JP4784082B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a method for manufacturing a printed wiring board having a smooth insulating layer and a method for filling an insulating layer between circuit patterns.

  In recent years, in the printed wiring board market, as the example of integration in the weak electric field such as a personal computer and a cellular phone, multilayering of circuits has progressed. In order to manufacture a multilayer printed wiring board by a build-up method, which is one of typical multilayering techniques, it is often necessary for the lower layer substrate to be smooth. For example, when the circuit pattern of the printed wiring board is produced by the subtractive method, the circuit pattern portion (Fig.1a) formed on the insulating layer (Fig.1c) rises from the substrate surface (Fig.1b), and the substrate It is difficult to further form a circuit on the surface (FIG. 1b), and it is necessary to smooth the substrate surface (insulating layer) because the presence of irregularities on the surface is disadvantageous particularly for fine pattern formation.

  Also, in the high electric field where a large current flows such as automobile parts, the height of the circuit pattern portion (FIG. 1a) becomes high. There were many cases of unevenness. However, this unevenness has not been a problem because it has been conventionally used as a single-sided plate or a double-sided plate. However, in recent years, there has been an increasing demand for multilayer boards having three or more circuits in the high power field, and in order to build up, it has become necessary to smooth the insulating layer in the same manner as in the weak power field. However, in order to flow a large current, the height of the circuit pattern portion (FIG. 1a) needs to be as thick as 200 μm or more, and it is not ready to compensate for this height and smooth the insulating layer. For example, in the conventional method of simply laying up the prepreg, (1) the circuit cannot be fully filled, and the required heat resistance and electrical reliability required as a printed wiring board cannot be secured due to the formation of voids. (2) The glass cloth comes into contact with the circuit, resulting in problems such as failure to maintain electrical reliability as a printed wiring board. Therefore, a method for filling a resin between circuits has been required.

JP 2000-332387 A JP 2002-064273 A

  Therefore, in order to flatten the unevenness, (a) a method of applying and drying a liquid resin so as to fill the circuit, or (Patent Document 1) (b) inserting a resin film between the circuit and the prepreg, the circuit Have been devised (Patent Document 1, Patent Document 2). However, when applying a liquid resin, (1) the process of application, drying, etc. will increase and become complicated (2) bubbles will easily enter during application, which may be a defect when it becomes a printed wiring board ( 3) When a solvent is used, if the thickness of the circuit is high, such as in high voltage applications, and the space between embedded circuits is deep, the solvent may remain in the resin embedded between the circuits, and the characteristics of the printed wiring board There were problems such as possible damage. Further, both of the methods a and b have a problem that since the resin peripheral layer occupies the periphery of the circuit, the strength is low, and cracks are easily generated due to thermal expansion, impact, or the like.

Therefore, as a result of various studies, the inventors have invented a method that is simple, has a low possibility of residual solvent and bubbles, and has an insulating portion in which the peripheral portion of the circuit is reinforced more than the resin layer and smoothes the insulating layer. It came to do.
The present invention relates to the following inventions.
<1> A printed wiring board having a smooth insulating layer formed by filling irregularities of a circuit pattern of a printed wiring board with an insulating material made of a fiber and a resin composition.
<2> A printed wiring board formed by subjecting the insulating material comprising the fiber and the resin composition according to <1> to a process of laminating a sheet-like material comprising the fiber and a semi-cured resin composition on a circuit. .
<3> A printed wiring board in which the fibers according to <1> or <2> are glass fibers or aramid fibers.
<4> The thickness of the insulating layer formed on the conductor of the circuit by the insulating material comprising the fiber and resin composition according to <1> to <3> does not exceed the thickness of the conductor of the circuit, and the thickness of the circuit is A printed wiring board having a size of 50 μm or more.
<5> A method for producing a printed wiring board according to <1> to <4>.

  According to the present invention, it is possible to obtain a printed wiring board on which a smooth insulating layer is formed by filling the unevenness of the circuit pattern of the printed wiring board with an insulating material made of a fiber and a resin composition, and the obtained printed circuit board. The wiring board can obtain superior characteristics as compared with a printed wiring board manufactured by a conventional method. In addition, handling is simple, the possibility of residual solvent and bubbles is low, and the insulating portion formed in the periphery of the circuit can be reinforced more than a simple resin layer.

  The present invention relates to a printed wiring board and a printed wiring board, in which it is essential to form an insulating layer made of a fiber and a resin composition on the periphery of the circuit pattern as a technique for flattening the unevenness of the circuit pattern of the printed wiring board. It relates to a manufacturing method.

In the present invention, the material, shape, etc. of the fiber are not particularly limited as long as it does not significantly impair the properties as a printed wiring board while ensuring insulation, and any inorganic fiber or organic fiber may be used. Aramid fiber is preferable as the organic fiber.
The resin composition is not particularly limited, but is preferably a thermosetting resin, and more preferably a resin composition having a combination of an epoxy resin and a curing agent thereof.
By combining these, a sheet-like material (hereinafter referred to as a resin-impregnated nonwoven fabric) made of a fiber and a semi-cured resin composition is produced. The produced resin-impregnated non-woven fabric is laid up on the circuit (FIG. 2a) formed on the substrate (FIG. 2d) in the same manner as the prepreg, and is flattened by heating and pressure forming at once. However, after planarization as illustrated in FIG. 1, the material (FIG. 2 c) constituting the resin-impregnated nonwoven fabric may be embedded between the circuits as illustrated in FIGS. 2 may be formed so as to cover some or all of the circuits as illustrated in 1-2 of FIG. 2, and further illustrated in FIG. 2b as illustrated in FIGS. A material such as a prepreg or a resin film may be laid up on the resin-impregnated nonwoven fabric.

The present invention relates to a printed wiring board having a smooth insulating layer by using a sheet-like material made of a fiber and a resin composition to form irregularities in a circuit pattern of the printed wiring board, and a manufacturing method thereof.
The present invention relates to a printed wiring board and a manufacturing method thereof, characterized by forming a smooth insulating layer by filling irregularities of a circuit pattern with an insulating material made of a fiber and a resin composition. However, it is not limited to use copper foil with resin together.

  The material and shape of the fiber used are not particularly limited as long as they do not impair the properties of the printed wiring board such as electrical insulation, and may be any of inorganic fiber and organic fiber. Preferably, glass, aramid, polyester, polyethylene, polypropylene, cellulose, acrylic, polyurethane, cupra, nylon, vinylon, polyacrylonitrile, acetate ceramic, rock wool, rayon, viscose, polymix, polyvinyl chloride, polyvinylidene chloride, These are fibers such as polyacrylonitrile, polyclar, silk, cotton, wool, hemp. More preferred are glass and aramid fiber.

  The shape of these fibers is not particularly limited as long as the properties of the printed wiring board are not impaired. For example, the diameter of the fiber is not particularly limited, but a fiber of 1 to 30 μm is preferable, more preferably 3 to 20 μm, and particularly preferably 4 to 13 μm. Although it does not prescribe | regulate also about fiber length, Preferably it is 1-50 mm, More preferably, it is 3-30 mm, Most preferably, it is 6-15 mm.

Further, the method of filling the unevenness of the circuit pattern with an insulating material composed of a fiber and a resin composition is characterized by using a sheet-like material (resin-impregnated nonwoven fabric) formed using the fiber and the resin composition. The method for producing this resin-impregnated nonwoven fabric is not particularly limited. For example, the above fibers can be produced by paper making a nonwoven fabric, impregnating and drying the resin. Alternatively, the fiber can be dispersed on a holding surface such as a wire mesh, impregnated with resin, and dried. The timing of peeling from the holding surface may be before the step of impregnating and drying the resin, before the drying after the impregnation, or after the drying, and is not particularly limited. In addition to these, fibers can be dispersed in the varnish at the same time as the resin, and paper can be produced.
The resin content of the resin-impregnated nonwoven fabric is not particularly limited as long as a good insulating layer is formed, but preferably 35 to 99%, more preferably 45 to 97%, more preferably 60 to 97%, More preferably, it is 75 to 97%.

  The resin composition described in the present invention is not particularly limited as long as the required characteristics as a printed wiring board are not significantly impaired. A resin composition mainly containing a thermosetting resin or a thermoplastic resin is preferred, and a resin composition mainly containing a thermosetting resin is particularly preferred. Here, the thermosetting resin is not particularly limited, but epoxy resin, urea resin, melamine resin, and phenol resin are preferable, and these can be used alone or in combination. Of these, the case of using an epoxy resin is most preferable. The epoxy resin here is bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalenediol type epoxy resin, phenol novolac type epoxy resin, cresol novolak type epoxy resin, bisphenol. A novolak-type epoxy resins, cycloaliphatic epoxy resins, glycidyl ester resins, glycidylamine resins, heterocyclic epoxy resins (triglycidyl isocyanurate, diglycidyl hydantoin, etc.), and modified epoxies modified with various reactive monomers Resins and the like can be used, and these bromides can also be used. Two or more of these epoxy resins can be used in appropriate combination. In particular, it is desirable to use phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin or their halides because of high heat resistance and reliability that can be applied to electrical and electronic materials. The amount added is not particularly specified, but is preferably in the range of 1 to 50% by weight in the total resin composition in order to obtain a sufficient cured product.

  In addition, a curing agent can be added for the purpose of improving workability and accelerating the curing of the added epoxy. Curing agents include phenolic, amine-based, cyanate-based, acid anhydride-based, and compounds having a dihydrobenzoxazine ring. As long as the addition amount is in a range that does not significantly inhibit the curing reaction of the resin composition, an arbitrary amount can be added, and it is particularly preferable to use in the range of 0 to 50% by weight of the resin composition. Specifically, phenolic novolak, cresol novolak, bisphenol A, bisphenol F, bisphenol S, curing agents having a phenolic hydroxyl group such as melamine-modified novolak type phenol resin, or halogenated curing agents such as dicyandiamide Examples of the curing agent include a known cyanate curing agent, an acid anhydride, and a compound having a dihydrobenzoxazine ring. The compound having a dihydrobenzoxazine ring here is easily synthesized by heating and reacting phenols, amines and aldehydes in an appropriate solvent such as methyl ethyl ketone (MEK), and removing the solvent and water. it can. For example, 1 mole of phenol and 1 mole of aniline and 2 moles of formaldehyde are added to 1 mole of phenol to be refluxed and cooled at any reaction rate. Thereafter, the resin can be obtained by removing the solvent, moisture, and possibly unreacted substances. Phenols can be phenol, cresol, bisphenol A, bisphenol F, bisphenol S, etc., amines can be aniline, diaminobenzene, etc., and aldehydes can be formaldehyde, paraform, etc. it can. Of course, these curing agents do not need to be used alone, and may be used in combination. Further, the epoxy resin and the curing agent used in the present invention can be used after appropriately reacting in advance.

  In addition to this, the resin composition of the present invention can also contain a filler. Metal oxides such as silica, talc, mica, calcium silicate, potassium silicate, calcined clay, titanium oxide, barium sulfate, aluminum oxide, magnesium carbonate, calcium carbonate, barium carbonate, molybdenum oxide, zinc oxide, magnesium silicate, etc. Metal hydroxides such as aluminum hydroxide and magnesium hydroxide are good, and other compounds such as oxides composed of a plurality of elements such as molybdenum, zinc, calcium, phosphorus, aluminum, and potassium may be used. . Moreover, the compound which consists of a some combination of the oxide which consists of molybdenum, silicon, magnesium, and zinc may be sufficient.

  In addition to these, an inorganic filler can be added to the resin composition of the present invention for the purpose of increasing rigidity and reducing thermal expansion. In addition, pigments, adhesion assistants, antioxidants, curing accelerators can be added. There are no particular limitations as long as a known substance can be used and does not deteriorate the printed wiring board characteristics.

  Regarding the type and amount of organic solvent used in the production of resin-impregnated nonwoven fabric, etc., the viscosity and volatility appropriate for producing a prepreg by uniformly dissolving or dispersing the epoxy resin and the curing agent constituting the resin composition. However, from the viewpoints of cost, handleability, and safety, methyl ethyl ketone, 2-methoxyethanol, 2-methoxypropanol, 1-methoxy-2 are satisfied. It is preferable to use about 5 to 60% by weight of the total weight of the resin composition containing a solvent such as propanol and dimethylformamide (DMF).

  The method of forming an insulating layer made of a fiber and a resin composition using these resin-impregnated nonwoven fabrics is not particularly limited as long as a good printed wiring board can be obtained. A method of obtaining a flattened insulating layer by pressing with metal foil or a release film and an end plate and then heat-pressing is simple and easy, and is preferable. In this press molding, the number of the resin-impregnated nonwoven fabrics laid up may be one or more, and is not particularly limited. Further, simultaneously with the layup of the resin-impregnated nonwoven fabric, prepreg, resin sheet, copper foil with resin, etc. may be laid up. For the purpose of improving workability after pressing, a release film such as polytetrafluoroethylene and polyethylene terephthalate may be used at the same time. The distribution of the insulating layer made of the fiber and the resin composition to be formed is not particularly limited, and as shown in FIG. 2, the entire circuit or part of the circuit is covered even if it is completely embedded between the circuits. The circuit may be embedded with. The circuit embedding need not be performed only with the resin-impregnated non-woven fabric component, and is not limited to being supplemented with all or a part of the constituent materials of the prepreg, resin film, and resin-coated copper foil used in parallel. The atmosphere during molding is not particularly limited as long as the characteristics of the printed wiring board are ensured, but it is preferably 400 hPa or less, preferably 200 hPa or less, more preferably 100 hPa or less, and even more preferably 40 hPa or less. In the case of press molding, the product pressure is not particularly limited as long as it is a value that allows good molding without defects, but it is preferably 2.0 MPa or more, more preferably 4.0 MPa or more, excluding the pressure for temporary pressure bonding. Well, if necessary, it may be 6.0 MPa or more.

  In addition, part or all of the resin-impregnated nonwoven fabric and part or all of the fibers in the resin may be cut or broken at the time of molding, but there is no particular limitation unless the characteristics of the printed wiring board are significantly impaired.

  Here, it is desirable that the thickness of the insulating layer made of the fiber and the resin composition formed on the circuit pattern does not exceed the thickness of the circuit, and it is particularly desirable that the thickness of the circuit is 50 μm or more. More preferably, when the circuit thickness is 170 μm or more, the thickness of the insulating layer made of the fiber and the resin composition formed on the circuit at that time is preferably 150 μm or less. More preferably, the circuit thickness is 250 μm or more and the insulating layer thickness is 120 μm or less.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples.

In the examples and comparative examples, the following were used as epoxy resins, curing agents, prepregs and the like. As the nonwoven fabric, a glass nonwoven fabric and an aramid nonwoven fabric having a basis weight of 25 g were used. For other organic solvents, additives, general-purpose fillers, non-woven fabrics, copper foils, releasable films, etc., raw materials generally used in the chemical industry and the electronics industry were used except those specifically described.
Epoxy resin: Cresol novolac type epoxy resin manufactured by Dainippon Ink and Chemicals, Inc.
Product name N-673 (epoxy equivalent 210)
Phenol-based curing agent A: Melamine novolak resin trade name Phenolite LA-7054 manufactured by Dainippon Ink and Chemicals, Inc.
Prepreg: Prepreg copper-clad laminate
Product name GEA-67BE HHFQ (insulating layer thickness equivalent to 200 μm)
Substrate with circuit: A prepreg 2ply is sandwiched and pressed from both sides with 300μm thick copper foil to obtain a laminated board, and then a circuit (test pattern) with a residual rate of 50% on the surface of the double-sided copper-clad laminated board by a subtractive method Formed.

Example 1
The epoxy resin and the curing agent were weighed so that the equivalent ratio of epoxy group and hydroxyl group was 1: 0.8, and dissolved in MEK so as to have a solid concentration of 75%. Furthermore, a varnish was prepared by adding a curing agent and an additive for adjusting viscosity. This varnish was applied to a glass nonwoven fabric and dried at 160 to 175 ° C. for 4 minutes to obtain a resin-impregnated nonwoven fabric (corresponding to 200 microns) having a resin content of 90%.
The evaluation is made by laying up the prepared resin-impregnated nonwoven fabric 1Ply and the prepreg 1Ply on the test pattern subjected to BF treatment (blackening treatment) on both sides of the test pattern, and further applying a resin-coated copper foil 185 on the outside thereof. A multilayer board was produced by heating and pressing at 80 ° C. and 80 ° C. for 80 minutes.
Using this multilayer board, the flatness, moldability, heat resistance, impact test, and electrical insulation were evaluated. The evaluation results are shown in Table 1.
Whether or not flattening was possible and formability were evaluated by visual inspection after removing the copper foil on both sides of the multilayer board by etching.
For heat resistance, the multilayer board produced above was cut into a 50 mm square and dried, and then immersed in 260 ° C. solder for 10 seconds to confirm over blistering and the like.
The impact test was a falling ball test. In the falling ball test, 100 g of a spherical weight was dropped on the printed wiring board produced, and the height at which the cracked weight was dropped was determined to be acceptable when the height was 50 cm or more.
The electrical insulation was evaluated by cutting the multilayer board prepared above into 50 mm squares, insulating the ends, and then applying a voltage of 100 V between the inner layer circuits at a temperature of 85 ° C. and a humidity of 85%. The amount of change in resistance (Ω) after 500 hours was measured. The case where the resistance value after 500 hours was 100 MΩ or more was regarded as acceptable.

Example 2
In the same manner as in Example 1, varnish was applied to an aramid nonwoven fabric and dried to obtain a resin-impregnated nonwoven fabric, and a multilayer board was prepared and evaluated in the same manner. The evaluation results are shown in Table 1.

Comparative Example 1
On both sides of the test pattern, prepreg 2Ply was laid up on the test pattern, and printed boards were prepared and evaluated in the same manner as in Examples 1 and 2. The evaluation results are shown in Table 1.

Comparative Example 2
A release film placed on a glass substrate is laid so that the release surface faces upward, and the same resin as in Example 1 is applied thereon, and air drying is repeated a plurality of times. When the resin thickness reaches 200 μm, 160 to 175 is reached. The resin sheet with a carrier film was obtained by drying at 4 ° C. for 4 minutes and removing the release film together with the glass substrate. One resin sheet was laid up on the test pattern, the carrier film was peeled off, and the prepreg was further laid up. A printed board was prepared and evaluated in the same manner as in Examples 1 and 2. The evaluation results are shown in Table 1.

  From Table 1, in Examples 1-2 illustrated, all the test results were favorable or passed (circle of Table 1 description). The handling property of the resin-impregnated paper was as easy as that of the prepreg, and the circuit was sufficiently filled with the fiber and the resin composition, and a good flattened insulating layer could be obtained. Also, no defects such as voids were found in the formability. Furthermore, the characteristic as a printed wiring board implemented subsequently was also good.

However, in Comparative Example 1, defects and failures (x in Table 1) occurred frequently. First, planarization was insufficient and the circuit was not sufficiently filled with resin. In the heat resistance test, measling occurred. The impact test could not be performed because the circuit was not fully filled. In the electrical insulation test, sufficient insulation was not obtained because a part of the glass cloth was in contact with the circuit. Thus, when a prepreg was used, a good printed wiring board could not be obtained.
In Comparative Example 2, it was possible to flatten the circuit, but it was difficult to handle because the resin sheet was brittle and easily broken. In addition, the insulating layer embedded between the circuits was cracked in the impact test due to the fragility due to the fact that it was made of only resin, resulting in the loss of the characteristics as a printed wiring board.

It is sectional drawing of a metal-clad laminated board. It is an example of sectional drawing of the metal-clad laminated board with which the insulating layer was smooth | blunted.

Explanation of symbols

a: Circuit pattern portion b: Base material surface c: Insulating layer d: Substrate

Claims (5)

A resin-impregnated non-woven fabric, which is a sheet-like material formed by using fibers and a resin composition, with the unevenness of the circuit pattern of the printed wiring board , wherein the resin content of the resin-impregnated non-woven fabric is 75 to 97% A printed wiring board in which a smooth insulating layer is formed by filling with a cloth .   A resin-impregnated nonwoven fabric, which is a sheet-like material formed using the fiber and resin composition according to claim 1, is composed of a fiber and a semi-cured resin composition, and undergoes a step of laminating the resin-impregnated nonwoven fabric on a circuit. A printed wiring board formed by   The printed wiring board whose fiber of Claim 1 or 2 is glass fiber or an aramid fiber.   The thickness of the insulating layer formed on the conductor of the circuit by the resin-impregnated nonwoven fabric, which is a sheet-like material formed using the fiber and resin composition according to any one of claims 1 to 3, is the thickness of the conductor of the circuit. And a printed wiring board having a circuit thickness of 50 μm or more.   A resin-impregnated nonwoven fabric, which is a sheet-like material molded using fibers and a resin composition, is laid up on a circuit and heated and pressed to fill the irregularities of the circuit pattern on the printed wiring board for smooth insulation. The manufacturing method of the printed wiring board in any one of Claims 1-4 which forms a layer.

Images