JPH05308191A - Surface treatment method of inner-layer circuit board for multilayer printed wiring board - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the halo phenomenon that occurs at the interface between the circuit copper foil pattern in the inner layer of the multilayer printed wiring board and the prepreg. [Structure] The inner layer circuit board is immersed in an aqueous solution containing components of an alkali, an oxidizing agent and a zinc compound to roughen the surface of the printed copper foil pattern and reduce the halo phenomenon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a printed wiring copper foil pattern of an inner layer circuit board used for a multilayer printed wiring board.

[0002]

2. Description of the Related Art Multilayer printed wiring boards are
Generally, it is manufactured by the following steps. Starting from a single-sided or double-sided copper-clad laminate, a predetermined copper foil circuit pattern is formed on the double-sided copper-clad laminate by an etching method such as a photographic method or a printing method to obtain an inner layer circuit board. The surface of the copper foil circuit pattern of this inner layer circuit board is roughened in order to improve the adhesive force in the subsequent steps. A prepreg is placed on both sides or one side of the inner layer circuit board, and an electrolytic copper foil is further placed on the prepreg to heat and press the whole to obtain a copper clad laminate with an inner layer circuit. A through hole is provided at a required position, and a through hole plating is formed on the through hole to connect the inner layer and the outer layer. A copper foil circuit pattern is formed on the outer layer copper foil by the same method as for the inner layer circuit board. Thus, a multilayer printed wiring board is obtained. by the way,
The reason why the roughening treatment is required is that the copper foil of the double-sided copper-clad laminate used as the inner layer material is an electrolytic copper foil because a thin one is required, and this electrolytic copper foil is a cathode in the manufacturing process. The drum surface becomes a glossy surface and the electrolytic solution side becomes a roughened surface,
Since the roughened surface side is arranged so as to be the inner surface in order to improve the adhesive strength of the double-sided copper clad laminate, it is manufactured.
The glossy side is the surface side of the copper foil circuit pattern of the inner layer circuit board, the adhesive strength with the prepreg resin arranged on the outside is improved, and in order to eliminate delamination defects due to thermal shock during the soldering process, etc. It is necessary to roughen the surface of the circuit pattern. As a method of roughening the copper foil circuit pattern surface of the inner layer circuit board, a copper oxide circuit pattern surface of the inner layer circuit board is formed with an oxidation treatment or a cuprous oxide called blackening treatment in which black copper oxide is formed. Surface treatment by brown oxidation called "Brown treatment" is performed. This surface treatment method by oxidation of copper is a method of obtaining a so-called anchor (anchor) effect of forming needle crystals of copper oxide to increase the surface area, and the anchor effect increases the bonding area of the conductor. Although it is a method that can easily obtain an excellent adhesive force at the interface between the conductor and the prepreg resin, copper oxide has a drawback that it easily dissolves in an acid, and therefore, in the through-hole plating process. The copper foil circuit pattern surface that constitutes the wall surface of the hole for through-hole plating by the acid treatment such as hydrochloric acid or sulfuric acid used,
Phenomenon (halo phenomenon) that changes from brown or black to pink due to acid attack occurs. If such a phenomenon occurs, there is a problem in that the portion is poor in adhesive strength, so that the interlayer may be easily peeled off due to thermal shock in a soldering process or the like, which may lead to an accident of the printed wiring board. The recognition that this halo phenomenon impairs the reliability of the multilayer printed wiring board is rapidly increasing with the increasing demand for the multilayer printed wiring board, and the demand for improvement is also increasing. The present inventors have completed the present invention when they are earnestly studying a surface roughening method that reduces the halo phenomenon and does not increase the manufacturing cost.

[0003]

According to the present invention, in order to reduce the halo phenomenon, the printed wiring pattern surface of an inner layer circuit board for a multilayer printed wiring board is immersed in an aqueous solution containing an alkali, an oxidizing agent and a zinc compound component. Then, a surface treatment method for roughening the surface of the printed wiring pattern is applied. As alkali, sodium hydroxide,
Potassium hydroxide or the like can be used. As the oxidizing agent, potassium persulfate, sodium chlorite, sodium hypochlorite, potassium perchlorate, potassium chlorate and the like can be used. As the zinc compound, zinc oxide, zinc chloride, zinc sulfate, zinc acetate, zinc nitrate, zinc sulfide, zinc hydroxide, zinc phosphate, zinc carbonate, zinc ammonium sulfate and the like can be used. [In addition, trisodium phosphate, sodium carbonate, sodium sulfate,
Sodium borate and the like can also be added. The appropriate concentration of each component is not particularly limited,
For example, 5 to 100 g / l when sodium hydroxide is used as an alkali, 5 to 100 g / l when sodium chlorite is used as an oxidizing agent, and 0.1 to 30 g when zinc acetate is used as a zinc compound. / L range. The dipping conditions should be selected so that the treated surface of the copper foil will not be under-treated or over-treated.
Specifically, the temperature is preferably 95 ° C. or lower, and the time is preferably in the range of 1 to 10 minutes. It is possible to determine the concentrations of the above-mentioned components that can be processed under the range of the immersion conditions. Further, there is no problem in performing pretreatment of the copper foil surface such as degreasing, washing with acid, and soft etching before dipping in the surface-roughening treatment solution of the present invention.

[0003]

Example 1 An inner layer circuit board using a glass cloth substrate epoxy resin double-sided copper clad laminate (board thickness 1.0 mm, copper foil thickness 70 μ) was prepared, and the circuit copper foil pattern surface of this inner layer circuit board was prepared. After polishing, it was immersed in an aqueous solution containing 20 g / l of sodium hydroxide, 50 g / l of sodium chlorite, 1 g / l of zinc acetate and 3 g / l of trisodium phosphate at 90 ° C. for 3 minutes, and washed with water. And dry at 120 ° C. for 60 minutes.

[0004]

Example 2 The inner layer circuit board used in the above Example 1 was prepared, the surface of the circuit copper foil pattern of this inner layer circuit board was polished, and then 20 g / l of sodium hydroxide, 50 g / l of sodium chlorite and oxidized. It is immersed in an aqueous solution containing 1 g / l of zinc at a temperature of 90 ° C. for 3 minutes, washed with water, and dried at 120 ° C. for 60 minutes.

[0005]

COMPARATIVE EXAMPLE The inner layer circuit board used in Example 1 was prepared,
After polishing the circuit copper foil pattern surface of this inner layer circuit board,
Sodium hydroxide 20g / l, sodium chlorite 50
g / l, trisodium phosphate 3 g / l temperature 90 ° C
Soak in water solution for 3 minutes, wash with water,
Dry for 0 minutes.

[0006]

[Test Method] In order to test the halo resistance and the like, test pieces were prepared from the inner layer circuits subjected to the immersion treatment of Examples 1 and 2 and Comparative Example through the following procedures (1) to (5). (1) Two glass cloth-based epoxy resin prepregs each having a thickness of 0.1 mm are placed on the upper and lower sides of the inner layer circuit board after the dipping treatment, and two copper foils each having a thickness of 18 μ are stacked on the prepreg. By heating and pressurizing at 40 ° C. and 40 kg / cm ² for 60 minutes, a copper clad laminate with an inner layer circuit is obtained. (2) Rotation speed of 70,00 on copper clad laminate with inner layer circuit
A 0.4 mm diameter hole is drilled under a processing condition of 0 rpm and a feed rate of 1,400 mm / min. (3) After performing degreasing and soft etching pretreatment, it is immersed in an aqueous solution of palladium chloride and tin chloride (Cataposit 44, manufactured by Shipley Co., Ltd.) for 5 minutes. (4) After washing with water, it is dipped in an electroless copper plating solution (Cuposit, manufactured by Shipley Co., Ltd.) for 20 minutes. (5) After washing with water, electrolytic copper plating is performed. Thereby, the test pieces of Examples 1 and 2 and Comparative Example were obtained. The halo value, solder heat resistance, and inner layer peel strength of these test pieces were measured and the results shown in Table 1 were obtained.

[0007]

[Table 1] However, the halo value was measured by peeling the prepreg layer to expose the circuit copper foil pattern surface of the inner layer and measuring the halo value. The solder heat resistance was measured according to JIS C-6481 by floating in a solder bath at 26 ° C. and measuring the time for peeling between layers. The inner layer peel strength was measured according to JIS C-6481, and the peel strength between the inner layer conductor surface and the prepreg resin was measured.

[0008]

The surface treatment method for the inner layer circuit board of the present invention can reduce the halo phenomenon occurring at the interface between the inner layer circuit copper foil pattern and the prepreg, and is substantially the same as the conventional copper oxidation treatment step. Therefore, it is possible to obtain an inner layer circuit board for a multilayer printed wiring board with an extremely low cost increase.

Claims (1)

[Claims] 1. A multilayer printed wiring characterized by roughening the surface of a printed wiring pattern by immersing an inner layer circuit board for a multilayer printed wiring board in an aqueous solution containing components of an alkali, an oxidizing agent and a zinc compound. Surface treatment method for inner layer circuit boards for boards.