JP2010048697A - Oxidizability analysis method and device of metal surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a simple method capable of executing quantitative determination and identification of an oxide layer generated on the surface of a metal material, such as a lead frame, even at a manufacturing site. <P>SOLUTION: A flat metal material is heated in the air as a cathode; an anode is set as an insoluble electrode and is immersed in an electrolyte, namely, an alkaline solution containing not less than a 0.5 mol/L lithium ions; a relation between potential and a reduction current is obtained by a potential scanning method for regulating the potential between a reference electrode immersed into the electrolyte and the cathode; and an oxide generated on the surface of the flat metal material is analyzed by the potential, shape, and area of the peak of the reduction current obtained from the relation between the potential and the reduction current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to analyzing the oxidation of the surface of a metal material such as a lead frame, and more specifically, a method for electrochemically analyzing the state in which the surface of such a metal material is oxidized by a thermal history or the like, and It is related with the apparatus used for it.

  In the electronics industry, various metal materials such as lead frames and copper foils are used as materials for forming electric circuits. As a metal material forming such an electric circuit, copper is mainly used because of its extremely high electric conductivity and low price. Moreover, in order to provide characteristics, such as easy workability and mechanical strength, it may be used as a copper alloy. These are processed into the form of a plate-like material or foil, and further combined with other metal materials or organic materials to be formed as electronic components such as semiconductor packages and printed boards. The form of the combination is, for example, soldering, resin laminate, resin mold or the like.

  When such a metal material is used in combination with another metal material or an organic material, the adhesion between the materials is important, and it is often damaged by an oxide layer formed on the surface of the metal material. For example, if soldering is performed when the oxide layer is formed thick, the solder does not wet and spread on the surface even when a flux or the like is applied, which tends to cause poor soldering.

  An example of a lead frame in which the surface oxide layer is involved in adhesion will be described. The lead frame is formed by etching or stamping a plate-like material made of copper, copper alloy, or the like, and forming a lead pattern that becomes a circuit by stamping. The lead pattern is an inner lead that is bonded to a semiconductor terminal by wire bonding, and a printed circuit board. There are outer leads that serve as connecting terminals to When wire bonding a semiconductor to an inner lead, a heat history of a maximum temperature of 180 to 400 ° C. is passed through the steps of die bonding for fixing a semiconductor chip with a die paste and wire bonding between a semiconductor terminal and an inner lead. The conditions vary depending on the materials used and the conditions set by the parties. Since this step is performed in the atmosphere, the exposed portion of the lead frame where copper or copper alloy is exposed to air oxidation generates an oxide layer on the surface. After wire bonding of the semiconductor chip, the inner lead portion is entirely molded with resin. However, when the oxide layer becomes thick in the thermal history, the adhesion between the lead and the mold resin is impaired after the molding process, and peeling occurs. In such a peeling portion, penetration of moisture or the like in the environment occurs, or a package crack starting from the portion due to a temperature difference in the operating environment or the like becomes a defect of the electronic component.

The growth state of the oxide layer on the copper surface generated by the thermal history as described above varies depending on not only the thermal history conditions (temperature and time) but also the components of the copper material and the surface state of the surface. In Non-Patent Document 1, focusing on the copper alloy composition and surface state of the material, the mechanism of oxide film formation and delamination was investigated, and the oxide generated on the surface was not cuprous oxide (Cu ₂ O) but oxidized. It is shown that cupric copper (CuO) affects the decrease in adhesion. It has been shown that the composition of such oxides varies with the composition of the copper material.

  In the manufacture of lead frames, copper alloy materials with different compositions are used as necessary, but after forming the lead pattern, thin copper plating (copper strike plating) is performed to make the composition of the surface pure copper as a whole. There is a case. By this step, the surface composition becomes relatively uniform, but a slight change in the surface state due to fluctuations in the copper plating conditions remains. After this process, the inner lead part is masked so that the silver plating solution is in contact with only the necessary part, and then "partial silver plating" is performed. It is removed in the “silver removal” step. In this way, in the lead frame manufacturing process, the surface of the material comes into contact with various chemicals, and the state of contamination of the surface changes depending on the processing conditions and cleaning conditions. The state of the oxide layer generated on the surface due to the history changes. This phenomenon can be confirmed by the state of discoloration of the lead frame surface after the thermal history. For example, when a thick oxide layer is formed, the surface becomes blackish brown, and such an oxide layer has poor adhesion to the material, so if you stick an adhesive tape on it and peel it off, the tape will oxidize The material layer is transferred. When the oxide layer is thin, the surface is brown, and the oxide film layer is not transferred to the tape even when the test using the tape is performed.

  Further, in the manufacture of the lead frame, after the above process, a discoloration preventing process is performed as necessary. This is because it is stored for a long period before it is shipped after the lead frame is manufactured and mounted on the semiconductor. It is. However, this adsorbs the component of the anti-discoloring agent on the surface of the lead frame, and depending on the component, there is a component that promotes surface oxidation and deteriorates adhesion in the resin mold due to thermal history in semiconductor mounting. Therefore, care must be taken in application.

  As described above, the state of the surface oxide film generated by the thermal history is affected by the state of the surface of the copper material, but since there are a variety of factors that change the surface state, it is necessary to manage the surface state. It is. In general, surface analysis methods include instrumental analysis using spectrophotometric methods such as XPS and Auger, and surface observation using an electron microscope. It is not suitable for implementation.

  As a simple method for analyzing a metal surface oxide, Patent Document 1 discloses a technique of analyzing an oxide on the surface of a metal part using a continuous electrochemical reduction analysis method (SERA method). In this method, a plate-shaped metal material placed in contact with a cathode with a high hydrogen overvoltage is placed in the electrolyte, and a current is passed between the anodes of the insoluble electrodes, so that the metal oxide on the surface of the plate-shaped metal material is continuously formed. The voltage and the reduction current are measured as a function of time. The measured value is analyzed to analyze the solderability of the plate-shaped metal material, that is, the state of the oxide generated on the surface. Here, a conventional electrochemical method called chronopotentiometry is applied, and a constant current is applied to the system to measure the potential response. A time-electrode potential curve is mainly obtained as a measurement result. Since the electrode potential shows a potential value corresponding to the reduction reaction of the oxide layer existing on the surface, the reaction can be identified. For example, when two types of oxide layers of cupric oxide and cuprous oxide are present on the surface, the time-electrode potential curve has a stepped shape, and the oxide species of the oxide species varies depending on the elapsed time of the corresponding electrode potential. You can know the abundance.

The known literature is described below.
Journal of Japan Institute of Circuit Packaging 11 (6) 423-428 (1996) JP-A-6-331598

  In the case of a metal material such as a lead frame, analysis and management of an oxide layer formed on the surface of the metal material is important. However, simple methods that can be carried out at the manufacturing site are limited. In Patent Document 1, analysis can be performed relatively easily using an electrochemical technique in the SERA method. However, this method is an application of the chronopotentiometry method, and a time-electrode potential curve is mainly obtained as a measurement result, but it is difficult to obtain a clear stepped form in an actual system. It is. The change from the flat part to the next flat part may be slow, and it is difficult to determine the oxide layer. In addition, the potential indicated by the flat region does not necessarily match the ideal electrode potential value, and identification may be difficult.

  One form of the present invention for solving the above problem is a method for analyzing a state in which a plate-like metal material with copper exposed on the surface is oxidized by a thermal history of 180 ° C. or more. An alkaline aqueous solution containing 0.5 mol / L or more lithium ions, the cathode of which is the same as the above-mentioned heat history or heated in air at a temperature equal to or higher than the maximum temperature, the cathode, the insoluble electrode as the anode The relationship between the potential and the reduction current was obtained by the potential scanning method in which the potential between the reference electrode and the cathode immersed in the electrolyte was regulated, and the potential between the reference electrode and the cathode was regulated. It is a metal surface oxidation analysis method characterized by distinguishing oxides generated on the surface of a plate-like metal material by the potential, shape, and area of a reduction current peak.

  In this method, the potential scanning method is used to obtain the relationship between the potential and the reduction current, and the measurement result appears in the form of a reduction current peak at the potential corresponding to the reaction, so that the analysis of the result can be clarified. In addition, the reduction current peak separation can be further improved by using an alkaline aqueous solution containing 0.5 mol / L or more of lithium ions as the electrolytic solution.

  In the present invention, the plate-shaped metal material forms a lead pattern to be a circuit by etching or stamping, and at least the entire surface is subjected to copper strike plating treatment, partial silver plating treatment, and silver peeling treatment. The metal surface oxidation analysis method is characterized in that the lead frame is subjected to a discoloration prevention treatment accordingly.

  In addition, in the present invention, in order to analyze oxides generated on the surface of a metal material, the metal material in which the oxide is generated is used as a cathode, an insoluble electrode is used as an anode, and 0.5 mol / L or more of lithium ions A function of determining the relationship between the potential and the reduction current by a potential scanning method in which the potential between the reference electrode and the cathode immersed in the electrolyte solution, which is an alkaline aqueous solution containing the electrolyte, is regulated, and the potential and the reduction current Thus, the metal surface oxide analyzer has a function of obtaining the composition and thickness of the oxide based on the potential, magnitude, and area of the reduction current peak.

  In the present invention, in the obtained potential-reduction current curve, the result appears in the form of a reduction current peak at the potential corresponding to the reaction. Therefore, the analysis of the result can be clarified using the potential, shape, and reduction current peak area. .

  In the present invention, the function for obtaining the relationship between the potential and the reduction current by the potential scanning method is at least a potentiostat, a function generator, a measurement data recording device, an analysis computer, and a reduction from the relationship between the potential and the reduction current. The metal surface oxide analyzer is characterized by comprising software having a function of analyzing the position, shape and area of a current peak to determine the composition and thickness of the oxide.

  In the method for analyzing the oxidizability of the metal surface according to the present invention, since the result appears in the form of a reduction current peak at the potential corresponding to the reaction in the obtained potential-reduction current curve, the potential, shape and reduction current peak area are used. Thus, the characteristics of the oxide generated on the surface of the metal material can be clearly distinguished. As a result, the present invention is a simple method capable of analyzing and managing the oxide layer generated on the surface of the metal material even at the manufacturing site, and further has an effect that the analysis of the measurement result can be made clearer than before. . In particular, in the lead frame, the surface state changes through many steps, which has a great influence on the formation of an oxide film layer when subjected to a thermal history. Clearly obtained.

  A metal surface oxidation analysis method and oxide analysis apparatus according to the present invention will be described below based on an embodiment thereof. FIG. 1 is a schematic view of an electrochemical measurement apparatus for analyzing the oxidizability of a metal surface according to the present embodiment. The plate-shaped metal material 1 having an oxide film layer is immersed together with an insoluble electrode 3 and a reference electrode 4 as a cathode in an electrolytic solution 2 added to the container. The terminals of the potentiostat 5 are connected to these electrodes. The potentiostat 5 is supplied with a voltage necessary for performing the potential scanning method from the function generator 6. This voltage is applied to the electrode through the potentiostat 5, and the reduction current value at the corresponding electrode is measured in the potentiostat 5. The potentiostat 5 is provided with a measurement data recording device 7 and records the obtained reduction current value corresponding to the voltage value. In this way, the relationship between the voltage applied to the plate-like metal material 1 serving as the cathode and the reduction current obtained as a signal is obtained. The relationship between the voltage and the reduction current recorded in the measurement data recording device 7 is analyzed by the analysis computer 8. Although the measurement data recording device 7 may be built in the analysis computer 8, it may be installed separately. Software for analyzing the composition and thickness of the oxide is installed in the analysis computer 8 and used for analyzing the result obtained by the measurement.

(Electrochemical measurement conditions)
FIG. 2 shows an example of a potential-reduction current curve obtained by the method of the present embodiment using the apparatus having the configuration shown in FIG. This is a measurement result of the plate-shaped metal material 1 obtained by heating an oxygen-free copper plate at a temperature of 300 ° C. for 60 minutes in the air. The electrochemical measurement conditions of this embodiment are as follows: the electrolytic solution 2 uses an alkaline aqueous solution containing 1 mol / L lithium hydroxide and 6 mol / L potassium hydroxide, the insoluble electrode 3 of the anode is a platinum-plated titanium electrode, and the reference electrode 4 Used silver / silver chloride electrodes. In the measurement, the operation of scanning the potential at a constant rate of 10 mV / s from −0.7 (V vs. Ag / AgCl) to −1.6 (V vs. Ag / AgCl) is repeated twice in succession. When the first potential scan is performed, the oxide on the surface of the plate-shaped metal material 1 is reduced to metallic copper. Therefore, the current measured in the first potential scan is the sum of the oxide reduction current and the other reaction current (water reduction current, impurity reduction current, etc.). When the second potential scan is performed in the state where the first potential scan is finished, the oxide on the surface of the plate-like metal material 1 has already disappeared. Only the current of the reaction is measured. Therefore, the relationship between the potential and the reduction current of the oxide is obtained by subtracting the current value of the second potential scan from the current value of the first potential scan at the same potential value.

(CuO reduction current peak and Cu ₂ O reduction current peak in the potential-reduction current curve)
In the graph of FIG. 2 obtained by this measurement, several reduction current peaks (of a negative value of the reduction current) can be found. These are current peaks representing reduction of oxides generated on the surface of the plate-shaped metal material 1 by the heat treatment. In the literature (S. Nakayama et.al J. Electrochem. Soc, 148 (11) B467 (2001)), an alkaline aqueous solution containing 1 mol / L lithium hydroxide and 6 mol / L potassium hydroxide as the electrolyte 2 is used. The assignment of the reduction current peak at -0.95 to -1.1 (V vs. Ag / AgCl) is shown for CuO and -1.3 to -1.5 (V
vs. Ag / AgCl), a Cu ₂ O reduction current peak appears. In the reduction current peak appearing in FIG. 2, the potential at which the reduction current peak appears is slightly shifted from this region, and if there are shoulders or small reduction current peaks, the number of reduction current peaks is two. However, this is not the case when the degree of oxygen defects in copper oxide (CuO) or cuprous oxide (Cu ₂ O) constituting the oxide film is different and the crystal type is reduced to metallic copper. The reduction potential is considered to change slightly. Eventually, the reduction current peak of CuO appeared on the low potential side of -0.7 to -1.1 (V vs. Ag / AgCl) and Cu ₂ O on the high potential side of -1.1 to -1.5 (V vs. Ag / AgCl). It is thought that there is.

From the amount of electricity of these reduction current peaks (integrated amount of reduction current), the thickness of the oxide film is composed (Cu
O and Cu ₂ O) can be obtained separately. This is because the reduction reaction of the oxide film in this measurement, CuO is on the low potential side of -0.7 to -1.1 (V vs. Ag / AgCl),
_{CuO + H 2 O + 2e →} Cu + 2OH - (1)
Cu ₂ O is on the high potential side of −1.1 to −1.5 (V vs. Ag / AgCl),
_{Cu 2 O + H 2 O +} 2e → 2Cu + 2OH - (2)
Therefore, the electric quantity obtained from the potential-reduction current curve is obtained by taking into consideration the specific gravity (CuO: 6.4, Cu ₂ O: 6.0) of the oxide film layer from the theoretical calculation using the Faraday equation. That is, the electric quantity on the low potential side of -0.7 to -1.1 (V vs. Ag / AgCl) is A (C), and the electric quantity on the high potential side of -1.1 to -1.5 (V vs. Ag / AgCl) is B. When (C) and the surface area of the sheet metal material 1 is S (cm ² ),
CuO film thickness (nm) = 260 * A / S (3)
Cu ₂ O film thickness (nm) = 500 * B / S (4)
It becomes.

  In the present embodiment, the metal material from which copper is exposed is heated to form an oxide film layer on the surface. This condition is that a thermal history of 180 ° C. or higher is passed in the atmosphere. The time is appropriately set depending on the purpose of use of the material. Below 180 ° C., it is difficult to form an oxide film layer in an amount detectable by measurement on the copper surface, so a temperature higher than that is appropriate. The upper limit does not need to be set in particular, but in the present embodiment, it is intended to analyze the characteristics of the copper material used for applications such as electronics, so unnecessary high temperature setting is meaningless. In addition, the time should be set in consideration of the temperature so as to obtain an oxide film in such an amount that a clear reduction current peak can be obtained in the measurement.

The electrochemical measurement conditions described above in (Electrochemical measurement conditions) are appropriate, and the details will be supplemented. The measurement may be performed at room temperature, but 15 to 30 ° C. is desirable. Usually, the measurement cell uses a container in which about 50 to 500 mL of the electrolyte 2 is stored. The insoluble electrode 3 is suitably platinum, platinum-plated titanium, iridium oxide electrode, or the like. In addition, a metal material that does not dissolve in an alkaline solution such as nickel or stainless steel can be used. The reference electrode 4 is most easily a silver / silver chloride electrode, but a saturated calomel electrode (SCE), a standard mercury oxide electrode, or the like can also be used. The size of the cathode and insoluble electrode 3 that is the plate-like metal material 1 is appropriately about 5 to 50 cm ² in terms of surface area, although it depends on the size of the container. The plate-shaped metal material 1, the insoluble electrode 3, and the reference electrode 4 are preferably attached to a jig so that their relative positions can be fixed. In addition, the plate-shaped metal material 1 is fixed so that the surface area of the portion in contact with the electrolytic solution 2 does not change during the measurement. The potential scanning speed can vary from 0.1 to 1000 mV / s, but 1 to 100 mV / s is particularly suitable.

  The software having the function of obtaining the composition and thickness of the oxide installed in the analysis computer 8 is based on the potential-reduction current curve data acquired in a series of measurements, from -0.7 to -1.1 (V) and -1.1. Set a potential range of -1.5 (V) and calculate the amount of electricity on the low potential side of -0.7 to -1.1 (V) and the amount of electricity on the high potential side of -1.1 to -1.5 (V), ( It is converted into the thickness of each oxide film from the equations 3) and (4). Moreover, it is desirable to have functions such as reduction current peak recognition and reduction current peak separation for analysis of the shape of the potential-reduction current curve.

Hereinafter, details and effects of the present invention will be described with reference to examples.
<Example 1>
The same oxygen-free copper plate-like metal material 1 was given a thermal history in air under the following different conditions, and a potential-reduction current curve was obtained using a measurement sample.
Sample number Temperature Time (1) 300 ° C., 60 minutes (2) 300 ° C., 40 minutes (3) 300 ° C., 10 minutes Measurement was performed with an alkaline aqueous solution containing 1 mol / L lithium hydroxide and 6 mol / L potassium hydroxide. Is the electrolyte solution 2 and the platinum-plated titanium plate is the insoluble electrode 3 of the anode. The potential scanning method was performed by regulating the potential between the reference electrode 4 immersed in the electrolyte 2 together with the insoluble electrode 3 and the plate-like metal material 1 as the cathode. Here, the operation of scanning the potential between the immersed reference electrode 4 and the cathode from −0.7 to −1.6 (V vs. Ag / AgCl) at a constant rate of 10 mV / s is repeated twice. The relationship between the potential and the reduction current of the oxide was obtained by subtracting the current value of the second potential scan from the current value of the first potential scan at the same potential value. 2, 3 and 4 are potential-reduction current curves obtained for the plate-shaped metal material 1 of the measurement samples of (1), (2) and (3), respectively.

2, 3, and 4, a reduction current peak or a shoulder appears at the following potential, respectively.
Figure Number Shape Potential Intensity Figure 2 Reduction current peak -0.96 (Vvs.Ag/AgCl) Weak
Shoulder -1.25 (Vvs.Ag/AgCl) Weak
Reduction current peak -1.38 (Vvs.Ag/AgCl) Strong figure 3 Reduction current peak -0.96 (Vvs.Ag/AgCl) Medium
Fig. 4 Reduction current peak -1.25 (Vvs.Ag/AgCl) Medium Fig. 4 Reduction current peak -1.25 (Vvs.Ag/AgCl) Medium These reduction current peaks and shoulders are based on the potential, (1) -0.96 (Vvs.Ag/ AgCl), (2) -1.25 (Vvs.Ag/AgCl), and (3) -1.38 (Vvs.Ag/AgCl). As described in the explanation of (CuO reduction current peak and Cu ₂ O reduction current peak in the potential-reduction current curve), these reduction current peaks are from −0.7 to −1.1 (V vs. Ag / AgCl). It is considered that the reduction current peak of Cu ₂ O appears on the high potential side of CuO, −1.1 to −1.5 (V vs. Ag / AgCl) on the low potential side. Measurement samples (1) to (3) show changes over time in the order of (3) → (2) → (1), and when the time is short, −1.25 (Vvs.Ag/AgCl) Although the reduction current peak of Cu ₂ O appears, when the heating time is extended, as shown in FIG. 3, a reduction current peak of −0.96 (Vvs.Ag/AgCl) of CuO appears, and in 60 minutes, FIG. as in, CuO of -0.96 (Vvs.Ag/AgCl), the reduction current peak of Cu ₂ O in -1.25 (Vvs.Ag/AgCl) becomes smaller, Cu ₂ O of -1.38 (Vvs.Ag/AgCl) It can be seen that the reduction current peak becomes dominant. As described above, it can be seen from FIGS. 2 to 4 that the state of the oxide film is remarkably changed by the thermal history of the plate-like metal material 1 by the method of this embodiment. However, the change due to the thermal history is a result of the oxygen-free copper plate used here, and the tendency varies depending on the copper crystal state of the material and the state of surface contamination.

Table 1 shows CuO and Cu ₂ O obtained from the results of FIGS. This was obtained from the equations (3) and (4), and the thickness of the oxide film could be easily obtained quantitatively by this example.

<Example 2>
The Example which applied this invention with respect to the plate-shaped metal material 1 which is a lead frame which consists of copper alloys is shown. A plate-like metal material 1 with a lead pattern that forms a circuit by etching or stamping copper alloy material EFTEC64T (Furukawa Electric) on three different times, electrolytic degreasing, copper strike plating, partial silver plating, silver The plate-shaped metal material 1 which performed the peeling process and the discoloration prevention process sequentially was produced. After imparting a thermal history at 320 ° C. for 10 minutes in the atmosphere, they were subjected to electrochemical measurement by the same potential scanning method as in Example 1. The results are shown in FIG. 5 as the reduction current density per area of the plate-like metal material 1. In both cases, the reduction current peak of Cu ₂ O of −1.38 (Vvs.Ag/AgCl) appears dominantly, but the area of the reduction current peak (the horizontal axis is the potential and the vertical axis is the reduction current density). The area of the shape of the reduction current peak in the graph is different, and the presence or absence and shape of the reduction current peak at other potentials are different, so that each feature can be distinguished and the difference in the oxide film can be grasped. Thus, according to the present invention, it is possible to clearly distinguish and grasp the characteristics of the oxide film formed on the surface of the metal material.

It is the schematic of the electrochemical measuring apparatus for performing the oxidation analysis method of the metal surface of this invention. 1 is a potential-reduction current curve obtained by the method of the present invention using the apparatus having the configuration shown in FIG. 1, and is a measurement result of a plate-like metal material obtained by heating an oxygen-free copper plate at a temperature of 300 ° C. for 60 minutes in the atmosphere. . 1 is a potential-reduction current curve obtained by the method of the present invention using the apparatus having the configuration shown in FIG. 1, and is a measurement result of a plate-shaped metal material obtained by heating an oxygen-free copper plate at a temperature of 300 ° C. for 40 minutes in the atmosphere. . 1 is a potential-reduction current curve obtained by the method of the present invention using the apparatus having the configuration shown in FIG. 1, and is a measurement result of a plate-like metal material obtained by heating an oxygen-free copper plate at a temperature of 300 ° C. for 10 minutes in the atmosphere. . The lead frame was given a heat history at 320 ° C. for 10 minutes in the air with a plate metal material sequentially subjected to electrolytic degreasing, copper strike plating, partial silver plating, silver peeling treatment, and discoloration prevention treatment at three different dates and times. FIG. 2 is a potential-reduction current density curve obtained using the apparatus having the configuration shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plate-shaped metal material 2 ... Electrolytic solution 3 ... Insoluble electrode 4 ... Reference electrode 5 ... Potentiostat 6 ... Function generator 7 ... Measurement data recording device 8 ...・ Analysis computer

Claims (4)

  This is a method for analyzing the state in which the surface of the plate-like metal material with copper exposed is oxidized by the thermal history of 180 ° C. or higher. Heated in air at a temperature higher than the temperature as a cathode, the insoluble electrode as an anode, immersed in an electrolytic solution that is an alkaline aqueous solution containing 0.5 mol / L or more of lithium ions, and both immersed in the electrolytic solution The relationship between the potential and the reduction current is obtained by a potential scanning method in which the potential between the reference electrode and the cathode is regulated, and the reduction metal peak potential, shape, and area obtained from the relationship between the potential and the reduction current are obtained as a plate-like metal material. A method for analyzing the oxidizability of a metal surface, comprising distinguishing oxides formed on the surface of the metal.   The plate-shaped metal material forms a lead pattern to be a circuit by etching or stamping, and at least the entire surface is subjected to copper strike plating treatment, partial silver plating, silver peeling treatment, and further, anti-discoloration treatment is performed as necessary. The method for analyzing the oxidizability of a metal surface according to claim 1, wherein the lead frame is an applied lead frame.   In order to analyze the oxide generated on the surface of the metal material, an alkaline aqueous solution containing 0.5 mol / L or more of lithium ions using the metal material on which the oxide is generated as a cathode and an insoluble electrode as the anode. The function of obtaining the relationship between the potential and the reduction current by the potential scanning method that regulates the potential between the reference electrode and the cathode immersed in the electrolyte and the reference electrode and the cathode both immersed in the electrolyte, and the reduction current peak from the relationship between the potential and the reduction current An apparatus for analyzing an oxide on a metal surface, which has a function of obtaining the composition and thickness of the oxide based on the potential, size, and area of the metal.   The function of obtaining the relationship between the potential and the reduction current by the potential scanning method is at least a potentiostat, a function generator, a measurement data recording device, an analysis computer, and the position and shape of the reduction current peak from the relationship between the potential and the reduction current 4. The apparatus for analyzing an oxide on a metal surface according to claim 3, comprising software having a function of analyzing the area and obtaining the composition and thickness of the oxide.