JP2001119141A - Multilayer printed wiring board and method of manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board that is filled sufficiently in a point containing no internal layer circuit and has superior accuracy in the thickness of an insulating layer, and a method of manufacturing it. SOLUTION: The multilayer printed wiring board is manufactured by the method in which resin powder is stuck to only a point containing no circuit in an internal layer circuit board, and a pre-preg and a metal foil are piled thereon, and the point is heated and pressurized to laminate and unit in a body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a multilayer printed wiring board and a multilayer printed wiring board manufactured by the method.

[0002]

2. Description of the Related Art A conventional method for manufacturing a multilayer printed wiring board is to impregnate a fiber base material such as a glass woven fabric or an aramid fabric with a thermosetting resin such as an epoxy resin or a polyimide resin.
The required number of prepregs obtained by heating and drying are stacked on an inner circuit board in a required number, a metal foil is further stacked, sandwiched between end plates, and a large number of end plates / inner circuit boards / prepregs / metal foils / end plates are stacked. It is common to set them in between and laminate them together by heating and pressing. At this time, a gap is formed between the prepreg and the portion without the inner layer circuit due to the step corresponding to the thickness of the metal foil forming the inner layer circuit of the inner layer circuit board. The resin impregnated into the resin melts and flows in, filling the gap. In recent years, the speed of electronic devices has increased, and it has been necessary to control the impedance of multilayer printed wiring boards. It has been required to increase the accuracy of the thickness of the insulating layer after molding by heating and pressing. ing.

[0003]

However, in the conventional manufacturing method, as described above, the resin in the prepreg flows to a place where there is no inner layer circuit, so that the thickness of the insulating layer after lamination depends on the shape of the inner layer circuit. Are different.

Therefore, in order to increase the accuracy of the thickness of the insulating layer after molding by heating and pressing, the flow of the resin must be reduced as much as possible, and the amount of the resin impregnated in the prepreg is reduced. In addition, the viscosity during melting by heating is increased to suppress the flow of resin when laminating by heating and pressing. However, as described above, the resin flow must be increased in order to fill a portion having no inner layer circuit, and increasing the accuracy of the thickness of the insulating layer is incompatible with filling a portion having no inner layer circuit. There is a problem that there are many.

SUMMARY OF THE INVENTION The present invention provides a method of manufacturing a multilayer printed wiring board capable of sufficiently filling a portion having no inner layer circuit and having excellent accuracy of the thickness of an insulating layer, and a multilayer printed wiring board manufactured by the method. The purpose is to provide.

[0006]

The present invention is characterized by the following. (1) A method of manufacturing a multilayer printed wiring board in which a resin powder is adhered only to a portion of an inner circuit board where no circuit is provided, a prepreg and a metal foil are laminated, and the laminate is integrated by heating and pressing. (2) A protective film is formed on the surface of the circuit of the inner circuit board, a resin powder is adhered to the surface of the inner circuit board, and then the protective film on the circuit is peeled off. Production method. (3) After adhering the resin powder to the surface of the inner circuit board,
The method for producing a multilayer printed wiring board according to (1), wherein only the resin powder adhering to the circuit is removed by cutting or polishing. (4) A multilayer printed wiring board manufactured by the manufacturing method according to any one of (1) to (3).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The resin powder used in the present invention is obtained by curing a thermosetting resin together with a curing agent and, if necessary, a curing accelerator, and finely crushing the resin. The cured product of the thermosetting resin is obtained by curing a thermosetting resin composition containing an epoxy resin and a curing agent. If necessary, a curing accelerator, a catalyst, an elastomer, a flame retardant, and the like may be added to the thermosetting resin composition.

The epoxy resin may be any one having an epoxy group in the molecule, such as a bisphenol A epoxy resin, a bisphenol F epoxy resin, a bisphenol S epoxy resin, an alicyclic epoxy resin, Group epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, bisphenol A novolak epoxy resin, diglycidyl etherified biphenol, diglycidyl etherified naphthalene diol, diglycidyl etherified phenol And diglycidyl ethers of alcohols, and alkyl-substituted, halogenated and hydrogenated products thereof. These may be used in combination,
Components other than the epoxy resin may be included as impurities.

The curing agent for an epoxy resin used in the present invention can be used without any limitation as long as it can cure an epoxy resin. Examples thereof include polyfunctional phenols, amines, imidazole compounds, acid anhydrides, organic anhydrides, and the like. Phosphorus compounds and their halides.

Examples of the polyfunctional phenols include monocyclic bifunctional phenols such as hydroquinone, resorcinol, catechol, and polycyclic bifunctional phenols such as bisphenol A, bisphenol F, naphthalene diols, biphenols, and halides thereof. There are alkyl group substituents and the like. Further, there are novolaks and resols which are polycondensates of these phenols and aldehydes.

Examples of amines include aliphatic or aromatic primary amines, secondary amines, tertiary amines, quaternary ammonium salts and aliphatic cyclic amines, guanidines, urea derivatives and the like. is there.

Examples of these compounds include N, N-
Benzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, tetramethylguanidine, triethanolamine, N, N'-dimethylpiperazine, 1,
4-diazabicyclo [2,2,2] octane, 1,8-
Diazabicyclo [5,4,0] -7-undecene, 1,
5-diazabicyclo [4,4,0] -5-nonene, hexamethylenetetramine, pyridine, picoline, piperidine, pyrrolidine, dimethylcyclohexylamine, dimethylhexylamine, cyclohexylamine, diisobutylamine, di-n-butylamine, diphenylamine, N -Methylaniline, tri-n-propylamine,
Tri-n-octylamine, tri-n-butylamine,
Examples include triphenylamine, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, triethylenetetramine, diaminodiphenylmethane, diaminodiphenylether, dicyandiamide, tolylbiguanide, guanylurea, and dimethylurea.

Examples of the imidazole compound include imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-imidazole,
Benzyl-2-methylimidazole, 2-heptadecylimidazole, 4,5-diphenylimidazole, 2-
Methylimidazoline, 2-phenylimidazoline, 2-
Undecylimidazoline, 2-heptadecylimidazoline, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidazoline, 2-phenyl-4-methylimidazoline, benzimidazole, 1- And cyanoethylimidazole.

Examples of the acid anhydride include phthalic anhydride, hexahydrophthalic anhydride, pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride and the like.

As the organic phosphorus compound, any phosphorus compound having an organic group can be used without particular limitation. Examples thereof include hexamethylphosphoric triamide, tri (dichloropropyl) phosphate, tri (chloropropyl) phosphate, Examples include triphenyl phosphite, trimethyl phosphate, phenylphosphonic acid, triphenylphosphine, tri-n-butylphosphine, and diphenylphosphine.

These curing agents can be used alone or in combination. The amount of the curing agent for the epoxy resin can be used without any particular limitation as long as the curing reaction of the epoxy group can proceed, but is preferably 0.01 to 5.0 with respect to 1 mol of the epoxy group.
It is used in the range of equivalents, particularly preferably in the range of 0.8 to 1.2 equivalents.

Further, the thermosetting epoxy resin composition of the present invention may optionally contain a curing accelerator. Representative curing accelerators include, but are not limited to, tertiary amines, imidazoles, quaternary ammonium salts, and the like.

In order to grind such a cured resin finely, the ground with a hammer or the like is finely ground with a mortar, a mortar or a bead mill. The size of the powder is smaller than the thickness of the inner layer circuit. Preferably, it is preferably in the range of 1 to 50 μm. If it is too small, handling may be difficult, wettability may be reduced, and flow of the resin may be hindered. If it exceeds 50 μm, irregularities are likely to be formed on the substrate at locations thicker than the inner layer circuit, and the mechanical strength of the substrate may be reduced.

In order to adhere the resin powder only to a portion of the inner circuit board where no circuit is provided, a resin powder previously moistened with an organic solvent is locally applied to a portion of the inner layer circuit having no metal by using compressed air or the like. , Resin powder can be adhered. For this spraying, a jet-type spraying machine or a gun-type spraying machine can be used to spray only the portion without metal foil while moving on the inner circuit board. It is preferable to use, as the organic solvent, one having a low boiling point and not remaining on the laminated plate after heat molding, for example, methanol (boiling point 78.3 ° C.) or ethanol (boiling point 64.56 ° C.). The reason why the resin powder is moistened in advance with an organic solvent is to swell the resin powder and to swell the resin portion sprayed at a high pressure to adhere the resin powder.

In order to adhere only to the part without metal foil,
Although it can also be realized by selectively performing the spraying part as described above, a protective film is formed on the surface of the circuit of the inner circuit board, and a resin powder is attached to the surface of the inner circuit board,
Thereafter, it is also possible to peel off the protective film on the circuit. For the protective film, various resist materials that are usually used for manufacturing a printed wiring board can be used. Such a resist is preferable because it is easily peeled since it is used after being peeled.

Further, in order to attach the resin powder only to a portion having no metal foil, after attaching a resin powder to the surface of the inner circuit board,
It is also possible to remove only the resin powder attached to the circuit by cutting or polishing. Also, after protecting the metal foil forming the circuit of the inner layer circuit board with a sheet of a material insoluble in organic solvents such as polyimide and ester, apply an organic solvent to the inner layer circuit board, and adhere resin powder in advance. A method of removing the resin powder adhering to the metal foil by facilitating adhesion of the resin powder and then peeling off the sheet may be used. Alternatively, after adhering the resin powder to the entire inner layer circuit board to which the resin powder is easily attached with an organic solvent, the surface is cut or polished to remove the resin powder adhering to the metal foil portion of the inner layer circuit. May be.

As the inner layer circuit board, a metal foil-clad laminate obtained by processing metal foil on the surface into a circuit shape can be used. The prepreg is prepared by impregnating a resin made of a fabric made of inorganic fibers such as glass or other organic fibers alone or by blending with a resin and drying. Examples of the resin to be impregnated include thermosetting resins such as epoxy resin, polyimide resin, and phenol resin. The outermost layer of the laminate may be a metal foil such as a copper foil, an aluminum foil, or a stainless steel foil, or a sheet made of an organic material capable of withstanding the heat and pressure molding of the laminate.

[0023]

As an example, as shown in FIG. 1 (a), unnecessary portions of copper foil on both sides of MCL-E-679 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is a double-sided copper-clad laminate. Circuit 31 of inner circuit board 3 produced by etching away
The adhesive sheet 7 made of polyester cut out according to the shape of the above is adhered to the inner circuit board 3, and as shown in FIG. The epoxy resin powder 5 easily. Brominated bisphenol A type epoxy resin (epoxy equivalent 47
0, bromine content 20%, AER8011, trade name of Toto Kasei Co., Ltd., high molecular weight brominated bisphenol A type epoxy resin (bromine content 53%, number average molecular weight 25,000)
0, the number average molecular weight is measured by gel permeation chromatography using a standard polystyrene calibration curve), a phenol novolak resin (hydroxy equivalent: 106, HP850N, trade name of Hitachi Chemical Co., Ltd.) as a curing agent, an accelerator Was added in an amount of 0.5% by weight with respect to the amount of the epoxy resin. Here, the blending amounts of the two types of epoxy resin and the blending amount of the phenol novolak resin were adjusted so that epoxy equivalent / hydroxyl equivalent = 1. Two types of epoxy resin are
The mixing ratio was adjusted so that the amount of bromine was 28% by weight based on the total amount of the epoxy resin composition containing no inorganic substance.
The obtained epoxy resin composition was applied to a depth of 1 mm and a length of 10 m.
It was poured into a simple mold having a size of mx 10 mm, heated at 180 ° C for 1 hour and cured to prepare a resin plate, which was crushed with a hammer and turned into a powder with a bead mill. As shown in FIG. 1 (c), after the inner circuit board 3 pulled up from the first tank is inserted into the empty second tank, the inner circuit board 3 is coated with the airbrush 8 containing the epoxy resin powder 5 in the paint tank. By spraying, the epoxy resin powder 5 was adhered. This epoxy resin powder 5
The size was about 15 μm in average diameter. Next, FIG.
As shown in (d), in the third tank, the inner layer circuit board 3 to which the epoxy resin powder 5 has adhered is kept in an atmosphere of about 80 ° C. for 5 minutes and dried, and the methanol 6 is evaporated and the epoxy resin adhered. The powder 5 is dried and fixed, and the inner circuit board 3 is dried.
Adhere to As shown in FIG.
The adhesive protection sheet 7 to which the upper epoxy resin powder 5 was adhered was peeled off. As shown in FIG. 2, copper foil 1 and prepreg 2
On both sides of the inner circuit board 3 prepared above,
Under a condition of 2.0 MPa at 5 ° C. for 60 minutes, the layers were integrated by heating and pressing. As a comparative example, an inner circuit board 3 was produced in the same manner as in the example except that the inner circuit board 3 was not subjected to the above-mentioned epoxy resin powder 5 adhering treatment.

Table 1 shows the results of the area occupancy of voids and thin spots and the thickness of the formed insulating layer in the multilayer printed wiring board thus manufactured.

[0025]

[Table 1]

From the above, since the resin powder is previously attached to the portion of the inner layer circuit where no metal foil is present, it is possible to easily fill the gap between the step of the inner layer circuit and the prepreg disposed on the surface of the inner layer circuit board. Because it is possible, it is possible to reduce the pressure at the time of lamination molding under heat and pressure, as well as minute voids called voids and waste that partially lacks resin, and warpage, twisting and the like of the laminated plate can be achieved. Distortion and deformation of the inner layer circuit can be reduced. Further, since a large current is required, it is possible to use a thick metal foil for forming the inner layer circuit and easily manufacture a laminated board having a thin insulating layer. This also gives
Since the amount of resin impregnated in the prepreg can be reduced and the viscosity at the time of heating and melting can be increased, the accuracy of the thickness of the insulating layer between the layers can be improved.

[0027]

As described above, according to the present invention, a method for manufacturing a multilayer printed wiring board in which a portion having no inner layer circuit can be sufficiently filled and the thickness of the insulating layer is excellent in accuracy. Can be provided.

[Brief description of the drawings]

FIGS. 1A to 1E are schematic sequence diagrams showing respective steps for explaining one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of one embodiment of the present invention.

[Explanation of symbols]

 1. Copper foil 2. Prepreg 3. Inner layer circuit board 5. Epoxy resin powder 6. Methanol 7. Adhesive sheet 8. airbrush

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E346 AA06 AA12 AA15 AA16 AA26 BB01 CC09 DD01 DD02 DD12 DD32 EE02 EE06 EE09 EE12 EE13 EE14 GG01 GG28 HH11

Claims (4)

[Claims] (1) A resin powder is adhered only to a portion of the inner circuit board where no circuit is provided, and a prepreg and a metal foil are overlapped.
A method for producing a multilayer printed wiring board, comprising laminating and integrating under pressure. 2. The method according to claim 1, wherein a protective film is formed on the surface of the circuit of the inner circuit board, a resin powder is adhered to the surface of the inner circuit board, and then the protective film on the circuit is peeled off.
3. The method for producing a multilayer printed wiring board according to item 1. 3. The multilayer printed wiring board according to claim 1, wherein after the resin powder is attached to the surface of the inner circuit board, only the resin powder attached to the circuit is removed by cutting or polishing. Production method. 4. A multilayer printed wiring board manufactured by the manufacturing method according to claim 1.