JPH0116913B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for removing an oxide film formed on the surface of a Si-containing Cu-based alloy for electronic component materials used in electronic components such as semiconductor lead frames and terminal connectors. . [Prior art] Cu-based alloys containing Si have high conductivity, high strength, and heat resistance, so they are used for a variety of purposes, such as semiconductor lead frames and terminal connectors. . When used in semiconductor lead frames, the surface of the alloy is plated with metal, and then a gold wire or the like is pressure-welded to form a circuit.
Furthermore, when used in terminal connectors, plating with Cu, Ni, Sn, etc. is performed to improve the reliability of the contact portion. When performing such a plating treatment, if the alloy surface is not clean and, for example, oxides are present, uneven plating will occur, and the adhesion of the plating metal will decrease, which may cause the plating to peel off. Therefore, it is undesirable for oxides or the like to remain on the alloy surface, even if only in a small amount.
However, in the manufacturing process of the alloys used in the above-mentioned electronic component materials, it is common to perform annealing after cold rolling, and during annealing, an alloy plate with a thickness of 0.2 to 2 mm that is wound into a coil is inert. It is customary to perform batch annealing in a gas or reducing gas atmosphere. However, the air and moisture introduced between the alloy plates during winding cannot be completely replaced by the inert gas, and a small amount remains. Therefore, during annealing, these act as oxidizing agents, and an oxide film is formed on the surface of the alloy plate. At this time, the winding force of the coil and the gas atmosphere of the annealing furnace vary, and the amount of residual air and residual moisture is not constant, so the amount of oxide film formed also fluctuates.
As shown in the figure, an uneven selvage pattern is formed from the end of the coil 1 in the width direction due to variations in the formation of the oxide film 2. In order to suppress the formation of such an oxide film, use N ₂ gas or H ₂ with a purity of 99.9% or higher.
using gas, and the dew point is −40 for _N2 gas.
℃ or below, or below -60℃ for _H2 gas during annealing, but although these gases are expensive, they are not a fundamental solution to preventing the formation of oxide films. I wasn't getting it. For this purpose, as shown in Fig. 2, the alloy plate 1a is unwound from the annealed alloy coil, immersed in an acidic cleaning solution 3 for cleaning, and then the SiC
Polishing was performed using a buff 4 coated with abrasive grains. 5 indicates the dipping roller 3. Normally 184g/
A sulfuric acid bath of about 100% is used as a cleaning solution to remove the oxides generated during annealing, but among oxides, the SiO ₂ film is particularly difficult to remove, so it is necessary to add buffing to remove it. It was needed. [Problems to be Solved by the Invention] However, since SiO ₂ is formed as a hard film, it is difficult to remove even by buffing and tends to remain almost unchanged. For this reason, when a polished alloy coil is slittered to make a strip to be used as a material for electronic parts, if the strip has even a partial annealing pattern, the entire length of the strip is scrapped. As a result, the yield was significantly reduced. If an aqueous solution of hydrofluoric acid, a mixed solution of sulfuric acid and hydrogen peroxide, or a mixed solution of nitric acid and sulfuric acid can be used as the cleaning liquid, it is not impossible to remove SiO ₂ . However, hydrofluoric acid aqueous solution
Since the reaction rate of SiO ₂ is fast, the life of the cleaning solution is short, and since hydrogen fluoride gas is used, it is highly corrosive and unfavorable in terms of the working environment. In addition, in the case of a mixed solution of sulfuric acid and hydrogen peroxide or a mixed solution of sulfuric acid and nitric acid, alloy components may be present in the solution.
There is a problem that Cu ions may be eluted, and the cleaning solution will spontaneously decompose due to the Cu ions and lose its effectiveness as a pickling solution in a short period of time. For this reason, it becomes necessary to add an acidic solution during the process or prepare a new acidic solution and wash again. However, preparing a new bath is not only uneconomical in itself, but also has the disadvantage that adding a new acidic solution changes the etching power of hydrogen peroxide or nitric acid, resulting in a different color tone on the surface of the alloy coil. arise. In addition, hydrogen peroxide or nitric acid, which have oxidizing properties, activate the surface of the alloy coil, so they are not necessarily preferable as finishing solutions for semiconductor lead frame materials and the like that do not like rust inhibitors. There is also the problem that hydrogen peroxide gas or nitrogen oxide gas is generated during work, contaminating the work environment. The present invention has been made in view of the above circumstances, and aims to stabilize various oxides such as SiO ₂ that are generated on the alloy surface by annealing Cu-based alloys containing Si for electronic component materials. The object of the present invention is to provide a surface treatment method for alloys that can be completely removed by cleaning with a strong acidic solution. [Means for Solving the Problems] The present invention uses an acid solution to clean an oxide film formed on the alloy surface by annealing a Si-containing Cu-based alloy for electronic component materials. The gist is to use a solution containing the above acidic ammonium fluoride. [Function] The present inventors investigated various acidic solutions in order to find an acidic cleaning solution that easily reacts with SiO ₂ and is relatively stable, and found that when a solution containing 10 g or more of acidic ammonium fluoride is used, It has been found that SiO ₂ generated by annealing is almost certainly removed. In addition, when the concentration was less than 10 g/L, the immersion cleaning time became longer and the work efficiency decreased. There is no particular upper limit to the concentration of the acidic ammonium fluoride solution, but the solubility of acidic ammonium fluoride in water at room temperature (40°C) is 500g/, so if it exceeds 500g/, it will not form a suspension. Unless otherwise specified, it may be used as a saturated solution. In this way, the SiO ₂ coating can be cleaned and removed by using a solution containing acidic ammonium fluoride.
As a result of research and consideration by the present inventors, using a solution of acidic ammonium fluoride dissolved in sulfuric acid water will further improve the removal effect of the oxide film and shorten the cleaning time, rather than simply using an acidic ammonium fluoride aqueous solution. I found out that it would happen. The reason for this is thought to be that sulfuric acid acts to remove a film of Cu ₂ O, etc. that coexists with SiO ₂ . The concentration of sulfuric acid is preferably 500 g/less or less, since etching properties appear as the amount of sulfuric acid added increases, and from the economic point of view.
In this way, it has become possible to remove the oxide film to a nearly satisfactory degree, so it is no longer necessary to use expensive N ₂ gas or H ₂ gas when annealing the alloy, and an inexpensive DX gas atmosphere can be used. It was found that annealing at In other words, when annealing was performed using DX gas, a local oxide film was formed over the entire length of the strip;
The thickness of the SiO ₂ film produced by annealing at 500°C for 2 hours in a DX gas furnace is approximately 0.6 μm at most, and the SiO ₂ film is removed by cleaning with a sulfuric acid solution of acidic ammonium fluoride at a concentration of 10 g/min or more. By removing the oxidized film and polishing it further, it is possible to achieve a beautiful finish in which the areas with an oxide film and those without are completely indistinguishable, and in this case, the color tone of the surface of the strip does not change. Ta. Note that when DX gas is used, the dew point of the gas in the annealing furnace is high, and its control is relatively easy. The polishing method after cleaning the alloy plate is not limited, but it is preferable to use a rotary buff coated with SiC abrasive grains. As a result of studies conducted by the present inventors, the oxide film formed on the surface of a Cu-based alloy containing 0.01% or more of Si is mainly composed of SiO ₂ , and this SiO ₂ is robust against pickling. I found out. For this reason, it is generally extremely difficult to remove the oxide film formed on the surface of a Cu-based alloy containing 0.01% or more of SiO ₂ , but the method of the present invention can remove it even in such cases. The oxide film can be removed without difficulty. The composition of the Si-containing Cu-based alloy for electronic component materials in the present invention generally includes 0.05 to 5% Ni, and if necessary, one or more selected from the following group: is typical, but the present invention does not particularly limit the alloy composition. Zn: 0.1~5% Sn: 0.02~5% Co: 0.1~0.5% Mn: 0.01~1% Cr: 0.001~0.1% Zr: 0.001~0.1% Ti: 0.001~0.1% B: 0.001~0.1% Al: 0.001~0.1% P: 0.001~0.1% Fe: 0.01~1% Mg: 0.001~0.01% Typical examples include Cu.3.2%Ni-0.7%
Si-0.3%Zn, Cu-1.6%Ni-0.35%Si-0.3%Zn,
Cu-1%Ni-0.2%Si-0.03%P, Cu-3.2%Ni
-0.7%Si-0.3%Zn-1.25%Sn are exemplified. [Example] Example 1 A coil made of a copper alloy plate having the composition shown in sample numbers 1 to 4 in Table 1 was annealed and immersed in an acidic cleaning solution for 10 seconds to remove the oxide film formed on the alloy surface. After cleaning, polishing was performed using a rotating buff coated with SiC abrasive grains. Table 2 shows the annealing conditions, Table 3 shows the composition and concentration of the acidic cleaning solution, and Table 4 shows the test results. The variation in plate thickness after polishing was less than ±1 μm.

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Example 2 Copper alloy strips with the compositions shown in sample numbers 1, 2, and 3 in Table 1 were heated under the conditions shown in Table 2 (however, the furnace was a bell-shaped furnace).
After annealing using a DX gas furnace (with a dew point of 5 to 10°C), the material was cooled to 150°C in the furnace, and then allowed to cool to room temperature in the atmosphere. Samples were cut from the outer periphery and the inner part of these alloys and washed in a cleaning solution having the chemical composition shown in Table 5 at 20° C. for 10 seconds to obtain the results shown in Table 5. The presence or absence of SiO ₂ was determined using an ESCA analyzer, and the wettability of the solder was determined by soaking Alpha 611, which is equivalent to the flux MIL-F-14256A, in 60% Sn-Pb at 230°C for 5 seconds. , the coating status was investigated. In addition, the surface finish and color tone changes of the five test materials were investigated using the solution after eluting 50 g of Cu with Cu ₂ O.

〔Effect of the invention〕

Since the present invention is constructed as described above, the oxide film on the surface of a Cu-based alloy for electronic component materials containing Si can be
The acidic cleaning solution of the present invention can be completely removed without roughening the surface of the base material or changing the color tone of the surface of the base material. Moreover, the acidic cleaning solution of the present invention can be used semi-permanently, and the work process Management is easy because the solution can be replenished and renewed even during the process. In addition, in the method of the present invention, the acidic solution does not contain oxidizing agents such as hydrogen peroxide or nitric acid, so the finish of the alloy surface is not activated and does not easily discolor after treatment with the acidic solution, and gas generation is small. Therefore, the working environment will also be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the state of formation of an oxide film on an alloy-based coil, and FIG. 2 is a diagram showing a process for removing the oxide film. 1... Alloy coil, 2... Oxide film, 3... Cleaning liquid, 4... Buff.

Claims (1)

[Claims] 1. When cleaning the oxide film formed on the metal surface by annealing Cu-based alloys containing Si for electronic component materials with an acidic solution, 10
Si-containing material for electronic components, characterized by using a solution containing acidic ammonium fluoride in an amount of
Method for removing oxide film from Cu-based alloys.