JP4277723B2 - Multilayer circuit board and method for manufacturing multilayer circuit board - Google Patents

Description

  The present invention relates to a multilayer circuit board used as a component of an electronic device and a method for manufacturing the multilayer circuit board.

  With the recent increase in the density of electronic devices, the circuit board used for this has become multi-layered, and a flexible circuit board having a multi-layer structure is often used. This circuit board is a rigid flex circuit board that is a composite board of a flexible circuit board and a rigid circuit board, and its application is expanding.

  A conventional method for connecting layers between a multilayer flexible circuit board and a rigid flex circuit board is similar to an interlayer connection method for multilayer rigid circuit 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 has 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 a problem in mounting components. It has come to occur.

  Against this background, in recent years, a multilayer rigid circuit board has adopted a build-up method as a new lamination technique. The build-up method is a method in which interlayer connection is made between single layers while stacking an insulating layer and a conductor composed only of a resin. 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.

  The build-up method is broadly classified into a method of connecting an interlayer after forming a via in an insulating layer and a method of stacking an insulating layer after forming an interlayer connection. The interlayer connection portion is divided into a case where the via hole is formed by plating and a case where the via hole is formed using a conductive paste or the like, and is further subdivided depending on the insulating material and via forming method used.

  Among them, a method of forming a fine via for interlayer connection in an insulating layer with a laser, filling a via hole with a conductive adhesive such as copper paste, and obtaining a more electrical connection of this conductive adhesive (for example, Patent Documents) In 1), since a stacked via that forms a via on the via is possible, not only high density but also wiring design can be simplified. However, in this method, since the electrical connection between the layers is performed with a conductive adhesive, the reliability is not sufficient. In addition, advanced technology for embedding a conductive adhesive in a fine via is also required, and it is difficult to cope with further miniaturization.

  In addition, there is a method in which a protrusion made of metal is formed on a conductor circuit, the protrusion penetrates through an insulating layer by lamination, and contacts with a conductor circuit of a layer adjacent in the thickness direction to make an interlayer connection (for example, a patent) Reference 2). However, in this method, the interlayer connection is only a physical contact, there is no means for maintaining the contact, and the reliability against expansion of the material due to heat is low.

  In addition, multilayer flexible circuit boards use thermosetting adhesives for interlaminar bonding, but with conventional technology, the post part simply removes the adhesive and reaches the connection pads for connection, etc. However, it is difficult to completely remove the adhesive between the connection post and the pad, and the reliability is low.

  Therefore, as a measure for improving reliability, a solder layer having a melting temperature higher than the curing temperature of the insulating resin is formed on the metal protrusion, and the uncured insulating layer is formed at a temperature lower than the solder melting temperature by lamination. There is also a method in which a solder joint is formed by penetrating through the metal, pressing the metal protrusions to cure the adhesive, and further melting and cooling the solder layer (for example, Patent Document 4).

However, since the adhesive has already been cured before the solder is melted, the adhesive between the solder layer at the tip of the protrusion and the conductor circuit layer cannot be eliminated by curing, impeding solder joints, machines such as presses, etc. The in-plane pressure distribution is non-uniform with a typical pressurizing mechanism, making it difficult to make reliable interlayer connections, and the appearance of the adhesive deteriorates when pressure is applied at high temperatures during bonding Is a problem.
JP-A-8-316598 JP-A-8-125344 JP 11-54934 A JP-A-8-195560

  In order to solve the above problems, the present invention can provide reliable interlayer connection, and can be laminated at a low temperature and low pressure, and can be prevented from seeping out adhesive and the like by interlayer connection under an extremely low pressure of atmospheric pressure. The present invention provides a method for manufacturing a circuit board that provides an appearance.

Such an object is achieved by the present invention described in the following (1) to ( 7 ).
(1) A first circuit board having at least one conductor pad and a second circuit board having a conductor post covered with at least one metal coating layer are laminated in a vacuum via an interlayer adhesive. The temperature is 40 ° C. or more and the melting point of the metal coating layer, the viscosity of the interlayer adhesive is 20 Pa · s or more and 500 Pa · s or less, and the pressure in the first step is 0.01 MPa or more and 1. a first step is 0MPa less, the heating temperature of the metal coating layer is melted and laminated, the temperature is less 300 ° C. above the melting point of the metal coating layer, the viscosity is 10 Pa · s of the interlayer adhesive More than 400 Pa · s, further, a second step in which the pressure of the process is substantially no pressure, and a third step of laminating at a temperature at which the interlayer adhesive is cured after the second step. It is characterized by including Method of manufacturing a multilayer circuit board.
( 2 ) The method for manufacturing a multilayer circuit board according to (1), wherein the conductor post is made of copper.
( 3 ) The method for producing a multilayer circuit board according to (1) or ( 2 ), wherein the conductor post protrudes from 2 μm to 50 μm from the surface of the insulating base material constituting the second circuit board. .
( 4 ) The method for producing a multilayer circuit board according to any one of (1) to ( 3 ), 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.
( 5 ) The method for producing a multilayer circuit board according to any one of (1) to ( 4 ), wherein a copper residual ratio of the first circuit board is not less than 30% and not more than 70%.
( 6 ) The interlayer adhesive has a flux function, and the thickness of the adhesive is obtained by adding the value obtained by dividing the volume of the circuit gap portion of the first circuit board by the area of the laminated portion and the height of the conductor post. The method for producing a multilayer circuit board according to any one of the above (1) to ( 5 ), wherein the combined value is in a range of a standard value ± 15 μm.
( 7 ) A multilayer circuit board obtained by the method according to any one of (1) to ( 6 ) above.

  According to the present invention, the solder post or the metal pad is heated by heating at a temperature higher than the melting point of the solder of the conductor post or the low melting point metal at the time of interlayer connection through the adhesive with the flux function between the conductor post and the conductor pad. A solder fillet or metal fillet is formed, and a highly reliable interlayer connection can be made, and the pressure at the time of interlayer connection is substantially no pressure only at atmospheric pressure, and the pressure distribution is uniform, resulting in poor connection Therefore, it is possible to suppress bleeding and to use this technique to obtain a highly reliable multilayer circuit board having no appearance abnormality.

  Hereinafter, although an embodiment of the present invention is described based on a drawing, the present invention is not limited to this at all.

  An example of a four-layer flexible circuit board will be described as a method for producing a multilayer circuit board of the present invention. 1-3 is a figure explaining the example of the connection method of the multilayer flexible circuit board which is embodiment of this invention, FIG.3 (c) is the present invention which has the multilayer part 320 and the flexible part 330 together. It is sectional drawing which shows the connection structure of the four-layer flexible circuit board 340 obtained.

As Step A (FIG. 1), a single-sided outer layer circuit board 130 having conductor posts 106 to be a second circuit board is formed. Subsequently, as step B (FIG. 2), an inner layer circuit board 220 having conductor pads 204 to be a first circuit board is formed. Finally, as Step C (FIG. 3), the conductor pads 204 of the inner layer circuit board 220 and the conductor posts 106 of the single-sided outer layer circuit board 130 are formed by the function of the adhesive layer 110 with a flux function. Form metal bonds and make electrical connections. As described above, it can be divided into three steps. In the case of a flexible circuit board of 6 layers or 8 layers or more, it is possible to prepare a single-sided outer layer circuit board by a process similar to Step A according to the number of layers, and repeat Step C. The order of steps A and B is not particularly limited. For example, the order of steps A and B can be performed, and then step C can be performed. Hereinafter, each step will be described.
(1) Step A
In Step A, an outer layer circuit board 130, which is a second circuit board, is manufactured (see FIG. 1). First, a single area layer plate 120 having a copper foil 101 attached to one side of a support 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, between the support substrate and the copper foil, in order to prevent the occurrence of smear that hinders the conductor connection, it is preferable that there is no adhesive layer for bonding the copper foil and the support substrate, It may be bonded using an adhesive.

  The support base material opening 103 is formed from the lower surface of the support base material 102 until the copper foil 101 is exposed (FIG. 1B).

  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 and smear remaining in the supporting substrate opening 103 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.

  A copper post 104 is formed as a protruding terminal in the support base opening 103 (FIG. 1C). One end of the copper post 104 is electrically connected to the copper foil 101, and the other end is formed so as to protrude a predetermined length from the lower surface of the support substrate 103 in the figure. Further, a metal covering layer 105 is formed on the protruding portion of the copper post 104 to cover the protruding portion (FIG. 1E). The copper post 104 and the metal coating layer 105 form a conductor post 106.

  The method for forming the conductor post 106 is not particularly limited. For example, after forming the copper post by a paste or a plating method (FIG. 1C), the metal post is covered. Examples of the metal forming the metal coating layer 106 include an alloy containing at least one kind of tin, lead, silver, zinc, bismuth, antimony, copper, and the like. In this case, the alloy is preferably a brazing material mainly composed of two or more of the above metals, for example, tin-lead, tin-silver, tin-zinc, tin-bismuth, tin-antimony. , Tin-silver-bismuth, tin-copper and the like. It is not limited to the metal combination and composition of the solder, and an optimal one may be selected.

  The height of the copper post 104 from the side surface of the support substrate 102 where the conductor circuit 107 is not present is preferably 2 μm or more and 50 μm or less, more preferably 5 μm or more and 25 μm or less. The thickness of the metal coating layer 105 is preferably 3 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less.

  Next, a desired conductor circuit 107 is formed by etching the copper foil 101 bonded to one side of the support base material 102 (FIG. 1 (e)).

  Next, an adhesive layer 110 with a flux function is formed on the surface of the support substrate 102 from which the conductor post 106 protrudes (FIG. 1 (f)). The adhesive layer with a flux function may be applied to the support base material 102 by a printing method, but a method of laminating the sheet-like adhesive on the support base material 102 is simple. The thickness of the interlayer adhesive with a flux function is preferably based on a value obtained by dividing the volume of the circuit space portion 207 of the circuit board having a conductor pad by the area of the laminated portion and the height of the conductor post, The reference value is within ± 15 μm, and more preferably within the reference value ± 10 μm. Finally, the sheet is cut according to the size of the multilayer portion to obtain a sheet or piece of outer-layer single-sided circuit board 130 on which several outer-layer single-sided circuit boards 130 are attached (FIG. 1 (g)).

  The adhesive with a flux function used in the present invention is an adhesive having a metal surface cleaning function, for example, an oxide film removal function existing on the metal surface, or an oxide film reduction function, and is not particularly limited. As a configuration of the first preferable adhesive, a phenol novolak resin having a phenolic hydroxyl group, a cresol novolak resin, an alkylphenol novolak resin, a resole resin, a polyvinylphenol resin and the like (A), and a curing agent (B) of the resin Is included. The curing agent is not particularly limited, but includes phenol bases such as bisphenol, phenol novolac, alkylphenol novolac, biphenol, naphthol, and resorcinol, and skeletons such as aliphatic, cycloaliphatic and unsaturated aliphatic. Examples of the base include epoxidized epoxy resins and isocyanate compounds.

  The blending amount of the resin having a phenolic hydroxyl group is not particularly limited, but it 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. If it exceeds wt%, a sufficient cured product cannot be obtained, and as a result, the bonding strength and reliability may be lowered. On the other hand, the resin or compound that acts as a curing agent is not particularly limited, but 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) of the epoxy resin and a curable antioxidant (E). The curing agent having an imidazole ring is not particularly limited, but imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, Examples include 2-phenyl-4-methylimidazole and bis (2-ethyl-4-methyl-imidazole). The curable antioxidant is a compound that acts as an antioxidant and can be cured by reacting with the curing agent, and is not particularly limited, but includes a compound having a benzylidene structure, 3-hydroxy-2-naphthoic acid, pamoic acid, Examples include 2,4-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid.

  Although the compounding quantity of an epoxy resin is not specifically limited, 30 weight% or more and 99 weight% or less are preferable in all the adhesive agents, and there exists a possibility that sufficient hardened | cured material may not be obtained if it is less than 30 weight%, and is unpreferable.

  Other than the two components, although not particularly limited, a thermosetting resin such as cyanate resin, acrylic acid resin, methacrylic acid resin, or maleimide resin, or a 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 curing agent and the curable antioxidant having an imidazole ring is not particularly limited, and is not particularly limited, but is 1% by weight to 20% by weight. If less than 1% by weight, the effect of cleaning the metal surface is lowered, and the epoxy resin may not be sufficiently cured, which is not preferable. If it exceeds 10% by weight, the curing reaction proceeds rapidly and the fluidity of the adhesive layer may be inferior. The epoxy curing agent and the curable antioxidant may be used in combination, or only one component may be used alone.

The method for adjusting the adhesive is not particularly limited. For example, a method for adjusting a resin by dissolving a resin (A) having a solid phenolic hydroxyl group and a resin (B) acting as a solid curing agent in a solvent, solid phenol The resin (A) having a functional hydroxyl group is dissolved in a resin (B) that acts as a liquid curing agent, and the resin (B) that acts as a solid curing agent is a resin having a liquid phenolic hydroxyl group (B Or a curable antioxidant having a imidazole ring and acting as a curing agent for the epoxy resin in a solution obtained by dissolving the solid epoxy resin (C) in a solvent. Examples thereof include a method of dispersing or dissolving (E). 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.
(2) Step B
In Step B, an inner-layer flexible circuit board 220 to be a first circuit board is manufactured. (See Figure 2)
First, for example, a double-sided plate 210 made of a heat-resistant resin 202 and a copper foil 201, such as polyimide, which is usually used for a flexible circuit board is prepared (FIG. 2A). The double-sided plate 210 is a material for the flexible part, and it is preferable that no adhesive layer is present between the copper foil 201 and the heat-resistant resin 202 in order to improve bendability and bendability. After the front and back electrical continuity is formed in the double-sided plate 210 through the through-hole 203 (FIG. 2B), a conductor pad 204 that can receive the conductor circuit and the conductor post 106 is formed by etching (FIG. 2). (c)). The copper residual ratio is preferably 30% or more and 70% or less. When the ratio is higher than this, it is difficult to form the vacuum space 301 in the stacking process, and when the ratio is lower than this, it is difficult to perform interlayer connection simultaneously with molding in the interlayer connection process.

  Thereafter, a surface coating 206 (FIG. 2D) made of polyimide or the like is applied to a portion of the conductor circuit 205 corresponding to the flexible portion 330 to form an inner layer flexible circuit board.

Even if this inner layer flexible circuit board is cut into a sheet or a piece on which several desired inner layer flexible circuit boards are imprinted before lamination, there is no problem.
(3) Step C
In Step C, the multilayer flexible circuit board 340 is manufactured using the first to third steps. (Fig. 3 (d))
First, the single-sided outer layer circuit board 130 is laid up on the inner flexible circuit board 220 (FIG. 3A). In this case, each layer is temporarily bonded by using a method in which a positioning mark formed in advance on a conductor circuit in each layer is read and aligned by an image recognition apparatus, and a method in which alignment is performed by a positioning pin. The temporary bonding method, which is the first step, needs to be provided with a ventilation portion without being in close contact with each other in order to exhaust air between layers in the next lamination step.

  The pressure of the first step is preferably 0.01 kPa or more and 20 kPa or less, more preferably 0.01 kPa or more and 10 kPa or less. By pressing at the temperature of the first step where the interlayer adhesive 110 with a flux function is softened, the conductor post 106 is embedded to the vicinity of the conductor pad to be joined. The temperature of the first step is preferably 40 ° C. or higher and the melting point of the metal coating layer or lower. The viscosity of the interlayer adhesive is preferably 20 Pa · s or more and 500 Pa · s or less. At this time, the inner layer conductor circuit space portion 207 is not formed with an adhesive, and forms a vacuum space 301 sealed with a conductor pad, a conductor circuit, an interlayer adhesive with a flux function, and a circuit board insulating layer (FIG. 3B). )).

  The adhesive layer 110 with a flux function is softened and activated at the same time by setting the temperature in the second step, which is higher than the melting point of the metal coating layer made of solder or low melting point metal, which is the second step. Thus, the metal coating layer covering the conductor post 106 is melted, and the interlayer adhesive with a flux function is formed by flowing into the vacuum space 301 by applying pressure with substantially no pressure only at atmospheric pressure. The viscosity of the interlayer adhesive is preferably 10 Pa · s or more and 400 Pa · s or less. At the same time, since the thickness of the interlayer adhesive with a flux function decreases, the metal coating layer, which is in a molten state, comes into contact with the conductor pad 204 to perform solder bonding or metal bonding, and simultaneously form a solder fillet or metal fillet. (FIG. 3C).

  As a third step, in order to cure the adhesive with a flux function, it is heated in an oven or a vacuum dryer at a temperature higher than the temperature at which the adhesive starts a curing reaction and at which the solder or low melting point metal does not melt, and the flux Cure functional adhesive. Thereafter, a surface coating 302 is applied to the conductor circuit 107 (FIG. 3D) to obtain a multilayer flexible circuit board. The surface coating 302 includes a method of attaching an overlay film obtained by applying an adhesive to an insulating resin or printing ink directly on a supporting substrate. The surface coating 302 may be provided with a surface coating opening 303 for surface treatment such as plating. The surface of the surface coating opening 303 may also be surface-treated with the same solder, metal, alloy, gold, silver, nickel or the like.

(Example 1)
(Production of outer layer single-sided circuit board)
A single-area layer plate 120 (Sumilite LαZ CLBu manufactured by Sumitomo Bakelite Co., Ltd.) having a copper foil 101 of 12 μm thickness on a support base material 102 made of an insulating material obtained by curing an epoxy resin of 55 μm thickness from the surface on the support base material 102 side. A supporting substrate opening 103 having a diameter of 100 μm is formed by a UV laser, and desmearing with an aqueous potassium permanganate solution is performed. Electrolytic copper plating is performed in the support base material opening 103 so as to have a height of 15 μm from the surface of the insulating base on the opposite side where the copper foil is provided, and then a solder plating (tin-lead eutectic) thickness of 15 μm is applied to the conductor post. 106 is formed. Next, the copper foil 101 of the single area layer plate 120 is etched to form the conductor circuit 107. Next, a 35 μm thick thermosetting adhesive sheet with a flux function (interlayer adhesive sheet RCF manufactured by Sumitomo Bakelite) was laminated, and the adhesive layer 110 with a flux function was laminated by a vacuum laminator. Finally, the outer layer single-sided circuit board 130 was obtained by external processing to the size of the laminated portion.
(Production of inner layer flexible circuit board)
Two-layer double-sided board 210 (Mitsui Chemicals NEX23FE (25T)) having a copper foil 201 of 12 μm and a support base material 202 of polyimide film thickness of 25 μm is directly plated after drilling, and through holes 203 are formed by electrolytic copper plating. After the formation and electrical conduction between the front and back sides, the pad 204 that can receive the conductor circuit and the conductor two-layer post 105 is formed by etching. The ratio of the conductor circuit and the conductor pad to the space portion 207 was 50%. Thereafter, a surface coating 206 is formed on the conductor circuit 205 corresponding to the flexible portion 330 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 obtained the inner-layer flexible circuit board 220. FIG.
(Production of multilayer flexible circuit board)
The outer-layer single-sided circuit board 130 was laid up on the inner-layer flexible circuit board 220 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, as a first step, lamination was performed in a vacuum press at 100 ° C., 0.1 MPa for 60 seconds, and the conductor post was formed to the vicinity of the conductor pad, and at the same time, the vacuum space 301 was formed. Next, as a second step, heating is performed at 260 ° C. under atmospheric pressure in a reflow furnace, and the vacuum space 301 is embedded by the adhesive layer 110 with a flux function, so that the interlayer adhesive layer 110 with a flux function is thin. As a result, the molten solder on the surface of the conductor post 106 was brought into contact with the pad 204 of the inner layer flexible circuit board 220 to form a solder joint and a solder fillet, and the layers were joined. Thereafter, as a third step, after heating at 180 ° C. for 60 minutes to cure the adhesive, a liquid resist (SR9000W manufactured by Hitachi Chemical Co., Ltd.) is printed, and then a surface coating is applied to obtain a multilayer flexible circuit board 340. It was.

(Example 2)
A multilayer flexible board obtained in the same manner as in Example 1 except that the outer layer single-sided board 130 was 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. Circuit board.

(Example 3)
The multilayer flexible circuit board obtained by the same method as Example 1 except having changed the solder plating of the conductor post 106 of the outer layer single-sided board 130 from eutectic solder to tin-silver 3.5.

(Comparative Example 1)
The outer-layer single-sided circuit board 130 and the inner-layer flexible circuit board 220 were produced by the same method as in Example 1. Next, the outer layer single-sided circuit board 130 was laid up on the inner layer flexible circuit board 220 using a jig with a pin guide for alignment. Thereafter, partial bonding was performed for partial positioning at a spot heater at 250 ° C. Then, as a laminating process, after pressing at 260 ° C. and 0.1 MPa using a hydraulic press without using a vacuum press, heating was performed at 180 ° C. for 60 minutes to cure the adhesive, and then a liquid resist ( Hitachi Chemical SR9000W) was printed, and then a surface coating was applied to obtain a multilayer flexible circuit board 340.

  In the multilayer flexible circuit boards of Examples 1 to 3, the interlayer connection portion was securely soldered, the solder fillet was formed, and no molding failure occurred. Further, the solder exists in a thickness of 3 μm to 10 μm between the conductor post 106 and the conductor pad 204 which are interlayer connection portions.

  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 Comparative Example 1, since a hydraulic press was used, the pressure distribution was non-uniform, resulting in poor connection, and the pressure was further increased. As a result, the adhesion of the interlayer adhesive was as large as 3 mm or more, resulting in poor appearance. Furthermore, since molding and interlayer bonding were performed simultaneously, there were many voids due to molding defects, and as a result of performing a temperature cycle test, cracks were generated in the interlayer junction due to stress due to void expansion, leading to disconnection.

  In interlayer connection of multilayer circuit boards that have a structure in which circuit boards are stacked, by placing an adhesive with a flux function between the layers, the conductor two-layer post and the conductor pads are soldered or metal-bonded, and further a fillet is formed. In addition, it is possible to perform bonding with higher reliability, and it is possible to perform reliable bonding by forming by atmospheric pressure and an interlayer connection process, and further, it is possible to obtain a multilayer circuit board having a good appearance without bleeding. .

Sectional drawing for demonstrating the outer-layer single-sided circuit board of this invention, and its manufacturing method. Sectional drawing for demonstrating the inner-layer double-sided circuit board of this invention, and its manufacturing method. Sectional drawing for demonstrating the multilayer flexible circuit board of the 4 layer structure of this invention, and its manufacturing method.

Explanation of symbols

101, 201: Copper foil 102, 202: Support base material 107, 205: Conductor circuit 103: Support base material opening 104: Conductor post first layer 105: Conductor post metal coating layer 106: Conductor post 120: Single area layer plate 110 : Adhesive layer with flux function 130: Outer layer single-sided circuit board 203: Through hole 204: Pads 206 and 302: Surface coating 210: Double-sided laminated board 220: Inner layer flexible circuit board 301: Vacuum space 303: Surface coating opening 310: Lamination Cross-sectional view after the process 320: Multilayer part 330: Flexible part 340: Multilayer flexible circuit board (four layers)

Claims (7)

A first circuit board having at least one conductor pad and a second circuit board having a conductor post covered with at least one metal coating layer are laminated in a vacuum via an interlayer adhesive, and the temperature is increased. 40 ° C. or more and the melting point of the metal coating layer, the interlayer adhesive has a viscosity of 20 Pa · s or more and 500 Pa · s or less, and the pressure in the first step is 0.01 MPa or more and 1.0 MPa or less. a certain first step, heating at a temperature at which the metal coating layer is melted and laminated, the temperature is less 300 ° C. above the melting point of the metal coating layer, also 400 Pa · viscosity of the interlayer adhesive 10 Pa · s or higher s or less, and further including a second step in which the pressure of the step is substantially no pressure and a third step of laminating at a temperature at which the interlayer adhesive is cured after the second step. Characteristic multilayer Method for producing a road substrate. The method for manufacturing a multilayer circuit board according to claim 1 , wherein the conductor post is made of copper. It said conductor posts, the manufacturing method of the multilayer circuit board according to claim 1 or 2 in which projecting 2μm above 50μm or less from the surface of the insulating base material constituting the second circuit board. The method for manufacturing a multilayer circuit board according to any one of claims 1 to 3 , wherein the metal coating layer is made of solder or a low melting point metal and has a thickness of 3 µm to 30 µm. Method of manufacturing a multilayer circuit board according to any one of 4 to copper retention of the first circuit board claims 1 to 70% or less than 30%. The interlayer adhesive has a flux function, and the adhesive thickness is a value obtained by adding a value obtained by dividing the volume of the circuit gap portion of the first circuit board by the area of the laminated portion and the height of the conductor post. was a reference, a method for manufacturing a multilayer circuit board according to any one of claims 1 to 5, characterized in that the range of the reference value ± 15 [mu] m. It claims 1 to multilayer circuit board obtained by any of the preparation of 6.

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