JP2007180421A - Multilayer circuit board and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a multilayer circuit board and multilayer circuit board, where complex processes are not included in the manufacturing process, and the preparation and management of a design tool are easy at the designing stage. <P>SOLUTION: The manufacturing method of the multilayer circuit board 600 includes a process of preparing a substrate 102 and a double-sided circuit board, obtained by forming a first conductor and a second conductor on both of the sides of the substrate 102; a process of previously layering an interlayer adhesive 108 at a predetermined position of the double-sided circuit board; a process of folding the double-sided circuit board one or more times to make the multilayer circuit board, and thereafter connecting the first conductor and the second conductor through the interlayer adhesive 108; and a process of removing the periphery of the multilayer circuit board. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer circuit board and a multilayer circuit board.

  With the recent development of electronic devices such as mobile terminals, there is an increasing demand for higher functionality, smaller size and lighter weight. With this, printed wiring boards are becoming increasingly thin and multi-layered with high-density wiring. There is an increasing demand. Multilayer printed wiring boards are broadly divided into two types, through-through-hole plating and build-up methods. In addition, build-up methods include sequential build-up method, which performs sequential lamination, and parallel build-up, which performs lamination in a batch. Classified into methods.

The through-through-hole plating method is a method in which a double-sided wiring board or single-sided wiring board that has been patterned in advance is integrated as an inner layer circuit via an adhesive layer, then through holes are drilled with a drill to perform through-hole plating. Is a method of electrically connecting the two.
In addition, the sequential buildup method uses the multilayer wiring board produced by the through-hole plating method as a core substrate, forms an insulating layer on the surface layer, and then conducts the outermost layer and the core substrate through blind vias, There is a method of sequentially laminating a series of processes for forming a wiring circuit in the outermost layer (for example, Patent Document 1).

In the parallel buildup method, a blind via is formed on a circuit-molded insulating base and the inside of the via is filled with plating or conductive paste is prepared for each layer, and these are positioned and stacked, and then laminated together by hot pressure. There are methods (for example, Patent Document 2).
However, these multi-layer wiring boards require a process for forming a circuit separately for each layer regardless of which method is used, and require a large number of man-hours compared to single-sided wiring boards and double-sided wiring boards. The manufacturing process has become more complex in proportion to the number of layers.
Furthermore, at the design stage, each layer requires a lot of data such as wiring pattern data, drilling data, positioning guide hole data, outline processing data, and insulation mask data. It was necessary.

JP-A-8-125344 JP 11-54934 A

  The present invention has been made in view of the above circumstances, and there is no complicated process in the manufacturing process, and in the design stage, a method for manufacturing a multilayer circuit board that is easy to create and manage a design tool and It is to provide a multilayer circuit board.

  The method for producing a multilayer circuit board according to the present invention includes a multilayer circuit board obtained by folding at least one time a base material and a double-sided circuit board in which a first conductive part and a second conductive part are formed on both sides of the base material, respectively. Thereafter, the method includes a step of removing a peripheral portion of the multilayer circuit board.

In this multilayer circuit board manufacturing method, by folding the double-sided circuit board at a predetermined position, the number of folding times is obtained by multiplying two layers on both sides, for example, 1 × 2 + 2 = 4 in one folding. A multilayer circuit board with 6 layers can be obtained by folding twice. Thus, a multilayer circuit board can be obtained without going through complicated processes and without using a great number of design tools.
In the present invention, the folding step can take various forms.
For example,
The base material includes a rectangular first surface region, and a rectangular second surface region adjacent to and sharing one side of the first surface region,
The step of folding the double-sided circuit board may include a step of folding the base material with the side as a folded portion and overlapping the first surface region and the second surface region.
Further, the base material shares a rectangular first surface region, a rectangular second surface region sharing one side of the first surface region, and the other side of the first surface region. An adjacent rectangular third surface region,
The step of folding the double-sided circuit board includes:
A first folding step in which the base is folded with the one side as a folded portion, and the first surface region and the second surface region are overlapped with each other;
A second folding step of further folding the base material with the other side as a folded portion, and overlapping the first surface region, the second surface region, and the third surface region;
It is good also as a structure containing.
If it does as mentioned above, a base material can be used effectively and a multilayer substrate can be produced efficiently by a simple process.

  According to the present invention, it is possible to provide a method for manufacturing a multilayer circuit board and a multilayer circuit board that are free from complicated processes in the manufacturing process and that are easy to create and manage a design tool in the design stage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, common constituent elements are denoted by the same reference numerals, and detailed description thereof will be appropriately omitted in the following description.

The method for manufacturing a multilayer circuit board according to this embodiment is as follows.
Preparing a double-sided circuit board comprising a base material and a first conductive part and a second conductive part provided on at least one surface of the base material;
Covering at least one of the first conductive part and the second conductive part provided on the one surface with an interlayer adhesive;
A state in which the double-sided circuit board is folded at least once, and the first surface region provided with the first conductive part and the second surface region provided with the second conductive part are opposed to each other through the interlayer adhesive. And a process of
By heat-pressing in the state, the interlayer adhesive in the portion sandwiched between the first conductive portion and the second conductive portion is melted and removed, and the first conductive portion and the second conductive portion are electrically connected. Forming a multilayer circuit board, and
And removing a peripheral portion of the multilayer circuit board to obtain a multilayer circuit board.
Here, the base material is adjacent to the rectangular first surface region, the rectangular second surface region sharing one side of the first surface region, and the other side of the first surface region. And a third surface region having a rectangular shape. The step of folding the double-sided circuit board includes (i) a first folding step in which the base is folded with the one side as a folded portion, and the first surface region and the second surface region are overlapped with each other, and (ii) the other side And a second folding step of further folding the base material with the first surface region, the second surface region, and the third surface region superimposed.
That is, as shown in FIGS. 1 and 2, the method for manufacturing the multilayer circuit board 600 according to the present embodiment includes the base material 102, and the first conductive portion 105 and the second conductive portion 115 on both sides of the base material 102. A step of preparing the double-sided circuit board 109 on which the multilayer circuit board 109 is formed, a step of previously laminating the interlayer adhesive 108 at a predetermined position of the double-sided circuit board 109, and the multilayer circuit board 550 by folding the double-sided circuit board 109 at least once After that, a step of connecting the first conductive portion 105 and the second conductive portion 115 via the interlayer adhesive 108 and a step of removing the peripheral portion of the multilayer circuit board 550 are included.

FIG. 3 is a diagram showing a schematic configuration of an embodiment of a multilayer circuit board 600 obtained by the manufacturing method of the present invention.
In the multilayer circuit board 600, the double-sided circuit board 109 is formed of three configurations in the present embodiment to form a six-layer multilayer circuit board 600. An interlayer adhesive 108 is connected between the layers of the double-sided circuit board 109. Further, the outermost layers of the multilayer circuit board 600 are each covered with an insulating coating 107. In the double-sided circuit board 109, the connection between the layers has a filled via plating 103 structure in which a hole penetrating the base material 102 is filled with plating or conductive paste. In connection between the layers, the first conductive portion 105 and the second conductive portion 115 are connected through the metal coating layer 104.

  Next, an example of a method for manufacturing the multilayer circuit board 600 according to the present embodiment will be described with reference to FIGS.

Examples of the material constituting the base material 102 include a resin film base material. Examples of the resin film substrate include polyimide resin films such as polyimide resin films, polyetherimide resin films, polyamideimide resin films, polyamide resin films such as polyamide resin films, and polyester resin films such as polyester resin films. Can be mentioned. Of these, a polyimide resin film is particularly preferably used from the viewpoint of improving the elastic modulus and heat resistance.
First, a double-sided laminate having a polyimide resin film substrate 102 with a copper foil 101 as a metal foil is prepared. At this time, a substrate 102 bonded with a copper foil 101 using an adhesive may be used.
Next, the copper foil 101 is removed from the double-sided laminated board by etching or laser, and then a blind via hole penetrating through the resin and reaching the other copper foil is further formed by laser or resin etching. At this time, the blind via hole may be formed only on one side of the double-sided plate or on both sides. Further, desmear treatment is performed in the brand via hole with permanganate or plasma, and a filled via 103 is formed by electrolytic plating (FIG. 1A). The filled via at this time may use electroless plating or may fill the inside of the blind via using another conductive material. Further, the metal coating layer 104 is formed on the necessary filled via using a plating method, a paste printing method, or the like. In this case, the metal coating layer 104 is a solder metal composed of at least one metal selected from tin, lead, silver, copper, zinc, nickel, bismuth, antimony, indium, and gold. Examples include tin, tin-lead, tin-silver, tin-zinc, tin-bismuth, tin-antimony, tin-silver-bismuth, and tin-copper, but combinations and compositions of metal elements It is not limited to this, and an optimal one may be selected. Although the thickness of the metal coating layer 104 is not specifically limited, Preferably it is 3-30 micrometers, More preferably, it is 10-15 micrometers. Further, for the purpose of preventing connection deterioration due to metal diffusion between the metal coating layer 104 and the copper foil layer at the time of soldering, a barrier layer of nickel or the like may be formed as a base treatment by 1 to 2 μm.

  Subsequently, the double-sided laminated board is pattern-etched with a photosensitive photoresist to form the second conductive portion 115 and the first conductive portion 105 on both sides of the insulating base (FIG. 1B). At this time, the first conductive portion 105 can be freely adjusted with a photomask such as a cylinder or a quadrangular prism.

  Next, an insulating coating 107 is applied to the necessary part of the double-sided board (FIG. 1C). The location of the insulating coating 107 is a portion that needs to be bent by a flex rigid or a multilayered flex, and finally a portion that corresponds to the outermost layer. The insulating coating 107 at this time is selected from a cover lay film made of a flexible and heat-resistant insulating resin such as polyimide and an adhesive, a thermosetting resist ink, a photosensitive resist ink, and the like. It can be coated on one or both sides.

Next, an interlayer adhesive 108 (adhesive with a flux function) is formed on necessary portions on the first conductive portion 105 and the conductor circuit 106 and the base material 102 of the double-sided plate (FIG. 1D). The adhesive 108 with a flux function used here is an adhesive having a cleaning function of a metal surface, for example, a function of removing an oxide film existing on the metal surface and a function of reducing an oxide film, and is a first preferable adhesion. The composition of the agent includes a resin (A) such as a phenol novolak resin having a phenolic hydroxyl group, a cresol novolak resin, an alkylphenol novolak resin, a resole resin, or a polyvinylphenol resin, and a curing agent (B) for the resin. Curing agents are epoxidized based on bisphenol, phenol novolac, alkylphenol novolac, biphenol, naphthol, resorcinol and other skeletons such as aliphatic, cycloaliphatic and unsaturated aliphatic skeletons. Examples of the second preferable adhesive composition include phenolic bases such as bisphenol, phenol novolac, alkylphenol novolac, biphenol, naphthol, resorcinol, aliphatic, and cyclic fats. Epoxy resin (C) epoxidized on the basis of a skeleton such as an aliphatic or unsaturated aliphatic group, an imidazole ring, and a curing agent (D) for the epoxy resin. Examples of the curing agent having an imidazole ring include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, and 2-phenyl-4. -Methylimidazole, bis (2-ethyl-4-methyl-imidazole) and the like.
A method for forming the interlayer adhesive 108 is not particularly limited, and examples thereof include a printing method and a transfer method. A method of laminating a sheet-like adhesive is simple and preferable.

Next, the double-sided plates are folded and stacked (FIG. 2).
The folding may be performed by using a method of folding one side of the rectangular figure or by folding another adjacent side of the rectangular drawing.
At this time, in order to make it easier to fold, a guide hole can be provided so that a part is cut, a slit of a crease is inserted in the bent portion, or the folding is not displaced. At this time, if a part is left without being completely separated from the double-sided plate, it is possible to process to the final process without being restricted in handling.

  The method of bending is, for example, the method shown in FIGS. 4A and 4B, and is not particularly limited. The first conductive portion 105, the second conductive portion 115, and the adhesive 108 with a flux function are arranged. The optimal bending method may be selected according to the above. Here, the folding method of FIG. 4A will be described with reference to FIG. Furthermore, as shown in FIG. 5 and FIG. 6, by combining not only the left and right folds but also the front and rear folds, a multilayer printed wiring board having six or more layers, or a flexibly combined flex part and component mounting part Applicable to rigid wiring boards.

Next, the folded double-sided plates are integrated (FIG. 2). Such multilayering is performed while thermocompression bonding, that is, pressure bonding under heating. The specific method is as follows.
Heating to the first temperature at which the metal coating layer melts, and thermocompression bonding until the metal coating layer 104 of the first conductive portion 105 is melt-bonded to the second conductive portion 115 via the adhesive layer 108 with a flux function. Then, the metal coating layer 104 is not melted again and is reheated at a second temperature suitable for the adhesive to be cured to cure the adhesive layer 108 with a flux function, and to bond the layers. , Laminated and integrated. As described above, in the thermocompression bonding process, by performing a temperature difference, the metal coating layer 108 is sufficiently melted to prevent poor bonding, and immediately after such fusion bonding is performed, the adhesive with a flux function is used. The layer 108 is cured to fix the joints and melt joints of each layer (FIG. 2B).
As a method of laminating each layer, for example, a vacuum press or a method using a combination of thermal lamination and baking can be used.
The first temperature is preferably 170 to 270 ° C., more preferably 185 to 260 ° C., and the second temperature is preferably 120 to 200 ° C., more preferably 150 to 190 ° C. Can do.

  Finally, a desired outer shape is cut to obtain a multilayer circuit board 600 (FIG. 2C).

A method for producing an eight-layer multilayer flexible printed wiring board using the present invention will be introduced as an example. First, on a flexible double-sided copper clad laminate having a copper foil thickness of 18 μm and a polyimide thickness of 25 μm, a brand via hole is formed at a predetermined location by a UV laser, and after filled with plasma desmear, filled via plating is formed. Next, a dry film photoresist is laminated as a protective film, and a predetermined portion is exposed and developed, and then Sn-Ag solder plating is performed by 15 μm. Furthermore, a dry film photoresist is again laminated, and the first conductive portion and the second conductive portion are formed by etching to obtain a double-sided flexible printed wiring board. At this time, as shown in FIG. 5 (a), this double-sided flexible printed circuit is a circuit 110 of (1) in which the front and back sides of the double-sided flexible printed wiring board worksheet 109 are sandwiched between the first layer and the second layer. The third and fourth layers (2) 111, the fifth and sixth layers (3) 112, and the seventh and eighth layers (4) 113 are patterned. Have been In addition, when these are folded, the second layer, the fourth layer, the fifth layer, and the seventh layer are arranged on one side and the other side on the opposite side in order to overlap in order from the first layer to the eighth layer. Are arranged with a first layer, a third layer, a sixth layer, and an eighth layer. Next, the coverlay film is insulatively coated on the bent portions 114 that require flexibility of the circuit 111 of (2) corresponding to the third layer and the fourth layer and the circuit 112 of (3) corresponding to the fifth layer and the sixth layer. Further, an adhesive layer having a flex function is laminated on the second layer portion (1), the seventh layer portion (4), and the fourth layer portion (2) excluding the bent portion 114.
Next, as shown in FIG.5 (b), the crease | fold 125 is given to the part to fold using a metal mold | die.
Next, as shown in FIG. 5C, the periphery of the outer shape is cut 116 with a mold, and a positioning guide hole 117 for overlapping is formed. A part of the outer periphery of the circuit 113 in (4) is left without being cut. Thereby, since it hold | maintains on the double-sided flexible printed wiring board worksheet 109, handling and conveyance can be easily performed in processes, such as subsequent terminal plating, continuity inspection, and punching. At this time, a portion corresponding to the boundary between the bent portion and the laminated portion is cut 126 in advance in consideration of the outer shape punching in the final process.
Next, as shown in FIG. 6A, the circuit 112 in (3) and the circuit 111 in (2) are overlapped on the (2) side along the fold 125 to become a circuit 118. Further, as shown in FIG. 6B, a circuit 118 in which the circuit 111 in (2) and the circuit 112 in (3) are overlapped becomes a superimposed circuit 119 along the fold 125 on the (4) side. Finally, as shown in FIG. 6C, the circuit 110 of (1) is overlapped on the circuit 119 side along the fold 115 to form a circuit 120. At this time, positional deviation is prevented by using a guide pin.
Then, after temporarily bonding at 130 ° C. and 0.2 MPa for 30 seconds with a vacuum pressure laminator, pressing is performed at 250 ° C. and 0.05 MPa for 3 minutes. At this time, the adhesive with the flux function exhibits the flux function, and the Sn-Ag solder on the surface layer of the first conductive part melts, so that a metal bond is formed between the second conductive parts overlapping the first conductive part. To do. Further, the adhesive layer is completely cured by baking at 180 ° C. for 1 hour. Finally, the outermost layer is covered with a solder resist, the terminal portion for mounting is subjected to surface treatment by plating or the like, and a multilayer flexible printed wiring board is obtained by outer shape punching.

It is sectional drawing for demonstrating the manufacturing method of this invention. It is sectional drawing for demonstrating the manufacturing method of this invention. It is sectional drawing for demonstrating the multilayer circuit board manufactured by this invention. It is sectional drawing for demonstrating the lamination | stacking method of this invention. It is a top view for demonstrating the lamination method of this invention. It is a top view for demonstrating the lamination method of this invention.

Explanation of symbols

101: Copper foil 102: Substrate 103: Filled via plating 104: Metal coating layer 105: First conductive part 106: Conductor circuit 107: Insulation coating 108: Interlayer adhesive (adhesive with flux function)
109: Double-sided flexible printed wiring board worksheet (double-sided circuit board)
110: second layer surface (lower surface first layer surface) circuit 111: fourth layer surface (lower surface third layer surface) circuit 112: fifth layer surface (lower surface sixth layer surface) circuit 113: seventh layer surface (lower surface eighth layer surface) circuit 114: Bending portion 115: second conductive portion 116: cutting 117: guide hole 118: sixth layer surface (lower surface fifth layer, fourth layer, third layer surface) circuit 119: third layer surface (lower surface fourth layer, fifth layer, 6th layer, 7th layer, 8th layer surface) circuit 120: 1st layer surface (lower surface 2nd layer, 3rd layer, 4th layer, 5th layer, 6th layer, 7th layer, 8th layer surface) circuit 125 : Crease 126: Cutting 550: Multilayer circuit board 600: Multilayer circuit board

Claims (9)

Preparing a double-sided circuit board comprising a base material and a first conductive part and a second conductive part provided on at least one surface of the base material;
Covering at least one of the first conductive part and the second conductive part provided on the one surface with an interlayer adhesive;
A state in which the double-sided circuit board is folded at least once, and the first surface region provided with the first conductive part and the second surface region provided with the second conductive part are opposed to each other through the interlayer adhesive. And a process of
By heat-pressing in the state, the interlayer adhesive in the portion sandwiched between the first conductive portion and the second conductive portion is melted and removed, and the first conductive portion and the second conductive portion are electrically connected. Forming a multilayer circuit board, and
And a step of removing a peripheral portion of the multilayer circuit board to obtain a multilayer circuit board.   The method for manufacturing a multilayer circuit board according to claim 1, wherein the substrate is a resin film.   The method for producing a multilayer circuit board according to claim 2, wherein the resin film is a polyimide resin film.   4. The method for manufacturing a multilayer circuit board according to claim 1, wherein the double-sided circuit board has a filled via structure.   The method for manufacturing a multilayer circuit board according to any one of claims 1 to 4, wherein a metal coating layer is formed on a surface of the first conductive portion or the second conductive portion.   The method for manufacturing a multilayer circuit board according to claim 5, wherein the metal coating layer is made of solder or a low melting point metal and has a thickness of 3 μm or more and 30 μm or less. The base material includes a rectangular first surface region, and a rectangular second surface region adjacent to and sharing one side of the first surface region,
The step of folding the double-sided circuit board includes a step of folding the base material with the side as a folded portion and overlapping and opposing the first surface region and the second surface region,
A method for manufacturing a multilayer circuit board according to any one of claims 1 to 6. The base material is adjacent to a rectangular first surface region, a rectangular second surface region sharing one side of the first surface region, and sharing another side of the first surface region. A rectangular third surface region,
The step of folding the double-sided circuit board includes:
A first folding step in which the base is folded with the one side as a folded portion, and the first surface region and the second surface region are overlapped with each other;
A second folding step of further folding the base material with the other side as a folded portion, and overlapping the first surface region, the second surface region, and the third surface region;
including,
A method for manufacturing a multilayer circuit board according to any one of claims 1 to 6. A multilayer circuit board manufactured by the method according to claim 1.

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