JPH11289166A - Multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board which is superior in fire-resistance and anti-tracking characteristics. SOLUTION: A layer of matrix comprising (a) epoxy resin, (b) a thermosetting resin component, wherein polycondensation product between bisphenol A and formaldehyde are the essential components with a bromine content of 5-15 wt.%, and (c) a hardened product of a thermosetting resin composition, wherein aluminum hydroxide is the essential component with Na2 O content which is 0.2 wt.% or less, is an insulating layer contacting an external layer conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a multilayer printed wiring board.

[0002]

2. Description of the Related Art A multilayer printed wiring board is a printed wiring board having a conductor circuit also in an inner layer. A printed wiring board on which a conductor circuit is formed is used as an inner layer material, and the inner layer material becomes an outer layer conductor. It is manufactured by heating and pressing copper foil through a prepreg. That is, the insulating layer in contact with the outer layer conductor is a layer having a cured product of the thermosetting resin composition contained in the prepreg as a matrix.

In order to ensure the safety of electronic devices to be incorporated, a multilayer printed wiring board is required to have flame retardancy. The flame retardancy and tracking resistance of the multilayer printed wiring board mainly involve the insulating layer in contact with the outer conductor,
Conventionally, a bromine-containing thermosetting resin has been incorporated into a thermosetting resin composition contained in a prepreg in order to impart flame retardancy to an insulating layer in contact with the outer conductor.

[0004]

However, since the bromine-containing thermosetting resin remains after being carbonized and easily forms a conductive path, if the bromine content in the insulating layer in contact with the outer conductor is increased, the bromine-containing thermosetting resin is resistant. There is a problem in tracking property, and it has been required to reduce the bromine content from the viewpoint of tracking resistance. However, when the bromine content is reduced, a predetermined flame retardancy cannot be obtained, and a multilayer printed wiring board excellent in both flame retardancy and tracking resistance has been demanded. SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer printed wiring board having both excellent flame retardancy and tracking resistance.

[0005]

The present invention relates to a thermosetting resin comprising (a) an epoxy resin and (b) a polycondensate of bisphenol A and formaldehyde as essential components and having a bromine content of 5 to 15% by weight. A multilayer printed wiring board comprising a layer having a matrix of a cured product of a thermosetting resin composition containing aluminum hydroxide as an essential component and (c) aluminum hydroxide as an insulating layer in contact with an outer conductor.

[0006] Tracking is a phenomenon in which a thermosetting resin in an insulating layer is carbonized by a minute arc discharge or the like generated from a conductor of a circuit, and a conductive path is formed between circuits by the carbonized resin. It is known that this is easily caused when moisture or conductive particles adhere to the surface, and that tracking becomes more likely to occur when the bromine content of the thermosetting resin in the insulating layer increases. According to the present invention, both the flame retardancy and the tracking resistance are satisfied by suppressing the bromine content of the thermosetting resin component and adding aluminum hydroxide.

The bromine content of the thermosetting resin component is 5% by weight.
If it is less than 1, the desired flame retardancy cannot be obtained, and if the bromine content exceeds 15% by weight, the tracking resistance deteriorates. From this, the bromine content of the thermosetting resin component is set to 7 to 12
More preferably, it is set to be% by weight.

Next, the present inventor has found that Na ₂ O contained in aluminum hydroxide is involved in the generation of tracking, and has reached the invention described in claim 2. Claim 2
The invention according to claim 1 is the multilayer printed wiring board according to claim 1, wherein the Na ₂ O content of the aluminum hydroxide is 0.2% by weight or less.

[0009] Na ₂ O is considered to act as a catalyst when carbonizing the resin, and it is considered that the carbonization of the resin is suppressed by reducing the Na ₂ O content. Further, Na ₂ O is also involved in the thermal decomposition of aluminum hydroxide, and by reducing the content of Na ₂ O, a decrease in the thermal decomposition temperature of aluminum hydroxide is prevented, and the heat resistance of the multilayer printed wiring board is reduced. It is also possible to suppress a decrease in sex.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the epoxy resin (a),
An epoxy resin having two or more epoxy groups in a molecule can be used. For example, bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol epoxy resin such as bisphenol S epoxy resin, phenol novolak epoxy resin, phenol novolak epoxy resin such as cresol novolak epoxy resin, alicyclic epoxy Resins, glycidylamine type epoxy resins and the like can be mentioned, and these may be used alone or in combination of two or more.

The polycondensate of bisphenol A and formaldehyde in (b) is a component that serves as a curing agent for the epoxy resin. Bisphenol A and formaldehyde can be used by polycondensation according to known methods and conditions, and there is no particular limitation. In addition, a phenol resin such as a phenol novolak resin can be used in combination as long as the effects of the present invention are not impaired.

The epoxy resin of (a) and the polycondensate of bisphenol A and formaldehyde of (b) are represented by (b)
Hydroxyl equivalent of (a) / epoxy equivalent of (a) = 0.8 to 1.2
It is preferable to mix them such that Since the polycondensate of bisphenol A and formaldehyde of (b) acts as a curing agent for the epoxy resin of (a), the polycondensate of the insulating layer may be less than 0.8 or more than 1.2. Heat resistance tends to decrease. For this reason, it is more preferable to mix (b) hydroxyl equivalent / (a) epoxy equivalent = 0.9 to 1.1.

As a bromine source of the thermosetting resin component, it is preferable to incorporate a bromide as the epoxy resin, since heat resistance is not impaired. In addition, a flame retardant such as a bromine-containing compound such as tetrabromobisphenol A or a phosphorus compound such as tetraphenylphosphine may be blended.

The aluminum hydroxide (c) is used in an amount of 70 to 70 parts by weight based on a total of 100 parts by weight of the epoxy resin (a) and the polycondensate of bisphenol A and formaldehyde (b).
It is preferable to mix 180 parts by weight. If the amount is less than 70 parts by weight, the tracking resistance tends to decrease. If the amount exceeds 180 parts by weight, it becomes difficult to impregnate the fiber base material in the prepreg manufacturing process. And the heat resistance of the multilayer printed wiring board tends to decrease. Aluminum hydroxide has a particle size of 0.5 to 5μ.
It is preferable to use m. When the particle size is less than 0.5 μm, the viscosity increases significantly when varnish is formed, and when a prepreg is produced, the impregnating property to the fiber base material tends to decrease. On the other hand, when the particle size exceeds 5 μm, the fluidity tends to decrease during the heating and press-molding, and it becomes difficult to fill irregularities between the circuits of the inner layer material, which tends to cause voids. Aluminum hydroxide has a Na ₂ O content of 0.2% by weight.
The following commercially available products can be selected and used.

In order to promote the reaction of the polycondensate of the epoxy resin (a) with the bisphenol A and formaldehyde (b), it is preferable to add a curing accelerator. Examples of the curing accelerator include imidazole, amines, and boron trifluoride complex compound. As imidazole, 2
-Methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2- Ethyl imidazole, 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-isopropylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-ethyl-4-methyl Imidazole trimellitate, 1-cyanoethyl-2-undecylimidazole trimellitate,
1-cyanoethyl-2-phenylimidazole trimellitate, 1-cyanoethyl-2-phenyl-4,5-di (cyanoethoxymethyl) imidazole and the like can be mentioned. As amines, dimethylaminomethylphenol, 2,4,6-tri (dimethylaminomethyl)
Examples include phenol and tri-2-ethylhexane salt of tri (dimethylaminomethyl) phenol. Also,
As the boron trifluoride complex compound, boron trifluoride / monoethylamine complex compound, boron fluoride / triethylamine complex compound, boron fluoride / piperidine complex compound, boron trifluoride / n-butyl ether Complex compound, 3
Boron fluoride / amine complex compounds. The curing accelerator is preferably added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the epoxy resin (a) and the polycondensate of bisphenol A and formaldehyde (b) in total. If the amount is less than 0.1 part by weight, the effect of accelerating the curing tends to decrease, and if it exceeds 10 parts by weight, the storage stability of the prepreg tends to deteriorate. From this, 0.1
It is more preferable to add 5 to 5 parts by weight. The thermosetting resin composition used in the present invention may contain other components such as an ultraviolet absorber and a colorant, if necessary, in addition to the curing accelerator.

The thermosetting resin composition used in the present invention comprises:
The varnish is dissolved and dispersed in a solvent to obtain a varnish, and the varnish is impregnated into a fiber base and dried to produce a prepreg. The solvent used here is not particularly limited, and includes, for example, acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, N, N-dimethylformamide,
Examples thereof include N, N-dimethylacetamide, methanol, and ethanol. These may be used alone or in combination of two or more. As the fiber base material, a glass woven fabric generally used in the field of a laminated board can be used, but is not limited thereto. From the viewpoint of tracking resistance, it is preferable to use an open-woven glass woven fabric. Opening treatment is a treatment to loosen the yarn of the glass woven fabric by spraying high-pressure water or squeezing with a roll. This treatment improves the impregnation of the varnish near the weave of the glass woven fabric, thereby improving the resistance to varnish. Tracking performance can be improved.

The prepreg thus produced is disposed between the inner layer material and the outer layer conductor, and heated and pressed to produce a multilayer printed wiring board. As the outer layer conductor, copper foil commonly used in printed wiring boards can be used, and there is no particular limitation. The same applies to the inner layer material. Generally, two prepregs are arranged between the inner layer material and the outer layer conductor. Since tracking occurs in the insulating layer in contact with the outer conductor,
When two prepregs are arranged, the prepreg manufactured as described above may be arranged on the side in contact with the outer layer conductor, and the other prepreg may be a known prepreg. The manufacturing method and conditions of the multilayer printed wiring board can be based on known manufacturing methods and conditions, and are not particularly limited.

[0018]

Example 1 60 parts by weight of a brominated bisphenol A type epoxy resin (epoxy equivalent: 480, bromine content: 21.5% by weight, manufactured by Toto Kasei Co., Ltd., using YDB-500 (trade name)), bisphenol A Type epoxy resin (epoxy equivalent 450,
YD-011 (trade name) manufactured by Toto Kasei Co., Ltd.)
40 parts by weight, polycondensate of bisphenol A and formaldehyde (hydroxyl equivalent 118, manufactured by Dainippon Ink and Chemicals, Plyofen UH-4170 (trade name)
24.5 parts by weight, 0.2 parts by weight of 2-ethyl-4-methylimidazole and aluminum hydroxide (Na ₂
150 parts by weight of an O content of 0.03% by weight and a particle size of 2 to 4 μm) were dissolved and dispersed in methyl ethyl ketone to prepare a varnish having a nonvolatile content of 75% by weight. A prepreg was impregnated and dried on an open-woven glass cloth (thickness: 0.1 mm, basis weight: 105 g / m ² , manufactured by Nitto Boseki Co., Ltd.) so that the amount of adhering components was 52% by weight. Produced. The thickness of 18 mm is applied to both sides of the inner layer material obtained by performing circuit processing on a 0.4 mm thick glass cloth base epoxy resin double-sided copper-clad laminate.
A copper foil of μm was stacked on each of the two prepregs obtained above, and heated and pressed at a pressure of 4 MPa and a temperature of 170 ° C. for 90 minutes to produce a four-layer printed wiring board.

Example 2 Unwoven Weave Treatment A glass cloth (thickness 0.1 m) without weaving the glass cloth
m, basis weight 105g / m ^TwoExample 1 except for changing to
In the same manner as in the above, a four-layer printed wiring board was produced.

Comparative Example 1 The compounding amount of the brominated bisphenol A type epoxy resin was 23
The amount of bisphenol A type epoxy resin was changed to 76 parts by weight, the amount of polycondensate of bisphenol A and formaldehyde was changed to 25.6 parts by weight, and ethylene glycol monomethyl ether was used as a solvent. Example 1 except that a mixed solvent of ethylene glycol and methyl ethyl ketone (weight ratio of ethylene glycol monomethyl ether / methyl ethyl ketone = 25 / 66.5) was used.
In the same manner as in the above, a four-layer printed wiring board was produced.

Comparative Example 2 The compounding amount of the brominated bisphenol A type epoxy resin was 92
4 layers in the same manner as in Comparative Example 1 except that the compounding amount of the bisphenol A type epoxy resin was changed to 7 parts by weight, and the compounding amount of the polycondensate of bisphenol A and formaldehyde was changed to 25 parts by weight. A printed wiring board was manufactured.

Comparative Example 3 The amount of the brominated bisphenol A type epoxy resin was 58
Parts by weight, the amount of bisphenol A type epoxy resin was changed to 64 parts by weight, and dicyandiamide 3 was replaced with polycondensate of bisphenol A and formaldehyde.
A four-layer printed wiring board was prepared in the same manner as in Comparative Example 1 except that the parts by weight were blended.

Comparative Example 4 The amount of the brominated bisphenol A type epoxy resin was 85
Parts by weight, and 15 parts by weight of a cresol novolak type epoxy resin (epoxy equivalent: 210, manufactured by Toto Kasei Co., Ltd., using YDCN-703 (trade name)) in place of the bisphenol A type epoxy resin. A four-layer printed wiring board was produced in the same manner as in Comparative Example 3, except that no was blended.

The tracking resistance, flame retardancy and solder heat resistance of the manufactured four-layer printed wiring board were examined as follows. Table 1 shows the results. Table 1 also shows the bromine content of the thermosetting resin component used. Tracking resistance: Using a platinum electrode, a CTI value was determined from a tracking voltage curve according to the IEC method. Flame retardancy: Investigated according to the UL combustion test method. Solder heat resistance: 3 pieces of 50 mm x 50 mm samples each with copper foil on the surface removed by etching in boiling water
After immersion for 4 hours, the sample was immersed in a solder at 260 ° C. for 20 seconds, and the result of visual observation of each sample for the presence or absence of abnormality was shown. In Table 1, .largecircle. Indicates no abnormality and X indicates significant blistering.

[0025]

[Table 1] Note) Br: Bromine content Tiger resistance: Tracking resistance Soldering heat resistance D-1 / 100: Immersion in boiling water for 1 hour D-2 / 100: Immersion in boiling water for 2 hours D-3 / 100: 3 in boiling water Dip for 4 hours D-4 / 100: Dip for 4 hours in boiling water

From Table 1, it can be seen that those having a lower bromine content (Comparative Example 1) did not satisfy the flame retardancy, and those having a higher bromine content (Comparative Example 2) did not satisfy the tracking resistance, and bisphenol Those using dicyandiamide instead of the polycondensate of A and formaldehyde (Comparative Examples 3 and 4) do not satisfy the tracking resistance.

[0027]

The multilayer printed wiring board according to the present invention has both good flame retardancy and good tracking resistance, and can secure the safety of electronic equipment to be incorporated.

Claims (2)

[Claims] 1. A thermosetting resin component comprising (a) an epoxy resin and (b) a polycondensate of bisphenol A and formaldehyde as essential components and having a bromine content of 5 to 15% by weight; and (c) aluminum hydroxide. A multilayer printed wiring board comprising a layer having a matrix of a cured product of a thermosetting resin composition containing, as an essential component, an insulating layer in contact with an outer conductor. 2. The multilayer printed wiring board according to claim 1, wherein the Na ₂ O content of the aluminum hydroxide is 0.2% by weight or less.