JPS6214035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an etching agent for nickel thin films. Currently, the commonly used printed circuit boards are:
A pattern etching resist is applied using solder or photoresist on a copper-clad laminate with a thickness of several tens of microns, and the copper in areas not covered by the resist is dissolved and removed using various methods to obtain the desired copper circuit pattern. . However, there are many disadvantages such as the need to dissolve and remove a large amount of copper.
For this reason, various improvements and developments have recently been made in the production of printed circuit boards. One of these is a printed circuit board in which electroless nickel plating is performed directly on the substrate to form a nickel thin film, and only a copper circuit pattern of several tens of microns is provided on the surface by electrolysis. The present invention relates to an etching agent for such a substrate, and the purpose of etching such a substrate is to dissolve and remove the nickel thin film that is not covered by the copper pattern. Since there is no etching resist, selective etching is required to suppress corrosion of the copper pattern as much as possible and dissolve and remove only the nickel thin film. The present inventors have previously discovered that a system consisting of an acid such as sulfuric acid, hydrogen peroxide and free chlorine ions is an etching agent that can advantageously carry out the above purpose. For example, hydrogen peroxide 100g/, sulfuric acid 100g/
A system in which 200 ppm of ammonium chloride is added to a solution with the composition can suppress the dissolution rate of copper to 1/15 or less at 30°C compared to a system without ammonium chloride. The dissolution rate of nickel is almost constant regardless of whether ammonium chloride is added or not. However, the above-mentioned etching agent consisting of acid, hydrogen peroxide, and free chlorine ions does not necessarily have a sufficient effect of suppressing copper corrosion, and it is necessary to precisely control the processing conditions and operations. The present inventors have completed the present invention based on the above-mentioned etching agent, and have further conducted research on an etching agent that inhibits corrosion of copper. That is, the present invention provides a solution containing an acid selected from the group consisting of sulfuric acid, nitric acid, and phosphoric acid, hydrogen peroxide, and free chlorine ions, and a compound having a tertiary amine and a polyoxyalkylene group (with a degree of polymerization of 1 to 3). The present invention relates to an etching agent for electroless nickel thin films, characterized in that it contains a compound selected from the group consisting of polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, and pyrrole. The concentrations of acid, hydrogen peroxide and free chlorine ions used in the present invention are 0.1 to 50% by weight and 0.1% by weight, respectively.
It can be selected within the range of ~50% by weight and 2~20000ppm. The concentration of each component cannot be determined unconditionally based on the thickness of the nickel thin film, the allowable amount of dissolution of the copper pattern, the desired processing time, etc., but from the viewpoint of operability etc., acid, hydrogen peroxide and The concentration range of free chlorine ions is 1 to 30% by weight, respectively.
1 to 30% by weight and 5 to 5000 ppm. Compounds such as tertiary amines, compounds having polyoxyalkylene groups (excluding polyethylene glycol with a degree of polymerization of 1 to 3), polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, and pyrrole (hereinafter, when referring to all compounds collectively, simply add (referred to as agent) is 0.5 g/ or more, preferably 1.0 to 30 g/. Further, the treatment temperature is 5 to 60°C, preferably 10 to 40°C. Although the mechanism of why copper corrosion is suppressed by adding the above additive to a system consisting of acid, hydrogen peroxide, and free chlorine ions is not clear,
It is thought that corrosion is suppressed due to the adsorption of the additive to the copper surface and the interaction between the additive and chlorine ions. The tertiary amines used in the present invention include triethylamine, tripropylamine, tributylamine, triamylamine, trihexylamine, trioctylamine, N,N-dimethylbenzylamine, N,N-dibenzylaniline, , N-dibutylaniline and N,N-diethylcyclohexylamine. Compounds having a polyoxyalkylene group (excluding polyethylene glycol with a degree of polymerization of 1 to 3) include polyethylene glycol with a degree of polymerization of 4 or more, polypropylene glycol, polyethylene glycol lauryl ether, polyethylene glycol nonylphenyl ether, polyethylene glycol oleyl ether, Polyethylene glycol stearyl ether, diethylene glycol diethyl ether, polyethylene glycol monostearate, polyethylene glycol distearate,
These include polyethylene glycol monolaurate, polyethylene glycol oleate, polyethylene glycol sorbitan monolaurate, polyethylene glycol sorbitan monostearate, polyethylene glycol monooleate, and polyethylene glycol stearylamine. Polyvinyl ether includes polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl isobutyl ether, and the like. Substances that provide free chloride ions used in the present invention include a wide range of water-soluble chlorides and inorganic and organic compounds that substantially release chloride ions in solution. Unless specifically desired, hydrogen peroxide may be used. It is desirable to use chlorides that are inert to the decomposition of . It is desirable to avoid as much as possible the use of metal chlorides that act as hydrogen peroxide decomposition catalysts and noble metal chlorides that tend to ionize more than copper and cause precipitation on the surface of the copper pattern. Compared to the above additives used in the present invention, they are slightly less effective, but include ethers such as ethyl ether and propyl ether, amides such as propionic acid amide and adipic acid amide, imines such as piperidine, diethyl adipate, and sorbitan monomer. rate,
It was also confirmed that esters such as 2-ethoxyethyl acetate, acetone, ketones such as p-methylacetophenone, and pyridine are substances that contribute to inhibiting copper corrosion. The etching process can be carried out by simply immersing the printed circuit board in the etching agent of the present invention, or by spraying the etching agent onto the printed circuit board. Continuous processing is also possible under controlled conditions, such as by appropriately replenishing solution components consumed by the etching process. According to the present invention, not only can the nickel thin film be completely dissolved and removed by a short etching process of several tens of seconds to several minutes, but the corrosion of the copper pattern portion is extremely small, resulting in extremely reliable etching. A highly completely etched substrate can be obtained. In addition, the additive used in the present invention also acts as a hydrogen peroxide stabilizer to stabilize the solution and extend the bath life. The present invention provides an etching agent which has many practical values such as ease of recovery of nickel and copper and the fact that it does not cause pollution problems. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 A solution consisting of 100 g of sulfuric acid, 100 g of hydrogen peroxide, and 200 ppm of ammonium chloride was prepared, and various additives were added to it at 1% (in the case of liquid, v/
v%, wt/v% in case of solid), and heated at 30°C.
The dissolution rate of copper for 5 minutes was measured, and the corrosion inhibition rate was calculated from the obtained value based on the following formula. Corrosion inhibition rate (%) = (1-r/r ₀ ) × 100 (r ₀ and r indicate the dissolution rate of copper without and with additives) Corrosion inhibition based on the above formula Find the ratio A to D
Ranked in four stages. The results are shown in Table 1. The A-ranked one is the present invention.

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【table】

【table】

[Table] The dissolution rate of nickel in the above composition of sulfuric acid, hydrogen peroxide and ammonium chloride was 0.45 μ/min when no additives were added, and was almost the same when various additives were added. Example 2 A printed circuit board with a 0.5 μ thick electroless nickel plating thin film on the entire surface and a 20 μ thick copper circuit pattern formed thereon was heated with 147 g of sulfuric acid.
Hydrogen peroxide 102g/, ammonium chloride
200ppm and tri-n-amylamine 10g/
A solution with the composition of 30℃, spray pressure 1.5Kg/
As a result of spray etching at cm ² , the nickel thin film could be completely removed in about 60 seconds. Moreover, the amount of dissolution of the copper pattern portion during this period was extremely small. Example 3 The same printed circuit board as Example 1 was treated with nitric acid 63g/,
Hydrogen peroxide 102g/, ammonium chloride
As a result of immersion treatment at 30℃ in a solution consisting of 200ppm and polyethylene glycol (#600), the nickel thin film could be completely removed in about 90 seconds, and the amount of copper pattern dissolved during this time was There were very few. Example 4 The same printed circuit board as in Example 1 was treated with 98 g of phosphoric acid/
, hydrogen peroxide 102g/, ammonium chloride
As a result of spray etching with a solution consisting of 200 ppm and 10 g of pyrrole at 30°C and a spray pressure of 1.5 kg/ ^cm2 , the nickel thin film was approximately 3.
It was possible to completely remove it within minutes, and the amount of dissolution of the copper pattern portion during this time was extremely small. Example 5 The same printed circuit board as in Example 1 was treated with 98 g of sulfuric acid/
Phosphoric acid 49g/, hydrogen peroxide 102g/, ammonium chloride 200ppm and polyvinylpyrrolidone
As a result of immersion treatment at 30°C in a solution with a composition of 10 g/ml, the nickel thin film could be completely removed in about 90 seconds, and the amount of copper pattern dissolved during this time was extremely small.

Claims (1)

[Claims] 1. A tertiary amine, a compound having a polyoxyalkylene group (polyethylene glycol with a degree of polymerization of 1 to 3) is added to a solution containing an acid selected from the group consisting of sulfuric acid, nitric acid, and phosphoric acid, hydrogen peroxide, and free chlorine ions. 1. An etching agent for electroless nickel thin films, characterized in that it contains a compound selected from the group consisting of polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, and pyrrole.