JP2003198141A - Insulating material for multilayer printed wiring board, insulating material clad with metal foil, and multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost adhesive film clad with a copper foil which enables processing of holes into a good shape by carbon dioxide gas laser processing and has a superior connection reliability, while at the same time satisfying various conventional characteristics such as an adhesiveness and a heat-resistant property, by increasing the toughness of a resin due to the increase in an aromatic component, a cross-linkage density, and the interlocking strength among high molecules by adding a cresol novolak type epoxy resin having a melting viscosity of 6.5P (150°C) or above with respect to a mixture of a carboxylic acid denatured polyvinyl acetal resin, a melamine resin, and a thermosetting resin. <P>SOLUTION: An insulating material for a multilayer printed wiring board is formed of a carboxylic acid denatured polyvinyl acetal resin, a melamine resin as a cross-linkage agent for a polyvinyl acetal resin, a thermosetting resin, and a cresol novolak type epoxy resin, as essential components. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an insulating material for a multilayer printed wiring board, an insulating material with a metal foil using the same, and a multilayer printed wiring board using the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have become smaller and lighter, have higher performance, and have lower costs, and the density of wiring on printed wiring boards used has been increased, the thickness of boards has been reduced, and the reliability of connections has been improved. ,
Manufacturing cost reduction is required. When a multilayer printed wiring board is manufactured using an adhesive film that is a prepreg without glass cloth or an adhesive film with a copper foil, it is possible to achieve high density, lightness, thinness and shortness. Furthermore, since it does not have glass cloth, it excels in small-diameter drilling workability and laser hole workability. In particular, in the manufacture of a multilayer printed wiring board, fine connection through holes and interstitial via holes (IVH) for electrical connection between layers are used.
Therefore, good drilling workability and laser hole workability are essential conditions for achieving high reliability. Conventionally, an epoxy resin adhesive film or a polyimide film has been used, but since the cost is high, an adhesive film or an adhesive film with a copper foil that is inexpensive and has excellent small-diameter drilling workability and laser hole workability is required.
Heretofore, a method of using a mixture of a carboxylic acid-modified polyvinyl acetal resin and a melamine resin as a cross-linking agent and a thermosetting resin as a low-cost film-like insulating material has been known. However, the cross-section of the hole shape during carbon dioxide laser processing becomes an overhang shape (a phenomenon in which the resin immediately below the mask edge is scooped out during laser processing by the conformal mask method), causing problems with plating. However, there is a problem in that the connection reliability is poor.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has a melt viscosity of 6.5 P (150 P) for a mixture of a carboxylic acid-modified polyvinyl acetal resin, a melamine resin, and a thermosetting resin. ℃) above by adding a cresol novolac type epoxy resin,
By strengthening the resin by increasing the aromatic content and increasing the crosslink density and the entanglement of polymer chains, while satisfying the various characteristics such as adhesiveness and heat resistance from the conventional one, An object of the present invention is to provide an inexpensive adhesive film with a copper foil having a good hole shape and excellent connection reliability.

[0004]

Means for Solving the Problems That is, the present invention provides a carboxylic acid-modified polyvinyl acetal resin, a melamine resin as a cross-linking agent for a polyvinyl acetal resin, a thermosetting resin, and a cresol having a melt viscosity of 6.5 P (150 ° C.) or more. This is achieved by using a novolac epoxy resin as an essential component. Hereinafter, the present invention will be described in detail.

(Polyvinyl acetal resin) In the present invention, it is particularly preferable to use a carboxylic acid-modified polyvinyl acetal resin as the polyvinyl acetal resin. In the present invention, the degree of polymerization of the carboxylic acid-modified polyvinyl acetal resin and the degree of acetalization are not particularly limited, but those having an average degree of polymerization of 500 to 3000 and an acetalization degree of 60 to 100 mol% are preferable. . If the average degree of polymerization is less than 500, the heat resistance of the adhesive is not sufficient, and if it exceeds 3000, the viscosity of the adhesive becomes too high and it becomes difficult to apply it to the metal foil. The degree of acetalization is not particularly limited as long as it is within the above range, but if it is less than 60 mol%, the flexibility of the resin is insufficient and the adhesive strength is poor. The carboxylic acid-modified polyvinyl acetal resin is used in an amount of 5 to 50% by weight based on the entire resin component (including a curing agent and a curing accelerator) of the insulating material for a multilayer printed wiring board according to the present invention.
It is particularly preferable in terms of uniform thickness and heat resistance. If the carboxylic acid-modified polyvinyl acetal resin is too small, it becomes difficult to obtain an insulating layer having a uniform thickness, and if it is too large, heat resistance and the like tend to be deteriorated. In addition, a polyvinyl acetal resin such as polyvinyl butyral which is not modified with an unsaturated carboxylic acid having two or more carboxyl groups can be mixed and used together. Examples of commercially available carboxylic acid-modified polyvinyl acetal resins include S-REC KS-23 and HS-1 (both manufactured by Sekisui Chemical Co., Ltd.). In addition, S-REC KS-
3Z, KS-5, KS-5Z (all manufactured by Sekisui Chemical Co., Ltd., trade name) and the like. In addition, polyvinyl butyral resin which is not modified with an unsaturated carboxylic acid having two or more carboxyl groups can be mixed and used together. These resins may be used alone or in combination of two or more.

(Bridge material of polyvinyl acetal resin)
A cross-linking agent of polyvinyl acetal resin can be mixed with the insulating material. Particularly when the polyvinyl acetal resin is not acid-modified, the crosslinking agent is an essential component. As the cross-linking material for the polyvinyl acetal resin, a resol type phenol resin, a phenol resin, a melamine resin, a poly- (or di-) isocyanate compound, glyoxazole or a derivative thereof can be used, and a methylolated melamine resin and an alcohol can be used. It is preferred to use an alkoxylated methylolated melamine resin.
The bridging material is preferably used in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the polyvinyl acetal resin. If the amount is less than 1 part by weight, the polyvinyl acetal resin tends to be insufficiently cross-linked and the chemical resistance tends to decrease.
Further, if the amount exceeds 100 parts by weight, the filling property of the inner layer circuit and the heat resistance of the insulating material may be deteriorated at the time of multilayering.

(Cresol novolac type epoxy resin)
Any cresol novolac type epoxy resin having two or more epoxy groups in the molecule and having a melt viscosity of 6.5 P (150 ° C.) or more may be used. Mixtures of these halides, hydrogenates and the resins mentioned above are suitable. The cresol novolac type epoxy resin is 50 to 1 with respect to 100 parts by weight of the polyvinyl acetal resin.
It is preferably used in the range of 50 parts by weight. If it is less than 50 parts by weight, a good via shape cannot be obtained, and if it exceeds 150 parts by weight, the inner layer circuit filling property and heat resistance of the insulating material at the time of multilayering may be deteriorated.

(Thermosetting Resin) As the thermosetting resin,
Any compound may be used as long as it is a compound having two or more epoxy groups in the molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine. Type epoxy resins, hydantoin type epoxy resins, isocyanate type epoxy resins, aliphatic cyclic epoxy resins, hydrogenated compounds, and mixtures of the above resins are preferred, among which bisphenol A
Type epoxy resins are preferable because they are excellent in combustion resistance and heat resistance.

(Curing agent) The curing agent is not particularly limited as long as it is usually used for curing an epoxy resin, and for example, dicyandiamide, bisphenol A, polyvinylphenol, phenol novolac resin, bisphenol A novolac resin and these phenol resins. The halides, hydrides, etc. of can be used.

(Curing Accelerator) As the curing accelerator, when the resin is an epoxy resin, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt or the like can be used. The ratio of the curing accelerator to the resin is preferably 0.01 to 20 parts by weight, more preferably 0.1 to 1.0 parts by weight, based on 100 parts by weight of the resin.

(Diluent) The resin component of the present invention (crosslinking material,
The curing agent and the curing accelerator can be used as a resin varnish by diluting with a solvent. Solvents include acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, methanol, ethanol, N, N '.
-Dimethylformamide, N, N'-dimethylacetamide and the like can be used.

(Other compounding agents) Further, in the present invention, in addition to the above-mentioned respective components, a coupling agent, a filler and the like may be optionally compounded in the resin.

The insulating material thus obtained is applied in the form of a varnish to a metal foil such as a copper foil and dried to be in a semi-cured state, whereby an insulating material with a metal foil can be obtained. The metal foil is preferably one whose surface is roughened in order to increase the adhesive force with the insulating material. Inner layer circuit board, by applying an insulating material, by laminating a metal foil and heating and pressing, also, by laminating the insulating material with a metal foil so that the insulating material faces the inner layer circuit board, by heating and pressing, A multi-layer metal-clad laminate including an inner layer circuit board can be produced.
According to the usual method, by performing an outer layer circuit forming step and an inner layer circuit and outer layer circuit conducting step, a multilayer printed wiring board in which the inner layer circuit formed on the inner layer circuit board and the outer layer circuit are electrically connected is manufactured. can do.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples. The resin composition was used in the ratio shown in Table 1 using the following raw materials. -Bisphenol A type epoxy resin (molecular weight 1250,
Epoxy equivalent 208) -cresol novolac epoxy resin (ESCN-19
0-3: Melt viscosity 2.8P, epoxy equivalent 195, ES
CN-190-6: Melt viscosity 6.5P, epoxy equivalent 1
98, ESCN-190-10: Melt viscosity 10P, Epoxy equivalent 199: Sumitomo Chemical Co., Ltd.-Carboxylic acid-modified polyvinyl acetal resin (ESREC KS-23Z: Sekisui Chemical Co., Ltd.)-Epoxy curing agent (Dicy: Nippon Carbide Industry)・ Imidazole curing accelerator (P-200Z50P: Japan Epoxy Resin)

Example 1 300 parts by weight of bisphenol A type epoxy resin, cresol novolac epoxy resin (ESCN-190-1)
0) 100 parts by weight, dicyandiamide 10 parts by weight, 2-
Methyl ethyl ketone and methanol were added to a composition containing 0.6 parts by weight of ethyl-4-methylimidazole and 100 parts by weight of carboxylic acid-modified polyvinyl acetal to prepare a 65% by weight varnish. This varnish was applied to the roughened surface of a single-sided roughened copper foil having a thickness of 12 μm so that the thickness of the dried insulating material would be 60 μm, and dried to obtain a semi-cured insulating material with copper foil. . Make sure that the insulating material with the copper foil prepared earlier is placed on both sides of the inner layer circuit board that has been subjected to circuit processing on the double-sided copper-clad laminated board with a thickness of 0.2 mm and a copper foil thickness of 35 μm so that the insulating material faces the inner layer circuit board. , 185 ° C., 60 minutes, product pressure 3.
Thermocompression molding was performed under the condition of 0 MPa to produce a multilayer copper-clad laminate with an inner layer circuit. After forming a window hole for laser processing on the outer layer copper foil of the copper-clad laminate by a known method, carbon dioxide gas laser irradiation (ballus width 8 μs, 2 shots) is used to produce IVH.
To form a copper-clad laminate. The following evaluation was performed on the copper-clad laminate prepared above. 1) Tg of a resin cured product was measured by a dynamic viscoelasticity measuring device (DVE). 2) The formed via shape (presence or absence of overhang) was observed by cross-section polishing. 3) After forming a copper circuit having a width of 100 μm and a via hole having a via hole diameter of 150 μm and a land diameter of 350 μm after etching the outer layer copper foil, thermal shock of −65 ° C. (30 minutes) to 125 ° C. (30 minutes) × 300 cycles. The test was conducted and the presence or absence of cracks between the insulating material and the plating was evaluated by observing the cross section.

Example 2 Cresol novolac type epoxy resin (ESCN-19
0-6) Evaluation was carried out in the same manner as in Example 1 except that the molecular weight of 100 parts by weight was changed.

Comparative Example 1 Cresol novolac type epoxy resin (ESCN-19
The evaluation was carried out in the same manner as in Example 1 except that 0-10) was omitted.

Comparative Example 2 Cresol novolac type epoxy resin (ESCN-19
0-3) Evaluation was performed in the same manner as in Example 1 except that 100 parts by weight was changed.

[0019]

[Table 1] Via shape: ○ (no overhang shape), △ (slightly shows overhang shape), × (overhang shape) Thermal shock test: ○ (no interface crack), × (interfacial crack)

As is clear from the above results, Example 1
~ 2 has a high Tg. A copper-clad laminate manufactured using this has excellent connection reliability because of its good via shape, and is useful as an inexpensive and highly reliable insulating material for multilayer printed wiring boards.

[0021]

By the insulating material for a multilayer printed wiring board according to the present invention, an insulating material with a metal foil having a good via shape, excellent connection reliability and low cost, and a multilayer printed wiring using the insulating material with a metal foil are provided. A board can be provided.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 61/06 C08L 61/06 61/28 61/28 63/00 63/00 AF term (reference) 4J002 BE062 CC043 CC184 CD021 CD051 CD101 CD111 CD131 4J036 AA01 AC00 DA01 DA02 FB01 FB08 FB09 JA08 5E346 AA12 AA32 AA42 AA43 CC09 CC31 DD02 DD03 DD12 DD22 DD31 EE01 EE06 EE06 H18H08H11H08H11HFFH

Claims (4)

[Claims] 1. An insulating material for a multilayer printed wiring board, comprising a carboxylic acid-modified polyvinyl acetal resin, a melamine resin as a cross-linking agent for the polyvinyl acetal resin, a thermosetting resin, and a cresol novolac type epoxy resin as essential components. . 2. An insulating material for a multilayer printed wiring board, wherein the cresol novolac type epoxy resin has a melt viscosity of 6.5 P (150 ° C.) or more. 3. An insulating material with a metal foil, which is obtained by laminating the insulating material for a multilayer printed wiring board according to claim 1 on a metal foil in a semi-cured state. 4. The insulating resin layer for supporting the outer layer circuit according to claim 1.
A multilayer printed wiring board, comprising the insulating material for a multilayer printed wiring board according to any one of 1 to 3, wherein an inner layer circuit and an outer layer circuit formed on the inner layer circuit board are electrically connected.