JP4227826B2 - Direct gold plating method and plating apparatus therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gold plating method, and more particularly to a method and apparatus for directly performing gold plating on a metal current-carrying layer that is more base than gold of an electronic element.
[0002]
[Prior art]
Conventionally, in a method of forming bumps and wiring on a wafer by plating, when the base material or the plating film is nickel, gold plating is often performed on the base material or the plating film. Non-cyan electrogold plating is widely used from the standpoint of properties.
[0003]
In this way, when non-cyan electrogold plating is performed on a metal conductive layer that is more basic than gold, such as nickel, gold plating should be performed under normal conditions after performing short-time plating called gold strike plating. Is common. This gold strike plating is a gold plating with a relatively high current density, and is performed to apply a thin gold plating on a base metal such as nickel in a short time, improving the adhesion between the underlying nickel and the gold plating. It is intended.
[0004]
However, in wafer processing, etc., downsizing of the apparatus is strongly demanded. For this purpose, simplification of the process is required, and the possibility of omitting gold strike plating is one of the examination items. Yes.
[0005]
On the other hand, although a gold plating layer may be formed by gold strike plating, the gold concentration of the gold strike plating solution is 1/3 to 1/10 that of a normal gold plating solution, which is not realistic.
[0006]
[Problems to be solved by the invention]
Therefore, it is an object of the present invention to develop a technique capable of omitting gold strike plating without reducing the adhesion between a metal layer such as a base nickel and a gold plating layer.
[0007]
[Means for Solving the Problems]
As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention are excellent between a base nickel or the like and gold plating by appropriately adjusting the energization state even in a non-cyan electrogold plating bath. The present invention has been completed by finding that it is possible to obtain high adhesion and eliminate gold strike plating.
[0008]
That is, according to the present invention, when non-cyan electrogold plating is performed on a metal current-carrying layer that is more basic than gold of an electronic element, after entering a non-cyanic gold plating bath, no current is applied and the current density is relatively high. The direct gold plating method is characterized in that power is supplied in the order of current supply and current supply at a relatively low current density and plating is performed.
[0009]
The present invention also includes a pretreatment tank, one or more water washing tanks, a nickel plating tank, one or more water washing tanks, a gold plating tank, and one or more water washing tanks in this order, and an anode in the gold plating tank. Direct gold plating characterized in that the power supply for energizing the power supply is provided with adjusting means for supplying power in the order of non-energization, energization at a relatively high current density, and energization at a relatively low current density Device.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the direct gold plating method and apparatus mean a gold plating method and apparatus in which the gold strike plating process prior to the gold plating process is omitted.
[0011]
The method of the present invention is characterized by a power feeding pattern in the gold plating step. That is, in the method of the present invention, after entering the non-cyan gold plating bath, it is necessary to supply power in the order of non-energization, energization at a relatively high current density, and energization at a relatively low current density. .
[0012]
In this power feeding pattern, the first non-energization may be performed for about 5 to 30 seconds after entering the tank. This time is a time for replacing the water adhering to the electronic device, particularly to the fine groove, with the gold plating solution by washing with water in the previous step.
[0013]
The energization at the next relatively high current density is an energization performed at a slightly higher current density than the standard current density in non-cyan gold plating, for example, about 0.7 to 1 A / dm ² , What is necessary is just to perform for about 1 to 30 seconds.
[0014]
The last energization at a relatively low current density is an energization performed at a standard current density in non-cyan gold plating, and may be performed at a current density of 0.3 to 0.5 A / dm ² , for example. . In addition, what is necessary is just to let this energization time be the time according to the target plating thickness.
[0015]
The non-cyanide gold plating bath used in the method of the present invention is not particularly limited, and plating baths disclosed in various literatures and patents can be used. Preferred examples include the following. The thing of a structure can be mentioned.
[0016]
That is, non-cyanide gold plating baths containing metal regulators and stabilizers such as gold sulfites such as sodium gold sulfite and potassium gold sulfite, thallium sulfate, diarsenic trioxide, and bismuth sulfate as metal salts are preferred. be able to. Among these, examples of the stabilizer include known benzene organic compounds, naphthalene organic compounds, pyridine organic compounds, and the like.
[0017]
Further, preferable plating conditions for the non-cyan gold plating bath include a bath temperature of pH 7 to 9 and 40 to 60 ° C. In particular, in the case of pH 7, the temperature is about 40 to 45 ° C. and pH 7.5. In the case of about 40-55 degreeC, in the case of pH8, about 40-60 degreeC, and in the case of pH8.5, the range of about 40-45 degreeC is preferable.
[0018]
As an apparatus for performing the above-described direct gold plating method of the present invention advantageously, for example, a plating apparatus having the configuration shown in FIG. 1 can be used. In this figure, 1 is a plating apparatus, 2 is a nickel plating tank, 3 is a gold plating tank, 4 is a pretreatment tank, 5 is a washing tank, 6 is an anode, 7 is a power source, and 8 is an adjusting means.
[0019]
As shown in FIG. 1, the plating apparatus 1 includes a pretreatment tank 4, a washing tank 5 a, a nickel plating tank 2, a washing tank 5 b, a gold plating tank 3, and a washing tank 5 c, and an anode 6 a in the nickel plating tank 2. The anode 6b in the gold plating tank 3 is supplied with power from power sources 7a and 7b, respectively. Among these, the power supply 7b for the gold plating tank 3 is provided with an adjusting means 8.
[0020]
Further, the washing tanks 6a, 6b and 6c may be one-stage or multi-stage, but it is generally preferable that each of them is a multi-stage washing tank. Further, the adjusting means 8 supplies power in the order of non-energization, energization at a relatively high current density, and energization at a relatively low current density in accordance with a program incorporated in advance. Implement the method. Note that the function of the adjusting means 8 may be incorporated in the power source 7b.
[0021]
【Example】
EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not restrict | limited to this Example at all.
[0022]
Example 1
Direct gold plating test:
Using a non-cyanide gold plating solution having the following composition, gold plating was performed at various temperatures and pHs using the power supply pattern shown in FIG. 2 (target plating film thickness: 0.35 μm). As a sample for plating, a copper plating of 10 μm and then a nickel plating of 10 μm were used as the base plating.
[0023]
(Non-cyan gold plating solution composition)
Sodium gold sulfite 21.6 g / L
Sodium sulfite 25 g / L
Thallium sulfate 6.2mg / L
pH adjuster (sulfuric acid or sodium hydroxide)
About the obtained gold-plated sample, a tape was affixed, and then it was examined whether or not the plating film was peeled off by peeling off the tape. The evaluation was evaluated as “Good” for those having no peeling at all, “Good” for those having peeling at several places, “B” for poor adhesion, and “No” for those having reached the whole surface peeling. The result is shown in FIG.
[0025]
From this result, it is 40-45 degreeC in the case of pH7, 40-55 degreeC in the case of pH7.5, 40-60 degreeC in the case of pH8, 40-45 degreeC in the case of pH8.5. In each case, no peeling was observed, indicating good adhesion.
[0026]
【The invention's effect】
According to the present invention, gold plating with good adhesion can be performed without going through a gold strike step.
[0027]
Therefore, by adopting the present invention, the gold strike step can be omitted, and the gold strike plating tank can be eliminated from the plating apparatus, so that the size of the entire apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an example of a direct gold plating apparatus according to the present invention. FIG. 2 is a diagram showing an energization pattern in Example 1. FIG. 3 is a graph showing the relationship between pH, temperature and peelability in Example 1. Drawing to show 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 ...... Plating apparatus 2 ...... Nickel plating tank 3 ...... Gold plating tank 4 ...... Pretreatment tank 5 ...... Washing tank 6 ...... Anode 7 ...... Power supply 8 ...... Adjustment means

Claims (6)

When performing non-cyan electroplating on the nickel energization layer, after entering the non-cyanide gold plating bath, no energization, energization at a relatively high current density, and energization at a relatively low current density. A direct gold plating method characterized by plating in which power is supplied in sequence and the non-energization time is 5 to 30 seconds after entering the bath and the energization time at a relatively high current density is 1 to 30 seconds . Relatively high current density, direct gold plating method as in claim 1 wherein a 0.7~1A / dm ^2. Relatively low current density, direct gold plating method as in claim 1 wherein a 0.3~0.5A / dm ^2.   2. The direct gold plating method according to claim 1, wherein the non-cyanic gold plating bath contains a stabilizer selected from gold sulfite, a crystal modifier, and a benzene organic compound, a naphthalene organic compound and a pyridine organic compound. .   The direct gold plating method according to claim 1, wherein the plating conditions of the non-cyanic gold plating bath are pH 7 to 9 and the bath temperature is 40 to 60 ° C. A pretreatment tank, one or more water washing tanks, a nickel plating tank, one or more water washing tanks, a gold plating tank and one or more water washing tanks are arranged in this order, and the anode in the gold plating tank is energized. Power is supplied to the power supply in the order of non-energization, energization at a relatively high current density, and energization at a relatively low current density , and the non-energization time is relatively high for 5 to 30 seconds after entering the tank. A direct gold plating apparatus, characterized in that an adjusting means is provided for setting the energization time at a density to 1 to 30 seconds .

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