JP3409453B2 - Manufacturing method of multilayer printed wiring board - Google Patents

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 used as an electronic component.

[0002]

2. Description of the Related Art In recent years, multi-layered printed wiring boards have been made highly multi-layered and thinned, and accordingly, it has become necessary to improve solder heat resistance after absorbing moisture. Conventional prepregs for multilayer printed wiring boards are generally manufactured by impregnating a base material with a varnish containing an epoxy resin and an amine-based curing agent such as dicyandiamide and drying the varnish. Although the prepreg using is good in adhesiveness with the copper oxide-treated inner layer copper foil, the solder heat resistance after moisture absorption is not sufficient when it is used as a multilayer printed wiring board, and the moisture absorption and heat resistance are improved. Is required.

As a method for improving the hygroscopicity and heat resistance of a cured product of an epoxy resin composition (representing a varnish) using a conventional amine-based curing agent, the present inventors have used a phenol-based curing agent as a curing agent. The method of using is disclosed in Japanese Patent Application No. 6-115723, and an epoxy resin composition for a laminated board containing an epoxy resin, a phenolic curing agent and a phenoxy resin is proposed. However, this Japanese Patent Application No. 6
No. 115723, a prepreg is prepared using a varnish containing an epoxy resin, a phenolic curing agent and a phenoxy resin, and the prepreg and the copper oxide-treated inner layer copper foil are adhered to each other to form a multilayer print. It has been found that when a wiring board is manufactured, the adhesive strength between the prepreg and the inner layer copper foil is largely varied depending on the manufacturing conditions.

[0004]

In view of the above circumstances, the problem to be solved by the present invention is to provide an epoxy resin, a varnish containing a phenolic curing agent having two or more phenolic hydroxyl groups in the molecule and a phenoxy resin. We have developed a method in which the adhesive force between the prepreg and the inner layer copper foil is always good when a multilayer printed wiring board is manufactured by bonding the prepreg obtained by impregnating the base material and drying it to the inner layer copper foil treated with copper oxide. It is to be. That is, an object of the present invention is to provide a method for producing a multilayer printed wiring board capable of bonding a prepreg using a phenolic curing agent as a curing agent and a copper oxide-treated inner layer copper foil with good adhesive strength. Is.

[0005]

A method for manufacturing a multilayer printed wiring board according to claim 1 of the present invention comprises an epoxy resin, a phenolic curing agent having two or more phenolic hydroxyl groups in the molecule, and a weight average molecular weight of 5000. Impregnating a substrate with a varnish containing a phenoxy resin of ˜100,000,
A method of manufacturing a multilayer printed circuit board for bonding the dried prepreg comprising copper oxide treated inner layer copper foil, before
The phenoxy resin is bisphenol and epichlorohydric
Is a phenoxy resin synthesized from a resin having a melt viscosity at 130 ° C. of a resin component of the prepreg of 400 to
It is characterized by 1500 poise.

A method for manufacturing a multilayer printed wiring board according to claim 2 is the method for manufacturing a multilayer printed wiring board according to claim 1, wherein the phenol-based curing agent having two or more phenolic hydroxyl groups in the molecule is represented by the following formula: It is characterized by being a novolac resin having a skeleton represented by

[0007]

[Chemical 2]

The present invention will be described in detail below. The epoxy resin used in the present invention is a compound having two or more epoxy groups in the molecule, and examples thereof include bisphenol A type epoxy resin, cresol novolac type epoxy resin, and trifunctional type epoxy resin.

Examples of the phenol-based curing agent having two or more phenolic hydroxyl groups in the molecule used in the present invention include a phenol novolac resin and a cresol novolac resin having a skeleton represented by the above formula. A trifunctional phenol compound having three hydroxyl groups in the molecule can also be used.

The phenoxy resin used in the present invention is a linear polymer synthesized from bisphenol such as bisphenol A and tetrabromobisphenol A and epichlorohydrin, and has a weight average molecular weight of 5,000 to 100,000.
Is what is . The reason is that the phenoxy resin in the present invention is added in order to act as a thickener, but when the weight average molecular weight is less than 5000, the thickening effect becomes small, and the melt viscosity of the resin component of the prepreg is aimed at. If the weight average molecular weight exceeds 100,000, it becomes difficult to obtain a varnish having a uniform composition due to poor solubility in a solvent.

The varnish of the present invention contains an epoxy resin, a phenolic curing agent having two or more phenolic hydroxyl groups in the molecule, and a phenoxy resin. In addition to these, a curing accelerator, an amine curing agent, a solvent, Inorganic fillers and the like may be included within a range that does not impair the object of the present invention.

The base material used in the present invention is not particularly limited, and various cloths and papers such as glass cloth and glass paper can be used.

Further, in the present invention, the prepreg and the copper oxide-treated inner layer copper foil are bonded to each other. This copper oxide treatment is a chemical oxidation treatment called blackening treatment, and the copper foil has a glossy surface. This is a treatment for improving the adhesiveness of the glossy surface of the copper foil. Usually in the manufacture of multilayer printed wiring boards,
The matte surface of the copper foil is bonded to the prepreg at the stage of manufacturing the inner layer material.When bonding the inner layer copper foil and the prepreg after forming the inner layer circuit, the glossy surface of the copper foil and the prepreg should be bonded. become. In order to improve the adhesiveness, it is preferable to roughen the glossy surface of the inner layer copper foil by brushing or the like before performing the chemical oxidation treatment.

In the present invention, the melt viscosity at 130 ° C. of the resin component of the prepreg is 400 to 150.
It is important to have 0 poise. The resin component in this case refers to a flowable component in the prepreg, in other words, by separating from the base material by some method, the component whose melt viscosity can be measured is expressed as a resin component. There is. Therefore, when the varnish contains a powdery component such as an inorganic filler, the powdery component is also included in the resin component of the prepreg. The present inventors have examined the melt viscosity at 130 ° C. of the resin component of the prepreg, and when it is less than 400 poise, the adhesive strength between the prepreg and the copper oxide-treated inner layer copper foil is low, but 400 poise. It has been found that good adhesive strength can be obtained when the above is the case. The reason for this is that when the melt viscosity is less than 400 poise, the resin component flows out from the prepreg end portion during pressure molding, and therefore, the resin component flows inside the copper oxide treated surface of the inner layer copper foil (gap portion). It is considered that the adhesive strength becomes low because it is not press-fitted. Further, the melt viscosity of the resin component at 130 ° C. is 15
When it is higher than 00 poise, the fluidity of the resin component at the time of molding becomes remarkably poor, the unevenness formed by the inner layer circuit cannot be completely filled with the resin component, and a void defect is likely to occur. is there.

In the case of a conventional prepreg using dicyandiamide as a curing agent, even if the resin component of the prepreg has a melt viscosity at 130 ° C. of less than 400 poise, the prepreg is bonded to the copper oxide-treated inner layer copper foil. It was confirmed that the power was high. Therefore, by setting the melt viscosity of the resin component of the prepreg at 130 ° C. to 400 poise or more, the adhesion between the prepreg and the copper oxide-treated inner layer copper foil becomes good because the phenolic hydroxyl group in the molecule is This seems to be a feature when using a prepreg having a phenolic curing agent having two or more of the above as the curing agent.

One of the resin components of the prepreg
Means for adjusting the melt viscosity at 30 ° C. to 400 to 1500 poise include a method of controlling the drying conditions during the preparation of the prepreg and a method of incorporating a thickener such as a phenoxy resin in the resin component. Prepregs for printed wiring boards also need to have an appropriate gelling time, and it is difficult to control the drying conditions alone to obtain a prepreg that has an appropriate gelling time and an appropriate melt viscosity. Therefore, in the present invention, a prepreg having an appropriate gelling time and an appropriate melt viscosity is obtained by a method of incorporating a phenoxy resin having a thickening effect into a varnish. Of course, in the present invention, there is no problem in controlling the drying conditions at the same time so that the melt viscosity falls within the target range.

[0017]

In the present invention, 13 of the resin components of the prepreg are included.
The melt viscosity at 0 ° C. of 400 poise or more works so that the resin component is easily pressed into the inside (gap) of the copper oxide treated surface (blackening treated surface) of the inner layer copper foil during molding. Therefore, it seems that the method of the present invention improves the adhesive force between the copper oxide treated surface of the inner layer copper foil and the resin component of the prepreg.

[0018]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples.

(Examples 1 to 4 and Comparative Examples 1 to 3) As shown in Tables 1 and 2, the respective raw materials were blended and mixed to obtain an epoxy resin and 2 phenolic hydroxyl groups in the molecule. Phenolic curing agent having more than one, phenoxy resin,
A varnish containing a curing accelerator and a solvent was prepared. Next, the obtained varnish was impregnated into a glass cloth substrate [Asahi Schebel Co., Ltd., product number 216L] and then dried at 150 ° C. to prepare a prepreg having a thickness of 0.1 mm.
The drying time was adjusted so that the melt viscosity of the resin component of the prepreg (minimum melt viscosity measured at 130 ° C.) at the stage of prepreg has the values shown in Tables 1 and 2 and It was set for each comparative example. The melt viscosity was measured by separating the resin component from the prepreg, and using a Koka type flow tester manufactured by Shimadzu Corporation for this resin component, a nozzle 0.5 mmφ × 10 mm (length), a load of 20
It was carried out by a method of measuring the minimum melt viscosity at 130 ° C. under the conditions of kg and preheating for 30 seconds.

Next, details of each raw material shown in Tables 1 and 2 will be described. Epoxy resin A: Tetrabromobisphenol A type epoxy resin, product number DER511 made by Dow Chemical Co., which has an epoxy equivalent of 500 Epoxy resin B: Cresol novolac type epoxy resin, product number Y made by Tohto Kasei Co., Ltd. having an epoxy equivalent of 200
DCN702P Phenolic curing agent C: Phenol novolac resin, trade name "Tamanor 752" manufactured by Arakawa Chemical Industry Co., Ltd. having an OH equivalent of 105 Phenol curing agent D: Trifunctional phenolic compound having three phenolic hydroxyl groups in the molecule which is a curing agent, OH equivalent of Honshu Chemical Industry Co., Ltd. under the trade name of 97 "tris phenol PHBA" phenoxy resin: weight-average molecular weight (M _W) is 4260
0, number average molecular weight (M _n ) is 11,200, trade name “PKHH” manufactured by Union Carbide Co., Ltd. Curing accelerator E: 2 ethyl 4 methyl imidazole curing accelerator F: triphenylphosphine solvent: methyl ethyl ketone

The prepreg thus obtained, the inner layer material and the copper foil were laminated as shown in FIG. 1 and molded to prepare a four-layer multilayer printed wiring board. To explain the configuration shown in FIG. 1,
The inner layer material 3 has a thickness of 3 on the upper and lower surfaces of the insulating layer 5 having a thickness of 0.5 mm.
The inner layer copper foils 6 and 6 having a thickness of 5 μm are adhered, and inner layer circuits are formed on the inner layer copper foils 6 and 6 by an etching method.
Moreover, the surface thereof is treated with copper oxide. And
The three prepregs 1 obtained above are arranged on the upper and lower surfaces of the inner layer material 3, and the thickness 1 is formed on the outer upper and lower surfaces thereof.
An outer copper foil 2 having a thickness of 8 μm is arranged. The inner layer material 3 is made by using a glass cloth base material epoxy resin copper clad laminate, and the copper oxide treatment of the inner layer copper foils 6 and 6 is performed by performing the following treatment on the glossy surface of the inner layer copper foil. I went.

[Copper Oxide Treatment Method] After buffing the glossy surfaces of the inner layer copper foils 6 and 6, the inner layer material 3 is dipped in a copper chloride solution for 25 seconds, washed with water, and then dipped in a hydrochloric acid solution for 60 seconds and washed with water. Then, it is immersed in a blackening treatment solution at 96 ° C. for 60 seconds, then washed with water and dried to obtain the copper oxide-treated inner layer material 3. In addition,
An aqueous solution containing sodium chlorite, sodium phosphate and sodium hydroxide is used as the blackening treatment liquid.

The molding conditions for manufacturing the multilayer printed wiring board were as follows in each of the examples and the comparative examples.

[Molding conditions] First step: pressure 5 kg / cm ² , temperature 120 ° C., time 10 minutes Second step: pressure 20 kg / cm ² , temperature 120 ° C.
Time 5 minutes Third step: pressure 40 kg / cm ² , temperature 120 ° C.,
Time 5 minutes Fourth step: pressure 40 kg / cm ² , temperature raised to 170 ° C. fifth step: pressure 40 kg / cm ² , temperature 170 ° C.
Time 90 minutes 6th step: Maintain pressure of 40 kg / cm ² and cool to room temperature

With respect to the multilayer printed wiring board obtained above, the peel strength of the inner layer copper foil was measured, and the results are shown in Table 1.
And shown in Table 2. The inner layer copper foil peeling strength is measured by measuring the adhesive force between the copper oxide-treated surface of the inner layer copper foil and the prepreg layer.As a measuring method, the matte surface not treated with copper oxide is exposed. A line with a width of 10 mm was formed on the inner copper foil, and the peeling strength (adhesion between the copper oxide treated surface and the prepreg layer) in the 90 ° direction of the line was 50.
It was measured at a peeling speed of mm / min.

The cross section of the multilayer printed wiring board obtained above was observed with an electron microscope and the results are shown in Tables 1 and 2.
It was shown to. In this observation, the adhesive interface between the copper oxide treatment (blackening treatment) surface of the inner layer copper foil and the prepreg layer was enlarged 10,000 times,
This is an observation of the state of resin penetration (state of being pressed) in the thickness direction of the blackening treatment.

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from Tables 1 and 2, in each of the examples of the present invention, the peel strength of the oxidation treated surface of the inner layer copper foil is higher than that of Comparative Examples 1 to 3, It was confirmed that according to the method of the invention, the adhesive strength between the copper oxide treated surface of the inner layer copper foil and the prepreg layer was improved.

[0030]

According to the method for manufacturing a multilayer printed wiring board of the present invention, it is possible to bond a prepreg using a phenolic curing agent as a curing agent and an inner layer copper foil treated with copper oxide with a good adhesive force. As a result, it becomes possible to manufacture a multilayer printed wiring board having excellent performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of a multilayer printed wiring board in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

1 prepreg 2 outer layer copper foil 3 Inner layer material 5 insulating layers 6 Inner layer copper foil

Front page continuation (72) Inventor Eiji Motobu 1048 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Yukihiro Hatta, 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works, Ltd. (56) References JP-A-5-304360 (JP, A) JP-A-60-39898 (JP, A) JP-A-54-163360 (JP, A) JP-A-4-96924 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) H05K 3-46 C08J 5/04-5/24

Claims (2)

(57) [Claims] 1. A base material is impregnated with a varnish containing an epoxy resin, a phenolic curing agent having two or more phenolic hydroxyl groups in the molecule, and a phenoxy resin having a weight average molecular weight of 5,000 to 100,000, and dried. A method for manufacturing a multilayer printed wiring board, comprising bonding an inner copper foil treated with copper oxide to a prepreg, wherein the phenoxy resin is
A compound synthesized from bisphenol and epichlorohydrin
A method for producing a multilayer printed wiring board, which is an enoxy resin , wherein the resin component of the prepreg has a melt viscosity at 130 ° C. of 400 to 1500 poise. 2. The multilayer printed wiring board according to claim 1, wherein the phenolic curing agent having two or more phenolic hydroxyl groups in the molecule is a novolac resin having a skeleton represented by the following formula. Production method. [Chemical 1]