JP2005277011A - Multilayer board and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variations in thickness occurring when laminating a plurality of boards, and prevent the separation of a coating layer provided on the boards. <P>SOLUTION: A multilayer board comprises a first conductor circuit, a first board having a coating layer that covers part of the first conductor circuit, a second board adjacent to the part which is not coated with the coating layer of the first board, and a third board adjacent to the second board. The end of the third board projects beyond a boundary section between the coating layer and the second board towards the coating layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer substrate and a manufacturing method thereof.

  With the recent increase in the density of electronic devices, the multilayered printed wiring board used for this has progressed. Such multilayer printed wiring boards are roughly classified into multilayer flexible printed wiring boards in which flexible printed wiring boards are laminated, and rigid flex printed wiring boards that are composite boards of flexible printed wiring boards and rigid printed wiring boards. The

  Among these, in the multilayer flexible wiring board having the flexible part having flexibility and the rigid part and the above-mentioned rigid flex printed wiring board, the flexible part (flexible printed wiring board) protrudes from the rigid part (rigid printed wiring board). It has an exposed part (see, for example, Patent Document 1).

Such an exposed portion is provided with a coating layer for protecting the formed conductor circuit.
However, in a multilayer printed wiring board provided with this coating layer, a flexible part (flexible printed wiring board) and a rigid part (rigid printed wiring board) are overlapped, and the rigid part (rigid printed wiring board) is partially In some cases, the thickness of the layer was not stable.
Furthermore, if the flexible part (flexible printed wiring board) is bent in this state, stress concentrates on the boundary part due to the difference in thickness between the rigid part (rigid printed wiring board) and the flexible part, and the layers are peeled off. Problems such as being easy and peeling of the surface coating layer are expected.

JP 2003-258426 A

  An object of the present invention is to reduce thickness variations caused by stacking a plurality of substrates and to prevent peeling of a coating layer provided on the surface of the substrate.

Such an object is achieved by the present invention described in the following (1) to (6).
(1) A first substrate having a first conductor circuit and a coating layer covering a part of the first conductor circuit, and a portion of the first substrate not covered with the coating layer A multilayer substrate having a second substrate adjacent to the second substrate and a third substrate adjacent to the second substrate, wherein an end of the third substrate is formed between the coating layer and the second substrate. A multilayer substrate characterized by protruding beyond the boundary portion toward the coating layer.
(2) The multilayer substrate according to (1), wherein a length of the protruding portion is 0.3 mm or more from the boundary portion to the coating layer side.
(3) The multilayer substrate according to (1) or (2), wherein the coating layer has a thickness of 15 to 60 μm.
(4) The multilayer substrate according to any one of (1) to (3), wherein the coating layer includes a resin film and an adhesive layer.
(5) The multilayer substrate according to any one of (1) to (4), wherein the first substrate has flexibility.
(6) A first step of covering a part of the first conductor circuit of the first substrate having the first conductor circuit with a coating layer, and a portion not covered with the coating layer of the first substrate. And a second step of laminating a second substrate adjacent to the second substrate, and a third step of laminating a third substrate adjacent to the second substrate. In the third step, the end portion of the third substrate protrudes toward the coating layer beyond the boundary between the coating layer and the second substrate and is laminated. Production method.

According to the present invention, it is possible to reduce variations in thickness caused by stacking a plurality of substrates and to prevent peeling of the coating layer provided on the surface of the substrate.
In addition, when the protruding portion has a specific length, it is possible to improve the level difference at the portion where the flexible portion and the rigid portion overlap.
In addition, when a flexible substrate is used as the first substrate, a multilayer substrate having particularly excellent flexibility can be obtained.

Hereinafter, a six-layer flexible wiring board which is one of the multilayer substrates of the present invention and a method for manufacturing the same will be described in detail based on preferred embodiments.
FIG. 1 is a cross-sectional view showing the manufacturing process of the outer layer circuit board. FIG. 2 is a cross-sectional view showing the manufacturing process of the inner layer circuit board. FIG. 3 is a cross-sectional view showing a manufacturing process of a circuit board serving as a core. FIG. 4 is a cross-sectional view showing a manufacturing process of a six-layer flexible wiring board.

First, the outer circuit board 100 (third board) will be described.
For example, a single area layer plate 110 having a copper foil 12 attached to one surface of a base material 11 made of an insulating material obtained by curing a resin such as polyimide resin or epoxy resin is prepared (FIG. 1A). As a method for processing the outer layer circuit board 100, the copper foil 12 and the base material 11 are bonded together between the base material 11 and the copper foil 12 in order to prevent the occurrence of smear that hinders conductor connection. However, it is preferable that the adhesive layer does not exist for this purpose, but an adhesive layer may be used. A wiring pattern 121 is formed by etching the copper foil 12 on one side of the substrate 11 (FIG. 1B).

  Next, the surface coating layer 13 is formed on the wiring pattern 121 (FIG. 1C). The surface coating layer 13 includes a method of attaching an overlay film obtained by applying an adhesive to an insulating resin, or printing ink directly on a substrate. The surface coating layer 13 may be provided with a surface coating layer opening 131 for surface treatment such as plating. Next, the substrate opening 111 is formed from the surface on the substrate 11 side until the wiring pattern 121 is exposed (FIG. 1D). At this time, if the laser method is used, the substrate opening 111 can be easily formed, and a small diameter can be opened. Further, it is preferable to remove the resin remaining in the substrate opening 111 by a method such as wet desmearing with an aqueous potassium permanganate solution or dry desmearing with plasma, because the reliability of interlayer connection is improved. The conductor post 14 is formed in the base material opening 111 until it protrudes from the surface of the base material 11 (FIG. 1 (f)).

  As a method for forming the conductor post 14, after forming the copper post 141 by a paste or plating method (FIG. 1E), the coating layer 142 is formed of a metal or an alloy. The height of the copper post 141 is not particularly limited, but is preferably 2 to 30 μm, particularly preferably 5 to 20 μm from the surface of the substrate 11. The metal is preferably made of tin. The alloy is preferably a solder composed of at least two kinds of metals selected from tin, lead, silver, zinc, bismuth, antimony, and copper. Examples include tin-lead, tin-silver, tin-zinc, tin-bismuth, tin-antimony, tin-silver-bismuth, and tin-copper, but are limited to solder metal combinations and compositions. What is necessary is just to select an optimal thing. Although thickness is not specifically limited, 2 micrometers or more are preferable and 5-20 micrometers is especially preferable. At this time, the surface treatment layer 132 may be simultaneously formed on the surface of the surface coating layer opening 131 with the same solder, metal, or alloy (FIG. 1 (f)).

  Further, an adhesive 15 with flux function (FIG. 1 (g)) layer is formed on the multilayer laminated portion. The adhesive layer 15 with a flux function includes a method of applying the adhesive agent 15 with a flux function to the substrate 11 by a printing method, and the like, and is formed by a method of laminating the sheet-like adhesive on the substrate 11. May be. Finally, the outer layer circuit board 100 is obtained by cutting according to the size of the multilayer portion (FIG. 1 (g)).

  Further, as a manufacturing method of this outer layer circuit board 100, after forming the base material opening 111 in the single area layer board 110, the conductor post 14 is formed, then the wiring pattern 121 is formed, and the surface coating layer 13 is applied to the wiring pattern. May be.

  The adhesive 15 with a flux function used in the present invention is an adhesive having a function of cleaning 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. As the composition of the adhesive 15 with a flux function, a resin (A) having a (solid) phenolic hydroxyl group such as a phenol novolac resin having a phenolic hydroxyl group, a cresol novolac resin, an alkylphenol novolak resin, a resole resin, or a polyvinylphenol resin; And a curing agent (resin that acts as a solid curing agent) (B) of the resin. Examples of the curing agent include phenol-based compounds such as bisphenol-based, phenol novolak-based, alkylphenol novolak-based, biphenol-based, naphthol-based, resorcinol-based, and skeletons such as aliphatic, cycloaliphatic and unsaturated aliphatic. Examples thereof include epoxidized epoxy resins and isocyanate compounds.

  Although content of resin which has a phenolic hydroxyl group is not specifically limited, 20 to 80 weight% is preferable in all the adhesive agents, and 35 to 60 weight% is especially preferable. If the content is less than the lower limit, the effect of cleaning the metal surface may be reduced, and if the content exceeds the upper limit, a sufficient cured product cannot be obtained, resulting in a decrease in bonding strength and reliability. There is a case.

  Further, the content of the resin or compound acting as a curing agent is not particularly limited, but is preferably 20 to 80% by weight, particularly preferably 35 to 65% by weight in the total adhesive. A colorant, an inorganic filler, various coupling agents, a solvent, and the like may be added to the adhesive with flux function 15 as necessary.

The composition of the second preferable adhesive 15 with a flux function includes phenol bases such as bisphenol, phenol novolac, alkylphenol novolac, biphenol, naphthol, resorcinol, aliphatic, cycloaliphatic and unsaturated fat. An epoxy resin (C) epoxidized based on a skeleton such as a family, and a curing agent (D) of the epoxy resin having an imidazole ring.
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. Examples include -4-methylimidazole and bis (2-ethyl-4-methyl-imidazole).

  Although content of the said epoxy resin is not specifically limited, 30 to 99 weight% is preferable in all the adhesive agents, and 40 to 90 weight% is especially preferable. When the content is less than the lower limit value, a sufficient cured product may not be obtained, and when the content exceeds the upper limit value, it may become brittle.

  Although it does not specifically limit as content of the hardening | curing agent of the said epoxy resin which has an imidazole ring, 1 to 10 weight% is preferable in all the adhesive agents, and 2 to 8 weight% is especially preferable. If the content is less than the lower limit, the effect of cleaning the metal surface is reduced, and the epoxy resin may not be cured sufficiently. If the content exceeds the upper limit, the curing reaction proceeds rapidly, and adhesion with a flux function is performed. The fluidity of the agent 15 may decrease.

  The configuration of the second preferable adhesive 15 with a flux function may contain a thermosetting resin or a thermoplastic resin such as a cyanate resin, an acrylic acid resin, a methacrylic acid resin, or a maleimide resin in addition to the two components. . Furthermore, you may add a coloring agent, an inorganic filler, various coupling agents, a solvent, etc. as needed.

  The adjustment method of the adhesive 15 with a flux function is, for example, a method in which a resin (A1) having a solid phenolic hydroxyl group and a resin (B1) acting as a solid curing agent are dissolved in a solvent and adjusted, a solid phenolic A method of dissolving and adjusting a resin (A1) having a hydroxyl group in a resin (B2) that acts as a liquid curing agent, a resin (B1) that acts as a solid curing agent and a resin (A2) having a liquid phenolic hydroxyl group And a method of dispersing or dissolving the curing agent (D) of the epoxy resin having an imidazole ring in a solution in which a solid epoxy resin (C) is dissolved in a solvent. Examples of the solvent to be used include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, toluene, butyl cello soble, ethyl cello soluble, N-methyl pyrrolidone, and γ-butyl lactone. A solvent having a boiling point of 200 ° C. or lower is preferable.

Next, the inner layer circuit board 200 (second board) will be described.
As a method of processing the inner layer circuit board 200, a single area layer board 210 having a copper foil 22 attached to one side of a base material 21 made of an insulating material obtained by curing a resin such as polyimide resin or epoxy resin is prepared (FIG. 2 ( a)). At this time, there is no adhesive layer between the base material 21 and the copper foil 22 for bonding the copper foil 22 and the base material 21 in order to prevent the occurrence of smear that hinders conductor connection. Although it is preferable, there is no problem even if it is bonded using an adhesive. Conductive pads 222 that can receive the wiring pattern 221 and the conductive posts 14 are formed by etching the copper foil 22 on one side of the base material 21 (FIG. 2B).

Next, the substrate opening 211 is formed from the surface on the substrate 21 side until the wiring pattern 221 is exposed (FIG. 2C).
At this time, if a laser method is used, the opening can be easily formed and a small diameter can be opened. Furthermore, it is preferable to remove the resin remaining in the base material opening 211 by a method such as wet desmearing with an aqueous potassium permanganate solution or dry desmearing with plasma, because the reliability of interlayer connection is improved. The conductor post 24 is formed in the base material opening 211 until it protrudes from the surface of the base material 21 (FIG. 2E).

  As a method for forming the conductor post 24, a copper post 241 is formed by a paste or plating method (FIG. 2D), and a coating layer 242 is formed of a metal or an alloy (FIG. 2E). Although it does not specifically limit as a height of the copper post 241, 2-30 micrometers in height from the base material 21 surface is preferable, and 5-20 micrometers is especially preferable. The metal is preferably made of tin. The alloy is preferably a solder composed of at least two kinds of metals selected from tin, lead, silver, zinc, bismuth, antimony, and copper. Examples include tin-lead, tin-silver, tin-zinc, tin-bismuth, tin-antimony, tin-silver-bismuth, and tin-copper, but are limited to solder metal combinations and compositions. What is necessary is just to select an optimal thing. The thickness is not particularly limited, but is preferably 2 μm or more, and particularly preferably 5 to 20 μm (FIG. 2 (e)). If the thickness is less than the lower limit value, the connection reliability between the layers may be reduced, and if the thickness exceeds the upper limit value, the height of the conductor post may vary and the connection reliability between the layers may be reduced.

Next, an adhesive 25 with flux function (FIG. 2 (f)) layer is formed on the multilayer laminated portion. The adhesive layer 25 with the flux function includes a method of applying the adhesive agent 25 with the flux function to the base material 21 by a printing method, and the like. It may be formed by a method. The inner layer circuit board 200 is obtained by these manufacturing methods (FIG. 2 (f)).
As the adhesive 25 with a flux function, the same adhesive as the adhesive 15 with a flux function described above can be used.

Next, the circuit board 300 (first board) serving as a core will be described.
As a method of processing the circuit board 300 serving as a core, for example, a double-sided board 310 in which copper foils 32 are formed on both sides of a heat-resistant resin film 31 used for a flexible wiring board such as polyimide is prepared (FIG. 3 ( a)). The double-sided board 310 is a material for the flexible part. That is, it has flexibility. Therefore, it is preferable that an adhesive layer is not present between the copper foil 32 and the resin film 31 in order to improve the flexibility and bendability.

  After the through hole 33 is formed in the double-sided plate 310, the front and back electrical continuity is formed by plating (FIG. 3B), and then the wiring pattern (first conductor circuit) 321 and the conductor post are etched. 24 is formed (FIG. 3C).

Next, a coating layer 34 made of polyimide or the like is applied so as to cover a part of the wiring pattern 321 to obtain a circuit board 300 serving as a core (FIG. 3D). Thereby, the covering portion 35 and the exposed portion 36 can be separated at the boundary portion 50. The covering portion 35 forms a flexible portion of the multilayer substrate.
Examples of the method for forming the coating layer 34 include a method of attaching a film with an adhesive having a two-layer structure of a resin layer and an adhesive layer by pressing, or printing an ink.

Although the coating layer 34 is not specifically limited, It is preferable to be comprised by two layers, the resin layer and the contact bonding layer.
Examples of the material constituting the resin layer include polyester resins, polyimides, and liquid crystal polymers. Among these, polyimide is preferable. Thereby, heat resistance and flexibility can be improved.

  Although the thickness of the said resin layer is not specifically limited, It is preferable that it is 5-50 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, the strength of the resin layer may be reduced, and if the thickness exceeds the upper limit value, slidability and flexibility may be reduced.

  Examples of the material constituting the adhesive layer include an acrylic adhesive, an epoxy adhesive, and a polyimide adhesive. Among these, an epoxy adhesive is preferable. Thereby, heat resistance and flexibility can be improved.

  Although the thickness of the said adhesive layer is not specifically limited, It is preferable that it is 5-40 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, circuit embedding may be insufficient, and if the thickness exceeds the upper limit value, the amount of adhesive stains increases, and the interlayer connection reliability decreases in the multilayer printed wiring board. Sometimes.

  The thickness of the coating layer 34 (the total of the resin layer and the adhesive layer) is not particularly limited, but is preferably 15 to 60 μm, and particularly preferably 25 to 50 μm. When the thickness is less than the lower limit value, the adhesion may be lowered, and when the thickness exceeds the upper limit value, the flexibility may be lowered.

The circuit board 300 (first board) serving as the core is not particularly limited, but preferably has flexibility. Thereby, the flexibility of a multilayer substrate can be improved.
The elastic modulus of the circuit board 300 (first substrate) serving as the core is not particularly limited, but is preferably 1.0 to 10 MPa, and particularly preferably 2.0 to 9.0 MPa. When the elastic modulus is within the above range, the flexibility is particularly excellent.
The elastic modulus can be measured, for example, according to ASTM D882.

Next, the six-layer flexible wiring board 400 will be described.
The inner circuit board 200 is stacked from both surfaces (upper and lower in FIG. 4A) of the circuit board 300 so as to be adjacent to the exposed portion 36 of the circuit board 300 serving as a core.
Next, the outer circuit board 100 is laminated from both sides (upper and lower in FIG. 4B) so as to be adjacent to the inner circuit board 200.
At this time, the end portion of the outer layer circuit board 100 protrudes toward the covering portion 35 beyond the boundary portion 50 between the covering portion 35 (covering layer 34) and the inner layer circuit board 200. Thereby, variation in thickness caused by stacking a plurality of substrates can be reduced. Furthermore, peeling of the coating layer 34 provided on the surface of the substrate can be prevented.

  The length of the protruding portion is not particularly limited, but is preferably 0.3 mm or more from the boundary portion 50 toward the coating layer 34 (covering portion 35), and particularly preferably 0.5 to 1.0 mm. If the length is less than the lower limit value, the effect of preventing peeling of the coating layer 34 may be reduced, and even if the length exceeds the upper limit value, further improvement in the effect cannot be expected.

And the obtained laminated body is heated and pressurized to obtain a six-layer flexible wiring board 400.
The six-layer flexible wiring board 400 is a rigid flex printed wiring board having a flexible portion 401 having flexibility and a rigid portion 402 that is rigid.
The heating condition is not particularly limited, but is preferably 220 to 270 ° C. and 0.005 to 0.1 MPa for 10 to 120 seconds, particularly preferably 230 to 260 ° C. and 0.01 to 0.05 MPa for 20 to 40 seconds. . When it is within the above range, it is particularly excellent in suppressing bleeding of the adhesive.

  The six-layer flexible wiring board 400 obtained under the above-described conditions is particularly excellent in reliability because a solder fillet is formed at the connection portion between the conductor post and the conductor pad.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited to this.
(Example 1)
1. Manufacture of the first substrate (circuit board as a core) A double-sided plate (Mitsui Chemical's NEX23FE (25T)) provided with copper foil (thickness 12 μm) on both sides of a polyimide film (thickness 25 μm) is drilled with a drill. After opening, direct plating was performed, and through holes were formed by electrolytic copper plating to form electrical conduction on the front and back sides. Thereafter, a conductor pad capable of receiving the wiring pattern and the conductor post was formed by etching.
Next, a thermosetting adhesive (CZA0525 manufactured by Arisawa Manufacturing Co., Ltd.) having a thickness of 25 μm on one side of a polyimide resin film (Apical NPI, manufactured by Kaneka Chemical Co., Ltd., thickness: 12.5 μm) is formed on the wiring pattern corresponding to the flexible part. ) To form a surface coating layer to obtain a first substrate.

2. Manufacture of second substrate (inner layer circuit board) Single area layer board (Sumitomo Bakelite) provided with copper foil (thickness 12 μm) on one side of base material (thickness 55 μm) made of an insulating material obtained by curing cyanate resin The copper foil of Sumilite LαZ CLBu) was etched to form a conductor pad for receiving the wiring pattern and the conductor post of the outer circuit board.
Next, a substrate opening having a diameter of 100 μm was formed from the surface on the substrate side by a UV laser, and desmearing with an aqueous potassium permanganate solution was performed. Electrolytic copper plating is applied to the opening of the base material to form a copper post having a height of 10 μm from the surface of the base material on the opposite side with the copper foil, and then solder plating (tin-2.5 silver) is formed at a thickness of 10 μm. To form a conductor post.
Next, a thermosetting adhesive sheet with a flux function (DBF manufactured by Sumitomo Bakelite, interlayer adhesive sheet, thickness 30 μm) was laminated by vacuum lamination so as to cover the conductor post, thereby obtaining a second substrate.

3. Manufacture of third substrate (outer circuit board) Single area layer board (Sumitomo Bakelite) provided with copper foil (thickness 12 μm) on one side of base material (thickness 55 μm) made of insulating material obtained by curing cyanate resin A copper foil of Sumilite LαZ CLBu) was etched, a wiring pattern was formed, a liquid resist (SR9000W, manufactured by Hitachi Chemical Co., Ltd.) was printed to form a surface coating layer, and an opening was formed by exposure and development.
Next, a substrate opening having a diameter of 100 μm was formed from the surface on the substrate side by a UV laser, and desmearing with an aqueous potassium permanganate solution was performed. Electrolytic copper plating was performed in the opening of the base material to form a copper post having a height of 10 μm from the surface of the base material opposite to the copper foil. Solder plating (tin-2.5 silver) was applied to the copper post with a thickness of 15 μm to form a conductor post. And the gold plating was given as surface treatment to the surface coating layer opening part.
Next, a thermosetting adhesive sheet with a flux function (DBF manufactured by Sumitomo Bakelite, interlayer adhesive sheet, thickness 25 μm) was laminated by vacuum lamination so as to cover the conductor post, to obtain a third substrate.

4.6 Manufacture of Flexible Wiring Board with Six Layers A second substrate is laminated on exposed portions (portions where no coating layer is provided) on the upper and lower surfaces of the first substrate, and the first substrate, the second substrate, A third substrate was laminated adjacent to the second circuit board so as to cover the boundary. Thereafter, partial bonding was performed for partial positioning at a spot heater at 250 ° C. Here, the third substrate protruded 1.0 mm from the boundary portion toward the coating layer side of the first substrate.
Next, heating and pressing were performed at 150 ° C. and 0.5 MPa for 60 seconds with a vacuum press, and the conductor post was molded until it contacted the conductor pad, and the circuit of the first substrate with the conductor pad was molded and embedded. Then, it is pressed at 260 ° C. and 0.01 MPa for 60 seconds with a hydraulic press, and the conductor post is soldered between the conductor pad of the second substrate and the conductor pad of the first substrate via the adhesive layer with a flux function. The layers were joined to form a solder joint and a solder fillet to join the layers. Furthermore, in order to harden the adhesive agent with a flux function, it heated at 180 degreeC and 60 minutes, and obtained the flexible wiring board of 6 layers.

(Example 2)
Example 3 was the same as Example 1 except that the third substrate protruded 0.3 mm from the boundary between the coating layer of the first substrate and the second substrate.

(Comparative Example 1)
Example 3 was the same as Example 1 except that the third substrate was laminated without protruding from the boundary portion between the coating layer of the first substrate and the second substrate.

The following evaluation was performed about the 6-layer flexible wiring board obtained by each Example and the comparative example. The evaluation items are shown together with the contents. The obtained results are shown in Table 1.
1. Thickness variation The variation in the thickness of the flexible wiring board was evaluated with a surface roughness meter. Each code is as follows.
◎: Thickness variation less than 3 μm ○: Thickness variation 3 to less than 10 μm Δ: Thickness variation 10 to less than 20 μm ×: Thickness variation 20 μm or more

2. Interlayer delamination Interlayer delamination was observed with a microscope to evaluate the presence or absence of delamination.

3. Flexibility Flexibility was evaluated with an open / close testing machine for hinge evaluation. Each code is as follows.
○: No increase in resistance and disconnection even after 50,000 times or more ×: Increase in resistance and disconnection after less than 50,000 times

4). Connection reliability Connection reliability was evaluated by conducting a continuity check with a tester after performing a temperature cycle test (hot oil 260 ° C., immersion for 5 seconds and immersion for 20 seconds at room temperature oil 100 times).

As is clear from Table 1, Examples 1 and 2 had small thickness variations and no delamination between layers.
In addition, Examples 1 and 2 were excellent in flexibility and connection reliability.
In addition, in the six-layer flexible wiring board obtained in Examples 1 and 2, the interlayer connection portion was securely soldered and a solder fillet was formed.

  The present invention can be used for a printed wiring board, a flexible printed wiring board, a multilayer flexible printed wiring board, and the like, and in particular, a multilayer flexible printed wiring board used as a component of an electronic device, a printed wiring board constituting them, and those It is used suitably for the manufacturing method.

It is sectional drawing for demonstrating the manufacturing method of a 3rd board | substrate. It is sectional drawing for demonstrating the manufacturing method of a 2nd board | substrate. It is sectional drawing for demonstrating the manufacturing method of a 1st board | substrate. It is sectional drawing for demonstrating the manufacturing method of a 6-layer flexible wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Base material 110 Single area layer board 111 Base material opening part 12 Copper foil 121 Wiring pattern 13 Surface coating layer 131 Surface coating layer opening part 132 Surface treatment layer 14 Conductor post 141 Copper post 142 Covering layer 15 Adhesive with a flux function 100 Outer layer circuit Substrate 21 Base material 210 Single area layer plate 211 Base material opening 22 Copper foil 221 Wiring pattern 222 Conductor pad 23 Surface coating layer 231 Surface coating layer opening 232 Surface treatment 24 Conductor post 241 Copper post 242 Coating layer 25 Adhesive with flux function DESCRIPTION OF SYMBOLS 200 Inner layer circuit board 31 Resin film 32 Copper foil 310 Double-sided board 321 Wiring pattern 322 Conductor pad 33 Through hole 34 Covering layer 35 Covering part 36 Exposed part 300 Circuit board 50 Boundary part 400 Six-layer flexible wiring board 401 Flexible part 02 rigid portion

Claims (6)

A first substrate having a first conductor circuit and a covering layer covering a part of the first conductor circuit;
A second substrate adjacent to a portion of the first substrate not covered by the coating layer;
A multilayer substrate having a third substrate adjacent to the second substrate,
An end portion of the third substrate protrudes beyond the boundary portion between the coating layer and the second substrate toward the coating layer side.   2. The multilayer substrate according to claim 1, wherein a length of the protruding portion is 0.3 mm or more from the boundary portion to the coating layer side.   The multilayer substrate according to claim 1, wherein the coating layer has a thickness of 15 to 60 μm.   The multilayer substrate according to claim 1, wherein the coating layer has a resin film and an adhesive layer.   The multilayer substrate according to claim 1, wherein the first substrate has flexibility. A first step of covering a part of the first conductor circuit of the first substrate having the first conductor circuit with a coating layer;
A second step of laminating a second substrate adjacent to a portion of the first substrate that is not covered with the covering layer;
And a third step of stacking a third substrate adjacent to the second substrate.
In the third step, the end portion of the third substrate protrudes toward the coating layer beyond the boundary between the coating layer and the second substrate and is laminated. Production method.

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