JP2004238610A - Curable resin composition with low dielectric constant and printed-wiring board given by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition having a low dielectric constant and capable of easily forming wiring on its surface, by applying metal plating treatment to the surface, and to provide a wiring board given by using the same as an interlaminar insulating layer. <P>SOLUTION: This resin composition with the low dielectric constant contains an aromatic formaldehyde resin, a curing agent capable of curing the aromatic formaldehyde resin, an oxidizing agent, and a component which is roughened by at least one kind selected from an acid or an alkali. Therefore, the surface of the resin composition is chemically roughened, so that an anchor effect of the composition improves adhesion of a metal layer formed by electroless copper plating. Thus, the resin composition making it possible that the good metal layer causing no bulging nor peeling is formed on the surface is obtainable. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a low dielectric constant curable resin composition, particularly to a low dielectric constant curable resin composition that can be used as an interlayer insulating material of a printed wiring board, and a printed wiring board using the same.

  In general, a curable resin composition is used as an interlayer insulating film in a multilayer printed wiring board. Such an interlayer insulating film is required not only to have high reliability (especially, moisture absorption resistance and high adhesion), but also to have no surface on the surface when manufacturing by a known build-up method. It is required that wiring can be formed by electrolytic copper plating and electrolytic copper plating.

  In recent years, with the miniaturization of electronic devices and the speeding up of information communication, printed wiring boards have also been required to be miniaturized, have high-density mounting, and have excellent high-frequency characteristics. Therefore, a low dielectric constant and a low dielectric loss are required for the interlayer insulating film. However, the materials mainly used for the epoxy resin, which have been used so far, have a high polarity and a high dielectric constant and a large dielectric loss. Therefore, attempts have been made to use thermosetting polyphenylene ether, liquid crystal polymer, polyimide, fluorinated resin, or the like as a low dielectric material instead of an epoxy resin (Patent Documents 1 to 5).

JP-A-11-21503 JP-A-07-64914 JP 2001-53416 A JP-A-06-210795 JP-A-2002-50851

  Among the above low dielectric materials, thermosetting polyphenylene ether (Patent Documents 1 and 2) is difficult to perform electroless copper plating only by roughening with permanganic acid, which has been mainly used so far. Instead, the wiring is formed by bonding a metal foil having irregularities. However, with such a method, it has been impossible to form fine wiring. The liquid crystal polymer (Patent Document 3) cannot be plated unless a catalyst for electroless copper plating is mixed in the resin in advance, and it is difficult to form wiring. In order to perform a plating process on polyimide (Patent Document 4), it is necessary to form a polyimide film on a copper foil having a roughened surface, remove the copper foil, and transfer the surface roughness of the copper foil. It was difficult to form. In addition, fluorinated compounds generally have poor adhesion to metals and poor moldability and workability, and are incapable of electroless copper plating. As described above, the interlayer insulating film cannot have both a low dielectric constant and ease of wiring formation by electroless copper plating.

  The present invention has been made in view of the above problems, and has a resin composition having a low dielectric constant and easily forming a wiring by plating on the surface thereof, and a wiring using the same as an interlayer insulating layer. A substrate is provided.

Means for Solving the Problems / Effects of the Invention

In order to solve the above problems, in the low dielectric constant curable resin composition of the present invention,
An aromatic formaldehyde resin, a curing agent capable of curing the aromatic formaldehyde resin, and a component roughened by at least one selected from an oxidizing agent, an acid, and an alkali (hereinafter, also referred to as a roughened component) And containing.

  Aromatic formaldehyde resin has a low polarity because it contains an aromatic ring and an ether bond, and a resin composition cured by adding a curing agent capable of curing the aromatic formaldehyde resin to heat resistance and moisture absorption resistance. It becomes an excellent low dielectric constant curable resin composition. However, when a plating layer is formed on the surface by electroless copper plating, the adhesion of the plating layer to the resin composition is insufficient, and swelling or peeling occurs, which causes an interlayer insulating film as a printed wiring board. Practical application was difficult. Therefore, in order to solve such a problem, in addition to the above components, a component roughened by at least one selected from oxidizing agents, acids and alkalis (hereinafter, also referred to as a roughening agent) is added to the resin composition. It has been found that it is contained. Thereby, the surface of the resin composition can be chemically roughened, and the adhesion of the plating layer by electroless copper plating can be improved by the anchor effect. In this way, a resin composition capable of forming a good plating layer without swelling or peeling on its surface can be obtained.

  Further, in the aromatic formaldehyde resin, the aromatic formaldehyde resin in which at least one or more of the hydrogen atoms belonging to the aromatic ring contained in the molecule is substituted with a hydrocarbon group, the hydrocarbon group is an electron. Since it has a donating property, it has a characteristic that the curing reaction is accelerated, and thus is suitable for use as a component of a low dielectric constant curable resin composition having excellent curability. Further, the cured product has excellent adhesiveness and flexibility, and these features are advantageous for use as an interlayer insulating film of a printed wiring board. Specifically, such an aromatic formaldehyde resin is preferably a xylene formaldehyde resin and / or a mesitylene formaldehyde resin (commonly referred to as “xylene resin”).

  The xylene formaldehyde resin and / or mesitylene formaldehyde resin is, for example, an oligomer synthesized from meta-xylene and / or mesitylene and formaldehyde, and has a reactive group such as a methylol group, a dimethylene ether group, or an acetal group in a molecule. . In particular, the xylene formaldehyde resin shows high reactivity due to the acid catalyst, and the obtained cured product has a low dielectric constant since it has few polar groups. Other aromatic formaldehyde resins include toluene, ethylbenzene, pseudocumene, monocyclic aromatic hydrocarbon compounds having 10 or more carbon atoms, or polycyclic aromatic hydrocarbon compounds such as naphthalene and methylnaphthalene, or derivatives thereof. Alternatively, a reaction product (oligomer) obtained by reacting the mixture with formaldehyde can be exemplified.

  In addition, the low dielectric constant curable resin composition of the present invention may contain a polyphenol compound in addition to the above components. When the aromatic formaldehyde resin is cured, cracks or the like may occur in the cured product due to large curing shrinkage. Therefore, when the resin composition contains a polyphenol compound, it is possible to prevent or suppress the occurrence of cracks in the cured product, and further, while ensuring a low dielectric constant as compared with the case where the polyphenol compound is not contained, A cured product having more excellent curability and good heat resistance can be obtained. Here, the polyphenol compound refers to a compound containing two or more phenolic hydroxyl groups in one molecule, and examples thereof include bisphenols, novolaks, resols, hydroxyvinylphenols, and other phenol adducts. be able to. In the polyphenol compound, since the ortho position and the para position of the phenolic hydroxyl group react with the aromatic formaldehyde resin to cause crosslinking, it is desirable that the ortho position and the para position of the phenolic hydroxyl group are not substituted.

As the means for curing the aromatic formaldehyde, two types of heat curing and light curing can be considered, and corresponding curing agents are used.
A curing agent that can thermally cure an aromatic formaldehyde resin is one that generates an acid by heating, cures an aromatic formaldehyde resin such as a xylene resin, and promotes a crosslinking reaction between a polyphenol compound and the xylene resin. I just need. For example, use of ionic compounds such as hexafluoroantimony salts, trichloromethyltriazine compounds, diazonium salts, iodonium salts, and sulfonium salts, carboxylic acids, nonionic compounds such as sulfonic acid esters and amide derivatives, and phosphorus compounds. Can be.

  The curing agent capable of photocuring the aromatic formaldehyde resin can be, for example, a photoactive species generator that generates an active species by irradiating light, and the active form cures the aromatic formaldehyde resin. It can be. The aromatic formaldehyde resin may be, for example, one in which a part of the hydrogen of the aromatic ring is substituted by an oxygen-containing substituent such as a methylol group, a dimethylene ether group, or an acetal group. The composition containing the aromatic formaldehyde resin exhibits excellent photosensitivity. It is presumed that these oxygen-containing substituents react with a compound having active hydrogen under an acid catalyst to generate reactive species such as carbocations, and the reactive species causes an intermolecular condensation reaction to proceed. Is done. Therefore, the photo-curing agent can be a photo-cationic polymerization initiator for initiating cationic polymerization, and further a photo-acid generator for generating an acid upon irradiation with light. As such a photocuring agent, it is possible to use known ones such as ionic compounds such as diazonium salts, iodonium salts and sulfonium salts, and nonionic compounds such as carboxylic acid and sulfonic acid esters and amide derivatives. it can.

  Next, the present invention is characterized in that the low dielectric curable resin composition has a relative dielectric constant after curing of 3.3 or less or a dielectric loss tangent after curing of 0.04 or less. This is a range in which when used as an interlayer insulating film of a printed wiring board, the signal propagation speed is high and the signal attenuation can be sufficiently suppressed. If the values of both the relative permittivity and the dielectric loss tangent are smaller, the above-mentioned effects can be obtained more, and the lower limit is not particularly limited (except 0). Further, it is desirable that the relative dielectric constant after curing is 3.3 or less and the dielectric loss tangent after curing is 0.04 or less.

  Next, the present invention is characterized in that the component roughened by at least one selected from the group consisting of an oxidizing agent, an acid and an alkali is a component roughened by an oxidizing agent. In general, an acid or alkali has a weaker roughening force than an oxidizing agent, and therefore requires a long roughening treatment to form a good roughened surface. For this reason, it is conceivable that the resin surface not intended for roughening may be damaged. Since the oxidizing agent has a strong roughening power, a good roughened surface can be obtained by a relatively short roughening treatment compared with the case where an acid or an alkali is used, and the resin surface as described above may be damaged. Can be avoided. More preferably, the oxidizing agent is a permanganate. There are various types of permanganate, such as potassium, sodium, and calcium permanganate, which have a strong oxidizing power (this is a power for roughening), and a fatty acid (chain-type structural portion) described later. It is an oxidizing agent that is particularly effective for causing decomposition and reactions that break double bonds.

  Next, in the present invention, it is effective to use an aliphatic compound as a component roughened by at least one selected from the oxidizing agent, acid and alkali. This is a particularly effective component when the roughening agent is an oxidizing agent. Aliphatic compounds are effective in forming a roughened surface because they have a characteristic that an aliphatic component (chain-type structure portion) is easily decomposed by an oxidizing agent. Of these, those having a double bond in the molecule are more effective because the double bond has a property of being very easily reacted with an oxidizing agent. Polybutadiene, which is an aliphatic compound, contains many such double bonds in the molecule. Further, the hydroxyl-terminated polybutadiene in which the terminal of polybutadiene is substituted with a hydroxyl group which is easily oxidized is more easily roughened, and a roughened surface can be easily formed.

  The above-mentioned components are particularly effective when the roughening agent is an oxidizing agent, but are also roughened against an acid or an alkali. Further, even if an acid or an alkali is not actively used as a roughening agent, it is used for a surface treatment or the like in a manufacturing process of a printed wiring board, and therefore, it is considered that the acid or alkali may act as a roughening agent at that time. On the other hand, when an acid or an alkali is positively used as a roughening agent, a component to be roughened corresponding to them is selected. The following can be considered as components to be roughened. When an acid is used as a roughening agent, a compound having an amino group showing an alkalinity (amine) is used. When an alkali is used as a roughening agent, a compound having a carboxyl group showing an acidity (carboxylic acid) or phenol is used. And a compound having a thiol group.

  The component roughened by at least one selected from the oxidizing agent, acid and alkali has a viscosity of 3000 Pa.s at 25 ° C. It is desirable that the material be a liquid or viscous material of s or less. In order to form fine wiring (for example, about 100 μm or less in width) on the roughened surface of the low dielectric constant curable resin composition, the unevenness of the roughened surface must also be fine. The component must be a liquid or viscous substance in the above-described state. If the component to be roughened is a liquid or viscous material, the component to be roughened is easily compatible with the aromatic formaldehyde resin and can be finely dispersed as compared with a case where the component is a solid. Therefore, when the cured product is subjected to a roughening treatment, the roughened surface has finer irregularities. Furthermore, the component to be roughened is 1500 Pa. More preferably, it is not more than s.

In addition, it is effective to use an acetal compound as a component roughened by at least one selected from an oxidizing agent, an acid, and an alkali. Here, the “acetal compound” is a general term for a compound having a structure in which an aldehyde hydrate (ortho aldehyde) and an alkyl group are ether-bonded (alias: dialkoxy compound RCH (OR ′) ₂ ). When such an acetal compound is used as a component to be roughened, the same effects as described above can be obtained, and a resin composition having a lower coefficient of thermal expansion than usual can be obtained. Such a resin composition having a low expansion coefficient is advantageous for use as an interlayer insulating film of a printed wiring board. Specifically, a butyral resin or the like can be used as the acetal compound. The butyral resin is a resin in which the main chain is composed of polyvinyl alcohol and the side chain is composed of butyraldehyde.

  Further, it is desirable that the component roughened by at least one selected from the oxidizing agent, acid and alkali is compatible with the aromatic formaldehyde resin to form a transparent varnish. In order to form fine wiring (eg, about 100 μm or less in width) on the roughened surface of the low dielectric constant curable resin composition, the unevenness of the roughened surface must be fine, and the aromatic formaldehyde resin It is important to select a component that is compatible with the material and becomes transparent. The fact that the varnish becomes transparent means that the formaldehyde resin and the component to be roughened are mixed at a molecular level, and when a roughening treatment is performed on the cured product, the roughened surface has a molecular level of about. It will have order irregularities. On the other hand, when the varnish becomes cloudy without being compatible, the components to be roughened are present as a lump (aggregate) in the resin. The roughness of the surface becomes too large, and it is difficult to accurately form fine wiring. Here, the term “transparent” means a degree to which a person visually perceives the transparency, and specifically, the evaluation is made based on the transmittance of an ultraviolet / visible absorption spectrum. Specifically, the resin composition is placed in a cell having an optical path length of 1 cm, and the absorption spectrum in the range of 200 to 900 nm is measured. Those having a transmittance of 70% or more in a region excluding the absorption peak unique to the resin composition are transparent. Is determined.

  The low dielectric constant curable resin composition of the present invention can be applied to, for example, an insulating layer of a printed wiring board requiring a low dielectric constant. Specifically, the present invention can be applied to a multilayer printed wiring board manufactured by a known build-up method. In this case, the low dielectric constant curable resin composition of the present invention is applied to an interlayer insulating film. The surface of such an interlayer insulating film can be easily roughened, thereby facilitating the formation of wiring by electroless copper plating. Since the printed wiring board thus obtained has an interlayer insulating film having a low dielectric constant and a low dielectric loss tangent, the signal delay of the transmission signal and the loss of the transmission signal are reduced, and the high-frequency characteristics are excellent. It becomes.

  Further, the insulating film of the low dielectric constant curable resin composition of the present invention has a low dielectric constant, a low dielectric loss tangent, and is excellent in heat resistance, moldability, flexibility, insulation, and water absorption resistance, Manufacturing is relatively easy. Due to such advantages, the low dielectric constant curable resin composition of the present invention can be used not only for an interlayer insulating film but also for a solder resist layer in a printed wiring board. However, since no wiring is formed on the solder resist layer, it has nothing to do with the above-described advantage in forming the wiring.

  Further, if necessary, the low dielectric constant curable resin composition may contain a filler such as a silica filler, a flexibility imparting agent such as a thermoplastic resin, a trace additive such as an antifoaming agent or a sensitizer, and a varnish. It can be used for an insulating layer (especially, an interlayer insulating film) of a printed wiring board by adding a volatile solvent or the like in the case of forming.

  Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. FIG. 1 shows an example of a printed wiring board 1 as one embodiment of the present invention, and FIG. 2 shows a cross-sectional structure thereof. The printed wiring board 1 is, for example, about 25 mm square and about 1 mm thick, and has the following structure. That is, a core is formed in a predetermined pattern on both surfaces of a plate-shaped core material 2 made of a heat-resistant resin plate (for example, a bismaleimide-triazine resin plate) or a fiber-reinforced resin plate (for example, a glass fiber-reinforced epoxy resin). The wiring pattern layers 3 and 13 are respectively formed. These core wiring pattern layers 3 and 13 are formed so as to cover most of the surface of the core material 2 and are used as power supply layers or ground layers. On the other hand, a through-hole 12 formed by a drill or the like is formed in the core material 2, and a through-hole conductor 30 that connects the core wiring pattern layers 3 and 13 to each other is formed on the inner wall surface. The through hole 12 is filled with a resin filling material 31 such as an epoxy resin.

  Further, first resin build-up layers 4 and 14 are respectively formed of a curable resin on the core wiring pattern layers 3 and 13. Further, first wiring pattern layers 5 and 15 are formed on the surface thereof by copper plating (described later). The core wiring pattern layers 3 and 13 and the first wiring pattern layers 5 and 15 are interconnected by via conductors 32 and 33, respectively. Similarly, second resin buildup layers 6 and 16 are formed of a hardening resin on the first wiring pattern layers 5 and 15, respectively. Second wiring pattern layers 7 and 17 are formed on the surface by copper plating (described later), respectively. The first wiring pattern layers 5 and 15 and the second wiring pattern layers 7 and 17 are connected to each other by via conductors 34 and 35, respectively.

  Here, the insulating resin build-up layers 4, 14, 6, and 16 are made of a low dielectric constant insulating plastic material made of a low dielectric constant curable resin composition of the present invention, in which a resin material that is a main component of the layers is formed. I have. Such insulating resin build-up layers 4, 14, 6, and 16 have a low dielectric constant and a low dielectric loss tangent, and are excellent in heat resistance, moldability, flexibility, insulation, and water absorption. Specifically, the low dielectric constant curable resin composition of the present invention contains, by mass%, 15 to 80% of an aromatic formaldehyde resin and 0.1% of a curing agent capable of curing the aromatic formaldehyde resin. 5 to 50% of a component roughened by at least one selected from an oxidizing agent, an acid and an alkali. Further, a polyphenol compound may be contained in an amount of 20 to 70%.

  The surfaces of the first resin build-up layers 4 and 14 and the second resin build-up layers 6 and 16 are formed, for example, in a manufacturing process before forming a wiring pattern by electroless copper plating on the surfaces. The surface is roughened with an oxidizing agent such as a manganate (sodium, potassium, calcium, etc.). Further, a copper plating wiring pattern layer 5, 15, 7, 17 is formed by further performing a plating process such as electrolytic copper plating on the wiring pattern formed by electroless copper plating.

  The surfaces of the core wiring patterns 3 and 13, the first wiring pattern layers 5 and 15, and the second wiring pattern layers 7 and 17 are subjected to a surface roughening treatment (for example, blackening) in order to increase the adhesion strength to the upper resin layer. (Based on a chemical treatment such as a chemical treatment or a chelate etching treatment).

  Next, a metal mark layer 9 is formed on the second resin build-up layer 6. The metal mark layer 9 is formed, for example, as a gold plating layer (for example, 0.04 μm in thickness) on the outermost surface, and for example, as shown in FIG. It includes a mark 9a, a fiducial mark 9b used for positioning the substrate, and the like. All of these have a smooth surface and a relatively strong metallic luster appearance. Further, on the second resin build-up layer 6, a large number of underlying conductive pads 10 electrically connected to the second wiring pattern layer 7 are provided. These underlying conductive pads 10 are arranged in a square shape at substantially the center of the substrate by electroless Ni-P plating and Au plating, and form a chip mounting portion 40 together with the solder bumps 11 formed thereon. .

  On the other hand, on the side where the second wiring pattern layer 7 is formed and on the side where the second wiring pattern layer 17 is formed, resin solder resist layers 8 and 18 that cover the wiring pattern layers 7 and 17 are formed respectively. Have been. On the wiring pattern layer 7 side, the metal mark layer 9 is exposed from the resin solder resist layer 8. Such a structure can be obtained, for example, by forming a resin solder resist layer in such a manner as to once cover the entire metal mark layer, and then removing the portion of the resin solder resist layer that covers the metal mark layer.

  The following tests were performed on the low dielectric constant curable resin composition of the present invention. First, a xylene resin, a phenol resin, a thermosetting agent, and a component to be roughened were mixed at a weight ratio shown in FIG. 3 to prepare resin compositions of Examples 1 to 4 and Comparative Example 1.

Nixanol L and H (unmodified products) manufactured by Mitsubishi Gas Chemical Co., Ltd. were used as the xylene resin. The viscosities of L and H are different (12.6 Pa.s for L, 200 Pa.s for H). In Comparative Example 1, an epoxy resin, specifically, a bisphenol A type epoxy resin (Epicoat 828 manufactured by Japan Epoxy Resin) was used instead of the xylene resin.
The phenol resin has a composition in which liquid polybutadiene and phenol are synthesized, a decahydronaphthalene structure is generated in the molecule, and the OH equivalent is 420 g / eq. , A resin having a molecular weight of 2000 (PP-1000-240 manufactured by Nippon Petrochemical) or a novolak-type special phenol, and having an OH equivalent of 104 g / eq. And a resin having a molecular weight of 500 (TD-2131 manufactured by Dainippon Ink and Chemicals, Inc.).
As the thermosetting material, an aromatic sulfonium salt (SI-100L manufactured by Sanshin Chemical Industry) was used.
Hydroxyl-terminated polybutadiene rubber (Idemitsu Petrochemical R-15HT) was used as the component to be roughened.

  Next, the obtained resin composition is applied on a substrate so as to have a thickness of about 40 μm, dried at 70 ° C. for 30 minutes, and then heated at 130 ° C. for 2 hours to cure the resin composition and to prepare a sample plate. Was prepared. Thereafter, an evaluation test as described below was performed.

`` Thermosetting test ''
The degree of curing of the resin composition was determined by the following method. On the sample plate, the surface of the cured resin composition was rubbed with a cloth impregnated with acetone to check whether or not the resin composition was dissolved or damaged. The case where no damage was found was judged as “good”, the case where there was some damage was judged as “almost good”, and the case where dissolution was found was judged as “poor”.

"Measurement of electrical characteristics (relative permittivity and dielectric loss tangent)"
The dielectric constant and the dielectric loss at 1 MHz of the cured resin composition (film having a thickness of about 40 μm) were measured according to JIS K6911 (Japan Electronic Industry Standard). The measuring instrument used was an impedance analyzer (HP4194A manufactured by Hewlett-Packard).

"Roughening and plating of resin"
As shown in the steps of FIGS. 5 and 6, the surface of the cured resin composition was subjected to a roughening treatment, and thereafter, a plating layer was formed by electroless copper plating. The chemicals in the figure are each commercially available. Then, a plating layer formed by electroless copper plating (hereinafter referred to as an electroless plating layer) was visually inspected for swelling or peeling (evaluation of plating state).
Further, a plating layer having a thickness of about 25 μm (hereinafter referred to as a wiring plating layer) was formed on the electroless plating layer by electrolytic copper plating using a copper sulfate solution. Then, a cut having a width of 1 cm was made in the wiring plating layer, and a force required to peel the wiring plating layer in a direction of 90 degrees was measured (peel strength measurement).

"Coefficient of thermal expansion (CTE)"
A test piece having a length of 20 mm and a width of 5 mm was cut out from the cured sheet, and the coefficient of thermal expansion was measured by Rigaku TMA-8310. The coefficient of thermal expansion is calculated by the following equation.
CTE (ppm / ° C.) = ((Elongation (%) at 50 ° C.) − (Elongation (%) at 20 ° C.)) / (50 ° C.-20 ° C.) × 10000
The measurement conditions are as follows.
Span: 15 mm, load: tensile load of 5 g in the length direction of the test piece Temperature condition: After raising the temperature to 180 ° C., annealing for 30 minutes, cooling to −55 ° C., and 270 at a rate of 10 ° C./min Heat to ℃ and measure elongation

  FIG. 4 shows the evaluation results of the curability and the electrical characteristics. When a xylene resin, a phenol resin and a hydroxyl-terminated polybutadiene are combined (Examples 1 to 3), both curability and electrical properties (relative permittivity 2.8 to 3.1, dielectric loss tangent 0.01 to 0.02) are used. This was within the range usable as a low dielectric constant interlayer insulating film material (good electrical characteristics are those having a relative dielectric constant of 3.3 or less and a dielectric loss tangent of 0.04 or less). When no phenol resin was added (Example 4), the curability was slightly inferior to that of Examples 1 to 3 in which phenol resin was added, and high-temperature heating was required. Although Example 4 does not pose a problem in practical use, it can be seen that adding a phenolic resin is more preferable for use as a material for an interlayer insulating film because the curability is improved.

  On the other hand, in Comparative Example 1, the curability was good, but the electrical characteristics (dielectric constant 3.6, dielectric loss tangent 0.04) were not good. This is presumably because when an epoxy resin is used, a hydroxyl group is generated from an epoxy group upon curing, so that the relative dielectric constant and the dielectric loss tangent increase. According to the above evaluation results, the use of aromatic formaldehyde (xylene resin) that does not generate a hydroxyl group upon curing as an interlayer insulating film material of a printed wiring board is effective in improving the electrical characteristics of the printed wiring board. Understand.

  Next, a xylene resin, a phenol resin, a thermosetting agent, and a component to be roughened were mixed at the weight ratio shown in FIG. 7 to prepare resin compositions of Examples 5 to 11 and Comparative Examples 2 to 5. The viscosity in the figure is a value measured at 25 ° C. using a B-type rotational viscometer at a shear rate of 0.8 (l / s). In addition, the components to be roughened were mixed in a xylene resin and a phenol resin, and the varnish was evaluated for transparency. Thereafter, a sample plate was prepared in the same manner as described above, and the curability, electrical characteristics, and plating state were evaluated. FIG. 8 shows the evaluation results.

  In Examples 5 to 11 in which a liquid rubber (the molecular structure of each of which is shown in FIG. 9 such as hydroxyl-terminated polybutadiene) is added as a component to be roughened, the electric characteristics are good and the electroless plating layer swells or peels off. This is not seen, indicating that a good electroless plating layer was formed. On the other hand, in Comparative Example 2 in which the component to be roughened was not added, swelling and peeling were observed in the electroless plating layer. Therefore, it is understood that a favorable electroless plating layer can be obtained by performing the roughening treatment by adding the component to be roughened. In addition, Comparative Examples 3 to 5 satisfy only the requirements of Claims 1 to 7 of the present specification (although they should be considered as Examples, here, for comparison described below, For the sake of convenience, they are classified into comparative examples), and since a component to be roughened is added to these, the electroless plating layer is excellent.

  Comparative Example 3 includes silicone resin particles (average particle size: 5 μm) as a component to be roughened, and Comparative Example 4 includes silica particles (average particle size: 5 μm) as a component to be roughened. These are not aliphatic compounds but components that are not roughened by permanganate. It was a solid (fine particle) component at room temperature, and the varnish was slightly cloudy. In Comparative Example 5, acrylic ester and methacrylic acid ester copolymer fine particles (average particle size: 0.5 μm) were added as components to be roughened. This was a solid (lumpy aggregate) component at normal temperature, turbidity was observed in the varnish, and the solid was floating. In addition, when the above-described transmittance measurement was performed on the varnish, the transmittance of each of Examples 5 to 11 in which good transparency was obtained visually was 70% or more, whereas the transmittance of the varnish was slightly cloudy. In Comparative Examples 3 and 4 where turbidity was observed, transmittance was in the range of 30 to 50%, and in Comparative Example 5 where turbidity was observed and solids were floating, transmittance was 1% or less and almost 0%. It showed a value close to.

  In Comparative Examples 3 to 5 described above, the electroless plating layer formed on the surface was good without any swelling or peeling, but the peel strength was 0.4 to 0.6 kN / m, which was the same as Example 5. As compared with the results (0.8 to 1.2 kN / m), only about half the strength was obtained.

  In Examples 5 to 11, the component to be roughened is composed of an aliphatic compound which is easily decomposed into permanganate. Further, since it is liquid at room temperature, it is easy to make it compatible with the xylene resin and the phenol resin, and the components can be finely dispersed. Therefore, it is considered that a roughened surface having fine irregularities can be obtained by the roughening treatment, and the adhesion of the electroless plating layer is improved by a strong anchor effect.

Further, the components to be roughened in Examples 5 to 11 have high compatibility with the xylene resin and the phenol resin because they have polar groups such as a hydroxyl group, a carboxyl group, and an epoxy group in the molecule. It is also possible. Among these polar groups, Examples 5 and 6, which contain a component having a hydroxyl group having higher compatibility with the phenolic resin, have higher peel strengths than those of other examples. It is considered that a roughened surface having the same was obtained.
In Examples 5, 9 and 11, in which a large number of double bonds which easily react with the oxidizing agent were contained in the molecule, the peel strength was higher than those of Examples. This is considered to be due to the decomposition of the double bond by the oxidizing agent (permanganate), whereby a roughened surface having finer irregularities was obtained.
Furthermore, Example 5 having the above two requirements, that is, containing a large number of double bonds and containing a hydroxyl-terminated polybutadiene having a hydroxyl group at its terminal as a component to be roughened, Among them, the peel strength is the largest at 1.2 kN / m, and it is considered that a roughened surface having the finest unevenness is formed.

  On the other hand, in Comparative Examples 3 and 4, since the component to be roughened was not an aliphatic compound and was not roughened to permanganate, it was present near the surface among the particles dispersed in the resin. It is considered that the surface was roughened by the particles falling off. Therefore, it is presumed that the roughness of the roughened surface became huge as compared with the cases of Examples 5 to 11, and the electroless plating layer could not sufficiently obtain the anchor effect, resulting in poor adhesion.

  In Comparative Example 5, a solid component (lumpy agglomerate, primary particle average particle size: 0.5 μm) at room temperature was used as a component to be roughened, and the varnish was turbid. This is because when the components to be roughened are mixed into the xylene resin and the phenol resin at the stage of preparing the resin composition, the components to be roughened are not dispersed until they become fine primary particles, and the state of the aggregates It is considered that the compound was present in the resin composition as it was. Then, since the roughened surface was formed by roughening or falling off of the aggregate, the unevenness of the roughened surface became huge as compared with the case of Examples 5 to 11, and the electroless plating layer provided a sufficient anchor effect. It is presumed that the adhesiveness was not obtained.

  From the above results, the components to be roughened are (1) a liquid component that is easily compatible with the resin, and (2) an aliphatic compound that is easily decomposed by an oxidizing agent (permanganate). It is further desirable that a component having (3) a double bond easily reacting with an oxidizing agent (permanganate) and (4) a hydroxyl group having higher compatibility with a xylene resin and a phenol resin in the molecule. Was found to be more desirable.

  Next, a xylene resin, a phenol resin, a thermosetting agent, and a component to be roughened were mixed at the weight ratio shown in FIG. 10 to prepare resin compositions of Examples 12 to 15 and Comparative Examples 6 to 9. In Examples 13 to 15, butyral resin was used as a component to be roughened. In FIG. 10, butyral resin 1 indicates KS-1 manufactured by Sekisui Chemical Co., Ltd., butyral resin 2 indicates KS-3Z manufactured by Sekisui Chemical Co., Ltd., and butyral resin 3 indicates KS-5Z manufactured by Sekisui Chemical Co., Ltd. In addition, as the xylene resins of Examples 12 to 15 and Comparative Example 6, Nikanol G (viscosity 1 Pa.s (75 ° C.)) manufactured by Mitsubishi Gas Chemical Company was used.

  Then, similarly to the above, the components to be roughened are mixed in xylene resin and phenol resin, and the varnish is evaluated for transparency. Further, a sample plate is prepared, and the curability, peel strength, and coefficient of thermal expansion ( CTE) and the plating state were evaluated. FIG. 10 shows the evaluation results of the transparency, and FIG. 11 shows the other evaluation results.

  According to FIG. 10, the varnishes of Examples 13, 14, 15 and Comparative Example 9 using butyral resin had good transparency. Butyral resin is synthesized by the reaction of polyvinyl alcohol and butyraldehyde, and has a highly compatible hydroxyl group in the molecule. FIG. 9H shows the structural formula of butyral resin. Therefore, the varnish has good compatibility with the xylene resin and the epoxy resin and is solid at normal temperature, but the varnish has good transparency by being dissolved.

  According to FIG. 11, in Examples 12 to 15, copper plating having better peel strength and better appearance was obtained as compared with the comparative example. This is presumably because a butadiene-based rubber or a butyral resin having good compatibility was used as a component to be roughened, so that plating was successfully performed and high peel strength was obtained. In Examples 12 to 15, similarly to the above-described examples, a low-polarity xylene resin (aromatic formaldehyde resin) is used, so that a low dielectric constant and a low dielectric loss tangent are achieved. Furthermore, Examples 13 to 15 using butyral resin have lower thermal expansion as compared with Comparative Examples. It is considered that this is because the addition of the butyral resin having a high molecular weight and compatibility with each other make it possible to harden the entire resin. Such a low thermal expansion resin composition is advantageous because it can reduce thermal stress when used for a printed circuit board or the like.

  In Comparative Examples 6 to 9, Comparative Example 6 did not use an epoxy resin and thus had a low dielectric constant and a low dielectric loss tangent, but did not have any components to be roughened, so that plating could not be formed. . Comparative Example 7 did not have a component to be roughened, so that plating could not be formed, and the use of an epoxy resin did not result in a low dielectric constant and a low dielectric loss tangent. Comparative Example 8 had a component to be roughened, so that plating could be formed. However, since the epoxy resin was used, the dielectric constant and the dielectric loss tangent were not low. In Comparative Example 9, plating was possible and low thermal expansion because butyral resin was used as a component to be roughened, but it was not low dielectric constant and low dielectric loss tangent because epoxy resin was used. .

FIG. 2 is a plan view showing one embodiment of the printed wiring board of the present invention. Diagram schematically showing the cross-sectional structure Component Table for Resin Compositions of Examples 1 to 4 and Comparative Example 1 Evaluation results for resin compositions of Examples 1 to 4 and Comparative Example 1 Roughening process Electroless copper plating process Component Table for Resin Compositions of Examples 5 to 11 and Comparative Examples 2 to 5 Evaluation results for resin compositions of Examples 5 to 11 and Comparative Examples 2 to 5 (A) Molecular structure of hydroxyl-terminated polybutadiene [Example 5] (b) Molecular structure of hydroxyl-terminated epoxidized polybutadiene [Example 6] (c) Molecular structure of epoxy-1,4-butadiene rubber [Example 7] ( d) Molecular structure of epoxy-1,2-butadiene rubber [Example 8] (e) Molecular structure of carboxyl terminal-1,2-vinylbutadiene rubber [Example 9] (f) Hydrogenated carboxyl terminal-1,2 -Molecular structure of vinyl butadiene rubber [Example 10] (g) Molecular structure of carboxyl-terminated isoprene rubber [Example 11] (h) Molecular structure of butyral resin [Examples 13 to 15] Component Table for Resin Compositions of Examples 12 to 15 and Comparative Examples 6 to 9 Evaluation results for resin compositions of Examples 12 to 15 and Comparative Examples 6 to 9

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Printed wiring board 4, 14 First insulating resin buildup layer 5, 15 First wiring pattern layer 6, 16 Second insulating resin buildup layer 7, 17 Second wiring pattern layer 8, 18 Resin solder resist layer

Claims (17)

  An aromatic formaldehyde resin, a curing agent capable of curing the aromatic formaldehyde resin, and a component roughened by at least one selected from an oxidizing agent, an acid, and an alkali. Dielectric curable resin composition.   The low dielectric constant curable resin composition according to claim 1, wherein at least one or more hydrogen atoms belonging to an aromatic ring contained in the aromatic formaldehyde resin are substituted with a hydrocarbon group. .   The low dielectric constant curable resin composition according to claim 2, wherein the aromatic formaldehyde resin is at least one of a xylene formaldehyde resin and a mesitylene formaldehyde resin.   The low dielectric constant curable resin composition according to any one of claims 1 to 3, further comprising a polyphenol compound.   The low dielectric constant curable resin composition according to any one of claims 1 to 4, wherein the cured resin has a relative dielectric constant of 3.3 or less.   The low dielectric constant curable resin composition according to any one of claims 1 to 5, wherein a dielectric loss tangent after curing is 0.04 or less.   The component roughened by at least one selected from the group consisting of an oxidizing agent, an acid and an alkali is a component roughened by an oxidizing agent, according to any one of claims 1 to 6, wherein Low dielectric constant curable resin composition.   8. The low dielectric constant curable resin composition according to claim 7, wherein the oxidizing agent is a permanganate.   The low dielectric constant curable composition according to any one of claims 1 to 8, wherein the component roughened by at least one selected from the group consisting of an oxidizing agent, an acid and an alkali is an aliphatic compound. Resin composition.   The low dielectric constant curable resin composition according to claim 9, wherein the aliphatic compound has a double bond in a molecule.   The low dielectric constant curable resin composition according to claim 10, wherein the aliphatic compound is polybutadiene.   The low dielectric constant curable resin composition according to claim 10, wherein the aliphatic compound is hydroxyl-terminated polybutadiene.   The component roughened by at least one selected from the group consisting of an oxidizing agent, an acid and an alkali has a viscosity of 3000 Pa.s at 25 ° C. 13. The low dielectric constant curable resin composition according to any one of claims 1 to 12, wherein the composition is not more than s.   The low dielectric constant curable resin according to any one of claims 1 to 8, wherein the component roughened by at least one selected from the group consisting of an oxidizing agent, an acid and an alkali is an acetal compound. Composition.   The low dielectric constant curable resin composition according to claim 14, wherein the acetal compound is a butyral resin.   The component roughened by at least one selected from the group consisting of an oxidizing agent, an acid, and an alkali is compatible with the aromatic formaldehyde resin to form a transparent varnish. Item 4. The low dielectric constant curable resin composition according to item 1.   A printed wiring board comprising a wiring formed by copper plating on a surface of an insulating layer made of the low dielectric constant curable resin composition according to any one of claims 1 to 16.

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