JPH0520520B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a stripping solution and a method for stripping an alloy plating layer made of nickel and phosphorus, and more specifically, to a stripping solution and a method for stripping an alloy plating layer made of nickel and phosphorus. The present invention relates to a stripping solution and a stripping method that can easily strip an alloy plating layer made of nickel and phosphorus without damaging copper or copper alloy. [Prior Art] Generally, plating removal methods can be broadly classified into three types: mechanical separation methods, chemical separation methods, and electrochemical separation methods. The mechanical peeling method is a method of scraping off the plating layer by polishing, etc., and the chemical peeling method is a method of dissolving the plating layer on it without dissolving the material. The method involves performing constant potential electrolysis in a stripping solution to dissolve only the plating layer without dissolving the material. The various plating layers are peeled off by selecting one of the above-mentioned peeling methods depending on the combination or shape of the material on which the plating layer is provided. Although mechanical peeling methods are used for various types of plating, it is difficult to use for products that require dimensional accuracy because there is a risk of scraping the surface of the material that is the base of the plating. , cannot be applied to articles with complex shapes. In addition, chemical peeling methods are performed on plating layers such as copper plating layer, gold plating layer, nickel plating layer, chrome plating layer, etc. For example, chrome plating layer on copper material When immersed in hydrochloric acid, it reacts violently and is removed in a short period of time. Although this method is effective for peeling off the plating layer on articles with complex shapes, it There are many cases where there is no suitable stripping solution for some combinations of metals. Furthermore, the electrochemical peeling method, like the chemical peeling method described above, is applied to various plated layers such as copper plated layer, gold plated layer, nickel plated layer, etc.
It is excellent in that it can be peeled off relatively quickly, but if the shape of the object is complex, it will not be possible to peel it off evenly unless the shape of the counter electrode is selected appropriately. It has the disadvantage of being expensive. Similar to the chemical stripping method, this method also requires selecting a stripping solution depending on the combination of the plated metal and the raw metal, and appropriately controlling conditions such as the electrolytic method and electric potential. Next, I will explain about the peeling of the alloy plating layer made of nickel and phosphorus.Since this alloy plating made of nickel and phosphorus has excellent corrosion resistance, abrasion resistance, and heat resistance, it can be removed by electrolytic method or non-electrolytic method. It is provided in various products by the electrolytic method, and is used, for example, in various mechanical parts, lead frames, casting molds for steel, etc. If these products have poor plating during manufacture or if they are to be replated after use, it is necessary to remove the alloy plating made of nickel and phosphorus without damaging the material. The mechanical peeling method involves polishing with a file, sandpaper, etc., but since the hardness of the nickel and phosphorus alloy plating layer is high at Hv600-1100, it requires a long time and may damage the material. There is. Therefore, chemical stripping methods are widely used as a method for stripping alloy plating layers made of nickel and phosphorus, and several types of stripping solutions are commercially available. These removers are strongly alkaline,
When used, the article is immersed at a high temperature of around 90°C to peel off the alloy plating layer made of nickel and phosphorus. This chemical peeling method has the advantage that it can be peeled off regardless of the shape of the article on which the alloy plating layer made of nickel and phosphorus is applied, and it also requires special equipment such as a power supply. Although it has the advantage that it is not necessary, the peeling speed is slow at 10 μm per hour even at the maximum value at the time of bath preparation, and it takes a long time to peel off products with plating of several tens of μm such as casting molds. do. Also,
The problem is that the stripping solution naturally wears out at room temperature, and when it is used at high temperatures, it decomposes and wears out even more rapidly, reaching the end of its service life in a short period of time. Further, the electrochemical peeling method has never been used to peel off an alloy plated layer consisting of nickel and phosphorus, but it has been used to peel off a nickel plated layer. This method involves anodic electrolysis in 50 volume % sulfuric acid, and when this method was applied as is to peeling off an alloy plating layer made of nickel and phosphorus on a copper plate, the surface of the plating layer turned black and a layer of 20 μm thick was applied.
It took about 4 hours to peel off the alloy plating layer made of nickel and phosphorus, and the copper base surface was rough. Therefore, the electrochemical peeling method of the nickel plated layer is not suitable for peeling off the alloy plated layer consisting of nickel and phosphorus. As an example, Japanese Patent Publication No. 60-056800 and Japanese Patent Application Laid-open No. 59-166700 describe electrolytic peeling of a plated layer, but both of them describe a method for peeling an alloy plated layer made of nickel and phosphorus. do not have. [Problems to be Solved by the Invention] The present invention has been developed in view of the various problems in the methods for peeling off various plated layers described above and the problems in the method for peeling off alloy plated layers made of nickel and phosphorus. As a result of intensive research and repeated consideration by the inventor, the problems of conventional chemical peeling methods, electrochemical peeling methods, etc. were resolved, and the peeling speed was high without damaging the base material of copper and copper alloys. In addition, we have developed a long-life stripping solution and a stripping method for alloy plating layers made of nickel and phosphorus that do not cause natural consumption of the stripping solution. [Means for Solving the Problems] The stripping solution and stripping method for the alloy plating layer made of nickel and phosphorus according to the present invention are as follows: (1) 50 to 70 wt% sulfuric acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid. The first invention is a stripping solution for an alloy plating layer consisting of nickel and phosphorus on copper or copper alloy, characterized in that it contains 1 to 15 g of at least one chloroacetic acid selected from (2) sulfuric acid. Potential of an article provided with a plating layer relative to the stripping solution in a stripping solution containing 50 to 70 wt% and 1 to 15 g of at least one type of chloroacetic acid selected from monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid. is measured, and the potential is accurately regulated to be above the potential at which the alloy plating layer consisting of nickel and phosphorus dissolves, and below the potential at which copper or copper alloy dissolves, and then,
A second invention provides a method for peeling off an alloy plating layer consisting of nickel and phosphorus on copper or copper alloy, which is characterized by carrying out anodic electrolysis, (3) 50 to 70 wt% sulfuric acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid. In a stripping solution containing 1 to 15 g of at least one type of chloroacetic acid selected from acetic acids, the potential of the article provided with the plating layer relative to the stripping solution is measured, and the potential is determined by measuring the potential of the article provided with the plating layer relative to the stripping solution. on copper or copper alloy, which is characterized by carrying out anodic electrolysis at a potential higher than the potential at which the alloy plated layer is eluted, and in a range where the copper or copper alloy becomes passivated and is difficult to elute. This invention consists of three inventions, with the third invention being a method for peeling off an alloy plating layer made of nickel and phosphorus. A stripping solution and a stripping method for an alloy plating layer made of nickel and phosphorus according to the present invention will be described in detail below. First, a stripping solution for an alloy plating layer made of nickel and phosphorus according to the present invention will be explained. If the sulfuric acid concentration is less than 50wt%, it is difficult to passivate the copper or copper alloy, and if stripping is performed at this concentration, the alloy plating layer consisting of nickel and phosphorus will be dissolved and removed, and the base material will be removed. Copper or copper alloys may be eluted and corrode the base surface, so it cannot be used in products that require dimensional accuracy, and electric current cannot be used in high-concentration sulfuric acid exceeding 70wt%. It becomes difficult to flow and the peeling speed decreases. Therefore, the sulfuric acid concentration is set at 50 to 70 wt%. The reason why chloroacetic acid is included in the stripping solution is to shift the elution potential (the potential at which the metal begins to dissolve) of the alloy plating layer consisting of nickel and phosphorus to the negative side. This is because the potential difference between the elution potential of copper or copper alloy is increased, and the potential difference between the elution potential of the alloy plating layer consisting of nickel and phosphorus and the elution potential of copper or copper alloy is increased. Anodic electrolysis is now possible, and only the nickel and phosphorus alloy plating layer can be peeled off without damaging the base surface of the copper or copper alloy. This chloroacetic acid has the effect of increasing the dissolution rate of the nickel and phosphorus alloy plating layer itself by preventing the blackening of the nickel and phosphorus alloy plating layer. If the chloroacetic acid is less than 1 g/ml, the above effect cannot be obtained, and even if the chloroacetic acid is contained in a large amount exceeding 15 g/ml, the above effect will be saturated. Therefore, the chloroacetic acid content is 1 to 15 g/
shall be. In addition, as chloroacetic acid, monochloroacetic acid,
There are dichloroacetic acid and trichloroacetic acid. The method of peeling off an alloy plating layer made of nickel and phosphorus according to the present invention will become clear from the following examples. [Example] An example of a stripping solution and a stripping method for an alloy plating layer made of nickel and phosphorus according to the present invention will be described. Example 1 Five copper alloy plates (25 mm x 50 mm x 1 mm) consisting of 3.2 wt% Ni, 0.7 wt% Si, 0.3 wt% Zn, and the balance Cu, and an alloy plating layer consisting of nickel and phosphorus on these plates. Prepare 5 boards with a 50 μm gap, mask all but 1 cm ² with epoxy paint, and then apply 30 wt.
Potential-current curves of alloy plating layers made of copper alloy, nickel, and phosphorus were measured in five types of solutions containing 50 wt%, 50 wt%, 70 wt%, 80 wt% sulfuric acid, 70 wt% sulfuric acid, and 5 g of trichloroacetic acid. . Figure 1 shows 5g of trichloroacetic acid in 70wt% sulfuric acid/
The potential-current curve in a solution containing . In addition, when carried out using the second invention (shown in FIG. 1A) of the stripping solution and stripping method for an alloy plating layer made of nickel and phosphorus according to the present invention, the Ni-P
However, since the potential range is small, there is a risk that the stripping solution may change during actual use and fall outside this potential range. In addition, in the third invention of the stripping solution and stripping method for an alloy plating layer made of nickel and phosphorus (indicated by B in FIG. 1), Ni-P is eluted and Cu is
becomes passivated and dissolves in a very small amount, but as can be seen from the fact that the vertical axis in Figure 1 is expressed as a logarithm,
Since the elution amounts of Ni--P and Cu differ by more than two orders of magnitude, approximately only Ni--P plating is eluted, and Cu is not eluted. Moreover, since this range is wide, it has the advantage of being easy to carry out in practice. As a comparative example, Figure 3 shows 30wt% sulfuric acid,
The figure shows potential-current curves in 50wt% sulfuric acid, Figure 5 in 70wt% sulfuric acid, and Figure 6 in 80wt% sulfuric acid. In Figures 3 to 6, the lower the sulfuric acid concentration, the less passivation of the copper alloy progresses, and the current value at 0.8V is 30wt%, 50wt%, 70wt%,
2.50A/dm ² as it increases to 80wt%,
They are smaller at 1.02A/dm ² , 0.07A/dm ² , and 0.01A/dm ² . Therefore, if the sulfuric acid concentration is low, there is a risk of damaging the base copper alloy. 5g of trichloroacetic acid/70wt% sulfuric acid in Figure 1
The potential-current curve in the solution dissolved in
Comparing the potential-current curves in 70wt% sulfuric acid,
By containing 5 g/trichloroacetic acid, the difference in elution potential between the alloy plating layer consisting of nickel and phosphorus and the copper alloy becomes large. That is, in FIG. 5, the elution potential of the copper alloy is -
0.07V, and the elution potential of the alloy plating layer consisting of nickel and phosphorus is -0.15V, whereas the elution potential of the copper alloy in Fig. 1 is -0.05V, and the elution potential of the alloy plating layer consisting of nickel and phosphorus is -0.15V. Elution potential is -
0.30V, and the elution potential difference of the alloy plating layer consisting of copper alloy, nickel, and phosphorus is 0.08V to 0.25V.
It's getting bigger. For this reason, only the alloy plating layer consisting of nickel and phosphorus can be selectively removed by electrolysis at a potential higher than the elution potential of the alloy plating layer consisting of nickel and phosphorus and lower than the elution potential of the copper alloy. can be eluted. Example 2 A 20 μm alloy plating layer consisting of nickel and phosphorus was provided on the same copper alloy plate as in Example 1, and the thickness was 1 cm ²
Masking was performed using epoxy paint except for the area. A plurality of these test pieces were prepared, and constant potential electrolysis was carried out in a solution containing sulfuric acid, trichloroacetic acid, etc. shown in Table 1 by regulating the potential of the article serving as an anode. The time until it was eluted and disappeared was measured. FIG. 2 shows the change in current value during constant potential electrolysis of No. 3, No. 4 and No. 10 in Table 1 with respect to time. Assuming that the influence of sulfuric acid concentration is constant at 5g/trichloroacetic acid, 30wt%, 50wt%, 70wt%, 80wt%
The peeling time and the condition of the copper alloy substrate surface after peeling were observed by changing the sulfuric acid concentration. No. 8 with a sulfuric acid concentration of 30wt% has a short peeling time, but
The copper alloy surface was also partially eluted and the surface condition was poor. In addition, the sulfuric acid concentration of No. 1 and No. 3 was 50 wt%,
In the case of 70 wt%, the peeling time was short and the substrate surface condition was good. For No. 9 with a sulfuric acid concentration of 80 wt%, the peeling time was as long as 21 minutes. This indicates that, as shown in Example 1, when the concentration of sulfuric acid is low, the copper alloy is also eluted, making the surface of the substrate rough, and when the concentration of sulfuric acid is high, it becomes difficult for current to flow. Next, we examined the effect of trichloroacetic acid content by keeping the sulfuric acid concentration constant at 70 wt%, 0 g/, 1 g/
, 5 g/, 15 g/, and 20 g/, and the peeling time and the surface condition of the copper alloy base after peeling were observed. As shown in Table 1, No.10, No.2, No.3, No.
4. As the amount of No. 11 and trichloroacetic acid was increased, the peeling time became shorter, but No. 4 and No. 11 were almost the same. In addition, in No. 10, which did not contain trichloroacetic acid, the alloy plating layer made of nickel and phosphorus remained blackened and was not completely peeled off. This shows that the peeling rate increases by containing trichloroacetic acid, and that the effect remains constant regardless of the amount of trichloroacetic acid at 15 g/or more. Also, looking at Figure 2, which shows the results for No. 10, No. 3, and No. 4, as the amount of trichloroacetic acid increases, the current value after the start of electrolysis increases, and the current decreases. This indicates that the alloy has become easier to flow, indicating that trichloroacetic acid has the effect of preventing the blackening of the alloy plating layer consisting of nickel and phosphorus and promoting elution. The above explanation explains that the peeling of the alloy plating layer made of nickel and phosphorus is caused by the copper alloy becoming passivated at a potential higher than the elution potential of the alloy plating layer made of nickel and phosphorus, which is a potential range of +0 that is difficult to elute. This is the case when done at .30V. Next, No. 5 shows an example in which constant potential electrolysis was carried out by keeping the potential of the article at -0.10V, which is above the elution potential of the alloy plating layer consisting of nickel and phosphorus and below the elution potential of the copper alloy. Indicated. The peeling time was 13 minutes, which is a short time compared to other examples, and since electrolysis was performed at a potential that did not cause copper alloy elution, the substrate surface after peeling was good. As described above, the stripping solution and stripping method for an alloy plated layer made of nickel and phosphorus according to the present invention can be electrolyzed at an elution potential higher than the elution potential of the alloy plated layer made of nickel and phosphorus and less than the elution potential of the copper alloy. 2
However, in actual stripping work, the composition of the stripping solution changes due to the influence of dissolved metal ions, etc. while the stripping solution is being used. In the second invention of the stripping solution and stripping method for an alloy plating layer made of nickel and phosphorus according to the present invention, the potential range that can be stripped is narrow because the anode potential changes. Therefore, in actual stripping work, the anode potential during electrolysis must be higher than the elution potential of the alloy plating layer consisting of nickel and phosphorus, and the copper or copper alloy becomes passivated and difficult to elute. It is preferable to use the third invention of the stripping solution and stripping method for an alloy plating layer made of nickel and phosphorus according to the present invention, which is carried out within a certain range, since it is less susceptible to changes in the composition of the stripping solution. Next, to explain examples of dichloroacetic acid and monochloroacetic acid, No. 6 is the case where 1 g/dichloroacetic acid was dissolved in 70 wt% sulfuric acid and electrolysis was performed while keeping the potential at +0.30V. This is the case where 5 g/monochloroacetic acid was dissolved in the same manner as No. 6. In any of these cases, as in the case of trichloroacetic acid, it is clear that the stripping time is shorter than in the case where dichloroacetic acid and monochloroacetic acid are not included. Further, even if dichloroacetic acid and monochloroacetic acid are used in combination, it is not considered that there is any intermolecular interaction between the two chloroacetic acids, and the effects are synergistic.

【table】

[Table] Example 3 An alloy plating layer (30 μm thick) made of nickel and phosphorus was applied as the first layer to the inner surface of the continuous casting pipe mold (134 mm x 800 mm, wall thickness 8 mm) made of the copper alloy shown in Example 1. ), cobalt plating layer (1μm) as the second layer, chrome plating layer (20μm) as the third layer
Two used molds were prepared. After melting and peeling off the third chrome plating layer of these two molds in 1:1 hydrochloric acid at a temperature of 30°C, one mold was in 70wt% sulfuric acid and the other was in the second mold.
Using the platinum-plated titanium electrode that was used when electroplating the alloy plating layer consisting of nickel and phosphorus in the stripping solution No. 3 in the table as the cathode, the potential of the mold was raised to +0.30V. After confirming this using a reference electrode, constant potential electrolysis was performed. As a result, after 4 hours of electrolysis in 70wt% sulfuric acid, when the inner surface of the mold was observed, some of the copper substrate was exposed, but an alloy plating layer consisting of nickel and phosphorus remained, and the surface had turned black. On the other hand, 5 g of trichloroacetic acid was dissolved in
During electrolysis in 70wt% sulfuric acid, the current value dropped to 5A 30 minutes after the start, and when the inner surface of the mold was observed, the alloy plating layer consisting of nickel and phosphorus had completely eluted, and the copper base was exposed. . moreover,
The inner surface of the copper alloy mold clearly remained after polishing before plating, and no signs of elution were observed. [Effects of the Invention] As explained above, since the stripping solution and the stripping method for the alloy plating layer made of nickel and phosphorus according to the present invention have the above configuration, the alloy plating layer made of nickel and phosphorus is provided. When re-plating due to poor plating during the manufacture of an article or after use, an alloy plating layer consisting of nickel and phosphorus can be applied over a short period of time without damaging the base copper or copper alloy. It has the excellent effect of being able to be peeled off.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between anode potential and current, Figure 2 is a diagram showing the relationship between time and current, and Figures 3 to 6 are diagrams showing the relationship between anode potential and current in comparative examples. be.

Claims (1)

[Claims] 1. 50 to 70 wt% sulfuric acid, at least one type of chloroacetic acid selected from monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid 1
A stripping solution for an alloy plating layer consisting of nickel and phosphorus on copper or copper alloy, characterized in that it contains ~15 g/. 2 50 to 70 wt% sulfuric acid, at least one type of chloroacetic acid selected from monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid 1
Measure the potential of the article provided with the plating layer with respect to the stripping solution in a stripping solution containing ~15 g/ , and set the potential to a potential higher than the potential at which the alloy plating layer consisting of nickel and phosphorus elutes, and A method for peeling off an alloy plating layer consisting of nickel and phosphorus on copper or copper alloy, which comprises carrying out anodic electrolysis while accurately controlling the potential to be below the potential at which copper or copper alloy elutes. 3 50-70wt% sulfuric acid, at least one type of chloroacetic acid selected from monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid 1
Measure the potential of the article provided with the plating layer with respect to the stripping solution in a stripping solution containing ~15 g/ , and set the potential to a potential higher than the potential at which the alloy plating layer consisting of nickel and phosphorus elutes, and A method for peeling off an alloy plating layer consisting of nickel and phosphorus on copper or copper alloy, which comprises carrying out anodic electrolysis while accurately regulating the potential within a range in which copper or copper alloy is passivated and difficult to elute.