JP2002261442A - Method of manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing multilayer printed wiring board by which the occurrence of recesses on an IVH when the conventional resin-bonded copper foil is used in the build-up method can be eliminated and the smoothness of a core IVH is improved. SOLUTION: This method of manufacturing multilayer printed wiring board includes a step (1) of preparing a thermosetting resin composition in which an electrical insulating filler is scattered, a step (2) of applying the resin composition to one surface of metal foil having a thickness of 18-105 μm, and a step (3) of forming adhesive-bonded metallic foil by half-curing the resin composition by heating. This method also includes a step (4) of laminating the adhesive- bonded metal foil upon an internal-layer circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board using an adhesive film or a metal foil with an adhesive excellent in corrosion resistance, and more particularly, to a core interstitial via hole (hereinafter referred to as "core IVH"). The present invention relates to a method for producing a multilayer printed board having improved smoothness.

[0002]

2. Description of the Related Art Conventionally, a multilayer printed wiring board is formed by laminating one or more prepreg sheets obtained by impregnating a glass cloth base material with an epoxy resin and semi-curing on an inner circuit board on which a circuit is formed, and furthermore, copper It is manufactured through a process of laminating foils and integrally forming these multilayer laminates by heating using a hot press. However, in this method, it is difficult to make the interlayer thickness extremely thin, and it is difficult to satisfy the requirement for smoothing the surface because the glass cloth has irregularities. Further, when forming the multilayer laminate, it is necessary to fill the holes of the IVH with a hole-filling agent in order to secure the reliability of the core IVH connecting the layers and improve the wiring density. However, when a filling agent is used, three steps of coating, drying and polishing are further required, and there are problems such as a decrease in yield and an increase in processing cost.

In recent years, as a method of solving these problems, a method of manufacturing a multilayer printed wiring board by a build-up method without using glass cloth as an interlayer insulating material has been attracting attention. Above all, a build-up system in which a via is provided by a laser or plasma using a copper foil with a resin and the copper foil as a conformal mask has begun to be frequently used.

In the build-up method, as a method of filling a via, there is a method of filling with a hole filling agent or a conductive paste, or a method of filling a resin of a copper foil with a resin into a hole at the time of hot pressing. In the former, after filling the filling material, it is necessary to polish and remove the filling material protruding around the via, which causes a problem of increasing the number of steps and decreasing the yield. On the other hand, the latter has the advantage that the entire resin flows into the via, so that the filling property is excellent. However, dents are easily formed on the core IVH due to shrinkage when the resin is solidified, and when a wiring pattern is formed on a layer thereabove, there is a possibility that an etching defect may occur.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a multi-layer print with improved core IVH smoothness which can solve the problem of dents on the IVH when a conventional resin-coated copper foil is used in a build-up system. An object of the present invention is to provide a method for manufacturing a wiring board.

[0006]

Means for Solving the Problems For such a purpose,
The present inventors have conducted intensive studies, and as a result, utilizing the thickness of the copper foil and the rigidity of the filler mixed with the resin, controlling the thickness of the entire resin at the time of lamination, the core IVH
It has been found that the problem of the upper dent can be solved. For example, when the rigidity is not sufficient, such as when the thickness of the copper foil is small, it is not possible to suppress local resin inflow during hot pressing. However, if the copper foil is made thicker and the rigidity of the filler is used, such local resin inflow can be suppressed, and the resin can be made uniform by uniformly flowing the entire resin into the via. Become.

That is, the present invention provides (1) a step of preparing a thermosetting resin composition in which an electrically insulating filler is dispersed, and (2) a step of preparing the prepared resin composition by using a resin composition having a thickness of 18 to 10.
A step of applying a metal foil of 5 μm on one side, (3) a step of heating the applied resin composition to form a metal foil with an adhesive, and (4) a step of applying the metal foil with an adhesive to an inner circuit board. Laminating and forming a laminated board.

The present invention also provides (1) a step of preparing a thermosetting resin composition in which an electrically insulating filler is dispersed;
(2) The resin composition prepared above is coated with a thickness of 18 to 105 μm.
and (3) heating the metal foil with a carrier coated with the resin composition to form a metal foil with a carrier having an adhesive layer. (4) laminating the adhesive layer on an inner circuit board to form a laminate; and (5) removing the carrier film from the laminated metal foil with a carrier to expose the metal foil. And a step of producing a multilayer printed wiring board.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of manufacturing a multilayer printed wiring board according to the present invention, first, a thermosetting resin in which an electric insulating filler is dispersed is prepared, and then this resin is applied to one surface of a metal foil. At this time, a known method such as a knife coating method can be used for application. Next, the applied resin composition is heated at, for example, 150 ° C. for 10 minutes, and then dried to form a B-stage semi-cured metal foil with an adhesive. Next, this adhesive surface is superimposed on one or both surfaces of the inner layer circuit board, for example, at 175 ° C. for 60 minutes.
The multi-layer printed wiring board is formed by pressing with a pressure of 3 MPa.

In addition, a metal foil with a carrier can be used in place of the above metal foil. In this case, the metal foil with a carrier that has been semi-cured is laminated on an inner circuit board, and then the carrier film is removed. There is a need.

According to the method of the present invention, instead of etching a metal foil surface of a multilayer printed wiring board integrally formed by the above-described method to form a conductor pattern, the metal foil of the laminate is removed and a new adhesive layer surface is formed. The conductor pattern can also be formed by forming a metal plating on the substrate. Such an additive method is advantageous for forming a fine pattern.

The electrically insulating filler used in the present invention is a ceramic filler. Filler is fibrous, spherical,
A filler having a shape such as a scaly shape or an amorphous shape can be used, but a fibrous filler is preferable in view of film formability. As the filler, a filler having one or more types selected from these shapes can be used.

The average diameter of the filler is preferably from 0.3 to 3.0 μm, more preferably from 0.3 to 1.0 μm, from the viewpoint of imparting rigidity and the smoothness of the surface. preferable. The average particle length of the filler is 100 μm
Or less, more preferably 50 μm or less. As the filler, a filler manufactured in advance according to a target particle diameter can be used. Further, a filler whose particle size is adjusted by using a general pulverizing apparatus to which a shearing force can be applied, for example, a ball mill, a bead mill, a nano maker, a nanomizer, or the like can be used.

The whiskers used as fillers include silicic acid, aluminum borate, wollastonite,
Potassium titanate, magnesium sulfate, magnesium oxide, silicon nitride, aluminum hydroxide, α-alumina,
One or more fillers selected from talc and synthetic mica synthesized from alumina and fluorosilicic acid can be used. Among them, aluminum borate is more preferable because of its low coefficient of thermal expansion and relatively low cost.

The filler whose surface is treated with a coupling agent is excellent in wettability and bonding property with resin, so that the rigidity and heat resistance of the printed wiring board can be further increased. As the coupling agent used for such a purpose, known compounds such as silicon-based, titanium-based, aluminum-based, zirconium-based, zirconaluminum-based, chromium-based, boron-based, phosphorus-based, and amino acid-based can be used. .

The thermosetting resin used in the present invention may be a thermosetting resin used for a conventional prepreg based on a glass cloth, an adhesive film or a copper used for a prepreg containing no glass cloth base. The thermosetting resin used for the adhesive film with a foil can be used.

That is, as the thermosetting resin, epoxy resin, bistriazine resin, polyimide resin, phenol resin, melamine resin, silicon resin, unsaturated polyester resin, cyanate ester resin, isocyanate resin,
A polyimide resin or various modified resins thereof can be used. Among them, epoxy resin or bistriazine resin is preferable from the viewpoint of the characteristics of the printed wiring board.

As the epoxy resin, bisphenol A
Epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, bisphenol A novolak epoxy resin, salicylaldehyde novolak epoxy resin, bisphenol F novolak epoxy resin, fat Cyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic cyclic epoxy resin, or halide or hydride of these resins can be used. . Among them, bisphenol A novolak type epoxy resin or salicylaldehyde novolak type epoxy resin is more preferable because of its excellent heat resistance. These resins can be used alone or in combination of two or more.

The thermosetting resin used in the present invention is preferably used in combination with a resin curing agent. As the curing agent for the thermosetting resin, a known curing agent that has been conventionally used can be used. In the case of an epoxy resin, for example, dicyandiamide, bisphenol A, bisphenol F,
Polyvinyl phenol, phenol novolak resin, bisphenol A novolak resin, or a halide or hydride of these phenol resins can be used. Above all, bisphenol A novolak resin is preferred because of its excellent heat resistance. The mixing ratio of the resin curing agent to the thermosetting resin is preferably 2 to 80 parts by weight based on 100 parts by weight of the thermosetting resin. When the curing agent is dicyandiamide, the amount is preferably 2 to 5 parts by weight, and when the other curing agent is used, the amount is preferably 20 to 70 parts by weight.

Further, the thermosetting resin of the present invention can also use a curing accelerator. In the case of an epoxy resin, for example, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, or the like can be used as the curing accelerator. The mixing ratio of the curing accelerator to the thermosetting resin is preferably from 0.01 to 20 parts by weight, and more preferably from 0.1 to 20 parts by weight, based on 100 parts by weight of the thermosetting resin.
1.0 parts by weight is more preferred.

The thermosetting resin of the present invention can be diluted with a solvent and used as a resin varnish. Solvents used for this purpose 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. The compounding ratio of the diluent to the thermosetting resin can be a compounding ratio conventionally used, and is preferably 1 to 200 parts by weight, more preferably 30 to 100 parts by weight, based on 100 parts by weight of the thermosetting resin. More preferred.

In the present invention, in addition to the above-described composition, a known coupling agent, a filler, and the like can be appropriately compounded, if necessary.

The compounding amount of the electrically insulating filler is preferably 5 to 350 parts by weight based on 100 parts by weight of the resin solid content such as a thermosetting resin, a resin curing agent, and a curing accelerator. In this range, there is no problem in handling such that the resin is finely crushed and easily scattered at the time of cutting, so that sufficient heat radiation can be obtained when the wiring board is used. Also,
Filling of the inner layer circuit and filling of the resin between the circuits are good when molding by hot pressing, and voids or fainting are contained in the resin composition layer in which the filler is compounded after hot pressing. Therefore, the characteristics of the wiring board are excellent. When the filler is blended in an amount of 100 to 230 parts by weight with respect to 100 parts by weight of the resin solid content,
Better filling of the inner layer circuit and filling of resin between circuits are more excellent. For this reason, it is possible to manufacture a wiring board having stiffness, dimensional stability, and wire bonding properties equal to or higher than those of a wiring board manufactured using a prepreg using a conventional glass cloth.

The thickness of the resin composition containing the electrically insulating filler is preferably 5 to 30 μm per layer. When a fibrous filler having a short average fiber length is used, the thickness of the resin composition is preferably 5 to 10 μm, which is thinner.
Further, by repeatedly applying and drying a resin composition containing an electrically insulating filler, an insulating layer having a desired thickness can be obtained.

The metal foil of the present invention may be a copper foil, a stainless steel foil,
Alternatively, a nickel foil or the like can be used, but a copper foil is preferable in terms of conductivity. As the copper foil, an electrolytic copper foil or a rolled copper foil can be used, but it is preferable to perform a roughening treatment on the bonding surface in order to increase the bonding strength to the insulating resin.

The thickness of the metal foil ranges from 18 to 105 μm. In this range, the metal foil can hold the resin, and its rigidity can prevent local inflow of the resin, so that the depression on the core IVH can be minimized. In order to make the dent smaller, a thickness of 35
~ 105 μm is preferred. On the other hand, in the case of the metal foil with a carrier, the thickness is not limited thereto, and the carrier foil is preferably 18 μm or more, more preferably 35 μm or more. Within this range, the thin line can be easily etched.

When it is necessary to form a fine line pattern on the metal foil used in the present invention, a low profile Rz of 2 to 5 μm is required as compared with a normal foil having a roughened surface of the metal foil having a surface roughness Rz of 5 μm or more. Foil is preferred.

[0028]

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Example 1 A thermosetting resin composition containing an electrically insulating whisker was prepared by the following method. Bisphenol A novolak type epoxy resin 1 having an epoxy equivalent of 210 as a thermosetting resin
100 parts by weight and 100 parts by weight of a bisphenol A novolak resin having an epoxy equivalent of 123, and as a resin curing agent,
1 part by weight of dicyandiamide is added to methyl ethyl ketone (M
EK) was diluted with 80 parts by weight to prepare a thermosetting resin varnish. Next, an aluminum borate whisker having an average diameter of 0.8 μm, an average fiber length of 8 μm, and a maximum fiber length of 12 μm was added to the varnish in an amount of 1 part per 100 parts by weight of the resin solid content.
10 parts by weight were mixed and stirred until the filler was uniformly dispersed in the varnish.

The varnish was applied to a low-profile copper foil having a thickness of 35 μm using a knife coater,
The resultant was dried by heating at 0 ° C. for 10 minutes to remove the solvent and semi-cured the thermosetting resin. Thereby, a copper foil with an adhesive having a thickness of 60 μm and a whisker volume fraction of 30% was produced. The resin flow at this time was 25% as measured by the MIL method.

Here, the resin flow refers to the amount of resin that exudes due to pressure when the resin is melted by heating.
The MIL method is a method defined in the U.S. MIL standard, and is a method in which three to four resin-coated copper foils are superposed and tested.

Then, both sides of an inner layer plate provided with a 0.3 mmφ core IVH were coated with a 60 μm-thick copper foil with an adhesive by the above method so that the hole density was 300,000 holes / m ^2. Were laminated so that the adhesive surface was in contact with the inner layer plate, and heated and pressed at 175 ° C. under a load of 3 MPa for 60 minutes to integrally form a multilayer printed wiring board. Then, the pattern used as the electrode for an electrolytic corrosion test was etched on the copper foil surface.

Example 2 The procedure of Example 2 was repeated except that 100 parts by weight of salicylaldehyde novolak type epoxy resin having an epoxy equivalent of 250 and 200 parts by weight of a resin mainly composed of bisphenol A novolak resin having an epoxy equivalent of 123 were used as the thermosetting resin. A varnish was prepared in the same manner as in Example 1. Using a knife coater, this varnish is applied to a foil surface of a low-profile copper foil having a thickness of 5 μm with a carrier having a thickness of 35 μm, and heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent. The thermosetting resin was semi-cured to form a copper foil with a carrier having a thickness of 65 μm and having an adhesive layer. Next, both surfaces of the inner layer plate provided with the same core IVH as in Example 1 were coated with a carrier-provided copper foil provided with an adhesive layer having a thickness of 65 μm by the above-described method. Laminated so that they touch each other, at 175 ° C under a load of 3 MPa, 60
By heating and pressurizing for minutes, a multilayer printed wiring board was integrally formed. Thereafter, the carrier film was removed, and a pattern serving as an electrode for an electrolytic corrosion test was etched on the exposed copper foil surface.

Example 3 A multilayer printed wiring board was produced in the same manner as in Example 1, except that a silicate glass filler of fibrous particles having an average diameter of 1 μm and an average fiber length of 70 μm was used.

Example 4 A multilayer printed wiring board was produced in the same manner as in Example 1 except that a synthetic mica filler synthesized from flaky alumina having an average particle diameter of 10 μm and fluorinated silicic acid was used.

Comparative Example 1 Average diameter 1 μm, average fiber length 30 μm, maximum fiber length 50 μm
m aluminum borate filler, thickness 12μm
Except that the usual copper foil was used,
A multilayer printed wiring board was manufactured.

Comparative Example 2 In the same manner as in Example 1 except that a prepreg having a thickness of 60 μm obtained by impregnating and drying the resin composition of Example 1 in a glass cloth was used instead of the copper foil with an adhesive, A multilayer printed wiring board was manufactured.

With respect to the multilayer printed wiring board obtained by these methods, the filling property of the core IVH, the amount of depression on the surface (surface step) and the corrosion resistance were investigated. Table 1 shows the characteristic values of Examples 1 to 4 and Comparative Examples 1 and 2.

[0039]

[Table 1]

The test method carried out here is as follows. The surface roughness is defined as R _MAX specified in JISB0601.
Was measured as a reference length of 2.5 mm. The corrosion resistance is 8
At 5 ° C., 85% RH and DC 50 V, the adhesive layer having an insulation resistance value of not less than 10 ⁹ Ω for 500 hours or more was evaluated as ○. In addition, the core IVH filling property was checked at a magnification of 300 times by using a stereoscopic microscope after polishing the cross section after heat compression.

As is clear from Table 1, Examples 1 to 4 according to the present invention are excellent in the filling property of the core IVH and the electric corrosion resistance after 500 hours, and the dents on the IVH are also 2-3.
It is suppressed to within μm. On the other hand, in Example 1 using a copper foil having a thickness outside the range of the present invention, the dent on the IVH was 8%.
μm. In Example 2 using a glass cloth prepreg, the filling property of the core IVH was 500
Both the corrosion resistance after time and the depression on the IVH are insufficient values.

[0042]

According to the present invention, a resin composition containing a thermosetting resin in which an electric insulating filler is dispersed is applied to one surface of a copper foil, heated and semi-cured, and this process is repeated. The method of manufacturing a multilayer printed wiring board in which a layered insulating layer having a desired thickness is formed and laminated on an inner layer circuit board has excellent circuit filling properties, a flat surface, and good circuit workability.
High insulation reliability. In addition, since it can be manufactured using existing equipment, it does not impose a greater burden on the environment than ever. Therefore, the present invention has the effect of greatly contributing to higher density, thinner, higher reliability, and lower cost of the multilayer printed wiring board.

Claims (4)

[Claims] (1) a step of preparing a thermosetting resin composition in which an electrically insulating filler is dispersed; and (2) applying the prepared resin composition to one surface of a metal foil having a thickness of 18 to 105 μm. A step of applying; (3) a step of heating the applied resin composition to form a metal foil with an adhesive; and (4) a step of laminating the metal foil with an adhesive on an inner circuit board to form a laminate. A method of manufacturing a multilayer printed wiring board. 2. A step of (1) preparing a thermosetting resin composition in which an electrically insulating filler is dispersed; and (2) providing the prepared resin composition with a metal foil having a thickness of 18 to 105 μm. A step of applying to the foil surface of the metal foil with a carrier,
(3) heating the metal foil with a carrier to which the resin composition has been applied to form a metal foil with a carrier having an adhesive layer; and (4) laminating the adhesive layer on an inner circuit board, and laminating. A method of manufacturing a multilayer printed wiring board, comprising: a step of forming a board; and (5) a step of removing a carrier film from the laminated metal foil with a carrier to expose the metal foil. 3. The method according to claim 1, further comprising the steps of: removing a metal foil from the laminate; and forming a conductive pattern by metal plating on the surface of the adhesive layer from which the metal foil has been removed. A method for manufacturing the multilayer printed wiring board according to the above. 4. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said electrically insulating filler is aluminum borate.