JP2009293091A - Method for producing copper alloy for electrical or electronic parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a copper alloy for electrical or electronic parts which can obtain satisfactory plating quality without strengthening pre-plating treatment and without damaging required characteristics to the material. <P>SOLUTION: Regarding a copper sheet or a copper alloy sheet rolled into a prescribed thickness through the stages of dissolution, casting, hot rolling, cold rolling, annealing or the like of pure copper or copper alloy, working strain is applied only to the vicinity of the surface layer of the material, thereafter, annealing is performed in an inert gas or reducing gas atmosphere, and subsequently, only the vicinity of the surface layer to which the working strain has been applied is subjected to the recovery of the rolled structure or is recrystallized. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a copper alloy for electrical and electronic parts having good strength and conductivity and excellent plating quality.

  Copper and copper alloys are used as materials for electric and electronic parts because of their very high thermal conductivity. Examples of electrical / electronic components include lead frames and connectors, which are usually used after various plating is applied to a copper material. For example, for lead frames, Ag plating and underlying Cu plating are used for wire bonding, and solder plating is applied for board mounting. In recent years, a method called a pre-plated lead frame (hereinafter referred to as PPF) has come to be used, and Pd plating and Au plating are performed on Ni plating. In PPF, since the solder plating process after the resin molding process can be omitted and effective as a Pb-free measure, the application has been expanded.

  The plating quality is greatly affected by the chemical composition of the copper material and the physical and chemical state of the surface as well as the pretreatment conditions for plating.

  As a method for producing a copper alloy having excellent plating quality, for example, Patent Documents 1 to 4 can be cited. In Patent Document 2 and Patent Document 3, the number of inclusions is defined. In Patent Document 2 and Patent Document 1, the thickness of the work-affected layer on the material surface is defined.

  The work-affected layer is a layer present in the surface layer portion of a copper plate obtained by cold rolling, and the outermost layer is considered to be amorphous with disordered crystallinity. The thickness is greatly influenced by the rolling reduction, rolling conditions, and material characteristics, but it is generally said that the thickness exists within 1 μm of the surface layer.

  The work-affected layer greatly affects the plating quality, and when the work-affected layer is thick or the crystallinity is severely disturbed, the plating quality is remarkably lowered. Specifically, pin holes, peeling, and subsequent swelling due to heating.

  For this reason, conventionally, in order to remove the work-affected layer, a pretreatment such as pickling has been sufficiently performed, or annealing at a predetermined temperature for recovery and recrystallization has been employed.

JP 2007-39804 A Japanese Patent No. 3383615 Japanese Patent Laid-Open No. 58-123846 Japanese Patent Laid-Open No. 2-100355

However, if the pickling treatment is strengthened to remove the work-affected layer, the production cost increases in the mass production process. The pickling solution for copper materials is generally H ₂ SO ₄ with H ₂ O ₂ and other oxidizing agents added, but H ₂ O ₂ is difficult to control the concentration, and other oxidizing agents are also produced. It becomes a factor of cost increase. Further, if the pickling time is increased in the mass production process, it is necessary to lengthen the pickling line or reduce the line speed, which also causes an increase in manufacturing cost.

  On the other hand, in the method of recovery / recrystallization at a predetermined temperature, the strength of the entire material is lowered, and the required characteristics may not be satisfied.

  The object of the present invention is to solve the above-mentioned problems and to provide a method for producing a copper alloy for electrical and electronic parts that can obtain good plating quality without strengthening the plating pretreatment and without impairing the required properties of the material. There is to do.

  In order to achieve the above object, the present invention provides a material surface layer of a copper plate or a copper alloy plate obtained by melting pure copper or a copper alloy through a process such as melting, casting, hot rolling, cold rolling, annealing, etc. An electrical / electronic component characterized by applying a processing strain only to the vicinity and then annealing in an inert gas or reducing gas atmosphere to recover or recrystallize the rolled structure only in the vicinity of the surface layer to which the processing strain has been applied. It is a manufacturing method of the copper alloy.

  It is preferable that the means for imparting the processing strain only in the vicinity of the surface layer is by polishing a copper plate or copper alloy plate finally rolled to a predetermined thickness using a brush or abrasive grains.

  The present invention has developed a method for producing a copper alloy for electrical and electronic parts that can provide good plating quality without strengthening the plating pretreatment and without impairing the basic properties such as strength and conductivity of the copper alloy. The effect is very great. Furthermore, the effect of improving the solder wettability can be obtained in the same manner as the plating quality.

  Hereinafter, a preferred embodiment of a method for producing a copper alloy for electrical / electronic parts with good plating quality according to the present invention will be described.

  The inventor of the present invention has determined how the work-affected layer changes depending on the polishing conditions and the subsequent annealing conditions, and further affects the plating quality for several types of copper alloys widely used as lead frame copper alloys. We conducted an extensive investigation.

  As a result, after the final rolling, it is possible to recover or recrystallize only the vicinity of the surface layer by annealing at an appropriate temperature and time in an inert gas or reducing gas atmosphere after giving processing strain only to the material surface layer vicinity. As a result, it was found that the plating quality was remarkably improved. Furthermore, as a result of scrutinizing a method for imparting a processing strain only in the vicinity of the material surface layer, it has been found that it is effective to polish the material surface in a random direction using an abrasive such as a brush or abrasive grains.

  That is, the present invention is to anneal a copper plate or copper alloy plate rolled to a predetermined thickness only in the vicinity of the material surface layer at an appropriate temperature and time in an inert gas or reducing gas atmosphere. In the method for producing a copper alloy for electric / electronic parts having excellent plating quality that recovers or recrystallizes only the vicinity of the surface layer.

  The embodiment of the present invention will be described in more detail below.

  Usually, after melting predetermined components in an electric furnace such as a crucible melting furnace or a channel melting furnace, a rectangular cross-section ingot (cake) having a thickness of about 150 to 250 mm and a width of about 400 to 1000 mm is cast by continuous casting.

  After holding the cake at a temperature of 800 to 1000 ° C. for 30 minutes or more, the cake is rolled to a thickness of about 10 to 15 mm by a hot rolling mill.

  The appropriate temperature for hot rolling varies depending on the chemical composition. In general, it is desirable to start hot rolling at a temperature at which an additive element is dissolved in a precipitation-type copper alloy, but if it is too high, the oxide scale increases.

  After hot rolling, the oxide film is removed by chamfering, and generally thereafter, cold rolling, annealing (including aging treatment), and pickling as necessary are repeated to reach final rolling. By giving the processing distortion by rolling, the material is work-hardened and the strength is increased.

  In the present invention, after the final rolling, the material surface is polished in a random direction using an abrasive such as a brush or abrasive grains.

  When the polishing direction is constant, polishing marks remain, and conversely, the plating quality deteriorates. In the case of a brush, if the count is rougher than # 2000, surface irregularities increase, and conversely the plating quality decreases. Use a fine brush of # 2000 or higher.

  In addition, when polishing with abrasive grains, alumina or diamond can be considered, but if the diameter of the abrasive grains is rougher than 1 μm, the surface irregularities increase, and conversely, the plating quality is deteriorated. Is used.

  Further, the applied normal stress is 2% or more and less than 20% of the yield stress of the material. If it is less than 2%, sufficient distortion cannot be imparted to the material surface. If it is 20% or more, polishing becomes difficult, and damage to the material is great, which also has an adverse effect. Furthermore, the relative speed of the material and the abrasive is 10 m / min or more and less than 300 m / min. When it is slower than 10 m / min, sufficient distortion cannot be imparted to the material surface. In the case of 300 m / min or more, polishing becomes difficult, and damage to the material is increased, resulting in an adverse effect.

  After imparting strain to the material surface as described above, the surface layer part is obtained by annealing at an appropriate temperature (300 to 550 ° C.) and an appropriate time (30 seconds to 2 minutes) in an inert gas atmosphere or a reducing gas atmosphere. Only recovered or recrystallized material can be obtained.

  When the atmosphere is not an inert gas atmosphere or a reducing gas atmosphere, it is necessary to sufficiently perform pickling in order to remove the oxide film on the surface before plating. Since the annealing conditions vary depending on the chemical composition of the material and the manufacturing process, it is necessary to optimize each time.

  By the manufacturing method of the present invention described above, a copper alloy strip for electric / electronic parts having excellent plating quality can be obtained.

  The thickness of the work-affected layer was evaluated by an SEM reflected electron image and EBSP, and the plating quality was evaluated by a thermal expansion test of Ag plating, a porosity evaluation test of Ni plating, and a solder wettability evaluation test by a meniscograph.

  After melting and adjusting to a composition of Cu-2.2 mass% Fe-0.03 mass% P-0.12 mass% Zn in a medium frequency induction type crucible furnace, semi-continuous casting with a copper mold, cross-sectional size 180 mm x 620 mm, length A 6000 mm rectangular ingot was cast.

  The ingot was then heated to 900 ° C., held for about 3 hours, and hot rolled to a thickness of about 12 mm in 11 passes.

  After removing the oxide scale, cold rolling, aging treatment, pickling, and cold rolling annealing were performed, and final rolling with a reduction rate of 80% was performed.

  Thereafter, processing strain was introduced under the conditions shown in Table 1.

  In Table 1, Example 1 is performed with a fine brush of count # 2000 or more at a pressing pressure of 30 MPa and a polishing rate of 30 m / min. Example 2 is alumina abrasive grains (particle size of 1 μm or less), and a pressing pressure of 30 MPa. This is performed at a polishing rate of 60 m / min.

  Comparative Example 1 was performed with a brush at a pressing pressure of 5 MPa and a polishing rate of 30 m / min, Comparative Example 2 was performed with a brush at a pressing pressure of 150 MPa and a polishing rate of 30 m / min, and Comparative Example 3 was an alumina abrasive grain. The pressing pressure was 30 MPa and the polishing rate was 5 m / min. Comparative Example 4 was alumina abrasive grains, and the pressing pressure was 30 MPa and the polishing rate was 400 m / min. Conventional Example 1 was used as it was without introducing processing strain.

  Among them, Comparative Example 2 had a high brush pressing pressure, and Comparative Example 4 had a high polishing rate, so that stable polishing could not be performed, making it impossible to produce a sample.

  Furthermore, strain removal annealing was performed at a temperature of 300 to 550 ° C. for 1 minute in an Ar atmosphere.

  FIG. 1 shows the relationship between the tensile strength and elongation of the samples of Examples 1 and 2 and Comparative Examples 1 to 4 and Conventional Example 1 with respect to the strain-removal annealing temperature, and the black squares indicate the tensile strength, A black circle mark is elongation.

  The tensile strength and elongation of the whole material overlap with each other in both the black square mark and the black circle mark, and regardless of the conditions in Table 1, Examples 1 and 2 and Comparative Examples 1 to 4 are equivalent to Conventional Example 1. I understand that.

  The required characteristics of this material are a tensile strength of 520 MPa or more and an elongation of 5% or more, and it can be seen from FIG. 1 that the annealing temperature satisfying this is 425 to 500 ° C.

  Therefore, for each sample in Table 1 (Examples 1, 2, Comparative Examples 1, 3, and Conventional Example 1), strain-relief annealing was performed at 450 ° C. and 500 ° C. for 1 minute, respectively, and the outermost surface structure and processing Table 2 shows the results of measurement of the altered layer thickness, Ag plating heating swelling, Ni plating Cu elution amount, and solder wetting time.

  The measurement of the outermost surface structure and the work-affected layer thickness is the cross-sectional structure observation of the material outermost surface using the SEM reflected electron image and EBSP and the work-affected layer thickness (defined as the portion whose orientation reliability is 10% or less in EBSP) ) Was measured.

In addition, Ag plating heating swelling test, Ni plating porosity evaluation test, and solder wettability test to investigate the effect on plating quality are as pre-treatment. Samples were subjected to alkaline electrolytic degreasing for 10 seconds → washed with running water for 10 seconds → pure Each test was carried out after rinsing → pickling for 10 seconds (2N H ₂ SO ₄ ) → washing with running water for 10 seconds → pure rinsing.

Ag plating is performed using an Ag plating bath containing AgCN: 50 g / l and KCN: 115 g / 1, with a sample effective area of 5 cm × 5 cm, a liquid temperature of 50 ° C., a current density of 5 A / cm ² , and a plating time of 100 seconds. Then, after the Ag plating, it was heated in an N ₂ atmosphere at 350 ° C. for 5 minutes, checked for the presence or absence of swelling on both surfaces with an optical microscope, and evaluated by the number of swellings.

Ni plating is performed in a sulfamic acid bath, the sample effective area is 5 cm × 5 cm, the liquid temperature is 50 ° C., the current density is 10 A / cm ² , and the plating time is 20 seconds. The Ni plating porosity evaluation test is performed in the atmosphere after Ni plating. After heating at a temperature of 450 ° C. for 5 minutes, masking was performed with a masking tape so that circular exposed portions having a diameter of 4 cm were formed on both the front and back surfaces, and this was further immersed in 1N H ₂ SO ₄ for 5 minutes to elute. The concentration of Cu was quantitatively evaluated by ICP emission spectroscopy.

  The solder wettability test was carried out by a meniscograph, and after immersing the sample in a rosin flux, the sample was immersed in 60Sn-40Pb solder heated to 220 ° C., and the time until wetting was evaluated.

  From Table 2, in Examples 1 and 2 of the present invention, the distortion of the material surface is released by annealing, and the work-affected layer becomes thin. As a result, the thermal expansion test of Ag plating, the porosity evaluation test of Ni plating, the solder wettability test In any case, good results were obtained.

  On the other hand, in Comparative Examples 1 and 3 and Conventional Example 1, the material surface strain is not released under this annealing condition, and as a result, any of the thermal expansion test of Ag plating, the porosity evaluation test of Ni plating, and the solder wettability test Good results were not obtained.

It is a figure which shows the relationship of the tensile strength and elongation with respect to the annealing temperature of the distortion removal of the sample of the Example of this invention, a comparative example, and a prior art example.

Claims (2)

  After applying a processing strain only to the vicinity of the surface layer of a copper plate or copper alloy plate that has been rolled to a predetermined thickness through steps such as melting, casting, hot rolling, cold rolling, and annealing of pure copper or copper alloy, A method for producing a copper alloy for electrical / electronic parts, comprising annealing in an active gas or reducing gas atmosphere and recovering or recrystallizing a rolled structure only in the vicinity of a surface layer subjected to processing strain.   The copper alloy for electric / electronic parts according to claim 1, wherein the means for imparting a processing strain only in the vicinity of the surface layer is obtained by polishing a copper plate or copper alloy plate finally rolled to a predetermined thickness using a brush or abrasive grains. Method.

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