JP4195619B2 - Multilayer wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer wiring board and a method for manufacturing the same, and more particularly to a multilayer flexible printed wiring board.
[0002]
[Prior art]
In recent years, electronic devices have become smaller and lighter in addition to high-frequency signals, digitization, and the like, and accordingly, printed wiring boards to be mounted are also required to be small and have high-density mounting. As a printed wiring board that meets these requirements, there is a rigid flex printed wiring board including a rigid portion and a flex portion (Patent Document 1).
[0003]
A typical manufacturing process of the rigid flex printed wiring board will be described with reference to FIGS.
[0004]
As shown in FIG. 13 (a), wiring circuits 104 are formed on the both surfaces of the flex substrate 101 made of polyimide film or the like, on both sides of the inner rigid substrate 102 made of prepreg, etc. Form.
[0005]
Next, a flex portion exposure hole 109 is provided in the adhesive sheet 105, the inner layer rigid substrate 102, and the outer layer rigid substrate 103 by press punching or the like. Then, the flex substrate cover layer 106, the inner layer rigid substrate 102, the adhesive sheet 105, and the outer layer rigid substrate 103 are arranged so as to overlap the front and back of the flex substrate 101, and the laminate shown in FIG. Get 100.
[0006]
Next, drilling, plating, etching, etc. are performed on the laminated body 100 to form the through hole 107, the outer layer wiring circuit 108, etc., and finally, the outer shape of the rigid part B and the flex part A are simultaneously removed. A rigid flex printed wiring board 110 as shown in FIG. 13C is obtained.
[0007]
In addition, a structure in which a buildup layer is provided on the surface layer of a rigid flex printed wiring board and interlayer connection is made by IVH (interstitial via hole) or SVH (surface via hole) has been announced.
[0008]
[Patent Literature]
Japanese Patent Laid-Open No. 2002-158445
[Problems to be solved by the invention]
However, in the case of such a rigid flex printed wiring board, after the rigid portions are stacked, the outer shape of the rigid portion and the flex portion is removed at the same time, so the shape (region) of the rigid portion is on the flex substrate and its front and back sides. This is the same as the multilayer part including the laminated inner layer rigid substrate and outer layer rigid substrate.
[0010]
For this reason, an extra multi-layered region may be present in the rigid portion, resulting in a waste of material cost. In addition, there is a restriction on the position of the multilayer region, and the degree of freedom of wiring is impaired. Nonetheless, the rigid flex printed wiring board is the best connection technology between the multilayered part (rigid part) for mounting electronic components and the flex board in terms of freedom of wiring and board area. is there.
[0011]
The present invention has been made to solve the above-described problems, and provides a multilayer wiring board capable of obtaining a higher degree of wiring freedom, achieving a reduction in material cost and a reduction in substrate capacity, and a method for manufacturing the same. It is intended to provide.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, in the multilayer wiring board according to the present invention, at least one base material with a wiring circuit that has been subjected to outline processing is bonded to a mother board printed wiring board, and at least one substrate is provided. It is electrically connected by an inner via hole.
[0013]
Accordingly, it is not necessary to match the outer shape of the substrate with a wiring circuit with the outer shape of the motherboard printed wiring board, and the outer shape of the substrate with a wiring circuit can be set smaller than the outer shape of the motherboard printed wiring board. However, it is possible to make an island-like structure where the necessary parts are selected on the motherboard printed wiring board.
[0014]
In addition, a plurality of substrates with wiring circuits that have undergone outer shape processing can be stacked, and a necessary region can be selected on a mother board printed wiring board so that a minimum necessary region can be multilayered. The base material with a wiring circuit that has been subjected to external processing may be a base material with a single-sided wiring circuit in which a wiring circuit is formed on one side of an insulating layer.
[0015]
Moreover, the insulating layer of the motherboard printed wiring board and the insulating layer of the substrate with wiring circuit can be made of a flexible resin such as polyimide, and the whole or a part thereof may be a flexible printed wiring board. it can. Moreover, it is preferable that the insulating layer of the motherboard printed wiring board and the insulating layer of the substrate with wiring circuit are made of the same material from the viewpoint of thermal and mechanical influences.
[0016]
Further, in the multilayer wiring board according to the present invention, a cover layer for covering the motherboard printed wiring board and the substrate with wiring circuit is formed for protecting the conductive layer, or the arrangement part of the substrate with wiring circuit is provided. A cover layer having an opening is formed. And the wiring circuit of the motherboard printed wiring board exposed in the gap between the cover layer and the substrate with wiring circuit at the opening of the cover layer is covered with a noble metal from the wiring circuit, or the cover layer An additional cover layer is formed to cover the surface of the motherboard printed wiring board exposed in the gap between the cover layer and the substrate with wiring circuit in the opening.
[0017]
In the multilayer wiring board according to the present invention, the insulating layer of the substrate with a wiring circuit that comes into contact with the motherboard printed wiring board also serves as a cover layer that covers the motherboard printed wiring board among the substrates with the wiring circuit. .
[0018]
In the multilayer wiring board according to the present invention, the inner via hole of the substrate with wiring circuit is filled with a conductive paste for interlayer conduction, and further, the conductive layer of the substrate with wiring circuit is conductive. A small hole is formed which acts as an air vent hole when the paste is filled.
[0019]
In order to achieve the above-mentioned object, a method for manufacturing a multilayer wiring board according to the present invention includes a step of bonding a substrate with a wiring circuit that has been subjected to external processing to the front surface and / or the back surface of a mother board printed wiring board. Furthermore, it includes a step of bonding a wiring circuit formed substrate, a via hole formed, and a substrate with a printed wiring circuit to the front surface and / or back surface of the mother board printed wiring board.
[0020]
In this multilayer wiring board manufacturing method, it is not necessary to match the outer shape of the substrate with a wiring circuit to the outer shape of the motherboard printed wiring board, the outer shape of the substrate with a wiring circuit can be set smaller than the outer shape of the motherboard printed wiring board, The base material with the wiring circuit can be made into an island-like structure in which a necessary part is selected on the mother board printed wiring board.
[0021]
Further, in this method of manufacturing a multilayer wiring board, before the step of bonding the substrate with wiring circuit to the mother board printed wiring board, the bonding portion of the substrate with wiring circuit is opened in the mother board printed wiring board. Forming a cover layer.
[0022]
In addition, the method of manufacturing the multilayer wiring board includes a step of forming a cover layer that covers the motherboard printed wiring board and the substrate with wiring circuit after the step of bonding the substrate with wiring circuit to the motherboard printed wiring board. including.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show a basic embodiment of a multilayer wiring board according to the present invention. In the multilayer wiring board of the present embodiment, partial wiring boards (multilayered portions) 20 that have been subjected to outline processing in advance are pasted together in islands at a plurality of locations on the front and back of the motherboard printed wiring board (base board) 10. ing. The partial wiring board 20 is obtained by collectively laminating a plurality of single-sided wiring circuit-equipped resin base materials 21 on the front and back of the mother board printed wiring board 10 that have been processed into a predetermined shape smaller than the outer shape of the mother board printed wiring board 10 in advance. It is. In addition, the partial wiring board 20 can also be multilayered including the resin base material with a double-sided wiring circuit.
[0024]
The motherboard printed wiring board 10 has conductor layers (wiring circuits) 12 on both the front and back surfaces of the insulating base material 11. The insulating base 11 of the motherboard printed wiring board 10 can be made of a flexible resin such as polyimide. The resin base material 21 with a single-sided wiring circuit has a conductor layer (wiring circuit) 23 on one side of an insulating base material 22. The insulating base material 22 of the resin base material with single-sided wiring circuit 21 can also be made of a flexible resin such as polyimide in addition to the rigid prepreg.
[0025]
The conductor layers 23 of the multi-layered resin base material 21 with a single-sided wiring circuit, the conductor layers 23 of the resin base material 21 with a single-sided wiring circuit, and the conductor layer 12 of the motherboard printed wiring board 10 are each a resin with a single-sided wiring circuit. The inner via hole (via hole) 24 formed in the substrate 21 is electrically connected by a conductor 25 made of conductive paste or the like.
[0026]
A specific manufacturing method includes a step of bonding a resin substrate 21 with a single-sided wiring circuit that has been subjected to external processing to a part of the front surface and / or the back surface of the motherboard printed wiring board 10. Of course, this may be a build-up method in which the resin base materials 21 with single-sided wiring circuits are bonded one by one. However, when a simpler manufacturing process and reduction in manufacturing cost are desired, the printed circuit board for the motherboard Collective lamination in which a plurality of single-sided wiring circuit-equipped resin base materials 21 that have undergone wiring circuit formation, via hole formation, and outer shape processing are stacked on one part of the front surface or / and the back surface of 10 The law applies.
[0027]
The adhesion between the resin base materials 21 with single-sided wiring circuits and the adhesion between the resin base material 21 with single-sided wiring circuits and the motherboard printed wiring board 10 are performed with the conductor layer 23 of the insulating base material 22 of the resin base material 21 with single-sided wiring circuits. Can be performed by forming an adhesive layer (not shown) on the opposite surface and using this adhesive layer. If the insulating base material 22 of the resin base material 21 with a single-sided wiring circuit is thermoplastic polyimide, a material obtained by imparting a thermosetting function to a thermoplastic polyimide, or a liquid crystal polymer, etc. The adhesive layer can be omitted.
[0028]
According to these, the multilayered part for mounting electronic components (partial wiring board 20) can be freely arranged at a free position on the surface of the mother board printed wiring board 10, and the extra multilayered part can be reduced, and the material can be reduced. Costs can be greatly reduced.
[0029]
Even when a flexible part made of a flexible resin substrate such as polyimide and a rigid multi-layer part are mixed like a rigid flex printed wiring board, the above-mentioned problem can be obtained by using the above-mentioned motherboard printed wiring board 10 as a flex board. Is resolved. In particular, when the electronic component mounting part is made of an expensive material such as polyimide due to requirements such as dielectric properties and lightness, this effect can be said to be extremely large.
[0030]
In the case of such a board configuration, the insulating layer (insulating base material 22) of the partial wiring board 20 which is an electronic component mounting part and the insulating layer (insulating base material 11) of the flex part (motherboard printed wiring board 10) are provided. By using the same material and combining the thermal and mechanical properties of both, high thermal and mechanical reliability can be obtained.
[0031]
The mother board printed wiring board 10 is generally provided with a cover layer such as a cover layer or a solder resist for the purpose of protecting the conductive layer. The cover layer of the motherboard printed wiring board 10 may be formed by previously opening a portion that is multilayered by the resin base material 21 with a single-sided wiring circuit, and the resin base material 21 with a single-sided wiring circuit may be bonded to the opening. In this case, as shown in FIG. 3, a gap g is formed between the multi-layered portion (arrangement part of the partial wiring board 20) and the cover layer 13 in the opening 13 </ b> A. In the portion g, the conductive layer 12 is exposed (exposed externally).
[0032]
Therefore, in this case, as shown in FIG. 4, the exposed portion is covered with a noble metal 15 such as gold, which is nobler than the conductive layer 12, to prevent oxidation, or FIG. It is preferable to cover with a cover layer 16 of a solder resist or the like.
[0033]
Further, as shown in FIG. 6, the cover layer 16 is formed so as to cover a part of the multilayered portion with the motherboard printed wiring board 10 after the multilayered portions are bonded, for example, At the time of bending when the motherboard wiring board 10 is flex, it is possible to prevent a problem such as peeling at the interface between the multilayered portion and the bent portion.
[0034]
Further, in order to simplify the process, as shown in FIG. 7, a cover layer of the motherboard printed wiring board 10 and a resin substrate with a single-sided wiring circuit bonded to and directly above the motherboard printed wiring board 10 are attached. This is solved by a structure in which the insulating layer of the material 21 is integrally formed. More specifically, it includes a step of forming the insulating layer of the resin base material 21 with a single-sided wiring circuit and the cover layer of the mother board printed wiring board 20 from the same insulating layer 17 and bonding them to the mother board printed wiring board 10. It is a waste.
[0035]
Further, as shown in FIG. 8, the inner via hole 24 having these structures is formed as a conductive paste inner hole, and is smaller than the diameter of the resin substrate portion in the conductive layer 23 portion of the resin base material 21 with a single-sided wiring circuit. By forming the small holes 27 for venting air, it is possible to prevent voids remaining when the conductive paste is filled. The conductive paste is filled in the small holes 27 so that the small holes 27 do not become hollow. In FIG. 8, reference numeral 26 denotes an interlayer adhesive layer.
[0036]
Next, a method for producing a resin base material with a single-sided wiring circuit used in a multilayer wiring board according to an embodiment of the present invention will be described with reference to FIGS.
[0037]
Etching the copper foil 52 by a subtractive method using a polyimide base material 50 with a single-sided copper foil having a copper foil 52 on one side of the polyimide base material 51 as shown in FIG. 9 (a). Thus, a circuit-formed substrate 53 as shown in FIG. 9B was obtained. Of course, this can also be obtained by an additive method or a semi-additive method using a polyimide base material without a copper foil as a starting material.
[0038]
Next, as shown in FIG. 9C, an interlayer adhesive layer 54 is formed on the surface of the substrate 53 on which the circuit has been formed on the side opposite to the copper foil 52. As the interlayer adhesive layer 54, a thermoplastic polyimide having a thermosetting function was used. Of course, this may be a thermosetting resin represented by epoxy or a thermoplastic resin such as thermoplastic polyimide. I do not care.
[0039]
However, the three-layer configuration of the copper foil 52, the polyimide base material 51, and the interlayer adhesive layer 54 is asymmetrical on the front and back sides, and no warping that causes a problem occurs in the subsequent process with the adhesive layer formed. Is preferred. The interlayer adhesive layer 54 preferably has a glass transition temperature of 110 ° C. or lower and a normal temperature elastic modulus of 1300 MPa or lower.
[0040]
Next, as shown in FIG. 9 (d), after drilling (via hole processing) with a UV-YAG laser so as to penetrate the interlayer adhesive layer 54 and the polyimide base material 51, plasma irradiation is performed. Desmearing was performed by applying soft etching, and IVH was formed by filling hole 55 with silver paste 56 for filling holes.
[0041]
Of course, in addition to the UV-YAG laser, the laser can be processed at a higher speed by a carbon dioxide gas laser, an excimer laser, or the like. As a desmear method, wet desmear using a permanganate is also very common. As the conductive paste filled with IVH, various metal pastes such as a copper paste, a carbon paste, and a nickel paste can be used in addition to the silver paste.
[0042]
Next, as shown in FIG. 9 (e), as shown by the dotted line L, the object is to process the outer shape, and by pressing with a mold, the outer shape is processed to a desired size, The resin base material 57 with the single-sided wiring circuit shown by FIG.9 (f) was obtained. At this time, in order to prevent the IVH caused by the conductive paste 56 from being destroyed, it is necessary to temporarily cure the conductive paste 56 to such an extent that destruction does not occur even when contacted. Specifically, it is preferable that 2B or more is cured by pencil hardness.
[0043]
Next, a method for manufacturing a multilayer wiring board according to an embodiment of the present invention will be described with reference to FIGS.
[0044]
As shown in FIG. 10A, the opening portion of the motherboard FPC 60 in which the wiring circuit 61 has been formed and the cover layer 62 having the opening (opening portion 62A) of the portion to be laminated is formed on the surface. 62A, the two-layered resin base material 57 with a single-sided wiring circuit that has been subjected to the outer shape processing is overlaid after being aligned, and heated and pressurized under a vacuum degree of 1 kPa or less by a vacuum hot press machine, and FIG. A substrate 63 including a multilayered portion 64 as shown in b) was obtained.
[0045]
For alignment, a pin alignment method may be used, but it is not preferable because a space for opening a pin hole is required. Therefore, alignment by image recognition was performed.
[0046]
Next, as shown in FIG. 10 (c), on the substrate 63, the gap between the cover layer 62 and the multilayered portion 64 of the motherboard FPC 60, a part of the surface of the multilayered portion 64 and the surface of the cover layer 62. A multilayer resist board 66 was obtained by applying and curing a solder resist 65 by a printing method so as to cover a part.
[0047]
Next, a method for manufacturing a multilayer wiring board according to another embodiment of the present invention will be described with reference to FIGS. 11, parts corresponding to those in FIG. 10 are denoted by the same reference numerals as those in FIG.
[0048]
As shown in FIG. 11A, resin base materials 57 and 70 with single-sided wiring circuits manufactured by the same method as in the above-described embodiment (FIG. 9) are applied to a motherboard FPC 60 in which the wiring circuit 61 has been formed. Two layers are overlaid after alignment. The resin base material 70 with a single-sided wiring circuit that contacts the circuit surface of the motherboard FPC 60 has an outer diameter shape that covers a portion to be covered with a cover layer, such as a copper foil portion of the motherboard FPC 60, by the insulating layer (polyimide base material 51). Thus, the insulating layer of the substrate 70 also serves as a cover layer.
[0049]
This alignment may be a pin alignment method, but it is not preferable because a space for making a pin hole is required. Therefore, alignment by image recognition was performed.
[0050]
After alignment, the substrate was heated and pressurized under a vacuum degree of 1 kPa or less with a vacuum hot press to obtain a substrate 71 shown in FIG. According to this method, a step is formed between the resin base materials 57 and 70 with a single-sided wiring circuit at the time of hot pressing. Therefore, it is preferable to have a cushion configuration that compensates for this step.
[0051]
Next, a method for manufacturing a multilayer wiring board according to another embodiment of the present invention will be described with reference to FIGS. Also in FIG. 12, parts corresponding to those in FIG. 10 are denoted by the same reference numerals as those in FIG. 10, and description thereof is omitted.
[0052]
As shown in FIG. 12A, the mother board FPC 60 in which the wiring circuit 61 has been formed and the cover layer 62 having openings (openings 62A and 62B) formed on the portions to be stacked is formed on the surface. Two-layered resin base material 57 with a single-sided wiring circuit that has been subjected to outer shape processing is placed in the opening 62A, after being aligned, and heated and pressurized under a vacuum degree of 1 kPa or less by a vacuum hot press machine. A multilayered portion 64 as shown in 12 (b) was obtained.
[0053]
Then, as shown in FIG. 12 (c), three-layered resin base material 57 with a single-sided wiring circuit that has undergone outline processing is overlaid on the other opening 62B of motherboard FPC 60 after alignment. In addition, a multilayered portion 67 as shown in FIG. 12D was obtained by heating and pressurizing under a vacuum degree of 1 kPa or less with a vacuum hot press.
[0054]
Next, as shown in FIG. 12 (e), the gap between the cover layer 62 and the multilayered portions 64 and 67 of the motherboard FPC 60, a part of the surface of the multilayered portions 64 and 67, and the surface of the cover layer 62 A multilayer resist board 68 was obtained by applying and curing a solder resist 65 by a printing method so as to cover a part.
[0055]
In this way, a multilayer structure can be obtained even when the number of layers is different between the multilayer portions, that is, when the thicknesses are different.
[0056]
【The invention's effect】
As can be understood from the above description, according to the multilayer wiring board and the method of manufacturing the same according to the present invention, at least one substrate with a wiring circuit that has been subjected to outline processing in advance is bonded to the mother board printed wiring board. Are electrically connected by an inner via hole in at least one place. The outer shape of the substrate with wiring circuit is smaller than the outer shape of the motherboard printed wiring board, and since the substrate with wiring circuit has an island shape on the motherboard printed wiring board, higher wiring flexibility can be obtained, and material cost Reduction of the substrate capacity can be achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a multilayer wiring board according to the present invention.
FIG. 2 is a plan view showing one embodiment of a multilayer wiring board according to the present invention.
FIG. 3 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIG. 4 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIG. 5 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIG. 6 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIG. 7 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIG. 8 is a cross-sectional view showing another embodiment of the multilayer wiring board according to the present invention.
FIGS. 9A to 9F are process diagrams showing a method for producing a resin substrate with a single-sided wiring circuit used in a multilayer wiring board according to an embodiment of the present invention.
FIGS. 10A to 10C are process diagrams showing a method for manufacturing a multilayer wiring board according to an embodiment of the present invention. FIGS.
11A and 11B are process diagrams showing a method for manufacturing a multilayer wiring board according to another embodiment of the present invention.
12A to 12E are process diagrams showing a method for manufacturing a multilayer wiring board according to another embodiment of the present invention.
FIGS. 13A to 13C are process diagrams showing a typical manufacturing process of a rigid flex printed wiring board. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Mother board printed wiring board 11 Insulating base material 12 Conductive layer 13 Cover layer 15 Precious metal 16 Cover layer 17 Insulating layer 20 Partial wiring board 21 Resin base material with single-sided wiring circuit Insulating base material 23 Conductive layer 24 Inner via hole 25 Conductor 27 Small Hole 26 Interlayer adhesive layer 50 Polyimide substrate 51 with single-sided copper foil Polyimide substrate 52 Copper foil 53 Circuit-formed substrate 54 Interlayer adhesive layer 55 Hole 56 Conductive paste 57 Resin substrate 60 with single-sided wiring circuit Motherboard FPC
61 Wiring Circuit 62 Cover Layer 63 Substrate 64 Multilayered Portion 65 Solder Resist 66 Multilayer Wiring Board 67 Multilayered Portion 68 Multilayer Wiring Board 70 Resin Base 71 with Single-sided Wiring Circuit Multilayer Wiring Board

Claims (9)

  At least one base material with a wiring circuit that has been subjected to outline processing is bonded to the mother board printed wiring board, and they are electrically connected to each other by an inner via hole at least at one place. The outer shape is smaller than the outer shape of the motherboard printed wiring board, the substrate with wiring circuit forms an island shape on the motherboard printed wiring board, and the placement portion of the substrate with wiring circuit is opened in the motherboard printed wiring board. A cover layer is formed, and a wiring circuit of the motherboard printed wiring board exposed in a gap between the cover layer and the base material with the wiring circuit is covered with a noble metal from the wiring circuit at an opening of the cover layer. Multilayer wiring board.   At least one base material with a wiring circuit that has been subjected to outline processing is bonded to the mother board printed wiring board, and they are electrically connected to each other by an inner via hole at least at one place. The outer shape is smaller than the outer shape of the motherboard printed wiring board, the substrate with wiring circuit forms an island shape on the motherboard printed wiring board, and the placement portion of the substrate with wiring circuit is opened in the motherboard printed wiring board. A multi-layer wiring in which an additional cover layer is formed to cover the surface of the motherboard printed wiring board exposed in the gap between the cover layer and the substrate with wiring circuit at the opening of the cover layer Board.   The multilayer wiring board according to claim 1 or 2, wherein a plurality of substrates with wiring circuits that have undergone external processing are laminated.   The multilayer wiring board according to any one of claims 1 to 3, wherein the substrate with a wiring circuit is a substrate with a single-sided wiring circuit in which a wiring circuit is formed on one side of an insulating layer.   The multilayer wiring board according to any one of claims 1 to 4, wherein an insulating layer of the mother board printed wiring board is made of a flexible resin such as polyimide.   The multilayer wiring board according to any one of claims 1 to 5, wherein the insulating layer of the substrate with a wiring circuit is made of a flexible resin such as polyimide.   The multilayer wiring board according to any one of claims 1 to 6, wherein an insulating layer of the mother board printed wiring board and an insulating layer of the substrate with wiring circuit are made of the same material. Multilayer wiring board according to any one of claims 1 to 7 to the inner via hole of the wiring circuit substrate with the conductive paste for interlayer conduction are filled. The multilayer wiring board according to claim 8 , wherein a small hole communicating with the inner via hole is formed in the conductive layer of the substrate with a wiring circuit.

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