JPS64469B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a stripping solution for stripping tin or tin alloys without attacking the substrate. Conventional techniques and their problems In order to peel off a tin alloy layer such as solder formed on a base material by a method such as plating, acidic ammonium fluoride or hydroborofluoric acid is conventionally used as the main component.
A stripping solution prepared by adding a hydrogen peroxide solution or the like is used as needed. However, such a stripping solution has a drawback that it is highly corrosive to the base material, and, for example, when copper is used as the base material, a large amount of the copper of the base material is also dissolved. Furthermore, acidic ammonium fluoride and hydroborofluoric acid are dangerous because they are deleterious substances, and there are various regulations regarding their handling. In addition, fluoride is
In general, it has a strong effect of corroding glass, and when peeling off the solder layer formed on a copper-clad laminate using an epoxy glass cloth base material, the glass cloth base material is corroded, causing delamination and adhesion to the laminate. Another problem is that defects are likely to occur. Means for Solving the Problems The present inventor has conducted extensive research in order to find a stripping solution that can strip tin or tin alloy without damaging the base material and is less dangerous in handling. As a result, the main component is a normal inorganic acid, to which at least one of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, sulfamic acid, and salts thereof is added as a chelating agent for chelating the dissolved metal, and further A stripping solution containing at least one of thiourea and thiourea derivatives as an inhibitor to prevent dissolution of the base material hardly attacks the base material when the base material is copper, copper alloy, or stainless steel. It has been found that tin or tin alloy can be peeled off, and there is also less danger in handling. That is, the present invention provides (i) 10 to 500 g of an inorganic acid, (ii) 1 to 100 g of at least one of monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, sulfamic acids, and salts thereof, and (iii) thiourea. and at least one thiourea derivative
This invention relates to a tin or tin alloy stripping solution containing 0.1 to 5 g/g of seeds. In the present invention, a common inorganic acid is used as the main component for stripping tin or a tin alloy. Examples of such inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid. These inorganic acids can be used alone or in combination, and the amount used is 10 to 500 g. If the amount used is less than 10 g/l, the peeling rate of tin or tin alloy will be insufficient, while if it exceeds 500 g/l, corrosion against the base material will increase, which is not preferable. In the stripping solution of the present invention, at least one of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, sulfamic acid, and salts thereof is used as a chelating agent in order to stabilize the dissolved metal in the stripping solution.
100g/use. By using such a chelating agent, precipitation due to dissolved metals is less likely to occur, and therefore the life of the stripping solution is significantly extended. If the amount of the chelating agent used is less than 1 g/l, the chelating power will be insufficient, whereas if it exceeds 100 g/l, the chelating agent itself will often not be completely dissolved in the liquid, which is unfavorable. Examples of monocarboxylic acids that can be suitably used in the present invention include glycolic acid, propionic acid, stearic acid, and lactic acid. Examples of dicarboxylic acids include oxalic acid, succinic acid, d-tartaric acid, and adipic acid. Tricarboxylic acids include citric acid, benzenetricarboxylic acid, 2,3,4-
Examples include pyridinetricarboxylic acid. In addition, as salts of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid or sulfamic acid,
Any soluble salt such as Na salt or K salt can be used. In the present invention, at least one of thiourea and thiourea derivatives is used as the inhibitor for preventing erosion of the substrate. The amount of these inhibitors used may be in the range of 0.1 to 5 g/,
If the amount used exceeds 5 g/l, the peeling rate of tin or tin alloy decreases, which is not preferable. In the present invention, by using the above-mentioned inhibitor, corrosion of the base material is significantly suppressed, and it has become possible to use a large amount of inorganic acid without attacking the base material. Therefore, the stripping solution of the present invention has a very high stripping rate. Examples of thiourea derivatives suitable for use in the present invention include allylthiourea, dimethylthiourea, trimethylthiourea, acetylthiourea, and the like. The stripping solution of the present invention is a stripping solution for immersion, and tin or a tin alloy can be stripped by immersing a sample in the solution. With this stripping liquid, the rate of stripping tin or tin alloy can be increased as the temperature at which it is used increases. However, it also increases the erosiveness of the base material, so it is usually
It is preferable to use it at about ~40°C. The stripping solution of the present invention is used for tin or a tin alloy, and examples of the tin alloy include tin-lead alloys such as 6:4 solder and 9:1 solder. In addition, when using the stripping solution of the present invention, base materials whose corrosion is suppressed include copper, copper alloys, chromium-based stainless steels such as 13Cr and 18Cr, and nickel-chromium stainless steels such as 18-8 series and 19-12Mo series. Examples include stainless steel. Effects of the Invention The stripping agent of the present invention provides the following remarkable effects. When the base material is copper, copper alloy, stainless steel, etc., tin or tin alloy can be peeled off without damaging the base material. There is less danger when using it compared to conventional stripping solutions that use fluoride. The use of specific inhibitors allows the use of large amounts of acid without attacking the substrate, so that the stripping solution of the invention has a very high stripping rate. The use of specific chelating agents makes the dissolved metals stable in the stripping solution, and thus the stripping solution of the present invention has a long life. Since the stripping solution of the present invention does not use fluoride, it hardly attacks the glass substrate. EXAMPLES The present invention will be explained in detail with reference to Examples below. Examples 1 to 5 and Comparative Examples 1 to 8 A film with a thickness of 0.3 mm and a size of 50 x 100 mm was
When a sample with a 10μm solder coating (tin: lead = 6:4) is immersed in the stripping solution shown in Table 1 at 25°C, the solder coating will completely peel off. The time required for this was measured. In addition, the corrosion rate of the copper plate was measured when the same copper plate as described above was immersed in a stripping solution at 25° C. for 10 minutes without forming a plating film. The erosion rate is expressed by the following formula. Erosion rate (%) = Weight before immersion - Weight after immersion / Weight before immersion x
100 Peeling time and erosion rate are shown in Table 1.

【table】

[Table] It is clear from Table 1 that the release agent of the present invention has a high peeling rate and low corrosiveness to the substrate. On the other hand, when the main ingredients are acidic ammonium fluoride or hydroborofluoric acid and the inhibitor used in the present invention is added to them,
The peeling rate of the plating film was slow, and the erosion rate of the base material was high. Furthermore, even with a peeling agent containing peroxide, the peeling rate of the film was slow and the rate of erosion of the base material was high. Example 6 A copper plate on which a tin plating film was formed was used instead of a solder plating film, and the tin plating film was removed in the same manner as in Example 1. The attached film was completely peeled off. Furthermore, the surface of the copper plate after peeling was glossy and hardly etched. Comparative Example 9 Using a stripping solution consisting of 300 g of acidic ammonium fluoride, 100 g of hydrogen peroxide (35%), 30 g of succinic acid, and 2 g of imidazole,
A copper plate with the same solder as in Example 1 was heated at 25°C.
When immersed in water for 5 minutes, the solder was completely dissolved, but the exposed copper surface was etched and lost its luster. Example 7 and Comparative Example 10 The same solder-plated copper plate as in Example 1 was used as a sample, and the solder-plated film was continuously melted.
The peeling speed of the solder plating film on the copper plate was measured when the amount of solder dissolved in the stripping solution was 50g/100g/. In the stripping solutions of the present invention in Examples 1 to 5, the amount of solder dissolved was
Although it was possible to remove the solder-plated film even when the solder dissolution amount was 100 g/1, white precipitates were formed in the stripping solution of Comparative Example 9 when the solder dissolution amount exceeded 50 g//. , the peeling speed decreased significantly and peeling became impossible.

[Claims]

1 A pair of parallel plate electrodes are placed in a vacuum container,
In the dry etching apparatus, the object to be processed is fixed to one of the parallel plate electrodes, and the object to be processed is etched by applying high frequency power to the electrode while introducing an etching gas into the vacuum container. CF ₄ is used as the gas, and a control device for controlling the pressure and flow rate of the etching gas in the vacuum container is installed in the middle of the introduction pipe that introduces this etching gas. A dry etching apparatus characterized in that the etching gas pressure in the vacuum container is controlled to 400 Pa and the residence time of the etching gas is controlled to 4 seconds or more.