JPH04206681A - Printed circuit board and surface processing method thereof - Google Patents

Abstract

PURPOSE:To improve the heat resistance property and solderability by forming a chemically formed film through contactness of a copper group wiring conductor surface with an imidazole compound substituted by 2-aryl group and with an aqueous solution including high fatty acid. CONSTITUTION:The surface of a printed circuit board including a copper group wiring conductor is placed in contact with an imidazole compound substituted by 2-aryl group expressed by the general expression (I) or (II) and an aqueous solution including at least a kind of a high fatty acid compound selected from a group of high fatty acid, ammonium salt of fatty acid and amine salt of high fatty acid. In this case, a weight ratio of imidazole compound is set to 0.01 to 5.0%. Thereby, a complex compound is formed through orientation of nitrogen atoms of imidazole to copper and an imidazole group preflux film is formed at the surface of a wiring conductor.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for surface treatment of a printed wiring board and a printed wiring board obtained by this surface treatment method, and is particularly suitable for a printed wiring board having a copper-based (copper or copper alloy) wiring conductor. The present invention relates to a surface treatment method that combines anti-corrosion treatment and pre-flux treatment to facilitate and ensure soldering when joining electronic components, etc., and a printed wiring board obtained by this surface treatment method.

[Prior art 1] Soldering of electronic components to a printed wiring board generally involves using pre-flux applied immediately after manufacturing the printed wiring board, and mounting various electronic components on the printed wiring board coated with this pre-flux. After surface mounting, post flux is used to solder the through holes. This pre-flux prevents oxidation by treating the copper conductor circuits of printed wiring boards made by etching copper-clad laminates to prevent rust, and also works with post-flux to prevent soldering of through-holes. It is a material for making highly reliable solder joints with high yield, and requires the following properties. ■It has good adhesion to copper foil, does not deteriorate or change in quality due to air, moisture, or other gases, and keeps the foil surface clean for a long period of time. ■Do not exhibit corrosive effects on copper or other metals used in electronic components. ■The preflux coating film should not become sticky or absorb dust or oil during storage. ■It has excellent compatibility with post flux and provides good solder wettability during soldering. - Easily removed by cleaning agent when cleaning printed wiring boards after soldering. ■Can be applied with a foam or brush, is less prone to defects such as pinholes and uneven coating, can be applied evenly, and dries quickly. Known prefluxes that are in practical use include resin-based prefluxes in which rosin or the like is dissolved in an organic solvent such as toluene, and imidazole-based prefluxes in which alkylimidazolium salts are dissolved in water. Conventional resin prefluxes include natural rosin, polymerized rosin, rosin ester, maleated rosin, hydrogenated rosin,
Terpene resin, phenol-modified terpene resin, etc. are dissolved in an organic solvent, and the carboxyl group of the organic acid (e.g. abietic acid) contained in the resin reacts with metallic copper and its oxides to produce soluble rosin soap. This prevents further oxidation of the copper surface. Since this resin-based preflux uses an organic solvent, it has an essential drawback in that its volatilization significantly impairs the working environment and safety. On the other hand, imidazole-based preflux is an aqueous solution of a salt of an alkylimidazole compound and an organic acid, and has excellent work safety.It also selectively forms a film only on the copper surface, so it has excellent preflux performance. It is excellent. The formation of a complex compound of aqueous 2-long chain alkylimidazole and copper on the copper surface is considered to be a factor in preventing copper oxidation. For example, Japanese Patent Publication No. 17046/1983 describes a surface treatment method for forming a film of a 2-long chain alkyl group-substituted imidazole compound on the surface of copper or copper alloy.
No. 48-11454. 48-25621, 4.9-1983, 49
-26183, 58-22545, 61-41
No. 988 and Japanese Unexamined Patent Application Publication No. 61-90492. Imidazole-based preflux is an excellent product that eliminates the problems of resin-based preflux, but as described below, it tends to deteriorate and stick when exposed to high temperatures, and it no longer decomposes. There was a fear that the action as a flux would be impaired and the cooperative action of the post-flux described above would be inhibited. [Problems to be Solved by the Invention] In recent years, electronic devices have become smaller, and surface mount devices (hereinafter referred to as SMDs), typically chip components, have become increasingly smaller.
ace Mount Device's W! 11) has come into widespread use. In surface mounting, when soldering electronic components, the SMD is first fixed with cream solder to a wiring board coated with pre-flux, and the cream solder is reflowed to join the SMD to the printed wiring board. Thereafter, the lead component is inserted into the through hole, post flux is applied, and then soldered, resulting in two-step soldering. SM
D is attached to both sides of the printed wiring board, and in some cases it is mounted on both sides, and the cream solder paste flow is applied to the surface of the printed wiring board.
This will be done twice on the back side. If soldering is carried out in such a process, the problem arises that the reflow process oxidizes the copper of the wiring conductor, changes the quality of the pre-flux, and makes the soldering with post-flux incomplete. It has become clear that resin-based prefluxes and imidazole-based prefluxes are insufficient. For example, a conventionally known imidazole-based preflux in which a chemical conversion film of a 2-long-chain alkyl group-substituted imidazole compound is formed on the sub-conductor circuit part can be used at room temperature to
Although stable soldering shows good properties up to about 0°C, when the temperature exceeds the reflow temperature of 240°C, the copper surface becomes discolored and the soldering properties are sometimes impaired. This is because there is a problem that the heat resistance of the 2-long chain alkyl group-substituted imidazole compound is low. The present invention aims to solve the above-mentioned conventional problems, and its first purpose is to provide an improved anti-rust protection treatment for wiring conductor circuits, which has high heat resistance and does not worsen the working environment. A second object of the present invention is to provide a method for surface treating a wiring conductor in a printed wiring board using a preflux, and a printed wiring board having an improved chemical conversion film surface-treated thereby. [Means for solving the problem] The action of conventional imidazole-based preflux is to apply an aqueous solution containing a 2-long chain alkyl group-substituted imidazole compound and an organic acid to the surface of copper or copper alloy (hereinafter referred to as copper-based). When brought into contact, a copper complex is locally formed due to a complex formation reaction between the 2-long chain alkyl group-substituted imidazole compound and copper, hydrogen bonding between the 2-long chain alkyl group-substituted imidazole compounds, and the creation of van der Waals forces. It is explained that a chemical conversion film of a 2-long-chain alkyl group-substituted imidazole compound is formed on the copper surface. On the other hand, the 2-aryl group-substituted imidazole compound according to the present invention is a conventionally known compound, but unlike the 2-long-chain alkyl group-substituted imidazole compound, it does not form the above-mentioned chemical conversion film. It's here. In view of these circumstances, the present inventors conducted various experimental studies and found that a 2-aryl group-substituted imidazole compound, a higher fatty acid, an ammonium salt of a higher fatty acid, and an amine salt of a higher fatty acid were added to the surface of a copper-based wiring conductor. It was unexpectedly discovered that when an aqueous liquid containing one or more selected compounds is brought into contact with the material, a chemical conversion film with excellent heat resistance can be obtained. The present invention has been made based on this knowledge, and means for achieving the object will be specifically explained below. (I) The surface of a printed wiring board having a copper-based wiring conductor is
-Aryl group-substituted imidazole compound, higher fatty acid,
A chemical film is formed on the surface of the copper-based wiring conductor by contacting it with an aqueous liquid containing at least one higher fatty acid compound selected from the group of ammonium salts of higher fatty acids and amine salts of higher fatty acids. This is achieved by a surface treatment method for printed wiring boards. The above 2-aryl group-substituted imidazole compound includes:
It is desirable that it is selected from at least one of the following general formulas (N and (■)). However, R is hydrogen or a methyl group, and R2 and R3 are any one selected from the group of hydrogen, methyl group, and phenyl group. Representative examples of the 2-, aryl-substituted imidazole compounds used in carrying out the method of the present invention include, for example, 2-phenylimidazole, 2-tolylimidazole, 2-phenyl -4-methylimidazole, 2-phenyl-4-benzylimidazole, 2,4.5-t-riphenylimidazole, 2-phenylbenzimidazole, etc. These imidazole compounds are, for example, water-alcoholic and water- It may be used as an aqueous system dissolved in a water-organic solvent mixture such as acetone, or formic acid, acetic acid, lactic acid,
It may be used as an aqueous solution after forming a salt of an organic acid or mineral acid such as propionic acid, glycolic acid, acrylic acid, and methacrylic acid. In addition, these imidazole compounds may be in the form of a homogeneous solution or a suspension, but for long-term auxiliary complex purposes, they are used as a homogeneous solution because of the uniformity of the chemical conversion film formed on the copper surface. It is preferable. Furthermore, the higher fatty acids used in carrying out the method of the present invention include straight chain fatty acids having 12 to 22 carbon atoms, straight chain monoenoic acids, synthetic fatty acids, etc. Typical examples include lauric acid, myristic acid, valmitic acid,
Examples include oleic acid. These higher fatty acids, singly or in combination, are selected from at least one of the following general formulas (r) and (IT) as explained in (I) above. (I) (II) However, it is desirable that R1 be hydrogen or a methyl group, and R2 and R3 be any one group selected from the group consisting of hydrogen, a methyl group, and a phenyl group. The above-mentioned 2-aryl group-substituted imidazol compounds include, for example, 2-phenylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole,
These are a mixed system of 2-phenyl-4-benzyl alcohols and a mixed system of water-acetones. Some of the higher fatty acids cannot be dissolved depending on the type of solvent, and in this case, they are used by self-emulsification or by emulsifying or suspending them with a suitable activator. To carry out the present invention, the surface of the wiring conductor must be polished, degreased,
After performing treatments such as soft etching and acid cleaning, wiring can be done by immersing the metal surface in a treatment solution, or by applying the treatment solution to the metal surface using an appropriate method such as brushing, spraying, or roller coating. It is desirable to bring the treatment liquid into contact with the conductor. In addition, during coating, the temperature of the treatment liquid is 2.
The temperature is preferably 0 to 60°C, and the higher the temperature, the thicker the deposited film tends to be. The second object of the present invention is as follows. (2) A printed wiring board having a copper-based wiring conductor, in which a chemically formed film of a 2-aryl group-substituted imidazole compound is formed on at least the surface of the copper-based wiring conductor,
achieved. The above can be used in combination with the above 2-aryl group-substituted imidazole compound. Higher fatty acids are involved in the film-forming properties during preflux film formation and the water repellency (moisture resistance) of the preflux film, and they may be added as fatty acids or as ammonium salts or amine salts. It's okay. Hereinafter, these higher fatty acids, higher fatty acid ammonium salts, and higher fatty acid amine salts will be referred to as higher fatty acid compounds. In carrying out the method of the present invention, the amount of the 2-aryl group-substituted imidazole compound added is suitably in the range of 0.01 to 5% by weight, preferably 0.1 to 2%, based on water or aqueous solvent. It is. The amount of higher fatty acids added is preferably equal to or less than the amount of the 2-aryl group-substituted imidazole compound added; if a large amount is used, the water repellency of the preflux film increases, but the heat resistance becomes inferior. In the present invention, examples of preferred solvents include water, water/methyl alcohol mixed solvent, water/ethyl alcohol mixed solvent, and water/isopropyl alcohol mixed solvent (4/6 each).
water-imidazole, 2,4.5-
It is preferable that the compound is composed of at least one selected from the group of triphenylimidazole and 2-phenylbenzimidazole, and this 2-aryl group-substituted imidazole compound forms a complex with the copper of the wiring conductor to form a chemical conversion film on the surface of the wiring conductor. covered. [Function] In the present invention, the 2-aryl group-substituted imidazole compound can be used in combination with higher fatty acids to improve the conventional 2-aryl group-substituted imidazole compound.
Similar to long-chain alkyl group-substituted imidazole compounds, a chemical film is formed on the surface of copper or copper alloy. Moreover, the imidazole-based preflux film formed according to the present invention has better heat resistance than conventional alkyl-based films, and this is thought to be due to the presence of aryl groups. The 2-aryl group-substituted imidazole compound forms a complex with the copper of the wiring conductor, and is coated on the surface of the wiring conductor as a chemical conversion film. That is, the nitrogen atom of imidazole coordinates with copper to form a complex compound, resulting in a chemical conversion film. [Examples] The present invention will be explained in more detail below using Examples and Comparative Examples. Examples 1 to 5 show examples of solder wettability tests, and the characteristic test conditions were all based on the same method as described below, so the characteristic test conditions will be explained in advance. The film thickness of the chemical conversion film in these tests is a reference value obtained by dividing the weight attached to a copper foil of a predetermined size by the surface area, assuming that the specific gravity of the film is 1 for convenience. Further, the solder wetting time was measured by the method shown below. First, a test piece (5 mm x 50 mm x 0.3 mm copper piece) was degreased with trichlorethylene, then soft etched, and then treated with various treatment solutions and heat treated, and immediately before measurement, it was coated as a post flag [Sanei Chemical Co., Ltd.]
rosin-based post flux, trade name JS-64]. This test piece was then tested using a solder wettability tester [Solder Checker-5AT-2000 manufactured by Resca Co., Ltd.].
The measurement conditions were as follows:
Solder temperature 240℃ 1 immersion depth 2mm, immersion speed 1
The speed was set at 6 mm/sec. Example 1 2-phenylimidazole 2 parts by weight, oleic acid 0.
1 part by weight, 20 parts by weight of methanol, and 80 parts by weight of water were stirred and mixed to prepare a 2-aryl group-substituted imidazole-based preflux solution of the present invention. The temperature of this solution was raised to 50°C, and the copper piece for the solder wetting test was immersed in it for 10 seconds, pulled up, drained, and dried at 100°C for 5 minutes to obtain a test piece. The chemical conversion and film thickness of the test piece thus obtained was 0.14 μm. Regarding the test piece of this example, immediately after forming the chemical conversion film, 9
After being left indoors for 6 hours, and after being left in an atmosphere of 65°C, 795% Rh for 96 hours, no heating and 20
Table 1 shows the results of the solder wetting test when air heating was performed at 0° C. for 10 minutes. Regarding solder wettability, the shorter the wetting time (in seconds), the easier it is to wet and the better the properties, and it can be seen that the solder of this example is superior to the comparative example. However, the numbers in [ ] in the table indicate the data of Comparative Example 1 Comparative Example 1 2-Undecylimidazole 1 part by weight and acetic acid 1.6
Parts by weight were dissolved in 100 parts by weight of water to prepare a conventional 2-alkyl group-substituted imidazole preflux solution. The temperature of this solution was adjusted to 50° C., and a copper piece for solder wettability testing was immersed for 20 seconds, taken out, washed with water and dried to obtain a test piece for comparison. The film thickness of this chemical conversion film is 0623
It was μm. The results of solder wettability evaluation in the same manner as in Example 1 are shown in [ ] in Table 1 above. Example 2 The same treatment as in Example 1 was performed except that 2-phenyl-4-methylimidazole was used instead of 2-phenylimidazole, and the chemical conversion and film thickness of the test piece were 0. .18 μm, and the results of evaluating its solder wettability are shown in Table 2. Similar to Example 1, good characteristics were obtained. Table 2, Solder wettability test results Example 3゜2-phenylimidazolium acetate 2 parts by weight,
Ammonium palmitate 0.2 parts by weight and water 1
00 parts by weight were stirred and mixed to prepare an imidazole preflux solution of the present invention. The temperature of this solution was raised to 40°C, and the copper piece for the solder wetting test was immersed in it for 30 seconds, pulled up, drained, and dried at 100°C for 5 minutes to obtain a test piece. The chemical conversion and film thickness of the test piece thus obtained were 0.
．． It was 22 μm. Regarding the test piece of this example, immediately after the chemical conversion coating was formed,
After being left indoors for 96 hours, and after being left for 96 hours in an atmosphere of 65°C and 95% Rh,
A solder wettability test was conducted when air heating was performed for 0" ClO minutes. The results are shown in Table 3, and good characteristics were obtained as in Example 1. Table 3 below shows the solder wettability test. Results Example 4 2 parts by weight of 2-phenylbenzimidazole, 0.1 part by weight of myristic acid, 60 parts by weight of methanol, and 40 parts by weight of water.
The imidasol-based preflux solution of the present invention was prepared by stirring and mixing the weight parts. This solution was heated to 45° C., and the solder wetting test copper piece was immersed in it for 10 seconds, pulled up, drained, and dried with a hair dryer for 30 seconds to obtain a test piece. The chemical conversion and film thickness of the test piece thus obtained were 0.0
It was 8 μm. Regarding the test piece of this example, immediately after forming the chemical conversion film, 9
After being left indoors for 6 hours and for 96 hours in an atmosphere of 65°C and 95% Rh,
Table 4 shows the results of the solder wetting test when air heating was performed at 0° C. for 10 minutes. In the case of no heating, the characteristics are not much different from those of Comparative Example 1, but in the case of heating, they are significantly improved. Table 4, Solder wettability test results Example 5゜2-phenylimidazolium acetate 2 parts by weight,
1 part by weight of acetic acid, 0.1 part by weight of lauric acid, and 1 part by weight of water
00 parts by weight were stirred and mixed, and further concentrated ammonia water was dripped until the pH of the liquid became 6.2 to prepare an imidasol-based preflux solution of the present invention. The temperature of this solution was raised to 50°C, the solder wetting test copper piece was immersed in it for 30 seconds, and after draining, it was heated to 100°C.
A test piece was obtained by drying for 5 minutes. The chemical conversion and film thickness of the test piece thus obtained was 0.28 μm. Regarding the test piece of this example, immediately after forming the chemical conversion film, 9
After being left indoors for 6 hours, and after being left for 96 hours in an atmosphere of 65°C and 95% Rh,
A solder wetting test was conducted when air heating was performed for 10 minutes at 0°C. The results are shown in Table 5, and as in Example 1, good characteristics were obtained. Table 5 below, solder wettability test results Example 6 In this example, the imidazole preflux of the present invention was used to surface-treat the wiring conductors on an actual printed wiring board.
An example will be shown in which a printed wiring board is obtained by forming a chemical conversion film. Hereinafter, a detailed explanation will be given using the drawings. FIG. 1 shows a manufacturing process diagram of a printed wiring board in which a wiring conductor is surface-treated with a treatment liquid containing a 2-aryl group-substituted imidazole of the present invention. FIG. 1(a) shows a cross section of printed wiring board 1 before surface treatment. In this method, a through hole 2 and a two-wire conductor pattern (not shown in this figure) are provided in advance on a double-sided mesh insulating substrate 5 by a well-known method, and then copper plating 4 is formed on the inner wall of the through hole and the wiring conductor pattern. It is manufactured by coating the board with solder resist 3 except for the runts 7 and through-holes used for connecting electronic components, and the printed wiring board can be processed equally whether it is rigid or flexible. becomes. As shown in Figure 1(b), the surface of the copper-plated conductor 4 is roughened with a soft etching solution, and as shown in Figure 1(c), the oxide film on the conductor surface is removed with an acidic solution, and then washed with water. Clean it. Furthermore, as shown in FIG. 1(d), the conductor surface of the printed wiring board is treated with an aqueous treatment liquid containing the 2=aryl group-substituted imidazole compound of the present invention and higher fatty acids. This treatment method includes immersing the printed wiring board in the processing liquid (dip method), applying a roller impregnated with the processing liquid to the printed wiring board (roller coater type), or spraying the processing liquid onto the printed wiring board. This is done by applying various treatment liquids, such as spraying (one-way spraying). Thereafter, the substrate is dried to evaporate moisture, and a chemical conversion film 6 is formed on the conductor surface such as the plating film in the land 7 and the through hole. Examples of specific surface treatments and treated printed wiring boards are shown below. A glass nipoxy copper through-hole substrate (substrate thickness 1.6 mm, through-hole diameter 0.8 mm, number of holes 105) having the structure shown in FIG. flux) at 50°C in the same manner as in the previous example.
was immersed for 30 seconds to form a chemical conversion film 6. This test printed wiring board was held at 65° C. and 95% Rh for 96 hours. Thereafter, air heating was performed at 210° C. for 10 minutes, and after cooling to room temperature, the JS-64 described above was applied with a brush as a post flux, and soldering was performed at 245° C. for 5 seconds. the result,
The copper-through-hole soldering rate was extremely high at 99% to 100%. On the other hand, in the case of Comparative Example 1, which used the conventional imidazole preflux, it was as low as 38% to 72%. Note that the copper-through-hole solder rise rate is expressed as a percentage of the number of through-holes in which the solder filled in the through-hole has a height of 90% or more, based on the total number of through-holes. Surface-mounted electronic components and lead components were mounted on the printed wiring board with the chemical conversion film 6 formed on the surface of the conductor by a well-known method. In the surface-mounted electronic component, the chemical conversion film 6 formed during the surface treatment effectively acted as a preflux, and highly reliable mounting characteristics were obtained. Also, for lead parts, post flux is supplied into the through holes,
We were able to achieve highly reliable mounting by inserting the leads into the through holes and making solder connections.

【Effect of the invention】

According to the method of the present invention, it is possible to form a chemical conversion film with excellent heat resistance mainly composed of a 2-aryl group-substituted imidazole compound on the surface of a copper-based wiring conductor. Soldering can improve performance.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for manufacturing a printed wiring board in which a wiring conductor is surface-treated with a treatment liquid containing a 2-aryl group-substituted imidazole according to the present invention. Explanation of symbols: 1.Printed wiring board, 2.Through hole, 3.
・Solder resist, 4. Copper plating, 5.. Insulating substrate, 6. Chemical conversion film, 7.. Runt.

Claims (10)

[Claims] 1. The surface of a printed wiring board having a copper-based wiring conductor is coated with a 2-aryl group-substituted imidazole compound and at least one higher fatty acid compound selected from the group of higher fatty acids, ammonium salts of higher fatty acids, and amine salts of higher fatty acids. A surface treatment method for a printed wiring board, comprising forming a chemical film on the surface of the copper-based wiring conductor by contacting it with an aqueous liquid containing the copper-based wiring conductor. 2. The above 2-aryl group-substituted imidazole compound is added to water or a mixed solvent of water and an organic solvent at a weight ratio of 0.
．． 2. The method for surface treatment of a printed wiring board according to claim 1, comprising the step of adding 0.01 to 5.0% to form an aqueous liquid and applying the aqueous liquid to the surface of the printed wiring board. 3. The above-mentioned 2-aryl group-substituted imidazole compound is selected from at least one of the following general formulas (I) and (II), ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc. ▼(II) However, R_1 is hydrogen or methyl group, R_2, R_
2. The method for surface treatment of a printed wiring board according to claim 1, wherein 3 is any one group selected from the group consisting of hydrogen, methyl group, and phenyl group. 4. 4. The method for surface treatment of a printed wiring board according to claim 1, wherein the higher fatty acid comprises at least one selected from the group consisting of lauric acid, myristic acid, palmitic acid, and oleic acid. 5. 3. The method for surface treatment of a printed wiring board according to claim 2, wherein the mixed solvent of water and an organic solvent comprises at least one of a water-alcohol type and a water-acetone type. 6. The above-mentioned 2-aryl group-substituted imidazole compounds include 2-phenylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-benzylimidazole, 2,4,5-triphenylimidazole and 2- The method for surface treating a printed wiring board according to any one of claims 1 to 3, comprising at least one member selected from the group of phenylbenzimidazoles. 7. Claim 1: When the surface of the printed wiring board having the copper-based wiring conductor is brought into contact with an aqueous liquid and a chemically formed film is formed on the surface of the copper-based wiring conductor, the temperature of the aqueous liquid is set at 20 to 60°C. The surface treatment method for the printed wiring board described above. 8. A printed wiring board comprising a printed wiring board having a copper-based wiring conductor, wherein a chemically formed film of a 2-aryl group-substituted imidazole compound is formed on at least the surface of the copper-based wiring conductor. 9. The above 2-aryl group-substituted imidazole compound is selected from at least one of the following general formulas (I) and (II), ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (II) However, R_1 is hydrogen or methyl group, R_2, R_
9. The printed wiring board according to claim 8, wherein 3 is any one group selected from the group consisting of hydrogen, methyl group, and phenyl group. 10. The above 2-aryl group-substituted imidazole compound is
At least one selected from the group of 2-phenylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-benzylimidazole, 2,4,5-triphenylimidazole and 2-phenylbenzimidazole The printed wiring board according to claim 8 or 9, comprising one type.