JP2003188544A - High density printed wiring board and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a high density printed wiring board which is superior in metal foil direct laser beam machining property and in reliability without largely increasing the energy of a laser. <P>SOLUTION: In the metal foil direct laser punching work of a metal foil-clad laminated board and a printed wiring board, metal foil on a surface is etched and it is thinned to not more than 7 μm. Then, a surface processing whose surface roughness of an etching system is not more than 4 μm is performed. Thus, the high density printed wiring board superior in metal foil direct laser beam machining property and reliability and the manufacturing method can be obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density printed wiring board used for electric / electronic devices and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a multilayer board used for manufacturing a printed wiring board is obtained by impregnating a base material such as glass cloth with a thermosetting resin composition such as an epoxy resin composition, followed by heating and drying to semi-cure. A prepreg is produced by stacking the required number of prepregs, and a metal foil such as a copper foil is placed on one side or both sides of the prepreg to be laminated, and heated and pressed to form a metal foil-clad laminate. . Then, the metal foil on the surface of the metal foil-clad laminate is etched to prepare an inner layer substrate having guide marks used for manufacturing a conductor circuit and a printed wiring board on the surface, and then roughening treatment is performed as necessary. Then, the required number of prepregs manufactured in the same manner as described above are stacked on the inner layer substrate on which the conductor circuits and the like are formed, and the metal foil is arranged on one side or both sides as necessary. Manufacturing is carried out by stacking and heating and pressing to form.

Further, as a method of manufacturing a printed wiring board using this multilayer board, a guide mark formed on an inner layer substrate is used, and a hole is drilled in the multilayer board by a drill machine and a laser machine based on this guide hole. After that, the wall surface of the hole formed by the drill machine and the laser machine is plated with through holes, and the outer layer metal foil is etched to form the outer layer conductor circuit.

The base material used for the production of these metal foil-clad laminates and prepregs is glass cloth woven with plain weave, and generally has a thickness of 60 to 200 μm. Further, a glass cloth that has been subjected to a fiber-opening treatment is used in order to improve impregnation properties and the like.

[0005] Multilayer printed wiring boards are moving toward higher densities, and as wiring circuits of multilayer printed wiring boards become thinner, IVH (Interstitial Via Hole) and SVH (Su).
The diameter of the hole for interlayer connection such as rfaceVia Hole) is also becoming smaller. Therefore, the diameter of the drill used for drilling has been reduced. However, due to the smaller diameter of the drill,
Hole bending, drill breakage, and shortened drill life are becoming apparent. Therefore, in the multilayer printed wiring board, a laser drilling machine excellent in small-diameter processing has been widely used.
In laser drilling, a method in which a copper foil is preliminarily etched to form a hole, and then laser drilling is performed, such as conformal and large windows, is predominant.
However, there are drawbacks such as misalignment of the inner copper foil, misalignment of the upper and lower holes, and the like, poor connection, and inability to form lands on the front and back. Therefore, metal foil direct laser processing for simultaneously punching a metal foil and an insulating layer has been adopted, and there is a method of performing blackening treatment on the surface metal foil in order to enhance absorption of laser light. However, the blackening treatment has a short treatment life, and there is a time limitation because the needle-like crystals are scratched and discolored or deteriorated when stored for a long time. Further, it has been attempted to use an ultra-thin copper foil, but the peeling strength is lowered due to the low profile, and there is a problem that the fine line pattern is peeled off. Also, when the through-hole is formed, if the surface copper foil is thick or if it is directly mounted on the laser machine and drilled, it is difficult to obtain a straight hole shape due to the heat generated during laser processing. There was a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a metal foil direct laser processability in a metal foil-clad laminate and a printed wiring board. Another object of the present invention is to provide a printed wiring board which is excellent in reliability and is compatible with high density, and a manufacturing method thereof.

[0007]

[Means for Solving the Problems] As a result of studies for solving the above problems, as a result of etching a metal foil having a general profile in metal foil direct laser drilling of metal foil-clad laminates and printed wiring boards. Down to 7 μm or less, and surface roughness of etching system is 4 μm
By performing the following surface treatment, the metal foil direct laser processability is excellent, and the peeling strength is improved to make it thinner.
We have found that it can be used for higher density. Also, in the case of through copper foil laser processability, the metal foil is similarly etched by etching.
A jig plate with a thickness of 1.0 mm or more that has been machined in advance to the lower side of the metal-clad laminate after the surface has been thinned to less than μm and the surface roughness of the etching system has been reduced to 4 μm or less. We solved the problem by finding that a straight hole shape can be obtained by inserting and then performing direct laser processing, and that the through-hole metal foil direct laser processing property is excellent.

The method for manufacturing a printed wiring board according to claim 1 of the present invention is an inner layer substrate having a conductor circuit formed on the surface by etching the metal foil of a metal foil-clad laminate, and a thickness of 20 to 20.
In order to facilitate formation of a through hole for conducting layers in a method for producing a multilayer board produced by laminating a prepreg produced by impregnating a 150 μm glass cloth with a thermosetting resin composition and then heating and pressing By etching the metal foil on the surface to thin the metal foil and applying a surface treatment that increases the absorption rate of laser light to the metal foil, it is not necessary to significantly increase the energy of laser light, and through holes can be efficiently obtained. A printed wiring board and a method for manufacturing the same.

A method of manufacturing a printed wiring board according to a second aspect of the present invention is the method of manufacturing a printed wiring board according to the first aspect, wherein the metal foil-clad laminate and the metal foil of the printed wiring board have electrodes with carriers. By using a general metal foil instead of a thin metal foil (3 to 5 μm), the material cost can be suppressed, the adhesive force with the resin can be made higher than that of the ultrathin metal foil, and peeling of the fine line pattern can be prevented. Further, it is characterized in that the metal foil direct laser hole processing can be efficiently performed by etching the surface of a general metal foil to reduce the thickness to 7 μm or less.

A method for manufacturing a printed wiring board according to claims 3 and 4 of the present invention is the method for manufacturing a printed wiring board according to claim 1, wherein after the surface of the general metal foil is thinned by etching with high accuracy in thickness, Surface roughness of 4 μm due to sulfuric acid aqueous solution, sulfuric acid / hydrogen peroxide aqueous solution, formic acid aqueous solution, etc.
By performing the following surface treatment having a rust preventive treatment film, it is possible to extend the life of the surface treatment and improve processing variations due to discoloration due to scratches and treatment deterioration. This surface treatment does not need to be black, and the laser light is diffusely reflected on the treated surface due to the unevenness of 4 μm or less on the surface, and it is easy to absorb the light, and the metal foil direct laser processing is possible. .

A method for manufacturing a printed wiring board according to a fifth aspect of the present invention is the method for manufacturing a printed wiring board according to the first aspect. CO2 laser, metal foil (copper, etc.)
It is known that YAG lasers are hardly absorbed.
Along with this, in the metal foil direct laser processing, it is necessary to increase the number of shots or set the energy of laser light to be higher than that in the conformal laser processing.
Therefore, the high-density printed wiring board is thermally affected by the irradiation of laser light. Therefore, the glass transition temperature is 160 ° C.
The above thermosetting resin composition is used, and in some cases, an appropriate amount of an inorganic filler is mixed, whereby thermal deterioration around the hole, heat resistance and connection reliability can be improved.

A method for manufacturing a printed wiring board according to claim 6 of the present invention is the method for manufacturing a printed wiring board according to claim 1, wherein in order to obtain a straight through hole by copper foil direct laser processing, a laser is used. With optimization of machine conditions, it is important to reduce heat generated by reflection of laser light and heat accumulated in the bottom portion of the substrate. Therefore, the thickness of the metal foil on the surface should first be 7μ.
When the thickness is less than or equal to m, the bottom side metal foil is likely to be pierced, and the heat generated by reflection is accumulated by inserting the backing plate with the laser-processed part preliminarily bored into the lower side of the printed wiring board. It is characterized by being able to release heat.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A printed wiring board according to the present invention is
A plain weave glass cloth having a thickness of 20 to 150 μm is impregnated with a thermosetting resin composition, laminated with a metal foil, and then heated and pressed to etch the metal foil of a metal foil-clad laminate, which is a copper foil on the surface. It is obtained by stacking a predetermined number of a circuit-formed inner layer substrate and a prepreg prepared by impregnating a glass cloth having a thickness of 20 to 150 μm with a thermosetting resin composition, and then heating and pressing.

As the base material used for producing the metal foil-clad laminate and the prepreg, non-glass fiber, glass non-woven fabric or glass cloth can be used. Among them, the glass cloth has been subjected to high fiber opening treatment and has an air permeability of 20.
It is desirable that it is not more than cm3 / cm2 / sec. In general glass cloth, the gap between the warp and weft threads is large,
At the intersection and the gap between them, during small-diameter laser processing,
Variations in circularity, inner wall roughness of holes, bending of holes, etc. are likely to occur.

As the thermosetting resin composition used in the present invention, both the thermosetting resin composition used for producing the metal foil-clad laminate and the thermosetting resin composition used for producing the prepreg are epoxy resin-based, Thermosetting resins in general can be used, such as phenol resin type, polyimide resin type, unsaturated polyester resin type, polyphenyl ether resin type, etc., alone, modified products, and mixtures. The types of the thermosetting resin composition used for producing the metal foil-clad laminate and the thermosetting resin composition used for producing the prepreg may be the same or different.

The thermosetting resin composition contains a thermosetting resin as an essential component, and if necessary, a curing agent for the thermosetting resin, a curing accelerator, an inorganic filler and a solvent. be able to. A thermosetting resin having a low self-hardening property such as an epoxy resin needs to contain a curing agent or the like for curing the resin.

When the thermosetting resin composition is an epoxy resin type, it is preferable because it has a good balance of electrical characteristics and adhesiveness. Examples of the epoxy resin contained in the epoxy resin-based resin composition include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, bisphenol A novolac type epoxy resin,
Examples thereof include bisphenol F novolac type epoxy resin, cresol novolac type epoxy resin, diaminodiphenylmethane type epoxy resin, and epoxy resin flame-retarded by halogenating a part of hydrogen atoms in these epoxy resin structures. . Examples of the curing agent contained in the epoxy resin-based resin composition include amide-based curing agents such as dicyandiamide and aliphatic polyamide, amine-based curing agents such as ammonia, triethylamine, and diethylamine, phenol novolac resin, and cresol. Examples include phenolic curing agents such as novolac resins and p-xylene-novolac resins, and acid anhydrides.

The inorganic filler which can be contained in the thermosetting resin composition includes inorganic powder fillers such as silica, calcium carbonate, aluminum hydroxide, talc and clay, glass fiber, pulp fiber, Examples of the solvent that can be contained in the thermosetting resin composition include amides such as N, N-dimethylformamide, ethylene glycol monomethyl ether, and the like. Ethers, ketones such as acetone and methyl erketoton, alcohols such as methanol and ethanol, aromatic hydrocarbons such as benzene and toluene, and the like.

The method of impregnating the glass cloth with the thermosetting resin composition is not particularly limited, and a general method can be applied. After impregnating the glass cloth with the thermosetting resin composition, it may be dried by heating if necessary.

The metal foil used in the present invention is copper,
Single, alloy, or composite metal foils of aluminum, brass, nickel, etc. can be used, and a single-sided metal-clad laminate or double-sided metal-clad laminate in which metal foils are laminated and molded can be used instead of the metal foil. The metal foil is not limited to being used only for producing a metal foil-clad laminate, and may be used by laminating it on one side or both sides of the laminate in which the inner layer substrate and the prepreg are laminated. The thickness of this metal foil is generally 0.003 to 0.070 mm when it is used for producing a metal foil-clad laminate, and is laminated on one side or both sides of the laminate in which the inner layer substrate and the prepreg are laminated. In this case, 0.03 to 0.035 mm is common.

The conditions for heating and pressurizing the metal foil-clad laminate and the conditions for heating and pressurizing after laminating the inner layer substrate and the prepreg are appropriately selected depending on the condition that the thermosetting resin composition is a curing agent. It may be adjusted and heated and pressed, but
If the pressure applied is high, the dimensional shrinkage of the conductor circuit may vary greatly, so within the range that satisfies the formability,
It is preferable to pressurize as low as possible. It is preferable to heat and pressurize under a reduced pressure atmosphere of 300 Torr or less because the moldability becomes good.

The method for etching the metal foil on the surface of the metal foil-clad laminate is not particularly limited, and a general method can be applied depending on the metal foil and the etching resist used for the etching.

[0023]

Example 1 As a thermosetting resin composition, an epoxy resin resin composition comprising the following two kinds of epoxy resins, a curing agent, a curing accelerator and a solvent was used. Epoxy resin 1: 50 parts by weight of bisphenol A novolac type epoxy resin (using Epicron N868 manufactured by Dainippon Ink and Chemicals, Inc.). Epoxy resin 2: brominated bisphenol A epoxy resin (manufactured by Sumitomo Chemical Co., Ltd., trade name ESB-400
50 parts by weight). -Curing agent: Bisphenol A novolac resin (manufactured by Japan Epoxy Resin Co., Ltd., trade name YLH-129) 4
0 parts by weight. -Curing accelerator: 1 part by weight of 1-cyanoethyl-2-phenylimidazole. -Solvent: 90 parts by weight of methyl ethyl ketone.

This resin composition was mixed with glass cloth (# 108
0 type: weight 48 g / m <2>) and the amount of the thermosetting resin composition after drying was adjusted to 62 parts by weight based on 100 parts by weight of the total amount of the thermosetting resin composition and the glass cloth. After impregnation, it was dried at a maximum temperature of 165 ° C. to prepare a prepreg.

Next, a copper foil having a thickness of 18 μm is arranged on both sides of the predetermined number of the obtained prepregs and laminated, and the laminate is sandwiched between metal plates and heated at a maximum temperature of 180 ° C. and a pressure of 3.0 MPa for 90 minutes. It was pressed and molded to prepare a double-sided copper-clad laminate.

Next, the double-sided copper-clad laminate thus obtained is subjected to a surface treatment, prepregs are arranged on both sides and laminated, and then 1
Place 2μm general copper foil on both sides and sandwich between metal plates,
A four-layer board was produced by heating and pressing at a maximum temperature of 180 ° C. and a pressure of 2.5 MPa for 80 minutes for molding.

The surface of the obtained four-layer plate was thinned by etching to about 5 to 6 μm, and further roughened with a formic acid solution to form a rust preventive film such as an organic film on the surface. Using the laser machine (LAVIA-1200 Sumitomo Heavy Industries, Ltd.) for direct laser processing from the surface, IVH was formed under the conditions of pulse width 50 μs, pulse energy 9 mj, and shot number 6 shots. further,
After plating the processed holes, create a multilayer printed wiring board,
Reliability was confirmed by a hot oil test.

Example 2 Glass cloth (# 2116 type: weight 104 g / m 2
), The amount of the thermosetting resin composition after drying was adjusted to 43 parts by weight with respect to 100 parts by weight of the total amount of the thermosetting resin composition and the glass cloth, and after impregnation, the maximum temperature was 165. Using a prepreg prepared by drying at ℃, 4 sheets were laminated and copper foil with a thickness of 18 μm was placed on both sides, and the laminate was sandwiched between metal plates to obtain a maximum temperature of 18
A double-sided copper-clad laminate having a plate thickness of 0.4 was prepared by heating and pressuring at 0 ° C. and a pressure of 3.0 MPa for 90 minutes. After that, the surface was thinned by etching and further roughened with a sulfuric acid aqueous solution to form a rust preventive film such as an organic film on the surface. Laser machine (LC-1C21 made by Hitachi Via Mechanics) for direct laser processing from the surface
Using a laser with a pulse width of 40 μs, a frequency of 500 Hz, and a number of shots of 10 shots, a jig plate having a thickness of 1.0 mm, which is formed by previously cutting a laser-processed portion under the double-sided plate, is inserted. Form IVH by processing. Further, a cross-section was observed after plating the processed hole.

Comparative Example 1 Multilayer printing was carried out in the same manner as in Example 1 except that a blackening treatment film was used for the surface treatment and an ultrathin copper foil (5 μm copper foil with carrier) was used as the copper foil on the surface. A wiring board was prepared and a hot oil test was conducted to confirm the reliability.

Comparative Example 2 A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the resin of general FR-4 was used as the resin of the prepreg used, and the hot oil test was conducted to confirm the reliability. .

Comparative Example 3 A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the surface treatment was carried out at 12 μm without etching the copper foil on the surface, and a hot oil test was conducted to confirm the reliability. confirmed.

Comparative Example 4 A cross section was observed in the same manner as in Example 2 except that the surface treatment was performed at 12 μm without etching the copper foil on the surface.

Comparative Example 5 Cross-section observation was carried out in the same manner as in Example 2 except that a jig plate having a thickness of 1.0 mm or more, which had a laser-processed portion previously hollowed out, was not inserted below the double-sided plate. It was

Evaluation, Results The printed wiring boards and double-sided boards obtained in Examples 1-2 and Comparative Examples 1-5 were evaluated for peeling strength, surface treatment life test, reliability test, laser workability and the like.

The results are shown in Table 1. As compared with Comparative Examples 1 to 3, Example 1 has peeling strength, life of surface treatment,
It was confirmed that the laser processability and reliability were good.
Further, it was confirmed that the laser working property of Example 2 was better than that of Comparative Examples 4 to 5.

[0036]

[Table 1] <Laser Machinability Evaluation Criteria> The cross sections of IVH and through holes were observed with an optical microscope. ◯: Good hole shape. Δ: The hole is clear, but the inner wall roughness is large. X: The hole has not been drilled. <Hot oil test evaluation criteria> Hot oil test <260 ° C 10s ← → 30 by daisy chain pattern
The number of cycles until the change rate of the conduction resistance value reached 10% or more at 10 ° C> 10 ° C was counted. ◯: 180 cycles OK Δ: 120 cycles NG <Life of surface treatment> With each surface treatment, it was left to stand at room temperature and the time until discoloration started was visually observed. ○: No change even if left for one week or more. X: Discoloration started within 3 days.

[0037]

EFFECTS OF THE INVENTION As is clear from the above description, according to the present invention, in a non-penetrating metal foil direct laser drilling process for a metal copper clad laminate and a printed wiring board, a general metal foil is thinned to 7 μm or less by etching. Furthermore, it is characterized in that an etching-type surface treatment with a surface roughness of 4 μm or less is performed. Further, in the case of a metal foil laser processability of a through hole, a thickness of a processed part previously cut into the lower side of the metal-clad laminate Characterized by inserting a jig plate of 1.0 mm or more
Provided are a printed wiring board which is excellent in metal foil direct laser processability and reliability and is compatible with high density, and a manufacturing method thereof. The printed wiring board manufactured according to the present invention has high reliability and can be processed with a small diameter, which can contribute to high density, high reliability, and cost reduction.

Claims (6)

[Claims] 1. A metal foil on a surface of a multilayer printed wiring board having an insulating resin layer containing a fibrous base material or a metal foil copper-clad laminate is etched to facilitate formation of a small-diameter through hole for connecting layers. A printed wiring board characterized by obtaining a small-diameter through hole by subjecting a metal foil to a thin treatment and performing a surface treatment on the metal foil so as to increase the absorption rate of laser light, thereby performing a perforating process with a laser from the metal foil surface. Production method. 2. The thickness of the etched metal foil is 7 μm.
The high-density printed wiring board according to claim 1 and the method for manufacturing the same, wherein: 3. The high-density printed wiring board according to claim 1, and the method for producing the same, wherein the surface treatment of the metal foil is an etching treatment having a roughened shape. 4. The high-density printed wiring board according to claim 1, wherein the surface treatment of the metal foil has a surface roughness of 4 μm or less, and a method for manufacturing the same. 5. The glass transition temperature (T
2. The high-density printed wiring board according to claim 1, wherein g) is 160 ° C. or higher, and the method for producing the same. 6. In the case of through copper foil direct laser processing,
The high-density printed wiring board according to claim 1, and a method for manufacturing the same, wherein a jig plate having a thickness of 1.0 mm or more, which is formed by cutting a processed portion in advance, is inserted under the printed wiring board.