KR100679913B1 - ??-??-??-?? based copper alloy strip and parts for the electronic goods obtained by manufacturing the same - Google Patents

Abstract

(Problem) Provided is a Cu-Ni-Si-Mg alloy in which good solder wettability, plating property and bendability can be obtained stably.

(Measures) 1.0-4.5 mass% of Ni is contained, 1 / 6-1 / 4 Si is contained with respect to the mass% of Ni, 0.05-0.3 mass% Mg is contained, and remainder is Cu and inevitable. Cu-Ni-Si- having a number of inclusion groups having a length of 0.05 mm or more in the inclusion group composed of Mg oxide particles observed in a cross section perpendicular to the rolling direction as a copper base alloy composed of red impurities. Mg based copper alloy strips.

Description

Cu-Ni-Si-Mg-based copper alloy strip and components for electronic devices obtained by processing it {Cu-Ni-Si-Mg BASED COPPER ALLOY STRIP AND PARTS FOR THE ELECTRONIC GOODS OBTAINED BY MANUFACTURING THE SAME}

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the form of an inclusion in a Cu-Ni-Si-Mg type copper alloy strip.

FIG. 2 is a schematic diagram of Mg-O particle distribution in a right angled cross section of a Cu—Ni—Si—Mg based copper alloy strip. FIG.

The present invention has high strength, conductivity, stress relaxation resistance, bending workability, etching property and plating property, which are preferable as conductive spring materials for lead frame materials, connectors, terminals, relays, switches, etc. of semiconductor devices of integrated circuits (IC). It relates to a copper alloy strip.

Copper alloys for electronic materials used in lead frames, terminals, connectors, and the like are required to have high strength, high electrical conductivity, or thermal conductivity at the same time as the basic characteristics of the alloy. In addition to these properties, bending workability, stress relaxation resistance, heat resistance, plating adhesion, solder wettability, etching processability, press punching resistance, corrosion resistance, and the like are required.

On the other hand, in response to the recent miniaturization and high integration of electronic components, in lead frames, terminals, and connectors, an increase in the number of leads and a narrowing of pitches are progressing, and component shapes are also complicated. At the same time, the demand for improved reliability at the time of assembly and after mounting is increasing. Against this background, the demand level for the characteristics of the above-described copper alloy material is becoming more and more advanced.

In view of high strength and high conductivity, in recent years, as the copper alloy for electronic materials, the amount of the age hardening copper alloy is increasing instead of the solid solution hardening copper alloy represented by conventional phosphor bronze, brass and the like. In the age hardening type copper alloy, by aging the solution-treated supersaturated solid solution, fine precipitates are uniformly dispersed, the strength of the alloy is increased, and the amount of solid solution in copper is reduced to improve electrical conductivity. For this reason, the material which is excellent in mechanical properties, such as strength and a spring property, and is excellent in electrical conductivity and thermal conductivity is obtained.

Among the age hardening copper alloys, Cu-Ni-Si alloys are representative copper alloys having both high strength and high electrical conductivity, and have been put into practical use as materials for electronic devices. In this copper alloy, fine Ni-Si-based intermetallic compound particles are precipitated in the copper matrix to increase strength and electrical conductivity.

In order to improve mechanical properties and the like, Cu-Ni-Si alloys are often added with elements other than Ni and Si. In particular, Mg is a representative element added to the Cu-Ni-Si alloy. As an effect of the addition of Mg,

(1) strength and stress relaxation resistance are improved (for example, Japanese Patent Laid-Open No. 61-250134);

(2) hot workability is improved (for example, JP-A-5-345941);

(3) When Mg becomes an oxide and traps oxygen, generation or coarsening of Si oxide during heat treatment can be prevented (for example, JP-A-9-209062), and the like. Reported.

According to another conventional technique (for example, JP-A-5-59468), when Mg is added to Cu-Ni-Si, the O and S concentrations must be reduced to 15 ppm or less. When S or O exceeds 15 ppm, Mg becomes an oxide, a stress relaxation characteristic and plating heat peelability deteriorate, and when a plated product is heated, defects, such as a bleeding and plating expansion, arise. That is, when Mg is oxidized or sulfided, not only does the effect of Mg addition occur, but also adversely affects properties.

In the general manufacturing process of Cu-Ni-Si-Mg alloy, first, raw materials, such as electric copper, Ni, Si, Mg, are melt | dissolved under charcoal coating using an atmospheric melting furnace, and the molten metal of a desired composition is obtained. And this molten metal is cast in a mold. Thereafter, hot rolling, cold rolling and heat treatment are performed to finish with a strip or foil having a desired thickness and properties.

Here, in order to reduce S concentration, what is necessary is just to regulate the S density | concentration of a dissolution raw material and a coating charcoal. In addition, in order to reduce the O concentration, it is important not only to use a raw material having a low O concentration, but also to strengthen the charcoal coating to prevent oxidation of the dissolution.

In addition, although the invention which focused on the inclusion of Cu-Ni-Si type alloy has been reported in the past, the invention which prescribed | regulated the frequency of coarse Ni-Si particle | grains (for example, Unexamined-Japanese-Patent No. 2001-49369), or As an invention in which Si oxide particles are defined (for example, Japanese Patent Application Laid-open No. Hei 9-209062), no attempt has been made to focus on Mg-O inclusions and attempt to improve the properties of a Cu-Ni-Si-Mg alloy.

The inventors have accumulated and examined the characteristic data of industrially produced Cu-Ni-Si-Mg alloys, and found that solder wettability between materials of the prior art in which O and S concentrations were adjusted to a sufficiently low level of 10 ppm or less. It has been found that there are subtle differences in the properties such as plating, bending and workability. This difference was not a problem in the conventional required characteristic level for lead frame, terminal, and connector. However, with the recent miniaturization of electronic components, the level of required characteristics for lead frames, terminals, and connectors has increased. Therefore, there is a need to make the characteristics as small as possible and to stably produce excellent characteristics as possible.

An object of the present invention is to provide a Cu-Ni-Si-Mg copper alloy strip in which good solder wettability, plating property, and bending workability can be stably obtained.

(Means to solve the task)

The present invention contains 1.0 to 4.5% by mass of Ni,

It contains 1 / 6-1 / 4 Si with respect to the mass% of Ni,

It contains 0.05-0.3 mass% Mg,

The balance is a copper base alloy composed of Cu and unavoidable impurities,

It is related with the Cu-Ni-Si-Mg type copper alloy strip whose number of inclusion groups which are 0.05 mm or more in length is 1 / mm <2> of the inclusion group comprised by the Mg oxide particle observed in the cross section orthogonal to a rolling direction.

The said copper alloy strip may contain 0.01-2.0 mass% in total amount of at least 1 sort (s) chosen from the group of Sn, P, Fe, Co, Mo, Mn, Zn, and Ag.

The present invention also relates to an electronic device component obtained by processing the copper alloy strip. The electronic device components include conductive spring materials such as lead frame materials, connectors, terminals, relays, and switches of semiconductor devices.

(The best mode for carrying out the invention)

The present inventors have investigated the metal structure of Cu-Ni-Si-Mg alloy having reduced O and S concentrations to 10 ppm or less in detail, and the material having poor properties such as solder wettability, plating property, bending workability, etc. is composed of particles of Mg oxide. It has been found to contain a significant frequency of inclusions.

1 shows the form of this inclusion. When the cross section perpendicular to the rolling direction of the alloy strip is observed, the inclusions are usually observed as a group of Mg oxide (Mg-O) particles paralleled in the direction orthogonal to the thickness direction. The diameter of each Mg-O particle is about 0.1-1 micrometer normally. Hereinafter, the aggregate of Mg-O particle | grains whose distance (d) with adjacent Mg-O particle | grains is within 5 micrometers is called Mg-O inclusion group.

In the ingot after casting, the Mg-O inclusion group is a spherical cluster in which Mg-O particles are collected, which is changed into a distribution form as shown in FIG. 1 by rolling.

Mg-O inclusion groups are at random probability of appearing on the material surface. If the Mg-O inclusion group is present inside the plate, the detriment to its properties is small. However, when the group of Mg-O inclusions is exposed on the surface, problems such as the following (i) to (i) occur.

(Iii) When soldering, solder splatters on the Mg-O inclusion group.

(Ii) When the rolled surface is chemically corroded as in the half etching process, the Mg-O inclusion group melts and remains, and the smoothness of the etching surface is lost.

(Iii) When plating of Ag, Ni or the like is performed, plating pinholes are formed on the Mg-O inclusion group. Alternatively, sufficient plating adhesion strength cannot be obtained on the Mg-O inclusion group, and peeling of the plating and plating expansion occur at this portion.

(Iv) When the Mg-O inclusion group is present near the surface layer of the bend at the time of bending, roughness or cracking of the surface occurs at this portion.

(Iii) At the time of cold rolling, the scratch which causes the presence of Mg-O inclusion group arises, and damages the surface appearance.

With the progress of miniaturization of electronic components, the above problems cannot be ignored, and it is necessary to reduce the group of Mg-O inclusions to a level where problems do not occur.

Next, the present inventors studied the method of reducing the Mg-O inclusion group. Mg has a very strong deoxidizing force even when compared with Si. When Mg is added to the Cu-Ni-Si alloy, the oxygen concentration of the molten metal decreases and Mg-O particles which are deoxidation products are generated. Even if the molten metal is strictly covered with charcoal, it is difficult to completely prevent the production of Mg-O particles. Mg-O particles generated in the molten metal gather together to form clusters and float in the molten metal. And Mg-O which reached the molten surface is absorbed by the slag layer (oxide layer) of the surface. Therefore, when the molten metal after Mg addition is made to stand for a suitable time, Mg-O inclusions in a molten metal will reduce.

As described above, in order to reduce the group of Mg-O inclusions, the charcoal coating is strengthened to suppress the oxidation of Mg as much as possible, the surface of the molten metal is coated with a molten flux such as borax to absorb Mg-O, and the molten metal is further melted. It is effective to carry out flotation treatment (politics) of Mg-O after adding Mg to it.

(1) Ni and Si

Ni of the alloy of the present invention is in the range of 1.0 to 4.5 mass%. If Ni is less than 1.0, sufficient strength cannot be obtained. When Ni exceeds 4.5 mass%, a crack will generate | occur | produce in hot rolling. Ni and Si perform the aging treatment to form fine particles of an intermetallic compound mainly containing Ni ₂ Si. As a result, the strength of the alloy is significantly increased, and at the same time, the electrical conductivity is also increased. The addition concentration (mass%) of Si of the alloy of the present invention is in the range of 1/6 to 1/4 of the addition concentration (mass%) of Ni. If the amount of Si added is out of this range, the electrical conductivity is lowered.

(2) Mg

In the addition of less than 0.05% by mass of Mg to the Cu-Ni-Si alloy, no increase in tensile strength and strength or improvement in heat resistance and stress relaxation characteristics are observed, while charcoal coating is applied when the amount of Mg added exceeds 0.3% by mass. Even when the melt flux coating and the Mg-O flotation treatment are performed, the group of Mg-O inclusions in the alloy increases, and solder wettability, plating property, bendability, and the like deteriorate.

(3) Mg-O inclusion group

The distribution of Mg-O particle | grains observed in the rolling right angle cross section is shown in FIG. The diameter of Mg-O particle is about 0.1-1 micrometer. Mg-O particles having a diameter of more than 1 µm are detrimental to properties even if they are dispersed alone without forming an aggregate. However, Mg-O particles larger than 1 mu m are not observed in ordinary Cu-Ni-Si-Mg copper alloy strips produced industrially in the prior art. On the other hand, for Mg-O particles having a particle diameter of less than 0.1 µm, since the adverse effects on the properties are small, the presence thereof may be ignored. Here, when a particle is elliptical, the average of long diameter and short diameter is made into a diameter.

The "Mg-O inclusion group" of the present invention refers to an aggregate of Mg-O particles having a distance (d) to adjacent Mg-O particles within 5 µm. If the Mg-O particles are dispersed at intervals exceeding 5 µm, the individual particles are minute, and thus adverse effects on the characteristics can be ignored. However, when the Mg-O particles are aggregated at a distance of 5 µm or less, the characteristics adversely affect the inclusion groups.

The larger the inclusion group having a larger length L of the inclusion group and the larger the number of inclusion groups, the greater the adverse effect on the alloy characteristics. According to the experimental results of the present inventors, the inclusion group having a length (L) of 0.05 mm or more is harmful, and when this existence frequency exceeds 1 / mm 2, solder wettability, plating property, bendability, and the like deteriorate. The number of inclusions whose length is 0.05 mm or more in the copper alloy strip of this invention is 1 piece / mm <2> or less. In addition, the length L of an inclusion group is defined as the length of the direction orthogonal to the thickness direction in the cross section perpendicular | vertical to a rolling direction.

Since Mg is very easy to oxidize, it is impossible to industrially produce a material containing no Mg-O particles at all, but by adjusting the distribution as described above, there is no harm to properties.

(4) Additional elements other than Mg

For the purpose of improving characteristics such as strength, Cu, an element that is more easily oxidized (stronger deoxidizing power) than Mg such as Ca or Be, or an element having the same level of deoxidizing power as Mg such as Ti, Zr, Al, etc. When added to the -Ni-Si-Mg alloy, the Mg-O particles are reduced to the metal Mg to form oxide particles of the additional element. As a result, the detriment to the properties of the Mg-O particles is reduced, while the detriment to the oxide particles of the additive element occurs, and the effect of the present invention cannot be obtained.

On the other hand, when elements that are less oxidized than Mg such as Sn, P, Fe, Co, Mo, Mn, Zn, and Ag are added, the frequency of the Mg-O inclusion group is regulated as in the case of not containing these elements. The characteristic improvement effect by doing is obtained.

These elements are added to the Cu-Ni-Si-Mg alloy for the purpose of improving the strength, plating heat peeling resistance and the like. However, since electrical conductivity falls, it is preferable to make the addition amount into 2.0 mass% or less in total. On the other hand, when the addition amount of these elements is less than 0.01 mass%, the effect by addition is not expressed.

(Example)

Using a high frequency induction furnace, 10 kg of electric copper was dissolved in a graphite crucible having an inner diameter of 100 mm, and the temperature of the molten copper was adjusted to 1200 ° C. Next, 2.5 mass% Ni and 0.5 mass% Si (1/5 with respect to mass% of Ni) were added to molten copper with respect to molten copper, and finally, Mg of predetermined concentration was added. Then, it inject | poured into the metal mold | die, and produced the ingot of width 60mm and thickness 30mm.

Using the above as basic conditions for ingot production, the charcoal coating conditions of the molten metal, the presence or absence of molten flux addition to the molten metal, the holding time from the addition of Mg to the start of injection, and the conditions of the Mg addition concentration were changed as follows.

(1) Charcoal coating: After electric copper melting (before addition of Ni and Si), the charcoal piece about 10 mm in diameter was added to the crucible, and the molten metal surface was covered. The number of charcoal pieces added was 15 or 30 pieces. Charcoal coating suppresses the production of Mg-O.

(2) Coating by melt flux: After addition of Ni and Si, 20 g of borax (Na ₂ B ₄ O ₇ ) was added to the crucible. Borax melts to cover the melt surface. As borax absorbs Mg-O, floating separation of Mg-O is promoted.

(3) Holding time from the addition of Mg to the start of injection: It was carried out under two conditions: injecting immediately after Mg addition (0 minutes), and injecting after holding for 3 minutes immediately after Mg addition. During the holding, oscillation of the high frequency in the melting furnace was stopped.

(4) Addition amount of Mg: 20g (0.2 mass% with respect to the molten mass) or 50g (0.5 mass% with respect to the molten mass) was added.

Next, after heating this ingot for 3 hours at 950 degreeC, it hot-rolled to thickness 8mm. After the oxidation scale of the surface of this hot rolled material was removed with a grinder, it was cold rolled to the plate thickness of 0.3 mm. After heating at 800 ° C. for 20 seconds as a solution treatment and quenching in water, the surface oxide film was removed by chemical polishing. Then, it cold-rolled to 0.15 mm of plate | board thickness, and heated at 450 degreeC in hydrogen for 3 hours as an aging treatment.

The following evaluation was performed about the sample produced in this way.

(1) O concentration

O concentrations were analyzed by combustion-infrared absorption method.

(2) Mg concentration

Mg concentration was analyzed by ICP (high frequency plasma) -luminescence spectroscopy.

(3) Number of Mg-O Inclusion Groups

A cross section perpendicular to the rolling direction is finished by mirror polishing using diamond abrasive grains having a diameter of 1 μm, and the number of Mg-O inclusion groups having a length of 0.05 mm or more at 400 times magnification using an optical microscope. Was measured. The observation area was 60 mm 2. In addition, the maximum length of the observed Mg-O inclusion group was 0.16 mm. In addition, the diameter of the observed Mg-O particle was 0.3-0.8 micrometers. It was confirmed by analyzing the component of the measured inclusion group that it is Mg-O using the EDS (energy dispersive X-ray analysis) of FE-SEM (electrolytic radiation scanning electron microscope).

(4) bending workability

According to JIS-H 3110, the W bending test was performed in the direction (Bad Way) in which a bending axis becomes parallel to a rolling direction. The bending radius was 0.15 mm and the width of the test piece was 10 mm. About each sample, the bending test of 20 test pieces was done. No large cracks were generated by this bending test. However, when the surface of the bent portion was observed by SEM, minute cracks of about 0.1 to 0.5 mm in length and about 0.01 mm in opening width were observed depending on the sample. About each sample, the number of test pieces in which the crack of 0.1 mm or more in length was observed among 20 test pieces was calculated | required.

(5) Ni plating property

A test piece having a rectangular shape of 50 mm in width was taken, and the surface was washed in the order of acetone degreasing, electrolytic degreasing, and pickling with 10vo1% sulfuric acid aqueous solution. Then, Ni plating of 1.5 micrometers in thickness was performed using the phenol sulfonic-acid Ni-boric acid bath. The plating area was 2500 mm 2. In all samples, the plating was normally electrodeposited at the naked eye level, but when observed with an optical microscope, a portion (pin hole) where Ni plating was missing was observed depending on the sample. The area of 2500 mm <2> was observed using the optical microscope, and the number of the pinholes whose width is 10 micrometers or more was calculated | required. In addition, the width of the pinhole was made into the diameter of the minimum circle | round | yen surrounding the pinhole.

Table 1 shows the O concentration, the number of Mg-O inclusion groups, the bending, and the Ni plating test results when the ingot was manufactured under various conditions.

When holding | maintenance for floating separation of Mg-O was performed (No. 1-3), the number of Mg-O inclusion groups exceeded 1 / mm <2> regardless of charcoal coating conditions.

By carrying out charcoal coating and holding to separate Mg-O from flotation (Nos. 5 to 6), the number of Mg-O inclusion groups was 1 / mm 2 or less. In addition, when the molten flux was coated with the molten flux (Nos. 8 and 9), the number of Mg-O inclusion groups was further reduced.

Even in the case of holding and holding Mg-O for floating separation, the number of Mg-O inclusion groups exceeded 1 / mm 2 if charcoal coating was not performed (No. 4, 7).

If Mg exceeding 0.3 mass% is added (No. 10), the number of Mg-O inclusion groups is 1 / mm2 even if all of the fats and oils, charcoal coating, and molten flux coating for floating separation of Mg-O are carried out. Exceeded.

In addition, there is no clear correlation between the number of Mg-O inclusion groups and the O concentration.

Next, when the number of Mg-O inclusion groups was 1 piece / mm <2> or less, the micro crack in a bending part and the pinhole of Ni plating were not observed. However, these defects occurred when the number of Mg-O inclusion groups exceeded 1 piece / mm <2>. As the number of Mg-O inclusion groups increased, the number of these defects increased.

The above results indicate that in order to ensure high reliability as a material for fine parts, a treatment for maximally preventing the oxidation of Mg by floating charcoal and floating the Mg-O is necessary. In addition, it is difficult to manage the above-described characteristics as an index and indicates that management of the distribution of the Mg-O inclusion group is necessary.

The Cu—Ni—Si—Mg based copper alloy strip of the present invention exhibits good solder wettability, plating property, and bending workability stably.

Claims (3)

It contains 1.0-4.5 mass% of Ni, It contains 1 / 6-1 / 4 Si with respect to the mass% of Ni, It contains 0.05-0.3 mass% Mg, The balance is a copper base alloy composed of Cu and unavoidable impurities, Cu-Ni-Si-Mg-based copper alloy strips, characterized in that the number of inclusion groups composed of Mg oxide particles observed in a cross section perpendicular to the rolling direction has a length of 0.05 mm or more. . The Cu-Ni-Si-Mg system according to claim 1, wherein 0.01 to 2.0% by mass of at least one selected from the group consisting of Sn, P, Fe, Co, Mo, Mn, Zn and Ag is contained. Copper alloy strip. The component for electronic devices obtained by processing the copper alloy strip of Claim 1 or 2.

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