JPH08316602A - Circuit board - Google Patents

Abstract

PURPOSE: To improve electrical contact between a through hole part and a circuit pattern, by filling a through hole with a hardening conductive material in a way that the same horizontal face as the circuit pattern is formed, and making a conductive pattern cover the contact part between the hardened part and the circuit pattern. CONSTITUTION: A through hole 3 is filled with a conductive material 4 to form a through hole part with the same face as both sides or at least one face of the circuit pattern 2. A conductive pattern 7 made of hardening conductive material is formed with uniform thickness at a contact part between the through hole part and the surface circuit pattern 2 so that the conductive pattern 7 covers the contact part. Then, the through hole part and the surface circuit pattern 2 are connected electrically to each other. In addition, the circuit pattern 2 connected to the through hole part may have a land part 8 and preferably, the conductive pattern 7 covering the land part 8 is formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel circuit board. Specifically, in a circuit board having a circuit pattern on both sides or a circuit board having a circuit pattern between at least one surface of a laminate and a plurality of insulating substrates, conduction between the circuit patterns is made of a cured body of a curable conductive material. The present invention relates to a circuit board which is reliable and can be easily performed when a through hole portion is provided.

[0002]

2. Description of the Related Art In general, a circuit board having circuit patterns formed on both sides is electrically connected to the circuit patterns on the front and back sides through through holes. Conventionally, as a method of manufacturing a circuit board having such through-hole portions, (a) through holes are formed in an insulating substrate having conductive layers on both sides by drilling, and after the through holes are subjected to chemical plating / electroplating, A method of forming a circuit pattern by etching the conductive layer, or (b) forming through holes for through holes by drilling or punching in an insulating substrate having conductive layers on both sides, and then etching the conductive layer To form a circuit pattern, and then a curable conductive material typified by a copper paste / silver paste is filled into the through hole by a screen printing method or a pin insertion method and cured to form a through hole filled with a conductive material. A forming method and the like are generally known.

In particular, the above-mentioned method (a) for manufacturing a circuit board has been industrially carried out for a long time and occupies the present mainstream.

[0004]

However, in the method of manufacturing a circuit board described in (a) above, it is necessary to perform plating twice or more in order to improve the reliability of the through hole portion, which is costly. It is not always an advantageous method. Further, since the electroplating is performed on the entire surface of the circuit board, the thickness of the conductive layer becomes non-uniform, and variations may occur during etching for pattern formation. Therefore, it has a drawback that it is difficult to deal with a circuit board having a fine pattern.

In addition, the above-mentioned method (b) for manufacturing a circuit board is characterized in that the manufacturing process is short because chemical plating / electroplating is not required in the through-holes for through-holes. Demand is increasing, but the through-hole portion obtained by filling with a conductive material is placed around the through-hole for through-hole in order to secure the reliability of the electrical connection with the wiring pattern connected to this. It is necessary to cover it with a conductive material and to fill it so as to protrude from the plane of the circuit board.
As a result, in the obtained circuit board, the unevenness of the board surface due to the protruding conductive material becomes an obstacle to solder paste printing at the time of mounting the surface mount component, which hinders reliable connection of the surface mount component.

On the other hand, in order to improve the circuit board of the above (b), the present inventors fill and harden the through holes for through holes so as to project the curable conductive material, and then form the protruding portion made of the conductive material. To form through holes by grinding so as to form the same surface as the conductive layers provided on both sides of the insulating substrate,
Then, a conductive layer was etched to provide a circuit board on which a circuit pattern was formed. Further, in this case, a common plating layer is formed on the conductive material and the conductive layer in the through hole portion, and then the conductive layer is etched to form a circuit pattern, and the circuit pattern and the through hole portion are formed. We also proposed means to improve the reliability of electrical connections.

The circuit board obtained by the above method has few irregularities on the surface of the board, and solder paste printing can be favorably performed at the time of mounting the surface mount component, and the surface mount component can be connected with high reliability. It is necessary to further form a plating layer on the conductive layer, and there are some problems in forming a fine pattern, although not limited to the circuit board of the above (a).

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to solve the above problems in a circuit board having a through hole portion.

As a result, a conductive material is filled in the through hole for a through hole to form a through hole portion having the same plane as the surface circuit pattern, and the connection portion between the through hole portion and the surface circuit pattern is covered. As described above, the circuit board on which the conductive pattern having a uniform thickness is formed by the curable conductive material extremely effectively improves the reliability of the electrical connection between the through hole portion and the circuit pattern on the surface connected to the through hole portion. In addition, since the conductive pattern can be formed by a simple method such as printing, and does not affect the thickness of the conductive layer as compared with plating,
The present invention has been completed by finding that it does not adversely affect etching in forming a circuit pattern and can sufficiently deal with a high-level fine pattern.

That is, the present invention comprises an insulating substrate having circuit patterns formed on both sides thereof, and penetrates the insulating substrate to a location where electrical connection between circuit patterns on both sides of the insulating substrate is required. A through hole for a through hole is provided, a through hole is filled with a conductive material to form a through hole portion having substantially the same plane as the circuit pattern, and the through hole portion and the circuit pattern are formed. Is a circuit board having a uniform thickness and a conductive pattern made of a cured body of a curable conductive material, which covers the connection part.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the accompanying drawings, but the present invention is not limited to these accompanying drawings. A typical embodiment of the circuit board of the present invention is shown in FIGS.

In FIG. 1, the insulating substrate 1 is not particularly limited, and those having known materials and structures can be used without limitation. For example, paper base material-phenolic resin laminated board, paper base material-epoxy resin laminated board, paper base material-polyester resin laminated board, glass base material-epoxy resin laminated board, paper base material-Teflon resin laminated board, glass base material -Polyimide resin laminated substrate, glass base material-BT (bismaleimide-triazine) resin resin laminated substrate, synthetic resin substrate such as composite resin substrate, flexible substrate such as polyimide resin and polyester resin, aluminum, iron,
Examples thereof include a metal-based insulating substrate obtained by insulating a metal such as stainless steel with an epoxy resin or the like, or a ceramic substrate.

When a laminate of a plurality of insulating substrates is used in the circuit board of the present invention, the method for forming the laminate is not particularly limited. Usually, a method of laminating insulating substrates provided with a circuit pattern as needed is adopted, and generally, a pin laminating method and a mass laminating method in which a prepreg is sandwiched between insulating substrates are preferably used. Further, the number of layers of the insulating substrate is determined according to the need of the pattern. The circuit pattern is formed between both surfaces or one surface of the laminate and a plurality of insulating substrates.

The circuit board of the present invention has a circuit pattern on both sides in the case of one insulating substrate, and at least one surface and a plurality of layers in the case of a laminated body of a plurality of insulating substrates. A circuit pattern is provided between the insulating substrates. As the circuit pattern, a known pattern such as a wiring pattern, a land portion, a pad portion or the like is formed as needed.

The material of the circuit pattern to be formed is not particularly limited, but typical examples of the material include copper and nickel. The thickness of the circuit pattern is not particularly limited, but generally a thickness of 5 to 70 μm is suitable.

In the present invention, the through hole 3 for through hole is used.
On the surface of the laminated body when the number of insulating substrates is one, and on the surface of the laminated body when the insulating substrates are a plurality of laminated bodies. Between the formed circuit pattern and the circuit pattern formed between the insulating substrates, or in the case where circuit patterns are formed on both surfaces of the laminate, between both surface circuit patterns, and further , Are provided at locations where electrical connection is required between the circuit patterns on both surfaces of the laminate and the circuit patterns formed between the insulating substrates.

The diameter of the through hole 3 for through hole is not particularly limited and can be set arbitrarily. In the present invention, the diameter of the through hole for the through hole is equal to or larger than the diameter of the hole capable of being filled with a conductive substance,
Usually 0.1 mm or more, preferably 0.2 mm to 2 mm
You can choose more. Further, in the present invention, it is possible to surely establish conduction even with such a minute hole diameter, which is effective for forming a fine pattern described later. In the present invention, the through hole 3 for through hole has a through hole portion which is filled with the conductive material 4 and has substantially the same plane as the circuit pattern 2 on both sides or at least one surface (hereinafter referred to as a surface circuit pattern) 2. It is formed. The material of the conductive material 4 is not particularly limited as long as it is fixed to the through hole 3 for through hole and has conductivity. In the present invention, the curable conductive material 9 that gives a cured product having conductivity after curing is suitable in the process of manufacturing a circuit board in view of ease of filling the through holes 3 for through holes, productivity, and the like. is there.

As the curable conductive material 9, gold, silver,
A known curable conductive substance which is made into a paste by mixing a powdery conductive material made of copper, nickel, lead, carbon or the like and a crosslinkable thermosetting resin such as epoxy resin or phenol resin together with an organic solvent as necessary. Can be used.
From these curable conductive materials, the etching solution used for etching, for example, ferric chloride etching solution, cupric chloride etching solution, ammonium persulfate etching solution, sodium persulfate etching solution, potassium persulfate etching solution, It is preferable to select and use a material that gives a cured product that is not substantially dissolved by an etching solution such as a hydrogen peroxide / sulfuric acid etching solution or an alkaline etching solution containing ammonium sulfate complex ions as a main component.

The curable conductive material 9 has a cured electric resistance of 1 in order to obtain good through-hole resistance.
Selection of conductive material so that it is less than × 10 ^-2 Ω · cm,
And it is preferable to adjust the amount used.

In the present invention, through hole 3 for through hole
It is preferable that the conductive material 4 and the surface circuit pattern 2 that are filled in the surface be formed so as to be substantially coplanar with each other so that the solder paste can be printed well when the surface mount component is mounted on the obtained circuit board. The conductive pattern 7 is made of a hardened material of a curable conductive material and is formed so as to cover the connection portion between the through-hole portion and the surface circuit pattern 2 and is important for reliable connection of the surface mount component. To
It is necessary for forming with accuracy and high reliability.

In the present invention, at the connecting portion between the through hole portion and the surface circuit pattern 2, a conductive pattern 7 having a uniform thickness is formed by a cured body of a curable conductive material so as to cover the connecting portion, and the through hole is formed. Electrical connection between the parts and the surface circuit pattern is made.

By covering the connection portion between the through-hole portion and the surface circuit pattern 2 with the conductive pattern 7 with a uniform thickness, the reliability of the electrical connection between the through-hole portion and the surface circuit pattern 2 can be achieved by a simple means. It is possible to surely improve. In order to improve the reliability of the electrical connection between the through hole portion and the surface circuit pattern 2, such means covers the through holes for through holes with the above-mentioned conventional conductive material so as to cover the surface of the circuit board. Also, the surface of the circuit board is maintained smoother than the means for filling so as to project, which is extremely advantageous in accuracy of the post-process, mounting of components, and the like.

Further, for the same purpose, in the means for covering the through hole portion and the circuit pattern with the plating layer, the difference in the coefficient of thermal expansion between the hardened body of the conductive material filled in the through hole portion and the plating layer is large, Thermal stress concentrates on the plating layer at the time of reflow for mounting components, which may lead to poor conduction of the through hole in some cases. On the other hand, in the present invention, as the conductive material with which the through hole portion is filled and the curable conductive material that covers the through hole portion and the circuit pattern, those having similar thermal expansion coefficients of these cured bodies are used. By doing so, thermal stress generated during reflow is small and high connection reliability can be obtained. Furthermore, since the plating layer that causes the variation in etching is not included, it is advantageous in terms of circuit pattern formation accuracy.

In the embodiment in which the connecting portion between the through hole portion and the surface circuit pattern 2 is covered with the conductive pattern 7, the conductive pattern is present so as to cover at least the contact portion between the peripheral edge of the through hole portion and the surface circuit pattern 2. However, it is more preferable to cover substantially the entire surface of the through hole and the peripheral portion of the surface circuit pattern connected to the through hole. The width of the peripheral portion of the circuit pattern depends on the circuit width of the circuit pattern, etc.
Generally, in consideration of reliability, it is preferable that the distance is 0.05 mm or more from the contact boundary line with the through hole portion.

Further, as shown in FIG.
In order to improve reliability, it is more preferable that the land portion 8 is provided in the circuit pattern 2 connected to the through hole portion, and the conductive pattern is formed so as to cover the land portion as well. The size of the land portion is preferably 0.05 mm or more from the circumference of the through hole portion, but it is preferable to design the land portion to be 2 mm or less in consideration of the wiring density of the circuit board. Of course, it is possible to secure sufficient reliability even in the mode in which the land portion is not formed as shown in FIG.

In any of the embodiments in which the connecting portion between the through hole portion and the surface circuit pattern 2 is covered with the conductive pattern 7, the shape of the connecting portion between the through hole portion and the surface circuit pattern is changed as shown in FIG. It can also be formed in a so-called teardrop shape. By forming the connection portion in a tear drop shape, the area of the surface circuit pattern covered with the conductive pattern 7 increases, and even in the mode in which the land portion shown in FIG. The reliability can be further improved.

Further, as shown in FIG. 1A, the land portion 8 is provided on the surface circuit pattern 2 and the conductive pattern 7 is formed so as to cover the land portion 8 as well, as shown in FIG. As described above, the conductive pattern may be formed in a donut shape except for the central portion of the through hole portion.
By forming the conductive pattern 7 in a donut shape in this manner, the amount of the curable conductive material used in the conductive pattern described later can be reduced, which is economically advantageous.

In the present invention, the conductive pattern 7 formed so as to cover the connecting portion between the through hole portion and the surface circuit pattern 2 needs to have a uniform thickness. That is, by making the conductive pattern uniform,
A stable through-hole resistance value can be obtained, and the yield during manufacturing is improved. Further, since the conductive pattern has a uniform thickness, it is possible to accurately perform solder paste printing, overcoat layer formation, etc., when mounting components, etc., and improve connection reliability of surface mount components. can do.

Further, by making the conductive pattern 7 have a uniform thickness, the surface mount component is mounted on the conductive pattern in a stable state. Therefore, since it becomes possible to directly connect the surface mount component to the conductive pattern, the component mount density can be improved.

Although the thickness of the conductive pattern 7 is not particularly limited, a thickness of 5 μm to 100 μm is preferable in consideration of reliability of through holes and printability of solder paste. Further, it is more preferable to control the thickness in the range of 5 to 50 μm, because component mounting can be extremely easily performed. The variation in the thickness of the conductive pattern 7 depends on the method of forming the conductive pattern 7 and the size of the connection portion of the surface mount component, but is adjusted to be ± 30% or less of the average thickness. It is preferable.

Further, in the present invention, the material of the conductive pattern 7 formed so as to cover the connecting portion between the through hole portion and the surface circuit pattern 2 is a conductive substance filled in the through hole for through hole. It is possible to use the same material as the curable conductive material used, but in particular, use a curable conductive material that gives a cured body with more moisture resistance than the conductive material filling the through holes for through holes. Is preferred.

By forming the conductive pattern 7 having such moisture resistance, it is possible to obtain a circuit board having a through hole portion having excellent reliability, particularly moisture resistance.

The curable conductive substance which gives the above-mentioned moisture resistant cured product can be selected from known curable conductive substances and used. For example, the conductive material contained in the curable conductive substance that gives the moisture-resistant cured body is not particularly limited, but is hard to be oxidized, and gold having a low specific resistance value,
Metals such as silver and copper, and carbon which has a slightly high resistance value but is not affected by oxidation at all can be preferably used.

Further, among the above conductive materials, considering the insulation reliability with the adjacent surface circuit pattern 2, it is preferable to use a metal with less migration. Among them, copper is particularly preferably used in consideration of conductivity, workability for preventing oxidation, cost and the like.

Further, in order to prevent the oxidation of the metal such as copper contained in the curable conductive material, it is more preferable to mainly use a resol type phenol resin as a binder component which gives a reducing atmosphere during thermosetting.

When the above-mentioned resol-type phenol resin is used as a curable conductive material for filling the through-holes 3 for through-holes, the through-holes will be formed in the through-holes due to the effects of water and formalin generated as by-products during thermosetting of the resin. Void occurs, the conductivity of the cured body of the curable conductive material filled in the through hole may decrease, and further, the reliability of the circuit in the vicinity of the through hole may be impaired, but in the present invention,
It can be effectively used in the formation of the conductive pattern 7.

On the other hand, as described above, the curable conductive material 9 to be filled in the through holes 3 for through holes is not particularly limited, but as a binder component, a curable conductive substance 9 and an epoxy resin which hardly generate by-products when the binder is cured are cured. It is preferable to use an epoxy resin binder composed of an agent. The curable conductive material using the binder has
It is slightly inferior to the curable conductive material mainly using the above-mentioned resol type phenol resin as a binder. However, according to the above aspect of the present invention, such a curable conductive substance having poor moisture resistance can be protected by the moisture resistance of the conductive pattern 7, and the reliability can be further enhanced.

Of the materials of the curable conductive material 9 to be filled in the through holes for through holes, the metal component is not particularly limited, but if the insulation reliability with adjacent through holes is taken into consideration, less migration will occur. It is preferable to employ a metal. Among them, copper is particularly preferably used in consideration of conductivity, workability for preventing oxidation, cost and the like.

In the present invention, the through holes 3 for through holes are filled with a curable conductive material 9 using an epoxy resin-based binder which causes less by-products when the binder is cured, and the conductive material inside the through holes is filled. No. 4 and a curable conductive material formed so as to cover the connection portion of the through-hole portion and the surface circuit pattern 2 with a resol type phenol resin as a binder main component and copper with less migration as a metal component. The embodiment using a moisture resistant copper paste is most recommended.

By forming the through-hole portion with such a structure, it is possible to obtain a circuit board having a highly reliable through-hole portion without defects inside the through-hole.

In the present invention, known techniques can be used for the other portions and there is no particular limitation. For example, a portion of the circuit pattern other than the connection terminal may be protected by forming an overcoat layer with a known insulating resin (resist), or the surface of the surface circuit pattern 2 may be protected by a known means. It is also possible to form a circuit pattern made of a plated layer of copper or the like through the insulating layer formed except for.

When the surface mount component is mounted on only one surface, only the surface on which the surface mount component is mounted may be the circuit board of the present invention. That is, the surface on which the component is not mounted is covered with a conventional conductive material around the through-hole for the through hole, and the conductive material is filled so as to project from the plane of the circuit board. The circuit board aspect of the invention may also be employed.

Furthermore, the material of the conductive pattern 7 formed so as to cover the connection portion between the through hole portion and the surface circuit pattern 2 is a hardened material which can be coated with solder after hardening, or nickel which is usually used for terminal plating or the like. When a curable conductive material that gives a hardened body capable of forming gold plating is adopted, surface mount components can be directly connected to the conductive pattern 7 (through hole portion), further improving the component mounting density. It becomes possible to do. The shape of the conductive pattern in the above mode is not particularly limited, but as shown in FIG. 8, in order to improve the stability of the connection between the conductive pattern and the surface mount component, almost all of the pad section is covered and the pad section is A flat shape is preferable in terms of ease of mounting the surface mount component. Furthermore, the mode in which the conductive patterns are formed on all the pad portions on which the mounting components are mounted is more preferable because the surface mounting components are mounted in a more stable state, and therefore the mounting of the surface mounting components is easy.

The mode of the circuit board of the present invention is not particularly limited, but typical modes are shown in FIGS. 1 and 2.

In the mode shown in FIG. 1A, land portions 8 are provided on the surface circuit patterns on both surfaces connected to the through holes, and the conductive patterns 7 are formed so as to cover the land portions. .

In the mode shown in FIG. 1B, the conductive pattern 7 is formed without providing the land portion 8 on the surface circuit patterns on both surfaces connected to the through hole portion.

In the mode shown in FIG. 1C, the land portions 8 are provided on the surface circuit patterns on both surfaces connected to the through holes, and the conductive pattern 7 is formed so as to cover the conductive pattern 7 on only one surface. Is.

In the mode shown in FIG. 1D, the land portions 8 are provided on the surface circuit patterns on both surfaces connected to the through holes, and the conductive patterns are formed so as to cover the land portions. A nickel / gold plating layer is provided on the portion and the conductive pattern portion. Thereby, even when the conductive pattern is a conductive paste having poor solder wettability, the surface mount component can be mounted on the conductive pattern.

The mode shown in FIG. 2A is a circuit board comprising a laminate of three insulating substrates, and the surface circuit pattern 2 is formed between the insulating substrates and on both surfaces of the laminate. In this case, the land portion 8 is provided on the surface circuit pattern 2 connected to the through hole portion, and the conductive pattern is formed so as to cover the land portion as well.

The modes shown in FIGS. 2B and 2C are as follows.
A circuit board comprising a laminated body of three insulating substrates, wherein the surface circuit pattern 2 is formed between the insulating substrates and on one surface of the laminated body, the surface circuit pattern being connected to the through hole portion. 2 is provided with a land portion 8 and is formed so as to cover the conductive pattern 7 including the land portion.

The method for manufacturing the circuit board of the present invention is not particularly limited, but if a typical manufacturing method is illustrated,
The method shown in FIGS. 3, 4 and 5 may be mentioned.

That is, in the circuit board of the present invention, as shown in FIG. 3, (a) through-holes for through holes are formed at positions where electrical connection between the surface circuit patterns 2 formed on both surfaces of the insulating board 1 is required. 3 and (b) a through-hole through-hole 3 is filled with a curable conductive substance 9 that gives a cured product having conductivity and cured, and (c) a surface circuit formed on both sides of the insulating substrate. The surface constituted by the pattern 2 and the conductive material 4 is ground to be substantially smooth, and (d) a curable conductive material is then applied so as to cover the connecting portion between the through hole portion and the surface circuit pattern 2. Can be obtained by forming the conductive pattern 7 having a uniform thickness.

As another method in which the surface circuit pattern 2 is not formed on both sides of the insulating substrate in advance, as shown in FIG. 4, (a) the through hole 3 for through holes is formed in the insulating substrate 1 having the conductive layers 5 on both sides. And (b) a curable conductive substance 9 which gives a cured product having conductivity to the through hole 3 for through hole.
And then hardened, (c) the surface constituted by the conductive layer 5 and the conductive material 4 is ground smoothly, and (d) the surface circuit pattern 2 is then formed on the conductive layer 5, (E) A circuit board of the present invention is manufactured by applying a curable conductive material to form a conductive pattern 7 having a uniform thickness so as to cover a connecting portion between the through hole portion and the surface circuit pattern 2. You can

Further, as a method of forming conductor patterns in advance before forming the surface circuit pattern 2 on both surfaces of the insulating substrate, as shown in FIG. 5, (a) an insulating substrate 1 having conductive layers 5 on both surfaces is formed. Providing a through hole 3 for through hole,
(B) After the curable conductive substance 9 that gives a cured body having conductivity is filled in the through hole for through hole and cured,
(C) The surface constituted by the conductive layer 5 and the conductive material 4 is ground smoothly, and (d) a curable conductive material is then applied so as to cover the through hole portion and the conductive layer around the through hole. After forming the conductive pattern 7 having a uniform thickness by (e) forming the surface circuit pattern 2 on the conductive layer 5, the circuit board of the present invention can be manufactured.

Even when a laminate of a plurality of insulating substrates in which the circuit pattern 11 is formed between the plurality of insulating substrates is used, it can be manufactured by the same method as described above. When the through hole 3 for a through hole is provided in the laminated body, it is not particularly limited, but the inner wall of the through hole is subjected to smear removal or etch back treatment to form a conductive material formed in the through hole. Circuit pattern 11 formed between insulating substrates
The connection stability with and the reliability of the conduction of the through hole portion are improved.

In the above method, as the method for forming the through hole 3 for through holes, known means similar to those for manufacturing a usual circuit board such as drilling, punching, and laser processing may be used without any particular limitation.

The through-hole through-hole 3 formed in the insulating substrate 1 is filled with the curable conductive material so that the curable conductive material 9 fills the entire space of the through-hole through-hole and the surface circuit is formed. Slightly from the surface of the pattern 2 or the conductive layer 5, specifically, 0.1 mm or more, preferably 0.
It is desirable to fill so as to project by 1 mm to 2 mm. A typical filling method of a curable conductive material is, for example, a method of applying one or more times by a printing method, a method of press-fitting with a pair of front and back squeegees from both sides of an insulating substrate, a roll coater or curtain coater Means such as a filling method is preferably used.

Further, when the curable conductive substance 9 is filled, the curable conductive substance originally exhibits conductivity because the conductive material contained in the curable conductive substance comes into contact due to curing contraction during curing of the binder. Yes, there is always shrinkage during curing. Therefore, when the through-hole through-hole 3 is filled with the curable conductive substance 9, the shrinkage rate is taken into consideration so that the surface of the cured body of the curable conductive substance does not become recessed from the circuit pattern 2 after curing. Preferably.

The hardening of the curable conductive material 9 filled in the through holes 3 for through holes is carried out by hot air oven, infrared oven,
A suitable one may be appropriately selected and cured from known curing methods such as a far infrared ray furnace, an ultraviolet ray curing furnace, and an electron beam curing furnace.

Furthermore, the hardening of the curable conductive material 9 filled in the through holes 3 for through holes is generally carried out immediately after the filling, but it may be carried out at the same time as the later step of forming the conductive pattern 7. It is possible.

The method of making the conductive material 4 filled in the through-holes 3 for through holes substantially flush with the surface circuit pattern 2 of the insulating substrate 1 or the conductive layer 5 will be described below. Conductive material 9 through hole for through hole 3
It is preferable to use a method in which the hardened material (conductive material) of the curable conductive material is smoothed after it has been filled in, and the portion where the hardened material (conductive material) protrudes from the surface circuit pattern 2 or the conductive layer 5 is smoothed. As a method for smoothly grinding the surface circuit pattern or the portion where the conductive material 4 protrudes from the conductive layer 5, a method used for polishing a normal circuit board such as slurry polishing, buff polishing, scrub polishing, and belt polishing is used. It is preferably used.

Although not shown in the figure, in the step (c) of FIG. 3, the surface circuit pattern 2 is protected to protect the surface circuit pattern 2 when the surface of the conductive material 4 is ground smoothly. It is also possible to form an overcoat layer composed of the above-mentioned resist.

The method of forming the circuit pattern 2 from the conductive layer 5 of the insulating substrate 1 is not particularly limited, and a known method can be used without particular limitation.

To give an example of a general forming method, for example,
A general method is to perform etching after forming an etching pattern with an etching resist on the surface of the conductive layer 5 of the insulating substrate 1 having the conductive layers 5 on both sides. As the etching resist used here, a dry film, a resist ink or the like is used without particular limitation, and it may be appropriately selected and used depending on the fineness of the pattern. Further, as the etching resist pattern, a positive pattern or a negative pattern may be appropriately adopted by the etching method. For example, a positive pattern may be adopted in the etching method typified by the tenting method, and a negative pattern may be adopted in the etching method typified by the solder peeling method and the SES method.

If the circuit pattern shown in FIGS. 4 and 5 is not formed in advance and the surface formed by the conductive layer 5 and the conductive material 4 is ground smoothly and then the circuit pattern is formed, the electrodeposition photo When the resist film is formed by the ED method, since the resist film is electrically formed, a highly accurate and highly reliable circuit pattern can be obtained without being adversely affected by dust and the like.

In particular, when a negative electrodeposition photoresist film is used, since the through holes 3 for through holes are filled with the conductive material 4, it is not necessary to expose the inside of the through holes for through holes, and Through holes having a small diameter of 3 mm or less can be reliably formed.

Further, a curable conductive material is applied so as to cover the connection portion between the through hole portion and the surface circuit pattern 2 or the conductive layer 5 around the through hole portion to form a conductive pattern 7 having a uniform thickness. As the method, a known method for producing a conductive pattern by printing is preferably adopted. Specifically, there may be mentioned a method of applying a curable conductive substance to a required portion using a dispenser and then curing, a method of applying a curable conductive substance by a screen printing machine and then curing. In the case where the surface mount component is directly connected to the conductor pattern 7 on the through hole portion described above, in order to stably mount the component, a circuit other than the through hole portion on which the surface mount component is directly mounted is mounted. Also when the curable conductive substance is applied onto the pattern to form a conductive pattern having a uniform thickness, the same forming method as described above is adopted, and is usually performed simultaneously.

The through hole and the surface circuit pattern 2
Alternatively, the hardening of the curable conductive material covering the connection portion with the conductive layer 5 around the through hole portion is carried out in the same manner as the hardening method of the curable conductive material 9 filled in the through hole for through hole 3 described above. A known one, such as an infrared furnace, a far infrared furnace, an ultraviolet curing furnace, and an electron beam curing furnace, may be appropriately selected and cured by a suitable curing agent for the curable conductive material.

In the present invention, as described above, the conductive substance 4 filled in the through hole 3 for through hole and the surface circuit pattern 2 or the conductive layer 5 are formed so as to be substantially flush with each other. Therefore, for example, when a curable conductive material is applied to the connection portion using a screen printing machine, no bleeding occurs during printing, resulting in excellent workability and even application of the curable conductive material. It becomes possible.

Further, the conductive pattern 7 formed in the through hole portion and the connection portion of the surface circuit pattern 2 is uniform and thin. Therefore, in the above-mentioned conventional means for filling the conductive material in a protruding manner so as to cover the through hole through hole, the conductive material is formed in the surface circuit pattern portion and the protruding portion in two steps. However, according to the present invention, the solder resist layer can be formed once and accurately.

Further, the surface circuit pattern 2 shown in FIG.
In the case where the surface formed by the conductive layer 5 and the conductive material 4 is not ground, the conductive pattern 7 is formed and the surface circuit pattern 2 is formed, the through holes 3 for through holes are filled. The surface of the conductive material 4 is not exposed to an etching resist, an alkaline solution such as a stripping solution of the etching resist, or a pickling solution for surface treatment, and the surface of the conductive material 4 or the conductive material and the land portion 8 are not exposed. Since the connection interface with and is not contaminated, a reliable through hole can be formed.

In the method of the present invention, the surface formed by the surface circuit pattern 2 or the curable conductive material 9 and the conductive material 4 is ground smoothly to form the conductive pattern 7. After forming the pattern 7, the other surface may be ground to form the conductive pattern 7.

Therefore, according to the method of the present invention, the electrical connection between the through hole portion and the circuit pattern can be made reliably and reliably.

[0074]

As is apparent from the above description, the circuit board of the present invention does not require chemical plating or electroplating, and the thickness of the conductive pattern formed at the connecting portion between the through hole portion and the surface circuit pattern is small. Uniformity, high through-hole conduction reliability, and accurate solder paste printing during mounting of surface mount components, and high connection reliability of surface mount components.

Further, according to the manufacturing method of the present invention, since the surface of the curable conductive material filled and cured in the through hole for the through hole has substantially the same plane as the circuit pattern, a through step which is a subsequent step is performed. The conductive pattern can be accurately and uniformly formed from the curable conductive material at the connection between the hole and the circuit pattern.

Therefore, the circuit board of the present invention is a circuit board having a high yield and a high mounting density and wiring density as compared with the conventional circuit boards which have been subjected to chemical plating or electric plating.

[0077]

EXAMPLES Examples will be shown below for specifically explaining the present invention, but the present invention is not limited to these examples.

Example 1 As the curable conductive material 9 with which the through holes 3 for through holes were filled, a copper paste having the following composition was used. That is, 35 parts by weight of decyl glycidyl ether as a binder component and 35 parts by weight of bisphenol A diglycidyl ether having an epoxy equivalent of 173 g / equivalent and 100 parts by weight of the bisphenol A diglycidyl ether, and a novolac type phenol resin as a curing agent are used. Binder 100 parts by weight and dendritic copper powder having an average particle size of 10.5 μm as copper powder
360 parts by weight is added to parts by weight, and 2-ethyl-
What added 2.8 weight part of 4-methylimidazole with respect to 100 weight part of binders was knead | mixed for 45 minutes with a three roll, and the copper paste was prepared.

Further, as the curable conductive material of the conductive pattern 7 formed so as to cover the connecting portion between the through hole portion and the circuit pattern, the main component of the binder is a resol-type phenol resin (Tatsuta Electric Wire Co., Ltd.). ) Copper Paste NF-2000 manufactured by the same company was used.

Hereinafter, the copper paste containing the former epoxy resin as the main component of the binder is "copper paste A", and the latter copper paste containing the resol-type phenol resin as the main component is Tatsuta Electric Wire Co., Ltd.'s copper paste NF2000. Paste B "
Described as.

A circuit board was manufactured according to the steps shown in FIG. That is, (a) a 1.2 mm-thick glass epoxy substrate having conductive layers 5 made of copper foil on both surfaces is used as the insulating substrate 1, and 100 through-hole through holes 3 having a diameter of 0.6 mm are provided by drilling. Forming a surface circuit pattern 2 including lines and lands having a width of 50 μm and a space of 50 μm on both surfaces of the insulating substrate, and (b) using the copper paste A as a curable conductive material 9 in the through hole for the through hole. Fill it by screen printing so that it protrudes 0.25 mm from the pattern, and use an air oven to fill it.
After curing under conditions of 0 ° C. for 30 minutes and 180 ° C. for 60 minutes, (c) the surface composed of the surface circuit pattern and the curable conductive material is sequentially used with the 200th buff and the 360th buff. Then, after smoothing to form a through hole portion filled with the conductive material 4, (d) the substantially entire surface of the through hole portion and the width of the surface circuit pattern 2 connected to the through hole of 0.1 mm. The copper paste B as a curable conductive material covering the peripheral portion of the is coated by a screen printing method and cured in an air oven at 160 ° C. for 30 minutes to have an average thickness of 30 μm (± 10% variation). Conductive pattern 7 was formed to obtain 100 double-sided circuit boards.

The obtained circuit board did not cause short circuit and disconnection of the circuit pattern, and the yield was 100%. When the resistance value of the through hole was measured between the conductive patterns 7 formed on the front and back of the circuit board for the circuit board,
The average was 15 mΩ / hole. This circuit board is 60 ℃
After exposing for 1000 hours under the high temperature and high humidity condition of 90% RH, the through hole resistance value was measured again, and it was 17 mΩ / average.
It was a hole. In addition, the above-mentioned circuit board has few irregularities on the surface of the board, and solder paste printing during mounting of the surface mount component can be performed well, and the surface mount component can be connected with high reliability.

Example 2 A circuit board was manufactured according to the steps shown in FIG.
That is, (a) 100 holes of through holes 3 for through holes having a diameter of 0.5 mm are provided by drilling in an insulating substrate 1 of a glass epoxy substrate having a thickness of 1.2 mm having conductive layers 5 made of copper foil on both sides. (B) The through holes 3 for through holes are filled with a copper paste A as a curable conductive material 9 by a screen printing method, and the mixture is placed in an air oven at 50 ° C. for 30 minutes for 18 minutes.
After curing under conditions of 0 ° C. and 60 minutes, (c) the surface constituted by the conductive layer and the curable conductive material is ground smoothly using a 200th buff and a 360th buff. After forming the through hole portion filled with the conductive material 4,
(D) Next, using an etching resist on the conductive layer 5, a surface circuit pattern 2 including lines and lands having a width of 50 μm and a spacing of 50 μm is formed on both surfaces, and then (e).
A copper paste B is applied by a screen printing method as a curable conductive material that covers substantially the entire surface of the through hole portion and the edge portion of the surface circuit pattern 2 connected to the through hole, which has a width of 0.1 mm. The copper paste B was cured under the conditions of 160 ° C. for 30 minutes in an air oven to form a conductive pattern 7 having an average thickness of 25 μm (variation of ± about 10%), and 100 double-sided circuit boards were obtained.

The obtained circuit board did not cause short circuit and disconnection of the circuit pattern, and the yield was 100%. When the resistance value of the through hole was measured between the conductive patterns 7 formed on the front and back of the circuit board for the circuit board,
The average was 19 mΩ / hole. This circuit board is 60 ℃
After exposure for 1000 hours under the high temperature and high humidity condition of 90% RH, the through hole resistance value was measured again, and the average was 22 mΩ /
It was a hole. In addition, the above-mentioned circuit board has few irregularities on the surface of the board, and solder paste printing during mounting of the surface mount component can be performed well, and the surface mount component can be connected with high reliability.

Example 3 A circuit board was manufactured according to the steps shown in FIG.
That is, (a) 100 holes of through holes 3 for through holes having a diameter of 0.5 mm are provided by drilling in an insulating substrate 1 of a glass epoxy substrate having a thickness of 1.2 mm having conductive layers 5 made of copper foil on both sides. (B) The through holes 3 for through holes are filled with a copper paste A as a curable conductive material 9 by a screen printing method, and the mixture is placed in an air oven at 50 ° C. for 30 minutes for 18 minutes.
After curing under conditions of 0 ° C. and 60 minutes, (c) the surface constituted by the conductive layer and the curable conductive material is ground smoothly using a 200th buff and a 360th buff. After forming the through hole portion filled with the conductive material 4,
(D) Applying a copper paste B as a curable conductive material by a screen printing method so as to cover substantially the entire surface of the through hole portion and the edge portion having a width of 0.1 mm of the surface circuit pattern 2 connected to the through hole. Then, air oven 160 ℃ 30
The copper paste B is hardened under the condition of min.
Form the conductive pattern 7 (variation of about ± 10%),
(E) Next, using an etching resist for the conductive layer 5, a surface circuit pattern 2 including lines and lands having a width of 50 μm and a spacing of 50 μm was formed on both surfaces to obtain 100 double-sided circuit boards.

The obtained circuit board did not cause short circuit and disconnection of the circuit pattern, and the yield was 100%. When the resistance value of the through hole was measured between the conductive patterns 7 formed on the front and back of the circuit board for the circuit board,
The average was 18 mΩ / hole. This circuit board is 60 ℃
After exposure for 1000 hours under the high temperature and high humidity condition of 90% RH, the through hole resistance value was measured again, and the average value was 19 mΩ /
It was a hole. In addition, the above-mentioned circuit board has few irregularities on the surface of the board, and solder paste printing during mounting of the surface mount component can be performed well, and the surface mount component can be connected with high reliability.

Example 4 A circuit board was manufactured according to the steps shown in FIG. 4, and finally nickel-gold plating was applied. That is, (a) 100 holes of through holes 3 for through holes having a diameter of 0.5 mm are provided by drilling in an insulating substrate 1 of a glass epoxy substrate having a thickness of 1.2 mm having conductive layers 5 made of copper foil on both sides.
(B) After filling the through-holes 3 for through holes with a copper paste A as a curable conductive material 9 by a screen printing method and curing in an air oven under conditions of 50 ° C.-30 minutes and 180 ° C.-60 minutes, (C) The surface constituted by the conductive layer and the curable conductive material was sequentially ground by using No. 200 buff and No. 360 buff to form a through hole portion filled with the conductive substance 4. After that, (d) an etching resist is used for the conductive layer 5, and the width is 50 μm on both sides.
m), after forming the surface circuit pattern 2 including a line and a land portion with a space of 50 μm, (e) a substantially entire surface of the through hole portion and a side having a width of 0.1 mm of the surface circuit pattern 2 connected to the through hole. A copper paste B as a curable conductive material is applied by a screen printing method so as to cover the edge portion and the pad portion on which the surface mount component is mounted, and the copper paste B is applied under the conditions of an air oven 160 ° C. for 30 minutes. Is cured to form a conductive pattern 7 having an average thickness of 25 μm (± 10% variation), and then nickel plating 4 μm and gold plating 0.2 μm are applied on the surface circuit pattern and the conductive pattern to form a double-sided circuit. 100 substrates were obtained.

The obtained circuit board did not cause short circuit and disconnection of the circuit pattern, and the yield was 100%. When the resistance value of the through hole was measured between the conductive patterns 7 formed on the front and back of the circuit board for the circuit board,
The average was 19 mΩ / hole. This circuit board is 60 ℃
After exposure for 1000 hours under high temperature and high humidity conditions of 90% RH, the through-hole resistance value was measured again, and the average was 20 mΩ /
It was a hole. In addition, the above-mentioned circuit board has few irregularities on the surface of the board, and solder paste printing during mounting of the surface mount component can be performed well, and the surface mount component can be connected with high reliability. In addition, the surface-mounted components could be connected on the conductive pattern with high reliability.

Example 5 A circuit board was manufactured using the laminated body of insulating substrates according to the steps shown in FIG. 4, and finally nickel-gold plating was applied. That is, (a) a thickness of a laminated body of three insulating substrates, a circuit pattern made of copper foil between the insulating substrates, and conductive layers 5 made of copper foil on both surfaces of the laminated body. 1.
100 mm through-hole through-holes 3 having a diameter of 0.5 mm are provided by drilling in a laminated body of a 2 mm glass epoxy insulating substrate, and (b) copper paste as a curable conductive material 9 is provided in the through-hole through-holes 3. A was filled by the screen printing method, and it was heated in an air oven at 50 ° C. for 30 minutes for 180 minutes.
After being cured under conditions of -60 ° C, (c) the surface constituted by the conductive layer and the curable conductive material is ground and smoothed by sequentially using the 200th buff and the 360th buff. After forming the through holes filled with the substance 4,
(D) Next, using an etching resist for the conductive layer 5, after forming the surface circuit pattern 2 including lines and lands having a width of 50 μm and a spacing of 50 μm on both surfaces,
(E) Applying a copper paste B as a curable conductive material by a screen printing method so as to cover the connecting portion between the through hole portion and the surface circuit pattern 2 and to cover the pad portion where the surface mount component is mounted. Air oven 160 ℃
The copper paste B is cured under the condition of -30 minutes, and the average thickness is 25
After forming the conductive pattern 7 of μm (± 10% variation), 4 μm of nickel plating and 0.2 μm of gold plating were applied on the circuit pattern and the conductive pattern to obtain 100 multilayer circuit boards.

The obtained circuit board did not cause short circuit and disconnection of the circuit pattern, and the yield was 100%. When the resistance value of the through hole was measured between the conductive patterns 7 formed on the front and back of the circuit board for the circuit board,
The average was 19 mΩ / hole. The resistance value of the through hole between the inner layers was measured and found to be 22 mΩ / hole. After this circuit board was exposed to high temperature and high humidity conditions of 60 ° C.-90% RH for 1000 hours, the through-hole resistance values of the conductor patterns formed on the front and back of the circuit board were measured again, and the average value was 20 mΩ / hole, between inner layers. When the through-hole resistance value was measured again, it was 22 mΩ / hole on average. In addition, the above-mentioned circuit board has few irregularities on the surface of the board, and solder paste printing during mounting of the surface mount component can be performed well, and the surface mount component can be connected with high reliability. In addition, the surface-mounted components could be connected on the conductive pattern with high reliability.

Comparative Example 1 In Example 1, a circuit board was manufactured by the steps (a) and (b). In order to mount the surface mount component on the obtained circuit board, a solder paste was printed on the circuit board by a screen printing method, but the solder paste was hardly printed on the circuit board and the component could be mounted. There wasn't. Moreover, when the resistance value of the through holes was measured on the front and back of the obtained circuit board, it was found to be 17 mΩ / hole on average. After this circuit board was exposed to high temperature and high humidity conditions of 60 ° C. and 90% RH for 1000 hours, the through hole resistance value was measured again, which was 98 mΩ / hole on average, and the resistance value was remarkably increased.

Comparative Example 2 In Example 3, after forming the through holes by the steps (a) to (c), a common plating layer was formed on the through holes and the conductive layer, and then the plating was performed. 50 μm wide on both sides using an etching resist for the layer and the conductive layer 5.
The surface circuit pattern 2 including lines and lands each having m and an interval of 50 μm was formed to obtain 100 double-sided circuit boards.
The resulting circuit board had a short circuit pattern and a broken wire, and the yield was 27%.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a typical aspect of a circuit board of the present invention.

FIG. 2 is a cross-sectional view showing a typical aspect of the circuit board of the present invention.

FIG. 3 is a process drawing showing a typical method for manufacturing a circuit board of the present invention.

FIG. 4 is a process drawing showing a typical method for manufacturing a circuit board of the present invention.

FIG. 5 is a process drawing showing a typical method for manufacturing a circuit board of the present invention.

FIG. 6 is a plan view showing a typical embodiment of a conductive pattern in the circuit board of the present invention.

FIG. 7 is a plan view showing a typical embodiment of a conductive pattern in the circuit board of the present invention.

FIG. 8 is a plan view showing a typical embodiment of a conductive pattern in the circuit board of the present invention.

[Explanation of symbols]

 1 Insulating Substrate 2 Surface Circuit Pattern 3 Through Hole Through Hole 4 Conductive Material 5 Conductive Layer 6 Overcoat Layer 7 Conductive Pattern 8 Land Part 9 Curable Conductive Material 11 Circuit Pattern Formed Between Insulating Boards 12 Nickel / Gold Plating Layer 13 Pad part

Claims (2)

[Claims] 1. A through hole penetrating through an insulating substrate, comprising an insulating substrate having a circuit pattern formed on both sides thereof, and where electrical connection between circuit patterns existing on both sides of the insulating substrate is required. A hole is provided, the through hole for through hole is filled with a conductive material to form a through hole portion having substantially the same plane as the circuit pattern, and a connecting portion between the through hole portion and the circuit pattern is formed. A circuit board having a conductive pattern formed of a cured body of a curable conductive material having a uniform thickness. 2. A circuit board comprising a laminate of a plurality of insulating substrates, wherein a circuit pattern is formed between at least one surface of the laminate and the plurality of insulating substrates, and a circuit pattern is formed on the surface of the laminate. Between the formed circuit pattern and the circuit pattern formed between the insulating substrates, or when a circuit pattern is formed on both surfaces of the laminate, an electrical connection is made between the surface circuit patterns on both surfaces. Through holes for through holes that penetrate the laminated body are provided at places where connection is required, and the through holes for through holes are filled with a conductive substance to substantially form a circuit pattern formed on the surface of the laminated body. A through hole portion having the same surface is formed, and a conductive pattern made of a cured body of a curable conductive material having a uniform thickness is formed to cover a connection portion between the through hole portion and the circuit pattern formed on the surface. Octopus Circuit board according to claim.