JP2006303338A - Multilayer circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel multilayer circuit board with at least one of its surfaces smooth and having a conductive structure between layers formed of a highly reliable columnar conductor. <P>SOLUTION: The multilayer circuit board P has an integral structure with a plurality of circuit boards laminated. At least one of its surfaces is a smooth surface with a land and a conductor circuit leveled with the surface. At least one of conductive structures connecting an upper-layer circuit board 1 with a lower-layer circuit board 2 is made of the columnar conductor 5, including a tip of a bump conductor 5<SB>1</SB>protruding from the lower surface of the upper-layer board 1 and a tip of a bump conductor 5<SB>2</SB>protruding from the upper surface of the lower-layer board 2 coupled directly or via a conductive material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer circuit board and a method for manufacturing the same, and more particularly, a novel multilayer having a smooth mounting surface for components, high-density mounting of components, and high reliability of a conductive structure between layers. The present invention relates to a circuit board and a manufacturing method thereof.

A semiconductor element package incorporated in various electronic devices such as computers, portable communication devices, and liquid crystal panels has a structure in which a predetermined semiconductor component is mounted on a circuit board and the whole is resin-molded.
Recently, electronic devices have been remarkably miniaturized, speeded up, and multi-functionalized. Corresponding to this, high-density mounting of semiconductor components is possible, and circuit boards with fine conductor circuit patterns The request to is strong.

As a circuit board that can meet such a demand, a multilayer circuit board having a structure in which a plurality of unit circuit boards are stacked is preferable.
Various methods have been proposed as a method for manufacturing this multilayer circuit board. In any case, it is necessary to form a conductive structure between the lower circuit board and the upper circuit board.
For example, an Ag paste is printed on a land portion of a lower circuit board on which a predetermined conductor circuit pattern is formed, a bump conductor having a protruding shape is formed thereon, and an upper circuit to be laminated with the lower circuit board An electrically insulating film having an adhesive layer formed on both sides is placed between the substrates, and the whole is hot-pressed to break through the film with bump conductors, and the bump conductors are connected to the upper circuit board. There is a method of forming a conduction structure between an upper layer and a lower layer by bonding to a land portion.

  As a method for manufacturing a multilayer circuit board, a build-up method is widely used. In this method, the conductor circuit of the lower circuit board and its land are embedded with an insulating layer having a predetermined thickness, and then this insulation is performed. After drilling a laser via from the surface of the layer to the surface of the conductor circuit of the lower circuit board, and forming a Cu plating layer on the inner wall of the laser via and the surface of the insulating layer by electroless plating and electroplating method, Filling the recess with an insulating material or resin material, forming a Cu plating layer on the entire surface again by electroplating, and processing this Cu plating layer into a conductor circuit of a predetermined pattern to form a desired upper circuit board Yes. In this case, a conduction structure is formed between the lower circuit board and the upper circuit board by a Cu plating layer formed on the inner wall in the via hole.

  In addition, a conductive paste may be filled in the laser via and an upper layer and a lower layer conductive structure may be formed by this conductive paste.

Recently, even in multilayer circuit boards, higher-density component mounting is required than before, and in response to this, refinement of the conductive structure between layers is required.
In relation to this requirement, in the method of breaking the film with a bump conductor to make the upper layer and the lower layer conductive, the bump-shaped bump conductor is formed by pattern printing of Ag paste, and its diameter is 200 μm. The diameter becomes relatively large, and it is not possible to sufficiently meet the demand for finer processing. Moreover, since the bump conductor must maintain a strength that can break through the film, even if the diameter can be reduced to, for example, about 50 μm, it does not always break through the film, and breaks during hot press. There is a fear, and the reliability as a conductive structure is lacking.

In the case of the build-up method described above, since the Cu plating layer on the surface of the insulating layer becomes thick, there is a problem that it is difficult to process it to form a fine conductor circuit pattern. And the conduction structure between layers formed by a method of filling a laser via with a conductive paste is limited in terms of electrical characteristics and reliability.
The present invention solves such problems, has a conductive structure that can be refined, has high reliability, and has a mounting surface suitable for component mounting, and a method of manufacturing the same. For the purpose of provision.

In order to achieve the above object, in the present invention,
In a multilayer circuit board having a structure in which a plurality of circuit boards are stacked and integrated,
At least one of the surfaces is a smooth surface in which the land portion and the conductor circuit are flush with the surface,
At least one of the conductive structures connecting the upper circuit board and the lower circuit board includes a front end portion of the bump conductor protruding from the lower surface of the upper circuit board and a front end of the bump conductor protruding from the upper surface of the lower circuit board. There is provided a multilayer circuit board characterized in that the parts are made of columnar conductors joined to each other directly or through a conductive material.

Preferably,
A single-layer or multi-layer first circuit board in which a land portion and a conductor circuit are formed flush with the upper surface on the upper surface, and a bump conductor protrudes on the lower surface;
A single-layer or multi-layer second circuit board having a land portion and a conductor circuit formed flush with the lower surface on the lower surface and a bump conductor projecting on the upper surface is bonded via an insulating substrate, There is provided a multilayer circuit board having a conductive structure of the columnar conductor formed in an insulating base material and having smooth surfaces on both sides.

In the present invention,
Produces an intermediate material in which a plurality of circuit boards are sequentially stacked on the surface of a conductive thin layer formed on one side of a smooth substrate, and bump conductors protrude in a predetermined plane pattern on the surface of the last stacked circuit board. Performing step A;
The surface on the bump conductor side of the two intermediate materials is opposed to each other through an insulating base material in which a through hole having a larger diameter than the bump conductor is formed corresponding to the planar pattern of the bump conductor on each surface,
After inserting each bump conductor into the through-hole, the whole is subjected to hot-pressing to join the two intermediate members through the insulating base material to form an integrated structure, and at the same time, the tip of the bump conductor In the through-hole; and step C in which the smooth substrate and the conductive thin layer are sequentially removed from the integrated structure;
A method for manufacturing a multilayer circuit board is provided.

In that case,
Step A is
After forming a thin conductive layer on the surface of the smooth substrate, the surface of the thin conductive layer is covered to form an insulating layer a, and the insulating layer a is exposed and developed to form a land portion and a conductive circuit. The insulating layer a in a place to be removed is removed to form a concave pattern a on which the conductive thin layer is exposed, and then the insulation is left in the concave pattern a by electroplating. A step A ₁ of filling the plating material until the surface of the layer a is flush with the surface of the layer a to form the plating filling portion a;
The insulating layer b is formed by covering the entire surface including the plating filling portion formed in the previous step, and the insulating layer b is exposed and developed to form the land portion and the conductor circuit at the location where the conductor circuit is to be formed. b is removed, and the concave pattern b exposed by the plating filling portion is formed therein, and then the surface of the insulating layer to be left in the concave pattern b is flush with the surface of the concave pattern b by electroplating. Step A _{2 in} which the plating material is filled up to form a new plating filling portion up to one time or repeated a plurality of times;
All surfaces, including the step A ₂ last plating filled portion formed in a coated form an insulating layer c, by performing exposure and development on the insulating layer c, the insulation of the portion to be formed a bump conductor The insulating layer is formed after removing a layer, forming a concave hole for a bump conductor exposed by the plating filling portion, and then filling a plating material into the concave hole for the bump conductor by electroplating. and a step C of removing bumps c and projecting bump conductors on the surface of the plating filling portion.

  In this multilayer circuit board conduction structure, the bump conductors projecting from the lower surface of the upper circuit board and the bump conductors projecting from the upper surface of the lower circuit board are hot-pressed in the through holes of the insulating base. Thus, for example, it is composed of a columnar conductor integrated by diffusion bonding, so this columnar conductor has a high coupling strength and is fixed without floating in the through hole of the insulating substrate, and has a conductive structure. As highly reliable.

  And since this multilayer circuit board can make the diameter of this bump conductor as small as 10 μm, the formed conductive structure is made fine and the surface is smooth. Higher density mounting is possible than before.

FIG. 1 shows a cross-sectional structure of an example P of the multilayer circuit board of the present invention.
In this circuit board P, the circuit board 1 located in the upper layer and the circuit board 2 located in the lower layer are joined and integrated via the insulating base material 3, and a land portion or a conductor circuit (hereinafter, summarized) of the upper circuit board 1 is joined. The conduction between 41 ₁ and the land portion of the lower circuit board 2 or the conductor circuit (hereinafter collectively referred to as a conductor circuit) 4 ₂ is formed in the insulating base 3. In addition, the structure is a column conductor 5 described later.

Since both the upper circuit board 1 and the lower circuit board 2 are circuit boards having a two-layer structure, the circuit board P has a five-layer structure as a whole including the insulating base material 3 having the columnar conductors 5. It is a multilayer circuit board.
In the case of this circuit board P, the conductor circuit formed on the surface 1a of the upper circuit board 1 and the surface 2a of the lower circuit board 2 is embedded in the insulating layer of each circuit board, and the surface and surface of the insulating layer Since each surface is exposed in one state, the surfaces 1a and 2a of the circuit boards 1 and 2 are both smooth surfaces.

In the multilayer circuit board of the present invention, both surfaces may not be smooth surfaces like the circuit board P, and one of the surfaces may not be smooth surfaces. However, in the multilayer circuit board of the present invention, one of the surfaces is a smooth surface in relation to the manufacturing process described later.
The biggest feature of the circuit board P, as shown in FIG. 1, the upper circuit and bumps conductors 5 _1, which is formed to protrude to the lower surface of the conductor circuit 4 _first substrate 1, a conductor circuit of the lower circuit board 2 4 ₂ The bump conductors 52 projecting from the upper surface of the _first and _second conductors are coupled and integrated with each other in the through holes 3a formed in the insulating base 3 to form the columnar conductors 5. That is, a conductive structure between the circuits 4 ₁ and 4 ₂ is formed.

And this columnar conductor 5 is formed in the manufacturing process mentioned later, However, Since the outer periphery of the columnar conductor 5 adheres to the inner wall of the through-hole 3a of the insulation base material 3 in the process of the hot press in the process, it is. It is firmly held by the through hole 3a without floating.
Note that both the conductor circuit (including the land portion) on the circuit board P and the bump conductor described above are usually formed of Cu.

Next, the method for manufacturing a multilayer circuit board according to the present invention will be described in detail. The case of the circuit board P shown in FIG. 1 will be described.
In the manufacturing method of the present invention, first, the process A for separately manufacturing the upper circuit board (first circuit board) 1 and the lower circuit board (second circuit board) 2 and the circuit boards 1 and 2 are insulated. It consists of a process B for forming an integrated structure by bonding via the substrate 3 and a process C for making the surface of the obtained integrated structure a smooth surface.

The above-described process A is divided into a process A ₁ for manufacturing the circuit board located on the outermost surface of the circuit board P shown in FIG. 1 and a surface (lower surface) of the circuit board manufactured in the process A _1. Are assembled in sequence A ₂ to produce a multi-layer circuit board, and A ₃ to form bump conductors protruding on the surface (lower surface) of the circuit board produced in process A _2. Yes.
First, the process A ₁ will be described.

First, as shown in FIG. 2, a smooth substrate 6 having a smooth surface, a relatively thick and rigid surface is prepared, and a conductor thin film is formed on one surface thereof by a known thin film forming method such as electroplating or sputtering. Layer 7 is deposited.
The material of the smooth substrate 6 is not limited as long as the surface is smooth, and examples thereof include a stainless steel plate and a glass plate. Moreover, as a material of a conductor thin layer, Cu and Ni can be mention | raise | lifted, for example, The thickness should just be 3-5 micrometers and the thickness which does not have a pinhole.

Then, as shown in FIG. 3, an insulating layer 8 _first predetermined thickness to cover the surface 7a of the conductor thin layer 7. Specifically, for example, it is formed by adhesion of a dry film having a predetermined thickness, printing of a liquid resist, or the like.
Note that the insulating layer 8 ₁ of thickness may be selected appropriately in relation to the design thickness of the conductor circuit or land portion to be formed.

Then, the insulating layer 8 ₁ is exposed and developed to etch away the insulating layer 8 ₁ where the conductor circuit and the land portion are to be formed, and as shown in FIG. The concave pattern 9 is exposed.
Then, electroplating is performed with the conductor thin layer 7 (or a smooth substrate if the smooth substrate is a conductive material) as a negative electrode, and the concave pattern 9 is filled with a plating material such as Cu, for example. forming a plating filling unit 10 ₁ as shown in.

In that case, the plating filling portion 10 ₁ of the surface, leaving to Dielectric 8 _first surface performs electroplating so as to flush with. The plating filling portion 10 ₁ is conductive circuit located outermost surface of the circuit board P shown in FIG.
In this way, in step A ₁ , a plated filling portion (conductor circuit) wired in a predetermined pattern is formed in the insulating layer 8 _{1 on} the surface of the thin conductor layer 7, and the insulating layer 8 ₁ An intermediate material P ₁ is manufactured in which the surface of the plating filling portion 10 ₁ is flush with the surface of the plating filling portion 10 ₁ .

Next, a description will be given of Step A _2.
In step A _2, and covers the intermediate material plated filling unit 10 ₁ also entire surface, including the P ₁ in FIG. 5 to form an insulating layer, then, as in the case of step A _1, a conductor circuit by removing the insulating layer portion that forms, there is formed a recess pattern plating filler 10 _first surface of the intermediate layer P ₁ is exposed, and then subjected to electroplating to the conductive thin layer 7 and negative pole Then, the recess pattern is filled with a plating material to form a new plating filling portion.

In this case, it is the same as in Step A ₁ of the surface of the insulating layer which is leaving the surface of the plating filling portion flush state.
As a result, as shown in FIG. 6, the intermediate member new plating filling section 10 _{2 1} a new plating filling section plating filling unit 10 are integrated in the P _1, an insulating layer 8 _first intermediate material P ₁ An intermediate material P ₂ having a new insulating layer 8 ₂ integrated with the formed insulating layer is manufactured.

Then, by performing the same process on the intermediate material P ₂ , the intermediate material P ₃ shown in FIG. 7, that is, the surface of the conductive thin layer 7, has one surface of the upper circuit board 1 in the circuit board P of FIG. An intermediate material in which the parts are integrated is manufactured.
In the next step A ₃ , bump conductors are projected from the surface of the intermediate material P ₃ .
In step A ₃ , first, as shown in FIG. 8, the insulating layer 8 ₃ is formed by adhesion of a dry film or resist printing so as to cover the entire surface including the plating filling portion 10 of the intermediate material P ₃ .

The insulating layer 8 ₃ thickness, it is preferable to slightly larger or the thickness of the same value as 1/2 value of length of the design of the columnar conductor 5 in the circuit board P of FIG.
Next, the insulating layer 8 ₃ is exposed and developed to remove the insulating layer 8 ₃ where the bump conductor is to be formed. As shown in FIG. 9, the surface 10 _a of the plated filling portion 10 is exposed. The concave hole 11 is formed. This concave hole 11 is a concave hole for forming a bump conductor there. The diameter of such a concave hole can be as small as about 10 μm.

Next, electroplating is performed with the conductor thin layer 7 as a negative electrode, and the plating material is filled in the concave holes 11 to form the plating filling portion 12 as shown in FIG.
At this time, the surface of the insulating layer 8 ₃ which is leaving the plated filling portion 12 is preferably flush state.
Then, all of which insulating layer 8 ₃ and leaving removed by etching. As a result, as shown in FIG. 11, the intermediate material P ₄ having the plating filling portion 12 protruding from the surface (lower surface) of the conductor circuit 10 is manufactured.

The intermediate material P ₄ has a structure in which the upper circuit board 1 in the circuit board P of FIG. 1 is assembled on the surface of the conductive thin layer 7, and the plating filling portion 12 is a bump conductor 5 of the upper circuit board 1. _{It is 1} . The diameter of the bump conductors 5 _1, it is possible to approximately 10μm diameter of the concave hole 11 at the minimum, it is possible to reduce the diameter of up to a minimum 10μm approximately.
Next, step B will be described.

First, as shown in FIG. 12, the two intermediate materials P ₄ and P ₄ ′ produced in the process A are placed with the insulating base 3 in the middle, and the surfaces on the side of the plating filling portion are opposed to each other. Arrange in a state.
Note that the plane of the bumps conductors 5 ₁ intermediate members P ₄ distribution patterns, the intermediate material P ₄ 'plane distribution pattern of bumps conductors 5 _2, the two intermediate members P _4, P _4' and in contact with Sometimes, each bump conductor is designed to have the same position coordinates, and is formed in the process A based on the design criteria.

Moreover, the through-hole 3a is formed in the insulating base material 3 at the coordinate position of each bump conductor. The thickness of the insulating base material 3 is equal to or slightly smaller than the total height of the bump conductors 5 ₁ and 5 ₂ formed on the intermediate materials P ₄ and P ₄ ′.
As the insulating substrate 3, for example, a prepreg material or a polyimide film can be used, and it is preferable that an adhesive layer is formed on both surfaces thereof.

Further, the diameter of the through hole 3a formed in the insulating base material 3 is not limited as long as the bump conductors 5 ₁ and 5 ₂ formed in the intermediate materials P ₄ and P ₄ ′ can be inserted. It does not have to be formed with processing accuracy.
Then, the intermediate material P ₄ and the intermediate material P ₄ ′ are overlapped via the insulating base material 3. Each bump conductor is inserted into the through hole 3a of the insulating substrate 3, or the bumps conductors 5 ₁ of the tip portion and the bump conductors 5 ₂ of the tip portion are in contact with each other, they are located opposite each other with a minute clearance It becomes a state.

At this time, since the diameter of the through hole 3a is larger than the diameter of the bump conductor, the insertion of the bump conductor into the through hole proceeds smoothly.
Then, in a state where the two intermediate materials are superposed, hot pressing is performed to integrate the two intermediate materials. The hot press is preferably performed in a vacuum. This is because the insulating base material contains a resin component, so that the gas during the thermal decomposition is removed from the adhesive surface.

The temperature at the time of hot-pressing is appropriately selected depending on the softening point of the insulating base material to be used and the bonding of the tip end portion of the bump conductor described later, but it may be about 150 to 340 ° C. The applied pressure is generally set to about 2.0 to 4.5 MPa from the viewpoint of the strength of the obtained integrated structure and the improvement of the reliability of the formed columnar conductor.
During this hot press, the insulating base material 3 is softened and deformed. The intermediate material P ₄ and the intermediate material P ₄ ′ are bonded to the surface of the insulating substrate 3 by the action of the adhesive layer on the surface.

On the other hand, the bump conductors 5 ₁ and 5 ₂ in the through-hole 3 a are in pressure contact with each other, and are mutually diffused or melted and integrated by heat and pressure to be converted into a single columnar conductor 5. The columnar conductor 5 is fixed in the through hole in close contact with the inner wall of the deformed through hole 3a.
Even when the center axis of each bump conductor is slightly deviated when the bump conductor is inserted into the through hole, the formed columnar conductor is still in contact with the inner wall of the through hole due to deformation of the insulating base material during hot press. It will adhere and be fixed in the hole.

Here, the plating material used when forming the bump conductor is usually Cu, as in the case of the conductor circuit and the land portion.
In order to increase the bonding strength of the bump conductors 5 ₁ and 5 ₂ during the hot press, diffusion or melting is caused by heat at the tip of at least one of the bump conductors of the intermediate material P ₄ and the intermediate material P ₄ ′. Preferably, the metal or alloy to be plated is thinly plated. For example, it is preferable to perform Au plating, solder plating, Sn plating, or the like.

For example, applying Au plating on the tip portion of the bump conductors 5 ₁ intermediate members P ₄ in FIG. 12, when the intermediate material P ₄ 'bump conductors 5 ₂ remains Cu, during hot pressing, between Cu and Au in occurs mutual diffusion, high binding altitude is obtained between the bump conductor 5 ₁ and the bump conductor 5 ₂ by its.
The state at the tip portion of the bump conductor idea to plating a low melting point material such as solder, Sn, where the bumps conductor 5 ₁ and the bump conductor 5 ₂ during hot pressing is not in contact with each other at the tip portion Even in this case, the low-melting-point material melted and solidified can ensure electrical coupling between the bump conductors.

This means that when the intermediate materials P ₄ and P ₄ ′ of FIG. 11 are manufactured, the height of the bump conductor to be formed can be given a degree of freedom.
When bonding the bump conductor, for example, a glass fiber-epoxy resin substrate having an adhesive layer formed on both sides, a resin film such as a polyimide film having an adhesive layer formed on both sides, or a prepreg material After forming a through hole 3a having a desired diameter in such an insulating base 3 with a drill or a laser beam, metal powder is dispersed in a resin binder like Ag paste or Cu paste in the through hole 3a. An insulating substrate filled with a conductive paste can also be used.

In this case, the height of the bump conductors 5 ₁ and 5 _{2 in} the intermediate materials P ₄ and P ₄ ′ can be reduced. This is because even if the bump conductors are not in contact with each other at the tip portions, the conductive paste is interposed between the tip portions, so that conduction is ensured and a columnar conductor is formed substantially.
When this step B is completed, as shown in FIG. 13, an intermediate material P ₅ in which the conductive thin layer 7 and the smooth substrate 6 are disposed on both surfaces is obtained.

In step C, the smooth substrate and the conductive thin layer are sequentially removed from the intermediate material P ₅ .
Specifically, the smooth substrate 6 is removed by, for example, an etching process. Next, a predetermined etching process is performed to remove the conductive thin layer 7.
As a result, the circuit board P shown in FIG. 1 is obtained. That is, both surfaces are smooth and the upper circuit board 1 and the lower circuit board 2 are integrated via an insulating base material, and the insulating base material is provided between the upper circuit board 1 and the lower circuit board 2. 3 is a multi-layer circuit board which is electrically connected by a columnar conductor 5 formed in the circuit board 3.

The above description relates to the circuit board P of FIG. 1 in which both the upper circuit board and the lower circuit board are multilayer circuit boards, but the present invention is not limited to this.
For example, as a circuit board for the upper layer (or lower layer), using an intermediate material P ₁ shown in FIG. 5, bumps conductor projecting from the intermediate material plated filling portion 10 ₁ of the surface of the P _1, a lower layer (or upper layer The same circuit board may be used.

  Also, for example, an upper layer (or lower layer) circuit board having a smooth surface is used, and a lower layer (or upper layer) circuit board having a thickness with a conductor circuit or land on the surface is used. If used, a multilayer circuit board having a smooth one side can be obtained.

  In the case of the multilayer circuit board according to the present invention, the conductive structure between the layers is formed of a solid columnar conductor fixed in the insulating layer, so that the conductive structure is highly reliable. Then, when forming the columnar conductor, at least one of the bump conductors to be bonded is subjected to Au plating, solder plating, etc., so that the bonding strength of the bump conductor is improved, and thus a more reliable conductive structure between layers. Can be.

  Further, since the diameter of the bump conductor can be reduced to a minimum of about 10 μm, the through structure between the layers becomes very fine, and as a result, various parts can be mounted at high density.

It is sectional drawing which shows one example P of the multilayer circuit board of this invention. It is sectional drawing which shows the state which formed the conductive thin layer in the single side | surface of a smooth substrate. It is sectional drawing which shows the state which coat | covered the electroconductive thin layer and formed the insulating layer. It is sectional drawing which shows the state in which the conductor circuit and the recessed part pattern for land parts were formed in the insulating layer. Plating material in the recess pattern is a sectional view showing an intermediate material P ₁ filled. Is a sectional view showing an intermediate material P _2. Is a sectional view showing an intermediate material P _3. It is a sectional view showing a state of forming an insulating layer on the surface of the intermediate member P _3. It is sectional drawing which shows the state which formed the concave hole for bump conductors in the insulating layer. It is sectional drawing which shows the state which filled the plating material in the concave hole. Is a sectional view showing an intermediate material P _4. It is a cross sectional view showing the arrangement relationship between the intermediate member P ₄ and the insulating base material intermediate member P ₄ '. Is a sectional view showing an intermediate material P _5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper-layer circuit board 1a Surface 2 of upper-layer circuit board 1 Lower-layer circuit board 2a Surface 3 of lower-layer circuit board 2 Insulating base material 3a Through-hole 4 ₁ , 4 ₂ Conductor circuit and land portion 5, 5 ₁ , 5 ₂ surface 8 ₁ of the bump conductor 6 smooth substrate 7 electrically conductive thin layer 7a insulating layer 7, 8 _2, 8 ₃ insulating layer 9 concave pattern 10, 10 _1, 10 ₂ plated filling section 11 concave hole 12 plated filling portion (bump conductor)

Claims (8)

In a multilayer circuit board having a structure in which a plurality of circuit boards are stacked and integrated,
At least one of the surfaces is a smooth surface in which the land portion and the conductor circuit are flush with the surface,
At least one of the conductive structures connecting the upper circuit board and the lower circuit board includes a front end portion of the bump conductor protruding from the lower surface of the upper circuit board and a front end of the bump conductor protruding from the upper surface of the lower circuit board. A multilayer circuit board characterized in that the portion is made of a columnar conductor joined directly or via a conductive material. A single-layer or multi-layer first circuit board in which a land portion and a conductor circuit are formed flush with the upper surface on the upper surface, and a bump conductor protrudes on the lower surface;
A land portion and a conductor circuit are formed on the lower surface in a state flush with the lower surface, and a single-layer or multilayer second circuit board on which the bump conductor protrudes is bonded to the upper surface via an insulating base material, The multilayer circuit board according to claim 1, wherein the multilayer circuit board has a conductor structure of the columnar conductor formed in the insulating base, and both surfaces are smooth surfaces. Produces an intermediate material in which a plurality of circuit boards are sequentially stacked on the surface of a conductive thin layer formed on one side of a smooth substrate, and bump conductors protrude in a predetermined plane pattern on the surface of the last stacked circuit board. Performing step A;
The surface on the bump conductor side of the two intermediate members is opposed to each other through an insulating base material in which a through hole having a larger diameter than the bump conductor is formed corresponding to the planar pattern of the bump conductor on each surface,
After inserting each bump conductor into the through-hole, the whole is subjected to a hot press process to join the two intermediate members through the insulating base material to form an integrated structure, and at the same time, the tip of the bump conductor A step B of joining the parts in the through hole; and a step C of sequentially removing the smooth substrate and the conductive thin layer from the integrated structure;
A method for producing a multilayer circuit board, comprising:   The two bump conductors of the intermediate material are both made of Cu, and at least a tip portion of the bump conductor of at least one intermediate material is plated with a metal or alloy that melts or diffuses by heat. Manufacturing method for multilayer circuit board.   The method for manufacturing a multilayer circuit board according to claim 4, wherein the metal or alloy plating is Au plating, Sn plating, or solder plating.   4. The method of manufacturing a multilayer circuit board according to claim 3, wherein the two bump conductors of the intermediate material are electrically coupled to each other through a conductive paste filled in the through hole of the insulating base.   4. The method for manufacturing a multilayer circuit board according to claim 3, wherein the hot-pressing process is a vacuum hot-pressing process. Step A is
After forming a thin conductive layer on the surface of the smooth substrate, the surface of the thin conductive layer is covered to form an insulating layer a, and the insulating layer a is exposed and developed to form a land portion and a conductive circuit. The insulating layer a in a place to be removed is removed to form a concave pattern a on which the conductive thin layer is exposed, and then the insulation is left in the concave pattern a by electroplating. Step A ₁ for filling the plating material until the surface of the layer a is flush with the surface of the layer a to form the plating filling portion a,
The insulating layer b is formed by covering the entire surface including the plated filling portion formed in the previous step, and the insulating layer b is exposed and developed to form the land portion and the conductor circuit at the location where the conductor circuit is to be formed. b is removed, and the concave pattern b exposed by the plating filling portion is formed therein, and then the surface of the insulating layer b to be left is flush with the surface of the concave pattern b by electroplating. A step A ₂ of filling the plating material until forming a new plating filling portion b until it is completed or repeating a plurality of times;
All surfaces, including the step A ₂ last plating filled portion formed in a coated form an insulating layer c, performing exposure and development on the insulating layer c, the insulation of the portion to be formed a bump conductor After removing the layer c, a bump conductor concave hole exposed by the plating filling portion is formed therein, and after filling the plating material into the bump conductor concave hole by electroplating, the insulation 4. The method of manufacturing a multilayer circuit board according to claim ₃ , further comprising a step A3 of removing all the layers c and projecting bump conductors on the surface of the plating filling portion.

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