JPS61108546A - Printed wiring 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 [rI] Purpose of the Invention The present invention is directed to forming a conductive 11IW; This is a printed circuit board produced by the so-called full additive method, and is particularly suitable for the full additive method using photoresist. More specifically, (A) a mixture consisting of a saponified product of (1) ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and (2) ethylene-vinyl acetate copolymer at a temperature of 250°C or less (B) Metal vapor deposition is performed on the thin-walled product obtained by extruding the thin-walled product under conditions that do not cause fish eyes and heating and pressurizing the obtained thin-walled product at a temperature of 100°C to 400°C. This relates to a printed wiring board in which a conductor thin film or circuit of 200 microns or less is formed on the surface of the board, and the purpose is to provide a printed wiring board that not only has good heat resistance but also is highly flexible. It is.

[I! ] Background of the Invention Recent electronic devices are rapidly becoming smaller, lighter, thinner, and more densely packaged. In #1, printed wiring boards began to be commercialized for consumer equipment such as radios, and now, supported by mass production and high reliability, their use is expanding to industrial equipment such as telephones and computers.

In particular, flexible printed wiring boards were initially used as a substitute for electric wires and cables, but due to their flexibility, they can not only be mounted three-dimensionally at high density in a narrow space, but also can withstand repeated bending. Therefore, its use is expanding as a composite component that provides wiring, cable, and connector functions for the moving parts of electronic devices.

Currently, the materials used as three-dimensional wiring materials in devices such as cameras, electric desktop calculators, telephones, and printers are:
A wiring pattern is formed using a flexible copper-clad board in which electrolytic copper foil of 35 microns is adhered to both or one side of a polyimide or polyester film with a thickness of approximately 25 microns. A wiring pattern in which through-hole plating is applied, and both sides and the outer layer are coated with a coverlay is also used.

Current flexible printed wiring boards generally use polyimide or polyester resin films as the base material, but polyester resin has a high water absorption rate and
Since the coefficient of thermal expansion is large between 0℃ and 250℃,
Through-hole connection lacks reliability. Furthermore, during production, curing is sometimes carried out by steam press at 170° C., and when multi-layered, not only does the tIi adhesion between resins decrease, but also the flexibility tends to decrease.

On the other hand, polyimide film is soldered at the normal soldering temperature (26
It has the advantage that solder connection can be easily performed at temperatures above 0° C., but it has the disadvantage that it is extremely difficult to bond with metal foil due to poor surface activity. To solve this problem of adhesion, the general method is to apply a chemical treatment using caustic soda, a chromic acid mixture, aluminum hydroxide, etc. to the surface of the film, and then bond it with an adhesive. It is. However, even if these methods are used for adhesion, it is not possible to obtain a printed circuit board with sufficient adhesion, and the chemical resistance and heat resistance are poor. There are disadvantages such as occurrence.

In addition, thermosetting adhesives with excellent heat resistance (for example,
In the method of bonding with metal foil using epoxy resin,
It is necessary to overlap a polyimide film coated with an adhesive with a metal foil and heat and pressurize it in a press for about 1 to 20 hours to cure it, which poses problems in terms of productivity, mass production, cost, etc.

In the method of manufacturing printed wiring boards (printed circuit boards), instead of the conventional etching method for copper-clad AM boards, we apply plating technology to plastic to directly draw circuits on resin boards by electroless plating7. The dateative method and furthermore, the subtractive method, which combines this plating and etching method, have 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 for high-volume, low-mix resin laminates. The performance of
A highly 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.

However, the conventional paper-phenol resin, glass-epoxy resin, and polyimide resin substrates used in these 7-date methods do not have good adhesion to the plating film, resulting in blistering, peeling, etc. When ripening stress is applied due to the large coefficient of thermal expansion in the thickness direction,
In particular, cracks often occur in the plated parts of fine patterns. Furthermore, when drilling holes in multilayer boards, smear occurs, which impedes the connection with the plating and reduces connection reliability. Furthermore, in etching and plating processes, large quantities of various aqueous solutions or washing water are used, so it is also an important condition that dimensional changes upon absorption of moisture be small.

[I [1] Constitution of the Invention 1 In order to improve these drawbacks, the present inventors conducted various searches to obtain a printed circuit board with good heat resistance and excellent electrical insulation properties. result.

(A) (+) A mixture consisting of an ethylene-acrylic acid copolymer and/or an ethylene-methacrylic acid copolymer and (2) a saponified product of an ethylene-vinyl acetate copolymer, and the ethylene- The mixing ratio of the acrylic acid copolymer and /l or ethylene-methacrylic acid copolymer is 20 to 80%, and the mixture is made into a thin layer at a temperature of 250° C. or lower under conditions that do not cause fish eyes. extrusion, resulting thin-walled product)
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A printed wiring board obtained by applying (B) metal vapor deposition to a thin material obtained by applying heat and pressure to form a conductive thin film or circuit of 200 microns or less on the surface of the thin material has excellent flexibility and durability. The present invention was achieved by discovering that the material not only has good properties, but also has excellent electrical insulation properties.

[■ Effects of the Invention The printed wiring board obtained by the present invention, including its manufacturing process, exhibits the following effects (characteristics).

(1) Since no thermosetting resin adhesive such as epoxy resin is used, the adhesion process is not only omitted, but also
There is no complicated process (such as drying).

(2) Electrical properties (e.g. insulation, withstand voltage.

(dielectric loss tangent performance) is excellent.

(3) It has good heat resistance and can not only withstand temperatures of 250°C or higher, but can also be made conductive by vapor deposition without using the adhesive by applying pressure at a temperature of 100°C or higher. ? The IS film can be well adhered to the substrate.

(4) Excellent flexibility.

(5) In particular, the flexible printed circuit board of the present invention is characterized by the fact 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. Not only does it have excellent dimensional stability.

It has good adhesion to the vapor deposited layer even at high temperatures, has good adhesion, and has very few residual voids.

As described above, the printed wiring 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. The bending durability of flexible substrates shows flexibility that could not be obtained conventionally, and #ti adhesion with conductive metal thin films due to thin coating formulations is good even at relatively high temperatures (approximately 380°C) by thermocompression bonding. It has characteristics such as showing gender.

[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 under high pressure (generally, 50 kg/C or higher). , preferably 100
kg/c rn') 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 50iii%.

If the copolymerization ratio of acrylic acid or methacrylic acid in these copolymers is less than 1% by weight, it is impossible to obtain a uniformly thin walled product, while if it exceeds 50'@lid%, the softening point becomes too low. Handling and transportation become 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 that the hydrolysis rate is 80% or more. The combination is obtained by copolymerizing ethylene and vinyl acetate in the same manner as the above-mentioned ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer. The copolymerization ratio of vinyl acetate in this ethylene-vinyl acetate copolymer is generally 1 to 80 percent, particularly 5 to [1
Ofi! ! 1% is preferable. If the copolymerization ratio of vinyl acetate in this copolymer is less than 111% by weight, it is impossible to obtain a uniformly thin walled product. On the other hand, if it exceeds 60% by weight, the softening point decreases and handling at room temperature becomes difficult. becomes difficult.

1 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 range of fields, and their manufacturing methods are It is also well known.

CC) 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 80-20% by weight), 25-75% by weight, particularly 30-70%
% by weight is preferred. If the mixing ratio of ethylene-acrylic acid copolymer 8 and/or ethylene-methacrylic acid copolymer 8 and/or ethylene-methacrylic acid copolymer in these mixtures is less than 20%i%, the number of carboxyl groups (-COOH) is lower than the number of hydroxyl groups (-
OH), hydroxyl groups that do not contribute to the condensation reaction remain, resulting in poor heat resistance. On the other hand, 80
If it exceeds % 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.

(0) 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 a mixer such as a Banbury mixer, Niegoo, roll mill, and screw extruder. It can be obtained by melt-kneading using. 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 (-Coo) l) possessed by the ethylene-acrylic acid and/or ethylene-methacrylic acid copolymer used for melt mixing and the hydroxyl group (-Coo) possessed by the saponified product of the ethylene-vinyl acetate copolymer. -OH) does not undergo a crosslinking reaction (condensation, reaction) in a woody manner, and it is necessary that fisheye do not occur ((!1) may also be crosslinked). From this, the melting temperature of these ethylene- This is the temperature at which the saponified product of acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer melts, but at a temperature at which no crosslinking reaction occurs (no fish build-up occurs). 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
0°C or lower, particularly preferably 100 to 150°C. Below 100°C, these resins are not completely melted and are not preferred. On the other hand, when adding (blending) a crosslinking accelerator, -. is below 140℃,
It is carried out at a temperature of 100°C or higher.

In producing this mixture, an element commonly used in the field of olefin polymers.

Additives such as light (ultraviolet) and heat stabilizers, metal deterioration inhibitors, flame retardants, electrical property improvers, antistatic agents, lubricants, processability improvers, and tack improvers can be added to the thin film of the present invention. It may be added as long as it does not impair the properties (physical properties) of the product.Furthermore, by adding crosslinking accelerators such as epoxy compounds tp-)luenesulfonic acid and ^-impropoxide, ethylene - The crosslinking between the acrylic acid copolymer and/or the ethylene-methacrylic acid copolymer and the saponified product of the ethylene-vinyl acetate copolymer can be further completed. The amount added is usually at most 0.1 parts by weight (preferably 0.01 to 0.05 parts by weight) per 100 parts by weight of these resins.

(E) Production of thin-walled products When the thin-walled products of the present invention are used in the form of a film or sheet, T-Guy film, which is commonly used in the field of thermoplastic resins, is widely used when producing films by the inflation method. A thin product can be obtained by extruding it into a film or sheet using a conventional extruder, at an extrusion temperature of 250°C or less. Karini, 25
When extruded above 0°C, some of the saponified products of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer crosslink,
Due to the generation of small gel-like particles, a uniform extrusion molded product cannot be obtained.For these reasons, the extrusion temperature is set at the same temperature as the above-mentioned melt crosslinking temperature, regardless of whether a crosslinking accelerator is added (compounded) or not. Same temperature range as in case.

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 material obtained in this way is from 3 microns to less than 5-1, and in consideration of flexibility and insulation, the thickness is preferably from 10 microns to 1 inch, and particularly preferably from 10 microns to 400 microns. .

CF) Heating and 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 the above-mentioned heat resistance to the thin-walled product. 100-400
It is important to heat and pressurize in the range of °C. When the heating temperature is in the range of 100 to 180°C, 20 to 30 minutes, 180
10-20 minutes in the range of ~240℃, 240-400℃
In this range, by heating and pressurizing for 0.1 to 10 minutes, a crosslinking reaction (condensation reaction) occurs within the resin, and the heat resistance is significantly improved.

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 exhibits thermoplasticity at a temperature of 250°C or lower; By carrying out pressure treatment while heating at a temperature above .degree. C., a crosslinking reaction is effected, and a laminate with excellent heat resistance can be obtained.

(G) Vapor-deposited metals can be vapor-deposited using commonly used resistance heating, electron beam heating, induction heating, thermal radiation heating, vacuum heating vapor deposition, or sputtering. ,aluminum,
Examples include metals such as gold, copper, nickel, and platinum, as well as alloys containing these as main components (50% by weight or more) (for example, stainless steel), especially for use in microcircuits.

Platinum and gold are often used, but when a circuit is formed by etching after forming a thin film, copper, aluminum, and alloys containing these as main components are preferably used.

The thickness of the deposited conductor thin film can be freely selected depending on the conditions of the equipment used, but it is usually 100A (
Angstroms) to 100 microns, particularly IGOOA to 20 microns.

Furthermore, copper, nickel,
It is also possible to electroplate a metal such as gold to protect the surface and prevent corrosion, or to apply solder on the conductive path through a solder bath.

(H) Circuit Formation Method It is also possible to use the so-called full additive method in which a circuit is formed by vapor deposition on the surface of the thin material and the inner surface of the through-hole by vapor deposition carried out in the present invention. Another feature is that an etching process can also be used. Generally, the insulating material used in the fully additive method is one coated with an adhesive on one surface. "thin material obtained from a mixture consisting of an acid copolymer and a saponified product of ethylene-vinyl acetate copolymer" (hereinafter r
"E-E thin material") can be used without using Jli adhesive.
Excellent adhesion to deposits. Furthermore, it is possible to form conductor circuits by common circuit forming methods, such as cutting E-E thin materials to specified dimensions and drilling holes (punching method, drilling method, and pressing method). Then, the pattern is formed by screen printing with a negative pattern or by removing unnecessary parts with a photosensitive agent. By vapor-depositing this masked E-E thin film, a pattern is formed by forming a gold mR deposited film of a specified thickness on the unmasked circuit portion. Excellent alkali resistance is a necessary condition for long-term immersion in mask printing.

Normally, a layer that serves as both a photosensitive agent and an adhesive used in the commonly used full additive method is formed, and by exposing this calendar to light, only the circuit portion is bonded and
Efforts have been made to form a layer that is easy to form an M film. However, in the printed wiring board of the present invention, there is no need to use these, and since the directly vapor-deposited metal film layer is formed with good adhesion and adhesion on the surface of the E-E thin object, it is suitable for mass production. Not only are there defects (
There is no occurrence of whiskers or pattern breakage, and it is possible to form M-dense circuits. After vapor deposition, it is also possible to plate with gold, tin, solder, etc. for corrosion prevention for circuit protection and further for molding IC chips.

For the printed wiring board of the present invention, any of the fully additive adhesive printing method, adhesive photography method, and Iff contact method can be used.

The feature is that the iI′r tangent method can also be performed.

(J) Printed Wiring Board The printed wiring and board obtained by the present invention will be explained below with reference to the drawings. 1 to 3 are enlarged cross-sectional views of representative examples of the manufacturing process of the printed wiring board of the present invention by the direct method among the full additive methods. It should be noted that it is of course possible to manufacture in the same manner using other adhesive printing methods and adhesive photography methods.

The ERI diagram is an enlarged cross-sectional view of a portion of a typical example of a double-sided through-hole board in which areas other than circuit formation are masked using a negative method. Further, FIG. 2 is a partially enlarged sectional view of a typical example of a double-sided through-hole substrate in which metal vapor deposited films are formed on both sides and through-hole portions. Further, FIG. 3 is an enlarged sectional view of a part of a typical example of a substrate on which a so-called circuit is formed, with masked portions removed. In each of Figures 1 to 3, l is an E-E thin material (a mixture consisting of a saponified product of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer and ethylene-vinyl acetate copolymer). 2 is the through-hole part obtained from 1. 3 is a resist material, and 4 is a conductive metal thin film obtained by vapor deposition.

[1 Example and Comparative Example Hereinafter, the present invention will be explained in more detail with reference to Examples.

'In addition, in the Examples and Comparative Examples, the heat resistance test was carried out by testing the obtained film on a board with the test pattern shown in UL 79B (Printed Wiring Board) 7.1.
Evaluation was made by floating for 180 seconds in a solder bath with a lead/tin ratio of 90,710 (weight ratio) held at 00°C. 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-off, low index (JIS K -87[10
Measured under the conditions of temperature 180°C and load 2.18, hereinafter rM, 1. J) is 300
g / 10 minutes of ethylene-acrylic acid copolymer (
A saponified product obtained by saponifying an ethylene-vinyl acetate copolymer having a density of 0.1154 g/c rn' and an acrylic acid copolymerization ratio of 20% by weight) and a vinyl acetate copolymerization ratio of 28% by weight. Saponification degree 97.5%, M, 1.75g 710 minutes, density 0.9
51 g/cnf) was triblended for 5 minutes using a Henschel mixer. The obtained mixture [hereinafter referred to as "mixture (A)" 1] was heated using an extruder equipped with a T-die (diameter: 40 cm, die width: 30 cm, rotation speed: 85 revolutions/min) until the cylinder temperature reached C-. 100
℃, C2 = 120℃ and C5 - 140℃ and the die temperature was 180℃, and the film (thickness 100 microns) was molded and rolled onto a roll water-cooled to 20℃ (Examples 1 to 4, Comparative Examples 1 and 2), and instead of the ethylene-acrylic acid copolymer used in producing the mixture (A), 200 K/10
Mixture E and R Mixture (B) were prepared in the same manner as Mixture (A) except that an ethylene-methacrylic acid copolymer (density 0.950 g/crn', methacrylic acid copolymerization ratio 25iJ1%) was used. ” says J.
was manufactured. A film was produced from the obtained mixture in the same manner as described above (Example 4).
Comparative Example 1), referred to as J), and a saponified product of ethylene-vinyl acetate copolymer (hereinafter referred to as "saponified product", Comparative Example 2) were used to produce films in the same manner as described above.

Each film obtained in this way was heated at 320°C for 10 minutes using a heat press machine to produce 20kg/crn.
Crosslinking was carried out under a pressure of ' (gauge pressure) (thickness is shown in Table 1) to produce a sheet.

Each sheet thus obtained was masked except for the circuit using a screen printing machine.

Platinum was deposited on the obtained sheet using a vacuum deposition apparatus (manufactured by JEOL Ltd., trade name: JEE-4X model) in a 2XIG (2XIG) mold to obtain a platinum film having a thickness of about 100 OA.

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. .

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a portion of a representative example of a double-sided through-hole board in which areas other than circuit formation are masked by a negative method. Further, FIG. 2 is a partially enlarged sectional view of a typical example of a double-sided through-hole substrate in which an electroless copper plating film is formed on both sides and through-hole portions. Further, FIG. 3 is an enlarged sectional view of a part of a typical example of a substrate on which a so-called circuit is formed, with masked portions removed. 1... E-E thin wall material 2... Through-hole portion obtained from 1... Resist material

Claims (1)

[Scope of Claims] (A) 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. (B) A thin conductive film of 200 microns or less is formed on the surface of the thin object by metal vapor deposition on the thin object obtained by extruding it into a thin shape and heating and pressurizing the obtained thin object at a temperature of 100°C to 400°C. Or a printed wiring board on which a circuit is formed.