JPH04154193A - Manufacture of multilayer printed board - Google Patents

Abstract

PURPOSE:To enhance reliability, improve productivity and eliminate pubic hazards as well by chemically oxidizing a copper clad surface of an inner layer board and processing said surface in a hydrazine gas prevailing atmosphere after having formed a brown or dark-colored copper oxide surface. CONSTITUTION:A copper clad surface of an inner layer board which has formed a printed wiring net used an inner layer is chemically oxidized and then, it is processed in a hydrazine gas prevailing atmosphere after the formation of a brown or dark colored copper oxide surface. The pressure of the hydrazine gas is specified to be 50% or below saturated vapor pressure in a processing temperature. In a through hole plating process where electric continuity is made between printed wirings of a multilayer board, brown or dark colored copper oxide is dissolved in a plating solution, which serves to reduce dramatically the generation of 'hollow' which is mainly responsible for the generation of defects, such as electric short circuit or eliminate definitely. It is, therefore, possible to manufacture highly reliable multilayer printed wiring boards without causing any public hazards.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the production of a multilayer printed wiring board characterized by reducing the copper foil surface of the printed wiring board serving as an intermediate layer (inner layer) in a gas phase. It is preferable that the oxidized film on the surface of the copper foil be made into a metallic copper surface without substantially changing the surface shape of the oxidized film on the surface of the copper foil. ” or virtually eliminates the “pink ring” phenomenon.

[Conventional technology and its problems]

In a multilayer printed board, a method of improving the multilayer adhesion of an inner layer board on which a printed wiring network is formed as an intermediate layer is to use a copper foil that has been textured on both sides in advance; After the formation, there are two known methods: (1) forming a copper oxide film on the copper foil surface using an oxidation treatment aqueous solution; (2) treating the copper foil surface with a silane coupling agent or an organic titanate coupling agent; Conventionally, from the viewpoint of adhesion and economy, after forming a printed wiring network for the inner layer on a copper-clad laminate with a glossy surface, it is treated with an oxidizing alkaline aqueous solution to form a brown or black copper oxide film. is used.

However, this copper oxide film, especially cupric oxide, is easily dissolved in acidic aqueous solutions such as hydrochloric acid and sulfuric acid. For this reason, when making small holes in a laminated multilayer board and performing a through-hole plating process, electroless plating, or subsequent electrolytic plating process,
A so-called "halo" or pink ring occurs when the copper oxide film exposed on the hole wall is sequentially dissolved by the acidic liquid, which is a drawback that causes a decrease in the reliability of printed wiring boards such as insulation. was there.

As a method to prevent the halo or pink ring that occurs when this brown or black copper oxide film is used, recently, the copper oxide film on the surface of the copper foil obtained in steps A method of changing to a copper oxide film or a copper film (Japanese Unexamined Patent Publication No. 153797/1983, etc.) has been disclosed. These methods can achieve adhesion strength at a level that can be put to practical use, but they require a new liquid phase reduction treatment process, and the adhesive strength is lower than that of brown or black copper oxide films, so they are not practical. In order to obtain adhesive strength that can withstand corrosion, the reducing conditions must be extremely strict. More r Hello J
There were variations in the effectiveness of preventing the occurrence of aqueous reducing agents, and a new problem occurred in the treatment of waste liquid of the aqueous reducing agent solution.

[Means to solve the problem]

The present inventors have found that by reducing a copper oxide film that has been oxidized to brown or black, not only is there no variation in the "halo" prevention effect, but there is no or only a small decrease in adhesive strength (and
We worked hard to find a method for wastewater treatment that would not create new problems.

As a result, the present inventor proposed that the gas phase reduction method be a research subject. However, all conventional printed wiring board manufacturing processes involve processes using water or organic solvent solutions. In the field of printed wiring boards, there are no examples of using hydrazine gas (and it is well known that these gases are toxic, easily combust, and can cause explosions in some cases. The decision to research and develop this subject, which deals with gas, was extremely difficult.

However, fortunately, as a result of small-scale preliminary research, it was confirmed that this gas-phase reduction method has the potential to exhibit extremely excellent performance, and based on this, research and development efforts were conducted to put it into practical use. , we have completed the present invention.

That is, in the method of manufacturing a multilayer printed wiring board, the present invention involves chemically oxidizing the copper foil surface of an inner layer board on which a printed wiring network used as an intermediate layer is formed to form a brown or black copper oxide surface, and then applying hydrazine to the copper foil surface. A method for manufacturing a multilayer printed wiring board characterized by using an inner layer board treated in a gas-present atmosphere, characterized in that the pressure of the hydrazine gas is 50% or less of the saturated vapor pressure at the treatment temperature. This is a method for manufacturing a multilayer printed wiring board.

The configuration of the present invention will be explained below.

The multilayer printed wiring board of the present invention is an inner layer board on which an inner layer printed wiring network used for the above-mentioned intermediate layer is formed, and after chemically oxidizing the copper foil surface to form a black or brown copper oxide surface, In addition to using those that have been dried and treated in an atmosphere containing hydrazine gas, inner layer plates used for multilayer lamination molding, prepregs used for multilayer adhesion,
Any laminated materials such as prepreg and copper foil or single-sided copper-clad laminates for forming the outer layer, and laminated molding methods can be used as long as they fall within the conventionally known concept, and are not particularly limited. It is.

Such laminated materials include E glass, S glass, D glass,
Various glass woven fabrics such as quartz glass, inorganic woven materials such as alumina paper: fully aromatic polyamide, polyimide, fluororesin, polyphenylene sulfide, polyetheretherketone, polyetherimide, liquid crystalline polyester resin, and other super heat-resistant materials woven fabrics made of polyimide, fluororesin, polyphenylene sulfide, polyetheretherketone, polyetherimide, liquid crystal polyester resin, and other super heat-resistant resins; films or sheets made of the above inorganic fibers and super heat-resistant resins Woven fabrics using composite yarns using fibers made from manufactured products; Woven fabrics made of appropriate combinations of the above are used as a reinforcing base material, and bisphenol A type, novolac type, halogenated bisphenol A type, halogenated novolac type, etc. Epoxy resins such as trifunctional or higher polyfunctional epoxy compounds; Cyanate ester resins typically include cyanate resins, cyanate ester-epoxy resins, cyanate ester-maleimide-epoxy resins; Polyfunctional epoxy compounds such as bismaleimide; Maleimide-based resins whose main components are polyfunctional amines such as polyfunctional maleimides and bis(4-aminophenyl)methane; furthermore, they are composed of heat-resistant thermoplastic resins or compositions of thermoplastic resins and thermosetting resins. Prepreg made using resin etc.
Copper foil such as electrolytic copper foil or rolled copper foil, double-sided or single-sided copper-clad laminate made by laminating and molding copper foil and prepreg, inner layer with a printed wiring network formed on one or both sides of the copper-clad laminate. An example is a printed wiring board (inner layer board). Examples of the lamination molding method include conventional hot plate press, hot plate vacuum press, autoclave molding, and continuous press.

The method of forming a brown or black copper oxide film on the inner layer plate of the present invention is known. Usually, after polishing and cleaning the copper foil surface of the inner layer plate, pre-etching (softening) is performed with an aqueous solution such as copper chloride or ammonium persulfate. etching, chemical polishing)
After that, it is treated with an alkaline oxidizing aqueous solution. Here, the alkaline oxidizing aqueous solution and treatment conditions are specifically exemplified by the following, but are not limited to these (although known methods can be used).

■ Sodium hydroxide (NaOH (15g/l)
)/Sodium hypochlorite (NaCIO□(31g#
))/sodium phosphate (15g#'), 70-1
00°C for 10,5-10 minutes.

■, Copper sulfate (50g #) / Sodium chloride (200g
/l), 40-80°C, 3-15 minutes.

■, Acetic acid (20g#)/Ammonium chloride (20g/
Copper acetate (10g, #), 30-80°C, 1
-10 minutes.

■, Copper acetate (10g#')/Copper sulfate (24g/l)
/ Barium sulfide (24g#) / Ammonium chloride (2
4 g/l, 40-50°C, 1-10 minutes.

■, Copper sulfate (25g, #)/Nickel sulfate (25g/
f)/potassium chlorate (25g#'), 70-9
0℃, 1-10 minutes.

(2) Potassium persulfate (20g#)/sodium hydroxide 50g#'), 50-800C, 1-3 minutes.

Among the above-mentioned methods for forming brown or black copper oxide films, the specific methods that have been put into practical use are those that are suitable for forming the obtained oxidized film itself in a multilayered layered manner, or those that are suitable for forming these into a liquid phase. These conditions are suitable for reduction treatment. However, since the present invention uses these after being subjected to gas phase reduction treatment, the one with the best adhesive strength as an oxidized film or a product obtained by reducing it in a liquid phase is necessarily the best after reduction treatment. It's not a thing.

In other words, the copper surface before and after the reduction treatment of the present invention does not seem to have a slightly slender uneven pattern in micrographs or 38M photographs, but it is virtually impossible to distinguish between them within the range of observation. There is no substantial change other than shrinkage caused by the loss of oxygen from copper oxide. Therefore, although the external shape of the oxidized film is substantially maintained, the crystal itself shrinks and the degree of unevenness is reduced, and the copper forming the unevenness is stronger than copper oxide. has been significantly improved. Therefore,
As an oxidized film, it has a higher degree of unevenness than conventional films.
Even in cases where the adhesive is somewhat weak and easily causes contamination, the present invention can be applied as a treatment method that further improves the adhesive strength.

After washing and cleaning the inner layer plate that has been treated with brown or black color as described above, the inner layer plate that has been subjected to the gas phase reduction treatment of the present invention is used, so that "halo" is extremely reduced or does not occur substantially. .

The atmosphere containing hydrazine gas in which the inner layer plate of the present invention is subjected to the reduction treatment is an atmosphere containing gas of a volatile hydrazine derivative such as hydrazine, hydrazine-hydrate, or methylhydrazine, and the pressure thereof is equal to the treatment temperature. saturated vapor pressure or less, preferably 50% or less, and as appropriate,
This is a gas phase atmosphere diluted with non-oxidizing gas.

The method of supplying hydrazine gas is not particularly limited, and examples include evaporating volatile hydrazine and supplying it into non-oxidizing gas; Examples include bubbling the gas and supplying it to a reduction treatment plant together with the degassed hydrazine; or supplying vaporizable hydrazine gas under reduced pressure.

Next, the reduction treatment temperature is usually 140°C or less, preferably in the range of 130°C to 20°C, and the treatment time is appropriately selected from the range of 1 minute to 24 hours, preferably 2 to 90 minutes. . The upper limit temperature here is mainly determined by the dimensional stability of the inner layer plate to be treated, and the lower limit temperature is determined by the hydrazine gas condensing to form a liquid film on the copper oxide film, and the reduction reaction progressing in the liquid film, resulting in the surface condition. is selected from a range in which there is no significant change. For example, when the pressure of hydrazine gas is high compared to the temperature, the unevenness of the copper foil surface decreases and the interlayer adhesive strength after multilayer lamination molding decreases, even though there is no visible liquid phase. Therefore, the partial pressure of hydrazine gas or the partial pressure of water vapor should be set to a low value of 50% or less of the saturated vapor pressure at the processing temperature, and the water produced by the reduction reaction should be easily transferred to the gas phase. It is preferable to keep it in a dry state so that

As described above, the inner layer plate subjected to the vapor phase reduction treatment of the present invention is used as it is in multilayer lamination molding to form a multilayer shield plate with copper foil on both sides, and then subjected to drilling, polishing, desmear treatment,
After electroless plating, electrolytic plating, etc., a multilayer printed wiring board is produced by forming printed wiring patterns on both surfaces.

In addition, in the gas phase reduction treatment of the present invention, there are no problems with waste liquid treatment as in liquid phase reduction treatment. For example, unreacted hydrazine scum is easily removed by passing it through water, and this aqueous solution If a decomposition catalyst and air are supplied to the decomposition catalyst, it becomes harmless, and it is also easy to lead it to a catalytic combustion device and oxidize it.

〔Example〕

The present invention will be explained below with reference to Examples.

Examples 1 to 3 and Comparative Example 1 After removing about half of both sides of a double-sided copper-clad glass epoxy laminate with a thickness of 0.8 mm and a copper foil thickness of 70 m using a known etching method, the copper foil surface was subjected to a black oxidation treatment as conventionally known. is Na0H
(15g/l)/sodium hypochlorite (31g/l)
i! )/sodium phosphate (15 g #') at 90° C. for 5 minutes, followed by washing with water to obtain a black oxidized inner layer plate.

The black oxidized inner layer plate was placed in a dryer capable of vacuum suction, and after drying at normal pressure at a temperature of 130°C for 30 minutes, the reduction treatment temperature was set as shown in Table 1, and the interior of the dryer was vacuumed and dried. After introducing the nitrogen gas, and vacuum suction again, hydrazine was supplied into the nitrogen gas at the partial pressure shown in Table 1 below for reduction treatment, and the reduced inner layer plate was taken out from the dryer.

Using the inner layer plate obtained above, 3 sheets of glass epoxy prepreg (resin content 52%, thickness 0.1 mm) were placed on both sides.
Further, layered with electrolytic steel foil with a thickness of I8-, the temperature was 175°C and 40k.
g/Ci for 2 hours to obtain a 4-layer board.

The adhesion strength of copper foil was measured for some of these.

In addition, for the rest, hole diameter 0.4 mmφ, 80,000 r, p
.

m9.1.000 pieces under the condition of 20ts/rotation, 2.5
Drill holes at intervals of 4 mrn, immerse the drilled 4-layer board in a 4N MCI aqueous solution for 5 minutes, and observe the halo around the hole where the inner layer is located for an arbitrary 1/4 of the holes (125 holes). The length of the largest one was also measured.

The results are shown in Table 1.

Table 1 [Operations and Effects of the Invention] From the detailed description and examples above, the multilayer printed board manufactured by the manufacturing method of the present invention is manufactured using a plating solution in the through-hole plating process for establishing electrical continuity between the printed wirings of the multilayer board. The occurrence of "halos", which tend to cause defects such as electrical short circuits due to the dissolution of brown or black copper oxide, is greatly reduced or completely eliminated.

Furthermore, since the inner layer plate is treated in a gas phase, it is extremely easy to scale up.

Furthermore, the amount or partial pressure of hydrazine gas used in the present invention is as follows:
It has a low concentration and can be used below the explosive limit.
The waste generated by the reduction treatment is also waste, and unreacted components can be removed extremely easily by catalytic combustion, etc., and are essentially non-polluting.

Furthermore, the surface shape of the copper foil that has been subjected to the vapor phase reduction treatment of the present invention and reduced to metallic copper by X-ray analysis is almost the same as the oxidized surface before the reduction treatment, at least when the surface is observed using a microscope or SEM. When carefully compared and observed with the oxidized surface for adhesion, it appears to be slightly slender. This proves that it has excellent physical properties such as adhesive strength.

As described above, according to the method for manufacturing a multilayer board of the present invention, a multilayer printed wiring board with excellent reliability can be manufactured with high productivity and without pollution, and has extremely high industrial significance.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd.

Claims (1)

[Claims] 1. In a method for manufacturing a multilayer printed wiring board, after chemically oxidizing the copper foil surface of an inner layer board on which a printed wiring network used as an intermediate layer is formed to form a brown or black copper oxide surface,
A method for manufacturing a multilayer printed wiring board, characterized by using an inner layer board processed in an atmosphere containing hydrazine gas. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the pressure of the hydrazine gas is 50% or less of the saturated vapor pressure at the processing temperature.