JP2005183944A - Multi-layer substrate and manufacturing method of multi-layer substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin multi-layer substrate capable of establishing highly reliable interlayer connection and a manufacturing method of the multi-layer substrate. <P>SOLUTION: The multi-layer substrate is constituted by superposing a first substrate having a first conductive circuit and a covering layer that partially covers the first conductive circuit, and a second substrate having a second conductive circuit at an area that is not covered with the covering layer of the first substrate. The side of the second substrate adjoins the side of the covering layer, in addition, the first substrate is flexible, in addition, the second substrate is of a flexible substrate, and further, the covering layer comprises a resin film and an adhesive. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  Along with the recent increase in the density of electronic devices, the multilayered printed wiring board is being used, and a flexible printed wiring board having a multilayer structure is often used. This printed wiring board is a rigid flex printed wiring board that is a composite substrate of a flexible printed wiring board and a rigid printed wiring board, and its application is expanding.

  A conventional interlayer connection method for multilayer flexible printed wiring boards and rigid flex printed wiring boards is similar to an interlayer connection method for multilayer rigid wiring boards. That is, a method of forming a laminated board in which a plurality of patterned copper foils and insulating layers are alternately stacked, forming a through hole for interlayer connection in the laminated board, and performing interlayer connection plating on the through hole to connect the interlayer Was the mainstream. However, further downsizing and higher density of mounted components have progressed, and the conventional technology that opens connection lands and through holes in each layer in the same place through all layers has insufficient wiring density, and there is also a problem in mounting components. It has come to occur.

  Against this background, in recent years, a multilayer rigid wiring board has adopted a build-up method as a new lamination technique. The build-up method is a method in which an interlayer connection is made between single layers while stacking an insulating layer composed of only a resin and a conductor. Interlayer connection methods include a wide variety of methods such as laser method, plasma method, photo method, etc., instead of conventional drilling, and high density is achieved by freely arranging small diameter via holes.

As one of the build-up methods, there is a method of laminating each substrate on which interlayer connection bumps and the like are formed using a thermosetting interlayer adhesive or the like. In rigid flex printed wiring boards, the circuit board is generally formed on both sides or on one side, and the conductor circuit is generally covered with a coating layer except for the connection of mounted parts and connections to other boards. A printed wiring board or a flexible printed wiring board whose entire surface is covered with a coating layer is used. In the rigid portion, a plurality of circuit boards are stacked. (For example, Patent Document 1)
However, since the core substrate is a flexible printed wiring board covered with a coating layer, the problem is that the final substrate thickness is increased, and when connecting the layers, the conductor post is not enlarged due to the thickness of the coating layer. Therefore, there is a problem that it is difficult to perform interlayer connection stably and inferior in connection reliability. (For example, Patent Document 2)
In addition, when a coating layer is partially provided, a portion that is covered with a coating layer and a portion that is not covered are mixed in the laminated portion, resulting in a step at these boundary portions, resulting in variations in surface thickness. There was a problem that would increase.
JP-A-8-125344 JP 11-54934 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a thin multilayer substrate capable of highly reliable interlayer connection and a method for manufacturing the multilayer substrate.

  According to the present invention, a first substrate having a first conductor circuit and a coating layer covering a part of the first conductor circuit, and the first substrate is covered with the coating layer of the first substrate. A multilayer substrate in which a second substrate having a second conductor circuit is arranged in an overlapping manner on a portion that is not present, and the side portion of the covering layer and the side portion of the second substrate are adjacent to each other A multilayer substrate is provided.

  In the multilayer substrate according to the present invention, since the first substrate in the portion where the second substrate is stacked and stacked is not covered with the coating layer, the connection reliability between the layers is reduced while reducing the thickness of the substrate. Can be improved.

  The first substrate may be a flexible substrate. Further, the second substrate may be a flexible substrate. Furthermore, the said coating layer may consist of a resin film and an adhesive agent.

  According to the invention, the first step of covering a part of the first conductor circuit of the first substrate having the first conductor circuit with the coating layer, and the coating layer of the first substrate A second step of stacking and stacking a second substrate having a second conductor circuit on a portion that is not covered, and a method for producing a multilayer substrate, wherein in the second step, There is provided a method for producing a multilayer substrate, characterized in that a side portion of a covering layer and a side portion of the second substrate are disposed adjacent to each other.

  According to the manufacturing method described above, a multilayer substrate with high connection reliability can be manufactured while reducing the thickness of the substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a thin multilayer substrate which can perform highly reliable interlayer connection, and a multilayer substrate can be provided.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 4B is a diagram illustrating a schematic configuration of a six-layer multilayer substrate 410 according to the present embodiment.

  The multilayer substrate 410 includes a flexible part 430 and a rigid part 420. The first substrate 320 is covered with a coating layer 306 leaving a part. The second substrate 220 is disposed so as to overlap the portion of the first substrate 320 that is not covered with the coating layer 306, and the side portion of the coating layer 306 and the side portion of the second substrate 220 are adjacent to each other. Yes.

  The first substrate 320 and the second substrate 220 may be flexible substrates. Further, the coating layer 306 may be made of a resin film 3061 and an adhesive 3062.

  Hereafter, each part which comprises the multilayer substrate 410 is demonstrated in detail.

  The first substrate 310 includes first conductor circuits 304 and 305, a covering layer 306, and a first base material 302. Examples of the material constituting the first base material 302 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.

  Although the thickness of the 1st base material 302 is not specifically limited, 5-50 micrometers is preferable and 12.5-25 micrometers is especially preferable. When the thickness is within this range, the flexibility is particularly excellent.

  The first conductor circuits 304 and 305 are covered with a coating layer 306 while leaving a part of the surface. The covering layer 306 may be a cover lay film composed of a resin film 3061 and an adhesive material 3062, or a liquid resin composition containing a thermosetting resin may be formed by screen printing or the like and cured by heating. It is preferable to use a coverlay film from the viewpoint of bending characteristics.

  The second substrate 210 is composed of a conductor post 208 and an interlayer adhesive 209 for electrically connecting the second conductor circuit 204, the second second base material 202, and the first substrate 320. . Examples of the material constituting the second substrate 202 include a resin film substrate. 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. Further, the second base material 202 may be obtained by impregnating a resin into a glass cloth or a glass cloth.

  Next, an example of a method for manufacturing the multilayer substrate 410 according to the present embodiment will be described. In this example, the following four steps A, B, C, and D are executed in this order.

As Step A (FIG. 1), the outer layer single-sided wiring board 120 is formed. Subsequently, in Step B (FIG. 2), the second circuit board 220 is formed. Finally, in step C (FIG. 3), the first substrate 320 is formed. In step D, the outer-layer single-sided wiring board 120 and the second circuit board 220 are laminated on the first circuit board 320 to form a multilayer board 410. As described above, it can be divided into four steps.
[Step A]
In Step A, the outer layer single-sided wiring board 120 is manufactured. As a manufacturing method, a single area layer plate 110 having a copper foil 101 attached to one side of a base material 102 made of an insulating material obtained by curing a resin such as polyimide resin or epoxy resin is prepared (FIG. 1A). At this time, it is preferable that there is no adhesive layer for bonding the copper foil and the base material between the base material and the copper foil in order to prevent the occurrence of smear that hinders the conductor connection. It may be pasted using. A wiring pattern 103 is formed by etching the copper foil 101 on one side of the substrate 102 (FIG. 1B), and a coating layer 104 is applied to the wiring pattern (FIG. 1C). The coating layer 104 includes a method of attaching an overlay film obtained by applying an adhesive to the film, or printing ink directly on a substrate. The covering layer 104 may be provided with a surface covering opening 105 for surface treatment such as plating. Next, the base material opening 106 is formed from the surface on the base material 102 side until the wiring pattern 103 is exposed (FIG. 1D).

  At this time, if a laser method is used, the opening can be easily formed and a small diameter can be opened. Further, it is preferable to remove the resin remaining in the substrate opening 106 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 111 is formed in the substrate opening 106 until it protrudes from the surface of the substrate 102 (FIG. 1 (f)).

  As a method for forming the conductor post 111, the copper post 108 is formed by a paste or plating method (FIG. 1E), and then covered with a metal or an alloy. The height of the copper post is 2 μm or more and 30 μm or less, preferably 5 μm or more and 20 μm or less from the substrate surface. 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 2 μm or more, preferably 5 μm or more and 20 μm or less. At the same time, a surface treatment 109 may be applied to the surface of the surface coating opening 105 with the same solder, metal, or alloy as described above (FIG. 1F). Further, an adhesive 112 with a flux function (FIG. 1 (g)) layer is formed on the multilayer laminated portion. This adhesive layer with a flux function includes a method of applying an adhesive with a flux function to the substrate 102 by a printing method, etc., but it may be formed by a method of laminating a sheet-like adhesive on the substrate 102. . Finally, the outer layer single-sided wiring board 120 is obtained by cutting according to the size of the multilayer portion (FIG. 1 (g)).

  The outer layer single-sided wiring board 120 is manufactured by forming the substrate openings 106 in the single-area layer board 110, forming the conductor posts 111, then forming the wiring patterns 103, and applying the surface coating 104 to the wiring patterns. May be.

  The adhesive 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 preferred adhesive. 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. And epoxy resins and isocyanate compounds.

  The blending amount of the resin having a phenolic hydroxyl group is preferably 20% by weight to 80% by weight in the total adhesive, and if it is less than 20% by weight, the effect of cleaning the metal surface is lowered, and if it exceeds 80% by weight. A sufficient cured product cannot be obtained, and as a result, bonding strength and reliability may be lowered, which is not preferable. On the other hand, the resin or compound acting as a curing agent is preferably 20% by weight to 80% by weight in the total adhesive. You may add a coloring agent, an inorganic filler, various coupling agents, a solvent, etc. to an adhesive agent as needed.

  The second preferred adhesive composition includes bisphenol-based, phenol novolak-based, alkylphenol novolak-based, biphenol-based, naphthol-based, resorcinol-based phenol bases, and skeletons such as aliphatic, cycloaliphatic and unsaturated aliphatic. An epoxy resin (C) epoxidized based on the above, 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.

The blending amount of the epoxy resin is preferably 30% by weight to 99% by weight in the total adhesive, and if it is less than 30%, a sufficient cured product may not be obtained.
In addition to the above two components, a thermosetting resin such as cyanate resin, acrylic acid resin, methacrylic acid resin, maleimide resin, or thermoplastic resin may be blended. Moreover, you may add a coloring agent, an inorganic filler, various coupling agents, a solvent, etc. as needed.
The blending amount of the epoxy resin that has an imidazole ring and is a curing agent for the epoxy resin is preferably 1% by weight to 10% by weight, preferably less than 1% by weight, based on the total adhesive. This is not preferable because the epoxy resin may not be sufficiently cured. If it exceeds 10% by weight, the curing reaction proceeds rapidly and the fluidity of the adhesive layer may be inferior.

The method for adjusting the adhesive is, for example, a method in which a resin (A) having a solid phenolic hydroxyl group and a resin (B) acting as a solid curing agent are dissolved in a solvent, a resin having a solid phenolic hydroxyl group A method in which (A) is dissolved and adjusted in a resin (B) that acts as a liquid curing agent, and a resin (B) that acts as a solid curing agent is dissolved in a resin (B) having a liquid phenolic hydroxyl group. Examples thereof include a method of adjusting, and a method of dispersing or dissolving a compound (D) having an imidazole ring and acting as a curing agent for an epoxy resin in a solution obtained by dissolving a solid epoxy resin (C) in a solvent. Examples of the solvent to be used include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, toluene, butyl cersable, ethyl cello soluble, N-methylpyrrolidone, and γ-butyl lactone. A solvent having a boiling point of 200 ° C. or lower is preferable.
[Step B]
In Step B, the second substrate 220 is manufactured. As a method of processing the second substrate 220, a single area layer plate 210 having a copper foil 201 attached to one surface of a second base material 202 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, it is preferable that there is no adhesive layer for bonding the copper foil and the base material between the base material and the copper foil in order to prevent the occurrence of smear that hinders the conductor connection. There is no problem even if they are pasted together. The copper foil 201 on one side of the second substrate 202 is etched to form a pad 204 that can receive the wiring pattern 203 and the conductor post 111 (FIG. 2B). Next, the base material opening 205 is formed from the surface on the second base material 202 side until the wiring pattern 203 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 substrate opening 205 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 double-layer post 208 is formed in the substrate opening 205 until it protrudes from the surface of the second substrate 202 (FIG. 2E). As a method for forming the conductor two-layer post 208, a copper post 206 is formed by a paste or plating method (FIG. 2D) and covered with a metal or an alloy (FIG. 2E). The height of the copper post is 2 μm or more and 30 μm or less, preferably 5 μm or more and 20 μm or less from the substrate surface. 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 may be 2 μm or more, preferably 5 μm or more and 20 μm or less (FIG. 2 (e)). If it is less than 2 μm, the reliability of connection between layers may be lowered.

  Next, an adhesive 209 with a flux function (FIG. 2 (f)) layer is formed on the multilayer laminated portion. This adhesive layer with a flux function includes a method of applying an adhesive with a flux function to the second substrate 202 by a printing method, etc., and a method of laminating the sheet-like adhesive on the second substrate 202 May be formed.

  The second substrate 220 is manufactured by forming the conductor two-layer post 208 after forming the base material opening 205 in the single-area layer plate 210, and then forming the wiring pattern 203 and the pad 204 that receives the conductor post. May be.

Further, before lamination, the second substrate 220 is cut into individual pieces or a plurality of patterns of sheets, and the outer shape is processed so that the surface coating 306 of the first substrate 320 and the second substrate 220 do not overlap at that time. To do. The second substrate 220 is obtained by these manufacturing methods (FIG. 2 (f)).
[Step C]
In Step C, the first substrate 320 is manufactured. As a manufacturing method, a double-sided board 310 made of a first base 302 and a copper foil 301, such as polyimide, usually used for a flexible wiring board is prepared (FIG. 3A). The double-sided plate 310 is a material for the flexible part, and it is preferable that no adhesive layer is present between the copper foil 301 and the first base material 302 in order to improve bendability and bendability. Absent. After the front and back electrical continuity is formed in the double-sided plate 310 through the through-hole 303 (FIG. 3B), a pad 305 that can receive the first conductor circuit 304 and the conductor post 208 is formed by etching. (FIG. 3 (c)). Next, a coating layer 306 made of polyimide or the like is applied to the first conductor circuit 304 corresponding to the flexible portion 430, and the first substrate 320 is obtained by these manufacturing methods (FIG. 3D).
Further, there is no problem even if the first substrate 320 is cut into individual pieces or a plurality of patterns of sheets before lamination.
[Step D]
In Step D, the multilayer substrate 410 is manufactured (FIG. 4B). First, the second substrate 220 is laid up (laminated) on the first substrate 320 of the center layer, and the single-sided circuit board 120 that is the outermost layer is laid up on the outer side (FIG. 4A).

  Next, the stacked first substrate 320, second substrate 220, and single-sided circuit board 120 are stacked and integrated. Such multilayering is performed while thermocompression bonding, that is, pressure bonding under heating. The method (thermocompression method) is not particularly limited, and may be subjected to thermocompression bonding each time the individual pieces of the first substrate 320 serving as the center layer are laid up, or all the single-sided circuit boards 120 of the outer layer. After laying up, thermocompression bonding may be performed at once. Also, during the temporary bonding of the layup, by applying heat at a temperature exceeding the melting point of the solder, the solder of the pad portion connected to the conductor post is melted and joined, and then heated to a temperature below the melting point. It is also possible to cure, laminate and integrate the adhesive of the adhesive layer between the layers. In this way, the second substrate 220 is superimposed on both surfaces of the first substrate 320, and the multilayer substrate 410 in which the outer-layer single-sided circuit substrate 120 is superimposed on both surfaces is laminated and integrated (see FIG. 4 (b)).

  In the case of seven or more layers, a desired number of second substrates 220 may be stacked. As for the multilayer thermocompression bonding method, positioning and double-layer bumps are performed each time an outer-layer single-sided wiring board or an inner-layer printed wiring board is laid up on an individual or multiple sheets of inner-layer flexible wiring boards that become the central layer. And the pad are pressed together, then heat exceeding the melting point of the solder is applied, the metal or alloy of the two-layer post is melted and joined to the pad, and this is repeated for the desired number of layers. In addition, after laying up a single-layer wiring board or inner-layer printed wiring board of a desired number of layers and a plurality of imprinted sheets, positioning, pressing the two-layer bumps and pads one by one, and then collectively Heat exceeding the melting point of the solder may be applied to melt and join the metal or alloy of the two-layer post. In either method, the interlayer adhesive is then cured and laminated at a temperature below the melting point of the metal or alloy. In addition, by applying heat exceeding the melting point of the solder at the time of thermocompression bonding for positioning the layup, after the metal or alloy of the two-layer post is melted and joined, the interlayer adhesive is cured at a temperature below the melting point, This can be laminated repeatedly.

(Example 1)
(Production of outer layer printed wiring board)
Single-area layer board 110 (Sumilite LαZ made by Sumitomo Bakelite Co., Ltd.) with a copper foil 101 of 12 μm thickness on a base material 102 made of an insulating material obtained by curing an epoxy resin of 55 μm thickness
The copper foil 101 of CLBu) is etched, a wiring pattern 103 is formed, a liquid resist (SR9000W manufactured by Hitachi Chemical Co., Ltd.) is printed, exposed and developed to give a surface film 104, and an opening 105 is also formed. Next, a substrate opening 106 having a diameter of 100 μm is formed from the surface on the substrate 102 side by UV laser, and desmearing with an aqueous potassium permanganate solution is performed. Electrolytic copper plating is performed in the base material opening 103 so that the copper post 108 has a height of 10 μm from the surface of the insulating base on the opposite side of the copper foil, and then the solder plating 107 (tin-lead eutectic) has a thickness of 15 μm. To form the conductor post 111. Subsequently, gold plating 109 was applied to the surface coating opening 105 as a surface treatment. Next, a 25 μm thick thermosetting adhesive sheet with a flux function (interlayer adhesive sheet made by Sumitomo Bakelite) was laminated, and the adhesive layer 112 with a flux function was laminated by a vacuum laminator. Finally, an outer shape was processed to the size of the laminated portion to obtain an outer layer single-sided wiring board 120.
(Second circuit board (production of inner printed wiring board))
Etching the copper foil 201 of a single area layer plate 210 (Sumilite LαZ CLBu made by Sumitomo Bakelite) with a 12 μm thick copper foil 201 on the second base material 202 made of an insulating material obtained by curing an epoxy resin having a thickness of 55 μm, Pads 204 that receive the wiring pattern 203 and the conductor posts 111 of the outer printed wiring board 120 are formed. Next, a substrate opening 205 having a diameter of 100 μm is formed from the surface on the second substrate 202 side by a UV laser, and desmearing with an aqueous potassium permanganate solution is performed. Electrolytic copper plating is performed in the base material opening 205 to make the copper post 206 15 μm high from the surface of the insulating base on the opposite side where the copper foil is present, and then solder plating 207 (tin-lead eutectic) is 15 μm thick. The conductor post 208 is formed. Next, a thermosetting adhesive sheet with a flux function (interlayer adhesive sheet manufactured by Sumitomo Bakelite Co., Ltd.) having a thickness of 32 μm was laminated, and the adhesive layer 209 with a flux function was laminated by a vacuum laminator. Finally, the outer layer was processed so that the insulating second base material 202 did not overlap with the size of the laminated portion and the surface coating 306 of the inner layer flexible printed wiring board 320 to obtain an inner layer printed wiring board 220.
(First circuit board (production of inner layer flexible wiring board))
Two-layer double-sided board 310 (Mitsui Chemicals' NEX23FE (25T)) having a copper foil 301 of 12 μm and a base material 302 of polyimide film thickness of 25 μm is directly plated after drilling, and through-holes 303 are formed by electrolytic copper plating. After the front and back electrical continuity is formed, a pad 305 that can receive the wiring pattern and the conductor two-layer post 208 is formed by etching. Thereafter, a surface coating 306 is formed on the wiring pattern 304 corresponding to the flexible part 430 by using a thermosetting adhesive (in-house developed material) having a thickness of 25 μm on polyimide having a thickness of 12.5 μm (Apical NPI manufactured by Kaneka Chemical Industry). did. Finally, it cut | judged to the external size and the inner-layer flexible wiring board 320 was obtained.
(Production of multilayer flexible printed wiring board)
The outer layer printed wiring board 120 and the inner layer printed wiring board 220 were laid up on the upper and lower sides of the inner layer flexible wiring board 320 using a jig with a pin guide for alignment. Thereafter, partial bonding was performed for partial positioning at a spot heater at 250 ° C. Next, lamination was performed at 150 ° C. and 0.5 MPa for 60 seconds using a vacuum press, and the conductor post was molded until it contacted the conductor pad, and the circuit of the inner-layer flexible wiring board 320 with the conductor pad was molded and embedded. Next, it is pressed at 260 ° C. and 0.005 MPa for 60 seconds with a hydraulic press, and the conductor posts 111 and 208 are connected to the pads 204 of the inner printed wiring board 220 and the inner flexible wiring via the adhesive layers 112 and 209 with a flux function. Solder fusion bonding was performed with the pads 305 of the plate 320 to form solder bonding and solder fillets, and the layers were bonded. Subsequently, in order to cure the adhesive, the temperature was heated at 180 ° C. for 60 minutes to obtain a six-layer multilayer flexible wiring board 410 in which the layers were laminated.

(Example 2)
Example 1 except that the outer layer printed wiring board 120 and the inner layer printed wiring board 220 are changed to a single-sided copper-clad board (Upicel SE1310 manufactured by Ube Industries) with a 12 μm copper foil based on a polyimide with a thickness of 25 μm. A multilayer flexible wiring board obtained by the method.

(Example 3)
It is obtained in the same manner as in Example 1 except that the solder plating of the conductor post 111 of the outer printed wiring board 120 and the conductor post 208 of the inner printed wiring board 220 is changed from eutectic solder to tin-silver 3.5. Multi-layer flexible wiring board.

(Comparative Example 1)
The size of the inner layer printed wiring board 220 of Example 1 is overlapped with the surface coating 306 of the inner layer flexible printed wiring board 320 to have the same outer shape as the outer layer printed wiring board 120, and the conductor post 208 of the inner layer printed wiring board is made to have a copper post height. A multilayer flexible printed wiring board (FIG. 5) obtained by the same method as in Example 1 except that the thickness was set to 20 μm and the thickness of the interlayer adhesive with a flux function was 37 μm.

  In the multilayer flexible printed wiring boards of Examples 1 to 3, the interlayer connection portion was securely soldered and a solder fillet was formed. Furthermore, the thickness of the 6-layered product was also good with variations of 5 μm or less.

  In addition, even when the samples obtained in these examples were subjected to a temperature cycle test (100 times of hot oil 260 ° C. immersion for 5 seconds and normal temperature oil 20 seconds immersion), no disconnection failure occurred, The state was also good, the increase in conduction resistance was 5% or less, and the decrease in insulation resistance between lines was 5% or less.

  However, in the case of Comparative Example 1, a good solder joint was obtained between the conductor post and the conductor pad, but it was necessary to increase the copper post, and the man-hour for producing the inner printed wiring board was increased more than usual. Since the overall product thickness is thicker at the matching step, the variation in the overall product thickness is as large as 5 μm or more.

  In a multilayer circuit board having a structure in which circuit boards are superposed, a matching portion between a surface coating layer of an inner flexible printed wiring board that is a first circuit board and an insulating base part of an inner printed wiring board that is a second circuit board Therefore, it is possible to obtain a multilayer substrate capable of reducing the product thickness variation.

Sectional drawing for demonstrating the single-sided printed wiring board for outer layers used for this invention, and its manufacturing method. Sectional drawing for demonstrating the 2nd board | substrate used for this invention, and its manufacturing method. Sectional drawing for demonstrating the 1st board | substrate used for this invention, and its manufacturing method. Sectional drawing for demonstrating the multilayer substrate of 6 layer structure of this invention, and its manufacturing method. It is a figure explaining the problem in the conventional lamination method.

Explanation of symbols

101, 201, 301: Copper foil 102, 202, 302: Base material 103, 203, 304: Conductor circuit 104, 306: Cover layer 105: Surface coating opening 106, 205: Base material opening 107, 207: Metal coating Layers 108, 206: Copper posts 109: Surface treatment 110, 210: Single-sided copper clad laminates 111, 208: Conductor posts 112, 209: Adhesive layers with a flux function 120: Outer printed wiring boards 204, 305: Pads 220: No. Second substrate 303: Through hole 310: Double-sided copper-clad laminate 320: First substrate 410, 510: Multilayer substrate (6 layers)
420, 520: Multilayer part 430, 530: Flexible part

Claims (5)

A first conductor circuit;
A first substrate having a coating layer covering a portion of the first conductor circuit;
A portion of the first substrate not covered with the coating layer, a second substrate having a second conductor circuit;
Is a multi-layer board arranged in an overlapping manner,
A multilayer substrate, wherein a side portion of the covering layer and a side portion of the second substrate are adjacent to each other.   The multilayer substrate according to claim 1, wherein the first substrate is a flexible substrate.   The multilayer substrate according to claim 1, wherein the second substrate is a flexible substrate.   The multilayer substrate according to claim 1, wherein the coating layer is made of a resin film and an adhesive. 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 stacking and stacking a second substrate having a second conductor circuit on a portion of the first substrate not covered with the coating layer;
A method for producing a multilayer substrate comprising:
In the second step, a multilayer substrate manufacturing method is characterized in that the side portion of the covering layer and the side portion of the second substrate are adjacently stacked.

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