Patent Application
20140154939
The present invention relates to a resin composition, especially a halogen-free low-dielectric resin composition, and prepreg used in printed circuit boards and copper foil laminate made by using same
As for the high-speed and high-frequency signal transmission in printed circuit boards, the smaller the signal attenuation is, the more advantageous it is to obtain a more complete signal. Recently, the demand for low dielectric copper clad plate is further increased along with the rapid development of information industry, and the sheet materials are required to have lower dielectric constant and less dielectric loss. The common FR-4 has a dielectric constant (Dk) of 4.3-4.8 at the condition of 1 GHz and a dielectric loss (Df) of 0.02-0.025, and has a dielectric constant (Dk) of 4.5-5.0 at the condition of 1 MHz and a dielectric loss (Df) of 0.015-0.02. Thus the common FR-4 cannot meet the requirements on the transmission rate of high frequency signal and the integrity of signal transmission.
There are various methods for preparing dielectric copper clad plates, such as cyanate-type, polyphenylene oxide-type, tetrafluoroethylene-type, bismaleimide-type copper clad plates, but they have the problems such as high price, complex process. There are fewer patents for preparing copper clad plate by using the low polarity and flexibility of polybutadiene. It is reported in Chinese Patent No.200710162020.9 that the resin plate prepared form 1,2-polybutadiene under the step-by-step free radical polymerization of low-temperature and high-temperature initiators has a Dk of 2.5 and a Df of 0.0015; the laminate has a Dk of 3.2 and a Df of 0.0024. However, it will be observed that polybutadiene exudes from the laminate. Moreover, it has a lower glass transition temperature and heat resistance, a worse adhesiveness to copper foil and a general solvent resistance.
The object of the present invention lies in providing a halogen-free low-dielectric resin composition, wherein the epoxidized polybutadiene not only improves the shortcomings of polybutadiene, but also maintains the advantages in dielectric property and flexibility, so as to make the composition have excellent dielectric performance.
Another object of the present invention lies in providing a prepreg and copper foil laminate made by using the halogen-free low-dielectric resin composition, which have excellent dielectric performance, better heat resistance and high glass transition temperature and can meet the requirements on the high frequency of electric signal transmission and high speed information processing in printed circuit copper clad plate industry.
In order to achieve said objects, the present invention provides a halogen-free low-dielectric resin composition, comprising based on the weight of the organic solid,
Said polybutadiene epoxy resin comprises at least one of the compounds having the following structural formula (I)
wherein the formula (I) represents cis-1,4-epoxidized polybutadiene, trans-1,4-epoxidized polybutadiene, cis-1,4-epoxidized hydroxyl terminated polybutadiene, trans-1,4-epoxidized hydroxyl terminated polybutadiene, cis-1,4-epoxidized carboxyl terminated polybutadiene, trans-1,4-epoxidized carboxyl terminated polybutadiene, having a molecular weight of from 100 to 10000;
and the formula (II)
wherein the formula (2) represents 1,2-epoxidized polybutadiene, 1,2-epoxidized hydroxyl terminated polybutadiene, or 1,2-epoxidized carboxyl terminated polybutadiene, having a molecular weight of from 100 to 10000.
Said benzoxazine resin comprises one or more selected from the group consisting of allyl benzoxazine, bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, 4,4′-diaminodiphenylmethane-type benzoxazine, biscyclopentadiene-type benzoxazine.
The epoxy resin comprises at least one of the following compounds
The curing agent is one or more selected from the group consisting of phenol curing agents, amine curing agents, acid or anhydride curing agent and cyanates.
The organic fire retardant is selected from the group consisting of melamine, melamine cyanurate, phosphate and compounds thereof, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and compounds thereof, phenoxyl phosphonitrile, or mixtures thereof.
The curing accelerator is one or more selected from the group consisting of 2-methylimidazole, 1-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-hendecylimidazole, and 2-phenyl-4-methylimidazole.
The packing is one or more inorganic packings selected from the group consisting of aluminium hydroxide, magnesium hydroxide, zeolite, wollastonite, silicon dioxide, magnesia, calcium silicate, calcium carbonate, clay, talc and mica.
The initiator is a peroxide having the following structural formula
wherein R1 and R2 are H, alicyclic hydrocarbon with 3 to 20 carbon atoms and derivatives thereof, aliphatic hydrocarbon with 1 to 20 carbon atoms and derivatives thereof, or unsaturated aliphatic hydrocarbon with 2 to 20 carbon atoms and derivatives thereof.
The halogen-free low-dielectric resin composition has a halogen content of less than 0.09 wt. %.
Meanwhile, the present invention provides a prepreg fabricated by using the halogen-free low-dielectric resin composition, comprising a base material and a halogen-free low-dielectric resin composition attached thereon after impregnation and drying. The base material is a nonwoven fabric or other fabrics.
Further, the present invention provides a copper foil laminate made by using the halogen-free low-dielectric resin composition, comprising several laminated prepregs, copper foils covered on one or both sides of the laminated prepregs, wherein each of the prepregs comprises a base material and a halogen-free low-dielectric resin composition attached thereon after impregnation and drying.
The present invention has the following beneficial effects. The halogen-free low-dielectric resin composition of the present application uses the epoxidized polybutadiene, which not only improves the shortcomings of polybutadiene, but also maintains the advantages in dielectric property and flexibility, and increases the adhesiveness to copper foils. High heat resistant benzoxazine is added to the formulation so as to cover the shortages of polybutadiene epoxy resin in heat resistance and flame retardance. The residual double bonds may be copolymerized with other resins containing double bonds under the action of the initiator, to increase the crosslinking density and solves the problem of the phase separation which readily occurs in polybutadiene resin. The prepreg and copper foil laminate for printed circuit made by using such resin composition have excellent dielectric performance, better heat resistance and high glass transition temperature and can meet the requirements on the high frequency of electric signal transmission and high speed information processing in printed circuit copper clad plate industry.
The halogen-free low-dielectric resin composition of the present invention comprises, based on the weight of the organic solid,
Said polybutadiene epoxy resin comprises at least one of the compounds having the following structural formula (I)
wherein the formula (I) represents cis-1,4-epoxidized polybutadiene, trans-1,4-epoxidized polybutadiene, cis-1,4-epoxidized hydroxyl terminated polybutadiene, trans-1,4-epoxidized hydroxyl terminated polybutadiene, cis-1,4-epoxidized carboxyl terminated polybutadiene, trans-1,4-epoxidized carboxyl terminated polybutadiene, having a molecular weight of from 100 to 10000; and the formula (II)
wherein the formula (2) represents 1,2-epoxidized polybutadiene, 1,2-epoxidized hydroxyl terminated polybutadiene, or 1,2-epoxidized carboxyl terminated polybutadiene, having a molecular weight of from 100 to 10000.
Said polybutadiene epoxy may be used alone, or the mixtures of these compounds may be used in an amount of from 5 to 90 parts by weight, preferably from 10 to 50 parts by weight. The liquid epoxidized polybutadiene resin has a molecular weight of from 100 to 10000, preferably less than 5000, and an epoxy equivalent of from 200 to 600 g/mol.
Said benzoxazine resin in the present invention, i.e. the compound having benzoxazine ring, is advantageous to increasing the flame retardance, moisture resistance, heat resistance, mechanical performance and electricity performance of the cured resin and the base plate made therefrom. The selected benzoxazine a prepolymer formed from one or more selected from the group consisting of allyl benzoxazine, bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, MDA (4,4′-diaminodiphenylmethane)-type benzoxazine, biscyclopentadiene-type benzoxazine. Benzoxazine having the unsaturated bond structure has a lower dielectric constant, and the double bond thereof and the residual double bond on epoxidized polybutadiene may be free-radical polymerized under the action of the initiator, to avoid the problem that the epoxidized polybutadiene produce the phase separation structure in the product. Thus the present invention preferably uses allyl benzoxazine, and the amount thereof is better from 10 to 90 parts by weight, preferably from 20 to 50 parts by weight.
The epoxy resin of the present invention is preferably the diglycidyl ether epoxy resin and provides the basic mechanical and thermal performance as required by the base plate. The epoxy resin comprises at least one of the following compounds
The curing agent is one or more selected from the group consisting of phenol curing agents, amine curing agents, acid or anhydride curing agent and cyanates.
The organic fire retardant is selected from the group consisting of melamine, melamine cyanurate (MCA), phosphate and compounds thereof, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and compounds thereof, phenoxyl phosphonitrile, or mixtures thereof. As for such flame retardant, it is better not to reduce the dielectric constant, and it can be used alone or in combinations according to the synergistic flame retardant effect.
The curing accelerator is one or more selected from the group consisting of 2-methylimidazole, 1-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-hendecylimidazole, and 2-phenyl-4-methylimidazole.
The packing is one or more inorganic packings selected from the group consisting of aluminium hydroxide, magnesium hydroxide, zeolite, wollastonite, silicon dioxide, magnesia, calcium silicate, calcium carbonate, clay, talc and mica, wherein the optimal packing is silicon dioxide. The packing has a particle size median value of from 1 to 15 μm, preferably from 2 to 5 μm. The amount of the inorganic packing may be adjusted according to the application object, and is preferably from 10 to 90 wt. % relative to the total amount of the organic solids.
The initiator is a peroxide having the following structural formula
wherein R1 and R2 are H, alicyclic hydrocarbon with 3 to 20 carbon atoms and derivatives thereof, aliphatic hydrocarbon with 1 to 20 carbon atoms and derivatives thereof, or unsaturated aliphatic hydrocarbon with 2 to 20 carbon atoms and derivatives thereof. The initiator is better in an amount of form 0.1 to 10 parts by weight, preferably from 0.5 to 5 parts by weight.
The halogen-free low-dielectric resin composition has a phosphorus content of from 1 to 5 wt. %, a nitrogen content of from 1 to 5 wt. % and a halogen content of less than 0.09 wt. %.
The present invention further provides a prepreg fabricated by using the halogen-free low-dielectric resin composition, comprising a base material and a halogen-free low-dielectric resin composition attached thereon after impregnation and drying. The base material is a nonwoven fabric or other fabrics, e.g. natural fibers, organic synthetic fibers and inorganic fibers. The composition of the present invention is prepared by the conventional method, comprising firstly adding the solids, then adding the solvent which is one or more selected from the group consisting of acetone, butanone, cyclohexanone, ethylene glycol methyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, stirring to complete dissolution, adding a liquid resin, continuously and homogeneously stirring. Said composition is added into a vessel; the accelerator, curing agent and initiator are firstly dissolved in a certain butanone solvent; the solid content of the solution is suitably adjusted with butanone solvent to 65-75% so produce a liquid cement; the liquid cement is impregnated with fabrics or organic fabrics such as glass fiber cloth; the impregnated glass fiber cloth is baked in an oven at 155° C. for 5-10 min to produce a prepreg.
The copper foil laminate made by using the halogen-free low-dielectric resin composition comprises several laminated prepregs, wherein each of the prepregs comprises a base material and a halogen-free low-dielectric resin composition attached thereon after impregnation and drying.
The printed circuit board of the present invention is made by coving copper foil (having a thickness of 35 μm) on one or two sides of the laminate made by bonding two or more prepregs via heating and compressing. Said copper foil lamination shall meet the following requirements: (1) the heating rate of the lamination shall generally be controlled within 1.0 to 3.0° C./min at the feedstock temperature of 80-160° C.; (2) setting of lamination pressure: a full pressure of about 300 psi is applied when the outside feedstock is at a temperature of 80-100° C.; (3) while curing, the feedstock is controlled at a temperature of 200° C. and remains for 90 min. Besides copper foil, the metal foil for covering may also be nickel foil, aluminum foil, SUS foil and the like, and the material is not limited.
As for the aforesaid copper foil laminate (8 sheets of the bonding sheets) for use in the printed circuit board, the performances thereof, such as dielectric loss factor, heat resistance, hygroscopicity, glass transition temperature, flame retardance and the like, are measured, and further detailed explained and described in the following examples.
The present invention is detailedly explained by the following examples, but is not limited within the scope of the examples. If not specifically indicated, said part represents the part by weight, and said % represent wt. %.
The aforesaid properties are measured by the following methods.
In conclusion, it can be seen that the efficacies of low dielectric property, heat resistance, dip-soldering resistance, and hygroscopicity can be achieved according to the present invention. Meanwhile, the plate material has an excellent processability, and the halogen content can achieve the V-O standard in fire resistance test UL94 within the JPCA halogen-free standard scope. The present invention sufficiently utilizes the synergistic properties of epoxidized polybutadiene, benzoxazine, epoxy resin, initiator, and curing agent, and the halogen content is less than 0.09%, so as to achieve the efficacy of environmental protection. Additionally, the printed circuit board prepared by using the resin matrix of the present invention has the equivalent mechanical performance and heat resistance to the general FR-4 printed circuit board.
Those stated above are the preferred examples of the present invention. Those ordinarily skilled in the art can make various corresponding changes and deformations according to the technical solutions and concepts of the present invention, but all said changes and deformations shall belong to the protection scope of the present invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2011/080943 | 10/18/2011 | WO | 00 | 1/29/2014 |
