JPS6379991A - Nickel electroplating bath and plating method using the same - Google Patents

Abstract

PURPOSE:To obtain a nickel electroplating bath enabling nickel plating with superior throwing power by preparing a plating bath contg. nickel chloride, an alkali salt of sulfuric acid and boric acid. CONSTITUTION:A nickel electroplating bath contg. a nickel halide such as nickel chloride or nickel bromide as a nickel source which doubles as an anode dissolution accelerator or nickel sulfate or nickel sulfamate as a nickel source and a halide such as sodium chloride or potassium bromide as an anode dissolution accelerator, an alkali salt of sulfuric acid, sulfamic acid or methanesulfonic acid as an electrically conductive salt and boric acid as a buffer is prepd. The amount of metallic nickel in the bath is 0.01-1mol/l, the molar ratio of the metallic nickel to the electrically conductive salt is 1:>=2 and the amount of the boric acid is 0.1mol/l the saturation concn. When plating is carried out by a PR process with the plating bath, a plated nickel film of a uniform thickness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrolytic nickel plating bath and a plating method using the same.

(Background Art) In recent years, the shapes of electronic components and the like have become increasingly smaller and more complex. In addition, further improvements in functional properties are required, and in the plating field, variations in the plating thickness of nickel plating, which is the base for various functional platings such as gold plating, are
I L standard (nickel thickness for gold plating base is 1.2
Strict conditions are required, such as keeping the variation in plating thickness within ±50%.

1 Currently, the mainstream nickel plating bath is Watt bath or □
is a sulfamic acid bath.

Cヮ2.1, bath. Bath, composition, example 4. Nickel sulfate 300g/β Nickel chloride 40g/ρ Boric acid 40g/β, and the bath composition of the sulfamic acid bath is, for example, nickel sulfamate 300g/ff nickel chloride 40g/7! Boric acid: 40g/ρ.

However, the above-mentioned Watt bath or sulfamic acid bath has poor plating coverage and uniform electrodeposition, and as mentioned above, as the shape of the plated object becomes smaller and more complex, the variation in film thickness becomes large. There is a difference of more than 10 times between the area and the thin area.

For example, when barrel plating is applied to an airtight glass terminal for a semiconductor device, the thickness of the nickel plating on the tip of the lead post is 10 μm or more, and on the surface of the eyelet (metal outer ring) it is about 2 μm. Variations occur, and because the aforementioned Nokel plating is thick, there are problems such as blistering and peeling of wire bonding due to heating.

In addition, in the case of leadless chip carriers (1-CC), small-diameter through-poles are formed on the object to be plated during the plating process, and it is difficult to uniformly electrodeposit nickel plating on the inner walls of these through-poles. However, there are problems such as the required soldering does not ensure proper soldering.

Furthermore, when applying nickel plating as the base plating to a DIP type or PGA type semiconductor device package, the plating on the inner lead part is thicker than on the stage part in the recess, and when gold plating is applied. However, there are also problems such as blistering caused by heating and peeling of wire bonding.

The present invention has been made in view of the various circumstances mentioned above,
The purpose is to provide an electrolytic nickel plating bath with excellent uniform electrodeposition and an electrolytic nickel plating method that can perform nickel plating more uniformly.

(Summary of the Invention) The electrolytic nickel plating bath of the present invention for the above purpose uses a nickel halide such as nickel chloride or nickel bromide as a nickel source and an anodic dissolution promoter, or anodic dissolution with nickel sulfate or nickel sulfamate as a nickel source. It is characterized by containing a halide such as sodium chloride or potassium bromide as a promoter, an alkali salt of sulfuric acid, sulfamic acid or methanesulfonic acid as an electrical conductivity salt, and a buffer.

In addition, nickel halides such as nickel chloride and nickel bromide as a nickel source and anode dissolution promoter, or nickel sulfate or nickel sulfamate as a nickel source and halides such as sodium chloride and potassium bromide as anode dissolution promoters, Sulfuric acid as electrical conductivity salt,
PR using an electrolytic nickel plating bath containing an alkali salt of sulfamic acid or methanesulfonic acid and a buffering agent.
It is characterized by being plated using a method.

In the present invention, it is preferable to use nickel halides such as nickel chloride and nickel bromide as the nickel source and anode dissolution promoter. It may be used in combination with a halide. Nickel salt concentration is 0.01M/A as metallic nickel.
-IM/ff, but 0.1M/1~0.4M
7! degree is suitable. This is considerably lower than the aforementioned Watt bath and sulfamic acid bath, which are around 1.7 M/ff as metallic nickel. Suitable electrical conductivity salts include alkali salts of sulfuric acid such as sodium sulfate, alkali salts of sulfamic acid such as sodium sulfamate and potassium sulfamate, and alkali salts of methanesulfonic acid such as potassium methanesulfonate.

The higher the molar ratio of the electrical conductivity salt to the metal nickel, the better the uniform electrodeposition, but as this molar ratio increases, the current density cannot be high and the high speed is inferior.
The electrical conductivity salt concentration is preferably 1 to 2 or more at this molar ratio and not too high. It was also observed that the higher Pl+, the better the uniform electrodeposition, but if it is too high, the plating tends to blister due to heating, so the pH is preferably about 4 to 5.

Boric acid is used as a buffer, and its content is 0°1M/
β~Saturation is valid.

With the above bath composition, excellent uniform electrodeposition was obtained as described above using a normal DC power supply.

When plating was performed using the PR method, a nickel plating film with a uniform thickness was obtained.

Specific examples are shown below.

(Example) Example 1 Nickel chloride 0.25M/1 Sodium sulfate 0.5M/7! Boric acid
0.75M/7! Using the above bath, PI(4,0,
When a Hull cell test was conducted at a bath temperature of 55° C. Cl2A for 7 minutes and 30 seconds, the high current density side faded and turned black, but the rest became white and matte. In addition, the film thickness at the four points in Figure 1 was measured using a fluorescent X-ray film thickness measuring device (SFT 157 manufactured by Seiko Electronic Industries).
Table 1 shows the results when measured using the following.

In addition, the current density at each corresponding point was determined using Terakado and Nagaita's equations.

Table 1 The above values were entered into Field's equation to determine the uniform electrodeposition property, which was found to be 54%. Similarly, when the uniform electrodeposition was determined using a Watt bath, the uniform electrodeposition was 13%.
It was found that the above bath had excellent uniform electrodeposition properties.

When the uniform electrodeposition was measured in the same manner using different nickel sources and electrical conductivity salts, the results shown in Table 2 were obtained, and it was found that each sample had excellent uniform electrodeposition.

Table 2 Nickel concentration 0.25M/1 Electrical conductivity salt concentration
0.5M/1 Example 2 Nickel chloride 0.25M/ρ Sodium sulfate 0.5M/7! Boric acid
0.75? I/ρ Using the above bath, PH4, 0, 55℃
, 2 A/d n (Nickel plating was applied to a ceramic package for a semiconductor device as shown in Fig. 2 by the rank method with an aim of 4 μm. Stage part 10, inner lead part 1
2. The nickel plating thickness of the seal ring part 14 is 3.5
μm, 4.7 μm, and 4.4 μm. When the same ceramic package was nickel plated using the rank method using a Watt bath, the stage, inner lead, and seal ring parts were 3.0 μm thick and 9.1 μm thick.
, 7.4 μm. It can be seen that when the above bath is used, nickel can be plated uniformly.

Even when nickel bromide is used as the Ni salt and sodium sulfupate is used as the electrical conductivity salt, the nickel plating thickness on the stage section, inner lead section, and seal ring section is 3.4 μm, 4.8 μm, and 4.4 μm. The variation was about the same as in the above bath. Further, gold plating was applied on the obtained nickel plating, and the die attachment properties, wire bonding properties, and heat resistance were examined, but no problems were found.

Example 3 Using the bath of Example 2, the pH was 4.0, the bath temperature was 55°C, the current density during piezoelectric reverse current was 3 A/d%, and the PR ratio was 10/2 seconds as shown in Figure 2. Nickel plating was applied to a ceramic package with a thickness of 4 μm using the rank method.

The plating thickness of the stage part 10, inner lead part 12, and seal ring part 14 is 3.8 μm and 4.4 μm, respectively.
, 4.1 μm, and was found to be uniformly non-electrostatic.

In addition, the obtained nickel plating was gold plated, and its die attachment properties, wire bonding properties, heat resistance, etc. were examined, but no problems were found. Furthermore, when nickel plating was applied to the LCC using the rack method under the conditions described in item 1, it was found that the plating thickness on the inside and outside of the through hole was approximately uniform at 3.9 μm and 4.2 μm. When gold plating was applied to this nickel plating and the soldering properties were examined, it showed considerably better solder leakage than Watt bath.

(Effects of the Invention) As described above, according to the plating bath according to the present invention, nickel plating with excellent uniform electrodeposition can be performed by electrolytic plating.

Furthermore, the plating method of the present invention has the remarkable effect of being able to perform nickel plating with better uniformity of electrodeposition.

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. It is.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing measurement points of plating film thickness on a Hull cell test piece, and FIG. 2 is an explanatory plan view of a ceramic package for a semiconductor device. 10... Stage part, 12... Inner lead part, 14... Seal ring part.

Claims (1)

[Claims] 1. Nickel halide such as nickel chloride or nickel bromide as a nickel source and anode dissolution promoter, or nickel sulfate or nickel sulfamate as a nickel source and sodium chloride or potassium bromide as an anode dissolution promoter halides such as, and an alkali salt of sulfuric acid, sulfamic acid or methanesulfonic acid as an electrically conductive salt,
An electrolytic nickel plating bath containing a buffering agent. 2. The content of metallic nickel in the bath is 0.01M/l to 1
The electrolytic nickel plating bath according to claim 1, wherein M/l. 3. The molar ratio of metallic nickel and electrical conductivity salt in the bath is 1.
The electrolytic nickel plating bath according to claim 1 or 2, wherein: 2 or more. 4. Using boric acid as a buffer, its content is 0.1M
The electrolytic nickel plating bath according to claim 1, 2 or 3, wherein the electrolytic nickel plating bath is from /l to saturation. 5. Nickel halide such as nickel chloride or nickel bromide as a nickel source and anode dissolution promoter, or nickel sulfate or nickel sulfamate as a nickel source and a halide such as sodium chloride or potassium bromide as an anode dissolution promoter; an alkali salt of sulfuric acid, sulfamic acid or methanesulfonic acid as an electrically conductive salt;
An electrolytic nickel plating method characterized by plating by the PR method using an electrolytic nickel plating bath containing a buffering agent.