JP6221912B2 - Copper alloy for solder joint - Google Patents

Description

  The present invention relates to a copper alloy for soldering used for soldering, for example, an external electrode of an electronic component or a semiconductor element.

  In general, an alloy at a connection destination when soldering an external electrode or the like of an electronic component or a semiconductor element is performed in a state where wettability with solder is enhanced.

  For example, when the alloy constituting the skeleton of the connection component is an Fe-42 mass% Ni alloy (42 alloy), the connection surface is plated with gold or Cu-2.4 mass% Fe-0.03 mass% In the case of P-0.12 mass% Zn (alloy 194), tin plating is further performed on the silver plating, or palladium plating is further applied on the nickel plating. For example, pure copper or a low-added copper alloy is used to improve wettability with molten solder at the time of soldering.

  By the way, in recent years, there is an increasing demand for cost reduction such as simplification of the process for increasing productivity, reduction of the number of parts, reduction of the amount of precious metal used, and the like when soldering external electrodes of electronic components and semiconductor elements. There is such a requirement for the alloy to be connected. Specifically, the silver plating region of the lead frame is limited to a narrow region necessary for wire bonding, and it is desired to omit plating of the external electrode portion for solder-joining the semiconductor package.

  For example, a method using a copper alloy containing nickel, tin, zinc, or the like has been proposed as a method for directly soldering the surface of a copper alloy constituting a semiconductor package or the like without plating (for example, Patent Documents). 1 and 2).

Japanese Patent Publication No. 07-116536 Japanese Patent No. 2858894

  However, the copper alloy described in Patent Document 1 has a copper appearance color, and there is a problem that the surface is oxidized and easily discolored when heated in the atmosphere. In this case, it is necessary to separately perform plating of gold, silver, palladium or the like. Further, in the copper alloy described in Patent Document 2, discoloration due to oxidation is suppressed by setting the nickel addition amount to 15% by mass, but when heated to about 150 ° C. in the atmosphere and an oxide film is formed on the surface. There is a problem that the solder wettability is remarkably lowered.

  A copper alloy to which nickel is added at a ratio of 10% by mass to 30% by mass is called cupro-nickel, and it is a material to be used when emphasizing appearance and weather resistance from the point of being able to suppress discoloration due to corrosion resistance and oxidation. One. However, for example, when heating at a temperature of about 150 ° C. for about 10 minutes in the atmosphere, solder wettability is remarkably deteriorated and unstable. Since cupronickel does not change as much as pure copper even when heated as described above, it cannot be judged whether or not it can be soldered based on the evaluation of the oxidation state with the naked eye, and solder bonding is performed. Was a process management problem.

  The present invention has been made in view of the above-described problems, and can suppress discoloration due to heat oxidation in the atmosphere, and also exhibits excellent solder wettability even after heating. An object of the present invention is to provide a copper alloy.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, in a copper alloy for solder joints mainly composed of copper, discoloration due to oxidation or the like can be suppressed by containing nickel at a predetermined ratio and silver at a predetermined ratio. As a result, the present invention has been completed. That is, the present invention provides the following.

  (1) The present invention is a copper for solder joints, characterized in that it contains copper as a main component, nickel is contained in a proportion of 10% by mass to 35% by mass and silver is contained in a proportion of 1% by mass to 20% by mass. It is an alloy.

  (2) The present invention also provides the solder according to the invention according to (1), wherein nickel is added in a proportion of 16% by mass to 28% by mass and silver is added in a proportion of 2% by mass to 10% by mass. It is a copper alloy for joining.

  (3) Moreover, this invention is JIS C 60068-2 using Sn-3.5 mass Ag-0.5 mass% Cu solder bath which melt | dissolves at 245 degreeC in the invention which concerns on (1) or (2). A copper alloy for solder joints, characterized in that a contact angle between the copper alloy in contact in a thermal equilibrium state and the solder bath measured by a test method according to -54 is 90 degrees or less.

  (4) Moreover, this invention is the invention which concerns on any one of (1) thru | or (3), Sn-3.5 mass fuse | melted at 245 degreeC with the said copper alloy heated for 10 minutes in the atmosphere of 150 degreeC. When the Ag-0.5 mass% Cu solder bath is in contact with a thermal equilibrium state, the contact angle between the copper alloy and the solder bath measured by a test method according to JIS C 60068-2-54 is 90. It is a copper alloy for solder joints, characterized in that it is less than or equal to the degree.

  According to the copper alloy for solder joining according to the present invention, since nickel is contained at a ratio of 10% by mass or more and 35% by mass or less, it ranges from bright and light copper color having a metallic luster to silver white, and about 150 ° C. Even when heated, it has no discoloration and a good appearance. Even when the appearance is particularly important, plating with noble metal or the like can be omitted.

  In addition, since the copper alloy for solder joint according to the present invention contains silver in a proportion of 1% by mass or more and 20% by mass or less, it is stable in solder joint even after being heated to about 150 ° C., for example. It exhibits excellent solder wettability, facilitates quality control in solder joining work, and can improve the reliability of solder joining. Therefore, it is not necessary to perform plating with silver, palladium, tin or the like for soldering.

It is a figure which shows typically the mode of the solder wettability of the copper alloy based on the relationship with the contact angle ((theta)) at the time of immersing a copper alloy in a molten solder bath.

  Hereinafter, a specific embodiment of the copper alloy for solder joint according to the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.

  The copper alloy for solder joint according to the present embodiment (hereinafter also simply referred to as “copper alloy”) is a copper alloy composed mainly of copper, and nickel and silver are added at a predetermined ratio, respectively. Contains as a component. Specifically, the copper alloy for solder bonding contains copper as a main component, nickel is contained in a proportion of 10% by mass or more and 35% by mass or less, and silver is contained in a proportion of 1% by mass or more and 20% by mass or less. It is characterized by becoming. In addition, a main component means that the content rate is 51 mass% or more.

  Here, when performing the soldering process by the reflow method, the substrate containing the copper alloy is preheated to a high temperature of about 150 ° C. to 180 ° C. and then heated to about 230 ° C. to 250 ° C. Soldered by passing through. However, conventional copper alloys for solder joints are easily oxidized and discolored in an atmosphere containing oxygen during heating during reflow, and the solder wettability is remarkably reduced by the oxide film formed on the surface. It was impossible to solder and process control was difficult. Further, in the case of a metal / alloy using a low melting point metal such as tin or indium, it may be melted or softened by being heated to about 250 ° C.

  On the other hand, according to the copper alloy for solder bonding according to the present embodiment, as described above, it contains nickel at a predetermined ratio and also contains silver at a predetermined ratio. It is possible to effectively suppress discoloration due to heat oxidation or the like, and to have an excellent appearance. In addition, with such a copper alloy for soldering, for example, even after preheating at a high temperature in reflow soldering processing, it is possible to stably maintain excellent solder wettability and to achieve good soldering. It can be carried out.

  The copper alloy for solder bonding can be various sizes depending on the application, and the size is not particularly limited. This copper alloy for soldering can be used as a material for electronic parts used as a general electric contact material, electrode material or the like. For example, it can be manufactured by performing cutting, rolling, forging, bending, punching, polishing, etc. from a molten ingot having a predetermined component composition, which will be described later, and using the obtained copper alloy, cladding It can be processed as a material for electronic parts by processing according to the application such as welding, vapor deposition and sputtering.

  For example, a sputtering target is produced using the copper alloy for solder bonding according to the present embodiment as a raw material, and a copper alloy film constituting the outermost surface of the electrode of the electronic component is formed using the target. The copper alloy film thus formed is not discolored due to heat oxidation or the like, and exhibits excellent solder wettability even after, for example, preheating at about 150 ° C. during reflow soldering. Thus, a highly reliable solder joint can be performed.

  As described above, the copper alloy for solder bonding according to the present embodiment contains nickel in a proportion of 10% by mass to 35% by mass. In this copper alloy for soldering, nickel is contained in a proportion of 10% by mass or more and 35% by mass or less, so that the color is not a so-called red copper color of copper, but a bright and light copper color having a metallic luster to a silver white color. Such a good appearance can be obtained, and corrosion resistance and discoloration due to oxidation can be effectively suppressed. Specifically, for example, even in a state of being heated in the atmosphere at a temperature of 150 ° C. or higher for 10 minutes, a copper alloy having an excellent appearance can be obtained without causing a change in appearance color.

  With respect to the nickel content, if the nickel content in the copper alloy is less than 10% by mass, the appearance color becomes copper, and for example, when heated at a temperature of 150 ° C. or higher in the atmosphere, it easily changes color and exhibits redness. On the other hand, if the nickel content exceeds 35% by mass, the electrical specific resistance of pure titanium showing the same silver white color exceeds 40 μΩcm. For example, when the copper alloy is used as a part of an electrode material, Electrical characteristics may be deteriorated.

  Moreover, as content of nickel, it is more preferable that it is 16 to 28 mass%. When the nickel content is within such a range, a copper alloy having a better appearance can be obtained.

  Now, nickel generally has poor wettability to solder. Therefore, when nickel is added to copper having high wettability with respect to solder, it becomes more difficult to get wet as the amount of addition increases, and the solder repels. Here, FIG. 1 schematically shows the solder wettability of the copper alloy 10 based on the relationship with the contact angle (θ) when the copper alloy 10 is immersed in the molten solder bath 11. When soldering a copper alloy, as shown in FIGS. 1A and 1B, the contact angle with respect to the molten solder bath needs to be 90 degrees or less (θ ≦ 90 degrees). If the material has a stable contact angle of less than 90 degrees regardless of the high temperature or high humidity environment that is exposed to the soldering operation after shipment, the quality control of the soldering operation is facilitated. Bonding reliability is improved.

  In FIG. 1B, the contact angle (θ) of the copper alloy 10 with respect to the molten solder bath 11 is 90 degrees (θ = 90 degrees). In this case, compared to the case where θ <90 degrees. Is slightly inferior, but the solder wettability is good. On the other hand, FIG. 1C shows a contact angle (θ) of the copper alloy 10 with respect to the molten solder bath 11 exceeding 90 degrees (θ> 90 degrees). In this case, the solder wettability is poor. It is judged that there is.

  As described above, with a copper alloy containing nickel at a predetermined ratio, for example, although the appearance color does not change even when heated in the atmosphere at a temperature of 150 ° C. or higher for 10 minutes, the surface is oxidized and the solder wettability is improved. It drops significantly. Therefore, the copper alloy for solder bonding according to the present embodiment is characterized in that silver is added at a predetermined ratio.

  Specifically, the copper alloy for solder bonding according to the present embodiment contains silver in a proportion of 1% by mass or more and 20% by mass or less. In this solder-bonding copper alloy, solder wettability can be improved by containing silver in a proportion of 1% by mass or more and 20% by mass or less. Further, such addition of silver contributes to further improving the effect of improving the solder wettability by the flux in the soldering operation.

  With regard to the silver content, if the silver content in the copper alloy is less than 1% by mass, the effect of improving the solder wettability cannot be obtained. On the other hand, even if the silver content exceeds 20% by mass, the effect of improving the solder wettability is saturated and does not change, but the cost increases and becomes inefficient.

  Moreover, as content of silver, it is more preferable that they are 2 mass% or more and 10 mass% or less. When the silver content is in such a range, as described later, even when a small amount of an element such as tin (Sn) is mixed, the high solder wettability can be reliably maintained. This makes it possible to perform solder bonding with higher reliability.

  Thus, the copper alloy for solder joints according to the present embodiment is composed mainly of copper, and nickel is contained in a proportion of 10% by mass to 35% by mass and silver is contained in a proportion of 1% by mass to 20% by mass. Being done. According to this copper alloy for solder joining, it has a good appearance ranging from bright and light copper color with metallic luster to silver white, and no discoloration is observed even when heated to about 150 ° C. Therefore, plating with noble metal or the like can be omitted even when the appearance is important and the appearance is regarded as important. More preferably, by adding nickel in a proportion of 16% by mass or more and silver in a proportion of 2% by mass or more, the appearance color becomes a silver white system, so that the appearance can be further improved.

  In addition, the copper alloy for solder joint according to the present embodiment shows excellent solder wettability close to that of pure copper in the subsequent solder joint even after being oxidized at about 150 ° C., for example. Specifically, this copper alloy for solder bonding uses JIS C 60068-2-54 (IEC 60068-) using a solder bath of Sn-3.5 mass Ag-0.5 mass% Cu that melts at 245 ° C. 2-54) The contact angle (θ) between the copper alloy in contact with the thermal equilibrium state and the solder bath measured by the solderability test method (solder bath equilibrium method) in conformity with 2-54) is 90 degrees or less. . Moreover, this copper alloy for solder joining is the solder of Sn-3.5 mass Ag-0.5 mass% Cu which melts at 245 degreeC in the state heated for 10 minutes in 150 degreeC air | atmosphere. When the bath is in contact with the bath in a thermal equilibrium state, the contact angle between the copper alloy and the solder bath measured by a test method according to JIS C 60068-2-54 is 90 degrees or less.

  Note that the heating in the atmosphere at 150 ° C. approximates to the preheating conditions in the reflow soldering process, for example. Further, heating for 10 minutes under a temperature condition of 150 ° C. can be regarded as an accelerated test of oxidation treatment on the sample surface.

  According to such a copper alloy having high solder wettability, quality control in the solder joining operation becomes extremely easy, and the reliability of solder joining can be improved. Moreover, it is not necessary to apply silver, palladium, tin, or the like for soldering, and an electronic member such as a copper wiring board can be manufactured at a low cost. In addition, the high wettability with respect to the molten solder of the copper alloy for solder bonding according to the present embodiment is the above-described solder bath of Sn-3.5 mass Ag-0.5 mass% Cu that melts at 245 ° C. For example, even a solder bath having a melting temperature lower than that of the solder bath exhibits high wettability.

  Further, even when a small amount of unintentional elements other than nickel and silver unavoidable impurities are mixed during melting casting, silver is in a ratio of 1% by mass to 20% by mass, preferably 2% by mass to 10% by mass. By containing in, high solder wettability can be maintained. Specifically, for example, even if tin (Sn) is contained in a proportion of 5.0% by mass or less, high solder wettability can be maintained. This widens the range of metal raw materials that can be used, and depending on the composition, an inexpensive metal with low purity such as scrap metal can be used as a raw material.

  As described above, when Sn is contained in the copper alloy, the Sn content is preferably 5.0% by mass or less. In addition, when Sn is contained in a proportion of 5.0% by mass or less as described above, the silver content is preferably 2% by mass or more, and more preferably 2.5% by mass or more. . Thereby, even if Sn is contained, high solder wettability can be maintained more effectively.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited to a following example at all.

<Manufacture of the copper alloy of an Example and a comparative example>
In Examples and Comparative Examples, a copper alloy molten metal was prepared so as to have a component composition as shown in Table 1 below to produce a copper alloy sample. In addition, as shown in Table 1, as a component, nickel, silver, and tin are contained in a predetermined ratio, respectively.

  Specifically, using a high-frequency vacuum melting furnace, a molten copper alloy having the composition shown in Table 1 below is prepared in a vacuum, held in the vacuum for 10 minutes, and then cast into a graphite mold in an argon gas atmosphere. An ingot was produced. And the produced ingot was cut out in the strip shape of thickness 0.3mm, width 5.0mm, and length 15.0mm, it was set as the copper alloy sample, and it used for evaluation shown below.

<Evaluation>
The produced copper alloy sample was evaluated for appearance color and solder wettability.

  The appearance color is evaluated with the naked eye, and the dark orange color, which is the color of 4N purity copper heated at 150 ° C in the atmosphere, is "5", and the copper color of non-oxidized 4N purity copper is the order of darkness. “3”, silvery white like a one hundred yen coin was “1”, the middle of each was “4”, “2”, and the closest color among the five colors was judged. In addition, the appearance color was evaluated based on two stage criteria: immediately after cutting (non-heated appearance color) and after heating for 10 minutes at a temperature of 150 ° C. in the atmosphere (post-heating appearance color).

  Solder wettability was evaluated using a Solder Checker (SAT-5200) manufactured by Reska Co., Ltd. In the solder wettability test, an activated rosin flux obtained by adding dimethylammonium chloride to a solution composed of 25% rosin and 75% isopropanol was used as the flux. Moreover, as a solder bath, the molten solder bath which melt | dissolved Sn-3 mass% Ag-0.5 mass% Cu and was hold | maintained at 245 degreeC was used. The immersion rate of the copper alloy sample in the solder bath was 5 mm / s, the immersion depth was 2 mm, and the immersion time was 30 seconds.

  Here, the solder checker uses the difference between the buoyancy B acting on the copper alloy sample and the surface tension S as the wetting force F (F = SB), and observes the wetting force F over time. Accordingly, the solder wettability of the copper alloy samples was evaluated as “good” when the maximum value of the wetting force F was zero or more, and “bad” when it was less than zero.

<Result>
Table 1 below shows the appearance color evaluation results and the solder wettability evaluation results. In addition, as above-mentioned in Table 1, it shows also about the component composition of the copper alloy in each Example and a comparative example.

  As shown in the results of Table 1, in Example 1, although the appearance color was not completely silver white, no change in appearance was observed before and after heating, and the discoloration could be effectively suppressed. Further, the copper alloy of Example 1 had very good solder wettability, and showed excellent solder wettability even after heating.

  In Examples 2 to 7, the appearance color was silver white before and after heating, and the appearance change was not observed before and after heating, and the discoloration could be effectively suppressed. Moreover, the copper alloys of Examples 2 to 7 also had very good solder wettability, and showed excellent solder wettability even after heating.

  On the other hand, in Comparative Examples 1, 3, 5, and 6, although the solder wettability before and after heating was good, the appearance color was copper and discoloration after heating was easily observed. In Comparative Examples 2, 4, and 7, the appearance color was silver white and there was no change before and after heating, but it did not contain silver or was added in an extremely small amount (less than 1% by mass). Therefore, the solder wettability before and after heating or after heating was extremely poor.

  According to the copper alloy for solder joining according to the present embodiment, for example, even when heated to about 150 ° C., the change in appearance color can be effectively suppressed, and the appearance is visually good. Further, since the solder wettability before and after heating is maintained high, the soldering workability is easy, the reliability is high, and the solder bonding alloy is particularly preferable when the appearance is regarded as important. In addition, the metal price is cheaper than gold, palladium, and silver, and the utility value in the electronic component industry is extremely large.

10 Copper alloy 11 Molten solder

Claims (5)

Nickel is 35 mass% to 10 mass%, silver Ri is Na is contained in an amount of 20 wt% or less than 2 wt%, the tin content is not more than 5.0 mass%, the balance being copper and incidental copper alloy is a material to be joined in a solder joint, wherein impurities der Rukoto.   Nickel is contained in a proportion of 16% by mass to 35% by mass, silver is contained in a proportion of 1% by mass to 20% by mass, the tin content is 5.0% by mass or less, and the balance is copper and inevitable impurities. A copper alloy, which is a material to be joined by soldering, characterized in that: The copper alloy according to claim 1 or 2 , wherein nickel is added at a ratio of 16% by mass to 28% by mass and silver is added at a rate of 2% by mass to 10% by mass. Using the Sn-3.5 mass Ag-0.5 mass% Cu solder bath that melts at 245 ° C., measured in a test method according to JIS C 60068-2-54, in contact with the thermal equilibrium state copper alloy according to any one of claims 1 to 3 the contact angle between the copper alloy and the solder bath is equal to or less than 90 degrees. When the copper alloy heated in the atmosphere at 150 ° C. for 10 minutes and the Sn-3.5 mass Ag-0.5 mass% Cu solder bath melting at 245 ° C. are in thermal equilibrium, JIS C 60068 -2-54 was measured in compliance with the test method, the copper according to any one of claims 1 to 4 contact angle with the copper alloy and the solder bath is equal to or less than 90 degrees alloy.

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