Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-03-23
2002-10-08
Tucker, Philip (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C428S901000, C428S413000, C428S416000
Reexamination Certificate
active
06462147
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to epoxy resin compositions suitable for printed circuit boards and printed circuit boards using the same.
DESCRIPTION OF RELATED ART
With an increasing demand for more compactness and high performance of electronics devices, a higher density packaging of printed circuit boards to be included therein is progressing by provisions of multilayered and thin film lamination, a reduced diameter of plated throughholes, a narrow gap between holes and the like. Further, for printed circuit boards to be mounted in information terminal equipment such as a cellular phone, a mobile computer and so on, which requires plastic packaging directly to mount a MPU on its printed circuit board, or on other types of printed circuit boards suitable for various types of modules, it is demanded to be able to process a large quantity of information at a higher speed, thereby requiring a faster signal processing speed, a lower transmission loss, and further down-sizing in the components and system. Therefore, a finer pattern wiring is demanded more than ever with the trend for the higher density electronic packaging.
A substantially improved material having an excellent heat endurance and a high Tg is demanded for such printed circuit boards and those for a module which mount MPUs thereon in order for the reliability of their circuit connections to be ensured fully. However, because conventional resin materials having a high Tg tend to be mechanically hard and brittle, there is such a disadvantage that they have a low adhesiveness with a copper foil. Any resin material having a low adhesion with the copper foil tends to cause a peel-off and /or disconnection of wiring during molding and packaging of a substrate. Therefore, the adhesion property with the copper foil will become more vital with an advancing finer pattern wiring technique.
Conventional printed circuit boards using an epoxy resin group which is cured with dicyandiamide have been widely used. However, this epoxy resin group cured with dicyandiamide has a disadvantage that its hygroscopic property tends to increase. Therefore, it is becoming difficult to satisfy an increasing insulation reliability required for realizing a next-generation printed circuit board having a higher packaging density.
In contrast, a group which uses a multifunctional phenol resin as its curing agent has a low water absorption, and can provide for a printed circuit board having a Tg higher than 170° C. However, as mentioned previously, the resin material having a high Tg is hard and brittle, and still more, the multifunctional phenol cured group has a lower adhesive strength with a copper foil because of its lower polarity of the resin compared with the dicyandiamide cured group.
A method for improving the adhesive property between the copper foil and the resin which has been practiced heretofore includes a copper foil treatment using a coupling agent and the like as disclosed in JPA Laid-Open No. 54-48879. However, for such hard and brittle resin groups having a higher Tg, there cannot be attained any sufficient chemical bonding therebetween merely by the treatment using commercially available coupling agents, such chemical bonding being inferior to that of conventional FR-4. Another method for treating the copper foil with a silane coupling agent has a problem that residue remaining on the substrate after circuitry formation cause contamination in the subsequent plating process and adversary affect the adhesion with solder resists.
SUMMARY OF THE INVENTION
The present invention has been contemplated to solve these problems associated with the prior art and provide for an epoxy resin composition and a printed circuit board using the same, which features a low hygroscopic property, an excellent heat endurance and a good adhesion with copper foils.
Namely, the epoxy resin composition and the printed circuit board using the same are made of an epoxy resin composition which comprises essentially (a) an epoxy resin, (b) a multi-functional phenol group, (c) a hardening accelerator, and (d) a compound with a triazine or isocyanuric ring, or a compound which contains nitrogen 60 weight percent or less without containing a urea derivative.
Further, in the epoxy resin composition for use in the printed circuit board according to the invention, preferably, its phenol hydroxyl group in the multi-functional phenol of (b) is in a range of 0.5 to 1.5 equivalent weight relative to the epoxy group of the epoxy resin; the hardening accelerator of (c) is in a range of 0.01 to 5 weight part relative to a hundred weight part of the epoxy resin; and the compound of (d) with a triazine or isocyanuric ring, or the compound which contains nitrogen of 60 weight percent or less without containing urea derivative is contains nitrogen in a range of 0.1 to 10 weight percent relative to a solid resin part. Further, more preferably, in addition to the above (a) to (d), the epoxy resin composition of the invention contains (e) a flame-retardant agent, which is preferably a tetrabromobisphenol A or a glycidyl ether of tetrabromobisphenol A.
Still further, the epoxy resin composition for use in the printed circuit board according to the invention described above is provided as a varnish, which is impregnated into a base material, dried to provide for a prepreg, on one or both surfaces of the prepreg, a plurality of which may be laminated, a metal foil is deposited, then they are heated under pressure to form the printed circuit board.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the invention will be described in detail in the following.
The epoxy resin of (a) described above is selected from the group which includes: a bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenol type epoxy resin, phenol novolac type epoxy resin, crezol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin; phenol salicylate aldehyde novolac type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ether type epoxy resin, and other compounds such as a bi-functional phenol group glycidyl ether compound, bi-functional alcohol glycidyl ether compound, polyphenol group glycidyl ether compound, polyphenol glycidyl ether compound and its hydride or halogenate. However, it is not limited to the above, and may be used in combination of these compounds.
The multifunctional phenol group of (b) described above is selected from the group which includes: a bisphenol F, bisphenol A, bisphenol S, polyvinyl phenol, and a novolac resin or its halogenate which is obtained by addition condensation of a phenol group such as phenol, crezol, alkylphenol, catechol, bisphenol F, bisphenol A and bisphenol S with an aldehyde group. A molecular weight of any of these compounds is not limited particularly, and it may be used in combination. A quantity of addition of its phenol hydroxyl group is preferably in a range of 0.5 to 1.5 equivalent weight relative to the epoxy group of the epoxy resin. If outside this range, a problem arises that its dielectric property and heat endurance may be deteriorated.
The hardening accelerator described above (c) may be any compound if it has a function to accelerate ether chemical reaction of the epoxy group with phenol hydrate group, which includes, for example, an alkaline metal compound, alkaline earth metal compound, imidazole compound, organic phosphorus compound, secondary amine, tertiary amine, tetra ammonium salt and the like. When an imidazole compound is used wherein its imino group is masked with acrylonitrile, isocyanate, melamine acrylate or the like, advantageously, a prepreg that has an excellent pot life stability twice or more better than that of the conventional prepreg can be provided.
The imidazole compound used here includes: imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecyl imidazole, 4,5-diphenylimidazole, 2-methylimidazolin
Arata Michitoshi
Fukuda Tomio
Takano Nozomu
Tomioka Kenichi
Crowell & Moring LLP
Hitachi Chemical Company Ltd.
Tucker Philip
LandOfFree
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