JPH0219995B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paper-based metal foil-clad laminate that has excellent metal foil peel strength at room temperature and high temperature, excellent solder heat resistance, electrical insulation properties, etc., and less warpage and twisting. Metal foil-covered laminates used in printed circuit boards are required to have excellent heat resistance against soldering temperatures that reach 260°C, excellent electrical insulation properties, and peel strength of the metal foil. In addition, in recent years, the density and speed of printed wiring board processing have rapidly increased, and high reliability is required in the soldering dip process, the component mounting process using a soldering iron, and the like. In such a process, stress is often applied to the metal foil in a high temperature range corresponding to the solder melting temperature, so that peeling of the metal foil is likely to occur. Therefore, peel strength is required to prevent the metal foil from peeling off in a high temperature range corresponding to the solder melting temperature. Further, it is required that large warpage does not occur during the printing process, heating process, or automatic insertion process of parts, and that the warpage is extremely small. For this reason, the present inventors previously proposed in Japanese Patent Application Laid-Open No. 56-8227 that an adhesive was used to improve the adhesion between a curable resin and metal foil that does not generate by-products such as gas or liquid during the curing reaction process. We proposed the use of amine-curing epoxy resin. In this case, the amine-curing epoxy resin was shown to exhibit well-balanced performance as an adhesive for printed circuit boards, including peel strength for metal foil, soldering heat resistance, and electrical insulation properties. However, in the metal foil-clad laminate using an amine-curing epoxy resin adhesive, the metal foil tends to peel off when stress is applied in a high temperature range corresponding to the solder melting temperature. When the peeling state of the metal foil at this high temperature was observed using a scanning electron microscope, it was found that it was cohesive failure within the adhesive layer. The inventors of the present invention have conducted further studies to solve this problem, and have found that by adding a certain amount of inorganic filler to the amine-curing epoxy resin adhesive, the above-mentioned drawbacks can be eliminated and the warpage can be improved. It was discovered that a metal foil-clad laminate with less twisting can be obtained, leading to the present invention. The present invention comprises a plurality of paper base layers impregnated with a curable resin that does not substantially generate reaction by-products such as gas or liquid during the curing reaction process, and a paper base layer laminated on at least one surface of the paper base layer with an adhesive layer interposed therebetween. In a metal foil-clad laminate for a printed circuit board having a metal foil,
The adhesive layer contains 10 to 200 parts by weight based on 100 parts by weight of the resin.
The adhesive layer is made of an amine-curing epoxy resin containing part by weight of an inorganic filler, and the thickness of the adhesive layer is 5 to 50% by weight.
The paper-based metal foil-clad laminate is characterized by having a thickness in the range of 150 μm. Inorganic fillers used in the present invention include metal oxides, metal hydroxides, metal carbonates, clay minerals, and silicate minerals. Examples of metal oxides include silica, magnesium oxide, aluminum oxide, zinc oxide,
Examples of metal hydroxides include aluminum hydroxide and magnesium hydroxide. Examples of metal carbonates include calcium carbonate and magnesium carbonate. Clay minerals include kaolin and montmorillonite. ,
There are talc, mica, baked products thereof, and those surface-treated with organic silane, and examples of silicate minerals include calcium silicate, magnesium silicate, aluminum silicate, and potassium aluminum silicate. A mixture of two or more types of inorganic fillers may also be used. These inorganic fillers have an average particle size (C ₅₀ ) of
The thickness is preferably 10 μm or less, preferably 2 μm or less. 10μm
If this value is exceeded, there is a risk that the filler will separate and settle in the adhesive, and the wettability of the adhesive to fine irregularities on the surface of the metal foil mat, in particular, will be impaired. These inorganic fillers are contained in an amount of 5 to 200 parts by weight, preferably 10 to 200 parts by weight, per 100 parts by weight of the epoxy resin.
It is blended in an amount of 100 parts by weight, more preferably 20 to 60 parts by weight. If it is less than 5 parts by weight, the effect is generally poor, and if it exceeds 200 parts by weight, the peel strength of the metal foil decreases and the soldering heat resistance when moisture is absorbed is impaired. Further, it is preferable that the hardness of the inorganic filler is 5 or less when expressed by Mohs hardness, and care must be taken because if the Mohs hardness is greater than 5, there is a risk of abrasion and damage to the die during punching. Among these inorganic fillers, clay minerals have a layered structure and are thought to improve the cohesive failure strength when peeling off metal foil, and among metal oxides, magnesium oxide has a hardening resin that is unsaturated. In the case of polyester resin, it is thought that it also improves the adhesion between the impregnated base material laminate and the adhesive layer, and both are preferred. Also, Japanese Patent Application No. 55-133249 (Japanese Patent Application No. 57-57657)
As proposed by the present inventors in , it is important to reduce the average residual stress in the adhesive layer of a metal foil-clad laminate in order to obtain a metal foil-clad laminate with improved warpage and twisting. Among these inorganic fillers, plate-shaped inorganic fillers such as talc and kaolin have a large effect of reducing the average residual stress of the adhesive layer, and therefore have a large effect of improving warpage and twisting. Furthermore, by incorporating an inorganic filler, it is expected that the solvent resistance of the adhesive layer will be improved. The epoxy resin used as an adhesive in the present invention is a compound having a bifunctional or higher epoxy group, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic type epoxy resin, etc. These can be used alone or in a mixture of two or more. Amine-based hardeners are used as hardeners for epoxy resin adhesives. Examples include aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, and polyoxypropylenediamine;
N-aminoethylpiperazine, menzendiamine, isophoronediamine, bis(4-amino-3
Examples include alicyclic polyamines such as -methylcyclohexyl)methane; aromatic polyamines such as metaphenylene dianine and diaminodiphenylsulfone; and polyamide amines synthesized from dimer acid and aliphatic polyamines such as ethylenediamine. 2
Mixtures of more than one species may also be used. The use of an acid anhydride for curing the epoxy resin of the adhesive layer is disadvantageous because it requires the use of a solvent, a high reaction temperature, or a long reaction time. Also, a compound having a trifunctional or more functional epoxy group,
For example, when tetraglycidyl-1,3-bisaminomethylcyclohexane, triglycidyl isocyanurate, etc. are used in combination with a difunctional epoxy compound, the peel strength of the metal foil at high temperatures is improved. However, since warping and twisting of the metal foil-clad laminate tends to increase, the blending of the inorganic filler is particularly important in this case. The adhesive can be applied to the metal foil using an appropriate device such as a normal roll coater, blade coater, or wire bar coater. The thickness is adjusted to be in the range of 5 to 150 μm, preferably 30 to 80 μm. If this thickness is less than 5 μm, the soldering heat resistance may deteriorate, and if it exceeds 150 μm, it may adversely affect the warpage of the metal foil-clad laminate, cracks may occur in the adhesive during punching, or there may be damage to the inside of the hole. The metal foil gets stuck more often. The resin used for impregnating the paper base material in the present invention is
A curable resin that does not substantially generate reaction by-products such as gas or liquid during the curing reaction process, and includes radical polymerization types such as unsaturated polyester resins, diallyl phthalate resins, and vinyl ester resins, and addition reaction types such as epoxy resins. including. Resins that produce gaseous or liquid reaction byproducts require high molding pressure during curing because the byproducts can damage the bond between the adhesive layer and the resin layer, and metal foil-clad laminates cannot be manufactured using a continuous method. It is unsuitable as a resin for manufacturing. On the other hand, the resin is impregnated with a resin liquid while continuously supplying the required number of long base materials,
It is suitable for producing a metal foil-clad laminate by a so-called pressureless continuous method in which these are overlapped, metal foil coated with an adhesive is laminated, and then cured in a pressureless state. Among these, unsaturated polyester resins have the structural formula of the unsaturated polyester chain, for example It includes generally well-known resins such as , and flame-retardant resins in which halogen is introduced into the polyester chain. Therefore, the raw material polyols for unsaturated polyester include ethylene glycol, propylene glycol, diethylene glycol, 1,4
-butanediol, 1,5-petanediol, bisphenol A propylene oxide adduct,
Saturated polybasic acids such as 2,2-dibromoneopetyl glycol include phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, azelaic acid,
Unsaturated polybasic acids such as chlorendoic acid, tetrabromo phthalic anhydride, and tetrachlorophthalic anhydride, as well as maleic anhydride and fumaric acid, are generally used, and are a mixture of these and a crosslinking monomer. For example, the structural formula of so-called vinyl ester resin is Mixtures of epoxy acrylates with two or more terminal acryloyl or methacryloyl groups and crosslinking monomers, and mixtures of diallyl phthalate resins and crosslinking monomers can also be used. Styrene is commonly used as a crosslinking monomer, but other examples include α-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, alkyl acrylate or methacrylate having 1 to 10 carbon atoms, diallyl phthalate, triallyl cyanurate, etc. Monomers can also be used. Organic peroxides are commonly used as curing catalysts for radial polymerization type curable resins, and in particular, peroxyketals and peroxy ester,
One or more peroxides selected from dialkyl peroxides are preferred from the viewpoint of soldering heat resistance, electrical insulation properties, and peel strength of metal foil. Therefore, preferred catalysts include peroxyketals such as 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, n- Butyl-4,4-bis(t-butylperoxy)valerate, peroxy esters such as t-butylperoxyacetate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, t-
Examples of butyl peroxybenzoate and dialkyl peroxide include di-t-butyl peroxide and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3. Curing by heating is common, but curing by light, electron beams, and radiation can also be employed. The epoxy resin used for impregnating the base material is preferably bisphenol A type, and the curing agent is not limited to the amine-based curing agent for the epoxy resin used as the adhesive described above, but liquid acid anhydrides can also be used. Can be done. The resin composition used for impregnating the base material may also contain various fillers, colorants, flame retardants (reactive type and additive type), and flame retardant aids, if necessary. Examples of the paper base material used in the present invention include kraft paper, linter paper, and mixed paper thereof. As the metal foil, electrolytic copper foil, rolled copper foil, aluminum foil, electrolytic iron foil, etc. are used. If a surface treatment agent, especially a silane coupling agent, is applied to the surface of the metal foil before applying the agent, a product with even better peel strength of the metal foil can be obtained. As the silane capping agent, any silane capping agent that is generally used for joining surfaces between inorganic and organic materials can be used, but alkoxysilanes having an epoxy group, an amino group, or a mercapto group are preferred. The metal foil-clad laminate of the present invention can be produced by either batch or continuous production methods, but as mentioned above, it is particularly advantageous to produce it by the pressureless continuous production method. It is also possible to manufacture the metal foil-clad laminate of the present invention by manufacturing the resin laminate portion in advance in a continuous manner and then laminating the metal foil in a batch manner. The metal foil-clad laminate obtained by the method described above is applicable not only to single-sided metal foil-clad laminates but also to double-sided metal foil-clad laminates. It has excellent heat resistance, electrical insulation, etc., less warpage and twisting, and fully satisfies the automation and labor-saving demands of printed wiring board processing manufacturers and set manufacturers. Next, the present invention will be explained with reference to examples. Example 1 Five sheets of commercially available kraft paper (MKP-150, manufactured by Tomegawa Paper Industries) pretreated with a suspension of a mixture of melamine resin (Nicaresin 305 manufactured by Nippon Carbide Industries) and oleyl alcohol were transported while continuously conveying them. 1.1 as a curing catalyst to 100 parts by weight of unsaturated polyester resin (Polymer 6305 manufactured by Takeda Pharmaceutical Co., Ltd.)
-bis(t-butylperoxy)-3,3,5-
Impregnated with a resin solution containing 1 part by weight of trimethylcyclohexane (Perhexane 3M manufactured by Nihon Yushi Co., Ltd.),
As well as overlapping using two roll pairs,
A 1% ethanol solution of γ-glycidoxypropyltrimethylsilane (A187 manufactured by Union Carbide) was added as a silane coupling agent to a commercially available electrolytic copper foil (T-7 manufactured by Fukuda Metal Foil Industries) that was continuously unwound. was applied thinly and then dried continuously, and as adhesives, a bisphenol type epoxy resin with an epoxy equivalent of 190 (Epicote 828 manufactured by Ciel Chemical Co., Ltd.), isophorone diamine with an active hydrogen equivalent of 41, and calcined kaolin (Satenton No. manufactured by Hayashi Kasei Co., Ltd.) were used as adhesives. .1)
A mixture of 100:24:40 by weight was applied to a thickness of 50 μm using a blade coater, and then passed through a tunnel furnace for adhesive heat treatment at 130°C for 3 minutes. A film that was slightly sticky to the touch was simultaneously laminated on one side, and then a 50 μm thick polyester film was laminated on the other side, and the film was heated in a tunnel-shaped hot air oven at a temperature of 110°C for 15 minutes. after cutting.
Further heat treatment was performed at 150°C for 10 minutes to obtain a single-sided copper foil-clad laminate with a thickness of about 1.6 mm. Its performance is shown in Table 1. Example 2 As adhesives, bisphenol A type epoxy resin (Epicote 828), isophoronediamine and silane-treated talc (Crystallite manufactured by Ryumori Co., Ltd.) were used as adhesives.
CRS6002) with a weight ratio of 100:24:40, and in the same manner as in Example 1, the thickness was approx.
A 1.6 mm single-sided copper foil-clad laminate was obtained. Its performance is shown in Table 1. Example 3 As an adhesive, bisphenol A type epoxy resin (Epicote 828), isophorone diamine and magnesium oxide (Kyowa Kagaku Kyomag) were used.
30) in a weight ratio of 100:24:40, and in the same manner as in Example 1, a single-sided copper foil-clad laminate with a thickness of about 1.6 mm was obtained. Its performance is shown in Table 1. Comparative Example 1 A single-sided adhesive with a thickness of about 1.6 mm was prepared in the same manner as in Example 1 using a bisphenol A type epoxy resin (Epicote 828) and isophorone diamine in a weight ratio of 100:24 as the adhesive. A copper foil-clad laminate was obtained. Its performance is shown in Table 1. Comparative Example 2 As adhesives, bisphenol A type epoxy resin (Epicoat 828) and tetraglycidyl-1,
Weight ratio of 3-bisaminomethylcyclohexane (ELM434 manufactured by Sumitomo Chemical) and isophoronediamine
A single-sided copper foil-clad laminate with a thickness of about 1.6 mm was obtained in the same manner as in Example 1 using a laminate with a ratio of 80:20:27.
Its performance is shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A paper substrate comprising a plurality of paper base layers impregnated with a curable resin that does not substantially generate reaction by-products such as gas or liquid during the curing reaction process, and an adhesive layer on at least one surface of the paper base layers. In a metal foil-clad laminate for a printed circuit board having a metal foil laminated with a metal foil, the adhesive layer is made of an amine-curing epoxy resin containing 10 to 200 parts by weight of an inorganic filler based on 100 parts by weight of the resin, A paper-based metal foil-clad laminate, characterized in that the thickness of the adhesive layer is in the range of 5 to 150 μm. 2. The paper base metal foil-clad laminate according to claim 1, wherein the curable resin is a radical polymerizable resin such as an unsaturated polyester resin, diallyl phthalate resin, or vinyl ester resin. 3. The paper-based metal foil-clad laminate according to claim 1, wherein the curable resin is an addition reaction type such as an epoxy resin. 4. The paper base metal foil laminate according to claim 1, wherein the inorganic filler is a metal oxide such as magnesium oxide or aluminum oxide. 5. The paper-based metal foil-clad laminate according to claim 1, wherein the inorganic filler is a clay mineral such as kaolin, montmorillonite, or talc, or a fired product thereof. 6. The paper-based metal foil-clad laminate according to claim 1, wherein the inorganic filler is a silicate mineral such as magnesium silicate or calcium silicate. 7. The paper base metal foil laminate according to claim 1, wherein the inorganic filler is a metal hydroxide such as aluminum hydroxide or magnesium hydroxide. 8. The paper base metal foil clad laminate according to claim 1, wherein the inorganic filler is a metal carbonate. 9. The paper-based metal foil-clad laminate according to any one of claims 1 and 4 to 8, wherein the inorganic filler has a Mohs hardness of 5 or less.