JP4620967B2 - Thermosetting resin composition for permanent hole filling - Google Patents

Description

  The present invention relates to a thermosetting resin composition useful for producing a multilayer printed wiring board and a multilayer printed wiring board using the same. More specifically, it is a liquid thermosetting resin composition that has little curing shrinkage and is excellent in crack resistance, and is useful as a composition for filling permanent holes such as via holes and through holes in printed wiring boards such as multilayer boards and double-sided boards. And a multilayer printed wiring board using the same.

In recent years, the pattern of printed wiring boards has been made thinner and the mounting area has been reduced, and further reductions in the size and functionality of printed wiring boards are expected in order to respond to the downsizing and enhancement of functionality of devices equipped with printed wiring boards. It is rare. For this reason, the printed wiring board is a build-up method in which a resin insulation layer is formed above and below the core material, a necessary circuit is formed, a resin insulation layer is further formed, and a conductor circuit is formed. The mounting components have been advanced to the area array type such as BGA (ball grid array) and LGA (land grid array). Recently, in order to further increase the density, there is a shift to a specification in which a pad is formed on a hole / recess and a component is mounted, or a via is formed on the hole / recess. Under such circumstances, in addition to filling properties, polishing properties, and cured product characteristics for filling holes / recesses, the composition for permanent hole filling has excellent adhesion of lid plating formed on the holes / recesses. Development of things is desired.
In the present specification, the “hole” is a general term for a via hole, a through hole, or the like formed in the manufacturing process of the printed wiring board.

  In general, as ink for permanent hole filling of printed wiring boards, thermosetting epoxy resin compositions are widely used because their cured products have excellent mechanical, electrical and chemical properties and good adhesion. ing. Moreover, in order to reduce the thermal expansion of hardened | cured material, many inorganic fillers are contained in this epoxy resin composition.

As such a composition, for example, a bisphenol type epoxy resin and a solventless resin filler containing an imidazole curing agent (see Patent Document 1) have been proposed. Such a composition is excellent in adhesiveness and eliminates shrinkage due to volatilization of an organic solvent, but due to catalytic curing with imidazole, distortion in the cured product is large, and insulation reliability and heat resistance are sufficient. There is a need for further improvements.
JP-A-10-75027 (Claims)

The present invention has been made in view of the circumstances as described above, and a basic object thereof is to provide a thermosetting resin composition having less curing shrinkage and excellent crack resistance.
Furthermore, the object of the present invention is that it can be liquefied with a useless agent or a small amount of an organic solvent, has no delamination due to volatile compounds remaining in the cured product, and has excellent properties such as insulation reliability and heat resistance. The object is to provide a thermosetting resin composition.
Furthermore, a conductive circuit is formed on the substrate through an interlayer resin insulating layer, and by using it as a filling of a printed wiring board having a hole filled with the filling, delamination due to thermal stress, etc. The present invention also provides a highly reliable printed wiring board having excellent characteristics such as insulation reliability and heat resistance.

In order to achieve the above object, basic aspects of the present invention include (A) an epoxy resin, (B) a polyfunctional phenol compound, (C) a curing catalyst, (D) a filler, and (E) an oxetane compound. And the blending amount of the oxetane compound (E) in the entire composition is 2-10% by mass, the number of equivalents of the epoxy group of the epoxy resin and the number of equivalents of the oxetane group of the oxetane compound (E). A thermosetting resin composition for permanent hole filling is provided, wherein the blending amount of the polyfunctional phenol compound with respect to the total number of equivalents is 0.7 to 1.2 . In a suitable aspect, it is preferable that the oxetane compound (E) used for the said thermosetting resin composition is a liquid at normal temperature.

  By using an oxetane compound, the thermosetting resin composition of the present invention has a reduced elastic modulus of the cured product and excellent crack resistance. Furthermore, as a preferred embodiment, by using a liquid oxetane compound, it is possible to reduce or eliminate organic solvents that contaminate the work environment. Furthermore, by reducing or eliminating the content of such volatile compounds, there is no delamination due to volatile compounds remaining after the production of the multilayer printed wiring board, and a highly reliable multilayer printed wiring board can be provided. It becomes possible.

The thermosetting resin composition of the present invention is characterized by a thermosetting epoxy resin composition comprising (A) an epoxy resin, (B) a polyfunctional phenol compound, (C) a curing catalyst, and (D) a filler. (E) The oxetane compound is blended , the blending amount of the oxetane compound (E) in the whole composition is 2-10% by mass, the number of equivalents of the epoxy group of the epoxy resin (A) and the oxetane compound (E) It exists in the point whose compounding quantity of the polyfunctional phenol compound (B) with respect to the total equivalent number of the equivalent number of an oxetane group is 0.7-1.2 .
That is, the thermosetting resin composition of the present invention includes the epoxy resin (A), the polyfunctional phenol compound (B), and (C) the curing catalyst by blending a predetermined amount of the oxetane compound (E). It was found that the curing shrinkage is reduced, the elastic modulus is lowered, and the curing strain is alleviated as compared with the composition comprising Furthermore, it has been found that by using a liquid oxetane compound as the oxetane compound (E), it can be liquefied with no solvent or a trace amount of an organic solvent without deteriorating electrical insulation properties.
Furthermore, such a thermosetting resin composition is used as a filling for a printed wiring board having a conductor circuit formed on a substrate through an interlayer resin insulating layer and having a hole filled with the filling. It has been found that a highly reliable printed wiring board having excellent properties such as insulation reliability and heat resistance can be obtained without using delamination due to thermal stress.

Hereinafter, each component of the thermosetting resin composition of the present invention will be described in detail.
First, as said epoxy resin (A), if it has two or more epoxy groups in 1 molecule, a well-known and usual thing can be used. For example, bisphenol A type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, diglycidyl ether of propylene glycol or polypropylene glycol, polytetra Methylene glycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, phenyl-1,3-diglycidyl ether, biphenyl-4,4′-diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene Diglycidyl ether of glycol or propylene glycol, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, Examples thereof include compounds having two or more epoxy groups in one molecule such as lith (2,3-epoxypropyl) isocyanurate and triglycidyl tris (2-hydroxyethyl) isocyanurate.
Among these, bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, diglycidyl ether of propylene glycol or polypropylene glycol Etc. are particularly preferred because they are easy to roughen. These can be used singly or in combination of two or more according to the demand for improving the properties of the coating.

Next, as the polyfunctional phenol compound (B), known and conventional compounds can be used as long as they have two or more phenolic hydroxyl groups in one molecule. Specific examples include phenol novolac resins, cresol novolac resins, bisphenol A, allylated bisphenol A, bisphenol F, bisphenol A novolac resins, vinylphenol copolymer resins, and the like. Is preferable because it has a high effect on increasing heat resistance.
Such a polyfunctional phenol compound (B) undergoes an addition reaction with the epoxy resin (A) in the presence of an appropriate curing catalyst (C), and further undergoes an addition reaction with an oxetane compound (E) described later. Therefore, the blending amount of the polyfunctional phenol compound (B) is 1 with respect to the total number of equivalents of the epoxy group of the epoxy resin (A) and the number of equivalents of the oxetane group of the oxetane compound (E) described later. : 0.7 to 1: 1.2, preferably 1: 0.8 to 1: 1.1. When the blending amount of the polyfunctional phenol compound (B) is less than 0.7 times the total number of equivalents, unreacted oxetane compound (E) and epoxy resin (A) remain, and in particular, oxetane compound. Is not preferred because it is difficult to cure by catalyst, and it is likely to remain, and sufficient cured product characteristics cannot be obtained. On the other hand, when the blending amount of the polyfunctional phenol compound exceeds 1.2 times, an excessive polyfunctional phenol compound (B) remains in the cured product, which is not preferable.

Examples of the curing catalyst (C) include compounds that serve as curing catalysts for the epoxy resin (A) and the polyfunctional phenol compound (B), and the oxetane compound (E) and the polyfunctional phenol compound (B) described below. , Tertiary amine, tertiary amine salt, quaternary onium salt, tertiary phosphine, crown ether complex, and phosphonium ylide, and the like can be arbitrarily selected from these, and these can be used alone or Two or more types can be used in combination.
Among these, imidazoles such as trade names 2E4MZ, C11Z, C17Z, and 2PZ, and AZINE compounds of imidazoles such as trade names 2MZ-A and 2E4MZ-A, trade names 2MZ-OK, and 2PZ-OK are preferable. Isocyanurate of imidazole such as imidazole, and imidazole hydroxymethyl compounds such as trade names 2PHZ and 2P4MHZ (the trade names are all manufactured by Shikoku Kasei Kogyo Co., Ltd.), dicyandiamide and its derivatives, melamine and its derivatives, diaminomaleonitrile and its Derivatives, amines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis (hexamethylene) triamine, triethanolamine, diaminodiphenylmethane, organic acid dihydrazide, 1,8-diazabicyclo [5,4,0] undecene 7 (trade name DBU, manufactured by San Apro Co., Ltd.), 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxaspiro [5,5] undecane (trade name ATU, Ajinomoto Co., Inc.) )), Or organic phosphine compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine.
Among these curing catalysts, dicyandiamide, melamine, acetoguanamine, benzoguanamine, 3,9-bis [2- (3,5-diamino-2,4,6-triazaphenyl) ethyl] -2,4,8 , 10-tetraoxaspiro [5,5] undecane and derivatives thereof, and their organic acid salts and epoxy adducts are known to have adhesion and rust prevention properties with copper. Since it not only works as a curing agent for the resin, but can also contribute to prevention of copper discoloration of the printed wiring board, it can be suitably used.
The amount of the curing catalyst (C) used is usually a normal quantitative ratio. For example, 0.1 to 10 parts by mass per 100 parts by mass of the epoxy resin (A) is appropriate.

The filler (D) used in the present invention is used for stress relaxation by curing shrinkage and adjustment of linear expansion coefficient, and is a known and commonly used non-conductive material used in ordinary resin compositions. Anything can be used. Examples thereof include silica, precipitated barium sulfate, talc, calcium carbonate, silicon nitride, and aluminum nitride. These can be used singly or in combination of two or more according to the demand for improving the properties of the coating. Among these inorganic fillers, silica is particularly excellent in low hygroscopicity and low volume expansion. Silica may be a mixture of these regardless of melting or crystallinity, but spherical fused silica is preferred from the viewpoint of high filling properties.
Moreover, the average particle diameter of these fillers (D) is preferably 3 to 25 μm. If the average particle size is less than 3 μm, the effect of suppressing the linear expansion coefficient of the cured product is low, while if it exceeds 25 μm, it is difficult to obtain defoaming properties and high filling properties, which is not preferable.
The blending ratio of such filler (D) is preferably 40 to 90% by mass, and more preferably 55 to 75% by mass of the total amount of the composition. When the blending ratio of the filler (D) is less than 40% by mass, the obtained cured product cannot exhibit a sufficiently low expansion property, and further, the polishing properties and adhesion are insufficient. On the other hand, when it exceeds 90% by mass, it becomes difficult to form a paste, and printability, hole filling and filling properties cannot be obtained.
In addition, when there is no problem even if it has conductivity, metal particles such as copper, gold, silver, and palladium can be used in combination.

The oxetane compound (E), which is a feature of the present invention, is represented by the following general formula (I):



(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)

A compound containing an oxetane ring. For example, a polyfunctional oxetane compound can be obtained by etherification or esterification using oxetane alcohols such as 3-ethyl-3-hydroxymethyloxetane as a raw material. Specific examples of the compound include 3-ethyl-3-hydroxymethyloxetane (trade name OXT-101 manufactured by Toagosei Co., Ltd.), 3-ethyl-3- (phenoxymethyl) oxetane (trade name OXT- manufactured by Toagosei Co., Ltd.). 211), 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (trade name OXT-212 manufactured by Toagosei Co., Ltd.), 1,4-bis {[(3-ethyl-3-oxetanyl) methoxy] methyl } Benzene (trade name OXT-121 manufactured by Toagosei Co., Ltd.), bis (3-ethyl-3-oxetanylmethyl) ether (trade name OXT-221 manufactured by Toagosei Co., Ltd.), and the like. Furthermore, phenol novolac type oxetane compounds and the like can also be mentioned. Among these, liquid oxetane compounds are preferable because they also have a diluting effect. Furthermore, bis (3-ethyl-3-oxetanylmethyl) ether (trade name OXT-221 manufactured by Toagosei Co., Ltd.), which is liquid and bifunctional, is preferable from the viewpoint of dilution effect and characteristics.
Such a liquid oxetane compound (E) does not use a halogen compound such as epichlorohydrin as a raw material, unlike a reactive diluent such as a polyglycidyl ether compound synthesized from epichlorohydrin and a polyfunctional alcohol. It has the characteristics that it has excellent skin irritation.
As a compounding quantity of the said oxetane compound (E), it is 10 mass% or less in the whole composition, Preferably, it is 2-8 mass%. When the blending amount of the oxetane compound (E) exceeds 10% by mass in the entire composition, the curability of the composition is lowered or the heat resistance of the cured product is lowered, which is not preferable.

In the thermosetting resin composition of the present invention, a diluent solvent may be added in addition to the liquid oxetane compound in order to adjust the viscosity of the composition. The blending ratio of the dilution solvent is preferably 10% by mass or less of the total amount of the composition, more preferably 5% by mass or less, and even more preferably no addition. When the blending ratio of the dilution solvent exceeds 10% by mass, bubbles and cracks are likely to be generated in the hole due to the evaporation of volatile components during the heating process.
Examples of the diluting solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene; methyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, propylene glycol monomethyl Glycol ethers such as ether, dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, and acetic acid ester of the above glycol ethers; ethanol, propanol, ethylene glycol, propylene glycol Alcohols such as octane, decane, etc .; petroleum ether, petroleum naphtha, hydrogenated naphtha, solvent naphtha, etc. Organic solvents, such as oil-based solvents. You may use these individually or in combination of 2 or more types.

In addition, when performing electroless plating on the cured product of the thermosetting resin composition of the present invention, in order to facilitate the roughening of the thermosetting resin composition and to improve the peel strength with the plating, an oxazine compound is used. May be blended.
The oxazine compound is a compound having an oxazine ring obtained by reacting a phenol compound, formalin and a primary amine. For example, Ba type benzoxazine manufactured by Shikoku Kasei Kogyo Co., Ltd., bisphenol F and formalin. And Fa-type benzoxazine manufactured by Shikoku Kasei Kogyo Co., Ltd. derived from aniline. These can be used alone or in combination of two or more.
By blending such an oxazine compound, the thermosetting resin composition of the present invention is filled into holes and recesses such as through holes and via holes of a printed wiring board and completely cured even after being completely cured. It can be easily roughened with a potassium acid aqueous solution or the like, and the adhesion of plating can be improved. Further, such an oxazine compound undergoes ring-opening polymerization by heat to produce a phenolic hydroxyl group, and reacts with the epoxy resin (A). In addition, it is known that weak acids and strong acids such as phenols having no substituent at the ortho-position or para-position are used as the ring-opening catalyst.
As a compounding quantity of the said oxazine compound, it is preferable to set it as 2.5 mass% or more and less than 50 mass% with respect to 100 mass% of organic components in a composition. When the compounding amount of the oxazine ring-containing compound is less than 2.5% by mass in the organic component, it is not preferable because an effect cannot be obtained with respect to adhesion to plating. On the other hand, when it is 50% by mass or more, voids and cracks are likely to occur in the hole during curing, which is not preferable.

  Furthermore, the composition of the present invention includes, as necessary, phthalocyanine blue, phthalocyanine green, iodin green, disazo yellow, crystal violet, titanium oxide, carbon black, which are used in normal screen printing resist inks. Known and commonly used colorants such as naphthalene black, known and commonly used thermal polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, pyrogallol and phenothiazine in order to impart storage stability during storage, clay, kaolin, organic Known and commonly used thickeners or thixotropic agents such as bentonite and montmorillonite, defoamers and / or leveling agents such as silicones, fluorines and polymers, imidazoles, thiazoles, triazoles, sila The known conventional additives, such as adhesion imparting agents such as a coupling agent may be blended.

  The viscosity of the thermosetting resin composition of the present invention comprising the above-described constituent components is preferably 1000 dPa · s or less at 25 ° C. in terms of filling properties. The blending amount of the oxetane compound (E) or the dilution solvent used for adjusting the viscosity is 10% by mass or less in the composition, thereby reducing the occurrence of cracks in the composition during curing after filling. Can do.

  The thermosetting resin composition of the present invention thus obtained can be filled into a via hole of a printed wiring board using a screen printing method, a roll coating method or the like conventionally used. Subsequently, it is heated at about 70 to 130 ° C. for about 30 to 90 minutes, then heated to about 140 to 180 ° C. and heated for about 30 to 90 minutes to be cured (finish hardening). Unnecessary portions protruding from the substrate surface of the composition thus cured can be easily removed by physical polishing, and a flat surface can be obtained. The composition of the present invention can be suitably used not only as a permanent hole filling ink for a printed wiring board but also for other uses such as an IC package sealant because of the excellent characteristics as described above. .

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the following description, “parts” are based on weight unless otherwise specified.

Examples 1 to 3 and Comparative Examples 1 and 2
The compounding components shown in Table 1 below were premixed and then kneaded with a three-roll mill to obtain each thermosetting resin composition.

  The viscosity at 25 ° C. of the thermosetting resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2 was measured by the following method, and the filling properties and polishing properties of the cured products filled in the holes of the wiring board were measured. The following methods were used to evaluate curing shrinkage, the presence or absence of cracks, and the presence or absence of residual voids.

Performance evaluation

viscosity:
0.2 ml of each of the thermosetting epoxy resin compositions of 1 to 3 and Comparative Examples 1 and 2 was collected, and using a cone plate viscometer (manufactured by Tokimec Co., Ltd.), conditions of 25 ° C. and 5 rpm / min. Measured with

Fillability:
The thermosetting resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2 were filled in the through holes under the following printing conditions by a screen printing method on a glass epoxy substrate in which through holes were formed in advance by panel plating. After filling, the sample was placed in a hot air circulation drying oven and pre-cured at 120 ° C. for 1 hour to obtain an evaluation sample (1). Fillability was evaluated by the degree of filling of the cured product filled in the through hole of this evaluation sample. The evaluation criteria are as follows.
○: Completely filled.
(Triangle | delta): The filled composition has flowed out from the bottom part of the through hole to the periphery.
X: The bottom of the through hole is not filled (underfilling).
(Printing conditions)
Squeegee: squeegee thickness 20 mm, hardness 70 °, oblique polishing: 23 °, plate: PET100 mesh bias plate, printing pressure: 60 kgf / cm ² , squeegee speed: 5 cm / sec, squeegee angle: 80 °

Abrasiveness:
The evaluation sample (I) was physically polished with a buffing machine, and after pre-curing, the ease of removing unnecessary portions of the cured product was evaluated. The evaluation criteria are as follows.
○: Easily polished △: Slightly difficult to polish ×: Not polished

Dent:
The evaluation sample (I) was physically polished with a buffing machine to remove unnecessary cured portions and smoothed. Then, it put into the hot-air circulation type drying furnace, main curing was performed at 150 degreeC for 1 hour, and evaluation sample (II) was obtained. The indentation of the through hole portion of this evaluation sample (II) was evaluated. The evaluation criteria are as follows.
○: No dent △: Slight dent is observed ×: Slight dent is observed

crack:
The evaluation sample (1) was cut at the through hole portion, the cross section was observed with an optical microscope, the through hole where a crack occurred in the sample was determined as NG, and the ratio of NG to the observed number of holes was calculated. . Judgment criteria are as follows.
○: Crack occurrence rate 0%
Δ: Crack generation rate less than 50% ×: Crack generation rate of 50% or more

Void residue:
The said evaluation sample (1) was cut | disconnected by the through hole part, the cross section was observed with the optical microscope, and the presence or absence of the void in a through hole was confirmed. The through hole in which the void remained was defined as NG, and the ratio of NG to the observed number of holes was calculated. The evaluation criteria are as follows.
○: Void residual rate 0%
Δ: Void residual ratio 50% or less ×: Void residual ratio exceeds 50%

The test results are shown in Table 2.

As is apparent from Table 2, Example 1 in which the oxetane compound was blended had a lower viscosity and excellent filling properties than Comparative Example 1 in which the organic solvent and the oxetane compound were not blended. Further, in Comparative Example 2 in which an organic solvent was blended as in the conventional composition instead of the oxetane compound, there was a dent in the through hole portion, and voids remained.

Claims (4)

(A) an epoxy resin, (B) a polyfunctional phenol compound, (C) a curing catalyst, (D) a filler, and (E) an oxetane compound ,
The amount of the oxetane compound (E) in the whole composition is 2-10% by mass,
The blending amount of the polyfunctional phenol compound with respect to the total equivalent number of the equivalent number of epoxy groups of the epoxy resin and the equivalent number of oxetane groups of the oxetane compound (E) is 0.7 to 1.2. A thermosetting resin composition for permanent hole filling . The said oxetane compound (E) is a liquid at normal temperature, The thermosetting resin composition for permanent hole filling of Claim 1 characterized by the above-mentioned. The cone plate type viscometer, 25 ° C., measured at a rotational speed of 5 rpm / min viscosity, permanent filling of claim 1 or claim 2, characterized in that less 1,000dPa · s Thermosetting resin composition. On a substrate, it is conductive circuits formed through an interlayer resin insulating layer, and the printed wiring board having a hole in which the packing has been filled, the filler filled in the hole portion, the claim A printed wiring board comprising a cured product of the thermosetting resin composition for permanent hole filling according to any one of 1 to 4.