JPH07122853A - Manufacture of circuit board - Google Patents

Abstract

PURPOSE:To provide a simple method wherein, when an insulating pattern is formed in such a way that a part of a first wiring pattern is exposed, the first wiring pattern is not affected harmfully and the surface of the formed insulating pattern is roughened sufficiently. CONSTITUTION:A coating layer composed of a photosensitive insulating resin is formed on a wiring pattern 6 which has been formed on an insulating board 1, the surface of the coating layer is chemically etched and treated, the surface is roughened, the surface is exposed and developed, and at least a part of the wiring pattern 6 is exposed. When an insulating pattern is formed on the first wiring pattern 6 which has been formed on the insulating board and other layers are laminated additionally on the insulating pattern, a chemical roughening treatment to the surface of the insulating pattern is executed before the insulating pattern is formed by developing the coating layer composed of the photosensitive insulating resin. Thereby, it is possible to prevent the first wiring pattern 6 from being affected harmfully due to its etching, and it is possible to form an extremely good roughened face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring pattern formed on an insulating substrate (hereinafter, also referred to as a first wiring pattern).
The present invention relates to a novel method for manufacturing a circuit board in which an insulating pattern is formed so that at least a part thereof is exposed. More specifically, when an insulating pattern is formed on a first wiring pattern formed on an insulating substrate, and a wiring pattern (hereinafter referred to as a second wiring pattern) and the like are further laminated, a circuit board is manufactured. The present invention relates to a method for manufacturing a circuit board, which enables an insulating pattern having a high bondability with another layer to be formed by a simple operation and without adversely affecting the first wiring pattern.

[0002]

2. Description of the Related Art A multi-layer circuit in which a second wiring pattern is laminated via an insulating layer on a first wiring pattern formed on an insulating substrate for the purpose of increasing the circuit density and forming an electromagnetic wave shield layer. Substrates are known. As a method for manufacturing this kind of multilayer circuit board, after forming an insulating pattern on the first wiring pattern so as to expose a portion that needs to be connected to the second wiring pattern, such as a pad portion and a through hole portion, The method of forming the second wiring pattern on the insulating pattern has a high degree of freedom in routing the wiring pattern, and provides a multilayer circuit board with extremely high accuracy and high wiring density.
This is useful for reducing the substrate size and increasing the density.

In the manufacture of the above-mentioned multilayer circuit board, when the second wiring pattern is laminated on the first wiring pattern via the insulating pattern, the adhesion of the joint between the insulating layer and the second wiring pattern It is necessary to improve the reliability of the obtained multilayer circuit board.

Conventionally, as a means for improving such adhesion, a method of roughening the surface after forming an insulating pattern has been generally performed. The roughening treatment is typically slurry polishing, buff polishing, scrub polishing, etc.
Sufficient roughening effect cannot be obtained only by physical polishing, and good adhesion cannot be obtained.

Therefore, various chemical surface roughening treatments are carried out in addition to or independently of the above-mentioned physical surface roughening treatments. For example, a roughening treatment using a treatment agent such as chromic acid or permanganate, which is a desmear treatment liquid used when forming a plated through hole, has been performed together.

By the above-mentioned chemical roughening treatment, the surface of the insulating pattern is sufficiently roughened, and good adhesion with the second wiring pattern formed on the insulating pattern can be obtained. Become.

However, when the insulating pattern is chemically roughened, the first wiring pattern exposed from the insulating pattern is eroded or modified, and the electrical connection with the second wiring pattern is disturbed. Have the problem of

This problem is particularly caused when the first wiring pattern is formed by mixing a powdery conductive material such as copper or silver and a thermosetting resin and curing the curable conductive material in the form of a paste. This is remarkable in the case where the conductive through hole portion is filled with the cured body of the curable conductive material in the first wiring pattern.

That is, the resin portion of the cured body of the curable conductive material is easily eroded by the chemical roughening treatment of the insulating pattern.

[0010]

Therefore, according to the present invention, when the insulating pattern is formed so that the first wiring pattern is partially exposed, the insulating pattern is formed without adversely affecting the first wiring pattern. It is a technical object to provide a simple method for sufficiently roughening the surface of an insulating pattern.

[0011]

As a result of intensive studies to solve the above problems, the present inventors have found that a photosensitive insulating resin is formed on the surface of a circuit board having a wiring pattern made of a curable conductive material. After forming the coating layer and before exposing or developing the coating layer, the surface thereof is chemically etched to expose it from the insulating pattern.
The wiring pattern of can be protected from the etching process, a sufficiently roughened insulating pattern can be obtained, and the roughening does not hinder the development of the coating layer. Since the portion to be removed by the development is roughened before, it was found that the contact with the developing solution was good and the developing processing speed could be improved, and the present invention was completed.

That is, according to the present invention, after a coating layer made of a photosensitive insulating resin is formed on a wiring pattern formed on an insulating substrate, the coating layer is exposed and developed to expose at least a part of the wiring pattern. In manufacturing a circuit board having an exposed insulating pattern, the surface of the coating layer is chemically etched to roughen the surface of the coating layer before developing the coating layer. Is.

In the present invention, the insulating substrate 1 may be a known one without any particular limitation. Representative examples are: paper base material-phenolic resin laminated board, paper base material-epoxy resin laminated board, paper base material-polyester resin laminated board,
Glass substrate-epoxy resin laminated substrate, paper substrate-Teflon resin laminated substrate, glass substrate-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, metal such as aluminum, iron and stainless steel with epoxy resin and the like. Examples thereof include a metal-based insulating substrate or a ceramic substrate that is covered and insulated.

The wiring pattern formed on the insulating substrate is not particularly limited. For example, by printing a curable conductive material by a printing method, a wiring pattern formed by curing, a conductive layer made of a plating layer or the like is laminated on an insulating substrate, and the conductive layer is etched into a predetermined pattern. The formed wiring pattern and the like can be mentioned. Further, the wiring pattern may be formed not only on one surface of the substrate but also on both surfaces.

As the above-mentioned curable conductive substance, known materials can be used without particular limitation. For example, it provides a cured product having conductivity, and is made of gold, silver, copper, nickel, lead or carbon. Generally, a conductive material such as the above and a crosslinkable thermosetting resin such as an epoxy resin and a phenol resin are mixed with an organic solvent as necessary to form a paste. Further, the curing method of the curable conductive material, hot-air oven, infrared furnace, far infrared furnace, ultraviolet curing furnace, can be adopted without limitation known methods such as electron beam curing furnace, usually, curing A suitable method may be selected depending on the type of the conductive material.

The amount of the conductive material and each component to be mixed in the curable conductive substance should be adjusted so that the electric resistance after curing is 1 × 10 ⁻² Ω · cm or less in order to obtain good conductivity. Is preferred.

The material of the conductive layer may be any known material without particular limitation. For example, copper nickel, aluminum, etc. are typical. The thickness of the conductive layer is not particularly limited, but generally 5 to 70 μm is suitable.

When wiring patterns are formed on both sides,
Each wiring pattern is provided with a through hole for conduction at a place where connection is required, and the conductive portion is filled with the curable conductive material and is electrically connected by a conductive portion formed by curing, or a through hole for conduction is formed. A mode in which a plated layer is formed on the inner surface and electrically connected is preferable.

Among the above-mentioned wiring patterns, the embodiment in which the wiring pattern (including the through hole portion) is made of a curable conductive material is suitable when the present invention is applied, because the effect is remarkable.

FIG. 1 is a process chart showing an embodiment for carrying out the method of the present invention. A plating layer and a curable conductive material are filled in a conduction through hole and cured to form a through hole portion. FIG. 6 is a process chart showing a mode of forming an insulating pattern on the first wiring pattern.

In the above figures, the method of forming the first wiring pattern on the insulating substrate is specifically illustrated. (A) After the plating layers 2 are formed on both surfaces of the insulating substrate 1, (b) through holes for conduction. 3 is provided, (c) the curable conductive material 4 is filled in the through hole 3 for conduction and cured, and (d) the surface of the cured body and the surface of the plating layer are ground to be smooth, and (e)
There is a method in which the smoothed surface is covered with an etching resist 5 in a pattern corresponding to the wiring pattern, (f) etching is then performed to remove the exposed plating layer, and (g) the etching resist is removed. .

The diameter of the above-mentioned through hole 3 for conduction is not particularly limited, but is usually set to 0.2 mm or more, preferably 0.3 to 2 mm so that the curable conductive material can be easily filled. To do. As a method of forming the through hole for the through hole, a well-known method of forming a hole used in the manufacture of a circuit board such as drilling, punching, and laser processing can be used without limitation.

A curable conductive material 4 is filled and cured in the through hole. The filling of the curable conductive material into the through holes of the insulating substrate is usually such that the curable conductive material fills the entire space of the through holes and is slightly above both surfaces of the conductive layer, preferably at least 0.05 mm, It is preferably filled so as to project by 0.1 to 2 mm. Examples of suitable methods for filling the curable conductive material include 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 the insulating substrate, a roll coater or a curtain coater. And the like, and the excess curable conductive substance is scraped off with a squeegee.

Then, after the curable conductive material is cured, the portion of the cured body protruding from the substrate surface is ground smoothly. As a method for smoothly grinding the protruding portion of the cured body, a method generally used for ordinary polishing such as slurry polishing, buff polishing, scrub polishing, etc. is generally used.

As the etching resist,
A known etching resist can be used without limitation, and for example, a dry film, a resist ink or the like can 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 can be appropriately adopted depending on the etching method. For example, it is preferable to adopt a positive pattern in the etching method typified by the tenting method and a negative pattern in the etching method typified by the solder peeling method and the SES method.

In the present invention, an important requirement is that after a coating layer made of a photosensitive insulating resin is formed on the first wiring pattern formed by the various methods as described above, the coating layer is developed and predetermined. Before forming the pattern, that is, in the state where the entire surface of the insulating substrate including the first wiring pattern is covered with the photosensitive insulating resin, the surface of the coating layer is chemically etched.

That is, with this structure, the influence of the etching solution on the first wiring pattern can be almost completely prevented, and at the time of developing the coating layer, the contact with the developing solution becomes good, and the etching treatment is performed. It is also possible to improve the speed.

Further, the chemical etching does not generate heat on the surface to be roughened as compared with physical etching, such as sandblasting, and does not affect subsequent exposure or development processing.

The method of the present invention will be further described with reference to FIG. 1. (h) After covering the first wiring pattern 6 with a coating layer 7 made of a photosensitive insulating resin, (i) the coating layer is The processed surface 8 that has been roughened by being chemically etched before development is formed.

In this case, the etching treatment of the coating layer may be carried out before the exposure or after the exposure, as long as it is before the development.

In the present invention, the coating layer 7 can be formed by a method using a photosensitive insulating resin of various forms such as a dry film, a liquid resist, a dry film / liquid resist combination and the like. Among them, particularly in the case of using the dry film, the thickness accuracy of the coating layer is good and the front and back surfaces can be formed simultaneously, so that the coating layer can be formed more efficiently.

From the viewpoint of the insulation characteristics and long-term reliability of the insulating pattern obtained by treating the coating layer, it is preferable to use a photosensitive epoxy resin as the material of the photosensitive insulating resin.

The coating layer may be formed by appropriately selecting it according to the form of the photosensitive insulating resin using a known coating device such as a laminator using a heating roll, a screen printing machine, a roll coater and a curtain coater. it can. In addition, when the coating layer contains a solvent, it is preferable to sufficiently heat and dry it to remove the solvent.

In the present invention, the etching solution used for the chemical etching treatment is not particularly limited as long as it can etch the coating layer. Specifically, a desmear treatment liquid that has been conventionally used for forming plated through holes, such as chromic acid and permanganate, is preferably used.

Further, the degree of the above-mentioned etching treatment is performed so that the surface roughness Ra of the coating layer is 0.2 to 1, which is excellent for the second wiring pattern formed on the insulating pattern formed thereafter. It is preferable for achieving adhesion.

In the present invention, the above-mentioned exposure of the coating layer is preferably carried out under the condition that the surface of the coating layer subjected to the etching treatment is sufficiently cured.

Further, referring to FIG. 1, (j) the coating layer which has been subjected to the etching treatment is developed after the above-mentioned exposure to form a predetermined insulating pattern. Such an insulating pattern includes, for example, a via hole opening A for ensuring conduction between the first wiring pattern and a second wiring pattern formed later. After development, the insulating pattern can be heated and further cured, if desired.

In the present invention, after forming the insulating pattern, the second wiring pattern 10 is formed thereon.

That is, as shown in FIG. 1, it is general that (k) a plating layer is formed on the insulating pattern and then (l) it is etched by a known method.

In the above method, the second wiring pattern is not particularly limited, and examples thereof include signal lines, power supply lines, ground lines, electromagnetic wave shield layers, and other wiring patterns.
The method of forming the wiring pattern on the insulating pattern is not particularly limited, but for example, a method of forming by a printing method using a curable conductive material typified by copper paste, silver paste, etc., chemical plating, electroplating, etc. Then, a method of forming a plating layer on all the substrates including the insulating layer and etching the plating layer to form a pattern can be mentioned. However,
When the second wiring pattern is used as the outermost layer, it is necessary to mount an electronic component, and therefore a plating method is generally adopted. At this time, examples of the method of forming the plating layer include a method that employs only the chemical plating method and a method that uses both the chemical plating method and the electroplating method. The material of the plating layer is not particularly limited as long as it is a known conductive metal, but generally, the same material as the conductive metal used as a component of the curable conductive material, for example, copper or the like is selected. . The thickness of the plating layer is not particularly limited, but is usually 50 μm or less, preferably 5 μm to
35 μm.

Before the formation of the second wiring pattern, it is also preferable to carry out cleaning treatment such as pickling and ultrasonic cleaning for the purpose of cleaning the surface of the insulating pattern and the surface of the first wiring pattern. is there.

Further, in the present invention, an insulating pattern and a wiring pattern can be sequentially laminated on the second wiring pattern in the same manner.

Further, in the present invention, the obtained circuit boards may be laminated with a prepreg interposed therebetween to obtain a high multilayer structure.

[0044]

According to the method of manufacturing a circuit board of the present invention,
When an insulating pattern is formed on the first wiring pattern formed on the insulating substrate and another layer is further laminated on the insulating pattern, the surface of the insulating pattern is chemically roughened by photosensitivity. By carrying out before the formation of the insulating pattern by developing the coating layer made of an insulating resin, most of the adverse effects of etching on the first wiring pattern are prevented, and
It is possible to form a very good rough surface.

Therefore, another layer such as the second wiring pattern can be formed on the insulating pattern with high bondability and by a simple operation.

[0046]

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

Example 1 A curable paste that gives a cured product having conductivity was prepared by the following method, and a printed circuit board was manufactured. That is, average particle size 6.8 μm, tap density 2.99 g
/ Cm3, specific surface area 4200cm2 / g Dendritic electrolytic copper powder, linoleic acid to the copper powder surface 0.25 × 10-5m
The ingredients were blended at a ratio of mol / cm 2 and premixed in a mortar for 15 minutes under a nitrogen atmosphere. The pretreated copper powder thus obtained was mixed with neopentyl glycol glycidyl ether (epoxy equivalent = 150) / novolac type phenol resin (hydroxy equivalent = 105) = 74/26 (weight ratio).
456 parts by weight to 100 parts by weight of the binder, and 2.8 parts by weight of 2-ethyl-4-methylimidazole to 100 parts by weight of the binder, and then kneaded for 30 minutes with a three-roll mill. As a copper paste.

Subsequently, a circuit board was manufactured according to the steps shown in FIG.

(A) A 1.6 mm-thick glass substrate epoxy resin copper-clad laminate is used as an insulating substrate having conductive layers on both sides, and (b) a through hole 3 having a diameter of 0.4 mmφ is drilled. Provided by.

(C) The through hole 3 was filled with the copper paste prepared by the above method as the curable conductive material 4 by the screen printing method. The copper paste is heated in an electric furnace at 80 ° C. 6
It was cured under conditions of 0 minutes and 180 ° C. for 60 minutes.

(D) Next, the buffs of No. 320 and No. 600 were sequentially used to grind the surface of the hardened copper paste from which the hardened body protruded, and the surface of the conductive layer containing the hardened body was smoothed.

(E) Next, a dry film ("Aquamer CF" 1.5 mil manufactured by Hercules Co., Ltd.) was formed as an etching resist 5 on the smoothed conductive layer surface.
Was laminated, exposed and developed to form a resist pattern.

Thereafter, (f) etching was performed with a cupric chloride etching solution, and (g) the etching resist was peeled off to form the first wiring pattern 6.

Next, (h) a photosensitive insulating resin made of a photosensitive epoxy resin is applied to the entire surface of the first wiring pattern 6 including the through holes by a screen printing method and dried to form a coating layer 7 having a thickness of 40 μm. After the formation, (i) Securigant P manufactured by Nippon Schering Co., Ltd. was brought into contact with the surface of the insulating layer to roughen the entire surface. The average roughness of the insulating layer surface after the surface roughening treatment was Ra = 0.46 μm.

(J) Next, the coating layer 7 was exposed and developed to form an insulating pattern having an opening A for a via hole in the insulating layer, followed by heat curing. The time required for the development was 56 seconds.

(K) The surface of the substrate was subjected to chemical plating and electroplating to form a plating layer 9 having a thickness of 10 μm. As the chemical plating bath and the electroplating bath, unigant and Kaparaside GS manufactured by Nippon Schering Co., Ltd. were used, respectively, and the electroplating was performed under the condition of a current density of 5 A / dm ² . Then, (l) the second wiring pattern 10 was formed according to the steps (e), (f), and (g).

The second wiring pattern 10 located on the front and back of the obtained circuit board and connected to a common through hole.
As a result of measuring the resistance between them, it was 34 mΩ. Also, J
Thermal shock test of ISC-5012 (-65 ° C x 30 minutes ← →
50 cycles at 125 ° C for 30 minutes)
After the lapse of 0 times, no increase in the resistance between the second wiring patterns located on the front and back of the multilayer circuit board was observed, and
The adhesion between the wiring pattern and the insulating layer was good.

Comparative Example 1 A circuit board was manufactured by the steps shown in FIG.

That is, (a) to (h) are the same as in Example 1 shown in FIG. 1, and after forming the first wiring pattern 6 and forming the covering layer 7, (i) Exposure and development were performed under the same conditions as in Example 1 to form an insulating pattern having a via hole portion A, followed by heating and curing, and the time required for the above development was 61 seconds.

(J) The surface roughening treatment of the insulating pattern was performed in the same manner as in Example 1. The surface roughness of the roughened insulating pattern was Ra = 0.49 μm.

Then, as shown in (k) and (l) of FIG. 1, a 21st wiring pattern 10 was formed on the insulating pattern in the same manner as in Example 1.

The second wiring pattern 10 located on the front and back of the obtained circuit board and connected to a common through hole.
As a result of measuring the resistance between them, there was almost no continuity. It is presumed that this is because the hardened body of the curable conductive material filled and hardened in the through hole was eroded by the etching treatment after the formation of the insulating pattern, and the conduction on the surface was lowered.

Example 2 The first wiring pattern was formed by screen-printing the copper paste used in Example 1 on the surface of an insulating substrate and curing it at 180 ° C. for 60 minutes in an electric furnace.

Then, in the same manner as in (h) to (j) of FIG. 1 of the first embodiment, a coating layer is formed on the first wiring pattern, roughening treatment, exposure and development are performed. To form an insulating pattern. The roughness of the roughened surface is Ra = 0.44 μm, and the time required for development is 5
It was 5 seconds.

After that, as shown in FIG. 1 of the first embodiment, (k)
Similarly to (l), formation of a plating layer and etching were performed to obtain a circuit board.

The connection resistance between the respective layers of the obtained circuit board was measured and found to be 50 mΩ / hole or less. Also, JIS
Thermal shock test of C-5102 (-65 ° C x 30 minutes ← → 1
50 cycles at 25 ° C x 30 minutes)
After 0 times, no increase in resistance between the layers of the multilayer circuit board was observed, and the adhesion of the second wiring pattern was good.

[Brief description of drawings]

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

FIG. 2 is a process drawing of a circuit board obtained by a conventional method.

[Explanation of symbols]

 1 Insulating Substrate 2 Conductive Layer 3 Through Hole 4 Curable Conductive Material 5 Etching Resist 6 First Wiring Pattern 7 Insulating Layer 8 Rough Surface of Insulating Layer 9 Plating Layer 10 Second Wiring Pattern A Via Hole Opening

Claims (1)

[Claims] 1. An insulating structure in which a coating layer made of a photosensitive insulating resin is formed on a wiring pattern formed on an insulating substrate, and the coating layer is exposed and developed to expose at least a part of the wiring pattern. A method for producing a circuit board, characterized in that, when a circuit board having a pattern is produced, the surface of the coating layer is chemically etched to roughen the surface before the development of the coating layer.