JP4501475B2 - Metal foil with insulating layer and multilayer printed wiring board - Google Patents

Description

  The present invention relates to a metal foil with an insulating layer and a multilayer printed wiring board.

  In the field of semiconductors, with the progress of high-density mounting technology, a trend of moving semiconductor elements from conventional surface mounting to area mounting is progressing. New packages such as a ball grid array (BGA) and a chip scale package (CSP) are appearing and increasing in response to such high-density mounting technology. Therefore, the rigid substrate for interposers has been attracting more attention than ever before, and the demand for a substrate having high heat resistance and low thermal expansion has increased.

  Further, in recent years, with the demand for higher functionality of electronic devices, etc., high density integration and high density mounting of electronic components have been advanced. For this reason, printed wiring boards and the like for high-density mounting used for these are smaller and higher in density than conventional ones. As a measure for increasing the density of such printed wiring boards, build-up multilayer wiring boards are often used.

  A general build-up multilayer wiring board is obtained by laminating an insulating layer having a thickness of 100 μm or less composed of a resin composition and a conductor layer composed of a conductor metal circuit. As an interlayer connection method, various methods such as a laser method and a photo method are used in place of the conventional drilling. These methods achieve high density by freely arranging small-diameter via holes, and various build-up interlayer insulating materials corresponding to each method have been proposed (for example, see Patent Document 1). .)

In the method using the build-up multilayer wiring board, since the interlayer connection is made by fine vias, the connection strength is likely to be lowered, and in some cases, cracks due to the stress generated from the difference in thermal expansion between the insulating resin and the conductor layer when subjected to thermal shock. In order to overcome this problem, it has been studied to reduce the thermal expansion of the insulating layer material. However, when the wiring board is further reduced in thickness, there is a problem that the insulation layer resin cracks due to insufficient strength to withstand the generated stress.
In multilayer printed wiring boards that use resin-coated copper foil as the build-up material, warpage as a multilayer printed wiring board occurs when two or more build-up layers are laminated, or as the core material becomes thinner. However, it has been pointed out that it is difficult to suppress twisting and component mounting defects occur during mounting.

  In order to overcome such problems, for example, a metal with an insulating layer in which an organic base material is impregnated with a thermosetting resin such as an epoxy resin, and an insulating layer in which this is semi-cured is provided on the surface of the metal foil There is a foil (see, for example, Patent Document 2). Such a material can form a thick insulating layer and improve the dimensional stability of the insulating layer, but is not necessarily sufficient in characteristics such as high heat resistance and low thermal expansion, and further improvement of characteristics Was desired.

  Further, these build-up multilayer wiring boards are often required to have flame retardancy. Conventionally, in order to impart flame retardancy, it has been common to use halogen-based flame retardants such as brominated epoxy resins in epoxy resins. However, since dioxins may be generated from halogen-containing compounds, the use of halogen-based flame retardants has been avoided along with the recent serious environmental problems. A computerized system has been demanded.

JP-A-5-243735 Japanese Patent No. 3266825

  The present invention is used for the production of a multilayer printed wiring board, has a high heat resistance, a high rigidity, a low thermal expansion, a metal foil with an insulating layer capable of forming an insulating layer excellent in flame retardancy, and A multilayer printed wiring board using the metal foil with an insulating layer is provided.

Such an object is achieved by the present invention described in the following (1) to (3).
(1) An insulating layer composed of a resin composition containing a curable resin and a non-woven fabric formed of organic fibers is a metal foil with an insulating layer joined to a metal foil, and the resin composition is A metal foil with an insulating layer comprising: a cyanate resin and / or a prepolymer thereof; a bisphenol A-type or F-type mixed epoxy resin substantially free of halogen atoms; and an inorganic filler.
(2) The metal foil with an insulating layer according to (1), wherein the organic fiber contains a polyester fiber.
(3) A multilayer printed wiring board obtained by laminating the metal foil with an insulating layer as described in (1) or (2) above on an inner circuit board and subjecting it to heat and pressure molding.

  According to the present invention, it is possible to provide a metal foil with an insulating layer that can form an insulating layer having high heat resistance, high rigidity, and low thermal expansion and excellent in flame retardancy. And the multilayer printed wiring board of this invention using this metal foil with an insulating layer can respond to high-density mounting.

Hereinafter, the metal foil with an insulating layer and the multilayer printed wiring board of the present invention will be described in detail.
The metal foil with an insulating layer of the present invention is used as a build-up material for multilayer printed wiring boards, and is an insulating layer composed of a resin composition containing a curable resin and a nonwoven fabric formed of organic fibers. Is a metal foil with an insulating layer bonded to a metal foil, the resin composition comprising a cyanate resin and / or a prepolymer thereof, an epoxy resin substantially free of halogen atoms, and an inorganic filler. It is characterized by containing.
A multilayer printed wiring board according to the present invention is characterized in that the metal foil with an insulating layer according to the present invention is laminated on an inner layer circuit board and heat-pressed.
First, the metal foil with an insulating layer of the present invention will be described in detail.

In the metal foil with an insulating layer of the present invention, the resin composition constituting the insulating layer contains a cyanate resin and / or a prepolymer thereof. Thereby, high heat resistance, low thermal expansibility, and a flame retardance can be improved.
The cyanate resin can be obtained, for example, by reacting a halogenated cyanide compound with a phenol and polymerizing by a method such as heating as necessary.

Although it does not specifically limit as cyanate resin, For example, bisphenol-type cyanate resin, such as novolak-type cyanate resin, bisphenol A-type cyanate resin, bisphenol E-type cyanate resin, tetramethylbisphenol F-type cyanate resin, etc. can be mentioned.
Among these, it is preferable to contain the novolak-type cyanate resin represented by the following general formula (I). Thereby, a glass transition temperature can be made high and the high heat resistance after a hardening and a flame retardance can be improved more.

The weight average molecular weight of the novolak cyanate resin represented by the general formula (I) is not particularly limited, but is preferably 500 to 4,500, and particularly preferably 600 to 3,000. When the weight average molecular weight is less than the lower limit value, the mechanical strength may be lowered. When the weight average molecular weight is more than the upper limit value, the curing rate of the resin composition is high, and the storage stability may be lowered.
This novolak-type cyanate resin can be obtained, for example, by reacting a novolak-type phenol resin with a compound such as cyanogen chloride or cyanogen bromide. Moreover, the commercial item prepared in this way can also be used.

  Since the cyanate resin does not generate a functional group having a large polarizability such as a hydroxyl group by a curing reaction, the dielectric property is very excellent. Moreover, since it has a rigid chemical structure, it has excellent heat resistance.

Moreover, what prepolymerized the said cyanate resin is preferably used in order to adjust a moldability and fluidity | liquidity, and is contained in the cyanate resin of this invention.
The prepolymerization is usually performed by heating and melting a cyanate resin. In the present invention, the prepolymer refers to one having a trimerization rate of 20 to 50 mol%, for example.
The trimerization rate can be determined using, for example, an infrared spectroscopic analyzer. A cyanate resin and a prepolymerized cyanate resin may be used in combination.

  Although content of the said cyanate resin is not specifically limited, 5 to 60 weight% of the whole resin composition is preferable, and 10 to 50 weight% is especially preferable. If the content is less than the lower limit, the effect of increasing the heat resistance and reducing the thermal expansion may be reduced. If the content exceeds the upper limit, the crosslink density is increased and the free volume is increased, which may reduce the moisture resistance. .

In the metal foil with an insulating layer of the present invention, the epoxy resin used contains substantially no halogen atom. Thereby, the halogen-free insulating layer can be easily achieved. Although it does not specifically limit as an epoxy resin, For example, a phenol novolak type epoxy resin, a bisphenol type epoxy resin, a naphthalene type epoxy resin, an aryl alkylene type epoxy resin etc. can be mentioned.
Note that “substantially free of halogen atoms” means, for example, that the content of halogen atoms in the epoxy resin is 1% by weight or less.

Although content of an epoxy resin is not specifically limited, 6 to 60 weight% of the whole resin composition is preferable, and 15 to 40 weight% is especially preferable. When the content is less than the lower limit value, the effect of improving the adhesion with the copper foil or the like used in the inner layer circuit may be reduced. When the content exceeds the upper limit value, the high heat resistance characteristic of the present invention is achieved. Or low thermal expansion may not be sufficient.

  Moreover, although the said epoxy resin is not specifically limited, It is preferable that it is a mixture of a 1st epoxy resin and a 2nd epoxy resin with a larger weight average molecular weight than a said 1st epoxy resin. Thereby, when producing a multilayer printed wiring board using the metal foil with an insulating layer of the present invention, it is possible to achieve both inner-layer circuit embedding property and flow control during press molding.

Although it does not specifically limit as said 1st epoxy resin, For example, a phenol novolak type epoxy resin, a bisphenol type epoxy resin, a naphthalene type epoxy resin, an aryl alkylene type epoxy resin etc. are mentioned. Among these, aryl alkylene type epoxy resins are preferable. Thereby, a flame retardance and moisture absorption solder heat resistance can be improved.
Here, the aryl alkylene type epoxy resin refers to an epoxy resin having one or more aryl alkylene groups in a repeating unit. For example, a xylylene type epoxy resin, a biphenyl dimethylene type epoxy resin, etc. are mentioned.
Among these, a biphenyl dimethylene type epoxy resin is preferable. As the biphenyldimethylene type epoxy resin, for example, those represented by the following general formula (II) can be used.

  The n of the biphenyldimethylene type epoxy resin represented by the general formula (II) is not particularly limited, but 1 to 10 is preferable, and 2 to 5 is particularly preferable. If the amount is less than this, the biphenyldimethylene type epoxy resin is easily crystallized, and the solubility in a general-purpose solvent is relatively lowered, which may make handling difficult. Moreover, when more than this, the fluidity | liquidity of resin will fall and it may become a cause of a molding defect.

  The weight average molecular weight of the first epoxy resin is not particularly limited, but is preferably 4,000 or less, particularly preferably 500 to 4,000, and most preferably 800 to 3,000. When the weight average molecular weight is less than the lower limit, tackiness may occur on the surface of the insulating layer, and when the upper limit is exceeded, solder heat resistance may be reduced.

  Although content of the said 1st epoxy resin is not specifically limited, 3-35 weight% of the whole resin composition is preferable, and 5-30 weight% is especially preferable. When the content is within the above range, particularly moisture-absorbing solder heat resistance can be improved.

Although it does not specifically limit as said 2nd epoxy resin, For example, a phenol novolak type epoxy resin, a bisphenol type epoxy resin, a naphthalene type epoxy resin, an aryl alkylene type epoxy resin etc. are mentioned.
Among these, bisphenol type epoxy resins are preferable. Thereby, adhesiveness with the copper foil etc. which are used for the inner layer circuit can be improved.

  The weight average molecular weight of the second epoxy resin is not particularly limited, but is preferably 5,000 or more, particularly preferably 5,000 to 100,000, and most preferably 8,000 to 80,000. When the weight average molecular weight is less than the lower limit, the effect of improving the film forming property of the insulating layer surface may be reduced. When the upper limit is exceeded, the resin varnish is prepared using the resin composition. The solubility of the epoxy resin may decrease.

  Although content of the said 2nd epoxy resin is not specifically limited, 3 to 30 weight% of the whole resin composition is preferable, and 5 to 20 weight% is especially preferable. When the content is within the above range, it is possible to improve the film forming property and the adhesion with the inner layer circuit at the time of producing the multilayer printed wiring board.

The resin composition used for the metal foil with an insulating layer of the present invention can contain an imidazole compound. Thereby, reaction of the said cyanate resin and an epoxy resin can be accelerated | stimulated, without reducing the insulation of a resin composition.
The imidazole compound is not particularly limited, and examples thereof include 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2, 4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- (2'-undecylimidazolyl) -ethyl-s-triazine, 2, Mention may be made of 4-diamino-6- [2′-ethyl-4-methylimidazolyl- (1 ′)]-ethyl-s-triazine.
Among these, an imidazole compound having two or more functional groups selected from an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a hydroxyalkyl group, and a cyanoalkyl group is preferable, and in particular, 2-phenyl-4,5 -Dihydroxymethylimidazole is preferred. Thereby, the heat resistance of the insulating layer can be improved, the thermal expansion can be reduced, and the water absorption rate can be lowered.

  Although content of the said imidazole compound is not specifically limited, 0.05-5 weight part is preferable with respect to a total of 100 weight part of cyanate resin and an epoxy resin, and 0.2-2 weight part is especially preferable. When the content is within the above range, the heat resistance can be particularly improved.

In the metal foil with an insulating layer of the present invention, the resin composition constituting the insulating layer contains an inorganic filler. Thereby, while being able to make low thermal expansion, the improvement of a flame retardance can be aimed at.
Although it does not specifically limit as said inorganic filler, For example, a talc, an alumina, glass, a silica, mica etc. can be mentioned.
Among these, silica is preferable, and fused silica is preferable in that it has excellent low expansibility. Although it does not specifically limit as a shape of a fused silica, For example, a crushed shape, spherical shape, etc. are mentioned. Among these, when spherical silica is used, the melt viscosity of the resin composition can be lowered, and the impregnation property into a nonwoven fabric formed of organic fibers can be improved.

The average particle size of the inorganic filler is not particularly limited, but is preferably 0.01 to 5 μm, and particularly preferably 0.2 to 2 μm. When the particle size of the inorganic filler is less than the lower limit, the viscosity of the resin varnish using the resin composition is increased, which may affect the workability when producing the insulating layer. When the upper limit is exceeded, phenomena such as sedimentation of the inorganic filler may occur in the resin varnish.
As the inorganic filler, it is particularly preferable to use spherical fused silica having an average particle diameter of 0.2 to 2 μm. Thereby, in addition to the said effect, the filling property of an inorganic filler can be improved.

  The content of the inorganic filler is preferably 30 to 70% by weight, and particularly preferably 40 to 60% by weight, based on the entire resin composition. If the content is less than the lower limit, the effect of low thermal expansion and low water absorption may be reduced, and if the content exceeds the upper limit, moldability may be reduced due to a decrease in fluidity.

  In the metal foil with an insulating layer of the present invention, the resin composition is not particularly limited, but preferably further contains a coupling agent. As a result, the wettability of the interface between the resin and the inorganic filler can be improved, and the non-woven fabric formed of organic fibers is uniformly impregnated / supported with the resin and the filler. Solder heat resistance can be improved.

  As the coupling agent, any of those usually used can be used, and among these, one selected from an epoxy silane coupling agent, a titanate coupling agent, an aminosilane coupling agent, and a silicone oil type coupling agent. It is preferable to use the above coupling agent. Thereby, wettability with the interface of an inorganic filler can be made high, and heat resistance can be improved more.

  Although content of the said coupling agent is not specifically limited, 0.05-3 weight part is preferable with respect to 100 weight part of inorganic fillers. When the content is less than the lower limit value, the inorganic filler cannot be sufficiently coated and the effect of improving heat resistance may be reduced, and when the content exceeds the upper limit value, the bending strength of the insulating layer may be reduced.

  If necessary, additives other than the above components can be added to the resin composition used for the metal foil with an insulating layer of the present invention as long as the object of the present invention is not impaired. Examples of the additive include an antifoaming agent and a leveling agent.

Although it does not specifically limit as a nonwoven fabric (henceforth only an "organic nonwoven fabric") formed with the organic fiber used in the metal foil with an insulating layer of this invention, For example, a polyamide fiber, an aromatic polyamide fiber, a polyester fiber , Aromatic polyester fibers, polyimide fibers and the like can be used. By using an organic nonwoven fabric formed from resin fibers having such a high glass transition temperature, the heat resistance of the insulating layer can be improved. In addition, the coefficient of linear expansion can be kept low within the range of the thermal history temperature in each process of manufacturing a printed wiring board, and internal stress distortion resulting from the difference in expansion coefficient with the metal foil can be reduced.
Among these, those containing polyester fibers are preferable, and aromatic polyester fibers are particularly preferable. Thereby, since it can be set as a low hygroscopic property, insulation and a dielectric characteristic can be improved.

Although it does not specifically limit as a method of manufacturing the metal foil with an insulating layer of the present invention, for example,
(1) A resin composition varnish in which the resin composition is dissolved and dispersed in an organic solvent or the like is prepared, this varnish is coated on a metal foil with a coater or the like, and an organic nonwoven fabric is superimposed on the coated surface, followed by heating and drying. . Subsequently, a method of obtaining the metal foil with an insulating layer in which the above varnish is applied again from the upper surface side of the organic nonwoven fabric and dried by heating, and the insulating layer containing the organic nonwoven fabric is bonded to the metal foil,
(2) An organic nonwoven fabric is immersed in the varnish and impregnated, and this is heated and dried to obtain a prepreg. Next, this prepreg is sandwiched between a metal foil and a release film, heated and pressed to integrate the prepreg and the metal foil, the release film is removed, and an insulating layer containing an organic nonwoven fabric is bonded to the metal foil. And a method for obtaining a metal foil with an insulating layer.

The solvent used for the preparation of the resin varnish desirably exhibits good solubility in the thermosetting resin component or imidazole compound in the resin composition, but a poor solvent is used within a range that does not adversely affect the resin varnish. It doesn't matter. Examples of the solvent exhibiting good solubility include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like.
Although the solid content in the resin varnish is not particularly limited, the solid content of the resin composition is preferably 30 to 80% by weight, and particularly preferably 40 to 70% by weight.

  In the metal foil with an insulating layer of the present invention, the thickness of the insulating layer is not particularly limited, but is preferably 10 to 100 μm, particularly preferably 20 to 80 μm.

  Further, the metal constituting the metal foil used in the metal foil with an insulating layer of the present invention is not particularly limited. For example, copper and / or copper-based alloy, aluminum and / or aluminum-based alloy, iron and / or iron-based alloy Etc.

Next, the multilayer printed wiring board of the present invention will be described.
The multilayer printed wiring board of the present invention is characterized in that the metal foil with an insulating layer of the present invention is laminated on an inner circuit board and is heated and pressed.
Although it does not specifically limit as a method of manufacturing the multilayer printed wiring board of this invention, For example, the insulating layer side of the metal foil with an insulating layer is laminated | stacked on the single side | surface or both surfaces of an inner-layer circuit board, Preferably this is 140-240 degreeC. A multilayer printed wiring board can be manufactured by heating and pressing at 0.5 to 4 MPa for 0.5 to 1.5 hours, filling the irregularities on the surface of the inner layer circuit board and molding. As the inner layer circuit board, for example, a conductor circuit formed on both surfaces of a copper-clad laminate by etching or the like and blackened can be used.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to this.

Example 1
(I) Preparation of resin varnish As the cyanate resin, 12% by weight of novolak cyanate resin PT-60 (Lonza Co., Ltd., weight average molecular weight 2600), novolak cyanate resin PT-30 (Lonza Co., Ltd., weight average molecular weight 700) ) 23.3% by weight, as the first epoxy resin, biphenyl dimethylene type epoxy resin (Nippon Kayaku Co., Ltd., NC-3000P, epoxy equivalent 275, weight average molecular weight 2000) 12% by weight, second epoxy resin As bisphenol A type and F type mixed epoxy resin Epicoat 4275 (Japan Epoxy Resin Co., Ltd., weight average molecular weight 57000) 12% by weight, an imidazole compound (Shikoku Kasei Kogyo Co., Ltd., 2-phenyl-4, 5-dihydroxymethylimidazole) 0.5% by weight Was added and dissolved in methyl ethyl ketone. Furthermore, spherical fused silica SO-25H (manufactured by Admatechs Co., Ltd., average particle size 0.5 μm) 40% by weight as an inorganic filler and an epoxy silane coupling agent A-187 (manufactured by Nihon Unicar Co., Ltd.) as a surfactant. The resin varnish having a solid content of 60% by weight was obtained by adding 0.5% by weight to the inorganic filler and stirring for 10 minutes using a high-speed stirrer.

(II) Manufacture of metal foil with insulating layer The resin varnish is coated on the anchor surface of a copper foil having a thickness of 18 μm with a comma coater, and subsequently, an aromatic polyester nonwoven fabric (basis weight as an organic nonwoven fabric on the coated surface) 25 g / m ² , manufactured by Mitsubishi Paper Industries Co., Ltd.), the nonwoven fabric is impregnated with a resin varnish, passed through a drying step, and then coated with the same resin varnish from the upper surface side of the nonwoven fabric with a comma coater. A copper foil with an insulating layer having an insulating layer with a thickness of 70 μm after drying was obtained.

(III) Manufacture of multilayer printed wiring board Halogen-free FR-4 inner layer circuit board (copper foil thickness 18 μm, insulating layer thickness 0.2 mm, L / S = 120/180 μm, clearance hole) with predetermined inner layer circuits formed on both sides 1 mmφ, 3 mmφ, slit 2 mm) are stacked one by one so that the insulating layer of the metal foil with the insulating layer comes to the inner layer circuit side, and this is stacked in a vacuum press apparatus at a pressure of 2 MPa and a temperature of 220 ° C. for 1 hour. Heat-press molding was performed to obtain a multilayer printed wiring board.

( Comparative Example 4 )
A resin varnish, a metal foil with an insulating layer, and a multilayer printed wiring board were obtained in the same manner as in Example 1 except that the amount of the resin varnish used was as follows.
25% by weight of novolak type cyanate resin PT-30, 22.3% by weight of biphenyldimethylene type epoxy resin NC-3000P, 12% by weight of bisphenol A type and F type mixed epoxy resin Epicoat 4275, 0.5% by weight of imidazole compound %, Spherical fused silica SO-25H was 40% by weight, and epoxy silane coupling agent A-187 (manufactured by Nihon Unicar Co., Ltd.) was 0.5% by weight based on the inorganic filler.

(Example 3)
A resin varnish, a metal foil with an insulating layer, and a multilayer printed wiring board were obtained in the same manner as in Example 1 except that the amount of the resin varnish used was as follows.
12% by weight of novolak type cyanate resin PT-60, 10% by weight of novolak type cyanate resin PT-30, 25.3% by weight of biphenyldimethylene type epoxy resin NC-3000P, bisphenol A type, F type mixed epoxy resin epicoat 12275% by weight of 4275, 0.5% of imidazole compound, 40% by weight of spherical fused silica SO-25H, and 0.5% of epoxy silane coupling agent A-187 (manufactured by Nihon Unicar Co., Ltd.) with respect to the inorganic filler. % By weight.

Example 4
A resin varnish, a metal foil with an insulating layer, and a multilayer printed wiring board were obtained in the same manner as in Example 1 except that the amount of the resin varnish used was as follows.
5% by weight of novolak type cyanate resin PT-60, 10.2% by weight of novolak type cyanate resin PT-30, 12% by weight of biphenyldimethylene type epoxy resin NC-3000P, bisphenol A type, F type mixed epoxy resin epicoat 12275% by weight of 4275, 0.5% of imidazole compound, 60% by weight of spherical fused silica SO-25H, and 0.5% of epoxy silane coupling agent A-187 (manufactured by Nihon Unicar Co., Ltd.) with respect to the inorganic filler. % By weight.

(Comparative Example 1)
A resin varnish, a metal foil with an insulating layer, and a multilayer printed wiring board were obtained in the same manner as in Example 1 except that the amount of other resin was changed as follows without using an epoxy resin.
40% by weight of novolak type cyanate resin PT-60, 19.3% by weight of novolak type cyanate resin PT-30, 0.5% of imidazole compound, 40% by weight of spherical fused silica SO-25H, epoxy silane coupling agent A -187 (manufactured by Nippon Unicar Co., Ltd.) was 0.5% by weight based on the inorganic filler.

(Comparative Example 2)
A resin varnish, a metal foil with an insulating layer, and a multilayer printed wiring board were obtained in the same manner as in Example 1 except that the amount of other resin was changed as follows without using a cyanate resin.
16.3% by weight of biphenyldimethylene type epoxy resin NC-3000P, 43% by weight of bisphenol A type and F type mixed epoxy resin Epicoat 4275, 0.5% of imidazole compound, 40% by weight of spherical fused silica SO-25H, Epoxy silane coupling agent A
-187 (manufactured by Nippon Unicar Co., Ltd.) was 0.5% by weight based on the inorganic filler.

(Comparative Example 3)
A resin varnish was prepared in the same manner as in Example 1 with the blending amount of the resin varnish used as follows.
Next, without using an organic nonwoven fabric, the resin varnish is coated on an anchor surface of a copper foil having a thickness of 18 μm with a comma coater and dried by heating, whereby a resin composition having a thickness after drying of 70 μm. A copper foil with an insulating layer having an insulating layer consisting only of was obtained. Thereafter, a multilayer printed wiring board was obtained in the same manner as in Example 1.
33% by weight of novolac type cyanate resin PT-60, 10% by weight of novolak type cyanate resin PT-30, 16.3% by weight of biphenyldimethylene type epoxy resin NC-3000P, 0.5% of imidazole compound, spherical fused silica The SO-25H was 40% by weight, and the epoxy silane coupling agent A-187 (manufactured by Nippon Unicar Co., Ltd.) was 0.5% by weight with respect to the inorganic filler.

  The following evaluation was performed about the metal foil with an insulating layer and multilayer printed wiring board obtained by each Example and the comparative example. The obtained results are shown in Table 1.

(I) Flame retardance Flame retardancy was measured by UL-94 standard, vertical method, etching the entire surface of the copper foil of the multilayer printed wiring board.

(II) Glass transition temperature After laminating a copper foil on the insulating layer side of the metal foil with an insulating layer, and performing hot press molding at a pressure of 2 MPa and a temperature of 220 ° C. for 1 hour with a vacuum press, the entire surface of the copper foil is etched. A cured product of the insulating layer was obtained.
A test piece of 10 mm × 60 mm was cut out from the obtained insulating layer cured product, heated at 5 ° C./min using DMA (TA Instruments Co., Ltd.), and the peak position of tan δ was defined as the glass transition temperature. did.

(III) Linear expansion coefficient A copper foil is laminated on the insulating layer side of the metal foil with an insulating layer, and after heat-pressing at a pressure of 2 MPa and a temperature of 220 ° C. for 1 hour with a vacuum press apparatus, the copper foil is etched entirely. A cured product of the insulating layer was obtained.
A 4 mm × 20 mm test piece was cut out from the obtained cured insulating layer, and the linear expansion coefficient was measured at 10 ° C./min using TMA (TA Instruments Co., Ltd.).

(IV) Formability The entire surface of the multilayer printed wiring board was etched, and the presence or absence of molding voids was visually observed.

(V) Moisture-absorbing solder heat resistance A 50 mm x 50 mm test piece was cut out from the multilayer printed wiring board, and the entire surface of one side and half of the copper foil on the other side were etched and removed in accordance with JIS K 6481. This was treated with a pressure cooker at 125 ° C. for 2 hours, and then floated in a solder bath at 260 ° C. with the copper foil face down for 180 seconds to confirm the presence or absence of swelling and peeling.

(VI) Dielectric constant / dielectric loss tangent Copper foil with insulating layer removed from the entire surface by etching, multiple sheets are stacked so that the thickness is 1.0 mm, and copper foil is stacked on both sides of the copper foil. Then, heat pressing was performed at a pressure of 2 MPa and a temperature of 220 ° C. for 1 hour. Thereafter, the copper foil was entirely etched, and 97 mm × 25 mm, 53 mm × 25 mm, and 37 mm × 25 mm test pieces were cut out from the obtained laminate, and the relative dielectric constant and dielectric loss tangent were measured by the triplate line resonance method.

(VII) Laser processability The multilayer printed wiring board is etched entirely, the resulting laminate is processed with a UV YAG laser (manufactured by Mitsubishi Electric Corporation), and the resin residue in the upper part and cross section of the via hole after desmear treatment is observed with a microscope. Those having no resin residue and those having a resin residue partially but having no practical problem were defined as “good”.

(VIII) Tensile strength A copper foil is laminated on the insulating layer side of the metal foil with an insulating layer, heat-pressed at a pressure of 2 MPa and a temperature of 220 ° C. for 1 hour with a vacuum press, and the entire surface of the copper foil is etched. A cured product was obtained.
Using this sample, a tensile test was performed at a test speed of 50 mm / min in accordance with JIS K 7161.

As is clear from Table 1, Examples 1, 3 and 4 have a high glass transition temperature, a small coefficient of thermal expansion, good dielectric properties, workability, flame retardancy, and mechanical strength. It was an excellent balance.
On the other hand, although the comparative example 1 used the resin composition which does not mix | blend an epoxy resin, heat resistance fell. Although the comparative example 2 used the resin composition which does not mix | blend cyanate resin, a flame retardance cannot be provided, a glass transition temperature falls, and it is inferior also in a dielectric property, mechanical strength, and low thermal expansibility. became. And although the comparative example 3 produced the metal foil with an insulating layer, without using an organic nonwoven fabric, a dielectric characteristic fell a little and it became inferior also in mechanical strength.

The present invention is a metal foil with an insulating layer that is used in the production of a multilayer printed wiring board, has high heat resistance, high rigidity, low thermal expansion, and can form an insulating layer excellent in flame retardancy. It can be suitably used as a build-up material for multilayer printed wiring boards that can cope with higher density. And the multilayer printed wiring board of this invention can be used suitably as a printed wiring board corresponding to high-density mounting.

Claims (3)

An insulating layer composed of a resin composition containing a curable resin and a nonwoven fabric formed of organic fibers is a metal foil with an insulating layer bonded to a metal foil, and the resin composition is a cyanate resin. And / or a prepolymer thereof, a bisphenol A-type, F-type mixed epoxy resin substantially free of halogen atoms, and an inorganic filler, and a metal foil with an insulating layer. The metal foil with an insulating layer according to claim 1, wherein the organic fibers contain polyester fibers. A multilayer printed wiring board obtained by laminating the metal foil with an insulating layer according to claim 1 or 2 on an internal circuit board and heating and pressing.