Method for manufacturing multilayer wiring board

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a method for manufacturing a multilayer wiring board.

【0002】

[Conventional technology]

In recent years, the density and thickness of multilayer wiring boards have been increasing, and a method for manufacturing a multilayer wiring board that does not use a glass cloth has been studied, and a so-called interstitial via hole that connects only adjacent wiring layers is formed. The method is being considered. As such an example, a base material made of an insulating adhesive layer and a copper foil with holes for interlayer connection in advance is laminated on an inner layer circuit board, and the circuit on the inner layer circuit board and the copper foil of the base material are electrically connected. There are known ways to connect to.

【0003】

Further, Japanese Patent Application Laid-Open No. 2-62095 describes a method in which an adhesive sheet having almost no resin flow is attached to a copper foil having a reinforcing material, and after making a hole, it is laminated on an inner layer plate on which a circuit is formed to form an IVH. It is described that, as an effect, NC hole processing can be performed without causing wrinkles and tears in the copper foil.

【0004】

[Problems to be Solved by the Invention]

By the way, a method in which a base material made of an insulating adhesive layer and a copper foil with holes for interlayer connection in advance is laminated on an inner layer circuit board, and the circuit on the inner layer circuit board and the copper foil of the base material are electrically connected. Then, if the fluidity of the insulating adhesive layer is increased, the conductors of the inner layer circuit can be filled, and the insulating characteristics between the circuits are improved, but the problem is that the insulation characteristics may flow to the interlayer connection holes and close the holes. If the fluidity of the insulating adhesive layer is reduced, the amount of resin flowing in the interlayer connection hole is reduced, but there arises a problem that the insulating characteristics between the circuits are deteriorated. In addition, the unevenness of the inner layer circuit appears on the surface layer, and the resist does not adhere to the recesses during etching resist film lamination or etching resist ink screen printing when processing the outer layer circuit, causing many defects such as circuit breakage. There is a problem that the formability of the ink is reduced. As described above, it is difficult to improve the circuit filling property and the interlayer connection reliability at the same time.

【0005】

Therefore, the present inventors have proposed by Japanese Patent Application No. 6-16504 to laminate and bond using a cushioning material that becomes fluid by heating, but the copper foil and the insulating adhesive layer are proposed. It was found that there is a drawback that the unevenness of the surface becomes large because the followability to the inner layer copper foil circuit is improved. In particular, it was difficult when the inner layer copper foil was thick or when the interlayer connection hole diameter was small. Further, when a thin copper foil is used for the outer layer circuit, since the rigidity of the copper foil is small, the copper foil is stretched at the time of laminating, so that it is easy to follow the inner layer copper foil circuit and the surface unevenness is likely to be large. It turned out that it was difficult to obtain sufficient surface smoothness.

【0006】

Further, in the method described in JP-A-2-62095, it is necessary to use an adhesive sheet having almost no resin flow, and there are problems that the filling property of the inner layer circuit is not sufficient and voids and the like are likely to occur. there were.

【0007】

The present invention is a method for manufacturing a multilayer wiring board that does not use a glass cloth, and an object of the present invention is to provide a method for manufacturing a multilayer wiring board that can simultaneously satisfy interlayer connection reliability and surface smoothness. is there.

【0008】

[Means for solving problems]

The method for manufacturing a multilayer wiring board of the present invention is A film in which an insulating adhesive layer with relatively high fluidity is formed on one surface of a copper foil, and a sheet-like reinforcing material made of a metal or organic material that can be removed by peeling, etching, etc. is formed on the other surface. The process of drilling holes in the shape material in place b. On the inner layer circuit board, the film-like material with the above holes is layered so that the circuit board and the insulating adhesive layer are in contact with each other, and further, a cushioning material that becomes fluid by heating is layered on the inner layer circuit board. The process of heating and pressurizing and laminating and integrating c. Process of removing sheet-like reinforcing material d. A step of electrically connecting the circuit on the inner layer circuit board and the copper foil of the film-like material through the holes provided in the film-like material from which the sheet-like reinforcing material has been removed. e. The process of processing copper foil, which is a film-like material, to form a circuit It is characterized by having.

【0009】

This film-like material can also be produced by laminating a copper foil obtained by applying an insulating adhesive material to a copper foil and a metal sheet or an organic material sheet, or forming a metal sheet or an organic material sheet on the copper foil. It can also be manufactured by applying an insulating adhesive material to the copper foil side of the product.

【0010】

As the sheet-like reinforcing material, a metal foil or an organic material sheet having a high elasticity at high temperature can be used, and as the metal foil, a metal foil such as copper or aluminum, and an adhesive or the like are applied thereto. Examples thereof include those manufactured by plating dissimilar metals on copper foil. For example, it is described in peelable electrolytic copper foil (manufactured by Furukawa Circuit Foil Co., Ltd., trade name) composed of aluminum foil and copper foil, Japanese Patent Application Laid-Open No. 5-206599, etc., and its surface has a roughness suitable for adhesion to a resin. A first copper layer serving as a circuit having a structure, a second copper layer having sufficient strength as a metal layer as a whole, and a thickness of 0.04 to provided between the first copper layer and the second copper layer. There is CCT foil (manufactured by Hitachi Kasei Kogyo Co., Ltd., trade name), which is a metal foil for printed wiring boards composed of a 1.5 μm nickel-phosphorus alloy layer. Further, as the organic material sheet, an organic material sheet such as polyimide, polyethylene terephthalate, polypropylene, polyvinylidene chloride, polyvinylidene chloride, polytetrafluoridene, polyvinyl alcohol, polyacrylonitrile, polyamide, cellophane and the like can be used.

【0011】

As the composition of the insulating adhesive layer that can be used in the present invention, an epoxy resin-based adhesive, an acrylic-modified resin-based adhesive, a polyimide resin-based adhesive, or the like can be used. The insulating adhesive layer needs to be in the form of A stage or B stage, and the fluidity is converted into the area change rate under the condition of 170 ° C / 15MPa / 10 minutes from the state where the resin flow is applied. Therefore, it is preferable to use an adhesive material in the range of 0.2 to 5.0%. If it is less than 0.2%, it is not enough to fill the space between the conductors of the inner layer circuit, and if it exceeds 5.0%, the effect of suppressing resin bleeding by the cushion material is not sufficient, and the resin bleeding becomes large, so that the layers are layered. This is not preferable because it reduces the connection reliability. Further, if the fluidity is too large, the film thickness between the layers is greatly reduced, which is not preferable in that the insulation reliability is lowered. Examples of such an insulating adhesive material include AS-3000 (manufactured by Hitachi Kasei Kogyo Co., Ltd., trade name) and the like.

【0012】

Further, the insulating adhesive layer can be composed of two or more layers having different cured states in order to balance the circuit filling property and the amount of the adhesive oozing out. In order to form such a two-layer or more structure, a varnish is applied as the first layer of the coating film on the copper foil, and this is heat-cured to the B or C stage state, and the second layer of the coating film is formed on the varnish. This can be achieved by coating and heat-curing to the A or B stage state under conditions more lenient than the above-mentioned heat-curing. Alternatively, as the first layer of the coating film, a flexible substrate or the like or a layer containing a high molecular weight rubber, a phenoxy resin, a high molecular weight epoxy resin, a high molecular weight epoxy resin, or the like as a main component and having low fluidity is used, and a second coating film is placed on the layer. This can also be achieved by applying a layer and heat curing it to the A or B stage state. In the present invention, the A, B, and C stages indicate the degree of curing of the insulating adhesive material, and the A stage is a state in which the insulating adhesive material is almost uncured and not gelled, and the total heat generation amount of curing is 0 to 20. The B stage is a state in which the heat generation of% is completed, the B stage is a state in which the gelation has progressed slightly, and the heat generation of 20 to 60% of the total heat generation amount is completed, and the C stage is a state in which the heat generation is considerably cured. Is in a state of progress and gelation, and a state in which 60 to 100% of the total heat generation amount of curing is completed. In forming this insulating adhesive layer, there are a bar coater, a lip coater, a roll coater, etc. as a method of applying the varnish to the copper foil or the film, but there are few defects such as craters and voids, and the coating thickness is almost uniform. Any method can be used as long as it can be applied.

【0013】

Further, when an electronic component having a large calorific value is mounted, an inorganic filler such as alumina, silica, or aluminum nitride can be added to the insulating adhesive layer, and the addition amount is preferably in the range of 50% by volume or less. As the amount of this addition increases, the heat dissipation property improves, but on the other hand, the fluidity of the adhesive sheet decreases and the adhesiveness between the copper foil and the adhesive sheet decreases. Therefore, it is sufficient if the addition amount exceeds 50% by volume. It is not possible to obtain good solder heat resistance and reliability.

【0014】

Next, for drilling holes in the base material, about 1 to 40 base materials can be stacked and holes can be drilled all at once. The larger the number of stacked sheets, the better the work efficiency. However, stacking 40 or more sheets is not preferable because problems such as variation in hole diameter and generation of burrs occur. Next, the laminating and bonding method is not particularly limited, but a press, a vacuum press, or the like can be used. Further, by using the above sheet-shaped reinforcing material, there is an effect that workability in the alignment process at the time of laminating work is improved. In particular, when the copper foil is thin, workability may deteriorate due to warping of the copper foil with an insulating adhesive material, which is effective in improving this. The thickness of the sheet-like material is preferably about 10 μm to 200 μm. Further, if the thickness of these sheet-shaped reinforcing materials is less than 10 μm, the effect of surface smoothing is reduced, which is not preferable. Further, when the thickness exceeds 200 μm, the flow of the cushioning material is hindered, and as a result, the exudation of the resin is not suppressed, which is not preferable in that the amount of exudation of the resin increases. For example, when the hole diameter is 200 μm, the thickness of the sheet-shaped reinforcing material is appropriately about 50 μm.

【0015】

Further, as the cushion material used at the time of lamination, paper, rubber sheet, silicon rubber sheet, various film materials, for example, polypropylene, polyethylene, polyvinylidene chloride, and a fluorine-containing material such as polytetrafluorinated ethylene may be used. it can. Further, a plurality of papers, rubbers, various thermoplastic films and the like can be used in combination. The required thickness of the cushion material needs to be appropriately set according to the film thickness of the insulating adhesive material, the lamination temperature, the pressure, and the like.

【0016】

For interlayer connection, a method such as conductive paste, plating, soldering, or wire bonding can be used.

【0017】

[Action]

According to the method for manufacturing a multilayer wiring board of the present invention, the cushion material flows from the connection portion where the sheet-shaped reinforcing material material is perforated and closes the hole portion, so that the amount of exudation of the insulating adhesive material can be reduced. , It is possible to reduce the hole diameter for interlayer connection. In addition, since the amount of flow of the cushion material is small in the portion where the sheet-shaped reinforcing material is not perforated, the unevenness of the inner layer copper foil can be flattened with the insulating adhesive material, and the surface smoothness can be improved. did it. Further, in the present invention, the insulating adhesive material and the sheet-shaped reinforcing material can be drilled at once, and as compared with the method of drilling and then superimposing each of them, there is less misalignment and less cost required for drilling. It is preferable in that respect.

【0018】

[Example]

Example 1 (1) Apply an epoxy resin adhesive to a copper foil with a thickness of 18 μm so that the film thickness after drying is 70 μm, and dry at 130 ° C for 10 minutes to prepare a copper foil with an insulating adhesive material. The amount of resin flow of this insulating adhesive material was 0.3%. (2) A polyethylene terephthalate adhesive sheet (thickness 70 μm) is further laminated on the copper foil with an insulating adhesive material. (3) Drill a hole with a diameter of 0.2 mm at the part of the copper foil with insulating adhesive material to be interconnected. (4) As a cushioning material, a polyethylene film having a thickness of 150 μm is used on the copper foil side with an insulating adhesive material, and a perforated insulating adhesive material copper foil and a circuit board having a copper foil circuit thickness of 18 μm are added by pressing. Pressure and heat (lamination temperature 170 ° C, pressure 30kgf / cm, 1 hour) to integrate the layers. (5) Peel off the polyethylene terephthalate adhesive sheet (film thickness 70 μm). (6) Polish, clean, and pre-plat the copper foil surface. (7) Copper plating is used to connect the layers between the upper and lower circuits. (8) Unnecessary parts of the copper foil on the surface are removed by etching to form a circuit.

【0019】

Example 2 An epoxy resin adhesive was applied to a copper foil with a thickness of 18 μm as the first layer of the coating film so that the film thickness after drying would be 70 μm, and dried at 150 ° C for 10 minutes to form the second layer of the coating film. Example 1 except that an epoxy resin adhesive is applied so that the film thickness after drying is 140 μm in total for the first layer and the second layer, and the film is dried at 130 ° C for 10 minutes to prepare a copper foil with an insulating adhesive material. The wiring board was formed in the same manner as in the above. At this time, the amount of resin flowing in the second layer of the coating film was 0.3%.

【0020】

Example 3 (1) Epoxy resin-based adhesion to a peelable electrolytic copper foil (manufactured by Furukawa Circuit Foil Co., Ltd., trade name) with a thickness of 79 μm (1st layer 70 μm, 2nd layer 9 μm) so that the film thickness after drying is 70 μm. The agent is applied and dried at 130 ° C for 10 minutes to prepare a copper foil with an insulating adhesive material. The amount of resin flow of this insulating adhesive material was 0.3%. (2) Drill a hole with a diameter of 0.2 mm at the part of the copper foil with insulating adhesive material to be interconnected. (3) As a cushioning material, a polyethylene film with a thickness of 150 μm is used on the copper foil side with an insulating adhesive material, and a perforated insulating adhesive material copper foil and a circuit board with a copper foil circuit thickness of 18 μm are added by pressing. Pressure and heat (lamination temperature 170 ° C, pressure 30kgf / cm, 1 hour) to integrate the layers. (4) Peel off the first layer of copper foil. (5) Copper plating is used to connect the layers between the upper and lower circuits. (6) The unnecessary part of the copper foil on the surface is removed by etching to form a circuit.

【0021】

Example 4 (1) The thickness of the first copper layer is 5 μm, the thickness of the second copper layer is 20 μm, and the first copper layer is a circuit whose surface has a roughness suitable for adhesion to the resin. CCT foil (manufactured by Hitachi Kasei Kogyo Co., Ltd., trade name), which is a metal leaf composed of a nickel-phosphorus alloy layer with a thickness of 0.4 μm provided between the second copper layer and the second copper layer, has a thickness after drying. Apply an epoxy resin adhesive so that the thickness is 70 μm, and dry at 130 ° C for 10 minutes to prepare a copper foil with an insulating adhesive material. The amount of resin flow of this insulating adhesive material was 0.3%. (2) Drill a hole with a diameter of 0.2 mm at the part of the copper foil with insulating adhesive material to be interconnected. (3) As a cushioning material, a polyethylene film with a thickness of 150 μm is used on the copper foil side with an insulating adhesive material, and a perforated insulating adhesive material copper foil and a circuit board with a copper foil circuit thickness of 18 μm are added by pressing. Pressure and heat (lamination temperature 170 ° C, pressure 30kgf / cm, 1 hour) to integrate the layers. (4) The second copper layer is removed by an etching process. (5) The nickel-phosphorus alloy layer is removed by an alkaline etching process. (5) Copper plating is used to connect the layers between the upper and lower circuits. (6) The unnecessary part of the copper foil on the surface is removed by etching to form a circuit.

【0022】

Comparative example 1 The same as in Example 1 except that the sheet-shaped reinforcing material is not used.

【0023】

Comparative example 2 The same as in Example 3 except that the cushion material is not used.

【0024】

Comparative example 3 The same applies to Example 1 except that the sheet-shaped reinforcing material and the cushioning material are not used.

【0025】

Comparative example 4 The same as in Example 3 except that an adhesive sheet having a resin flow amount of 0.1% is used.

【0026】

Comparative example 5 The same applies to Example 3 except that an adhesive sheet having a resin flow rate of 7% is used.

【0027】

The multilayer wiring board produced as described above was evaluated as follows. The evaluation results are shown in Table 1.

【0028】

(Amount of exudation) An adhesive sheet having a hole with a diameter of 0.2 m was laminated on a circuit board, and the distance of the insulating adhesive material exuding from the hole after the lamination was measured. (Void generation) Microscopic observation was performed, and those with no voids exceeding 10 μm in diameter between the lower copper foil and the insulating adhesive material were considered good, and those with voids with a diameter of 10 μm or more were considered defective. did. (Amount of surface unevenness) The surface unevenness was measured using a surface roughness meter, and the difference in height between the convex portion and the concave portion was measured by measuring the surface unevenness amount.

【0029】

[table 1]

<img file="JPH08316632A_D0001.tif" />【0030】

[Effect of the invention]

According to the method for producing a multilayer wiring board of the present invention, the unevenness of the inner layer copper foil can be flattened with an insulating adhesive material, and the surface smoothness can be improved. It has become possible to form fine wiring that improves the circuit formability of the outer layer circuit. The size of the multi-layer wiring board has been reduced. In addition, the defective rate has been reduced. Further, although the cost of the film increases, the alignment at the time of press configuration is unnecessary, and the increase in the cost required at the time of manufacturing is small. Further, these methods increase the steps of laminating and peeling the sheet-like reinforcing material, but these can be automated and have little influence on the processing time.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing which shows the example which laminated by the conventional method.

[Figure 2]

It is sectional drawing which shows one Example of this invention.

[Fig. 3]

It is sectional drawing which shows an example of the structure at the time of stacking of this invention.