JPH04276691A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain sufficient electric insulation by preliminarily curing postcrosslinking type etching resist to form an etching resistant pattern layer corresponding to a wiring pattern, and then forming an insulating layer without peeling an etching pattern. CONSTITUTION:A postcrosslinking type heat resistant resist is filled in a through hole of a laminated substrate, preliminarily cured, a resist is printed in a wiring pattern on the board by screen printing, and preliminarily cured to form an etching resistant pattern layer 2. Thereafter, the conductive layer 2 is etched by using ferric chloride solution to form a wiring pattern 2'. Then, insulation resist is screen printed on a part except the through hole 7 of the pattern 2', a soldering pad 7 and a ground circuit 6, and cured to form an insulating layer 3-b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for manufacturing a printed wiring board in which a wiring pattern covered with an insulating layer is formed on the surface of an insulating substrate. Specifically, it is a method for efficiently forming a highly reliable insulating layer on a wiring pattern.

0002

2. Description of the Related Art In recent years, in printed wiring boards for digital equipment, the noise level generated by the printed wiring boards has increased as signal processing speeds have increased. Along with this, the Voluntary Regulation of Electromagnetic Interference (VCCI) has been strengthened, and an electromagnetic wave countermeasure wiring board in which the wiring pattern is covered with conductive copper paste via an insulating layer has been proposed.

FIG. 2 shows a typical structure of the above electromagnetic wave countermeasure wiring board. That is, the electromagnetic wave countermeasure board has the wiring pattern layer 2
An electromagnetic shielding layer 4 formed of a conductive paste that is electrically connected to the ground circuit 6 of the wiring pattern layer 2 is formed so as to cover the wiring pattern layer 2 via the insulating layer 3. formed and composed. Further, in the figure, 5 is a solder resist layer.

[0004] Conventionally, such electromagnetic wave countermeasure boards are generally constructed by forming an etching resist layer on the conductor layer of a laminated board that is constructed by forming a conductor layer on the surface of an insulating substrate, and then etching the conductor layer to form a circuit pattern. The manufacturing process includes a step of peeling off the etching resist, a step of forming an insulating layer, a step of forming an electromagnetic shield layer using conductive copper paste, and a step of forming a solder resist layer.

However, in manufacturing the above-mentioned electromagnetic wave countermeasure wiring board, in order to increase the reliability of the insulating layer 3 provided between the wiring pattern layer 2 and the electromagnetic shielding layer 4, it is necessary to increase the thickness of the insulating layer. However, the process of forming the insulating layer becomes complicated. That is, the method of forming an insulating layer on a wiring pattern formed by etching is usually performed by screen printing because of its good productivity and pattern formation. Since the thickness of the insulating layer formed by one printing process covering the wiring pattern is small, it is necessary to repeat the screen printing process and the curing process multiple times in order to ensure sufficient electrical insulation.

[0006]

[Problems to be Solved by the Invention] The present inventors have conducted repeated studies in order to establish a method for efficiently forming a reliable insulating pattern layer on the wiring pattern formed by etching the multilayer substrate. As a result, when etching a multilayer substrate to form a wiring pattern, the post-crosslinked etching resist is pre-cured to form an etching-resistant pattern layer corresponding to the wiring pattern, and then etching is performed to form the etching-resistant pattern. It has been discovered that this problem can be solved by subsequently forming an insulating layer without peeling, and the present invention has been completed.

[0007]

[Means for Solving the Problems] That is, the present invention provides (a) a layered substrate having a conductor layer on the surface of an insulating substrate, which is pre-cured with a post-crosslinked etching resist to form a desired wiring pattern; An etching-resistant pattern forming step of forming an etching-resistant pattern layer, (b) a wiring pattern forming step of etching the conductor layer exposed by the formation of the etching-resistant pattern, and (c) lamination except for the portions of the wiring pattern that need to be exposed. After forming an insulating pattern using a hardened layer of photocurable insulating resist on the substrate surface, an insulating pattern forming step of selectively peeling off the exposed etching-resistant pattern layer; and (d) removing the etching-resistant pattern layer. This is a method for manufacturing a printed wiring board, which includes a post-crosslinking step.

In the present invention, the insulating substrate constituting the laminated substrate may be made of known materials without particular limitations. For example, epoxy resin, phenolic resin, bismaleimide
Resin substrates made by impregnating glass reinforcing materials such as glass cloth, paper reinforcing materials such as linter paper and kraft paper with resins such as triazine resin and fluororesin; film substrates such as polyester films and polyimide films; surfaces covered with resin, glass, etc. Commonly used are metal substrates coated with insulating materials, ceramic substrates made of alumina, aluminum nitride, etc. Also,
Through holes are formed in the insulating substrate as necessary.

Further, in the present invention, the conductor layer on the surface of the insulating substrate is formed on the surface of the insulating substrate including the inside of the through hole. For the conductor layer, any known material may be used without particular limitation. Generally, metals such as copper, nickel, and aluminum are mentioned, and copper is particularly suitable. Such a conductor layer is generally manufactured by laminating and pressing a copper foil on the surface of an insulating substrate, by plating copper, or the like.

The post-crosslinked heat-resistant etching resist used in the process of forming the etching-resistant pattern of the present invention can be pre-cured, that is, cured without substantially three-dimensional cross-linking, and at the time of pre-curing. Any known resist material may be used without any particular restriction as long as it has the function of an etching resist and has electrical insulation properties after crosslinking. For example, epoxy resin-based curable compositions, acrylic resin-based curable compositions, epoxy/acrylic resin-based curable compositions, polyimide resin-based curable compositions,
From the composition of bismaleimide-triazine resin-based curable compositions, etc., one that satisfies the above characteristics may be selected and used. Among these, those that can be peeled off with an alkaline aqueous solution and have a carboxyl group introduced as a functional group are preferably used.

[0011] The form of the etching resist is not particularly limited. For example, liquid, dry film, etc. are common. Further, when preliminary curing of the etching resist is performed by exposure, negative type and positive type etching resists can be used without particular limitation. Such a type can be obtained by appropriately selecting a known photocurable material.

[0012] In the case of liquid etching resist,
Preferably, the precuring is performed by removing the solvent and the like until the product becomes non-sticky, if necessary, and curing to an extent that does not affect peeling with a stripping solution, followed by precuring. For example, when the epoxy/acrylic resin-based curable composition is used, preliminary curing can be performed by curing only the acrylic resin after removing the solvent.

In the present invention, as a method for forming an etching-resistant pattern layer corresponding to a wiring pattern, any known method using an etching resist may be employed without particular limitation. For example, when using liquid etching resist,
A mode in which an etching-resistant pattern is directly formed using the liquid etching resist by screen printing or the like and pre-cured, and a layer of the liquid etching resist is formed and pre-cured to form an etching-resistant pattern, and then the uncured portion is cured. A common method is to remove (develop) the image. Furthermore, when using a dry film etching resist, a common method is to laminate the dry film on a laminated substrate and then pre-cure and develop it to form an etching-resistant pattern.

In the wiring pattern forming step of the present invention, a wiring pattern is formed by etching the conductor layer in the portion of the multilayer substrate on which the heat-resistant etching pattern layer is formed, which is not covered with the pattern. As the etching method for the conductor layer, a known method may be employed as appropriate. For example, when the conductor layer is made of copper, it is preferable to use an aqueous solution of ferric chloride, cupric chloride, persulfates, hydrogen peroxide/sulfuric acid, or the like as an etching solution.

In the present invention, after the wiring pattern is formed, without peeling off the etching-resistant pattern, insulation is applied to the surface of the laminated substrate except for the portion where the wiring pattern needs to be exposed using a hardened layer of photocurable insulation resist. It is characterized by forming a pattern. That is, with this configuration, the etching-resistant pattern layer can be used as an insulating layer before forming the insulating pattern layer. This is the first
Since the etching-resistant pattern layer, which serves as an insulating layer, is formed on the smooth surface of the conductor layer, the thickness of the etching-resistant pattern layer is uniform, and it can be reliably formed on the wiring pattern. Compared to the conventional method of forming an insulating layer after pattern formation, it is now possible to form an extremely reliable insulating layer, and the resulting printed wiring board can be obtained without increasing the thickness of the insulating pattern layer laminated on top of the insulating layer. The reliability of the system can be significantly improved. It is particularly preferable to use a dry film to form the above-mentioned etching-resistant pattern layer, since this layer can be made thicker.

In the present invention, the parts of the wiring pattern that need to be exposed generally include through holes, conductive parts for soldering such as pads, and ground circuit parts.

The photocurable insulating resist used in the present invention is a known resist material that is not removed by the post-crosslinked etching resist stripping solution and has soldering heat resistance and electrical insulation properties. Appropriately selected from. For example, known curable compositions include epoxy resin-based curable compositions, acrylic resin-based curable compositions, epoxy/acrylic resin-based curable compositions, polyimide resin-based curable compositions, and bismaleimide-triazine resin-based curable compositions. What is necessary is to select a material having the above characteristics rather than a material having the composition. As the above-mentioned insulating resist, negative type and positive type can be used without particular limitation. Such a type can be obtained by appropriately selecting a known photocurable material. Furthermore, the form of the insulating resist is selected depending on the coating method, such as a liquid form or a dry film form.

The method for forming an insulating pattern layer using an insulating resist depends on the form, type, etc. of the insulating resist.
Known methods can be employed without particular restriction.

After forming the insulating pattern layer, the precured etching-resistant pattern layer exposed from the insulating pattern layer is peeled off. The stripping solution used for the stripping is a known stripping solution that does not strip the insulating pattern layer made of the cured product of the insulating resist, but can strip the etching-resistant pattern layer obtained by pre-curing the post-crosslinked etching resist. An appropriate one is selected from stripping solutions and used. As the above-mentioned stripping solution, for example, a method of stripping using a stripping solution such as an organic solvent or an alkaline aqueous solution is preferable. As the organic solvent, an organic solvent such as 1,1,1-trichloromethane or methylene chloride is generally used, and as the alkaline aqueous solution, an aqueous solution such as Na2CO3 or NaOH is generally used.

In the present invention, it is preferable to crosslink the cured material constituting the layer in a pre-cured state after peeling off the exposed portion of the etching-resistant pattern, as this can stably improve insulation reliability over a long period of time. . Such crosslinking conditions are:
Conditions are appropriately selected in which three-dimensional crosslinking of the etching resist occurs and the cured coating film has soldering heat resistance and electrical insulation properties. For example, when the epoxy/acrylic resin-based curable composition is used, crosslinking can be performed by heating at 140 to 160°C.

In the present invention, the total thickness of the etching-resistant pattern layer and the insulating pattern layer is not particularly limited;
Generally, 30 to 50 μm is suitable.

The printed wiring board obtained by the method of the present invention, in which an insulating pattern layer covering the wiring pattern layer is formed, has good insulation reliability over a long period of time.
For example, if an electromagnetic shielding layer made of a conductor such as a conductive paste is laminated on the surface, the shielding effect can be obtained without adversely affecting the operation of the wiring pattern.

[0023] As a method for forming the electromagnetic shield layer, any known method may be used without any particular limitation. For example, a common method is to form a continuous conductive layer using a conductive paste on the surface of the insulating pattern layer so as to be electrically connected to the ground circuit portion of the wiring pattern layer exposed from the insulating pattern layer. As such a conductive paste, a known copper paste can be used without particular limitation. An example of a typical copper paste is a conductive paste whose main components are copper powder as a conductive component, a binder component such as a resol type phenolic resin, and a reducing agent such as an unsaturated fatty acid such as oleic acid or its salt. Examples include copper paste. Further, in the present invention, any known method can be used without particular limitation as a method for forming a conductive layer using a conductive paste. Generally, printing methods such as screen printing are suitable.

Furthermore, a solder resist layer is formed on the surface of the conductive layer to protect the conductive layer. For forming such a solder resist layer, any known resist material may be used without particular limitation as long as it has solder heat resistance and electrical insulation properties after curing. For example, known curable compositions include epoxy resin-based curable compositions, acrylic resin-based curable compositions, epoxy/acrylic resin-based curable compositions, polyimide resin-based curable compositions, and bismaleimide-triazine resin-based curable compositions. A curable composition having the composition is used. As the solder resist, negative type and positive type may be used without any particular restriction. Such a type can be obtained by appropriately selecting a known photocurable material. Further, the form of the solder resist is selected depending on the coating method, such as liquid or dry film.

[0025] As a method for forming a solder resist layer using a solder resist, any known method may be employed without particular limitation, depending on the form, type, etc. of the solder resist.

[0026]

[Effect] As understood from the above explanation, according to the present invention, an insulating pattern layer is formed without peeling off the etching-resistant pattern layer formed on the wiring pattern used for forming the wiring pattern. , it is possible to maintain good insulation reliability of the insulating pattern layer for a long period of time. Moreover, it is no longer necessary to peel off the etching-resistant pattern layer formed by the etching resist, which was essential in the conventional process, and the number of insulation resist coating steps is reduced, so the manufacturing process of the intended printed wiring board can be simplified. will be significantly shortened.

[0027]

[Example] In order to explain the present invention more specifically,
Although examples and comparative examples are shown, the present invention is not limited to these examples.

[0028] Various tests in Examples and Comparative Examples were conducted by the following methods. (1) Through-hole connection reliability test Through-hole connection resistance of electromagnetic wave countermeasure wiring board
After 1000 cycles of a temperature cycle of 40° C./30 minutes←→125° C./30 minutes, the through-hole connection resistance change rate was determined. This operation was performed for each of 10 samples, and the through-hole connection resistance change rate was 10.
The number of sheets not exceeding % is shown.

(2) Electrical Insulation Test After the electromagnetic wave countermeasure wiring board was treated in a 95% atmosphere at 40° C. for 144 hours, an AC voltage of 1 kV was applied for 1 minute between the wiring pattern and the conductive layer made of conductive copper paste. This operation was performed on each of 10 samples, and the number of samples without dielectric breakdown is shown.

(3) Solder heat resistance test After immersing the electromagnetic wave countermeasure wiring board in organic acid flux,
It was immersed in a solder bath at 0 to 260°C for 5 seconds. This operation 1
After repeating each 5 times for 0 samples,
Observe the blistering and peeling of post-crosslinked heat-resistant etching resist layers, insulating layers such as coating layers made of photocurable insulating resists, conductive layers made of conductive copper paste, and solder resist layers, and count the number of sheets without blistering or peeling. It was shown in

(4) Measurement of radiation noise reduction effect The electric field strength of electromagnetic waves generated from the signal line of the electromagnetic wave countermeasure wiring board was measured using the open site 3m method. The radiation noise reduction effect was measured by measuring the attenuation from the measurement results of a normal double-sided wiring board in the frequency range of 20 to 1000 MHz.

Example 1 A printed wiring board was manufactured according to the process shown in FIG. (a) As the insulating substrate 1, a glass epoxy copper-clad laminate (“R-1700”: product name, manufactured by Matsushita Electric Works cm) with holes formed as through holes 7 for conduction is used, and the insulating A conductor layer 2 was formed on the surface of the substrate including through-holes by electroless plating and electrolytic plating treatment to obtain a laminated substrate. A post-crosslinked heat-resistant resist (“TGR-100”: trade name,
After filling with Taiyo Ink Seisaku cm) using a roll coater and pre-curing with an exposure amount of 1000 mJ/cm2,
Further, the resist was printed in a wiring pattern on the substrate by screen printing, and precured with an exposure dose of 1000 mJ/cm2 to form an etching-resistant pattern layer 2.

(b) After forming the etching-resistant pattern, the conductive layer 2 was etched using a ferric chloride solution to form a wiring pattern layer 2'.

(c) Next, an insulating resist ("TS-60
N": trade name, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was screen printed and cured with an exposure dose of 1000 mJ/cm2 to form an insulating layer 3-b.

(d) Next, as a stripper, 1% Na2
After peeling off the pre-cured etching-resistant resist layer exposed in the through-hole portion, soldering pad portion, and ground circuit portion of the wiring pattern using a CO3 aqueous solution, the etching-resistant resist layer on which the insulating pattern layer is laminated is removed. The patterned layer 3-a was post-cured at 160° C. for 30 minutes to obtain a printed wiring board of the present invention.

(Creation of electromagnetic wave countermeasure board) (e) Next,
A conductive copper paste ("NF-2000": trade name, manufactured by Tatsuta Electric Wire Co., Ltd.) is coated on the insulating pattern layer 3b of the above printed wiring board, and the layer is connected to the ground circuit portion 6 of the wiring pattern. Print and cure the conductive layer 4 to
was formed.

(f) Furthermore, a solder resist ("S-222": trade name, manufactured by Taiyo Ink Manufacturing Co., Ltd.) is applied by screen printing on the conductive layer 4 made of the conductive copper paste and cured. A resist layer 5 was formed. Various measurements and tests including a through-hole reliability test, an electrical insulation test, a soldering heat resistance test, and a radiation noise reduction test were performed on the electromagnetic wave countermeasure wiring board obtained using the obtained printed wiring board. The results are shown in Table 1.

Example 2 A printed wiring board of the present invention was manufactured in the same manner as in Example 1, except that steps (a), (b), (c), and (d) were performed in the following manner. After that, we obtained an electromagnetic wave countermeasure wiring board. (a) Glass epoxy copper clad laminate (“MCL-E-6
7" (trade name, manufactured by Hitachi Chemical Co., Ltd.), holes were formed to serve as through holes for conduction, and then electroless plating and electrolytic plating were performed to create a laminated substrate having through holes for conduction. After filling the through holes of the above laminated board with a monomer resist ink ("Value L1", product name, manufactured by DuPont Japan Co., Ltd.) using a roll coater, a dry film photo solder resist ("Value 8220V") was filled using a roll coater. '': trade name, manufactured by DuPont Japan Co., Ltd.) was laminated on the above substrate using a laminator. Subsequently, exposure and development were performed using a photomask corresponding to the wiring pattern to form an etching-resistant pattern layer.

(b) After forming the etching-resistant pattern, the conductive layer was etched using a ferric chloride solution to form a wiring pattern layer.

(c) Next, an insulating resist ("TS-91E") is applied on the multilayer substrate excluding the through-hole portions, soldering pad portions, and ground circuit portions of the wiring pattern layer.
: trade name, Taiyo Ink Manufacturing Co., Ltd.) was applied by screen printing and cured with an exposure dose of 600 mJ/cm2 to form an insulating pattern layer.

(d) Next, use a 3% NaOH aqueous solution to peel off the resist ink in the through holes of the wiring pattern, the dry film photo solder resist on the soldering pad portions and the ground circuit portion, and then heat at 160° C.6.
After curing for 0 minutes, a printed wiring board was obtained. Various measurements and tests including a through-hole reliability test, an electrical insulation test, a soldering heat resistance test, and a radiation noise reduction test were performed on the electromagnetic wave countermeasure wiring board obtained using the obtained printed wiring board. The results are shown in Table 1.

Example 3 An electromagnetic wave countermeasure wiring board was obtained in the same manner as in Example 1 except that steps (a), (b), (c) and (d) were carried out in the following manner. (a) Glass epoxy copper-clad laminate (“CCL-E17
0'': trade name, manufactured by Mitsubishi Gas Chemical Co., Ltd. After forming holes to serve as through holes for conduction, electroless plating and electrolytic plating were performed to create a laminated substrate having through holes for conduction. A liquid photoresist ("DSR-2200", trade name, manufactured by Tamura Seisakusho Co., Ltd.) is applied to the inside and surface of the through-holes of the laminated substrate using a roll coater, and heated at 80°C for 15 minutes to eliminate stickiness. After curing to 100%, pre-curing was performed using a photomask corresponding to the wiring pattern, and uncured portions were peeled off (developed) to form an etching-resistant pattern layer.

(b) After forming the etching-resistant pattern, the conductive layer was etched using a ferric chloride solution to form a wiring pattern layer.

(c) Next, insulating resist ("TS-90E": trade name, Taiyo Ink Manufacturing Co., Ltd.) is applied to the wiring pattern except for the through-holes, soldering pads, and ground circuits. Co., Ltd.) was applied by screen printing and cured with an exposure dose of 700 mJ/cm2 to form an insulating pattern layer.

(d) Next, using a 5% NaOH aqueous solution, the resist ink in the through holes of the wiring pattern layer, the pre-cured layer of liquid photoresist in the soldering pad area and the ground circuit area are peeled off. 150℃, 40
Post-cured in minutes. Various measurements and tests including a through-hole reliability test, an electrical insulation test, a soldering heat resistance test, and a radiation noise reduction test were performed on the electromagnetic wave countermeasure wiring board obtained using the obtained printed wiring board. The results are shown in Table 1.

Comparative Example 1 An electromagnetic wave countermeasure wiring board was obtained in the same manner as in Example 1 except that steps (a), (b), and (c) were carried out in the following manner. (a) Glass epoxy copper clad laminate (“R-1700”)
: (trade name, manufactured by Matsushita Electric Works Co., Ltd.)) after forming holes to serve as through holes for conduction, electroless plating and electrolytic plating were performed to create a substrate having through holes for conduction. Subsequently, hole-filling ink ("HC-25W", trade name, manufactured by Sanwa Kagaku Kogyo Co., Ltd.) was filled into the through holes of the substrate using a roll coater, and cured at 80° C. for 15 minutes. Next, dry film photoresist (“V
"ANX440": Product name, manufactured by Fuji Hunt Co., Ltd.) was applied onto the substrate using a laminator, and 8
Exposure was performed at a light intensity of 0 mJ/cm2. Subsequently, a wiring pattern was formed by etching using a ferric chloride solution.

(b) Next, the hole-filling ink and dry film photoresist on the wiring pattern were peeled off using a 5% NaOH aqueous solution.

(c) Next, the wiring pattern with the through holes, soldering pads, and ground circuits removed,
An insulating resist ("TS-60N": trade name, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was applied onto the substrate by screen printing, and cured with an exposure dose of 1000 mJ/cm2, and after repeating this operation twice. , heat curing was performed at 150° C. for 30 minutes. Various measurements and tests including a through-hole reliability test, an electrical insulation test, a soldering heat resistance test, and a radiation noise reduction test were performed on the electromagnetic wave countermeasure wiring board obtained using the obtained printed wiring board. The results are shown in Table 1.

Comparative Example 2 An electromagnetic wave countermeasure wiring board was obtained in the same manner as in Comparative Example 1, except that step (c) was carried out in the following manner.

(c) Next, the wiring pattern with the through holes, soldering pads, and ground circuits removed,
An insulating resist ("TS-60N", trade name, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was coated once on the substrate by screen printing, cured with an exposure dose of 1000 mJ/cm2, and then heated at 150°C for 30 minutes. Curing was performed. Various measurements and tests including a through-hole reliability test, an electrical insulation test, a soldering heat resistance test, and a radiation noise reduction test were performed on the electromagnetic wave countermeasure wiring board obtained using the obtained printed wiring board. The results are shown in Table 1.

[0051]

[Table 1]

[Brief explanation of the drawing]

[Figure 1] Diagram showing the steps of the manufacturing method of the present invention

[Figure 2] Cross-sectional view showing a typical aspect of the electromagnetic wave countermeasure board

[Explanation of symbols]

1 Insulating substrate 2, 2' wiring pattern layer 3 Insulating layer 3a Etching-resistant pattern layer 3b Insulating layer 4 Electromagnetic shielding layer 5 Solder resist layer 6　　　　　　　　Earth circuit part 7 Soldering pad part 8 Through hole part

Claims (1)

[Claims] Claim 1: (a) An etching-resistant method in which an etching-resistant pattern layer corresponding to a desired wiring pattern is formed by pre-curing a post-crosslinked etching resist on a laminated substrate having a conductor layer on the surface of an insulating substrate. Pattern formation process (
b) a wiring pattern forming step of etching the conductor layer exposed by the formation of the etching-resistant pattern; (c) forming a hardened layer of photocurable insulating resist on the surface of the laminated substrate excluding the portions where the wiring pattern needs to be exposed; A method for producing a printed wiring board, which comprises an insulating pattern forming step of selectively peeling off the exposed etching-resistant pattern layer after forming the insulating pattern, and (d) a step of post-crosslinking the etching-resistant pattern layer.