JP2009007625A - Method for producing high strength copper alloy for electric/electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high strength copper alloy for electric/electronic components by which a dimensional change upon heating can be reduced without impairing its fundamental properties such as strength, electric conductivity and heat resistance. <P>SOLUTION: In the method for producing a high strength copper alloy for electric/electronic components, a copper base alloy containing, by mass, 1.0 to 4.0% Ni and 0.2 to 1.2% Si, and the balance Cu with inevitable impurities is cast, is rolled by hot rolling, is thereafter subjected to cold rolling at a working ratio of ≥15%, is subjected to aging treatment at 300 to 500°C for 30 min to 24 hr, is subsequently subjected to final cold rolling, and is further subjected to stress relieving annealing at 300 to 550°C for 30 s to 3 min, wherein the hardening rate of its hardness after the final cold rolling to its hardness after the aging treatment is controlled to ≤10%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a copper alloy for electrical / electronic parts that has good strength and electrical conductivity and has a small dimensional change during heating.

Copper alloys for electrical and electronic parts such as lead frames and connectors are required to have high strength and high thermal conductivity, as well as high heat resistance that is not easily softened by heating during the manufacturing process of electrical and electronic parts. In recent years, with the progress of miniaturization and high integration of electrical and electronic components, the requirements for the above characteristics have become more severe. As an alloy that satisfies these requirements, Cu-Ni-Si alloy (Corson alloy) is used. It has been developed and used with various additive elements added. Many patents relating to Cu-Ni-Si alloys have been published by various companies so far. For example, patent No. 2572204 from Olin is a typical example of a patent that mentions components and manufacturing methods in order to improve strength and electrical conductivity. Patents referring to bending workability and plating property include, for example, Japanese Patent No. 3383615, Japanese Patent Laid-Open No. 58-123846, and Japanese Patent Laid-Open No. 10-110228 by Furukawa Electric. Patents referring to wire bonding properties include, for example, Nikko Metal Patent No. 2714560 and Japanese Patent Publication No. Sho 62-46071. Patents referring to pressability include, for example, Nikko Mineral Patent No. 3619516 and JP-A-10-30155.
Japanese Patent No. 2572042 Japanese Patent No. 3383615 Japanese Patent Laid-Open No. 58-123846 Japanese Patent Laid-Open No. 10-110228 Japanese Patent No. 2714560 Japanese Examined Patent Publication No. 62-46071 Japanese Patent No. 3619516 Japanese Patent Laid-Open No. 10-30155

  The lead frame is obtained by pressing or etching a copper strip to obtain a predetermined shape. However, as the lead frame is narrowed by a multi-pin narrow pitch, the requirement for dimensional accuracy has become very strict. In the case of manufacturing by pressing, annealing at about 500 ° C. is performed after pressing to remove press distortion. For this reason, the copper strip for lead frames is strongly required to have a high heat resistance and a small dimensional change upon heating.

  As described above, there are many patents regarding secondary characteristics of Cu—Ni—Si based alloys. However, there are no patents referring to dimensional changes during heating. With regard to dimensional changes due to heating in other copper alloys, it is known that Cu-Be alloys cause significant dimensional changes during the aging heat treatment process, and many research papers are found. For example, a series of researches including Miki et al. “Effect of cold working on dimensional change (shrinkage and expansion) with aging of Cu—Be alloy” (copper and copper alloy, 38 (1999), 139.). A paper is mentioned. However, in the Cu—Ni—Si based alloy, there is no literature as to whether a significant dimensional change is observed as in the aging heat treatment of the Cu—Be alloy. When manufacturing a lead frame, manufacturing conditions are set in consideration of a dimensional change during heating, and the lead frame copper alloy strip is required to have a small variation in dimensional change. Accordingly, efforts have been made to stabilize the dimensional change during heating of the copper alloy strip for lead frames by stabilizing the manufacturing conditions, but it cannot be said that a measure for reducing the dimensional change has been taken sufficiently.

  Accordingly, an object of the present invention is to provide a manufacturing method capable of reducing a dimensional change during heating without impairing basic characteristics such as strength, conductivity, and heat resistance.

  In order to achieve the above object, the effects of aging treatment conditions and rolling conditions of Cu—Ni—Si based alloys on dimensional changes during heating of the final product were investigated. As a result, it was found that the curing rate in the final rolling greatly affects the dimensional change due to heating, and the greater the amount of work hardening by the final rolling, the longer the heating in the rolling direction. Therefore, in order to reduce the dimensional change during heating without impairing the basic properties such as the original strength, conductivity, and heat resistance, the aging treatment conditions and the final rolling process rate should be optimized, and the strain removal annealing should be optimized. Found that is necessary.

  The present invention has been obtained on the basis of the above knowledge, and contains 1.0 mass% to 4.0 mass% of Ni, 0.2 mass% to 1.2 mass% of Si, or these In addition to P, Zn, Sn, Mg, Fe, Co, Mn, Zr, Ti, Cr, and Ag as a subsidiary component, the total amount is less than 2.0% by mass, and the balance is inevitable with Cu. After casting a copper-based alloy made of impurities and rolling it to a desired thickness by hot rolling or the like, it is cold-rolled at a processing rate of at least 15% and at a temperature of 300 ° C. to 500 ° C. for 30 minutes to 24 hours In the method for producing a copper alloy strip, which is subjected to the following aging treatment, followed by final cold rolling, and further subjected to strain removal annealing at a temperature of 300 ° C. to 550 ° C. for 30 seconds to 3 minutes, Of hardness after final cold rolling to thickness Dimensional change during heating, characterized in that the elongation in the rolling direction during heating for 1 minute to 10 minutes at a temperature of 400 ° C. to 550 ° C. is 50 ppm or less by making the rate 10% or less The present invention relates to a method for producing a high-strength copper alloy for electrical / electronic parts having a small size and capable of reducing dimensional changes during heating without impairing basic properties such as strength, conductivity, and heat resistance.

  The present invention has developed a manufacturing method that can reduce the dimensional change during heating without impairing the basic characteristics of Cu-Ni-Si alloys such as strength, conductivity, and heat resistance. The effect is very large in that the problem of the dimensional change during the press strain removal annealing is solved.

  A method for producing a copper alloy for electric / electronic parts having good strength and conductivity according to the present invention and having a small dimensional change during heating will be described in detail below.

(1) Alloy component The alloy component includes Ni of 1.0 mass% to 4.0 mass% and Si of 0.2 mass% to 1.2 mass%. While obtaining high strength by precipitating Ni 2 _Si which is an intermetallic compound in the Cu by aging treatment in this alloy, Ni is less than 1.0 wt%, or Si is a sufficient strength is less than 0.2 wt% Can't get. On the other hand, when Ni exceeds 4.0% by mass or Si exceeds 1.2% by mass, the decrease in conductivity and the deterioration of workability become remarkable. In particular, the intermediate temperature brittleness becomes remarkable and intergranular cracking at the time of high temperature heating or hot working is very likely to occur. In addition, the amount of precipitation of Ni ₂ Si and the like increases, and these become residues on the surface during pickling to induce plating defects. Further, when Ni exceeds 4.0% by mass, the amount of H absorbed in the molten metal at the time of melting increases, and remains as solute hydrogen in the ingot. These hydrogens contribute to brittleness at the intermediate temperature and are liable to become blistered defects during annealing after cold rolling. Desirably, Ni is 1.5 mass% or more and 3.0 mass% or less, and Si is 0.3 mass% or more and 0.7 mass% or less. The mixing ratio of Ni and Si should be Ni: Si = 4: 1 because it is considered possible to improve the strength and conductivity more efficiently when the composition is closer to the composition of Ni ₂ Si, which is an intermetallic compound. Is desirable.

  The alloy component is basically the above-mentioned component, but as a subsidiary component, any one or more of P, Zn, Sn, Mg, Fe, Co, Mn, Zr, Ti, Cr, and Ag are added in a total amount of 2. Even if the content is less than 0% by mass, the effects of the present invention can be obtained in the same manner.

  P has an effect of slightly improving the strength as well as an effect as a deoxidizer during dissolution.

  Zn improves solder wettability and has an effect of suppressing growth of an alloy layer of Cu and Sn generated at the interface with the solder layer. In addition, it has a degassing action at the time of dissolution and a Cu migration suppressing action. Even if added in a relatively large amount, there is little adverse effect on the properties, but addition of 2.0% by mass or more brings about a decrease in conductivity and saturation of the effect.

  Sn dissolves in Cu and has the effect of improving heat resistance, spring properties, bending workability, and stress relaxation resistance, and it is desirable to add Sn when used as a connector. Increasing the amount causes a decrease in conductivity, promotes the growth of an alloy layer of Cu and Sn formed at the interface with the solder layer, and tends to generate whiskers.

  Mg has the effect of improving the stress relaxation resistance as well as the strength and heat resistance without significantly reducing the electrical conductivity. Further, S is an element that promotes brittleness at intermediate temperature, but Mg has an effect of generating a compound with S to fix S at the grain boundary and improving hot workability. Addition of 0.5% by mass or more results in deterioration of castability such as oxide entrainment.

  Fe mainly dissolves at high temperatures, and has the effect of delaying recrystallization during high-temperature heat treatment and suppressing crystal grain growth. Addition of 0.1% by mass or more greatly reduces the conductivity and saturates the effect.

  Co also has an action of delaying recrystallization during high-temperature heat treatment and suppressing crystal grain growth. Moreover, there is little decrease in electrical conductivity compared to Fe.

  Mn also produces a compound with S to fix S at the grain boundary and improve the hot workability, but lowers the conductivity.

  Zr, Ti, and Cr have the effect of improving strength and heat resistance, but lower castability such as oxide entrainment.

  Ag has the effect of improving heat resistance.

(2) Manufacturing method After a predetermined component is melted in an electric furnace such as a crucible melting furnace or a channel melting furnace, a rectangular cross-section ingot having a thickness of 150 mm to 250 mm and a width of 400 mm to 1000 mm is obtained by continuous casting (cake) ). The cake is held at a temperature of 800 ° C. or more and 950 ° C. or less for 30 minutes or more, and then rolled to a thickness of 10 mm or more and 15 mm or less by a hot rolling mill. When the heating temperature of hot rolling is lower than 800 ° C., cracks occur at the grain boundaries during hot rolling. Further, coarse precipitates precipitated during the cooling process of casting are not sufficiently dissolved. On the other hand, when the temperature is higher than 950 ° C., the recrystallized crystal is easily coarsened and the oxide film becomes thick. Therefore, the heating temperature of hot rolling is set to 800 ° C. or more and 950 ° C. or less. Further, even if the holding time is shorter than 30 minutes, the precipitate is not sufficiently dissolved, so that the holding time is 30 minutes or more. Furthermore, it is desirable that the hot rolling end temperature is 650 ° C. or higher, and water cooling is performed at a cooling rate of 300 ° C. or more per minute. By increasing the hot rolling end temperature and increasing the subsequent cooling rate, high strength can be obtained during the aging treatment. Further, the ingot may be cast into a thin plate having a thickness of about 20 mm. In this case, hot rolling is not necessary.

  The oxide film is removed by chamfering after hot rolling. Then, after cold rolling at a processing rate of at least 15% or more, an aging treatment is performed. If the cold rolling ratio before the aging treatment is less than 15%, the precipitation sites are insufficient, the precipitation rate becomes slow and the strength is hardly increased. Desirably, it is 50% or more and 80% or less. When higher strength is required, after cold rolling to a predetermined thickness, heat at a temperature of 750 ° C or higher for 1 minute or more and less than 5 minutes, and then cool with water at a cooling rate of 200 ° C or more per minute. Apply solution treatment. Then, after cold rolling at a processing rate of at least 15% or more, an aging treatment is performed.

  The aging treatment is maintained for 30 minutes to 24 hours at a temperature of 350 ° C. to 500 ° C. When the aging temperature is less than 350 ° C., the deposition rate is slow, and even when heated for 24 hours or more, it does not precipitate sufficiently. If the aging treatment temperature exceeds 500 ° C., fine precipitates cannot be obtained and sufficient age hardening cannot be obtained. In this case, when trying to finally obtain a high strength, it is possible to increase the processing rate in rolling after aging treatment and improve the strength by processing strengthening, but the elongation rate in the rolling direction when heated is increased. growing. Desirably, it is 1 hour or more and 4 hours or less at the temperature of 420 degreeC or more and 480 degrees C or less.

  Although the final cold rolling is performed after the aging treatment, the hardening rate of the hardness after the final cold rolling with respect to the hardness after the aging treatment is set to 10% or less. If it exceeds 10%, the amount of work strain added by cold rolling increases, and the elongation in the rolling direction when heated is increased. The aging treatment may be performed twice or more with the cold rolling interposed therebetween. In this case, the hardening rate of the hardness after the final cold rolling relative to the hardness after the final aging treatment is set to 10% or less. Further, multiple annealing may be applied during the final cold rolling, but in this case, the hardness after the final cold rolling for the lowest hardness among the hardness after each annealing and the hardness after aging. The condition is that the rate is 10% or less.

  After final cold rolling, strain relief annealing is performed. The strain removal annealing is held at a temperature of 300 ° C. or more and 550 ° C. or less for 30 seconds or more and 3 minutes or less. If the temperature is less than 300 ° C. or the holding time is less than 1 minute, the processing strain cannot be sufficiently removed, the elongation is insufficient, and the elongation in the rolling direction when heated is increased. When temperature exceeds 550 degreeC, the fall of electrical conductivity and intensity | strength will become large.

  First, as shown in Table 1, after changing the components, hot rolling conditions, solution conditions, pre-aging processing rate, aging conditions and preparing several types of copper alloys, melting each component copper alloy in a high-frequency melting furnace, An ingot having a thickness of 20 mm was cast by casting in a SUS mold. Next, hot rolling was performed under each hot rolling condition to finish to a thickness of 8 mm, and after removing the oxide scale, cold rolling was performed. No. of the present invention. Only 4 was subjected to a solution treatment at a thickness of 2.5 mm, and then cold-rolled to a thickness of 1 mm. Then, cold rolling is performed at each pre-aging rate, aging treatment is performed for 2 hours at a temperature of 470 ° C., then final rolling is performed at a processing rate of 50%, and strain is removed at a temperature of 450 ° C. for 1 minute. Annealing was performed.

  Table 2 shows the results of evaluating the hot workability, electrical conductivity after strain-removal annealing, tensile strength, and plating properties of these samples. No. In all of Nos. 1 to 4, the hot workability and plating properties were good, and no problem was found in the characteristics. The higher the Ni and Si contents, the higher the strength. On the other hand, no. No. 5 has a low content of Ni and Si, and sufficient strength cannot be obtained. No. 6 had a large content of Ni and Si, and cracks occurred at the grain boundaries during hot rolling, and a large amount of residue was generated by pickling before plating. No. 7 to 9 have chemical compositions No. No. 2 but no. In No. 7, the heating temperature of the hot rolling was low, and minute cracks were generated at the grain boundaries. At the heating temperature of 860 ° C., almost no precipitates were observed inside and outside the crystal grains, but at 770 ° C., many precipitates were observed. Moreover, many non-recrystallized grains were seen in the cross section after hot rolling. No. In No. 8, the heating temperature of hot rolling was high, and the recrystallized grains became coarse. No. No. 9 had a low processing rate before aging treatment, and the precipitation did not proceed sufficiently, resulting in low conductivity and low strength.

  Next, based on the results of Table 2, After cold-rolling to a thickness of 1 mm under the same production conditions as 2 (Example 1), as shown in Table 3, changing the aging conditions, the final rolling process rate, the strain-removal annealing conditions, and producing several samples, Vickers hardness after aging and final rolling, electrical conductivity after strain removal annealing, and tensile strength were evaluated. Furthermore, heating was performed at a temperature of 500 ° C. for 5 minutes, and the dimensional change in the rolling direction before and after the heating was measured to calculate the expansion / contraction rate (elongation rate). At this time, the sample had a length of 250 mm and a width of 10 mm, and was heated in a no-tension state in an Ar atmosphere. The distance between gauge points for dimension measurement was 200 mm. In Example 1 and Examples 2 to 4 which are the present invention, the curing rate in final rolling ((hardness after final rolling / hardness after aging treatment-1) × 100) is 10% or less. Yes, the heat expansion / contraction rate is 50 ppm or less. The electrical conductivity and tensile strength after strain removal annealing are also good. On the other hand, Comparative Examples 1 to 3 have a low hardness after aging, and the curing rate exceeds 20%. As a result, the heat expansion / contraction rate greatly exceeds 50 ppm. Comparative Example 4 has the same aging conditions as Comparative Example 3, but the final rolling process rate was increased to increase the strength by work hardening. A high value of 250 ppm or more was obtained. Moreover, since it is an overaging condition, heat resistance is low, and the strength reduction by distortion removal annealing is large. Comparative Example 5 is the same manufacturing process as Example 1 up to the final rolling, and heating was performed for 1 minute at a temperature of 600 ° C. only for the strain-removal annealing conditions, but the strength was greatly reduced.

Claims (3)

  Cast a copper-based alloy containing Ni from 1.0% by mass to 4.0% by mass, Si from 0.2% by mass to 1.2% by mass, the balance being Cu and inevitable impurities, and hot rolling After rolling, cold rolling is performed at a processing rate of 15% or more, aging treatment is performed for 30 minutes to 24 hours at a temperature of 300 ° C. to 500 ° C., and then final cold rolling is performed, and further 300 ° C. or more is performed. In a copper alloy manufacturing method that performs strain relief annealing at a temperature of 550 ° C. or lower for 30 seconds or longer and 3 minutes or shorter, the hardening rate of the hardness after the final cold rolling relative to the hardness after the aging treatment should be 10% or less. A method for producing a high-strength copper alloy for electric and electronic parts.   In Claim 1, the said copper base alloy contains 1.0 mass% or more and 4.0 mass% or less of Ni, 0.2 mass% or more and 1.2 mass% or less of Si, Furthermore, P, Zn, Sn, An electrical / electronic component characterized by containing at least one of Mg, Fe, Co, Mn, Zr, Ti, Cr, and Ag in a total amount of less than 2.0 mass%, with the balance being Cu and inevitable impurities For producing high-strength copper alloys for industrial use.   The said hot rolling is a manufacturing method of the high strength copper alloy for electrical / electronic components in any one of Claim 1 or 2 which is rolled after hold | maintaining for 30 minutes or more at the temperature of 800 degreeC or more and 950 degrees C or less.