JPH08279673A - Circuit board - Google Patents

Abstract

PURPOSE: To provide a circuit board which is capable of stable surface mount on a conductive through hole formed for electrically connecting the part between circuit patterns formed on both surfaces, and can be easily manufactured. CONSTITUTION: On an insulating board 1 with circuit pattern 2, 2' on both sides, a penetrating hole 5 as a through hole which penetrates the insulating board is formed in a part where electric connection between the circuit patterns is necessary. A conductive layer is formed on the inner wall of the penetrating hole, thereby forming a conductive through hole 4. A cured body of hardening paste is buried in the through hole, in the manner in which the through hole is closed, the cured body does not protrude from the circuit pattern surface, and a recessed surface is constituted inside the periphery of the through hole at least in a part.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel circuit board. More specifically, it is a circuit board that can be stably surface-mounted on a conductive through hole provided for making electrical connection between circuit patterns formed on both sides and is easy to manufacture. .

[0002]

2. Description of the Related Art Conventionally, electrical connection between circuit patterns on both sides formed on a circuit board is performed by forming a conductive layer 3 on the inner wall of a through hole 5 for a through hole as shown in (1) FIG. Means for electrically connecting the circuit patterns 2 and 2'on both surfaces by forming the conductive through hole 4, (2)
As shown in FIG. 5, the through hole 5 for through holes is filled with the hardened body 9 of the curable conductive paste, and the conductive through holes 4 are formed.
A means for electrically connecting the circuit patterns 2, 2 ′ on both sides by forming a wiring is generally known.

[0003]

However, in the above connecting means, when it is attempted to mount the surface mount component on or near the conductive through hole, the circuit board having the structure of (1) above has a structure in the conductive through hole. Since there is a through hole in the component, the solder diffuses to the opposite surface through the conduction through hole when fixing the component, so that not only the amount of solder required for component connection cannot be maintained, but also the circuit pattern on the opposite surface is short-circuited. However, stable component mounting cannot be performed.

The circuit board having the structure (2) is
Since the through hole for the through hole is closed, the above problem does not occur, but in such a connecting means, in order to obtain electrically stable conduction, even the periphery of the through hole for the through hole of the circuit pattern is electrically conductive. It is necessary to fill the cured body of the curable conductive paste so as to cover the substance. Therefore, in the state where the cured body of the curable conductive paste is filled,
A protrusion of the cured body of the curable conductive paste is formed.

Such a protrusion not only hinders stable fixing of the surface-mounted component at the time of fixing the component but also makes it difficult to control the amount of solder at the time of solder cream printing necessary for component connection, resulting in stable component mounting. It has the problem of being difficult to do.

Therefore, in mounting the surface-mounted components of the circuit board having these conductive through holes, it is necessary to avoid the conductive through holes and mount the components. This causes a problem that the density and the wiring density are significantly reduced.

In order to solve the above problem, the applicant of the present invention, in the above-mentioned means (1), fills a conductive through-hole with a hardened body of a hardenable paste so as to be flush with the circuit pattern. (Also referred to as) (Japanese Patent Laid-Open No. 5-243728). The circuit board can solve all of the problems in (1) and (2) above, but in the case where the diameter of the conduction through hole is large or the number of conduction through holes is large, Not only a large amount of the curable paste to be filled in the conduction through holes is required, but also the amount of the cured body of the curable paste that protrudes from the surface of the circuit pattern after the curable paste is filled and cured increases. The amount of the hardened body of the curable paste that is removed and discarded in order to obtain a smooth surface is also increased.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have determined that the filling amount of the hardened body of the curable paste into the conductive through holes is such that the conductive through holes are blocked. However, by stopping the amount enough to form a depressed surface inside the edge of the conduction through hole,
While solving the problems (1) and (2), the amount of the curable paste used in a large amount in the improved substrate can be suppressed to a small amount, and extremely stable component mounting is performed on the conductive through holes. It has been found that this is possible, and the present invention has been completed.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited to these accompanying drawings.

FIG. 1 is a partial sectional view showing a typical structure of a circuit board of the present invention.

That is, in this study, the circuit patterns 2 on both sides are
In the insulating substrate 1 on which 2'is formed, a through hole through hole 5 penetrating the insulating substrate is provided at a position where electrical connection between the circuit patterns is required, and an inner wall of the through hole through hole is formed. A conductive through-hole 4 is formed by providing the conductive layer 3, and the conductive through-hole is closed, does not protrude from the surface of the circuit pattern, and at least partially forms a surface depressed inside the edge of the conductive through-hole. As described above, the circuit board is characterized in that the conductive through hole is filled with the hardened body 11 of the hardenable paste.

As the insulating substrate 1 used in the present invention, those having known materials and structures used for circuit boards can be used without particular limitation. Typical examples of the above-mentioned substrate include a paper base material-phenol resin laminated board, a paper base material-epoxy resin laminated resin board, a paper base material-polyester resin laminated board, a glass base material-epoxy resin laminated board, Paper substrate-Teflon resin laminated substrate, glass substrate-polyimide resin laminated substrate, glass substrate-BT (bismuth-triazine) resin resin laminated substrate, synthetic resin substrate such as composite resin substrate, flexible such as polyimide resin, polyester resin, etc. Examples thereof include a substrate, a metal-based insulating substrate obtained by insulating a metal such as aluminum, iron, and stainless with an epoxy resin or the like, a ceramic substrate, and the like.

The insulating substrate has circuit patterns on both sides. The circuit pattern is used without particular limitation, such as a signal line, a power line, a ground line, and a pad for connecting components. The material of the circuit patterns 2, 2'is not particularly limited as long as it has conductivity. Typical examples of the material include metal materials such as copper, nickel and aluminum. The thickness of the circuit pattern is not particularly limited, but generally 5 to 70 μm is preferable from the viewpoint of reliability of the circuit pattern and ease of formation.

The circuit pattern forming method according to the present invention is
The method is not particularly limited and can be carried out by a known method. Specific examples include a pattern plating method, a panel plating method, a semi-additive method, and a full-additive method.

As the etching resist used for forming the etching pattern, a dry film, a resist ink, an electrodeposition photoresist, etc. may be used without limitation, and the kind may be appropriately selected depending on the fineness of the pattern.

In the insulating substrate 1 having the above circuit pattern, through-holes 5 for through holes are provided on the front and back surfaces of the insulating substrate at positions where electrical connection between circuit patterns is required. The shape of the through hole for the through hole is not particularly limited, but usually a circular shape is preferable from the viewpoint of easy workability. The size of the through hole for the through hole is not particularly limited, but when the shape is circular, the diameter can be generally selected from 0.1 mm or more, preferably from 0.2 to 2.0 mm.
As a method of forming the through hole, a known method such as a drilling method, a punching method, or a laser method can be employed without any particular limitation.

In the present invention, the through hole 5 for through hole is used.
A conductive layer 3 is formed on the inner wall of the substrate to provide electrical connection between circuit patterns. The conductive layer is not particularly limited as long as it has known conductivity, but it can be generally formed by plating because of its ease of formation and high reliability. The material of the plating layer forming the conductive layer 3 is not particularly limited as long as it is a known conductive metal such as copper. The method for forming the plating layer is not particularly limited, and known methods can be adopted without particular limitation. Generally, a chemical (electroless) plating method, an electroplating method, a combined chemical / electroplating method and the like can be mentioned. Further, the thickness of the plating layer is preferably such that the reliability of the conductive through hole by plating is improved and the unevenness of the thickness of the plating layer does not occur. Generally, from the viewpoint of preventing thickness unevenness, it is preferably 50 μm or less, and 5 μm or more in consideration of improvement of reliability of the conductive through hole. Particularly preferably, it is 5 to 35 μm.

An insulating substrate 1 having the above circuit pattern
Although not shown in the figure, it is also possible to use an insulating substrate having an inner layer having one or more circuit patterns. The electrical connection between the circuit patterns formed on the inner layer and between the circuit pattern formed on the inner layer and the circuit patterns formed on both surfaces of the insulating substrate is performed by a pre-formed buried (embedding)
It can also be obtained through via holes and blind via holes. Further, a through hole for a through hole penetrating the insulating substrate is provided as necessary, and a conductive layer is provided on an inner wall of the through hole for a through hole to form a conductive through hole, thereby obtaining the electrical connection. You can also

It is important that the filled state of the cured body of the curable paste into the conductive through hole satisfies the following three conditions.

That is, (1) the conduction through hole is closed,
(2) Does not substantially project from the surface of the circuit pattern, and (3)
It is necessary to fill so as to form a depressed surface inside the edge of the conduction through hole.

A typical mode of the filling state according to FIGS. 1 (a), 1 (b) and 1 (c) is shown.

As described above, the filled state of the hardened body of the curable paste into the conductive through-hole is such that the conductive through-hole is closed by the hardened body of the curable paste, so that the solder is applied when the component is fixed through the conductive through-hole. Does not diffuse to the opposite surface, so that the amount of solder necessary for connecting components can be reliably maintained.

Further, since the hardened body of the hardenable paste does not substantially project from the surface of the circuit pattern, when fixing the parts,
The component is fixed to the surface of the circuit pattern in a stable state, and the amount of solder required for component connection during solder cream printing is easily controlled.

Furthermore, the amount of the hardened body of the curable paste is reduced by filling the hardened body of the hardenable paste so as to form a depressed surface inside the edge of the conductive through hole. Therefore, the residual stress in the cured body of the curable paste, which occurs due to the curing shrinkage of the curable paste, is reduced, and the stress acting on the conductive through-hole and the cured body of the curable paste is reduced. The adhesion of the conductive paste to the cured product is improved. Further, also in the manufacturing method described below, by removing the amount of the curable paste used and the removal amount when removing the cured body of the curable paste protruding to form the same surface as the circuit pattern, During the removal, the stress acting on the adhesive surface between the cured body of the curable paste and the conductive through-hole becomes small, and the decrease in the adhesive force due to the peeling of the cured body of the curable paste on the adhesive surface is suppressed. For this reason, the adhesion between the cured body of the curable paste and the conductive through-holes is improved, so that the occurrence of the defect of the cured body of the curable paste filled in the conductive through-holes is suppressed, and the component mounting The yield in time can be improved. Furthermore, by reducing the amount of the curable paste that is removed when the cured body of the curable paste that is projected is reduced, it is possible to efficiently produce a circuit board with less waste of the curable paste used.

Therefore, when the circuit board of the present invention is used, even when the surface mount component is mounted and connected to the upper part or the vicinity of the conductive through hole, the component can be mounted with high reliability and high yield.

Further, when the cured body of the curable paste is filled so as to form a surface that is depressed inward from the edge of the conductive through hole, considering the adhesive force between the cured body of the curable paste and the conductive through hole. , The characteristics of the curable paste,
Although it depends on the material of the insulating substrate, the plate thickness, the diameter of the through hole of the conductive through hole, etc., when the volume ratio of the cured body exceeds 99% with respect to the volume of the through hole portion of the conductive through hole, the residual stress in the cured body is increased. Becomes larger and the adhesive force is significantly reduced. Therefore, generally, the volume ratio of the cured body is 99% or less with respect to the volume of the through hole portion of the conductive through hole, and preferably, in order to suppress the amount of the curable conductive paste used,
It is preferably 90% or less.

Further, considering the stability of the blockage of the conductive through holes due to the cured body of the curable paste, the curing depends on the characteristics of the curable paste, the material of the insulating substrate, the plate thickness, the diameter of the through hole of the conductive through hole, etc. The minimum thickness t of the closed part of the cured product of the conductive paste is 1/100 of the thickness T of the insulating substrate.
If it is less than (t = T × 1/100), the blockage cannot be maintained due to the thermal shock at the time of mounting the component. Therefore, generally, the minimum thickness t of the blockage part of the cured body of the curable paste is 1/100 of the thickness T (t = T × 1/100) or more,
Considering the variation in the minimum thickness t of the closed portion of the cured product during manufacturing, it is preferably 10/100 (t = T × 10/100) or more. Therefore, when the cured body of the curable paste is filled so as to form the surface depressed inward from the edge of the conductive through hole, the volume ratio of the cured body is satisfied with respect to the volume of the through hole portion of the conductive through hole. In addition, it is preferable that the minimum thickness of the closed portion of the cured body of the curable paste is satisfied.

In the present invention, the curable paste to be filled in the above-mentioned conductive through-hole has a suitable fluidity at the time of filling, and a curable paste which is cured by heat or light energy can be particularly preferably used.

The curable paste is not particularly limited as long as it can be filled in the conductive through hole and can be fixed in the conductive through hole after curing. Specific examples of the curable paste include an inorganic filler or an organic filler, a cross-linking thermosetting resin such as an epoxy resin or a phenol resin as a binder component, and mixed with an organic solvent as necessary to form a paste. The known curable paste described above can be used without particular limitation. Further, in order to improve the reliability of the adhesion between the cured body of the curable paste and the inner wall of the conductive through hole, a cured body of the curable paste and the conductive through hole having similar thermal expansion coefficients are used. Preferably. The coefficient of thermal expansion of the cured product of the curable paste may be determined by appropriately selecting the resin as the binder component or the content of the filler in consideration of the coefficient of thermal expansion of the insulating substrate used.

In order to form a depressed surface inside the edge of the conductive through hole, the cured body of the curable paste is
This can be performed by adjusting the filling amount into the conductive through hole in consideration of the curing shrinkage rate of the curable paste.

The method of forming the surface of the cured body of the curable paste which is depressed inside the edge of the conductive through hole using the curable paste is not particularly limited, and a general circuit board manufacturing method is adopted. it can. Specifically, the conductive through-hole is filled with the curable paste by a general method such as screen printing, and the portion where the cured body of the curable paste protrudes from the circuit pattern is buffed. A method of polishing and removing by a mechanical polishing method such as is preferable.

In the present invention, since it is not necessary to fill the entire conductive through-hole with the hardened body of the curable paste, the amount of the curable paste used can be reduced as compared with filling the entire conductive through-hole. Further, it is possible to easily remove the hardened body of the hardenable paste protruding from the surface of the circuit pattern, and it is possible to reduce the amount of the hardened body to be removed. In particular, in the case where the diameter of the conductive through holes is large and the number of the conductive through holes is large, the above effect becomes remarkable.

In addition, in order to improve solder wettability at the time of connecting components, a common plating layer may be formed on the cured body of the curable paste and the circuit patterns on the front and back of the insulating substrate. The curable paste used in this embodiment is
Since sufficient adhesion strength can be obtained between the common plating layer and the cured body of the curable paste, gold, silver,
A known silver paste in which a crosslinkable thermosetting resin such as an epoxy resin or a phenol resin containing 20 to 60% by volume of a metal conductive powder such as copper, nickel or lead is mixed with an organic solvent as necessary to form a paste. A curable conductive paste represented by a paste or a copper paste that gives a cured body having conductivity after curing is preferable. When the curable conductive paste cured body is used as the curable paste cured body, chemical plating can be omitted in the formation of the common plating layer. The material of the plating layer is not particularly limited as long as it is a known conductive metal.

The formation of the plating layer is not particularly limited as long as the circuit pattern and the surface of the cured body of the curable paste are connected by the common plating layer. In general, the conductive layer on the front and back of the insulating substrate and the coating of the cured body of the curable paste are formed by the plating layer, and then the conductive layer is etched to form a circuit pattern, and the circuit is formed by the common plating layer. A mode in which the pattern and the surface of the hardened body of the hardenable paste are connected to each other, and the conductive layer and the hardened body of the hardenable paste are covered with a plating layer, and then the conductive layer is etched to form a circuit pattern. A mode in which the circuit pattern and the surface of the curable paste hardened body are connected by a common plating layer, and a plating layer is selectively formed on the surface of the circuit pattern and the curable paste hardened body Thus, a mode in which the circuit pattern and the surface of the cured body of the curable paste are connected by the common plating layer can be mentioned.

As the plating method used for forming the above-mentioned plated layer, generally, there are a chemical (electroless) plating method, an electroplating method, a combined chemical / electroplating method and the like.
The thickness of the plated layer is preferably such that unevenness in thickness does not occur. Generally, from the viewpoint of preventing thickness unevenness, 5
It is preferably 0 μm or less and 5 μm or more. Particularly preferably,
The thickness is 5 to 35 μm for easy pattern formation.

Usually, when the above-mentioned plated layer is formed on the cured body of the curable paste, the adhesion strength of the contact portion between the plated layer and the cured body of the curable paste becomes a problem. Since the hardened body of the curable paste forms a recessed surface inside the edge of the conductive through hole, the hardened body of the curable paste forms the same surface as the substrate surface, rather than the hardened body of the curable paste and plating. The contact area of the layers can be increased, and the adhesion strength between the cured body of the curable paste and the plating layer can be increased.

The method of 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. 2 and 3 may be used.

That is, as shown in FIG. 2, (a) the insulating substrate 1 having the conductive layers 10 on both sides is used, (b) through-hole through holes 5 are provided, and (c) through-hole through holes. 5, the conductive layer 3 made of a plated layer is formed on the surface of the conductive layer 10 including the inner wall of 5, and the conductive through hole 4 is formed.
(D) filling the conductive through holes with a curable paste,
Cured. At this time, as shown in FIG. 2, the shape of the cured body 11 of the curable paste is such that the vicinity of the edge of the conductive through hole 4 is the conductive layer 3 formed of the plated layer formed on the surface of the conductive layer 10 on both surfaces of the insulating substrate. It projects from the surface, and the vicinity of the central portion of the conduction through hole 4 is depressed.

(E) Next, the cured body 11 of the curable paste
The surface on which the protrusions are protruded is removed by polishing, and the surface formed by the cured body 11 of the curable paste and the conductive layer 3 formed of the plating layer formed on the surfaces of the conductive layers 10 on both surfaces of the insulating substrate is smoothed to form a flat surface. did.

(F) An etching resist 6 is formed on the surface of the flat surface, and (g) after that, etching is performed and the etching resist is peeled off to form the circuit pattern 2.
And the solder resist 7 is formed on the surface of the circuit board to obtain the circuit board of the present invention.

Further, as a method of forming a plating layer common to the hardened body of the hardenable paste filled in the conductive through holes and the circuit pattern, (a) to (e) of FIG.
Is performed to smooth the surface formed by the cured body 11 of the curable paste and the conductive layer 3 formed of the plating layer formed on the surfaces of the conductive layers 10 on both surfaces of the insulating substrate to form a flat surface. As shown, (e ') the flat surface and the surface of the hardened body of the curable paste filled in the conductive through holes 4 are coated with a common plating layer 8, and (f') the flat surface is etched. A resist 6 is formed, (g ′) is then etched, a circuit pattern is formed by peeling off the etching resist, and a solder resist 7 is formed on the surface of the circuit board to obtain the circuit board of the present invention. it can.

In the above method, as the insulating substrate 1,
Although not particularly limited, an insulating substrate having a conductive layer on the insulating substrate is generally used. The material of the conductive layer is not particularly limited as long as it has conductivity. Typical examples of the material include metal materials such as copper, nickel and aluminum. Specifically, it is most common to use a commercially available copper-clad laminate in which copper foils are laminated.

As the insulating substrate, the insulating substrate having a circuit pattern on the inner layer may be used.
A method for manufacturing an insulating substrate having a circuit pattern in the inner layer is not particularly limited, and generally, it is formed by a mass laminating method and a pin laminating method.

In the above method, as the method of forming the through hole 5 for through holes, known methods similar to those for manufacturing a normal circuit board such as drilling, punching, and laser processing are used without particular limitation.

In the above method, a typical method of forming the conductive layer 3 made of a plated layer is shown by a chemical (electroless) method.
The plating method, the electroplating method, the combined chemical / electroplating method and the like can be mentioned. The material of the formed plating layer is not particularly limited as long as it is a known conductive metal, but generally, the same material as the conductive metal such as copper used as the material of the conductive layer of the insulating substrate may be selected. preferable.

The method of filling the conductive through holes formed in the insulating substrate with the curable paste is not particularly limited, and a general method is adopted. Specific examples include a method of filling once or a plurality of times by a printing method, a method of press-fitting with a pair of front and back squeegees from both sides of the insulating substrate, and a method of filling with a roll coater or curtain coater. It is preferably used.

The curing of the filled curable paste is
It can be performed by heat or light energy, and specifically, a hot air curing furnace, a far infrared curing furnace, an ultraviolet curing furnace,
According to a known method such as an electron beam curing furnace, a material suitable for curing the curable paste may be appropriately selected and cured.

The hardened body 11 of the curable paste, which is filled and hardened in the conductive through-holes, near the edges of the conductive through-holes 4 by a general filling method as shown in FIG. It slightly projects from the surface of the conductive layer 3. Since this protrusion is removed in a later process, the smaller the better. Further, it is preferable to form a depressed surface to the extent that the central portion of the conduction through hole does not penetrate.

In the present invention, after the curable paste is hardened, the hardened body protruding from the surface of the conductive layer 3 is removed in order to smooth the surface of the conductive layer 3. The removing method is not particularly limited, and a known method such as a physical removing method or a chemical removing method is adopted without particular limitation. Specific examples include buff polishing and belt polishing.

When the conductive paste is filled with the curable paste, the surface of the curable paste is removed in advance so as to form the same plane as the conductive layer 3, and then the curable paste is cured, whereby the above grinding is substantially performed. Without doing so, it is possible to form a cured body that does not protrude from the surface of the circuit pattern and has a depressed surface. Specifically, after filling the curable paste, the surface of the curable paste is flush with the conductive layer 3 by means such as scraping off excess curable paste protruding from the surface of the conductive layer 3 with a squeegee. It can be carried out by curing after forming the structure.

The surface formed by the cured body 11 of the curable paste and the conductive layer 3 formed of the plating layer formed on the surfaces of the conductive layers 10 on both surfaces of the insulating substrate is smoothed to form a flat surface, and then the flat surface is formed. A circuit pattern is formed by forming an etching resist on and etching.

As the typical etching resist, a dry film, a resist ink, an electrodeposition photoresist, etc. may be used without limitation, and the type may be appropriately selected depending on the fineness of the pattern.

The etching method is not particularly limited, but a method usually used for circuit boards is used. As the etching solution, generally, a known aqueous solution of cupric chloride, ferric chloride, persulfates, alkali etchant or the like is adopted by appropriately selecting the type depending on the material of the etching resist.

The method for removing the etching resist is as follows.
Although not particularly limited, a method usually used for a circuit board is used. As the stripping solution, generally, the type is appropriately selected depending on the material of the etching resist, and a known aqueous solution such as sodium hydroxide and an organic solvent are adopted.

A solder resist is formed on the surface of the circuit pattern formed by the above method. The method of forming the solder resist is not particularly limited, but a method usually used for circuit boards is used. Specifically, a heat-curable or UV-curable solder resist ink is applied to a required portion of the solder resist on the substrate surface by a screen printing method and cured to form a solder resist, or a heat for exposure and development. After the curable or UV-curable solder resist ink is applied to the substrate surface by the screen printing method, roll coating method, spray coating method, etc., the resist ink in unnecessary portions of the solder resist is removed by exposure and development. After that, a method of curing and forming a solder resist is adopted.

In the method of forming the plating layer 8 common to the ground flat surface and the hardened body of the hardenable paste shown in FIG. 3, the circuit pattern formation and the solder resist formation are the same as those described above. Can be carried out.

The circuit board of the present invention can be formed into a multilayer circuit board by a build-up method in which conductive layers are sequentially formed on the surface of the circuit board via an insulating layer to form a multilayer structure.

[0058]

As can be understood from the above description, the circuit board of the present invention closes the conductive through hole, does not protrude from the surface of the circuit pattern, and is at least partially separated from the edge of the conductive through hole. Since the hardened body of the hardenable paste is filled so as to form the depressed surface inside,
Excellent adhesion between the hardened body of the curable paste and the conductive through-hole, stable component mounting on the conductive through-hole, and the curable paste to be used can be kept to a small amount, which is extremely economical. Is.

Further, by forming a plating layer common to the cured body of the curable paste filled in the conductive through holes and the circuit pattern, the solder wettability of the cured body surface of the curable paste is improved, Further, the reliability of component connection is improved.

[0060]

EXAMPLES In order to describe the present invention more specifically, examples will be given below, but the present invention is not limited to these examples.

Example 1 A circuit board was prepared by the method shown in FIG. 2 below.

(A) As the insulating substrate 1 having the conductive layer 10 having a thickness of 18 μm on both sides, a glass base epoxy resin copper clad laminate having a thickness of 1.6 mm is used, and (b) a diameter of 0.
A 4 mm through-hole through hole 5 was formed by drilling, and the surfaces of the conductive layer 10 and the through-hole through hole 5 were cleaned in the order of buff polishing, ultrasonic cleaning, and high pressure cleaning.

(C) A commercially available copper chemical plating bath is used to form a chemical plating layer having a thickness of 0.5 μm on the through holes 5 for through holes.
After forming it on the surface of the conductive layer 10 including the inner wall of
m electroplating layer is formed on the surface of the chemical plating layer to form a conductive layer 3 made of a plating layer, and a conduction through hole 4 is formed, and (d) a viscosity of 50 is set as a hardening paste in the conduction through hole 4. Poise commercially available thermosetting silver paste (PS-652, manufactured by Tokurika Ken Co., Ltd.) was used to fill by screen printing, and the silver paste was heated in a hot air drying oven to 80
It was dried and cured under the conditions of 4 ° C. for 4 hours and 150 ° C. for 2 hours. At this time, as shown in FIG. 2, the shape of the cured body 11 of the curable paste is such that the vicinity of the edge of the conductive through hole 4 is the conductive layer 3 formed of the plated layer formed on the surface of the conductive layer 10 on both surfaces of the insulating substrate. It projects from the surface, and the vicinity of the central portion of the conduction through hole 4 is depressed.

(E) Next, using the 600th buff,
The surface from which the cured body 11 of the curable paste is projected is removed by polishing, and the surface formed by the cured body 11 of the curable paste and the conductive layer 3 formed of a plating layer formed on the surfaces of the conductive layers 10 on both sides of the insulating substrate is removed. It was smoothed to form a flat surface.

(F) A dry film 6 (“Aquamer CF” 1.5 mil manufactured by Hercules Co., Ltd.) was laminated as an etching resist on the surface of the flat surface, exposed and developed to form an etching resist.

(G) After that, etching is performed with a cupric chloride etching solution, and a wiring pattern is formed by peeling off the etching resist. The thermosetting solder resist SR-31-made by Tamura Manufacturing Co., Ltd. is formed on the surface of the circuit board. S
“E” was applied by a screen printing method and cured at 120 ° C. for 10 minutes to form a solder resist 7.

The chip size 160 is attached to the pad formed on the conductive through hole of the circuit board produced by the above method.
8 (1.6 mm x 0.8 mm) surface mount parts for 200
When mounted individually, all surface mount components were mounted and connected well. Then, thermal shock test (-65 ° C 30 minutes ← →
After performing 100 cycles at 125 ° C. for 30 minutes, all the surface mount components did not fall off.

Example 2 (a) to (e) in Example 1 were carried out as a method of forming a plating layer common to the cured pattern of the curable paste filled in the conductive through holes and the circuit pattern. After smoothing the surface formed by the cured body 11 of the curable paste and the conductive layer 3 formed of the plating layer formed on the surfaces of the conductive layers 10 on both surfaces of the insulating substrate to form a flat surface,
A circuit board was prepared as shown in FIG.

(E ') A 0.5 μm-thick chemical plating layer was formed on the flat surface and the surface of the hardened body of the hardening paste filled in the conductive through holes 4 by using a commercially available copper chemical plating bath. After the formation, an electroplating layer having a thickness of 20 μm is formed on the surface of the chemical plating layer to form a conductive layer 3 composed of a plating layer formed on the surfaces of the conductive layers 10 on both surfaces of the insulating substrate and a cured body of a curable paste. Covering the common plating layer 8,
(F ′) A dry film 6 (“Aquamer CF” 1.5 mil manufactured by Hercules Co., Ltd.) was laminated as an etching resist on the surface of the common plating layer 8 and exposed and developed to form an etching resist.

(G ') After that, etching is performed with a cupric chloride etching solution, and the etching resist is peeled off to form a wiring pattern. The solder resist 7 is formed on the surface of the circuit board as a "thermosetting solder by Tamura Corporation". Resist SR-31-SE "was formed by a screen printing method and cured at 120 ° C. for 10 minutes.

The chip size 160 is attached to the pad formed on the conductive through hole of the circuit board produced by the above method.
8 (1.6 mm x 0.8 mm) surface mount parts for 200
When mounted individually, all surface mount components were mounted and connected well. Then, thermal shock test (-65 ° C 30 minutes ← →
After performing 100 cycles at 125 ° C. for 30 minutes, all the surface mount components did not fall off.

Comparative Example 1 (a) to (c) in Example 1 were carried out to form the conductive through holes 4, and then (d) and (e) were not carried out, but (f) and (g) were carried out. Then, a circuit board was prepared.

The chip size 160 is attached to the pad formed on the conductive through hole of the circuit board produced by the above method.
8 (1.6 mm x 0.8 mm) surface mount parts for 200
When they were mounted, 82 surface mount components could not be mounted and connected due to lack of solder amount. After that, when a thermal shock test (-65 ° C. 30 minutes ← → 125 ° C. 30 minutes, 100 cycles) was performed, 43 more surface-mounted components were dropped.

Comparative Example 2 (a) and (b) in Example 1 were carried out to form through holes 5 for through holes, and a commercially available product having a viscosity of 50 poise as a curable conductive paste was formed in the through holes for through holes. A thermosetting silver paste (PS-652, manufactured by Tokuri Kaken Co., Ltd.) was used to fill by screen printing, and the silver paste was dried and hardened in a hot air hardening oven under the conditions of 80 ° C. for 4 hours and 150 ° C. for 2 hours. . Cured body 9 of the curable conductive paste at this time
5 was formed so as to project from the surface of the conductive layer 10 as shown in FIG.

Thereafter, steps (f) to (g) were carried out without carrying out steps (d) and (e) in Example 1 to prepare a circuit board.

The chip size 160 is attached to the pad formed on the conductive through hole of the circuit board produced by the above method.
8 (1.6 mm x 0.8 mm) surface mount parts for 200
When mounted individually, the protrusions of the cured body of the curable conductive paste hindered stable fixing of the surface mount components, and 126 surface mount components were not mounted and connected. After that, when a thermal shock test (-65 ° C. for 30 minutes ← → 125 ° C. for 30 minutes, 100 cycles) was performed, 58 surface-mounted components were further dropped.

[Brief description of drawings]

FIG. 1 is a sectional view showing a typical embodiment of a circuit board of the present invention. FIG. 2 is a cross-sectional view showing a typical manufacturing process of the circuit board of the present invention. FIG. 3 is a cross-sectional view showing a typical manufacturing process of the circuit board of the present invention. FIG. 4 is a cross-sectional view showing a conventional example of the circuit board in Comparative Example 1. 5: is sectional drawing which shows the conventional example of the circuit board in the comparative example 2. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Circuit pattern 3 Conductive layer 4 Conductive through hole 5 Through hole through hole 6 Dry film 7 Solder resist 8 Plating layer 9 Cured body of curable conductive paste 10 Conductive layer 11 Cured body of curable paste

Claims (1)

[Claims] 1. An insulating substrate having circuit patterns formed on both sides thereof, through holes for through holes penetrating the insulating substrate are provided at locations where electrical connection between the circuit patterns is required, and the through holes. A conductive layer is formed on the inner wall of the through hole for use to form a conductive through hole, the conductive through hole is closed, does not protrude from the surface of the circuit pattern, and is at least partially depressed inside the edge of the conductive through hole. A circuit board, wherein the conductive through-hole is filled with a hardened body of a hardenable paste so as to form a surface.