Patent Application
20110127168
The present invention relates to a hard gold-based plating treatment technology. In particular, the present invention relates to a hard gold-based plating solution which is suitable in forming contact materials of electronic components such as a connector and applies hard gold plating and hard gold alloy plating. The hard gold-based plating of the present application refers to either hard gold plating or hard gold alloy plating. A plating solution for applying the hard gold-based plating is referred to as a hard gold-based plating solution.
Conventionally, gold plating has been used for electronic devices and electronic components for reasons of excellent electrical properties and corrosion resistance or the like of gold, and has been widely used for an application of protecting a surface of a connecting terminal of the electronic component or the like. The gold plating is used as surface treatment of electronic components such as an electrode terminal of a semiconductor device, a lead formed on a resin film and a connector connecting the electronic device.
In the electronic components such as the connector connecting the electronic device, the gold plating is used as the surface treatment. Since corrosion resistance, abrasion resistance and electrical conductivity are required as the properties of the electronic components, the hard gold-based plating is often used. For example, hard gold alloy platings such as gold-cobalt-based alloy plating and gold-nickel-based alloy plating have been known as the hard gold-based plating through the ages (Patent Documents 1 and 2).
Copper or a copper alloy is generally used as a material for the electronic components such as the connector. Nickel plating is ordinarily applied on the surface of the copper or the copper alloy in the case of applying the hard gold-based plating, and the hard gold-based plating is then applied on the surface of the nickel plating.
When the hard gold-based plating is applied to the electronic components such as the connector, partial plating treatment is required so that the hard gold-based plating is applied to only a necessary portion. That is, the hard gold-based plating is applied to only the necessary portion, and the ungeneration of the deposition of the hard gold-based plating on an unnecessary portion is required. The reason is that when the hard gold-based plating is applied to the unnecessary portion of the connector, a solder also infiltrates the unnecessary portion to reduce electric properties in soldering treatment for electric connection. Another reason is that unless the hard gold-based plating is deposited on the unnecessary portion, the used amount of gold can be suppressed to enable the reduce amount of gold. To meet such a demand, a technology capable of selectively performing hard gold-based plating treatment on only a necessary portion is proposed (for example, Patent Document 3).
A gold-cobalt alloy plating solution of the conventional technique is used to deposit a gold alloy plating film on only a desired place of the electronic components such as the connector and to suppress the deposition of the gold alloy plating film on the unnecessary place. Thereby, hard gold-based plating can be applied.
Incidentally, since gold or gold alloy plating has excellent material properties, the gold or gold alloy plating is very often applied to a portion requiring electric connection in the current electronic components. A hard gold-based plating solution selectively enabling partial plating treatment is required for various object parts. However, the types of hard gold-based plating solutions are fewer. That is, in this situation, there is need for a novel hard gold-based plating solution enabling selective partial plating treatment as proposed in Patent Document 3.
The present invention was developed in the light of the above-described situations. It is an object of the present invention to provide a hard gold-based plating solution which enables selective partial plating treatment and is suitable for electronic components such as a connector.
A hard gold-based plating solution of the present invention comprises: a soluble gold salt or a gold complex; a conductive salt; and a chelating agent, wherein the hard gold-based plating solution further comprises an aromatic compound having one or more nitro groups. When the hard gold-based plating solution comprising the soluble gold salt or the gold complex, the conductive salt, and the chelating agent further comprises the aromatic compound having one or more nitro groups, the selective partial plating treatment is enabled by hard gold-based plating.
Preferably, the hard gold-based plating solution further comprises at least one metal salt selected from a cobalt salt, a nickel salt and a silver salt. The metal salt can convert a plating film into a gold alloy to harden the film.
The hard gold-based plating solution may comprise polyethyleneimine as an organic additive in place of the metal salts such as the cobalt salt, the nickel salt and the silver salt. The polyethyleneimines having various molecular weights can be used, regardless of structures such as a straight chain structure and a branch structure. The addition of the organic additive can harden the plating film as well as the addition of the metal salt.
In the hard gold-based plating solution, the soluble gold salt or the gold complex can be used as a gold ion source. Specifically, there can be used gold(I) potassium cyanide, gold(II) potassium cyanide, gold ammonium cyanide, gold(I) potassium chloride, gold(II) potassium chloride, gold(I) sodium chloride, gold(II) sodium chloride, gold potassium thiosulfate, gold sodium thiosulfate, gold potassium sulfite, gold sodium sulfite or any combination of two or more thereof. Gold(I) potassium cyanide is particularly preferable.
The gold concentration of the hard gold-based plating solution is desirably in the range of 1 g/L to 20 g/L in terms of gold. The gold concentration of less than 1 g/L complicates treatment of the hard gold-based plating solution at a high current density, with the result that this tends to complicate high-speed plating treatment. This is because the gold concentration exceeding 20 g/L increases a drag-out loss of gold from the plating solution (A slight plating solution is attached to a connector or the like as an object to be plated, to be brought out to the next process. For example, even if several drops of the plating solution are brought out, weight loss of the gold from the plating solution is increased as the gold concentration is higher.), causing an increase in manufacturing cost. A gold salt concentration is more preferably 2 g/L to 16 g/L in terms of gold.
When the hard gold-based plating solution according to the present invention comprises the cobalt salt, a soluble cobalt compound can be used as a cobalt source. For example, cobalt sulfate, cobalt chloride, cobalt carbonate, cobalt sulfamate, cobalt gluconate and a combination of two or more thereof can be used. Preferably, the cobalt compound is an inorganic cobalt salt, and particularly cobalt sulfate.
The concentration of the cobalt salt in the plating solution is desirably in the range of 0.05 g/L to 10 g/L in terms of cobalt. The concentration of less than 0.05 g/L reduces the amount of cobalt co-deposited in the plating film, with the result that this tends not to improve the hardening of the hard gold-based plating. The concentration exceeding 10 g/L tends to reduce the stability of the plating solution. More preferably, the concentration of the cobalt salt is 0.1 g/L to 3 g/L in terms of cobalt.
When the hard gold-based plating solution according to the present invention comprises the nickel salt, a soluble nickel compound can be used as a nickel source. For example, nickel sulfate, nickel chloride, nickel carbonate, nickel sulfamate, nickel gluconate and a combination of two or more thereof can be used. The nickel compound is particularly preferably nickel sulfate.
The concentration of the nickel salt in the plating solution is desirably in the range of 0.05 g/L to 30 g/L in terms of nickel. The concentration of less than 0.05 g/L reduces the eutectoid amount of nickel in the plating film, with the result that this tends to unimprove the hardening of the hard gold-based plating. The concentration exceeding 30 g/L tends to reduce the stability of the plating solution. More preferably, the nickel concentration is 0.1 g/L to 20 g/L in terms of nickel.
When the hard gold-based plating solution comprises the silver salt, a soluble silver compound can be used as a silver source. For example, silver cyanide and a salt thereof, silver chloride, silver carbonate, silver nitrate and a combination of two or more thereof can be used. The silver compound is particularly preferably silver cyanide.
The concentration of the silver salt in the plating solution is desirably in the range of 0.05 g/L to 100 g/L in terms of silver. The concentration of less than 0.05 g/L reduces the eutectoid amount of silver in the plating film, with the result that this tends to unimprove the hardening of the hard gold-based plating. The concentration exceeding 100 g/L tends to reduce the stability of the plating solution. More preferably, the silver concentration is 0.1 g/L to 50 g/L in terms of silver.
When the hard gold-based plating solution comprises polyethyleneimine as the organic additive, the concentration of the organic additive in the plating solution is preferably 0.1 g/L to 300 g/L. The concentration of less than 0.1 g/L tends to unimprove the hardening of the hard gold-based plating. The concentration exceeding 300 g/L tends to reduce the stability of the plating solution. More preferably, the concentration is 1 g/L to 200 g/L.
Both an organic compound and an inorganic compound can be used as the conductive salt in the hard gold-based plating solution. Examples of the organic compound include a compound containing carboxylic acids such as citric acid, tartaric acid, adipic acid, malic acid, succinic acid, lactic acid and benzoic acid and salts thereof, and a phosphonate group and a salt thereof. Examples of the inorganic compound include alkali metal salts or ammonium salts of phosphoric acid, sulfurous acid, nitrous acid, nitric acid and sulfuric acid or the like, alkali cyanides and ammonium cyanide. The combination of two or more thereof can be also used.
The concentration of the conductive salt in the plating solution is desirably in the range of 0.1 g/L to 300 g/L. More preferably, the concentration is 1 g/L to 200 g/L.
A carboxyl group-containing compound and a phosphonate group-containing compound or the like can be used as the chelating agent in the hard gold-based plating solution. Examples of the carboxyl group-containing compound include citric acid, potassium citrate, sodium citrate, tartaric acid, oxalic acid and succinic acid. The phosphonate group-containing compound has a phosphonate group or a salt thereof in a molecule. Examples of the phosphonate group-containing compound include compounds having a plurality of phosphonate groups in a molecule such as aminotrimethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediamine tetramethylene phosphonic acid and diethylenetriamine pentamethylenephosphonic acid, and alkali metal salts or ammonium salts thereof. A nitrogen compound as an auxiliary chelating agent can be also used with the carboxyl group-containing compound. Examples of the nitrogen compound include ammonia, ethylene diamine and triethanolamine. The combination of two or more of the chelating agents can be also used.
The concentration of the chelating agent in the plating solution is desirably in the range of 0.1 g/L to 300 g/L. The concentration of less than 0.1 g/L tends to hinder a chelating action. The concentration exceeding 300 g/L tends to cause undissolution of the chelating agent in the plating solution. More preferably, the concentration is 1 g/L to 200 g/L.
Dinitrobenzoic acid, nitrobenzoic acid and nitrobenzene sulfonic acid can be used as the aromatic compound having one or more nitro groups in the hard gold-based plating solution. The addition of the aromatic compounds into the plating solution enables the selective partial plating treatment to effectively suppress the deposition of the hard gold-based plating on an unnecessary portion.
The concentration of the aromatic compound having one or more nitro groups in the plating solution is desirably in the range of 0.01 g/L to 30 g/L. The concentration of less than 0.01 g/L easily causes the deposition of the gold alloy plating on the unnecessary portion. The concentration exceeding 30 g/L excessively suppresses the plating deposition amount wholly, with the result that this tends to complicate the hard gold-based plating on a necessary portion. More preferably, the concentration is 0.05 g/L to 15 g/L.
The hard gold-based plating solution can comprise a pH adjuster and a buffering agent or the like in addition to the basic composition described above. Alkali metal hydroxides such as potassium citrate and potassium hydroxide, or acid materials such as citric acid and phosphoric acid can be used as the pH adjuster. Citric acid, tartaric acid, oxalic acid, succinic acid, phosphoric acid, sulfurous acid or salts thereof or the like can be used as the buffering agent.
As the plating treatment condition, the pH of the hard gold-based plating solution is preferably set to 3 or more. The plating treatment should preferably be performed at a solution temperature of 5° C. to 90° C. The pH of less than 3 tends to easily cause generation of cyanogen gas. More preferably, the plating treatment should be performed under the plating treatment condition that pH is 4 or more and a solution temperature is 20° C. to 70° C. The applicable range of a current density in the plating treatment is wide. The optimal current density value can be selected according to conditions such as an object to be plated, a plating device and a flow rate of the plating solution. The hard gold-based plating solution according to the present invention can particularly correspond to the plating treatment condition of the high current density such as high-speed plating treatment.
The hard gold-based plating treatment can be performed on only the necessary portion of the electronic components such as the connector by using the hard gold-based plating solution according to the present invention. Particularly, when the hard gold-based plating treatment is performed on a surface of nickel plating as an under layer, partial plating treatment can be selectively performed.
Hereinafter, embodiments of the present invention will be described.
The embodiment describes results of inspecting plating properties of a hard gold-based plating solution of a gold-cobalt alloy.
In Example 1, results of performing a Hull cell test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups to inspect electrodeposition properties thereof will be described. A composition of a hard gold-based plating solution was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
cobalt sulfate: 3.6 g/L (0.76 g/L in terms of cobalt)
citric acid: 150 g/L
potassium hydroxide: 20 g/L
dinitrobenzoic acid: 1 g/L, 5 g/L
pH: 4.4
solution temperature: 60° C.
In the Hull cell test, a commercially available Hull cell tester (manufactured by Yamamoto-MS Co., Ltd.) was used. A Hull cell plate made of brass (length: 70 mm, width: 100 mm, thickness: 0.3 mm) having both surfaces on which nickel plating (thickness: 10 μm) was applied was used as a base material to be plated. Plating treatment time was set to 30 seconds and a current to be energized was set to 3 A. A plating solution was strongly agitated during plating treatment.
Hull cell evaluation was performed by measuring plating film thicknesses of nine places of the plated Hull cell plate. The nine places of the Hull cell plate were selected at a predetermined interval in the width direction of the Hull cell plate in a horizontal direction at a portion (a portion dipped in the plating solution) located at the upper side by about 2 cm from the bottom of the Hull cell plate contacting the internal bottom face of the Hull cell tester.
The plating film thicknesses were measured with the fluorescent X-ray film thickness meter (manufactured by SII NanoTechnology Inc.). As an approximate current density value in each of the nine points (No. 1 to 9) at which the film thicknesses were measured, No. 1 was 0.3 A/dm2; No. 2, 1 A/dm2; No. 3, 2 A/dm2; No. 4, 3 A/dm2; No. 5, 4 A/dm2; No. 6, 5.5 A/dm2; No. 7, 7.5 A/dm2; No. 8, 10 A/dm2; and No. 9, 13.5 A/dm2. This Hull cell evaluation was performed on both the surface of the plated Hull cell plate and the rear face thereof. Results of measuring the film thicknesses of the points are shown in Table 1. The current density values of the nine places described above represent current densities on the surface side of the Hull cell plate. The current density values on the back side of the Hull cell plate are unknown. The current density values on the rear face side of the Hull cell plate are much lower than those on the surface side.
Results of a hard gold-based plating solution to which dinitrobenzoic acid is not added are also shown for comparison in Table 1. Numbers 1 to 9 shown in Table 1 represent measurement points at the nine places of the Hull cell plate. The results of columns of hyphens are the results of the hard gold-based plating solution to which dinitrobenzoic acid is not added. Each of the columns of 1 g/L, and 5 g/L represents the results of the hard gold-based plating solution containing dinitrobenzoic acid of each concentration of 1 g/L and 5 g/L (The same applies to Tables of measurement results of the film thicknesses of Hull cell plates to be shown later.). As is apparent from the measurement results of the film thicknesses of the surface of the Hull cell plate, it became clear that when dinitrobenzoic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, the plating of the low current density side is further suppressed. Furthermore, in the case of the hard gold-based plating solution to which dinitrobenzoic acid was not added, hard gold-based plating was also applied on the rear face side of the Hull cell plate. However, it further became clear that when dinitrobenzoic acid is added, the rear face side is virtually free from any plating treatment.
In Example 2, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 2 is the same as that of Example 1. The composition of Example 2 is different from that of Example 1 only in a point that nitrobenzoic acid is used in place of dinitrobenzoic acid of Example 1. A Hull cell test condition and evaluation thereof were also the same as those of Example 1. Results of measuring film thicknesses of points according to Example 2 are shown in Table 2.
As is apparent from the results shown in Table 2, it became clear that when nitrobenzoic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 3, nitrobenzene sulfonic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 3 is the same as that of Example 1 except that the former uses nitrobenzene sulfonic acid in place of dinitrobenzoic acid of Example 1. A Hull cell test condition and evaluation thereof were also same as those of Example 1. Results of measuring film thicknesses of points according to Example 3 are shown in Table 3.
As is apparent from the results shown in Table 3, it became clear that when nitrobenzene sulfonic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzene sulfonic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzene sulfonic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
Example 4 describes results of performing a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups to inspect electrodeposition properties thereof. A composition of a hard gold-based plating solution of a gold-cobalt alloy was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
cobalt sulfate: 3.6 g/L (0.76 g/L in terms of cobalt)
citric acid: 150 g/L
potassium hydroxide: 20 g/L
dinitrobenzoic acid: 0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 3.0 g/L, 5.0 g/L
pH: 4.4
solution temperature: 60° C.
In the high-speed partial plating test, a Ni-plated (thickness of 10 μm) brass plate as an object to be plated was used. In order to confirm the deposition selectivity of a gold plating film, the brass plate was fluid-tightly sealed by a silicon packing so that a circular portion having a diameter of 9 mm was in an exposed state. However, a groove (width: 2 mm, length: 20 mm, depth: 3 mm) extending from one end of the exposed circular portion was formed between nickel plating and a silicon packing mask. When the plating solution is jetted to the exposed circular portion which is not masked with the silicon packing, plating is formed on the circular portion. The plating solution passes through a gap formed in the groove portion, and is discharged from the end side of the groove portion. Since the mask exists on the upper part of the groove portion, the groove portion has a current density lower than that of the circular exposed portion on which no mask exists, at the time of electrolysis. Therefore, when this high-speed partial plating device performs plating treatment, it is ideal to perform plating treatment on only the circular portion and to perform no plating treatment on the groove portion.
As the plating treatment condition, a flow rate was controlled to 15 L/min and a current density was controlled to 50 A/dm2 to form a gold-cobalt alloy plating film having a thickness of 0.5 μm.
A plating state in the case of changing the concentration of dinitrobenzoic acid in the plating solution was externally observed. It became clear that as the added amount of dinitrobenzoic acid is increased, the groove portion is free from any plating treatment.
Then, plating film thicknesses were measured at four places of the groove portion of each of test samples plated at concentrations to inspect an average plating film thickness. The results are shown in Table 4. The plating film thicknesses were measured by a fluorescent X-ray film thickness meter (manufactured by SII NanoTechnology Inc.).
From the results of Table 4, it became clear that when the concentration of dinitrobenzoic acid in the plating solution is increased, plating treatment proceeds selectively on a circular plating portion of a substrate, and the groove portion that does not require any plating treatment is free from any plating treatment.
The embodiment describes results of inspecting plating properties of a hard gold-based plating solution of a gold-nickel alloy.
In Example 5, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
nickel sulfate: 9 g/L (2 g/L in terms of nickel)
citric acid: 150 g/L
potassium hydroxide: 20 g/L
dinitrobenzoic acid: 1 g/L, 5 g/L
pH: 4.4
solution temperature: 60° C.
A Hull cell test condition and evaluation were same as those of Example 1. Results of measuring film thicknesses of points according to Example 5 are shown in Table 5.
Results of a hard gold-based plating solution to which dinitrobenzoic acid is not added are also shown for comparison in Table 5. As is apparent from the results shown in Table 5, it became clear that when nitrobenzoic acid is added as in the case of the first embodiment, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. In the case of the hard gold-based plating solution to which dinitrobenzoic acid is not added, hard gold-based plating is also applied to a rear face side of a Hull cell plate. However, it further became clear that when dinitrobenzoic acid is added, the rear face side is virtually free from any plating treatment.
In Example 6, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 6 is the same as that of Example 5. The composition of Example 6 is different from that of Example 5 only in a point that nitrobenzoic acid is used in place of dinitrobenzoic acid of Example 5. A Hull cell test condition and evaluation thereof were same as those of Example 1. Results of measuring film thicknesses of points according to Example 6 are shown in Table 6.
As is apparent from the results shown in Table 6, it became clear that when nitrobenzoic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 7, nitrobenzene sulfonic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 7 is the same as that of Example 5. The composition of Example 7 is different from that of Example 5 only in a point that nitrobenzene sulfonic acid is used in place of dinitrobenzoic acid of Example 5. A Hull cell test condition and evaluation thereof were also same as those of Example 1. Results of measuring film thicknesses of points according to Example 7 are shown in Table 7.
As is apparent from the results shown in Table 7, it became clear that when nitrobenzene sulfonic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzoic sulfonic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzene sulfonic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 8, as in Example 4 described above, results of performing a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups to inspect electrodeposition properties thereof will be described. A composition of a hard gold-based plating solution of a gold-nickel alloy was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
nickel sulfate: 9 g/L (2 g/L in terms of nickel)
citric acid: 150 g/L
potassium hydroxide: 20 g/L
dinitrobenzoic acid: 0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 3.0 g/L, 5.0 g/L
pH: 4.4
solution temperature: 60° C.
A test sample, a device and a plating condition or the like of the high-speed partial plating test were the same as those of Example 4.
Also in Example 8, a plating state in the case of changing the concentration of dinitrobenzoic acid in the plating solution was externally observed. It became clear that as the added amount of dinitrobenzoic acid is increased, a groove portion is free from any plating treatment.
In Example 8, results of inspecting average plating film thicknesses of the groove portion as in Example 4 described above are shown in Table 8. The film thicknesses were also inspected as in Example 4.
From the results of Table 8, as in Example 4, it became clear that when the concentration of dinitrobenzoic acid in the plating solution is increased, plating treatment proceeds selectively on a circular plating portion of a substrate, and no plating treatment is performed on the groove portion that does not require any plating treatment is free from any plating treatment.
In the embodiment, results of inspecting plating properties of a hard gold-based plating solution of a gold-silver alloy will be described.
In Example 9, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
silver cyanide: 10 g/L (8 g/L in terms of silver)
potassium cyanide: 50 g/L
dinitrobenzoic acid: 1 g/L, 5 g/L
pH: 12
solution temperature: 20° C.
A Hull cell test condition and evaluation were the same as those of Example 1. Results of measuring film thicknesses of points according to Example 9 are shown in Table 9.
Results of a hard gold-based plating solution to which dinitrobenzoic acid is not added are also shown for comparison in Table 9. As is apparent from the results shown in Table 9, it became clear that when nitrobenzoic acid is added as in the case of the first embodiment, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when dinitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which dinitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 10, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 10 is the same as that of Example 9. The composition of Example 10 is different from that of Example 9 only in a point that nitrobenzoic acid is used in place of dinitrobenzoic acid of Example 10. A Hull cell test condition and evaluation thereof were the same as those of Example 1. Results of measuring film thicknesses of points in Example 10 are shown in Table 10.
As is apparent from the results shown in Table 10, it became clear that when nitrobenzoic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 11, nitrobenzene sulfonic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 11 is the same as that of Example 9. The composition of Example 11 is different from that of Example 9 only in a point that nitrobenzene sulfonic acid is used in place of dinitrobenzoic acid of Example 9. A Hull cell test condition and evaluation thereof were also the same as those of Example 1. Results of measuring film thicknesses of points in Example 11 are shown in Table 11.
As is apparent from the results shown in Table 11, it became clear that when nitrobenzene sulfonic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzene sulfonic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzene sulfonic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 12, as in Example 4, results of performing a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups to inspect electrodeposition properties thereof will be described. A composition of a hard gold-based plating solution of a gold-silver alloy was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
silver cyanide: 10 g/L (8 g/L in terms of silver)
potassium cyanide: 50 g/L
dinitrobenzoic acid: 0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 3.0 g/L, 5.0 g/L
pH: 12
solution temperature: 20° C.
A test sample, a device and a plating treatment condition or the like of the high-speed partial plating test were the same as those of Example 4.
Also in Example 12, a plating state in the case of changing the concentration of dinitrobenzoic acid in the plating solution was externally observed. It became clear that as the added amount of dinitrobenzoic acid is increased, a groove portion is free from any plating treatment.
In Example 12, results of inspecting average plating film thicknesses of the groove portion as in Example 4 are shown in Table 12. The film thicknesses were also inspected as in Example 4.
From the results of Table 12, as in Example 4, it became clear that when the concentration of dinitrobenzoic acid in the plating solution is increased, plating treatment proceeds selectively on a circular plating portion of a substrate, and the groove portion that does not require any plating treatment is free from any plating treatment.
In the embodiment, results of inspecting plating properties of a hard gold-based plating solution of only gold will be described. Polyethylene amine was used as an organic additive contributing to hardening.
In Example 13, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of only gold was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
polyethylene amine: 10 g/L
citric acid: 150 g/L
dinitrobenzoic acid: 1 g/L, 5 g/L
pH: 7
solution temperature: 65° C.
A Hull cell test condition and evaluation were the same as those of Example 1. Results of measuring film thicknesses of points according to Example 13 are shown in Table 13.
Results of a hard gold-based plating solution to which dinitrobenzoic acid is not added are also shown for comparison in Table 13. As is apparent from the results shown in Table 13, it became clear that when nitrobenzoic acid is added as in the case of the first embodiment, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when dinitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which dinitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 14, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 14 is the same as that of Example 13. The composition of Example 14 is different from that of Example 13 only in a point that nitrobenzoic acid is used in place of dinitrobenzoic acid of Example 13. A Hull cell test condition and evaluation thereof were the same as those of Example 1. Results of measuring film thicknesses of points in Example 13 are shown in Table 14.
As is apparent from the results shown in Table 14, it became clear that when nitrobenzoic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzoic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzoic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 15, nitrobenzene sulfonic acid was used as an aromatic compound having one or more nitro groups. A composition of a hard gold-based plating solution of Example 15 is the same as that of Example 13. The composition of Example 15 is different from that of Example 13 only in a point that nitrobenzene sulfonic acid is used in place of dinitrobenzoic acid of Example 9. A Hull cell test condition and evaluation thereof were also the same as those of Example 1. Results of measuring film thicknesses of points in Example 15 are shown in Table 15.
As is apparent from the results shown in Table 15, it became clear that when nitrobenzene sulfonic acid is added, the plating film thickness of a low current density side is rapidly decreased. It also became clear that when the added amount thereof is set to 5 g/L, plating of the low current density side is further suppressed. It further became clear that when nitrobenzene sulfonic acid is added unlike the case of the hard gold-based plating solution to which nitrobenzene sulfonic acid is not added, a rear face side of a Hull cell plate is virtually free from any plating treatment.
In Example 16, as in Example 4, results of performing a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups to inspect electrodeposition properties thereof will be described. A composition of a hard gold-based plating solution was as follows.
gold(I) potassium cyanide: 12 g/L (8 g/L in terms of gold)
polyethylene amine: 10 g/L
citric acid: 150 g/L
dinitrobenzoic acid: 0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 3.0 g/L, 5.0 g/L
pH: 7
solution temperature: 65° C.
A test sample, a device and a plating treatment condition or the like of the high-speed partial plating test were the same as those of Example 4.
Also in Example 16, a plating state in the case of changing the concentration of dinitrobenzoic acid in the plating solution was externally observed. It became clear that as the added amount of dinitrobenzoic acid is increased, a groove portion is free from any plating treatment.
In Example 16, results of inspecting average plating film thicknesses of the groove portion as in Example 4 are shown in Table 16. The film thicknesses were also inspected as in Example 4.
From the results of Table 16, as in Example 4, it became clear that when the concentration of dinitrobenzoic acid in the plating solution is increased, plating treatment proceeds selectively on a circular plating portion of a substrate, and the groove portion that does not require any plating treatment is free from any plating treatment.
The present invention can apply the hard gold-based plating treatment to only the necessary portion of the electronic components such as the connector. Particularly, when the hard gold-based plating is applied on the surface of the nickel plating applied on the under layer, the partial plating treatment can be selectively applied.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-215592 | Aug 2008 | JP | national |
| 2009-147253 | Jun 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/063931 | 8/6/2009 | WO | 00 | 1/20/2011 |
