JP2015086293A - Prepreg and multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg capable of forming an insulating layer which can achieve a low thermal expansion coefficient, provide appropriate surface roughness and is improved in adhesiveness to a conductor layer.SOLUTION: There is provided a prepreg which comprises a first resin layer A containing a fiber substrate 2 and a second resin layer B which contains no fiber substrate 2 and is formed on at least one surface of the first resin layer A. The first resin layer A contains 100 to 400 pts.mass of an inorganic filler based on 100 pts.mass of a resin component. The second resin layer B contains no inorganic filler or contains 50 pts.mass or less of an inorganic filler based on 100 pts.mass of a resin component. The resin component of the second resin layer B comprises a thermosetting resin B1 having a functional group equivalent of 150 to 400 g/eq, a thermosetting resin B2 having a functional group equivalent of 450 to 600 g/eq and a curing agent. The thickness of the second resin layer B is one half or less of the thickness of the first resin layer A.

Description

  The present invention relates to a prepreg and a multilayer printed wiring board.

  Printed wiring boards are widely used in various fields such as electronic devices, communication devices, and computers. In recent years, especially in small portable devices such as portable communication terminals and notebook PCs, multifunction, high performance, thinning and downsizing are rapidly progressing, and semiconductor packages mounted on such devices are also highly integrated. , Thinner and smaller. Along with this, the mounting substrate (printed wiring board) of the semiconductor package is also required to have high performance such as miniaturization, multilayering, thinning, and mechanical characteristics of the wiring pattern.

  A multilayer printed wiring board having an inner layer circuit is used as a mounting substrate for a semiconductor package. Conventionally, as a method for producing this multilayer printed wiring board, there is known a method in which a copper foil is laminated and pressed on an inner layer circuit board through a prepreg, interlayer conduction is established by a through hole, and a copper foil is patterned by etching to form a circuit. It has been. However, since this method forms a circuit by etching, it cannot sufficiently cope with fine pattern wiring. Therefore, in recent years, as a technique that can cope with such a fine pattern, a conductor insulating layer is formed on the surface of the conductor layer of the inner circuit board using a prepreg or a resin film, and a wiring pattern is formed on the surface by plating. A build-up type multilayer printed wiring board is used in which a multilayer structure is formed by alternately repeating these steps. In this build-up method, the surface of the resin insulation layer is usually roughened with an oxidizing agent such as potassium permanganate in order to improve the adhesion between the conductor layer and the resin insulation layer. By performing the roughening treatment in this way, small irregularities are formed on the surface of the resin insulating layer, the contact area with the conductor layer formed by plating is increased, and the adhesion is improved. At this time, if the surface roughness such as the unevenness of the unevenness of the surface of the resin insulating layer due to the roughening treatment is too large, it becomes difficult to accurately form a fine wiring pattern.

  Patent Document 1 describes an invention of an epoxy resin composition that can be made into a resin insulating layer having a suitable surface roughness by roughening treatment. In the epoxy resin composition of Patent Document 1, two types of epoxy resins having different solubility when roughened are used as the resin component, so that the surface roughness does not become too large and high adhesion is realized. That's it.

Japanese Patent No. 4600399

  By the way, the mounting method of the semiconductor package has recently shifted from the wire bonding method to the connection by the flip chip method, but on the other hand, as the semiconductor package becomes thinner, the CTE (thermal expansion) with the substrate material constituting the mounting substrate Warpage is likely to occur due to a difference in coefficient of thermal expansion, and prevention of this warpage is a major issue. In order to prevent this warpage, in the insulating material constituting the insulating layer of the substrate, a technique of reducing CTE by blending a thermosetting resin such as an epoxy resin with a high content of an inorganic filler has been performed. . However, if the content of the inorganic filler contained in the insulating layer is increased, the CTE can be reduced, but the adhesion with the conductor layer formed on the surface of the insulating layer is reduced, or it is difficult to form a fine wiring pattern. The problem of becoming. That is, when the conductor layer of the multilayer printed wiring board is formed of a copper foil, the resin filler is low because the content of the inorganic filler in the resin insulating layer is large, so that the adhesion with the copper foil is lowered. In addition, when the conductor layer of a multilayer printed wiring board is formed by plating, the inorganic filler exposed on the surface of the resin insulation layer increases and the surface roughness increases, so a fine fine wiring pattern can be accurately obtained. It becomes difficult to form.

  In Patent Document 1, although it is described that an inorganic filler can be contained in the epoxy resin composition, it is described that the content is preferably 5 to 50% by weight of the entire resin composition, and contained Since the rate is in a relatively small range, the CTE was not sufficiently reduced. If the content of the inorganic filler in the epoxy resin composition of Patent Document 1 is as high as 50% by weight or more of the entire resin composition, as described above, on the surface of the insulating layer, There is a problem that the adhesiveness with the conductor layer to be formed is lowered, or that it is difficult to form a fine wiring pattern.

  The present invention has been made in view of the above points, and can form an insulating layer that can realize a low coefficient of thermal expansion, can have a suitable surface roughness, and has improved adhesion to a conductor layer. An object of the present invention is to provide a prepreg capable of forming a multilayer printed wiring board.

The prepreg according to the present invention includes a first resin layer A containing a fiber substrate,
A second resin layer B formed on at least one surface of the first resin layer A without including a fiber substrate;
With
Said 1st resin layer A contains 100-400 mass parts inorganic filler with respect to 100 mass parts of resin components,
Said 2nd resin layer B does not contain an inorganic filler, or contains 50 mass parts or less of an inorganic filler with respect to 100 mass parts of resin components,
The resin component of the second resin layer B includes a thermosetting resin B1 having a functional group equivalent of 150 to 400 g / eq, a thermosetting resin B2 having a functional group equivalent of 450 to 600 g / eq, and a curing agent. Contains,
The thickness of the second resin layer B is ½ or less of the thickness of the first resin layer A.

In the prepreg, the thickness of the first resin layer A is 15 μm or more,
The thickness of the second resin layer B is preferably 5 to 15 μm.

In the prepreg, the thermosetting resin B1 is an epoxy resin having an epoxy equivalent of 150 to 400 g / eq,
The thermosetting resin B2 is preferably an epoxy resin having an epoxy equivalent of 450 to 600 g / eq.

In the prepreg, the thermosetting resin B1 is a polyfunctional epoxy resin having three or more epoxy groups in one molecule,
The thermosetting resin B2 is preferably an epoxy resin having 2 to 2.3 epoxy groups in one molecule.

  In the prepreg, the content ratio of the thermosetting resin B1 and the thermosetting resin B2 is such that the mass ratio of the thermosetting resin B2 to the thermosetting resin B1 is (B2) / (B1) = 4. It is preferable that it is 2-9.0.

The multilayer printed wiring board according to the present invention comprises a cured product of the prepreg as an insulating layer,
The surface of the cured product layer of the second resin layer B is roughened and a plated conductor layer is formed thereon.

  According to the present invention, a low thermal expansion coefficient can be realized, and a suitable surface roughness can be obtained, and an insulating layer with improved adhesion to the conductor layer can be formed.

An example of embodiment of this invention is shown, (a) is schematic sectional drawing of the prepreg in which the 2nd resin layer B was formed in the single side | surface of the 1st resin layer A, (b) is the 1st resin layer A It is a schematic sectional drawing of the prepreg in which the 2nd resin layer B was formed in both surfaces. It is a schematic sectional drawing which shows an example of the multilayer printed wiring board manufactured using the prepreg shown to Fig.1 (a).

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of an embodiment of a prepreg 1 according to the present invention. The prepreg 1 includes a first resin layer A and a second resin layer B. The first resin layer A and the second resin layer B are in a semi-cured state (B stage state).

  The first resin layer A is a semi-cured product of the first resin composition and includes the fiber substrate 2. The first resin composition contains a resin component and an inorganic filler. The resin component includes a thermosetting resin and, if necessary, a curing agent and a curing accelerator. The 1st resin layer A contains 100-400 mass parts of inorganic fillers with respect to 100 mass parts of resin components.

  Here, as a thermosetting resin, an epoxy resin, a phenol resin, cyanate resin, a melamine resin, an imide resin etc. can be used, for example. One or more selected from these groups can be used. Among the above thermosetting resins, an epoxy resin is particularly preferable. Examples of the epoxy resin include naphthalene skeleton type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, alicyclic epoxy resin, polyfunctional phenol diglycidyl ether compound A diglycidyl ether compound of a polyfunctional alcohol, a phenolic novolac type epoxy resin, a cresol novolak type epoxy resin, a bisphenol A novolak type epoxy resin, and a brominated form thereof, which are glycidyl etherified products of polycondensates of phenols and formaldehyde An epoxy resin etc. can be mentioned. One or more selected from these groups can be used. In particular, both the first resin layer A and the second resin layer B are preferably resin systems containing an epoxy resin. In this case, when the prepreg 1 is cured, cross-linking occurs in the boundary region between the first resin layer A and the second resin layer B, and the interlayer strength can be further increased.

  Further, the curing agent can be appropriately selected from known materials from the viewpoint of adaptability in combination with a thermosetting resin, such as a phenolic curing agent, an amine curing agent, a dicyandiamide curing agent, and the like. Is mentioned. One or more selected from these groups can be used. Examples of the phenolic curing agent include bifunctional phenolic resins such as bisphenol A, novolac type phenolic resins, and phenolic novolac resins having a triazine ring. One or more selected from these groups can be used. The phenol-based novolak resin having a triazine ring is a phenol-based novolak resin containing a structural unit derived from a compound having a triazine ring.

  Moreover, as a hardening accelerator, if it can accelerate | stimulate hardening reaction, it can use without a restriction | limiting in particular. Specific examples include imidazoles such as 2-methylimidazole, tertiary amines such as triethylenediamine, and organic phosphines such as triphenylphosphine. One or more selected from these groups can be used.

  Examples of the inorganic filler include silica, aluminum hydroxide, magnesium hydroxide, E glass powder, alumina, magnesium oxide, titanium dioxide, barium titanate, calcium silicate, calcium carbonate, clay, talc and the like. it can. One or more selected from these groups can be used. Among these, it is preferable to use silica. As silica, spherical silica, crushed silica, or the like can be used. The average particle diameter of the inorganic filler is, for example, 0.1 to 20 μm, preferably 0.5 to 10 μm. In addition, an average particle diameter means the weight average particle diameter measured using the laser diffraction type particle size distribution measuring apparatus.

  Moreover, as the fiber base material 2, for example, a woven fabric (cloth) or a nonwoven fabric of inorganic fibers such as glass, an aramid cloth, a polyester cloth, paper, or the like can be used. In particular, the fiber base 2 is preferably a glass cloth.

  As described above, the first resin layer A includes the fiber base 2 and contains a relatively high proportion of the inorganic filler, so that the cured product has a coefficient of thermal expansion (CTE). Can be made sufficiently low. If the content of the inorganic filler in the first resin layer A is less than 100 parts by mass, the coefficient of thermal expansion of the cured product of the first resin layer A cannot be sufficiently reduced. In addition, if the content of the inorganic filler exceeds 400 parts by mass, when molding using the prepreg 1, the melt viscosity of the first resin composition becomes too large, and molding defects such as scum and voids may occur. is there.

  On the other hand, the second resin layer B is formed on at least one surface of the first resin layer A. That is, the second resin layer B may be formed on one side of the first resin layer A as shown in FIG. 1A, or formed on both sides of the first resin layer A as shown in FIG. May be. And the conductor layer by a metal is formed in the surface of the hardened | cured material layer 32 which the 2nd resin layer B hardened | cured as mentioned later.

  The second resin layer B is a semi-cured product of the second resin composition and does not include the fiber substrate 2. The second resin composition includes a thermosetting resin B1, a thermosetting resin B2, and a curing agent described later as resin components. The second resin layer B does not contain an inorganic filler or can contain an inorganic filler as long as the content is relatively small. When the 2nd resin layer B contains an inorganic filler, the content shall be 50 mass parts or less with respect to 100 mass parts of resin components. When the 2nd resin layer B does not contain an inorganic filler, in the hardened material layer 32 which 2nd resin layer B hardened, as mentioned below, the effect by the resin component of the 2nd resin composition is acquired suitably. Adhesion to the conductor layer is improved. In addition, even if the second resin layer B contains an inorganic filler, if the content is small as described above, the effect on the adhesion of the cured product layer 32 to the conductor layer is substantially satisfactory. Therefore, suitable adhesion can be obtained.

  Here, the resin component of the second resin layer B (or the second resin composition) includes a thermosetting resin B1 having a functional group equivalent of 150 to 400 g / eq and a thermosetting resin having a functional group equivalent of 450 to 600 g / eq. Containing a functional resin B2 and a curing agent. The functional groups of the thermosetting resin B1 and the thermosetting resin B2 can react with the curing agent. The thermosetting resin B1 having a small functional group equivalent reacts with a curing agent to form a cured product having a high crosslink density, while the thermosetting resin B2 having a relatively large functional group equivalent has a curing agent and It reacts to become a cured product having a lower crosslink density than the above cured product. And when the hardened | cured material layer 32 of the 2nd resin layer B roughens the surface, the hardened | cured material of thermosetting resin B2 with low crosslinking density is hardened | cured material of thermosetting resin B1 with high crosslinking density. Is also preferentially dissolved, resulting in a fine uneven surface with a relatively small surface roughness. This fine concavo-convex surface contributes to an improvement in adhesion to the conductor layer. The surface roughness can be evaluated by, for example, arithmetic average roughness (Ra) and ten-point average roughness (Rz).

  In addition, when the functional group equivalent of thermosetting resin B1 is less than 150 g / eq, the surface roughness of the surface formed by roughening the obtained cured product becomes too small, and when it exceeds 400, Said surface roughness becomes too large, and adhesiveness with a conductor layer falls. Further, when the functional group equivalent of the thermosetting resin B2 is less than 450 g / eq, the surface roughness of the surface formed by roughening the resulting cured product becomes too small, resulting in a decrease in adhesion, and 600 If it exceeds 1, the above-mentioned surface roughness becomes too large.

  In particular, the thermosetting resin B1 is preferably an epoxy resin having an epoxy equivalent of 150 to 400 g / eq, and the thermosetting resin B2 is preferably an epoxy resin having an epoxy equivalent of 450 to 600 g / eq. Thus, if both thermosetting resin B1 and thermosetting resin B2 are epoxy resins, compared with other thermosetting resins, the adhesive force with respect to the conductor layer of the hardened | cured material layer 32 of the 2nd resin layer B is improved. It can be improved further.

  Further, the thermosetting resin B1 is a polyfunctional epoxy resin having 3 or more epoxy groups in one molecule, and the thermosetting resin B2 is an epoxy resin having 2 to 2.3 epoxy groups in one molecule. Preferably there is.

  Specific examples of polyfunctional epoxy resins having three or more epoxy groups in one molecule include diglycidyl ether compounds of polyfunctional phenols, diglycidyl ether compounds of polyfunctional alcohols, and glycidyl ethers of polycondensates of phenols and formaldehyde. And phenolic novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins and brominated epoxy resins. One or more selected from these groups can be used. Of these, phenol novolac type epoxy resins are preferably used because of their high reactivity.

  Specific examples of the epoxy resin having 2 to 2.3 epoxy groups in one molecule include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, and biphenyl type epoxy resin. . Among these, bisphenol A type epoxy resins are preferable, and brominated bisphenol A type epoxy resins are particularly preferable. When such a brominated bisphenol A type epoxy resin is used, a bromine atom becomes a steric hindrance during curing, resulting in incomplete crosslinking, and when the cured product is roughened, Since this part dissolves so as to form fine irregularities, it is considered that it contributes to showing high adhesion.

  When a polyfunctional epoxy resin having three or more epoxy groups in one molecule is used as the thermosetting resin B1, a portion having a high crosslinking density can be formed in the cured product layer 32 of the second resin layer B. On the other hand, when an epoxy resin having 2 to 2.3 epoxy groups in one molecule is used as the thermosetting resin B2, a portion having a low crosslinking density can be formed in the cured product layer 32 of the second resin layer B. . Therefore, when the above two types of epoxy resins are used in combination, a portion having a relatively high crosslink density and a portion having a low crosslink density can coexist in the cured product layer 32 of the second resin layer B.

  In the second resin layer B, the content ratio of the thermosetting resin B1 and the thermosetting resin B2 is such that the mass ratio of the thermosetting resin B2 to the thermosetting resin B1 is (B2) / (B1) = 4. It is preferable that it is 2-9.0. In this case, when the surface of the cured product layer 32 of the second resin layer B is roughened, a fine uneven surface with a relatively small surface roughness is formed favorably. That is, the concave and convex portions on the uneven surface are formed in a well-balanced manner. Therefore, the adhesiveness with respect to the conductor layer of the hardened | cured material layer 32 of the 2nd resin layer B can be improved.

  In addition, as the curing agent in the second resin composition, those mentioned as the curing agent in the first resin composition can be used, and a particularly preferable curing agent is a phenol novolak resin having a triazine ring. This phenolic novolak resin having a triazine ring may be used alone or in combination with other phenolic compounds as a curing agent.

  The second resin composition may further contain a curing accelerator as necessary. In that case, as a hardening accelerator, it can select from the same compound as what was illustrated as a hardening accelerator in a 1st resin composition.

  In the present invention, as described above, the second resin layer B does not include the fiber base material 2 and is formed of a semi-cured product of the second resin composition. Thereby, as will be described later, the second resin layer B can be formed in a relatively thin state on the surface of the first resin layer A. Moreover, the 2nd resin layer B does not contain the inorganic filler, or even if it contains, the amount is a small amount of 50 parts by mass or less with respect to 100 parts by mass of the resin component as described above. Therefore, since the surface of the cured product layer 32 of the second resin layer B is not affected by the inorganic filler or does not have a significant effect, the cured product layer 32 of the second resin layer B has a rough surface. When the treatment is performed, a fine uneven surface having a relatively small surface roughness is formed well, and the adhesion to the conductor layer is improved. Here, when the content of the inorganic filler in the second resin layer B exceeds 50 parts by mass, the amount of the inorganic filler exposed on the surface of the insulating layer 3 after the prepreg 1 is cured, in particular, the cured product layer 32 increases. There is a possibility that the surface roughness increases and the adhesion to the conductor layer decreases. However, since the coefficient of thermal expansion of the cured product layer 32 of the second resin layer B is reduced by containing even a small amount of the inorganic filler, the adhesiveness is increased when the inorganic filler is contained in the second resin layer B. It is sufficient that the content of the inorganic filler is low to the extent that it does not adversely affect the content.

  In addition, when the 2nd resin layer B contains an inorganic filler, the thing similar to the inorganic filler which the 1st resin layer A contains can be used as this inorganic filler. In this case, the average particle size of the inorganic filler is preferably 2 μm or less, more preferably 1 μm or less. Thus, by making the average particle diameter of an inorganic filler comparatively small, when the 2nd resin layer B contains an inorganic filler, the influence on the said adhesiveness can be made small.

  Moreover, the thickness of the 2nd resin layer B is 1/2 or less of the thickness of the 1st resin layer A, Preferably it is 1/3 or less. Thus, since the thickness of the 2nd resin layer B is thin and the thickness of the 1st resin layer A is thick, the cured | curing material layer 32 of the 2nd resin layer B has the thermal expansion coefficient as the whole cured | curing material of the prepreg 1 in it. The thermal expansion coefficient characteristic of the cured product layer 31 of the first resin layer A is predominantly reflected rather than the thermal expansion coefficient characteristic. In addition, when the thickness of the 2nd resin layer B exceeds 1/2 of the thickness of the 1st resin layer A, the thermal expansion coefficient as the whole cured | curing material of the prepreg 1 tends to become high.

  Next, an example of the manufacturing method of the prepreg 1 which is embodiment of this invention is demonstrated.

  First, the first resin layer A can be formed by impregnating the fiber substrate 2 with the varnish of the first resin composition and drying it by heating until it is in a semi-cured state.

  Here, in preparing the varnish of the first resin composition, a base varnish is first prepared by blending a thermosetting resin, and optionally a curing agent, a curing accelerator, and a solvent. Next, the varnish of a 1st resin composition can be prepared by mix | blending an inorganic filler with a base varnish.

  Examples of the solvent include aromatic hydrocarbons such as benzene and toluene, amides such as N, N-dimethylformamide (DMF), ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, cellosolves, and the like. Can be mentioned. One or more selected from these groups can be used.

  Next, the varnish of the second resin composition is applied to one side or both sides of the first resin layer A formed as described above, and this is heated and dried until it becomes a semi-cured state, whereby the second resin layer B can be formed to obtain a prepreg 1 as shown in FIG. The coating method of the varnish of the second resin composition is not particularly limited, and examples thereof include known coating methods such as a spray coating method, a dip coating method, a roll coating method, a curtain coating method, a die coating method, and a slit coating method.

  Here, the varnish of the second resin composition is a thermosetting resin B1 having a functional group equivalent of 150 to 400 g / eq, a thermosetting resin B2 having a functional group equivalent of 450 to 600 g / eq, a curing agent, and if necessary. It can be prepared by blending a curing accelerator and a solvent. An inorganic filler is mix | blended with the varnish of a 2nd resin composition as needed.

  In the prepreg 1 obtained as described above, the thickness of the first resin layer A is preferably 15 μm or more, and the thickness of the second resin layer B is preferably 5 to 15 μm. If the thickness of the 1st resin layer A is 15 micrometers or more, the influence of the thermal expansion characteristic which the 1st resin layer A has can be enlarged relatively, and the thermal expansion coefficient as a hardened | cured material of the prepreg 1 is made still lower. be able to. In addition, although the upper limit of the thickness of the 1st resin layer A is not specifically limited, For example, it is 200 micrometers. If the thickness of the second resin layer B is too thin, part of the constituent components of the first resin layer A melted in the process of curing the prepreg 1 are mixed with the second resin layer B, and the surface of the second resin layer B There exists a possibility that the adhesive force of the hardened | cured material layer 32 may fall under the influence of the structural component of the 1st resin layer A to the side. However, if the thickness of the 2nd resin layer B is 5 micrometers or more, the fall of the adhesiveness with respect to the conductor layer of the hardened | cured material layer 32 can be suppressed. Further, if the thickness of the second resin layer B is 15 μm or less, the influence of the thermal expansion characteristics of the second resin layer B can be relatively reduced, and the coefficient of thermal expansion as a cured product of the prepreg 1 is increased. This can be suppressed.

  Next, an example of an embodiment of the multilayer printed wiring board 5 according to the present invention will be described. As shown in FIG. 2, the multilayer printed wiring board 5 includes the cured product of the prepreg 1 as an insulating layer 3 on the surface of the inner circuit board 50 on which the conductor layer 40 is formed. When the prepreg 1 is formed by forming the second resin layer B on one side of the first resin layer A as shown in FIG. 1A, the cured product of the prepreg 1 is a cured product layer 31 of the first resin layer A. And the insulating layer 3 will be formed in the state which the cured | curing material layer 32 of the 2nd resin layer B laminated | stacked. Further, when the prepreg 1 is one in which the second resin layer B is formed on both surfaces of the first resin layer A as shown in FIG. 1B, the cured product of the prepreg 1 is cured of the two second resin layers B. The insulating layer 3 is formed in a state where the cured product layer 31 of the first resin layer A is sandwiched between the product layers 32.

  Here, when using the prepreg 1 in which the second resin layer B is formed on one side of the first resin layer A as shown in FIG. 1A, particularly on the inner circuit board 50 side as shown in FIG. It is preferable to overlap the first resin layer A and make the second resin layer B outside.

  And the surface of the hardened | cured material layer 32 of the 2nd resin layer B is roughened by the roughening liquid, and the plating conductor layer 4 is formed on it. Although not shown, a plurality of insulating layers 3 and plated conductor layers 4 may be alternately laminated by a build-up method.

  Below, the specific form of the multilayer printed wiring board 5 is demonstrated, explaining the manufacturing method of the multilayer printed wiring board 5. FIG.

  In manufacturing the multilayer printed wiring board 5, first, an inner layer circuit board 50 in which a conductor layer 40 that can be an inner layer circuit is formed in advance on the outer surface is prepared, and this inner layer circuit board is used using an acid solution or the like as necessary. 50 conductor layers 40 are subjected to inner layer roughening treatment such as black oxidation treatment (blackening treatment). Next, after the above prepreg 1 is overlaid on the outer surface of the inner layer circuit board 50 and a protective film is further overlaid, these are integrally laminated by a molding method such as a multistage vacuum press. After removing the protective film after molding, the surface of the insulating layer 3 formed by curing the prepreg 1 is roughened with a roughening solution.

  Here, the roughening solution is not particularly limited as long as it contains both or one of an acid and an oxidizing agent. For example, it can be roughened with an oxidizing agent such as permanganate, dichromate, ozone, hydrogen peroxide / sulfuric acid, nitric acid.

  Furthermore, a set of three types of “Circumposit MLB211”, “Circuposit MLB213” and “Circuposit MLB216” manufactured by Rohm and Haas may be used as a roughening solution. The roughening treatment with the roughening liquid can be performed by immersing the laminated plate after the prepreg 1 is laminated in the roughening liquid, and can be performed a plurality of times by changing the type of the roughening liquid. The temperature of the roughening solution can be set to 40 to 90 ° C., and the immersion time can be set to 1 to 30 minutes.

  When the above-mentioned “Circus Deposit MLB 211”, “Circus Deposit MLB 213” and “Circus Deposit MLB 216” are used as a roughening solution as a set, the roughening treatment can be performed as follows, for example. it can. First, the laminated board after the lamination molding is immersed in “Circusposit MLB211” to swell the resin, then the above laminated board is immersed in “Circuposit MLB213” to dissolve the resin, and finally the above laminated board is It is immersed in “Circuposit MLB216” to neutralize the basic condition. In this way, the roughening treatment with the above three kinds of roughening liquids can be performed.

  Then, the multilayer printed wiring board 5 can be obtained by forming the plating conductor layer 4 which can become an outer layer circuit by the well-known additive method on the surface of the insulating layer 3 roughened as described above. The additive method includes a full additive method and a semi-additive method. In the present invention, any method may be used to form the plated conductor layer 4. Hereinafter, an example in which the plated conductor layer 4 is formed by the semi-additive method will be described.

  First, a through hole or a non-through hole (both not shown) for forming a through hole or a blind via hole is formed in the insulating layer 3 after the roughening process by a drill, a laser, or the like. Next, after performing electroless plating treatment to form electroless plating such as electroless copper plating on the surface of the insulating layer 3, a plating resist (not shown) is formed in a portion where the plated conductor layer 4 is not formed. Thereafter, electrolytic plating treatment is performed to form electrolytic plating such as electrolytic copper plating on a portion where the plating resist is not formed, and then the plating resist is peeled off. And the multilayer printed wiring board 5 in which the plating conductor layer 4 was formed as an outer layer circuit can be obtained by removing the electroless plating exposed by peeling of the plating resist by a quick etching method (flash etching). Through holes and blinds that electrically connect the conductor layer 40 that is the inner layer circuit and the plated conductor layer 4 that is the outer layer circuit by forming electroless plating and electrolytic plating on the inner surface of the through hole and the non-through hole. A via hole (both not shown) is formed. In addition, you may perform an after cure suitably.

  In the multilayer printed wiring board 5 obtained as described above, the following effects can be obtained. That is, when the insulating layer 3 of the multilayer printed wiring board 5 is formed using the prepreg 1 described above, the cured product layer 32 of the second resin layer B constituting the insulating layer 3 has a surface roughness compared by roughening treatment. It is easy to make small uneven surface. Therefore, when the plated conductor layer 4 is formed on the surface of the cured product layer 32 by an additive method, the cured product layer 32 can be highly adhered to the plated conductor layer 4. In addition, the coefficient of thermal expansion can be reduced at the same time by the cured product 31 of the first resin layer A constituting the insulating layer 3. Thus, when manufacturing the multilayer printed wiring board 5, if the above prepregs 1 are used, a low coefficient of thermal expansion can be realized and a suitable surface roughness can be obtained, and adhesion to the conductor layer can be achieved. It is possible to form the insulating layer 3 with increased resistance.

  Hereinafter, the present invention will be specifically described by way of examples.

<Examples 1-9 and Comparative Examples 1-4>
(First resin composition)
The first resin layer A is formed by blending a thermosetting resin A1, a curing agent, an inorganic filler, and a curing accelerator, and further diluting with methyl ethyl ketone (MEK) according to the blending composition shown in Table 1 and Table 2. A varnish (solid content 74% by mass) of the first resin composition was prepared. The following materials were used as each material.

(Thermosetting resin A1): “Epiclon HPC9500P” manufactured by DIC Corporation (Naphthalene skeleton type epoxy resin, epoxy equivalent 153 g / eq)
(Curing agent): “TD2090” manufactured by DIC Corporation (phenol curing agent)
(Inorganic filler): “SO-C2” manufactured by Admatechs Co., Ltd. (spherical silica, average particle size 0.5 μm)
(Curing accelerator): “2E4MZ” (imidazole catalyst) manufactured by Shikoku Kasei Kogyo Co., Ltd.
(Second resin composition)
By blending the thermosetting resin B1, the thermosetting resin B2, the curing agent, the inorganic filler, and the curing accelerator according to the composition shown in Tables 1 and 2, the second resin layer B is diluted with MEK. The varnish (solid content 62.5 mass%) of the 2nd resin composition for forming was prepared. However, about the comparative example 3, by mix | blending thermosetting resin B1, thermosetting resin B2, a hardening | curing agent, an inorganic filler, a hardening accelerator by the compounding composition shown in Table 3, and also diluting with MEK, A varnish (solid content: 62.5% by mass) of the second resin composition was prepared. The following materials were used as each material.

(Thermosetting resin B1): “Epiclon N690-75M” manufactured by DIC Corporation (cresol novolac type epoxy resin, epoxy equivalent 225 g / eq, about 12 epoxy groups in one molecule)
(Thermosetting resin B2): “Epiclon 850S” manufactured by DIC Corporation (bisphenol A type epoxy resin, epoxy equivalent 188 g / eq, number of epoxy groups 2 in one molecule)
(Curing agent): “LA3018-50P” (novolac type phenolic resin) manufactured by DIC Corporation
(Inorganic filler): “SO-C2” manufactured by Admatechs Co., Ltd. (spherical silica, average particle size 0.5 μm)
(Curing accelerator): “2E4MZ” (imidazole catalyst) manufactured by Shikoku Kasei Kogyo Co., Ltd.
(Prepreg)
About the prepreg of Examples 1-9 and Comparative Example 4, it manufactured as follows.

  First, the first resin composition was impregnated in the fiber base material 2, and this was heat-dried until it became a semi-cured state, whereby the first resin layer A was formed. As the fiber substrate 2, for Examples 1 to 3, 5 to 9 and Comparative Example 4, "1017-1070-AS890MSW" manufactured by Asahi Kasei E-Materials Co., Ltd. was used, and for Example 4, Asahi Kasei E-Materials was used. “1000-1070-AS890TFD” manufactured by Co., Ltd. was used.

  Next, the second resin composition B is applied to one side of the first resin layer A formed as described above, and the second resin layer B is formed by heating and drying until a semi-cured state is obtained. A prepreg 1 as shown in FIG.

  For the prepregs of Comparative Examples 1 and 2, the first resin composition was impregnated in the same fiber base material 2 (“1017-1070-AS890MSW” manufactured by Asahi Kasei E-Materials Co., Ltd.), It was manufactured by heating to dryness.

  For the prepreg of Comparative Example 3, the second resin composition was impregnated into the same fiber base material 2 (“1017-1070-AS890MSW” manufactured by Asahi Kasei E-Materials Co., Ltd.) until it was in a semi-cured state. It was manufactured by heat drying.

(Multilayer printed wiring board)
First, the first resin layer A of the prepreg 1 is overlaid on the surface of an inner layer circuit board 50 (“R-1566” manufactured by Panasonic Corporation) in which a conductor layer 40 that can be an inner layer circuit is formed on the outer surface in advance, and a protective film is further formed. After superposition, lamination molding (temperature 150 ° C., pressure 0.4 MPa) was performed using a multistage vacuum press. And the protective film was peeled and removed, it hardened | cured on 170 degreeC * 30 minute conditions in oven, and the roughening process of the insulating layer by the roughening liquid was performed.

  Said roughening process was performed in order of following (1)-(3).

  (1) The laminated board after lamination molding was immersed in a solution of “Circuposit MLB211” manufactured by Rohm and Haas for 6 minutes at 80 ° C.

  (2) Next, it was immersed for 10 minutes at 80 ° C. in a solution of “Circuposit MLB213” manufactured by Rohm and Haas.

  (3) Finally, it was immersed for 5 minutes at 45 ° C. in a solution of “Circuposit MLB216” manufactured by Rohm and Haas.

  Then, the plating conductor layer 4 was formed as an outer layer circuit on the surface of the roughened insulating layer 3 (in the first to ninth embodiments, the cured layer 32 of the second resin layer B) using a semi-additive method. That is, after electroless copper plating treatment was performed to form electroless copper plating on the surface of the insulating layer 3, it was dried at 120 ° C. for 60 minutes to form a plating resist in a portion where no circuit was formed. Furthermore, after performing the electrolytic copper plating treatment, the plating resist was peeled off, and the electroless plating was removed by flash etching. The thickness of the plating conductor layer 4 formed by electroless copper plating and electrolytic copper plating was 20 ± 2 μm, and the width of the plating conductor layer 4 was 10 mm.

  After forming the plating conductor layer 4, the multilayer printed wiring board 5 was obtained by performing after-curing on 180 degreeC x 60 minute conditions with a dryer.

<Coefficient of thermal expansion (CTE)>
About the multilayer printed wiring board 5, the thermal expansion coefficient of the direction perpendicular | vertical to the plate | board thickness direction in the temperature range (50-100 degreeC) below a glass transition temperature (Tg) was measured by the tension mode of TMA method (Thermo-mechanicalanalysis).

<Surface roughness>
Using an Olympus laser microscope “OLS3000”, the arithmetic average roughness (Ra) and ten-point average roughness (Rz) of the surface of the insulating layer 3 after the roughening treatment were measured under the following conditions.

・ Semiconductor laser: wavelength 408nm
・ Measurement pitch: 0.1 μm
・ Measurement range: 0.012 mm ² (plane)
<Adhesion>
In order to evaluate adhesion, the plating peel strength of the plating conductor layer 4 (copper plating width 10 mm) of the multilayer printed wiring board 5 was measured according to a 90-degree peel test method (JIS C6481).

  The above results are shown in Tables 1 to 3.

ＣＴＥは１０．０ｐｐｍ／℃以下、算術平均粗さ（Ｒａ）は０．２μｍ以下、十点平均粗さ（Ｒｚ）は２．７μｍ以下、めっきピール強度は０．７ｋＮ／ｍ以上であることが好ましく、実施例１〜９ではこれらの数値範囲が全て満たされている。

CTE is 10.0 ppm / ° C. or less, arithmetic average roughness (Ra) is 0.2 μm or less, ten-point average roughness (Rz) is 2.7 μm or less, and plating peel strength is 0.7 kN / m or more. Preferably, in Examples 1 to 9, all of these numerical ranges are satisfied.

  On the other hand, in the comparative example 1, since the 2nd resin layer B is not formed, surface roughness is high and adhesiveness is also bad.

  In Comparative Example 2, since the inorganic filler is highly filled as compared with Comparative Example 1, although the CTE is small, since the second resin layer B is not formed, the surface roughness is high and the adhesion is poor. .

  In Comparative Example 3, a second resin composition is used, and this second resin composition contains a resin component having excellent adhesion, but additionally contains a large amount of an inorganic filler. Has been. Therefore, although CTE becomes small, the highly filled inorganic filler interferes with the characteristics of the resin component, resulting in poor adhesion.

  Moreover, in the comparative example 4, since the thickness of the 1st resin layer A and the thickness of the 2nd resin layer B are the same, CTE is large.

DESCRIPTION OF SYMBOLS 1 Prepreg 2 Insulating base material 3 Insulating layer 4 Plating conductor layer 5 Multilayer printed wiring board 32 Hardened | cured material layer A 1st resin layer A
B Second resin layer B

Claims (6)

A first resin layer A containing a fiber substrate;
A second resin layer B formed on at least one surface of the first resin layer A without including a fiber substrate;
With
Said 1st resin layer A contains 100-400 mass parts inorganic filler with respect to 100 mass parts of resin components,
Said 2nd resin layer B does not contain an inorganic filler, or contains 50 mass parts or less of an inorganic filler with respect to 100 mass parts of resin components,
The resin component of the second resin layer B includes a thermosetting resin B1 having a functional group equivalent of 150 to 400 g / eq, a thermosetting resin B2 having a functional group equivalent of 450 to 600 g / eq, and a curing agent. Contains,
The thickness of said 2nd resin layer B is 1/2 or less of the thickness of said 1st resin layer A, The prepreg characterized by the above-mentioned. The thickness of the first resin layer A is 15 μm or more,
The prepreg according to claim 1, wherein the thickness of the second resin layer B is 5 to 15 μm. The thermosetting resin B1 is an epoxy resin having an epoxy equivalent of 150 to 400 g / eq,
The prepreg according to claim 1 or 2, wherein the thermosetting resin B2 is an epoxy resin having an epoxy equivalent of 450 to 600 g / eq. The thermosetting resin B1 is a polyfunctional epoxy resin having three or more epoxy groups in one molecule,
The prepreg according to claim 3, wherein the thermosetting resin B2 is an epoxy resin having 2 to 2.3 epoxy groups in one molecule. The content ratio of the thermosetting resin B1 and the thermosetting resin B2 is such that the mass ratio of the thermosetting resin B2 to the thermosetting resin B1 is (B2) / (B1) = 4.2-9. The prepreg according to claim 1, wherein the prepreg is zero. A cured product of the prepreg according to any one of claims 1 to 5 is provided as an insulating layer,
A multilayer printed wiring board, wherein the surface of the cured product layer of the second resin layer B is roughened and a plated conductor layer is formed thereon.

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