TW202233899A - Plating structure comprising Ni electrolytic plating film, and lead frame including said plating structure - Google Patents

Abstract

Provided is a plating structure including a substrate configured from Cu or a Cu alloy, an Ni electrolytic plating film formed on the substrate, a Pd plating film formed on the Ni electrolytic plating film, and an Au plating film formed on the Pd plating film, wherein: the Ni electrolytic plating film contains 0.01-1.0 wt% (inclusive) of P; when the P content is 0.01 wt% or more and less than 0.05 wt%, the film thickness of the Ni electrolytic plating film is 0.1-10 [mu]m (inclusive); when the P content is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the Ni electrolytic plating film is 0.06-10 [mu]m (inclusive); and when the P content is 0.2-1.0 wt% (inclusive), the film thickness of the Ni electrolytic plating film is 0.01-10 [mu]m (inclusive). The present invention addresses the problem of providing a plating structure comprising an Ni plating film that has exceptional solder wetting properties.

Description

Plating structure with Ni plating film and lead frame including the plating structure

The present invention relates to a Ni plated film and a plated structure provided with the plated film, and more particularly to a plated structure in a bonding portion such as wire bonding in semiconductor packages such as ICs and LSIs.

As a method of mounting a semiconductor element on a substrate in semiconductor packages such as ICs and LSIs, there are known a method called flip chip for electrical connection by protruding terminals called bumps, and a method called flip chip using a lead frame. A method of electrically connecting (wire bonding) with external wiring. Regarding flip chip packaging, for example, Patent Documents 1 to 4 disclose that an electroless plating film of Ni/Pd/Au is formed on a connection terminal portion of a semiconductor element, and a solder bump is formed thereon.

On the other hand, regarding wire bonding, the present applicant previously provided an invention (Patent Document 5), which relates to a plated structure composed of three layers of Ge—Ni/Pd/Au formed by electroplating. In addition, a technique of forming a Ni/Pd-P/Au film by electroplating is also known (Patent Document 6). Although the above-mentioned plating film can be formed by electroplating or electroless plating, since electroplating and electroless plating each have advantages and disadvantages, they are generally used according to the objects to be plated. [Prior Art Literature] [Patent Literature]

[Patent Document 1]: Japanese Patent Application Laid-Open No. 11-345896 [Patent Document 2]: Japanese Patent Laid-Open No. 2006-179797 [Patent Document 3]: International Publication No. 2006/112215 [Patent Document 4]: Japanese Patent Application Laid-Open No. 2016-162770 [Patent Document 5]: Japanese Patent Application Laid-Open No. 2009-228021 [Patent Document 6]: Japanese Patent Laid-Open No. 2012-241260

[The problem to be solved by the invention]

As one of the surface treatment methods of the lead frame, there is a method called Pd-PPF (Pre Plated Frame) (refer to Patent Document 6). In this method, Ni/Pd/Au three-layer plating is performed on the entire surface of the Cu-based lead frame, whereby the solder wettability can be improved, and sufficient bonding performance can be obtained. As an attempt to reduce the cost of the Pd-PPF lead frame, thinning of precious metal films such as Au and Pd has been promoted.

The thinning of the precious metal plating film must not impair the solder wettability. The determination of whether this effect can be maintained is performed by the evaluation of solder wettability after heat-processing a plated film. For example, as described in Patent Document 5, a test piece having a plated film formed thereon is subjected to heat treatment and then immersed in a solder bath, and the time until the wetting stress value becomes zero (zero cross time) is measured. ): ZCT), if this time is short enough, it can be considered that the solder wettability is maintained.

In the current technology, even if the Au and Pd plating films are several nanometers to several tens of nanometers, sufficient solder wettability can be maintained, and the cost reduction by the thinning of the precious metal plating films has reached the limit. On the other hand, there is still room for improvement in the Ni plated film. By improving the characteristics (solder wettability) of the Ni plated film, thinning can be achieved, and it is expected that the tact time can be further reduced by shortening the tact time. cost. The present invention was made in view of such a problem, and an object of the present invention is to solve the problem of providing a Ni-plated film excellent in solder wettability and a plated structure provided with the Ni-plated film. [Technical means to solve the problem]

In order to solve the above-mentioned problems, the present inventors have made diligent studies, and as a result, they have obtained the following knowledge: by including a specific amount of P (phosphorus) in the Ni (nickel) electroplating film, it is possible to form a Ni (nickel) electroplating film excellent in solder wettability. As for completing the present invention. The above-mentioned problems are solved by the means shown below.

1) A plated structure comprising: a substrate made of Cu or a Cu alloy; a Ni plating film formed on the substrate; a Pd plating film formed on the Ni plating film; and an Au plating film Coating film, which is formed on the Pd plating film; the Ni plating film contains 0.01 wt% or more and 1.0 wt% or less of P, and when the P content is more than 0.01 wt% and less than 0.05 wt%, the Ni plating film The film thickness of the Ni plating film is 0.1 μm or more and 10 μm or less, and when the P content is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above Ni plating film is 0.06 μm or more and 10 μm or less, and the P content is 0.2 wt% % or more and 1.0 wt% or less, the film thickness of the above-mentioned Ni plating film is 0.01 μm or more and 10 μm or less. 2) A plated structure comprising: a substrate made of Cu or a Cu alloy; a Ni plating film formed on the substrate; and a Pd plating film formed on the Ni plating film; the above-mentioned Ni plating film The electroplating film contains 0.01 wt% or more and 1.0 wt% or less of P. When the P content is more than 0.01 wt% and less than 0.05 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.1 μm or more and 10 μm or less. When the content of P is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.06 μm or more and 10 μm or less, and when the content of P is 0.2 wt% or more and 1.0 wt% or less, the above Ni electroplating film has a thickness of 0.06 μm or more and 10 μm or less. The film thickness of the film is 0.01 μm or more and 10 μm or less. 3) A plated structure comprising: a substrate made of Cu or a Cu alloy; a Ni plated film formed on the substrate; and an Au plated film formed on the Ni plated film; wherein, The above-mentioned Ni electroplating film contains 0.01 wt% or more and 1.0 wt% or less of P, and when the P content is 0.01 wt% or more and less than 0.05 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.1 μm or more and 10 μm or less, When the P content is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.06 μm or more and 10 μm or less, and when the P content is 0.2 wt% or more and 1.0 wt% or less, the above The thickness of the Ni plating film is 0.01 μm or more and 10 μm or less. 4) The plated structure according to any one of the above 1) to 3), wherein a metal impact composed of any one of Au, Ag, Pd, and Cu is formed as an underlayer of the Ni plated film plated film. 5) The plated structure according to any one of 1) to 4) above, wherein as the bottom layer of the Pd plated film and/or the Au plated film, any one of Au, Ag, and Pd is formed. The formed metal impact plating film. 6) A lead frame comprising the plated structure according to any one of 1) to 5) above. [Effect of invention]

ADVANTAGE OF THE INVENTION According to this invention, there exists an excellent effect that the Ni electroplating film which is excellent in solder wettability can be obtained. In addition, it has the excellent effect of being able to maintain good solder wettability and to achieve the thinning of the Ni plating film. In the film forming step of the plated film, the Ni plated film is particularly time-consuming. Therefore, by reducing the Ni plated film to a thin film, the takt time can be greatly shortened.

Electroless plating does not use electricity, so it can be uniformly plated without being affected by current. On the other hand, since it forms a film by chemical reaction, the rate of film formation is slow, and a plating bath must be used. Chemically stable, there are cases where the cost of maintenance and management of chemical solutions and plating tanks is relatively high. In view of such a situation, when forming a plating film on the entire surface of the lead frame, the plating film is usually formed by electroplating.

The inventors of the present invention have made intensive studies to improve the solder wettability of the plating film, and found that the solder wettability of the plating film can be improved by including a specific amount of P (phosphorus) in the Ni plating film. In particular, it was found that sufficient solder wettability can be maintained even when the Ni plating film is thinned. Thereby, the tact time can be shortened by thinning the Ni plating film, and the cost can be expected to be reduced.

The Ni plating film of the embodiment of the present invention is characterized by containing P (phosphorus) in an amount of not less than 0.01 wt % and not more than 1.0 wt %. By making the phosphorus content in the Ni plating film into the above-mentioned range, the solder wettability of the Ni plating film can be improved. On the other hand, when the content of P is less than 0.01 wt %, the effect of improving the solder wettability cannot be obtained, and when the content of P exceeds 1.0 wt %, the solder wettability decreases on the contrary. The lower limit of the content of P is preferably 0.08 wt% or more, more preferably 0.18 wt% or more, and the upper limit of the content of P is preferably 0.8 wt% or less, more preferably 0.61 wt% or less.

The Ni plating film containing P (phosphorus) was observed with a scanning electron microscope, and the following tendency was observed: as the phosphorus content increased, the particles of the Ni plating film became finer. In addition, when the Ni plated film was heated, the crystals expanded compared with those before heating, but the higher the P content, the more suppressed the crystals from expanding. This crystal refinement is considered to be because phosphorus is concentrated at the grain boundaries and inhibits crystal growth. The reason for the decrease in solder wettability is considered to be that the underlying metal (Cu or Cu alloy, etc.) diffuses to the outermost surface of the plated film and is exposed to the atmosphere and oxidizes. Diffusion of the underlying metal, thereby inhibiting the decrease in solder wettability.

The film thickness of the Ni electroplating film can be determined by the relationship with the P content. When the P content is 0.01 wt% or more and less than 0.05 wt%, the film thickness of the Ni electroplating film is 0.1 μm or more and 10 μm or less. When the content of P is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.06 μm or more and 10 μm or less, and the P content is 0.2 wt% or more and 1.0 wt% or less (or 0.8 wt% 0.61 wt% or less), the film thickness of the above-mentioned Ni electroplating film shall be 0.01 μm or more and 10 μm or less. The Ni plating film of the present embodiment is particularly excellent in that good solder wettability can be secured even when the film thickness of the Ni plating film is reduced to 1 μm or less.

When the content of P is more than 0.01 wt% and less than 0.05 wt%, if the film thickness of the Ni plating film is less than 0.1 μm, the effect of preventing the diffusion of the underlying metal (Cu or Cu alloy) will be weakened, and Cu will form on the surface. oxides, resulting in reduced solder wettability. In addition, when the content of P is 0.05 wt% or more and less than 0.2 wt%, if the film thickness of the Ni plating film is less than 0.06 μm, the effect of preventing the diffusion of the underlying metal (Cu or Cu alloy) will be weakened, and the surface Oxides of Cu are formed, resulting in reduced solder wettability. Furthermore, when the content of P is 0.2 wt% or more and 1.0 wt% or less, if the film thickness of the Ni plating film is less than 0.01 μm, the function of preventing the diffusion of the underlying metal (Cu or Cu alloy) is weakened as described above. resulting in reduced solder wettability. The film thickness is preferably 0.06 μm or more, more preferably 0.1 μm or more, and still more preferably 0.2 μm or more. Furthermore, although the film thickness of the Ni electroplating film is thicker, the solder wettability is improved, but if the film thickness exceeds the required thickness, excess Ni will adhere, resulting in an increase in cost. Therefore, the film thickness is set to 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less, and most preferably 0.5 μm or less.

The plated structure of the embodiment of the present invention can have the following structure. Structure (I): (substrate)/Ni plating film/Pd plating film/Au plating film (outer surface) Structure (II): (substrate)/Ni plating film/Pd plating film (top surface) Structure (III): (substrate)/Ni plating film/Au plating film (top surface) Here, the above-mentioned Ni plating film is the Ni plating film containing P of the present embodiment. Any of the above-mentioned plating films may be formed of a plating film. The Pd plating film may be not only pure Pd but also Pd alloy. This embodiment is particularly effective when Cu or Cu alloy is used as the substrate (underlying metal), but does not prevent the use of other materials such as Fe or Fe alloy. The above-mentioned plated structure can be selected according to the application and required properties. The main purpose of the Au plating film or the Pd plating film formed on the outermost surface is to prevent the oxidation of the Ni plating film and to prevent the diffusion of Ni to the surface.

In the Ni plating film, the Pd plating film, and the Au plating film, a metal impact plating film can be formed as a base layer, respectively. Generally, in order to improve the adhesiveness of the electroplating film, impact plating may be performed as a pretreatment. In the case of forming the Ni plating film, it is preferable to perform metal impact plating composed of any one of Au, Ag, Pd, and Cu. In the case of forming the Pd plating film and/or the Au plating film, it is preferable to perform metal impact plating composed of any one of Au, Ag, and Pd. The film thickness of the metal impact plating film is not particularly limited, but can be set to, for example, 0.001 to 0.5 μm. Preferably it is 0.01-0.1 micrometer.

Another embodiment of this invention is the lead frame provided with the said plating structure. The lead frame is mostly composed of copper or copper alloy. By forming the plated structure of the present embodiment on such a lead frame, it is possible to realize excellent bonding at the time of wire bonding or soldering. Furthermore, the plated structure of the present embodiment can be formed not only on the lead frame but also on the pad portion used in the flip chip package, and it is presumed that an excellent bonding can be obtained similarly.

However, depending on the object to be plated, the Ni/Pd/Au plated film may be formed by electroless plating. In the case of electroless plating, a phosphorus compound is sometimes used as a reducing agent in the plating solution, and in this case, P (phosphorus) is necessarily contained in the Ni film. It is also possible to form a Ni film with a P content of 0 wt% by using a reducing agent other than phosphorus compounds, but it is difficult to control the P content in the Ni film to be less than 2 wt% because it is derived from the reducing agent.

The Ni plating film of this embodiment can be formed by electroplating using a nickel plating bath containing a phosphorus compound. As the phosphorus compound, hypophosphorous acid, phosphorous acid, phosphoric acid, or the like can be used. In addition, other phosphorus-containing compounds may be used instead. As the nickel plating bath, a Watts bath, a sulfamine bath, a citric acid bath, or the like can be used. In addition, other nickel-containing plating baths may be used instead. The phosphorus compound and nickel plating bath shown above are illustrative and non-limiting. In metal conversion, the amount of nickel salt in the Ni plating bath can be set to 40 to 125 g/L. In addition, in terms of phosphorus, the amount of the phosphorus compound can be set to 5 to 300 mg/L. It should be understood that the amounts of nickel salts and phosphorus compounds shown above are exemplary and not intended to limit the scope of the disclosure.

Ni plating conditions can be set as follows. However, it is obvious that the electroplating conditions are exemplary, and that there are many processing systems and processing apparatuses for performing Ni electroplating, and according to the processing systems and processing apparatuses, the electroplating conditions can be changed. Therefore, it should be noted that there is no intention to be limited to the disclosed plating conditions. Cathode current density: 1～10 A/dm ² Electrolysis time: 5～30 min pH value: 3～6 Bath temperature: 30～60℃ Cathode: copper or copper alloy Anode: nickel

The Pd plating film and the Au plating film can be formed using a known plating bath and known plating conditions (for example, Patent Document 5). In addition, the metal impact plated film can also be formed using a known plating bath and known plating conditions. [Example]

Next, the Example and the comparative example of this invention are demonstrated. Furthermore, the following examples are only representative examples, and the present invention should be construed within the scope of the technical idea described in the specification without being limited to these examples.

<About preparation of evaluation samples> As a pretreatment, electrolytic degreasing (liquid temperature: 68° C., current density: 10 A/dm ² , immersion time: 60 seconds) was performed on a lead frame made of a Cu alloy, followed by acid Washing (5 vol.% sulfuric acid, 30 seconds), after that, washing with pure water. Under the following plating conditions, Ni plating, Pd plating, and Au plating were sequentially performed on the pretreated lead frame. At this time, the P concentration in the Ni plating solution was changed to adjust the evaluation sample.

(Ni plating conditions) Plating bath: Matte Watt bath containing phosphorus compound Ni concentration: 66 g/L P concentration: 0～200 mg/L Current density: 5 A/dm ² Bath temperature: 50℃ pH value: 4 Target film thickness: 0.13 μm

(Pd plating conditions) Plating bath: Palladium plating solution (manufactured by Matsuda Sangyo Co., Ltd.: Palla Sigma UF) Pd concentration: 3 g/L Current density: 0.5 A/dm ² Bath temperature: 40°C pH: 6.5 Target Film Thickness: 0.025 μm Anode: Iridium Oxide

(Au plating conditions) Plating bath: Gold plating solution (manufactured by Matsuda Sangyo Co., Ltd.: Auru Sigma F) Au concentration: 2 g/L Current density: 2 A/dm ² Bath temperature: 45°C pH: 4 Target Film Thickness: 0.005 μm Anode: Iridium Oxide

(Determination of Phosphorus Content) The measurement of the phosphorus content in the Ni plating film of each evaluation sample was performed using a high-frequency induction coupled plasma (ICP) emission spectrometer.

(Evaluation of Solder Wettability) Each evaluation sample was kept under specific temperature conditions (400°C ± 2°C) for a certain period of time to apply a high temperature thermal history, and then immersed in a solder bath (63%-Sn, 37%-Pb, liquid temperature : 230° C.±5° C.), and then the time required until the force applied to the solder bath became zero (zero crossing time) was measured, and the solder wettability was evaluated. A shorter zero crossing time means better solder wettability. Regarding the conditions of immersion in the solder bath, the immersion depth was set to 1 mm, the immersion speed was set to 2 mm/sec, the immersion time was set to 5 seconds, and R-type flux (inactive type) was used as a soldering accelerator .

<Evaluation of P content of Ni plated film> Table 1 shows the relationship between the P content contained in the Ni film and the zero-crossing time. As shown in Table 1, it was confirmed that the solder wettability was improved by adding phosphorus. In particular, when the phosphorus content is 0.1 wt % or more and 0.8 wt % or less, the solder wettability is greatly improved. In addition, in general, Pb-free solder has poorer solder wettability than Pb-Sn solder, but it was confirmed that even when Pb-free solder (Sn-3.0Ag-0.5Cu) was used, the solder wettability Sex is no problem.

[Table 1] P concentration in Ni plating solution P content in Ni plating film zero crossing time mg/L wt% sec Comparative Example 1 0 0 no welding Example 1 5.4 0.03 2.8 Example 2 10.9 0.06 2.4 Example 3 16.3 0.08 1.7 Example 4 21.8 0.14 1.3 Example 5 32.7 0.18 0.9 Example 6 54.5 0.26 0.8 Example 7 76.3 0.35 0.8 Example 8 98.1 0.42 0.8 Example 9 109 0.56 0.8 Example 10 119.9 0.61 0.9 Example 11 163.5 0.78 1.1 Example 12 196.2 0.93 2.1

<Evaluation of Thinning of Ni Plating Film> Except that the P concentration in the Ni plating solution was set to 5.4 mg/L, 10.9 mg/L, 32.7 mg/L, 76.3 mg/L, and 119.9 mg/L, the Ni plating film thickness was changed as shown in Table 2. Evaluation samples were prepared under the same plating conditions as above. And, under the same conditions as above, the solder wettability of each sample was evaluated. In addition, regarding the thickness of the plated film of 0.13 μm, it was obtained by directly referencing the results in Table 1. The results are shown in Table 2. As shown in Table 2, it was confirmed that good solder wettability can be maintained even if the film thickness of the Ni plating film is 1.0 μm or less. In addition, as the film thickness of the Ni plating film was increased, the solder wettability was improved. Therefore, the case where the film thickness exceeded 0.3 μm was not shown in the examples, but it was confirmed that there was no problem in the solder wettability.

[Table 2] P concentration in Ni plating solution P content in Ni plating film Thickness of Ni plating film zero crossing time mg/L wt% μm sec Comparative Example 2 5.4 0.03 0.01 no welding Comparative Example 3 0.034 no welding Comparative Example 4 0.05 no welding Example 13 0.1 5.5 Example 14 0.2 1.5 Example 15 0.3 1.0 Comparative Example 5 10.9 0.06 0.03 no welding Example 16 0.06 8.5 Example 2 0.13 2.4 Example 17 0.2 1.4 Example 18 0.3 0.9 Comparative Example 6 32.7 0.18 0.034 no welding Example 19 0.061 1.1 Example 5 0.13 0.9 Example 20 0.2 0.9 Example 21 0.3 0.8 Example 22 76.3 0.35 0.038 0.9 Example 23 0.58 0.9 Example 7 0.13 0.8 Example 24 0.2 0.8 Example 25 0.3 0.7 Example 26 119.9 0.61 0.037 1.0 Example 27 0.83 0.9 Example 10 0.13 0.9 Example 28 0.2 0.7 Example 29 0.3 0.8

<Formation of Metal Impact Plating> As a pretreatment, electrolytic degreasing (liquid temperature: 68° C., current density: 10 A/dm ² , immersion time: 60 seconds) was performed on a lead frame made of a Cu alloy, and then, After pickling (5 vol.% sulfuric acid, 30 seconds), it was washed with pure water. Cu impact plating, Ni plating, Pd plating, and Au plating were sequentially performed on the lead frame after the pretreatment. At this time, the P concentration in the Ni plating solution was changed to adjust the evaluation sample. In addition, Ni plating, Pd plating, and Au plating were performed under the same conditions as above, and the impact plating was set as follows.

(Cu impact plating conditions) Plating bath: Cu impact plating solution Cu concentration: 40 g/L Current density: 1 A/dm ² Bath temperature: 25°C pH value: 13 Target film thickness: 0.001 μm Anode: iridium oxide

<Evaluation of Thinning of Ni Plating Film> Table 3 shows the relationship between the P content contained in the Ni film and the zero-crossing time. As shown in Table 3, it was confirmed that the solder wettability was improved by adding phosphorus. In particular, when the phosphorus content is 0.1 wt % or more and 0.8 wt % or less, the solder wettability is greatly improved. In addition, in general, Pb-free solder has poorer solder wettability than Pb-Sn solder, but it was confirmed that even when Pb-free solder (Sn-3.0Ag-0.5Cu) was used, the solder wettability Sex is no problem.

[table 3] P concentration in Ni plating solution P content in Ni plating film zero crossing time mg/L wt% sec Comparative Example 7 0 0 no welding Example 30 5.4 0.03 2.5 Example 31 10.9 0.06 2.1 Example 32 16.3 0.08 1.8 Example 33 21.8 0.14 1.2 Example 34 32.7 0.18 0.8 Example 35 54.5 0.26 0.7 Example 36 76.3 0.35 0.6 Example 37 98.1 0.42 0.6 Example 38 109 0.56 0.8 Example 39 119.9 0.61 0.9 Example 40 163.5 0.78 1.0 Example 41 196.2 0.93 1.8

<Evaluation of Thinning of Ni Plating Film> Except that the P concentration in the Ni plating solution was set to 5.4 mg/L, 10.9 mg/L, 32.7 mg/L, 76.3 mg/L, and 119.9 mg/L, the Ni plating film thickness was changed as shown in Table 4. Evaluation samples were prepared under the same plating conditions as above. And, under the same conditions as above, the solder wettability of each sample was evaluated. In addition, regarding the thickness of the plated film of 0.13 μm, it was obtained by directly citing the results in Table 3. The results are shown in Table 4. As shown in Table 4, it was confirmed that good solder wettability can be maintained even if the film thickness of the Ni plating film is 1.0 μm or less. In addition, as the film thickness of the Ni plating film was increased, the solder wettability was improved. Therefore, the case where the film thickness exceeded 0.3 μm was not shown in the examples, but it was confirmed that there was no problem in the solder wettability.

[Table 4] P concentration in Ni plating solution P content in Ni plating film Thickness of Ni plating film zero crossing time mg/L wt% μm sec Comparative Example 8 5.4 0.03 0.01 no welding Comparative Example 9 0.032 no welding Comparative Example 10 0.048 no welding Example 42 0.101 4.3 Example 43 0.205 1.2 Example 44 0.3 0.9 Comparative Example 11 10.9 0.06 0.03 no welding Example 45 0.06 8.1 Example 31 0.13 2.1 Example 46 0.194 1.2 Example 47 0.294 0.7 Comparative Example 12 32.7 0.18 0.033 no welding Example 48 0.06 1.1 Example 34 0.13 0.8 Example 49 0.19 0.8 Example 50 0.301 0.7 Example 51 76.3 0.35 0.04 0.8 Example 52 0.59 0.7 Example 36 0.13 0.6 Example 53 0.21 0.6 Example 54 0.29 0.7 Example 55 119.9 0.61 0.037 1.1 Example 56 0.82 0.9 Example 39 0.13 0.9 Example 57 0.2 0.6 Example 58 0.293 0.7

<Formation of Metal Impact Plating> As a pretreatment, electrolytic degreasing (liquid temperature: 68° C., current density: 10 A/dm ² , immersion time: 60 seconds) was performed on a lead frame made of a Cu alloy, and then, After pickling (5 vol.% sulfuric acid, 30 seconds), it was washed with pure water. Ni plating, Pd impact plating, Pd plating, and Au plating were sequentially performed on the lead frame after the pretreatment. At this time, the P concentration in the Ni plating solution was changed to adjust the evaluation sample. In addition, Ni plating, Pd plating, and Au plating were performed under the same conditions as above, and the impact plating was set as follows.

(Pd impact plating conditions) Plating bath: Pd impact plating solution Pd concentration: 1.5 g/L Current density: 1.5 A/dm ² Bath temperature: 50°C pH value: 9 Target film thickness: 0.001 μm Anode: iridium oxide

<Evaluation of Thinning of Ni Plating Film> Table 5 shows the relationship between the P content contained in the Ni film and the zero-crossing time. As shown in Table 5, it was confirmed that the solder wettability was improved by adding phosphorus. In particular, when the phosphorus content is 0.1 wt % or more and 0.8 wt % or less, the solder wettability is greatly improved. In addition, in general, Pb-free solder has poorer solder wettability than Pb-Sn solder, but it was confirmed that even when Pb-free solder (Sn-3.0Ag-0.5Cu) was used, the solder wettability Sex is no problem.

[table 5] P concentration in Ni plating solution P content in Ni plating film zero crossing time mg/L wt% sec Comparative Example 13 0 0 no welding Example 59 5.4 0.03 2.7 Example 60 10.9 0.06 2.4 Example 61 16.3 0.08 1.5 Example 62 21.8 0.14 1.2 Example 63 32.7 0.18 0.8 Example 64 54.5 0.26 0.8 Example 65 76.3 0.35 0.8 Example 66 98.1 0.42 0.7 Example 67 109 0.56 0.8 Example 68 119.9 0.61 0.9 Example 69 163.5 0.78 1.1 Example 70 196.2 0.93 2.0

<Evaluation of Thinning of Ni Plating Film> Except that the P concentration in the Ni plating solution was set to 5.4 mg/L, 10.9 mg/L, 32.7 mg/L, 76.3 mg/L, and 119.9 mg/L, the Ni plating film thickness was changed as shown in Table 6. Evaluation samples were prepared under the same plating conditions as above. And, under the same conditions as above, the solder wettability of each sample was evaluated. In addition, regarding the thickness of the plated film of 0.13 μm, it was obtained by directly referencing the results in Table 5. The results are shown in Table 6. As shown in Table 6, it was confirmed that good solder wettability can be maintained even if the film thickness of the Ni plating film is 1.0 μm or less. In addition, as the film thickness of the Ni plating film was increased, the solder wettability was improved. Therefore, the case where the film thickness exceeded 0.3 μm was not shown in the examples, but it was confirmed that there was no problem in the solder wettability.

[Table 6] P concentration in Ni plating solution P content in Ni plating film Thickness of Ni plating film zero crossing time mg/L wt% μm sec Comparative Example 14 5.4 0.03 0.015 no welding Comparative Example 15 0.027 no welding Comparative Example 16 0.045 no welding Example 71 0.1 5.1 Example 72 0.21 1.5 Example 73 0.29 1.0 Comparative Example 17 10.9 0.06 0.028 no welding Example 16 0.06 8.4 Example 60 0.13 2.4 Example 74 0.201 1.4 Example 75 0.3 0.9 Comparative Example 18 32.7 0.18 0.034 no welding Example 76 0.064 1.1 Example 63 0.13 0.8 Example 77 0.192 0.8 Example 78 0.305 0.7 Example 79 76.3 0.35 0.037 0.9 Example 80 0.58 0.8 Example 65 0.13 0.8 Example 81 0.2 0.7 Example 82 0.303 0.7 Example 83 119.9 0.61 0.038 1.0 Example 84 0.83 0.9 Example 68 0.13 0.9 Example 85 0.22 0.7 Example 86 0.3 0.6

<Formation of Metal Impact Plating> As a pretreatment, electrolytic degreasing (liquid temperature: 68° C., current density: 10 A/dm ² , immersion time: 60 seconds) was performed on a lead frame made of a Cu alloy, and then, After pickling (5 vol.% sulfuric acid, 30 seconds), it was washed with pure water. Ni plating, Pd plating, Au impact plating, and Au plating were sequentially performed on the lead frame after the pretreatment. At this time, the P concentration in the Ni plating solution was changed to adjust the evaluation sample. In addition, Ni plating, Pd plating, and Au plating were performed under the same conditions as above, and the impact plating was set as follows.

(Au impact plating conditions) Plating bath: Au impact plating solution Au concentration: 1.0 g/L Current density: 5 A/dm ² Bath temperature: 50°C pH value: 4 Target film thickness: 0.001 μm Anode: iridium oxide

<Evaluation of Thinning of Ni Plating Film> Table 7 shows the relationship between the P content contained in the Ni film and the zero-crossing time. As shown in Table 7, it was confirmed that the solder wettability was improved by adding phosphorus. In particular, when the phosphorus content is 0.1 wt % or more and 0.8 wt % or less, the solder wettability is greatly improved. In addition, in general, Pb-free solder has poorer solder wettability than Pb-Sn solder, but it was confirmed that even when Pb-free solder (Sn-3.0Ag-0.5Cu) was used, the solder wettability Sex is no problem.

[Table 7] P concentration in Ni plating solution P content in Ni plating film zero crossing time mg/L wt% sec Comparative Example 19 0 0 no welding Example 88 5.4 0.03 2.7 Example 89 10.9 0.06 2.3 Example 90 16.3 0.08 1.7 Example 91 21.8 0.14 1.2 Example 92 32.7 0.18 0.9 Example 93 54.5 0.26 0.8 Example 94 76.3 0.35 0.8 Example 95 98.1 0.42 0.7 Example 96 109 0.56 0.7 Example 97 119.9 0.61 0.8 Example 98 163.5 0.78 1.1 Example 99 196.2 0.93 2.0

<Evaluation of Thinning of Ni Plating Film> Except that the P concentration in the Ni plating solution was set to 5.4 mg/L, 10.9 mg/L, 32.7 mg/L, 76.3 mg/L, and 119.9 mg/L, and the Ni plating film thickness was changed as shown in Table 8, Evaluation samples were prepared under the same plating conditions as above. And, under the same conditions as above, the solder wettability of each sample was evaluated. In addition, regarding the thickness of the plated film of 0.13 μm, it was obtained by directly referencing the results in Table 7. The results are shown in Table 8. As shown in Table 8, it was confirmed that good solder wettability can be maintained even if the film thickness of the Ni plating film is 1.0 μm or less. In addition, as the film thickness of the Ni plating film was increased, the solder wettability was improved. Therefore, the case where the film thickness exceeded 0.3 μm was not shown in the examples, but it was confirmed that there was no problem in the solder wettability.

[Table 8] P concentration in Ni plating solution P content in Ni plating film Thickness of Ni plating film zero crossing time mg/L wt% μm sec Comparative Example 20 5.4 0.03 0.011 no welding Comparative Example 21 0.034 no welding Comparative Example 22 0.051 no welding Example 100 0.11 5.3 Example 101 0.204 1.4 Example 102 0.3 1.0 Comparative Example 23 10.9 0.06 0.03 no welding Example 103 0.055 8.5 Example 89 0.13 2.3 Example 104 0.2 1.3 Example 105 0.3 0.9 Comparative Example 24 32.7 0.18 0.034 no welding Example 106 0.059 1.2 Example 92 0.13 0.9 Example 107 0.19 0.9 Example 108 0.3 0.7 Example 109 76.3 0.35 0.039 0.9 Example 110 0.57 0.9 Example 94 0.13 0.8 Example 111 0.21 0.7 Example 112 0.3 0.7 Example 113 119.9 0.61 0.039 1.0 Example 114 0.84 0.9 Example 97 0.13 0.8 Example 115 0.19 0.8 Example 116 0.31 0.7 [Industrial Availability]

The present invention has an excellent effect of being able to obtain a Ni plating film having excellent solder wettability. In addition, it has the excellent effect of being able to maintain good solder wettability and to achieve the thinning of the Ni plating film. The plating film and the plating film structure of the present invention can be used for lead frames, printed wiring boards, rigid substrates, flexible substrates, tape carriers, connectors, power devices, wires, pins, and the like.

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Claims (6)

A plating structure includes: a substrate made of Cu or a Cu alloy; a Ni plating film formed on the substrate; a Pd plating film formed on the Ni plating film; and an Au plating film , which is formed on the Pd plating film; the above-mentioned Ni plating film contains 0.01 wt% or more and 1.0 wt% or less of P, and when the P content is more than 0.01 wt% and less than 0.05 wt%, the above-mentioned Ni plating film film When the thickness is 0.1 μm or more and 10 μm or less, when the P content is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the Ni electroplated film is 0.06 μm or more and 10 μm or less, and the P content is 0.2 wt% or more And when it is 1.0 wt% or less, the film thickness of the above-mentioned Ni plating film is 0.01 μm or more and 10 μm or less. A plated structure comprising: a substrate made of Cu or a Cu alloy; a Ni plated film formed on the substrate; and a Pd plated film formed on the Ni plated film; wherein the Ni The electroplating film contains 0.01 wt% or more and 1.0 wt% or less of P. When the P content is more than 0.01 wt% and less than 0.05 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.1 μm or more and 10 μm or less. When the content of P is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.06 μm or more and 10 μm or less, and when the content of P is 0.2 wt% or more and 1.0 wt% or less, the above Ni electroplating film has a thickness of 0.06 μm or more and 10 μm or less. The film thickness of the film is 0.01 μm or more and 10 μm or less. A plated structure comprising: a substrate made of Cu or a Cu alloy; a Ni plated film formed on the substrate; and an Au plated film formed on the Ni plated film; wherein the Ni The electroplating film contains 0.01 wt% or more and 1.0 wt% or less of P. When the P content is more than 0.01 wt% and less than 0.05 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.1 μm or more and 10 μm or less. When the content of P is 0.05 wt% or more and less than 0.2 wt%, the film thickness of the above-mentioned Ni electroplating film is 0.06 μm or more and 10 μm or less, and when the content of P is 0.2 wt% or more and 1.0 wt% or less, the above Ni electroplating film has a thickness of 0.06 μm or more and 10 μm or less. The film thickness of the film is 0.01 μm or more and 10 μm or less. The plated structure according to any one of claims 1 to 3, wherein a metal impact plated film composed of any one of Au, Ag, Pd, and Cu is formed as the underlayer of the Ni plated film. The plated structure according to any one of claims 1 to 4, wherein a metal impact composed of any one of Au, Ag, and Pd is formed as a bottom layer of the Pd plated film and/or the Au plated film. plated film. A lead frame provided with the plated structure of any one of claims 1 to 5.