HK1261475B - Metal-clad laminate, printed wiring board and semiconductor package - Google Patents

Description

Metal-clad laminate, printed wiring board, and semiconductor package

Technical Field

The present invention relates to a metal-clad laminate, a printed wiring board, and a semiconductor package.

Background Art

From the perspective of simplification, efficiency and labor saving, the items around us used in daily life are being electronicized. From the perspective of convenience in use, the electronic components used in electronic equipment are required to be further lightweight and miniaturized. Therefore, the printed wiring boards used in electronic components are also thinner and miniaturized, and the wiring patterns are being refined and the thickness of the insulating layer is being thinned. From the perspective of price and operability, the components carried are also getting smaller and narrower in pitch, so the warping of the printed wiring board during installation may become a big problem. Therefore, in the past, in order to reduce the difference between the thermal expansion of the substrate before and after reflow soldering and the thermal expansion of the installed chip, the glass transition temperature of the resin layer contained in the substrate is increased, or the thermal expansion coefficient of the resin layer is low, thereby reducing warping.

In recent years, the trend toward thinner substrates and narrower pitches has led to a growing desire to further reduce warpage. Consequently, methods have been proposed, such as replacing glass cloth with quartz cloth to lower the thermal expansion coefficient and increasing substrate rigidity to suppress the stress that causes warpage (see Patent Document 1).

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-278414

Summary of the Invention

Problems to be solved by the invention

However, the quartz cloth described in Patent Document 1 is hard and therefore has poor machinability in drilling and substrate cutting, thus requiring development of a method that does not require quartz cloth (although the present invention does not exclude solutions that include quartz cloth).

Furthermore, the recent increase in wireless communication devices utilizing high-frequency bands and the resulting increase in communication speeds are inevitably leading to an increasing use of high-frequency bands. Transmission loss has become a significant factor in high-frequency substrates. To reduce the relative dielectric constant, a large amount of resin composition is applied to aggregates such as fiber base materials. However, since the void volume of aggregates is fixed, excess resin composition is retained as a resin layer on the aggregate surface, potentially causing warping.

Therefore, an object of the present invention is to provide a metal-clad laminate, a printed wiring board, and a semiconductor package in which warping is effectively suppressed.

Means for solving problems

The present inventors have repeatedly conducted in-depth research to solve the above-mentioned problems. As a result, they speculated that when the proportion of the resin layer in the overall prepreg is high, the curing shrinkage of the resin composition present on the surface and back surfaces of the fiber substrate has a greater impact on the warping of the substrate. They also found that even if the proportion of the resin layer in the overall prepreg is high, the above-mentioned problems can be solved by adjusting the thickness of the resin composition on the surface and back surfaces, without using a hard fiber substrate such as quartz cloth, and thus completed the present invention.

That is, the present invention provides the following [1] to [9].

[1] A metal-clad laminate using a prepreg comprising a resin composition attached to a fiber base material, the prepreg satisfying the following formula (1), and further satisfying the following formula (2).

0.12＜{(a1+a2)/2}/B (1)

0.8≤a1/a2≤1.25 (2)

(In the above formula, a1 is the average thickness of the resin composition present on one surface of the fiber substrate after curing, a2 is the average thickness of the resin composition present on the other surface of the fiber substrate after curing. B is the average thickness of the fiber substrate.)

[2] The metal-clad laminate according to [1] above, wherein the fiber base material is glass cloth.

[3] The metal-clad laminate according to [1] or [2] above, wherein in the above formula (1), the average thickness B of the fiber base material is 5 to 120 μm.

[4] The metal-clad laminate according to any one of [1] to [3] above, wherein the fiber base material is a single-layer fiber base material.

[5] The metal-clad laminate according to any one of [1] to [4] above, wherein the resin composition contains a thermosetting resin.

[6] The metal-clad laminate according to any one of [1] to [5] above, wherein the resin composition contains at least one thermosetting resin selected from epoxy resin, phenolic resin, unsaturated imide resin, cyanate resin, isocyanate resin, benzoxazine resin, oxetane resin, amino resin, unsaturated polyester resin, allyl resin, dicyclopentadiene resin, silicone resin, triazine resin and melamine resin.

[7] The metal-clad laminate according to any one of [1] to [6] above, wherein the warpage amount measured by the following measurement method is 2.0 mm or less.

Warpage measurement method: The copper foil of the outer layer of a metal-clad laminate is completely etched, leaving only the laminate. The laminate is then placed horizontally and dehydrated at 80°C for 2 hours, then allowed to return to room temperature at 20°C. A 250 mm square test piece is cut from the center of the resulting laminate. This test piece is fixed and suspended at 20°C at any one of its four corners, and the warpage at the other three points is measured. This procedure is repeated for all four corners, and the largest value is taken as the warpage.

[8] A printed wiring board formed using the metal-clad laminate according to any one of [1] to [7] above.

[9] A semiconductor package comprising the printed wiring board described in [8] above.

Effects of the Invention

According to the present invention, a metal-clad laminate, a printed wiring board, and a semiconductor package in which warping is effectively suppressed can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view for explaining a prepreg used in the present invention.

DETAILED DESCRIPTION

[Metal-clad laminate]

The metal-clad laminate of the present invention uses a prepreg in which a resin composition is attached to a fiber base material, the prepreg satisfies the following formula (1), and further satisfies the following formula (2).

0.12＜{(a1+a2)/2}/B (1)

0.8≤a1/a2≤1.25 (2)

In the above formulas (1) and (2), a1 is the average thickness of the resin composition on one surface of the fiber substrate after curing, and a2 is the average thickness of the resin composition on the other surface of the fiber substrate after curing. B is the average thickness of the fiber substrate (see Figure 1).

The method for obtaining the values of a1, a2, and B is not necessarily limited, but the present invention adopts values measured by the following method.

(Measurement method of a1, a2 and B)

The prepreg was suspended in a dryer, and the temperature of the dryer was increased from 20°C to 160°C at a rate of 5°C/hour. After being held at 160°C for 30 minutes, the sample was placed in a container so that it conformed to a 0.01 mm thickness tape (Japanese: シクネステ一プ) measured in accordance with JIS B 7524 (2008) [sheet shape: Type A].

Then, 100 parts by mass of bisphenol A type liquid epoxy resin and 10 parts by mass of trimethyltetramine were stirred and injected into the above-mentioned container. After vacuum degassing for 3 minutes at a vacuum degree of 700 mmHg (93.3 kPa), the mixture was cured at 40°C for 60 minutes and then at 60°C for 90 minutes. After curing, the cured product was taken out from the container, cut and mechanically polished to expose the cross section. The cross section was observed with a scanning electron microscope (SEM) to measure the thickness of the resin composition on one side of the fiber substrate, the thickness of the resin composition on the other side of the fiber substrate, and the thickness of the fiber substrate.

Regarding the measurement, 10 parts without obvious scratches, dents, and creases were measured, and their average values were calculated to obtain a1 (measured value), a2 (measured value), and B (measured value), respectively. The a1 (corrected value), a2 (corrected value), and B (corrected value) obtained by performing the following correction are used as a1, a2, and B in the above formulas (1) and (2), respectively.

-Calibration method-

The 0.01 mm thick strip was also observed using a scanning electron microscope (SEM). The thickness was measured at 10 locations in the same manner as above, and the average value was calculated. Using this average value and 0.01 mm, the correction coefficient α was calculated using the following formula (3). The calculated correction coefficient α was multiplied by a1 (measured value), a2 (measured value), and B (measured value), respectively, to obtain a1 (corrected value), a2 (corrected value), and B (corrected value).

α＝0.01mm/Thickness Average value of the measured thickness of the strip (3)

a1(corrected value)=a1(measured value)×α

a2(corrected value)=a2(measured value)×α

B (corrected value) = B (measured value) × α

The above-mentioned correction is performed for the purpose of correcting the deviation between the measured value and the true value when the prepreg is not cut or mechanically polished at a right angle to the measurement surface.

The aforementioned thickness tape is available from Tokyo Thickness Co., Ltd.

The bisphenol A type liquid epoxy resin can be represented by the following formula (I).

[Chemistry 1]

In formula (I), ⁿ¹ is an integer of 0 to 3, preferably an integer of 0 to 2, and more preferably 0 or 1.

The epoxy equivalent of the bisphenol A-type liquid epoxy resin is preferably 150 to 500 g/eq, more preferably 150 to 400 g/eq, and even more preferably 150 to 250 g/eq. Here, the epoxy equivalent is the mass of the resin per epoxy group equivalent (g/eq) and can be measured according to the method specified in JIS K 7236 (2009), and the same applies hereinafter. Specifically, using a Mitsubishi Chemical Analytech automatic titrator "GT-200 Model", 2 g of the epoxy resin is weighed into a 200 ml beaker, 90 ml of methyl ethyl ketone is added dropwise, and the mixture is dissolved in an ultrasonic cleaner. Then, 10 ml of glacial acetic acid and 1.5 g of cetyltrimethylammonium bromide are added, and the mixture is titrated with a 0.1 mol/L perchloric acid/acetic acid solution to determine the epoxy equivalent.

As the bisphenol A type liquid epoxy resin, a commercially available product can be used, and examples of the commercially available product include "jER (registered trademark) 815" (manufactured by Mitsubishi Chemical Corporation).

The average thickness B of the fiber substrate is preferably 5 to 120 μm, more preferably 5 to 100 μm, further preferably 10 to 100 μm, particularly preferably 10 to 50 μm, and most preferably 10 to 30 μm.

The above formula (1) is an indicator of the ratio of the average value of the average thickness of the resin composition present on the surface and back of the fiber substrate after curing [(average thickness a1 on the surface + average thickness a2 on the back)/2] to the average thickness (B) of the fiber substrate. Here, the surface and back are not particularly limited, and any surface can be defined as the surface, and the same applies hereinafter.

When the ratio of the average post-curing thickness of the resin composition present on the surface and back of the fiber substrate to the total prepreg is greater than a specified value, the curing shrinkage of the resin composition present on the surface and back of the fiber substrate significantly affects the warpage of the substrate. Therefore, in order to set the conditions that cause this problem, the value of {(a1+a2)/2}/B in formula (1) is greater than 0.12. When this value is met, it is necessary to effectively reduce warpage.

The prepreg used in the present invention is not particularly limited, but preferably satisfies the following formula (1').

0.12＜{(a1+a2)/2}/B≤0.45 (1’)

(In the above formula, a1, a2 and B are as defined above.)

The prepreg used in the present invention is not particularly limited, but preferably satisfies the following formula (2').

0.9≤a1/a2≤1.15 (2’)

The above formulas (2) and (2') define the ratio of the average thickness of the resin composition on one (surface) surface of the fiber substrate after curing to the average thickness of the resin composition on the other (back) surface of the fiber substrate after curing, which means that the difference in their respective average thicknesses is small. By so defining, the difference in curing shrinkage of the resin composition on the surface and back of the prepreg can be reduced, effectively reducing the occurrence of deformation. In addition, it also has the following effect: after the resin composition is cured, the difference in thermal expansion caused by temperature changes is reduced. Therefore, in the room temperature-high temperature treatment-cooling process during component installation, the "warping" caused by the release of strain above the glass transition temperature and the "warping" caused by the difference in thermal expansion caused by heating-cooling can be appropriately suppressed, which can make the installation operation more efficient.

Conventionally, the focus has been on achieving uniformity in the total amount of resin deposited on a fiber substrate. The ratio of the average thickness of the resin composition present on one (front) surface of the fiber substrate after curing to the average thickness of the resin composition present on the other (back) surface of the fiber substrate after curing has not been considered to have a significant effect and has tended to be ignored. However, in the case of prepregs satisfying the above formula (1), the influence of this ratio is more significant than previously thought. The present invention effectively reduces warpage by adjusting this ratio.

According to the metal-clad laminate of the present invention, the warpage amount measured by the following measuring method can be 2.0 mm or less.

(Measurement method of warpage)

The copper foil of the outer layer of a metal-clad laminate is completely etched, leaving only the laminate. The laminate is then placed horizontally and dehydrated at 80°C for two hours, then allowed to return to room temperature at 20°C. A 250 mm square test piece is cut from the center of the resulting laminate. This test piece is suspended at 20°C at any one of its four corners, and the warpage at the other three points is measured. This procedure is repeated for all four corners, and the maximum warpage value is taken as the warpage value.

The fiber base material and the resin composition contained in the prepreg will be described below.

〔Fiber base material〕

As the fiber substrate, well-known fiber substrates used in various laminates for electrical insulating materials can be used. Examples of the material of the fiber substrate include: natural fibers such as paper and cotton linter; inorganic fibers such as glass fibers and asbestos; organic fibers such as aromatic polyamide, polyimide, polyvinyl alcohol, polyester, tetrafluoroethylene, and acrylonitrile-based fibers; and mixtures thereof. Among these, glass cloth is preferred from the perspective of flame retardancy. Examples of glass cloth include: glass cloth using E glass, C glass, D glass, S glass, etc., or glass cloth made by bonding short fibers with an organic binder; glass cloth made by mixing glass fibers and cellulose fibers (Japanese: mixed sand), etc. More preferably, glass cloth using E glass is used.

These fiber substrates have the form of woven fabrics, non-woven fabrics, rovings, chopped strand mats or surface mats. It should be noted that the material and shape can be selected according to the purpose and performance of the target molded product. One type can be used alone, or two or more materials and shapes can be combined as needed.

The materials and shapes of the two or more fiber base materials may be the same or different. When two or more fiber base materials are used, the average thickness B of the fiber base material is the sum of the average thicknesses of the two or more fiber base materials.

The fiber base material is not particularly limited and may be a single-layer fiber base material. Here, a single-layer fiber base material refers to a fiber base material composed only of entangled fibers. If a non-entangled fiber base material exists, it is classified as a multi-layer fiber base material.

[Resin composition]

The resin composition is attached to the fiber base material in the prepreg and penetrates into the fiber base material. There are also cases where the resin composition exists on the surface of the fiber base material.

The resin composition preferably contains a thermosetting resin. In addition to the thermosetting resin, it may also contain a curing agent, a curing accelerator, an inorganic filler, an organic filler, a coupling agent, a leveling agent, an antioxidant, a flame retardant, a flame retardant auxiliary, a thixotropy-imparting agent, a tackifier, a thixotropy-imparting agent, a flexible material, a surfactant, a photopolymerization initiator, etc. as needed, preferably containing at least one selected from these.

Hereinafter, each component that the resin composition may contain will be described in order.

(Thermosetting resin)

As a thermosetting resin, it is preferred that the melt viscosity of the resin can be changed by the degree of cure of the resin in any temperature region. As the thermosetting resin, epoxy resin, phenolic resin, unsaturated imide resin, cyanate resin, isocyanate resin, benzoxazine resin, oxetane resin, amino resin, unsaturated polyester resin, allyl resin, dicyclopentadiene resin, silicone resin, triazine resin, melamine resin etc. can be listed. In addition, it is not particularly limited to these, and known thermosetting resins can be used. These can be used alone or in combination of two or more. Among these, from the viewpoint of formability and electrical insulation, epoxy resin and unsaturated imide resin are preferred.

Examples of the epoxy resin include cresol novolac epoxy resins, phenol novolac epoxy resins, naphthol novolac epoxy resins, aralkyl novolac epoxy resins, biphenyl novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol T epoxy resins, bisphenol Z epoxy resins, tetrabromobisphenol A epoxy resins, biphenyl epoxy resins, tetramethylbiphenyl epoxy resins, triphenyl epoxy resins, tetraphenyl epoxy resins, naphthol aralkyl epoxy resins, naphthalenediol aralkyl epoxy resins, naphthol aralkyl epoxy resins, fluorene epoxy resins, epoxy resins having a dicyclopentadiene skeleton, epoxy resins having an ethylenically unsaturated group in the skeleton, and alicyclic epoxy resins.

Furthermore, as the epoxy resin, a halogenated epoxy resin may be used from the viewpoint of flame retardancy. The epoxy resin may be used alone or in combination of two or more from the viewpoint of insulation reliability and heat resistance.

The epoxy equivalent of the epoxy resin is not particularly limited, but is preferably 60 to 400 g/mol, more preferably 70 to 300 g/mol, and even more preferably 80 to 250 g/mol from the viewpoint of heat resistance.

Commercially available products of epoxy resins include: "EPICLON (registered trademark) N-660" (manufactured by DIC Corporation), which is a cresol novolac-type epoxy resin; "EPICLON (registered trademark) N-770" (manufactured by DIC Corporation), which is a phenol novolac-type epoxy resin; "EPICLON (registered trademark) 840S" (manufactured by DIC Corporation), "jER828EL", and "YL980" (all manufactured by Mitsubishi Chemical Corporation), which are bisphenol A-type epoxy resins.

The epoxy resin is not particularly limited, but from the perspective of imparting flexibility, it may be an epoxy resin having two or more epoxy groups in one molecule and a structural unit derived from an alkylene glycol having 3 or more carbon atoms in its main chain. Furthermore, from the perspective of further improving flexibility, two or more structural units derived from an alkylene glycol having 3 or more carbon atoms may be continuously repeated.

The alkylene glycol having 3 or more carbon atoms is preferably an alkylene glycol having 4 or more carbon atoms. The upper limit of the carbon number is not particularly limited, but is preferably 15 or less, more preferably 10 or less, and even more preferably 8 or less.

Furthermore, as the epoxy resin, a halogenated epoxy resin can be used from the viewpoint of flame retardancy.

Examples of unsaturated imide resins include maleimide compounds. Preferred maleimide compounds are those having at least two N-substituted maleimide groups per molecule. From the perspective of solubility in organic solvents and mechanical strength, the weight-average molecular weight (Mw) of the maleimide compound is preferably 400 to 3,500, more preferably 600 to 1,000, and even more preferably 650 to 950.

Examples of maleimide compounds include maleimide compounds having an aliphatic hydrocarbon group between any two maleimide groups among a plurality of maleimide groups, or maleimide compounds containing an aromatic hydrocarbon group between any two maleimide groups among a plurality of maleimide groups (hereinafter referred to as maleimides containing aromatic hydrocarbon groups). Among these, maleimides containing aromatic hydrocarbon groups are preferred from the viewpoints of heat resistance, dielectric properties, glass transition temperature, thermal expansion coefficient, and moldability. The maleimide containing aromatic hydrocarbon groups may contain an aromatic hydrocarbon group between any two maleimide groups selected arbitrarily.

The maleimide compound is preferably an aromatic hydrocarbon group-containing maleimide represented by the following general formula (II).

[Chemistry 2]

(In the formula, ^R1 and ^R2 each independently represent an aliphatic hydrocarbon group having 1 to 5 carbon atoms or a halogen atom. ^X1 represents an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -O-, -C(=O)-, -S-, -SS-, or a sulfonyl group. m and n each independently represent an integer from 0 to 4.)

Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by ^R1 and ^R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and an n-pentyl group. From the viewpoint of heat resistance, dielectric properties, glass transition temperature, thermal expansion coefficient, and moldability, the aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and a methyl group and an ethyl group are more preferred.

Examples of the halogen atom represented by R ¹ and R ² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the alkylene group having 1 to 5 carbon atoms represented by ^X1 include methylene, 1,2-dimethylene, 1,3-trimethylene, 1,4-tetramethylene, and 1,5-pentamethylene. From the viewpoints of heat resistance, dielectric properties, glass transition temperature, thermal expansion coefficient, and moldability, the alkylene group is preferably an alkylene group having 1 to 3 carbon atoms, and more preferably a methylene group.

Examples of the C2-5 alkylidene group represented by ^X1 include ethylidene, propylidene, isopropylidene, butylidene, isobutylidene, pentylidene, and isopentylidene. Among these, isopropylidene is preferred from the viewpoints of heat resistance, dielectric properties, glass transition temperature, thermal expansion coefficient, and moldability.

Among the above-mentioned options, X ¹ is preferably an alkylene group having 1 to 5 carbon atoms or an alkylidene group having 2 to 5 carbon atoms, and more preferably an alkylene group having 1 to 5 carbon atoms. Further preferred groups are as described above.

The maleimide compound is more preferably a maleimide compound modified with a monoamine compound or a diamine compound having an acidic substituent.

Examples of the acidic substituent of the monoamine compound having an acidic substituent include a hydroxyl group, a carboxyl group, and a sulfonic acid group, and a hydroxyl group is preferred.

Examples of monoamine compounds having an acidic substituent include o-aminophenol, m-aminophenol, p-aminophenol, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, 3,5-dihydroxyaniline, and 3,5-dicarboxyaniline. Among these, m-aminophenol, p-aminophenol, p-aminobenzoic acid, and 3,5-dihydroxyaniline are preferred from the perspective of solubility and reactivity, while o-aminophenol, m-aminophenol, and p-aminophenol are preferred from the perspective of heat resistance. As the monoamine compound having an acidic substituent, m-aminophenol can be selected from the above.

The diamine compound is preferably a diamine compound having at least two benzene rings, more preferably a diamine compound having at least two benzene rings in a linear chain between two amino groups, and still more preferably a diamine compound represented by the following general formula (III).

[Chemistry 3]

(In the formula, ^X2 is a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, -O-, a sulfonyl group, -C(=O)-, a fluorenylene group, or a phenylenedioxy group. ^R3 and ^R4 are each independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogen atom, a hydroxyl group, a carboxyl group, or a sulfonic acid group. v and w are each independently an integer from 0 to 4.)

Examples of the C1-5 alkylene group represented by ^X2 include a methylene group, an ethylene group, a propylene group, etc. The alkylene group is preferably an C1-3 alkylene group, and more preferably a methylene group.

Examples of the C2-5 alkylidene group represented by ^X2 include ethylidene, propylidene, isopropylidene, butylidene, isobutylidene, pentylidene, and isopentylidene. The alkylidene group is preferably isopropylidene.

X ² is preferably a single bond, an alkylene group having 1 to 5 carbon atoms, or -O-, and more preferably a single bond.

Examples of the C1-5 alkyl group represented by ^R3 and ^R4 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and n-pentyl. The alkyl group is preferably a C1-3 alkyl group, and more preferably a methyl group.

Examples of the alkoxy group having 1 to 5 carbon atoms represented by R ³ and R ⁴ include methoxy, ethoxy, and propoxy. The alkoxy group is preferably a methoxy group.

Examples of the halogen atom represented by R ³ and R ⁴ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

v and w are each independently preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 1.

Examples of the diamine compound include 3,3'-dimethyl-4,4'-diamino-1,1'-biphenyl (o-tolidine) and 2,2'-dimethyl-4,4'-diamino-1,1'-biphenyl. Among these, 3,3'-dimethyl-4,4'-diamino-1,1'-biphenyl (o-tolidine) is preferred.

(Curing Agent)

When the thermosetting resin is an epoxy resin, examples of the curing agent include phenolic curing agents, cyanate curing agents, acid anhydride curing agents, amine curing agents, and curing agents for epoxy resins such as compounds containing active ester groups. It should be noted that when the thermosetting resin is a resin other than an epoxy resin, substances known as curing agents for the thermosetting resin can be used. The curing agent may be used alone or in combination of two or more.

The phenolic curing agent is not particularly limited, but preferably includes a cresol novolac curing agent, a biphenyl curing agent, a phenol novolac curing agent, a naphthyl ether curing agent, a triazine skeleton-containing phenolic curing agent, and the like.

The hydroxyl equivalent of the phenolic curing agent is not particularly limited, but is preferably 80 to 150 g/eq, more preferably 80 to 130 g/eq, and even more preferably 90 to 120 g/eq.

Commercially available products of phenolic curing agents include: cresol novolac-type curing agents such as KA-1160, KA-1163, and KA-1165 (all manufactured by DIC Corporation); biphenyl-type curing agents such as MEH-7700, MEH-7810, and MEH-7851 (all manufactured by Meiwa Chemicals Co., Ltd.); phenol novolac-type curing agents such as PHENOLITE (registered trademark) TD2090 (manufactured by DIC Corporation); naphthyl ether-type curing agents such as EXB-6000 (manufactured by DIC Corporation); and phenolic curing agents containing a triazine skeleton such as LA3018, LA7052, LA7054, and LA1356 (all manufactured by DIC Corporation).

The cyanate curing agent is not particularly limited, and examples thereof include bisphenol A dicyanate, polyphenol cyanate (oligomeric [3-methylene-1,5-phenylene cyanate)], 4,4'-methylenebis(2,6-dimethylphenylcyanate), 4,4'-ethylenediphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylene))benzene, bis(4-cyanatephenyl)sulfide, and bis(4-cyanatephenyl)ether.

The acid anhydride curing agent is not particularly limited, and examples thereof include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, 5-(2,5-dioxotetrahydro-3-furyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, and pyromellitic anhydride.

The amine-based curing agent is not particularly limited, and examples thereof include aliphatic amines such as triethylenetetramine, tetraethylenepentamine, and diethylaminopropylamine; and aromatic amines such as m-phenylenediamine and 4,4'-diaminodiphenylmethane.

In addition, urea resin or the like can also be used as a curing agent.

When the resin composition contains a curing agent, the content thereof is preferably 10 to 150 parts by mass, more preferably 10 to 100 parts by mass, and even more preferably 10 to 50 parts by mass, relative to 100 parts by mass of the thermosetting resin.

When the resin composition contains a curing agent, its content can be expressed as a functional group equivalent, and is preferably expressed in this manner. Specifically, the curing agent is preferably contained in the form of . The constant C varies depending on the type of functional group in the curing agent. When the functional group is a phenolic hydroxyl group, it is preferably 0.8 to 1.2, when it is an amino group, it is preferably 0.2 to 0.4, and when it is an active ester group, it is preferably 0.3 to 0.6.

When the thermosetting resin is an epoxy resin, the above formula becomes

(Curing Accelerator)

As a curing accelerator, any common curing accelerator used for curing the aforementioned thermosetting resins can be used. For example, when the thermosetting resin is an epoxy resin, examples of curing accelerators include imidazole compounds and their derivatives; phosphorus compounds; tertiary amine compounds; and quaternary ammonium compounds. From the perspective of accelerating the curing reaction, imidazole compounds and their derivatives are preferred.

Specific examples of imidazole compounds and their derivatives include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1,2-dimethylimidazole, 2-ethyl-1-methylimidazole, 1,2-diethylimidazole, 1-ethyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 4-ethyl-2-methylimidazole, 1-isobutyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4,5-dimethylimidazole, 1-cyanoethyl-2- ... Imidazole compounds such as hydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]ethyl-s-triazine, and 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine; 1-cyanoethyl-2-phenylimidazolium trimellitate; addition reaction products of the above imidazole compounds with trimellitic acid; addition reaction products of the above imidazole compounds with isocyanuric acid; and addition reaction products of the above imidazole compounds with hydrobromic acid. The imidazole compounds may be used alone or in combination of two or more.

When the resin composition contains a curing accelerator, the content thereof is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the thermosetting resin.

(Inorganic filler)

Inorganic fillers can reduce the thermal expansion coefficient and improve the coating strength. In addition, they can also improve impermeability and wear resistance. In addition, they are sometimes contained for the purpose of increasing the amount of the resin composition.

Examples of the inorganic filler include oxides such as silica, alumina, zirconia, mullite, and magnesia; hydroxides such as aluminum hydroxide, magnesium hydroxide, and hydrotalcite; nitride-based ceramics such as aluminum nitride, silicon nitride, and boron nitride; and natural minerals such as talc, montmorillonite, and saponite. It is preferred to use at least one selected from these. Among these, silica, alumina, and aluminum hydroxide are preferred, and silica and aluminum hydroxide are more preferred.

Examples of the silica include precipitated silica produced by a wet process with a high water content and dry-process silica produced by a dry process and containing almost no bound water. Examples of dry-process silica include crushed silica, fumed silica, and fused silica (fused spherical silica), depending on the production method.

The inorganic filler may be surface-treated with a silane coupling agent or other surface treatment agent to improve moisture resistance, or may be hydrophobized to improve dispersibility.

The inorganic filler can be appropriately selected according to the purpose. From the perspective of facilitating the formation of fine wiring, the specific surface area of the inorganic filler is preferably 1 to 50 m ² /g, more preferably 1 to 30 m ² /g, and even more preferably 1 to 15 m ² /g. The specific surface area of the inorganic filler can be determined by a measurement method commonly used by those skilled in the art, for example, by the BET method. The BET method is a method in which molecules with a known adsorption area are adsorbed on the surface of powder particles at the temperature of liquid nitrogen, and the specific surface area of the sample is determined from the amount of the molecules adsorbed. In specific surface area analysis, the most commonly used method is the BET method based on inert gases such as nitrogen.

The average primary particle size of the inorganic filler is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm, and further preferably 0.1 to 10 μm. Here, the "average primary particle size" does not refer to the average diameter of the aggregated particles, that is, the secondary particle size, but refers to the average particle size of the unaggregated monomers. The primary average particle size can be measured and obtained using a laser diffraction particle size distribution meter. In addition, the average primary particle size is the particle size at the point equivalent to 50% of the volume when the cumulative frequency distribution curve based on the particle size is obtained with the total volume of the particles as 100%.

When the resin composition contains an inorganic filler, its content is preferably 1 to 65% by mass, more preferably 10 to 60% by mass, and even more preferably 25 to 50% by mass of the total components of the resin composition (excluding the organic solvent). If it is 65% by mass or less, the viscosity of the resin composition can be suppressed to a low level, thereby improving workability.

It should be noted that inorganic filler widely exists the type of proportion less than resin component to the type of proportion greater than resin component, so above-mentioned content (quality %) can be converted into also considering " volume % " of proportion and represent. That is to say, although the content of inorganic filler is different according to adding purpose, it can also be said that it is preferably 0.1～65 volume %. When colored and not through purpose, there is the tendency that can bring into play sufficient effect as long as more than 0.1 volume %. On the other hand, when adding for the purpose of increment, by suppressing to be below 65 volume %, thereby having the tendency that viscosity will not excessively become high, easily suppress operability to decline when coordinating resin component. From the same viewpoint, the content of inorganic filler is more preferably 10～60 volume %, further preferably 25～50 volume %.

(Organic Solvent)

From the viewpoint of easy handling, the resin composition may contain an organic solvent. In this specification, a resin composition containing an organic solvent may be referred to as a resin varnish.

The organic solvent is not particularly limited, and examples thereof include alcohol solvents such as methanol, ethanol, propanol, butanol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, and 4-methyl-2-pentanone; ester solvents such as ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate; ether solvents such as tetrahydrofuran; aromatic solvents such as toluene, xylene, and mesitylene; nitrogen-containing solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; and sulfur-containing solvents such as dimethyl sulfoxide. Among these, ketone solvents are preferred from the viewpoints of solubility and appearance after coating, with cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone being more preferred, and methyl ethyl ketone being even more preferred.

The organic solvent may be used alone or in combination of two or more.

The content of the organic solvent is adjusted so that the nonvolatile component (also referred to as solid content) of the resin composition is preferably 20 to 85% by mass, more preferably 40 to 80% by mass, from the viewpoint of ease of coating.

(Method for preparing resin composition)

The method for preparing the resin composition (resin varnish) is not particularly limited, and a conventionally known method can be employed.

For example, the above components can be added to the above organic solvent and then mixed and stirred using various mixers. Examples of the mixer include those using ultrasonic dispersion methods, high-pressure collision dispersion methods, high-speed rotation dispersion methods, bead milling methods, high-speed shearing dispersion methods, and rotation-revolution dispersion methods.

(Method for producing prepreg)

The method for producing the prepreg is not particularly limited, and a known method for producing the prepreg may be employed. For example, the prepreg may be produced by impregnating or coating a fiber substrate with the resin composition and then semi-curing (B-staging) the prepreg by heating or the like.

The heating temperature during semi-curing (B-staging) is preferably a temperature above the boiling point of the organic solvent, which allows for efficient removal of the organic solvent, in order to simultaneously perform the solvent removal step. Specifically, it is preferably 80-200°C, and more preferably 140-180°C. It should be noted that, in the present invention, a prepreg obtained by semi-curing (B-staging) is considered a cured prepreg. That is, "curing" also includes "semi-curing."

Another method for producing a prepreg includes, for example, applying the resin composition to a release film, semi-curing (B-staging) the resin composition by heating or the like to form a film, and laminating the resin film onto a fiber substrate. This method is preferred because it easily satisfies the above formula (2).

The resin composition can be applied using a known coater such as a die coater, comma coater, bar coater, kiss coater, or roll coater, and these coaters can be appropriately selected depending on the desired resin film thickness.

Examples of lamination methods include lamination on a fiber substrate under reduced pressure by roll lamination or vacuum lamination. Roll lamination conditions include, for example, a heating temperature of 50 to 150°C and a pressure of 0.1 to 1.0 MPa/m. Vacuum laminator conditions include, for example, a heating temperature of 50 to 150°C, a pressing time of 10 to 120 seconds, and a pressure of 0.1 to 0.5 MPa.

Examples of release films include organic films such as polyethylene terephthalate (PET), biaxially oriented polypropylene (OPP), polyethylene, polyvinyl fluoride, and polyimide; films of copper, aluminum, and alloys of these metals; and films obtained by subjecting these organic or metal films to a release treatment using a release agent. These release films may be films subjected to a release treatment using a release agent.

The overall thickness of the prepreg can be appropriately adjusted depending on the thickness of the inner layer circuit, and is preferably 10 to 700 μm, more preferably 10 to 500 μm, further preferably 10 to 250 μm, and particularly preferably 10 to 150 μm from the viewpoint of formability and handleability.

The metal-clad laminate of the present invention uses the above-mentioned prepreg. Specifically, a metal-clad laminate is obtained by arranging metal foil for circuit formation on both sides of the above-mentioned prepreg. The metal of the metal foil is preferably copper, gold, silver, nickel, platinum, molybdenum, ruthenium, aluminum, tungsten, iron, titanium, chromium or an alloy containing at least one of these metal elements. As alloys, copper-based alloys, aluminum-based alloys, and iron-based alloys are preferred. Examples of copper-based alloys include copper-nickel alloys. Examples of iron-based alloys include iron-nickel alloys (42 alloys). Among these, copper, nickel, and 42 alloys are more preferred as metals, and copper is further preferred from the perspective of ease of use and cost. The thickness of the metal foil is not particularly limited and can be 3 to 210 μm, preferably 5 to 140 μm.

It should be noted that, instead of a metal foil for circuit formation, a metal foil having a resin layer corresponding to electroless copper plating performed by a semi-additive process or the like may be provided. The resin composition contained in the resin layer can be described in the same manner as the above-mentioned resin composition, and can be the same as or different from the above-mentioned resin composition. The resin composition is not particularly limited, but preferably contains an epoxy resin. The epoxy resin can be described in the same manner as described above.

[Printed wiring board]

The printed wiring board of the present invention uses the metal-clad laminate of the present invention.

The printed wiring board of the present invention can be manufactured by forming a wiring pattern on the metal-clad laminate. The method for forming the wiring pattern is not particularly limited, and examples thereof include known methods such as a subtractive process, a fully additive process, a semi-additive process (SAP), and a modified semi-additive process (m-SAP).

[Semiconductor Package]

The semiconductor package of the present invention includes the printed wiring board of the present invention, and more specifically, a semiconductor mounted on the printed wiring board of the present invention. The semiconductor package of the present invention can be manufactured by mounting a semiconductor chip, memory, etc. at a predetermined position on the printed wiring board of the present invention.

Example

The present invention will be further described in detail by the following examples, but these examples are not intended to limit the present invention. It should be noted that a1, a2, B, and warpage were measured using the prepregs or copper-clad laminates produced in each example according to the following methods.

(Measurement method of a1, a2 and B)

The prepreg was suspended in a dryer, and the temperature of the dryer was increased from 20°C to 160°C at a rate of 5°C/hour. After being held at 160°C for 30 minutes, the sample was placed in a container with a thickness of 0.01 mm (manufactured by Tokyo Thickness Co., Ltd.) as measured in accordance with JIS B 7524 (2008) [sheet shape: Type A].

Then, 100 parts by mass of bisphenol A liquid epoxy resin "jER (registered trademark) 815" (manufactured by Mitsubishi Chemical Corporation), which is a material for the casting resin, and 10 parts by mass of trimethyltetramine (manufactured by Wako Pure Chemical Industries, Ltd.) were stirred and injected into the above-mentioned container. After vacuum degassing for 3 minutes at a vacuum degree of 700 mmHg (93.3 kPa), it was cured at 40°C for 60 minutes and then at 60°C for 90 minutes. After curing, the cured product was taken out of the container, cut and mechanically polished to expose the cross section. The cross section was observed with a scanning electron microscope (SEM) to measure the thickness of the resin composition on one side of the fiber substrate, the thickness of the resin composition on the other side of the fiber substrate, and the thickness of the fiber substrate.

Regarding the measurement, 10 parts without obvious scratches, dents, and creases were measured, and their average values were calculated to obtain a1 (measured value), a2 (measured value), and B (measured value), respectively. The following correction was performed, and the obtained a1 (corrected value), a2 (corrected value), and B (corrected value) were used as a1, a2, and B in the above formulas (1) and (2), respectively.

-Calibration method-

The 0.01 mm thick strip was also observed using a scanning electron microscope (SEM). The thickness was measured at 10 locations in the same manner as above, and the average value was calculated. Using this average value and 0.01 mm, the correction coefficient α was calculated using the following formula (3). The calculated correction coefficient α was multiplied by a1 (measured value), a2 (measured value), and B (measured value), respectively, to obtain a1 (corrected value), a2 (corrected value), and B (corrected value).

α＝0.01mm/Thickness Average value of the measured thickness of the strip (3)

a1(corrected value)=a1(measured value)×α

a2(corrected value)=a2(measured value)×α

B (corrected value) = B (measured value) × α

(Measurement method of warpage)

Cut a 250 mm square test piece from the center of the metal-clad laminate. Fix and hang the test piece at any one of its four corners at 20°C, and measure the warpage at the other three points. Repeat this procedure for all four corners, and the maximum value is defined as the warpage (with copper foil).

On the other hand, the outer copper foil of the metal-clad laminate was entirely etched to leave only the laminate, which was then placed horizontally and dehydrated at 80°C for 2 hours. It was then allowed to return to room temperature at 20°C, and the warpage (without copper foil) was measured using the same method as above.

Example 1 (subtractive method)

The prepreg A and the copper-clad laminate were produced according to the following procedures.

(1. Preparation of Resin Varnish A)

35.8 g of o-tolidine, 469.5 g of bis(4-maleimidophenyl)methane, 35.7 g of m-aminophenol, and 360.0 g of dimethylacetamide were added to a container and reacted at 100° C. for 2 hours to obtain a solution A (solid content concentration: 60% by mass) containing a polyimide compound having a biphenyl skeleton in the molecule.

To 50 parts by mass of the obtained polyimide compound-containing solution A (solid content concentration: 60% by mass) were added 30 parts by mass of a phenol novolac-type epoxy resin (manufactured by DIC Corporation, trade name: EPICLON (registered trademark) N-770, epoxy equivalent: 188 g/eq), 20 parts by mass of a cresol novolac-type resin (manufactured by DIC Corporation, trade name: PHENOLITE (registered trademark) KA-1165, hydroxyl equivalent: 119 g/eq), 30 parts by mass of aluminum hydroxide (manufactured by Showa Denko K.K., trade name: HP-360), and fused silica (manufactured by Admatechs Co., Ltd., trade name: SC2050-KC, average primary particle size: 0.5 μm, BET specific surface area: 6.8 m ² ). 90 parts by mass of methyl paraben (Daiichi Kogyo Seiyaku Co., Ltd., trade name: G8009L) as a curing accelerator, and methyl ethyl ketone as a diluent were mixed to prepare a resin varnish A having a solid content concentration of 65% by mass.

(2. Preparation of Resin Film A)

The resin varnish A was coated onto a 580 mm wide PET film (manufactured by DuPont Film Co., Ltd., trade name: G-2) to a coating width of 525 mm and a thickness of 7 μm after drying, thereby producing a resin film A. The viscosity of this resin film A was measured using a rheometer "AR-200ex" (manufactured by TA Instruments Japan Co., Ltd., heating rate: 3°C/min, jig). The temperature at which the minimum melt viscosity was observed was 128°C.

(3. Preparation of Prepreg A)

Two pre-heated resin films A were placed against a pre-heated glass woven fabric (thickness 15 μm, basis weight 13 g/m ² , IPC#1017, substrate width 530 mm, manufactured by Nitto Bosho Co., Ltd.) as a fiber substrate from both sides under the following conditions. The pre-heated glass woven fabric was sandwiched between pressure rollers to impregnate the fiber substrate with the resin composition under pressure and laminate the film. The prepreg was then cooled with a cooling roller and wound up to produce a prepreg A.

The pressure roll conditions were set to a roll temperature of 100°C, a linear pressure of 0.2 MPa, and a speed of 2.0 m/min. Heating was performed using a halogen heater (UH-USF-CL-700, manufactured by USHIO Electric Co., Ltd.). The heating position on the side of the resin film A that came into contact with the fiber substrate was adjusted so that the center of the heater's heating surface was approximately 30 mm from the pressure roll, and the heating temperature reached 135°C at the center of the heating surface. The fiber substrate itself was also heated in the same manner, adjusted so that its temperature reached 140°C.

(4. Production of copper-clad laminates)

One sheet of the prepreg A was cut into 530 mm square pieces and sandwiched between 540 mm square copper foils (Mitsui Kinzoku Co., Ltd., trade name: MT-18EX-5). This was then sandwiched between 530 mm square SUS panels with a thickness of 1.8 mm. The prepreg was then held for 90 minutes in a vacuum atmosphere at a product temperature range of 60 to 160°C at a heating rate of 2 to 3°C/minute, a product pressure of 2.5 MPa, and a maximum holding temperature of 220°C, thereby producing a copper-clad laminate A.

Table 1 shows the above measurement results.

Example 2 (semi-additive method)

One prepreg A obtained in Example 1 was cut into 530 mm square pieces and sandwiched between the resin layer side of two 540 mm square pieces of copper foil for forming fine wiring corresponding to SAP (manufactured by Hitachi Chemical Co., Ltd., trade name: PF-EL5, copper foil provided with a resin layer containing epoxy resin, the resin layer having a thickness of 4 μm).

Then, it was clamped with SUS panels of 1.8 mm thickness and 530 mm square, and maintained for 90 minutes under the conditions of a vacuum atmosphere, a product pressure of 2.5 MPa, a product temperature of 60 to 160°C in a heating rate of 2 to 3°C/minute, and a maximum holding temperature of 220°C to obtain a laminated board with a resin layer corresponding to SAP.

The outer copper foil of the resulting laminate with the SAP-corresponding resin layer was removed by etching to expose the SAP-corresponding resin layer. Decontamination treatment was then performed using a decontamination treatment solution (manufactured by Atotech) under standard conditions. Electroless copper plating was then performed using an electroless copper plating solution (manufactured by Atotech) under standard conditions, and electroplating was further performed until the copper thickness reached 20 μm, thereby producing a copper-clad laminate B.

Example 3

In the same manner as in Example 1, a resin varnish A was prepared.

This resin varnish A was adjusted to a coating width of 525 mm and a thickness of 50 μm after drying, and coated on a 580 mm wide PET film (manufactured by Teijin DuPont Film Co., Ltd., trade name: G-2) to produce a resin film C. The temperature exhibiting the lowest melt viscosity of this resin film was 121°C.

Prepreg C was prepared by laminating the prepreg C on a glass woven fabric (88 μm in thickness, 104 g/m ² in basis weight, IPC#2116, 530 mm in width: manufactured by Nitto Bosho Co., Ltd.) as a fiber substrate in the same manner as in Example 1.

A copper-clad laminate C was produced in the same manner as in Example 1 except that the heating rate in the product temperature range of 60°C to 160°C was changed to 1.0 to 1.5°C/min for one of the obtained prepregs C. Table 1 shows the measurement results.

Comparative Example 1

In Example 1, two types of resin films A were prepared: resin film D1, which was adjusted to a thickness of 7 μm after drying, and resin film D2, which was adjusted to a thickness of 10 μm after drying. The same procedures were followed, except that resin films D1 and D2 were used instead of the two resin films A in the preparation of prepreg A, to produce a copper-clad laminate D. The results of the above measurements are shown in Table 1.

Comparative Example 2

In Example 3, two types of resin films C were prepared: resin film E1, which was adjusted to have a thickness of 25 μm after drying, and resin film E2, which was adjusted to have a thickness of 50 μm after drying. The same procedures were followed, except that resin films E1 and E2 were used in place of the two sheets of resin film A in the preparation of prepreg A, to produce a copper-clad laminate E. The results of the above measurements are shown in Table 1.

Reference Example 1

In Example 3, a copper-clad laminate F was produced in the same manner except that, in the production of resin film C, two sheets of resin film F were used instead of two sheets of resin film A in the production of prepreg A. The results of the above measurements are shown in Table 1.

[Table 1]

Table 1

In Examples 1 and 2, the warpage was significantly reduced both with and without copper foil compared to Comparative Example 1. In Example 3, the warpage was significantly reduced both with and without copper foil compared to Comparative Example 2.

It should be noted that in Reference Example 1, the average thicknesses a1 and a2 of the resin composition present on the fiber substrate surface are smaller than those of the fiber substrate, that is, the proportion of the resin composition in the overall prepreg is small. Therefore, it is believed that the strain caused by the difference between the front and back surfaces relative to the substrate is small, and the impact on the warpage is small. Since the impact on the problem of reducing the warpage is small, it is not particularly relevant to effectively solving the problem. This shows that the effect of the present invention in reducing warpage is effectively exerted when the conditions of the above formula (1) are met.

Explanation of symbols

a1 Average thickness of the resin composition on one side of the fiber substrate after curing

a2 Average thickness of the resin composition on the other side of the fiber substrate after curing

B Average thickness of fiber substrate

Claims (7)

1. A metal-clad laminate obtained by providing metal foil on both sides of a prepreg, wherein the prepreg is a resin composition attached to a fiber substrate and satisfies the following formula (1’), wherein the resin composition present on the surface and back side of the fiber substrate is the same and further satisfies the following formula (2’), wherein the resin composition contains 1% to 60% by mass of inorganic filler in all components of the resin composition except for organic solvents. 0.12＜{(a1+a2)/2}/B≤0.45(1’) 0.9≤a1/a2≤1.15(2’) In the above formula, a1 is the average thickness of the resin composition on one side of the fiber substrate after curing, a2 is the average thickness of the resin composition on the other side of the fiber substrate after curing, and B is the average thickness of the fiber substrate, which is 5μm to 30μm. 2. The metal-clad laminate according to claim 1, wherein the fiber substrate is glass cloth. 3. The metal-clad laminate according to claim 1 or 2, wherein the fiber substrate is a single-layer fiber substrate. 4. The metal-clad laminate according to claim 1 or 2, wherein the resin composition contains a thermosetting resin. 5. The metal-clad laminate according to claim 1 or 2, wherein the resin composition contains at least one thermosetting resin selected from epoxy resin, phenolic resin, unsaturated imide resin, cyanate ester resin, isocyanate ester resin, benzoxazine resin, oxetane resin, amino resin, unsaturated polyester resin, allyl resin, dicyclopentadiene resin, silicone resin, triazine resin, and melamine resin. 6. A printed wiring board using the metal-clad laminate according to any one of claims 1 to 5. 7. A semiconductor package comprising the printed wiring board of claim 6.