laminated plate is sandwiched between the insulating layers and adhered to the insulating resin layer. A through-hole is formed so as to penetrate the inner-layer land forming member, and an inner-layer land is formed at the peripheral portion of the through-hole.

  A printed wiring board according to the present disclosure includes at least one laminated board in which a metal is deposited on at least one surface of an insulating resin layer that does not include an insulating cloth material, an insulating layer that sandwiches the laminated board, A laminated plate including at least one through-hole and having a through-hole formed on the surface of the insulating resin layer at least on the upstream side in the through-direction of the through-hole. Are provided with inner lands, and a gap is formed at the peripheral edge of the inner lands.

It is explanatory drawing which shows one Embodiment of the printed wiring board which concerns on this indication. (A)-(d) is process explanatory drawing which shows one Embodiment of the manufacturing method of the printed wiring board which concerns on this indication. It is a graph which shows the transmission loss of the inner-layer land of the printed wiring board shown in FIG.

  An insulating cloth material such as glass cloth is included in the insulating resin layer as a reinforcing material. For this reason, a laminated board that does not contain the insulating cloth material in the insulating resin layer has a lower strength (becomes brittle) than the laminated board that contains the insulating cloth material. Therefore, when manufacturing a printed wiring board including such an insulating resin layer, for example, when subjected to drilling, a crack may occur in the insulating resin layer due to impact or vibration during processing. Furthermore, a propagation crack is induced from such a crack. As a result, the insulation reliability of the insulating resin layer is impaired by the propagation crack.

  In the method for manufacturing a printed wiring board according to the present disclosure, in the laminated board in which the through hole is formed, among the surfaces of the insulating resin layer not including the insulating cloth material, at least the surface positioned on the upstream side in the through direction of the through hole In all of these, the inner layer land forming member is attached to the inner layer wiring regardless of the presence or absence of electrical connection. As a result, when the through hole is formed, for example, by drilling or the like, the insulating resin layer can be protected from impact and vibration, and the occurrence of cracks can be prevented. Therefore, since propagation cracks starting from such cracks can be prevented, the insulation reliability of the insulating resin layer is not deteriorated. Furthermore, since the insulating resin layer of the laminate does not include an insulating cloth material, the thickness of the laminate can be reduced as compared with the case where an insulating resin layer including an insulating cloth material is used.

  A method for manufacturing a printed wiring board according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. A printed wiring board 100 shown in FIG. 1 is a printed wiring board obtained by a manufacturing method according to an embodiment of the present disclosure, and includes a laminated board 1, an inner layer land 2, an insulating layer 3, and a conductor 4.

  The laminated board 1 will not be specifically limited if it is a laminated board with which the metal adhered to the at least one surface of the insulating resin layer which does not contain an insulating cloth material. Examples of such a laminated plate include those obtained by depositing a metal foil on at least one surface of the insulating resin layer, and those obtained by depositing metal on at least one surface of the insulating resin layer by plating. The laminate 1 shown in FIGS. 1 and 2 will be described by taking as an example a metal-clad laminate in which a metal foil 12 is attached to both surfaces of an insulating resin layer 11 that does not contain an insulating cloth material.

  The insulating resin layer 11 included in the metal-clad laminate 1 is not particularly limited as long as it is formed of an insulating material (insulating plate). Examples of such insulating materials include epoxy resins, bismaleimide-triazine resins, polyimide resins, polyphenylene ether (PPE) resins, phenol resins, polytetrafluoroethylene (PTFE) resins, silicon resins, polybutadiene resins, Examples thereof include organic resins such as polyester resins, melamine resins, urea resins, polyphenylene sulfide (PPS) resins, and polyphenylene oxide (PPO) resins. These organic resins may be used in combination of two or more. Furthermore, the insulating resin layer 11 may contain inorganic fillers (fillers) such as silica, barium sulfate, talc, clay, calcium carbonate, and titanium oxide.

  This insulating resin layer 11 does not contain an insulating cloth material (for example, glass fiber, glass nonwoven fabric, aramid nonwoven fabric, aramid fiber, polyester fiber, etc.) as a reinforcing material. Therefore, the breaking strain of the insulating resin layer 11 is usually 2% or less and may be 1 to 2%.

  The laminated plate 1 has a structure in which metal foils 12 are attached to both the upper and lower surfaces of an insulating resin layer 11. In FIGS. 1 and 2, the laminated plate 1 uses a double-sided copper-clad laminated plate with a metal foil 12 stuck on both sides, but a laminated plate with a metal foil stuck only on one side may be used. Examples of the metal foil 12 include a copper foil. The insulating resin layer 11 has a thickness of about 5 to 25 μm, for example. As a double-sided copper-clad laminate in which an insulating resin layer is not included in the insulating resin layer, for example, “FARADFLEX MC24M” manufactured by Mitsui Mining & Smelting Co., Ltd. is commercially available.

  An insulating layer 3 is formed on the upper and lower surfaces of the laminated plate 1. That is, the laminated plate 1 is sandwiched between the insulating layers 3. The resin forming the insulating layer 3 is not particularly limited, and examples thereof include the resin forming the insulating resin layer 11 described above. The resin forming the insulating layer 3 and the resin forming the insulating resin layer 11 may be the same or different. Furthermore, unlike the insulating resin layer 11, the insulating layer 3 should contain an insulating cloth material.

  A conductor 4 is formed inside or on the surface of the insulating layer 3. The conductor 4 is electrically connected to a component to be mounted, another substrate, or the like. The conductor 4 is not particularly limited as long as it is formed of a conductive material. Examples of such a material include copper. For such a conductor 4, for example, a layer formed of a conductive material such as copper previously formed on the surface of the insulating layer 3 is exposed and developed by a known method, and a part of the conductive material is etched. And a method of forming by pattern plating.

  In the printed wiring board 100 shown in FIG. 1, a through hole (through hole) 5 that penetrates from the upper surface to the lower surface of the printed wiring board 100 is formed. A conductor is attached to the inner wall surface of the through hole 5, and the upper and lower surfaces of the printed wiring board 100 are electrically connected. The outer diameter X of the through hole 5 is not particularly limited, and is about 300 to 1000 μm, for example. A metal foil (copper foil) may be provided on the surface of the printed wiring board 100 other than the opening of the through hole 5.

  An inner land 2 is formed at the peripheral edge of the through hole 5. Specifically, the inner land 2 is formed on the upper and lower surfaces of the insulating resin layer 11 at a portion where the through hole 5 and the insulating resin layer 11 of the laminated plate 1 intersect. This inner layer land 2 may be a dummy land that is not electrically connected to the inner layer wiring (metal foil 12 and conductor 4) formed on the printed wiring board 100.

The diameter Y of the inner land 2 is not particularly limited, and for example, it is preferable to satisfy the formula (I), and particularly to satisfy the formula (II).
Outer diameter of through hole <Inner layer land diameter ≦ Outer diameter of through hole + 0.2 mm (I)
Through hole outer diameter + 0.1 mm ≤ inner land land diameter ≤ through hole outer diameter + 0.2 mm (II)

  A gap 7 is formed between the inner layer land 2 formed on the same plane of the insulating resin layer 11 and the inner layer wiring (solid portion of the metal foil 12). That is, the gap 7 is formed at the peripheral edge of the inner land 2. The gap 7 is preferably formed substantially concentrically with the through hole 5.

  Such a printed wiring board 100 shown in FIG. 1 is obtained by the following method, for example. One embodiment of a method for manufacturing a printed wiring board according to the present disclosure will be described with reference to FIGS. This manufacturing method includes the following steps (i) to (iv). The same members as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

(I) At least one laminated board in which a metal is deposited on at least one surface of an insulating resin layer not including an insulating cloth material is prepared.
(Ii) In the laminated board in which the through hole is formed, the inner layer land forming member is formed on the surface of the insulating resin layer at least on the upstream side in the through direction of the through hole.
(Iii) The laminate is sandwiched between insulating layers.
(Iv) A through hole is formed so as to penetrate the inner layer land forming member attached to the insulating resin layer, and an inner layer land is formed at the peripheral edge of the through hole.

  First, as shown in FIG. 2A, a double-sided metal-clad laminate (laminate 1) in which metal foils 12 (for example, copper foils) are attached to both sides of an insulating resin layer 11 is prepared. A circuit pattern is formed on at least one main surface of the laminate 1 by a known method such as a subtractive method.

  Next, as shown in FIG. 2B, an inner land land forming member 21 is formed on the laminated plate 1. The inner layer land forming member 21 is formed at a position where the through hole 5 is formed. Inner layer land forming member 21 may be formed of metal foil 12 affixed to laminate 1, and after removing metal foil 12, a metal such as copper may be formed by plating. The diameter Y of the inner layer land forming member 21 is the same as the diameter Y of the inner layer land 2 described above. In the metal (metal foil 12) formed on the same plane of the insulating resin layer 11, a gap 7 is formed between the inner land formation member 21 and the inner wiring (solid portion of the metal foil 12). . The diameter of the gap 7 (clearance diameter Z) is preferably not less than 2 times and not more than 4 times the inner layer land forming member 21 (the diameter Y of the inner layer land forming member).

  After the inner layer land forming member 21 is formed on the laminate 1, the laminate 1 is sandwiched between the insulating layers 3. The insulating layer 3 is as described above, and detailed description thereof is omitted. If necessary, a laminate (second laminate 6) different from the laminate 1 in which the conductor 4 is formed on at least one surface of the insulating layer 3 is prepared.

  When the desired printed wiring board 100 has a multilayer structure, as shown in FIG. 2C, the laminated plates 1, the insulating layers 3, and the second laminated plates 6 are alternately stacked. In this case, in the second laminated plate 6, when there is no electrical connection to the inner layer wiring, the conductor 4 is not formed at the location where the inner layer land forming member 21 is formed, and the position of the inner layer land forming member 21 of the laminated plate 1 is determined. Are stacked so that they do not shift laterally. Then, the laminated board 1, the insulating layer 3, and the 2nd laminated board 6 are thermocompression-bonded by hot press. Next, when the through hole 5 is formed on the inner land formation member 21 from the direction indicated by the arrow D using, for example, a drill, a printed wiring board 100 as shown in FIG. 2D is obtained. The diameter of the drill is not particularly limited, and may be appropriately selected according to the desired outer diameter of the through hole.

  In an embodiment of the method for manufacturing a printed wiring board according to the present disclosure, the inner layer land forming member 21 is formed at a position where the through hole 5 is formed. This inner layer land forming member 21 is formed of a metal (for example, copper (breaking strain: 20% or more)) having a larger breaking strain than that of the insulating resin layer. Therefore, the inner layer land forming member 21 protects the insulating resin layer 11 from impact during drill entry when forming the through hole 5 and vibration during drilling, and prevents the insulating resin layer 11 from cracking. be able to. Therefore, since it is possible to prevent the occurrence of propagation cracks starting from such cracks, the insulating reliability of the insulating resin layer 11 is hardly impaired in the printed wiring board 100. By forming the through-hole 5 at the position of the inner-layer land forming member 21, the inner-layer land 2 is formed at the peripheral portion of the through-hole 5 in the printed wiring board 100 as shown in FIG.

  Although the printed wiring board structure according to the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and various modifications or improvements can be made within the scope of the claims. . For example, the printed wiring board 100 shown in FIGS. 1 and 2 uses a double-sided metal-clad laminate. However, a metal-clad laminate in which a metal foil is stuck only on one side of the insulating resin layer may be used.

  In the printed wiring board 100 shown in FIGS. 1 and 2, the inner land 2 is formed on the upper and lower surfaces of the insulating resin layer 11 at a portion where the through hole 5 and the insulating resin layer 11 of the laminated board 1 intersect. That is, the inner layer land forming members 21 are formed on the upper and lower surfaces of the insulating resin layer 11. However, the inner layer land forming member may be formed only on the upstream side in the through-hole penetration direction, that is, on the upper surface side of the insulating resin layer 11 in FIGS. Inner layer land forming members are formed on the upper and lower surfaces of the insulating resin layer in that the insulating resin layer can be further protected from impact during drill entry when forming a through hole and vibration during drilling. Good.

  In the printed wiring board 100 shown in FIGS. 1 and 2, a through hole 5 penetrating the upper and lower surfaces of the printed wiring board 100 is formed. However, in the manufacturing method according to an embodiment of the present disclosure, for example, an embodiment in which a through hole penetrating at least one laminated plate 1 among the plurality of laminated plates 1 may be formed. In this case, the inner layer land forming member is formed on the insulating resin layer included in the laminated plate forming the through hole.

  In the printed wiring board 100 shown in FIGS. 1 and 2, the solder resist layer is not formed on both surfaces of the printed wiring board. However, in the manufacturing method according to an embodiment of the present disclosure, solder resist layers may be formed on both surfaces of the printed wiring board.

  By providing the gap 7 at the periphery of the inner land 2, a decrease in impedance of the inner land 2 can be suppressed, and the influence on the electrical characteristics can be reduced. If the impedance of the inner land 2 is at least about 50Ω, the influence on the electrical characteristics can be reduced. For example, it may be 50 to 100Ω.

  Since the impedance of the inner layer land 2 satisfies the above range, the diameter of the gap 7 (clearance diameter Z) is preferably not less than 2 times and not more than 4 times the diameter of the inner layer land 2 (inner layer land diameter Y). .

FIG. 3 is a graph showing the transmission loss of the through hole 5 formed in the printed wiring board 100, where the X axis represents the frequency and the Y axis represents the transmission loss. The transmission characteristic (Zdiff) of the inner land 2 can be determined by 2 × Z ₀ × (1−0.374 × exp (−2.9 × S / h)).
(Zdiff: differential impedance, Z ₀ : characteristic impedance, S: width of the gap 7 (distance between the inner land 2 and the solid portion of the metal foil 12), h: clearance diameter Z (long if the clearance is not a circle) Diameter)))

In the through hole A1 shown in FIG. 3 (φ350 μm inner land and φ1250 μm gap), the gap diameter (clearance diameter) is 3.57 times the inner land diameter and the impedance (Zdiff) is 79Ω. . As shown in FIG. 3, this A1 prevents a reduction in transmission characteristics.
On the other hand, in the through-hole of B1 (φ350 μm inner layer land and φ660 μm gap), the clearance diameter is 1.88 times the inner layer land diameter, and the impedance (Zdiff) is 46Ω. As shown in FIG. 3, B1 is within the allowable range, but the transmission characteristics are deteriorated as compared with A1.

  From FIG. 3, the quality of the signal flowing through the through hole 5 is further prevented by setting the diameter of the gap 7 (clearance diameter Z) to be 2 to 4 times the diameter of the inner land 2 (inner land diameter Y). I understand that I can do it.

1 Laminate (metal-clad laminate)
DESCRIPTION OF SYMBOLS 11 Insulating resin layer 12 Metal foil 2 Inner layer land 21 Inner layer land formation member 3 Insulating layer 4 Conductor 5 Through hole (through hole)
6 Second laminated board 7 Gap 100 Printed wiring board X Through hole outer diameter (outer diameter of through hole)
Y Inner layer land diameter (Inner layer land forming member diameter)
Z clearance diameter (diameter of gap)

Claims (7)

Preparing at least one laminate having a metal deposited on at least one surface of an insulating resin layer not including an insulating cloth material;
In the laminated plate in which the through hole is formed, an inner layer land forming member is formed on the surface of the insulating resin layer at least on the upstream side in the through direction of the through hole,
Sandwich the laminate with an insulating layer,
A through hole is formed so as to penetrate the inner layer land forming member attached to the insulating resin layer, and an inner layer land is formed at the peripheral edge of the through hole.
A method for producing a printed wiring board, comprising:   The manufacturing method according to claim 1, wherein the laminate is a metal-clad laminate in which a metal foil is attached to at least one surface of the insulating resin layer.   The manufacturing method according to claim 1, wherein the inner layer lands are provided on both surfaces of the insulating resin layer. The manufacturing method according to any one of claims 1 to 3, wherein the inner land has a diameter satisfying the following formula (I).
Outer diameter of through hole <Inner layer land diameter ≦ Outer diameter of through hole + 0.2 mm (I)   The manufacturing method according to claim 1, wherein the breaking strain of the insulating resin layer is 2% or less. At least one laminate having a metal deposited on at least one surface of an insulating resin layer not including an insulating cloth material; and
An insulating layer sandwiching the laminate,
A through hole penetrating at least one of the laminates;
Including
In the laminated plate in which the through hole is formed, an inner layer land is provided at a peripheral portion of the through hole on at least an upstream surface of the insulating resin layer in the through direction of the through hole, and the peripheral portion of the inner layer land A printed wiring board characterized in that a gap is formed in the printed wiring board.   The printed wiring board according to claim 6, wherein a diameter of the gap is not less than 2 times and not more than 4 times the diameter of the inner land.

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