JPS60233885A - Printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [I] Purpose of the Invention The present invention is to produce a through-hole plated copper-clad wiring board by drilling a hole in a copper-clad laminate and then depositing a thin copper film in the through-hole by electroless copper plating. The present invention relates to a printed wiring board manufactured by the so-called etched wheel method in which a circuit is formed by forming a circuit and then removing unnecessary copper other than the circuit by etching.

More specifically, (^) A mixture consisting of a saponified product of (1) an ethylene-acrylic acid copolymer and/or an ethylene-methacrylic acid copolymer and (2) an ethylene-vinyl acetate copolymer is heated at a temperature of 250°C or less. (B) A laminate made of conductive metal foil. This relates to a special lint wiring board that is characterized by electroless plating or electroless plating and electroplating on the through-hole portions of the board.Not only does it have good heat resistance, but it is also excellent as a highly flexible flexible board. The object of the present invention is to provide a printed wiring board with improved characteristics.

[TI] Background of the Invention Copper-clad laminates are mainly used as printed wiring boards, and the demand for them has been increasing in recent years. Conventionally, phenol resin-impregnated base materials and epoxy resin-impregnated base materials have been mainly used as copper-clad laminates.

However, pudding I based on these resin-impregnated base materials
- Wiring boards do not always have sufficient properties, such as the adhesive strength between the copper foil and the base material, dimensional stability, and electrical properties (particularly electrical properties after moisture absorption treatment). For these reasons, it has not been possible to fully satisfy the demands for higher density and higher reliability accompanying the recent development of the electronic industry, and a printed wiring board with higher performance has been desired.

As a method to improve properties such as heat resistance and dimensional stability, fibrous materials made of glass fibers such as glass paper, filaments and stable fibers, as well as glass fabrics, can be treated with phenolic resins or improved epoxy resin impregnated groups. material is appearing. However, even in these wiring boards, although dimensional stability, heat resistance, etc. can be improved to some extent by these inorganic fibrous materials present in the base material, temperature resistance, electrical properties, etc. Wood quality cannot be improved. Furthermore, because there is no good adhesive between these base materials and copper foil, the current situation is that improvements in the physical properties of the base material itself do not have sufficient improvement effects when molded into copper foil and laminates. . Furthermore, recently, the use of heat-resistant thermoplastic resins has been developed to improve the drawbacks of these thermosetting resins.

Polyimide or polyester resin is generally used as a base material for hybrid integrated circuit boards, but polyimide has drawbacks such as poor adhesion strength to copper foil and copper foil lifting due to solder reflow. On the other hand, polyester resin has poor water absorption and a large coefficient of thermal expansion at 20°C to 250°C, so it lacks through-hole connection reliability. Furthermore, during production, curing is sometimes carried out using a steam press at 170°C, which tends to reduce the adhesion between resins when multi-layered.

Furthermore, when these thermoplastic resins are used as a base material, the dimensional stability of the finished substrate is significantly affected by the conditions for thermal fusion or bonding with an adhesive.

Furthermore, due to residual stress in the adhesive layer, shrinkage occurs at high temperatures, causing bending, twisting, etc. In order to improve these problems, materials in which glass cloth, matte, or inorganic cloth of mm are interposed in the resin base material are used. However, because the adhesiveness and compatibility between the thermoplastic resin and glass fibers, which are essential requirements for printed wiring boards, is extremely poor, repeated bending causes peeling between the resin and glass fibers, resulting in breakage. This often causes damage to the circuit or destroys the circuit.

For these reasons, there is a demand for printed wiring boards that not only have good dimensional stability at high temperatures but also have excellent electrical properties, are highly reliable, and are inexpensive. As density increases, the number of layers is increasing.

In particular, when there are three or more layers, through holes are used to connect arbitrary conductor layers. For example, plated through-hole methods, additive methods, and multi-wire methods are used, and through-holes are also used for mounting electronic components, such as clearance methods and pin insertion methods.

In these through-holes, conductors are generally formed by plating, but there are problems with temperature resistance and adhesion strength, resulting in wire breakage and very low product yields. (insulating layer) is required.

In the method of manufacturing printed wiring boards (printed circuit boards), instead of the conventional etching method for copper-clad laminates, we apply additive technology to directly draw circuits on resin boards using electroless plating. Furthermore, a substrative method using a combination of this plating and etching method has come to be used. The reason why this additive method has become popular is that it is an effective method for simultaneously forming through-holes and pattern plating in resin laminates for high-volume, low-variety type resin laminates. Performance such as "Niji" is improved, and a high degree of fine line can now be obtained. Recently, a resistless method has also been developed in which ultraviolet rays are directly applied to a photoreaction catalyst mixed in the adhesive layer through a photomask to precipitate metal nuclei and electroless plating is performed.

l-Kashi, conventional paper used in these additive methods-phenolic resin, glass epoxy resin,
Polyimide resin substrates do not have good adhesion to the plating film, so blistering and peeling may occur, and the coefficient of thermal expansion in the thickness direction is large, so when thermal stress is applied, especially on fine pattern plating parts. Cracks often occur. Furthermore, when drilling holes in multilayer boards, smear occurs, which impedes the connection with the plating and reduces connection reliability. Furthermore, in the etching and scratching processes, large amounts of various aqueous solutions or washing water are used, so it is also an important condition that dimensional changes upon moisture absorption be small.

[m] Structure of the Invention Based on the above, the present inventors conducted various searches to improve these drawbacks in order to obtain a printed circuit board with good heat resistance and excellent electrical insulation properties, and as a result, ( A) A mixture consisting of saponified products of (1) ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and (2) ethylene-vinyl acetate copolymer; The mixing ratio of the acid copolymer and/or ethylene-methacrylic acid copolymer is 20 to 80% by weight, and the mixture is extruded into a thin shape at a temperature of 250° C. or lower under conditions that do not cause fish eyes. (B) Electroless plating or electroless plating and electroplating is applied to the through-hole portion of the laminate made of conductive metal foil to the crosslinked product obtained by heating and pressurizing the thin walled product at a temperature of 100°C to 400°C. The present inventors have discovered that a printed wiring board characterized by the above-mentioned characteristics not only has excellent flexibility, but also good durability, and also has excellent electrical insulation properties, and has thus arrived at the present invention.

[rV] Effects of the invention The printed circuit board obtained by the invention exhibits the following effects (characteristics) including its manufacturing process.

(1) Since no thermosetting resin adhesive such as epoxy resin is used, not only the adhesion process is omitted, but also there is no need for the cumbersome drying process that interferes with that process.

(2) Excellent electrical properties (for example, insulation, withstand voltage, and dielectric heavy junction performance).

(3) It has good heat resistance and can not only withstand temperatures of 250°C or higher, but can also be plated without electrolytic plating or without the use of adhesives by applying pressure at temperatures of 100°C or higher. Electrolytic plating and electroplating allow a conductive metal thin film to be well adhered to the through-hole portion and the substrate.

(4) Excellent flexibility.

(5) In particular, the flexible printed circuit board of the present invention is characterized in that the crosslinking process is performed at a relatively high temperature (200°C or higher) as described below, compared to the case where conventionally used polyimide films and polyester films are used alone. Therefore, it is considered to have excellent dimensional stability, has good adhesion to the plating layer even at high temperatures, has good adhesion, and has extremely few residual voids.

As described above, the printed circuit board of the present invention not only has good electrical properties such as insulation resistance and dielectric constant, but also has good dimensional stability, heat resistance, chemical resistance, moisture resistance, etc., and is also flexible. The bending durability of the substrate exhibits flexibility that has not been previously available. Furthermore, the adhesion with the conductive metal thin film due to the plating recipe is characterized by good adhesion up to relatively high temperatures (approximately 360° C.).

[V] Detailed description of the invention (A) Ethylene-acrylic acid copolymer and ethylene-
Methacrylic acid copolymer The ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer used in the present invention is prepared by combining ethylene and acrylic acid or ethylene and methacrylic acid at high pressure (generally 50 kg/cm or less). 5, preferably 10
0 kg/c rn' or more) in the presence of a free radical generator (usually an organic peroxide). The physical properties of each of these are well known. The copolymerization ratio of acrylic acid or methacrylic acid in these copolymers is 1 to 50% by weight, preferably 5 to 50% by weight.

If the copolymerization ratio of acrylic acid or methacrylic acid in these copolymers is less than 1% by weight, a uniformly thin product cannot be obtained. On the other hand, if it exceeds 50% by weight, the softening point will be too low, making handling and transportation inconvenient.

(B) Saponified product of ethylene-vinyl acetate copolymer,
The saponified ethylene-vinyl acetate copolymer used in the present invention can be obtained by saponifying (hydrolyzing) the ethylene-vinyl acetate copolymer. Hydrolysis is generally carried out using caustic soda in methyl alcohol. In producing the saponified product of the present invention, it is usually desirable to have a hydrolysis rate of 80% or more. The raw material ethylene-vinyl acetate copolymer is obtained by copolymerizing ethylene and vinyl acetate in the same manner as the ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer described above. be. The copolymerization ratio of vinyl acetate in this ethylene-vinyl acetate copolymer is generally 1 to 60% by weight, particularly 5 to 60% by weight.
Weight percent is preferred. If the copolymerization ratio of vinyl acetate in this copolymer is less than 1% by weight, a uniformly thin product cannot be obtained. On the other hand, if it exceeds 60% by weight, the softening point decreases and handling at room temperature becomes difficult.

Saponified products of these ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-vinyl acetate copolymers are industrially produced and used in a wide variety of fields, and we will discuss their manufacturing methods. is also well known.

(C) Mixing ratio The mixing ratio of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer in the mixture of the present invention is 20 to 80% by weight (i.e., ethylene-vinyl acetate copolymer The mixing ratio is preferably 80 to 20% by weight) -25 to 75% by weight, particularly 30 to 7% by weight.
0% by weight is preferred. If the proportion of the ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer in these mixtures is less than 20% by weight,
Since the number of carboxyl groups (-C:0OH) is smaller than that of hydroxyl groups (-OH), hydroxyl groups that do not contribute to the condensation reaction remain, resulting in poor heat resistance. on the other hand,
If it exceeds 80% by weight, on the contrary, there are too many carboxyl groups contributing to the condensation reaction, so that unreacted groups remain and heat resistance and moisture resistance are not improved, which is not desirable.

(Il)) Mixing method To produce the mixture of the present invention, the saponified products of the above ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer are uniformly mixed. This can be achieved by As a mixing method, tri-blending may be performed using a mixer such as a Henschel mixer, which is commonly used in the field of olefin polymers, or mixing may be performed using a mixer such as a Banbury mixer, kneader, roll mill, or screw extruder. It can be obtained by melt-kneading using a machine. At this time, a homogeneous mixture can be produced by tri-blending in advance and melt-kneading the resulting mixture. In addition, the carboxylic acid group (-COOH) possessed by the ethylene-acrylic acid and/or ethylene-methacrylic acid copolymer used for melt mixing and the hydroxyl group (-OH) possessed by the saponified product of the ethylene-vinyl acetate copolymer are ) essentially does not undergo a cross-linking reaction (lit reaction), and fish eyes remain raw.

(slight crosslinking may be allowed). From this, the melting temperature is the temperature at which the saponified products of these ethylene-acrylic acid copolymers and/or ethylene-methacrylic acid copolymers and ethylene-vinyl acetate copolymers melt, but the crosslinking reaction does not occur. (no fish eyes occur). The melting temperature varies depending on whether or not a crosslinking accelerator is added in the latter stage, as well as their type and amount; however, when no crosslinking accelerator is added, it is usually 18
The temperature is preferably 0°C or lower, particularly preferably 100 to 150°C. If the temperature is less than 100°C, these resins will not be completely melted, which is not preferable. On the other hand, when adding (blending) a crosslinking accelerator, the temperature is generally 140°C or less, and 1
The test is carried out at temperatures above 00°C.

In producing this mixture, stabilizers against oxygen, light (ultraviolet light) and heat, metal deterioration inhibitors, flame retardants, electrical property improvers and antistatic agents commonly used in the field of olefinic polymers are used. Additives such as lubricants, processability improvers, and tackiness improvers may be added to the extent that they do not impair the characteristics (physical properties) of the thin-walled product of the present invention.

9 Furthermore, by adding a crosslinking promoter such as an epoxy compound, P-toluenesulfonic acid, and AM-impropoxide, the ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene - Crosslinking of the vinyl acetate copolymer with the saponified product can be further completed. The amount added is usually at most 0.1 part by weight (preferably 0.01 to 0.05 part by weight) per 100 parts by weight of these resins.

(E) Production of thin material When the thin material of the present invention is used in the form of a film or sheet, it is widely used in the production of T-Guy film, which is commonly used in the field of thermoplastic resins, and the film 11 by the inflation method. A thin product can be obtained by extruding it into a film or sheet using a commonly used extruder. At this time, the extrusion temperature is 250°C or less. On the other hand, when extruded at temperatures exceeding 250°C, some of the saponified products of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer crosslink, forming a gel-like material. Due to the generation of small lumps, a uniform extrudate cannot be obtained. Based on these facts, the extrusion temperature was adjusted by adding a crosslinking accelerator (
The temperature range is the same as in the case of melt-kneading described above, regardless of whether the compound is added or not.

In any of the above cases, after manufacturing the thin-walled objects, the thin-walled objects with good transparency are made by rapidly cooling them in a water-cooling roll or a water bath to prevent adhesion between the thin-walled objects or between the thin-walled objects and a take-up roll. can get. The thickness of the thin-walled material thus obtained is from 3 microns to less than 5 mm, preferably from 10 microns to 1a+m, particularly preferably from 10 microns to 400 microns, taking into account flexibility and insulation.

(F) Heat/pressure treatment The thin-walled product obtained as described above exhibits the same behavior as a normal thin-walled product because crosslinking has hardly progressed. In order to impart adhesion and heat resistance to the conductive metal foil described below to the thin material, it is important to heat and pressurize it in the range of 100 to 400°C. 20 to 30 minutes when the heating temperature is in the range of 100 to 180 °C, 10 to 20 minutes in the range of 1130 to 240 °C, and 0.1 to 1 when the heating temperature is in the range of 240 to 400 °C
By heating and pressurizing the resin, a crosslinking reaction (condensation reaction) occurs within the resin, and the heat resistance is significantly improved.

Since the thin-walled article obtained by the present invention exhibits thermocompression adhesion (adhesiveness) at a temperature of 100° C. or higher, the effects of the present invention are further enhanced by bonding it to a conductive metal foil at the same time as the crosslinking treatment. That is, a mixture of an ethylene-acrylic acid copolymer and/or an ethylene-methacrylic acid copolymer and a saponified product of an ethylene-vinyl acetate copolymer is
The mixture exhibits thermoplasticity at temperatures below 160°C.
By subsequently subjecting the material to heat and pressure treatment, a crosslinking reaction occurs, and a laminate that adheres to the thin material and the metal foil and has excellent heat resistance can be obtained.

(G) Metal foil The thickness of the metal foil used in the present invention is generally 3 to 40 mm.
0 microns, preferably 3 to 100 microns, particularly 3 to 50 microns. As the metal of the metal foil, conductive metals such as copper, nickel, aluminum, silver, and gold, and alloys mainly composed of these metals are preferable, and in particular, conductive metals with a thickness of 15 to 4
0 micron rolled steel foil and electrolytic copper foil can be preferably used. Furthermore, with the recent increase in density, 3~1O
A micron metal foil has been developed, and this ultra-thin metal foil can also be suitably used.

(H) Electroless plating - generally known as electroless plating, i.e. chemical plating,
Nickel plating, highly corrosion resistant zinc/nickel alloy plating,
Copper plating is well known, but for printed wiring boards, it is best to use a combination of material (substrate) and plating film that has a uniform thickness on all surfaces that come into contact with the processing solution and that provides a dense plating film. Copper sulfate plating is usually put into practical use because it has excellent adhesion and ductility. According to this copper sulfate plating, it is possible to obtain a product having fine crystals, leveling (uniform thickness), stable workability, and excellent physical properties.

Generally, in copper sulfate plating, copper sulfate and sulfuric acid are used to supply metallic copper into the solution and improve the conductivity and uniform electrodeposition of the solution. Additionally, chloride ions (as a catalyst) and appropriate amounts of brighteners are used. Additionally, polyoxyethylene and polyoxypropylene derivatives may be used to enhance leveling. A typical composition is 5 to 40 g (7) of copper sulfate (CuSOa-5820) in an aqueous solution of 11.
and further p)! As a conditioning agent (buffer), for example, caustic soda (NaOH), ammonium chloride (NH
For example, EDTA-2Na (sodium salt of ethylenediaminetetraacetic acid) and formalin (HC:HO) are added as a reducing agent to prevent abnormal precipitation of copper in an aqueous solution. In addition, metals such as copper, nickel, and gold are electroplated on the conductive surfaces (paths) of these chemical (electroless) plated plates to protect the surface and prevent corrosion. It is also possible to apply solder.

(J) Circuit Formation Method There are various methods for manufacturing the printed wiring board of the present invention. A typical method is to drill a hole in a plate-shaped object laminated with copper foil, then form a thin copper film in the through hole by electroless copper plating, and then electrolytically plate the entire surface of the hole so that the inner wall of the hole meets the specified specifications. A panel plating method is used in which a metal key 1 is applied to the thickness of the copper plating, a plating material is applied, a circuit is formed using resist plating or an organic resist, and other unnecessary copper is removed by etching. After that, a copper foil film is applied to the through hole by electroless copper plating or electrolytic copper plating.
l! Next, leaving the pattern part and covering the rest with an organic resist, electrolytic copper plating is applied to the circuit part to a specified copper plating thickness, then electroplating is applied to resist etching, and then an organic resist is applied. A pattern plating method in which the resist is removed and the resist is used as an etching resist to dissolve and remove unnecessary copper by etching.
Furthermore, after forming through-hole plating using the same method as the panel plating method described above, a positive pattern is formed using an organic photosensitive film, the holes on both sides of the through-hole are sealed with this photosensitive film, and then etching is performed. Examples include the tenting method, which protects the plating of the through-hole holes from corrosion due to the intrusion of an etching solution when removing unnecessary copper foil, and through-hole plated printed circuit boards can be manufactured by these methods.

[Crosslinked product of a mixture consisting of saponified products of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer] (hereinafter referred to as rE-E resin) used in the present invention Because of the superior adhesion strength of electroless copper in the through-hole area and the plate, it is possible to achieve precision compared to copper-clad substrates such as ordinary glass-epoxy liquid, paper-phenol liquid, and even polyimide film and polyester film. Patterns are possible, and even when mass-produced, products with stable quality can be obtained. Furthermore, since the E-E resin is flexible, it is easy to drill holes, there is no occurrence of whiskers, and the thickness and precision of the plating can be made uniform. Furthermore, in fields that do not require flexibility, it is also possible to adopt a method of improving hardness and dimensional change by laminating an ordinary glass base fabric as an intermediate layer. These methods do not essentially reduce the adhesion of the electroless plating of the present invention.

CK) Printed wiring board The printed wiring board obtained by the present invention will be described below with reference to the drawings. The drawings shown below are representative examples of the etched wheel method, and it goes without saying that other methods such as panel plating, pattern plating, and tent etching can also be used.

FIG. 1 is an enlarged sectional view of a portion of a typical example of a double-sided copper-clad board. Further, FIG. 2 is an enlarged cross-sectional view of a portion of a typical example of a double-sided through-hole substrate in which an electroless copper plating film is formed on the portion where a hole is made for a through-hole. Further, FIG. 3 is an enlarged sectional view of a part of a typical example of a circuit board on which a so-called circuit is formed, after forming a positive pattern as shown in FIG. 2, etching is performed to remove unnecessary copper.

In FIGS. 1 to 3, 1 is a thin material made of E-E resin, and 2 is a copper foil. Further, 3 is a through hole portion, and 4 is a conductive metal film obtained by electroless plating.

[VI] Examples and Comparative Examples The present invention will be explained in more detail with reference to Examples below.

In addition, in the Examples and Comparative Examples, the heat resistance test was carried out using a substrate having the test pattern shown in UL 7!113 (Printed Wiring Board) 7.1 shown in Figure 7.1, which was held at 300°C. It was evaluated by floating it in a solder bath with a lead/tin ratio of 90,710 (weight ratio) for 180 seconds. The evaluation is shown in Table 1 as follows.

○: No change in the current form ×・Changes such as peeling, cracking, and splitting were observed between the conductor circuit and the resin layer Examples 1 to 4, Comparative Examples 1.2 Melt Flow Index (JIS) K-8760N, temperature is 190℃ and load is 2.18kg
Measured under the following conditions: rM, 1. J) is 300 g
100 parts by weight of ethylene-acrylic acid copolymer (density 0.954 g/cm', acrylic acid copolymerization ratio 20% by weight) and ethylene-acetic acid having a vinyl acetate copolymerization ratio of 28% by weight. Saponified product obtained by saponifying vinyl copolymer (saponification degree 8
7.5%, M, '1.75g/10min, density 0.951
g/cnf) was triblended for 5 minutes using a Henschel mixer. The obtained mixture E, hereinafter referred to as "mixture (A)", was transferred to an extruder equipped with a T-die (diameter: 40 LI 1 m, die width: 30 cm).
, the rotation speed is 85 revolutions/min), and the temperature of the cylinder is c1.
= ioo°C, C2 = 120°C and C3 = 140°C and the die temperature is 160°C.
(Examples 1 to 4, Comparative Examples 1 and 2). Also, instead of the ethylene-acrylic acid copolymer used in producing the mixture (A), M and T were added at 200 g/1
Ethylene-methacrylic acid copolymer (density 0.0 minutes)
950g/cm', methacrylic acid copolymerization ratio 25
The mixture [wt%] was used in the same manner as the mixture (A) except that
J, hereinafter referred to as "mixture (B)", was produced. A film was produced from the obtained mixture in the same manner as above (Example 4)
. Furthermore, the ethylene-acrylic acid copolymer (hereinafter referred to as rEAAJ) used in Example 1. Comparative Example l
) and a saponified product of ethylene-vinyl acetate copolymer (hereinafter referred to as "saponified product", Comparative Example 2) were used to produce a film in the same manner as described above.

Each film thus obtained was heated to 20 kg/cm' using a heat press for 10 minutes at 320°C.
Under pressure (gauge pressure), electrolytic copper foil (thickness: 17 microns) was adhesively laminated on both sides as shown in Figure 1, crosslinked (thickness is shown in Table 1), and both sides were laminated with copper foil. Created a board.

A through-hole hole with a diameter of 0.5mm and 1.0m+s was drilled in the obtained laminate using a drill, and the through-hole area was plated with an electroless copper plating solution having the following composition at 72°C to form a film. A copper plating film approximately 20 microns thick was produced.

Cu5Oa 5H2010g EDTA ・2Na Φ2H2030gHCHO(38
%) 3 mJL NaOH 12 g After completion of plating, the plate was washed with water and then dried.

Next, a circuit was formed by masking the circuit portion using a screen printing machine and etching away parts other than the circuit using a conventional method.

A heat resistance test was conducted on the obtained circuit-formed substrate.

The results are shown in Table 1.

Table 1 From these results, it was found that the printed wiring board obtained by the present invention not only has a very high circuit density, but also has excellent heat resistance and is a flexible, high-quality printed wiring board. fruit

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a portion of a typical example of a double-sided copper-clad board. Further, FIG. 2 is an enlarged cross-sectional view of a portion of a typical example of a double-sided through-hole substrate in which an electroless copper plating film is formed on the portion where a hole is made for a through-hole. Further, FIG. 3 is an enlarged sectional view of a part of a typical example of a circuit board on which a so-called circuit is formed, after forming a positive pattern as shown in FIG. 2, etching is performed to remove unnecessary copper. l... Thin wall of E-E resin. 2... Copper foil, 3... Through-hole portion, 4... Conductive metal film obtained by electroless plating Patent applicant Showa Denko K.K. Representative Patent attorney Sei Kikuchi - Figure 2, Figure 3 figure

Claims (1)

[Claims] (^) A mixture consisting of (1) an ethylene-acrylic acid copolymer and/or an ethylene-methacrylic acid copolymer and (2) a saponified product of an ethylene-vinyl acetate copolymer, The proportion of the ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer in the mixture is 20 to 80% by weight, and the mixture is mixed at a temperature of 250°C or less under conditions that do not cause fish eyes. A crosslinked product obtained by extruding into a thin shape and pressurizing the resulting thin product while heating at a temperature of 100°C to 400°C, and (B) electroless plating on the through-hole portion of a laminate made of conductive metal foil. Or a printed wiring board characterized by electroless plating or electroplating.