WO2009123139A1

WO2009123139A1 - Tin-plated cu-ni-si alloy strip with excellent unsusceptibility to thermal tin deposit peeling

Info

Publication number: WO2009123139A1
Application number: PCT/JP2009/056539
Authority: WO
Inventors: 真之長野
Original assignee: 日鉱金属株式会社
Priority date: 2008-03-31
Filing date: 2009-03-30
Publication date: 2009-10-08
Also published as: TW200948991A

Abstract

A tin-plated Cu-Ni-Si alloy strip having excellent unsusceptibility to thermal tin deposit peeling. The tin-plated copper alloy strip is a tin-plated strip of a copper alloy which contains 1.0-4.5 mass% nickel and contains silicon in an amount of 1/6 to 1/4 the mass% of the nickel and which optionally contains at least one member selected from a group consisting of zinc, tin, magnesium, cobalt, silver, chromium, and magnesium in a total amount of 2.0 mass% or smaller, the remainder being copper and incidental impurities. The interface between the copper alloy and the deposit phase directly overlying the alloy has a silicon concentration which is not higher than 120% of the silicon concentration of the copper alloy composition.

Description

Cu-Ni-Si alloy tin-plated strips with excellent heat-resistant peelability for tin plating

The present invention relates to a Cu—Ni—Si alloy tin-plated strip having good heat-resistant peelability, which is suitable as a conductive spring material for connectors, terminals, relays, switches and the like.

Conventionally, solid solution strengthened copper alloys represented by phosphor bronze and brass have been used as copper alloys for electronic materials such as connectors and terminals. However, in recent years, with the progress of miniaturization of terminals, connectors, etc., the amount of precipitation hardening type copper alloys having higher strength and higher electrical conductivity is increasing in place of conventional solid solution strengthened copper alloys. In precipitation-hardened copper alloys, by aging the supersaturated solid solution that has undergone solution treatment, fine precipitates are uniformly dispersed, increasing the strength of the alloy and reducing the amount of solid solution elements in the copper. , Electrical conductivity is improved. For this reason, precipitation hardening type copper alloys are excellent in strength and electrical conductivity.
A typical precipitation hardening type copper alloy is a Cu—Ni—Si alloy, which has been put to practical use as a copper alloy for electronic materials. In this copper alloy, the strength and electrical conductivity are increased by the precipitation of fine Ni—Si intermetallic particles in the copper matrix. In a general manufacturing process of a Cu—Ni—Si based alloy, in the same way as a normal precipitation hardening type copper alloy, first, melting in the atmosphere is performed to cast an ingot having a desired composition. Thereafter, hot rolling, cold rolling and aging heat treatment are performed to finish the strip or foil having a desired thickness and characteristics.

The Cu—Ni—Si based alloy Sn plated strip obtained by applying Sn plating to the Cu—Ni—Si based alloy strip manufactured as described above makes use of the excellent solder wettability and electrical connectivity of Sn. It is used as a consumer connector and terminal. Therefore, the Cu—Ni—Si based alloy Sn plating strip is required to have excellent strength, high electrical / thermal conductivity, and excellent properties such as heat-resistant peelability of tin plating.
The Sn-plated strip of Cu-Ni-Si alloy is generally degreased and pickled in a continuous plating line, followed by electroplating and then Sn plating by electroplating. Finally, Manufactured in a process of reflow treatment and melting the Sn plating layer.
As the base plating of the Cu—Ni—Si based alloy Sn plating strip, Cu base plating is generally used, and Cu / Ni two-layer base plating may be applied for applications requiring heat resistance. Here, the Cu / Ni two-layer undercoat is obtained by performing reflow treatment after performing electroplating in the order of Ni undercoat, Cu undercoat, and Sn plating. This technique is disclosed in Patent Documents 1 to 3 (Japanese Patent Laid-Open Nos. 6-196349, 2003-293187, and 2004-68026).

Regarding plating peelability, in Patent Document 4 (Japanese Patent Laid-Open No. 9-209062), the size of Si oxide is limited in order to improve solder wettability and heat swell resistance of Ag plating.
JP-A-6-196349 JP 2003-293187 A JP 2004-68026 A Japanese Patent Laid-Open No. 9-209062

However, the Cu-Ni-Si-based alloy Sn plating strips of Patent Documents 1 to 3 have a problem that the plating layer peels off from the base material when held at a high temperature for a long time.
Patent Document 4 relates to Ag plating, not Sn plating, and is not economically preferable. In order to improve the heat swell resistance, the limitation of the size of the Si oxide employed in the same document is not changed. Even if it is applied to Sn plating, excellent effects cannot be expected because the plating components are different.
Therefore, the present inventors have improved the heat peelability of the Cu—Ni—Si based alloy tin plating strip from a viewpoint completely different from the above prior art.

The present inventors pay attention to the Si concentration at the interface between the base material of the Cu-Ni-Si-based alloy Sn plating strip subjected to the reflow treatment and the plating layer immediately above the reflow treatment, The following knowledge was obtained by investigating the relationship.
As described above, the Cu—Ni—Si based alloy is subjected to an aging treatment on the solution-treated supersaturated solid solution, whereby fine Ni—Si compound particles are precipitated and contribute to an increase in strength. However, not all of the solid solution Si precipitates as a Ni—Si compound, and a part remains in the Cu matrix. The remaining solid solution Si naturally remains even after plating, and moves to the interface between the base material and the plating phase after plating to generate a Si concentrated layer at the interface. The Si concentrated layer formed at the base material / plating phase interface causes plating peeling. Therefore, in order to obtain good heat-resistant peelability of plating, it is necessary to prevent the Si concentration from increasing under the interface between the base material after the reflow treatment and the plating phase.

Conventionally, aging treatment is performed in a reducing atmosphere to prevent surface oxidation, and plating is performed after removing a small amount of Cu and / or Si oxide formed on the surface of the base material after aging by pickling or the like. It was. However, even if aging is performed in a reducing atmosphere and plating is performed after pickling, a Si-concentrated layer is easily formed immediately under the interface for a long period of time or under heating conditions, and plating peeling is promoted.
The inventor of the present invention pays attention to the fact that a Si-deficient layer is formed under the Si-concentrated layer when a thick Si-concentrated layer is formed on the surface of the base alloy before plating treatment in a relatively short time (see FIG. 1). The present invention has been completed. That is, when a thick Si concentrated layer is formed on the surface of the base material intentionally under a predetermined condition, and then plating is carried out after removing most of the Si concentrated layer, the interface between the base material and the plating phase is in a Si deficient state. Thus, even after long-term storage and / or heating, formation of a Si-concentrated layer below the base material / plating phase interface can be prevented, and thus a plating strip excellent in heat-resistant peelability can be produced.
Thus, the present invention focuses on the Si concentration under the copper base material / plating phase interface, not the size of the Si oxide presented in Patent Document 4, in order to improve the heat-resistant peelability of Sn plating. The following plating strips are provided.

(1) 1.0 to 4.5% by mass of Ni, 1/6 to 1/4 of Si with respect to the mass% of Ni, and further Zn, Sn, Mg, Co, if necessary A copper alloy tin-plated strip containing at least one selected from the group consisting of Ag, Cr and Mn in a total amount of 2.0% by mass or less, the balance being composed of copper and unavoidable impurities. A Cu—Ni—Si alloy tin-plated strip characterized in that the Si concentration at the interface with the plating phase is 110% or less of the Si concentration of the copper alloy composition.
(2) From the surface to the base material, a plating film is composed of each layer of Sn phase, Cu—Sn alloy phase, and Cu phase, the average thickness of Sn phase is 0.1 to 1.5 μm, and the average of Sn—Cu alloy phase The Cu—Ni—Si alloy tin-plated strip according to (1), wherein the thickness is 0.1 to 1.5 μm and the average thickness of the Cu phase is 0 to 0.8 μm.
(3) From the surface to the base material, a plating film is composed of each layer of Sn phase, Cu—Sn alloy phase and Ni phase, the average thickness of Sn phase is 0.1 to 1.5 μm, and the average of Sn—Cu alloy phase The Cu—Ni—Si alloy tin-plated strip according to (1), wherein the thickness is 0.1 to 1.5 μm and the average thickness of the Ni phase is 0.1 to 1.0 μm.

We provide Cu-Ni-Si alloy tin plating strips with excellent heat-resistant peelability for tin plating.

It is Si density | concentration profile of the base material after the aging treatment of this invention. It is a density | concentration profile with respect to the depth direction of Ni with respect to the Cu / Ni base Sn plating copper alloy of this invention. It is a density | concentration profile with respect to the depth direction of Si with respect to the Cu / Ni base Sn plating copper alloy of this invention.

(1) Base Material Components Ni and Si are subjected to an aging treatment to precipitate Ni and Si compound particles in a Cu matrix, thereby obtaining high strength and electrical conductivity.
Ni is added in the range of 1.0 to 4.0% by mass. If Ni is less than 1.0, sufficient strength cannot be obtained. When Ni exceeds 4.0 mass%, a crack generate | occur | produces by casting or hot rolling.
The additive concentration (mass%) of Si is in the range of 1/6 to 1/4, preferably 1/5 to 1/4 of the additive concentration (mass%) of Ni. If Si deviates from this range, the conductivity decreases. In particular, when the addition amount of Si exceeds 1/4 of Ni, solute Si increases, the Si concentration at the interface between the copper alloy and the plating phase increases, and the Si-deficient layer associated with the Si concentration treatment is not formed, Reduces heat-resistant peelability.
In order to improve properties such as strength and heat resistance, at least one selected from the group consisting of Zn, Sn, Mg, Co, Ag, Cr and Mn can be added. However, since the electrical conductivity decreases as the amount added increases, the total amount added is 2.0% by mass or less.

(2) Si concentration at the interface between the base material and the plating phase In the present invention, the “interface between the copper alloy and the plating phase” means Sn of the Sn plating strip after reflow by GDS (glow discharge issuance spectroscopy analyzer), It is obtained as follows from the concentration profile of Cu, Ni, and Si in the depth direction.
(A) In the case where the Cu plating layer remains on the Cu base, a position where the Cu concentration is intermediate between the Cu concentration of the base material and the maximum value of the Cu concentration profile is defined as the interface.
(A) When the Cu plating layer does not remain on the Cu base, the plating layer immediately above the base material is Cu ₆ Sn ₅ . Therefore, in the Cu concentration profile, the position at which the Cu concentration is intermediate between the Cu concentration of the base material and the Cu concentration of Cu ₆ Sn ₅ (39.1 wt%) is defined as the interface.
(C) In the case of a Cu / Ni base, in the Ni concentration profile, the position where the Ni concentration is intermediate between the Ni concentration of the base material and the maximum value of the Ni concentration profile is defined as the interface.
In the present invention, the “Si concentration at the interface between the copper alloy and the plating phase” refers to the maximum value of the Si concentration within a depth range of 0.5 μm from the interface. In order to obtain excellent tin plating heat-resistant peelability, this maximum value, that is, the Si concentration at the interface between the copper alloy and the plating phase is 110% or less, preferably less than 100% of the Si concentration of the copper alloy composition. There must be. If it exceeds 110%, plating peeling occurs after long-term storage and / or heating conditions.
In the present invention, the “Si-deficient layer” refers to a portion that is continuously lower than the Si concentration of the copper alloy composition, and specifically refers to a portion that is less than 100%, particularly 95% or less.

The Cu—Ni—Si based alloy of the present invention is produced, for example, by appropriately changing and adjusting “melting, casting → homogenization → hot rolling → cold rolling 1 → solution forming → cold rolling 2 → aging”. In the production of the tin-plated alloy strip according to the present invention, a thick Si-enriched layer is formed intentionally on the surface of the base material, and at the same time an Si-deficient layer is formed. When the aging treatment is carried out in the presence of oxygen or other compounds that easily bind to Si, not in a conventional reducing atmosphere, a Si concentrated layer with a Si deficient layer shown in FIG. 1 can be formed. In the Si concentration profile of FIG. 1, a valley portion of the Si-deficient layer is observed from the surface in the depth direction following the peak of the Si-enriched layer, and thereafter, the Si concentration has a constant copper alloy composition.
For example, when the oxygen concentration in the ambient atmosphere of the aging treatment is adjusted to 5 to 50 ppm and the formation of the Si oxide layer on the alloy surface is promoted, a target Si concentrated layer is generated. The oxygen concentration can be appropriately changed depending on the aging temperature, time, and degree of surface layer removal.
The Si concentrated layer on the surface of the base material copper alloy obtained by the aging treatment is removed by polishing, buffing, pickling or the like.

After the removal of the Si enriched layer, a plating treatment is performed to obtain the alloy tin plating strip of the present invention. The plating process is performed within a temperature range of 20 to 80 ° C. and a plating time of 3 to 120 seconds. The reflow treatment temperature after plating is 230 to 550 ° C., and the reflow treatment time is 3 to 10 seconds.
The plating strip of this invention is manufactured by the said process.

(3) Plating thickness (3-1) Cu underlayer reflow Sn
From the surface to the base material, a plating film is composed of layers of Sn phase, Cu—Sn alloy phase, and optionally remaining Cu phase. This plating film structure is obtained by performing electroplating on the base material in the order of Cu base plating and Sn plating, and performing reflow treatment. The thicknesses of the Sn phase and the Cu—Sn phase are determined by an electrolytic film thickness meter.
The thickness of the Sn phase after the reflow treatment is 0.1 to 1.5 μm. When the thickness is less than 0.1 μm, solder wettability and contact resistance deterioration under high temperature environment are remarkably accelerated. When the thickness exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, resulting in plating peeling. Is promoted.
The thickness of the Cu—Sn alloy phase after reflow is 0.1 to 1.5 μm. Since the Cu—Sn alloy phase is hard, if it exists in a thickness of 0.1 μm or more, it contributes to a reduction in insertion force. On the other hand, when the thickness of the Cu—Sn alloy phase exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted.
The thickness of the Cu plating phase formed by electroplating is 0 to 0.8 μm. When the thickness exceeds 0.8 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. The preferable thickness of the Cu plating layer is 0.4 μm or less. However, it is more preferable that the thickness of the Cu plating layer is zero because it is consumed for forming the Cu—Sn alloy phase during reflow.

At the time of each electroplating, the Sn plating layer thickness is appropriately adjusted so as to be formed in the range of 0.5 to 2.0 μm, and the Cu plating layer thickness in the range of 0.1 to 1.5 μm. Then, the said plated structure is obtained by performing a reflow process on suitable conditions.

(3-2) Cu / Ni underlayer reflow Sn plating A plating film is composed of layers of Sn phase, Cu—Sn alloy phase and Ni phase from the surface to the base material. This plating film structure is obtained by performing electroplating on the base material in the order of Ni base plating, Cu base plating, and Sn plating, and performing reflow treatment. By the reflow process, Cu and Sn between the plating layers react to form a Cu—Sn alloy layer. On the other hand, the Ni plating layer remains almost in the state (thickness) after electroplating. The thickness of the Ni phase is determined by SEM observation from the cross section.
The thickness of the Sn phase and the thickness of the Cu—Sn alloy phase after the reflow treatment are the same as those of the Cu underlayer reflow Sn.
The thickness of the Ni phase after reflowing is 0.1 to 1.0 μm. When the thickness of the Ni phase is less than 0.1 μm, the corrosion resistance and heat resistance of the plating deteriorate. On the other hand, when the thickness of the Ni phase after reflow exceeds 1.0 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted.

During each electroplating, the Sn plating layer thickness is in the range of 0.5 to 2.0 μm, the Cu plating layer thickness is in the range of 0.1 to 1.0 μm, and the Ni plating layer thickness is in the range of 0.1 to 0.8 μm. Adjust as appropriate. Then, the said plated structure is obtained by performing a reflow process on suitable conditions.

In the present invention, “excellent in heat-resistant peelability” means that after heating, 90 ° bending with a bending radius of 0.5 mm and bending back are performed, and plating peeling does not occur.

An example in which a Cu—Ni—Si based alloy, which is excellent in strength and conductivity as a female terminal material, is used as a plating base material is shown below.
Electrolysis was performed in a copper nitrate bath using commercially available electrolytic copper as an anode, and high purity copper was deposited on the cathode. The P, As, Sb, Bi, Ca, Mg, and S concentrations in this high purity copper were all less than 1 ppm by mass. Hereinafter, this high purity copper was used for the following ingot production material.
Using a high-frequency induction furnace, 2 kg of high-purity copper was dissolved in a graphite crucible having an inner diameter of 60 mm and a depth of 200 mm. After covering the surface of the molten metal with charcoal pieces, a predetermined amount of Ni, Si and additional elements were added, and the molten metal temperature was adjusted to 1200 ° C.
Thereafter, the molten metal was cast into a mold to produce an ingot having a width of 60 mm and a thickness of 30 mm, and processed into a Cu base reflow Sn plating material and a Cu / Ni base reflow Sn plating material in the following steps.
(Step 1) After heating at 950 ° C. for 3 hours, hot rolling to a thickness of 8 mm.
(Step 2) The oxidized scale on the surface of the hot rolled plate is ground and removed with a grinder.
(Step 3) Cold rolling to a plate thickness of 0.3 mm.
(Step 4) As a solution treatment, the solution is heated at 800 ° C. for 1 minute and then rapidly cooled in water.
(Step 5) The electric furnace is evacuated to a vacuum degree of 10 ⁻⁴ Pa or less and replaced with nitrogen gas having a purity of 99.99998%. This operation is repeated twice or more. Thereafter, oxygen gas having a purity of 99.9999% is injected and controlled to a predetermined oxygen concentration. As an aging treatment, after holding at 460 ° C. for 6 hours in an electric furnace controlled to a predetermined oxygen concentration, cooling is performed as it is.
(Step 6) Cold rolling to a plate thickness of 0.25 mm.
(Step 7) After holding at 500 ° C. for 10 seconds in an electric furnace in a nitrogen atmosphere, buffing is performed in a 10 vol% sulfuric acid-1 vol% peroxide aqueous solution to remove the Si concentrated layer on the copper alloy surface.

(Step 8) Ni foundation plating is performed under the following conditions (only Cu / Ni foundation reflow Sn plating).
-Plating bath composition: nickel sulfate 250 g / L, nickel chloride 45 g / L, boric acid: 30 g / L.
-Plating bath temperature: 50 ° C.
Current density: 5A / dm ^2.
・ Ni plating thickness is adjusted by electrodeposition time.
(Step 9) Cu base plating is performed under the following conditions.
-Plating bath composition: copper sulfate 200 g / L, sulfuric acid 60 g / L.
Plating bath temperature: 25 ° C.
Current density: 5A / dm ^2.
・ Cu plating thickness is adjusted by electrodeposition time.
(Step 10) Sn plating is performed under the following conditions.
Plating bath composition: stannous oxide 41 g / L, phenol sulfonic acid 268 g / L, surfactant 5 g / L.
Plating bath temperature: 50 ° C.
Current density: 9A / dm ^2.
Sn plating thickness is adjusted by electrodeposition time.
(Step 11) As a reflow treatment, the substrate is held in a heating furnace adjusted to a nitrogen atmosphere and a temperature of 550 ° C. for 5 seconds, and then cooled with water.
The following evaluation was performed about the sample produced in this way.

(A) Component analysis of base material After the plating layer was completely removed by mechanical polishing and chemical etching, additional elements other than Cu were measured by ICP-emission spectroscopy.
(B) Measurement of plating thickness The thickness of each layer of the Sn phase, Cu-Sn alloy phase, and Ni phase was determined.
(A) Since the cross-sectional shape of the Cu—Sn alloy phase is dome-shaped, the thicknesses of the Sn phase and the Cu—Sn alloy phase are determined by cross-sectional observation, and the values vary greatly depending on the measurement location. Therefore, the thicknesses of the Sn phase and the Cu—Sn alloy phase were determined according to JIS H8501 using a CT-1 type electrolytic film thickness meter (manufactured by Denso Co., Ltd.). The measured value is an average value obtained by measuring five arbitrary points from the portion excluding 10 mm from the edge of the sample. For the measurement, an electrolytic solution “R-50” manufactured by Kocourt was used. In the case of Cu-based Sn plating, when electrolysis is performed with the electrolytic solution R-50, the Sn plating layer is first electrolyzed and the electrolysis stops before the Cu-Sn alloy layer, and the displayed value of the device here is the Sn plating layer thickness. It becomes. Next, the electrolysis is started again and the Cu—Sn alloy layer is electrolyzed until the next time the apparatus is stopped, and the displayed value at the end time corresponds to the thickness of the Cu—Sn alloy layer.
(I) The thickness of the Ni phase was determined by SEM observation from the cross section because there was no appropriate electrolytic solution. In a direction parallel to the rolling direction, the width of 10 mm × length 20 mm is cut from the portion excluding 10 mm from the edge of the sample, the plated cross section is finished to a mirror surface by mechanical polishing, and 20,000 times by PHEMIPS SEM (XL30) Observed at. The thickness of the Ni phase at five locations was measured arbitrarily from the observation surface, and the average value was taken as the Ni plating layer thickness.

(C) Amount of pickling polishing The plate thickness of the sample before and after the pickling polishing was measured with a micrometer, and the pickling polishing amount was determined from the difference in the plate thickness before and after the pickling polishing.
(D) Si concentration profile and interfacial Si concentration After the sample was ultrasonically degreased in acetone, the concentration profile of Si in the depth direction was determined by GDS (glow discharge emission spectroscopic analyzer) analysis from the surface. The measurement conditions are as follows.
Apparatus: JY5000RF-PSS type Current Method Program manufactured by JOBIN YBON: CNBintel-12aa-0
Mode: Set power = 40W
Atmospheric pressure: 775 Pa
Current value: 40 mA (700 V)
Flash time: 20s
Preheating time: 2 s
Measurement (analysis) time = 30 s, sampling time = 0.020 s / point

The Si concentration at the interface between the base material and the plating phase was determined from the concentration profile data.
Representative examples of density profile data by GDS are shown in FIGS. 2 and 3 are data of a Cu / Ni base plating material (after Sn plating) of Invention Example 14 to be described later. FIG. 2 is a concentration profile of Ni with respect to the depth direction. A Ni concentration peak is detected in the depth range of 1.8 to 2.8 μm, the intermediate between this peak concentration and the Ni concentration of the copper alloy is 47%, and the depth at that time is 2.5 μm. That is, it was determined that the interface between the plating phase and the copper alloy exists at a depth of 2.5 μm. On the other hand, FIG. 3 shows a Si concentration profile in the depth direction of the same sample. The maximum value of the Si concentration in the range from the interface having the depth of 2.5 μm to the depth of 0.5 μm (that is, the depth from the surface of 2.5 to 3.0 μm) is 0.31% by weight. there were. Therefore, the Si concentration at the interface between the copper alloy of Invention Example 14 and the plating phase was 94%, which was less than 100% of the Si concentration of the copper alloy composition.

(E) Heat-resistant peelability A strip test piece having a width of 10 mm was collected and heated at a temperature of 150 ° C. for up to 1000 hours in the atmosphere. In the meantime, the sample was taken out from the heating furnace every 50 hours, and 90 ° bending with a bending radius of 0.5 mm and bending back were performed. And the bending inner peripheral part surface was observed with the optical microscope (50-times multiplication factor), and the presence or absence of plating peeling was investigated.

Table 1 shows an example in which the influence of the Si concentration at the interface between the base material and the plating phase on the heat-resistant peelability was investigated.
For the Cu underplating materials of Invention Examples 1 to 10 and Comparative Examples 11 to 13, the Cu plating bath temperature was 25 ° C., the plating time was 15 seconds, the thickness was 0.3 μm, the Sn plating bath temperature was 50 ° C., and the plating time. Electroplating was performed for 30 seconds and a thickness of 0.8 μm.
The thickness of the Sn phase after reflowing at 550 ° C. for 5 seconds was about 0.4 μm regardless of the sample, the thickness of the Cu—Sn alloy phase was about 1 μm, and the Cu phase disappeared.
For the Cu / Ni base plating materials of Invention Examples 14 to 23 and Comparative Examples 24 to 26, the Ni plating bath temperature was 50 ° C., the plating time was 20 seconds, the thickness was 0.4 μm, and the Cu plating bath temperature was 25 ° C. The electroplating was performed with a plating time of 15 seconds, a thickness of 0.3 μm, a Sn plating bath temperature of 50 ° C., a plating time of 30 seconds, and a thickness of 0.8 μm.
The thickness of the Sn phase after reflowing at 550 ° C. for 5 seconds is about 0.4 μm regardless of the sample, the thickness of the Cu—Sn alloy phase is about 1 μm, the Cu phase disappears, and the Ni phase is 0.4 μm. It remained as it was when it was worn.

The Si concentration ratio at the interface between the base material and the plating phase in Invention Examples 1 to 9 and 14 to 22 is less than 100% of that of the base material immediately after plating and after the heat resistance test at 150 ° C. for 1000 hours, Regardless of the Cu / Ni base, plating peeling did not occur even when heated at 150 ° C. for 1000 h.
The Si concentration ratio at the interface between the base material and the plating phase in Invention Examples 10 and 23 is within the range of 100 to 110% of that of the base material both after the plating and after the heat resistance test at 150 ° C. for 1000 hours. When both the Cu / Ni bases were heated for a long time, plating peeling occurred. However, the peeling is slight and there is no problem in practical use.
In Comparative Examples 11 and 24 with respect to Invention Examples 7 and 20, the pickling polishing amount (thickness reduced by polishing) was reduced. In Comparative Examples 11 and 24, the pickling polishing amount is insufficient, so that the Si concentration at the interface between the base material and the plating phase is higher than 110% of that of the base material immediately after plating and after the heat resistance test. Occurred.
Compared with Invention Examples 8 and 21, in Comparative Examples 12 and 25, the oxygen concentration in the aging treatment is lowered. Since Comparative Example 12 had a low oxygen concentration, the Si concentration gradually increased from the base material to the surface, and no Si-deficient layer was formed. Therefore, even when pickling and polishing is performed in the same manner as in Invention Examples 8 and 21, the Si concentration at the interface between the base material and the plating phase is higher than 110% of that of the base material immediately after plating and after the heat resistance test, so that the plating is peeled off. There has occurred.
Compared to Examples 10 and 23, Comparative Examples 13 and 26 are alloys in which the Si concentration of the base material exceeds 1/4 of the Ni concentration, and the amount of solute Si is large. In pickling polishing, the Si-enriched layer on the surface of the base material could not be sufficiently removed, and its concentration was higher than 110% of that of the base material, and plating peeling occurred.

Table 2 shows examples in which the influence of plating thickness on heat-resistant peelability was investigated. In all samples, the composition of the base material is 2.80Ni-0.59Si-0.52Sn-0.41Zn, the aging oxygen concentration is 10 ppm, the pickling polishing amount is about 1 μm, the temperature of the plating bath is Ni at 50 ° C, The plating time is 20 seconds, Cu is 25 ° C., plating time is 15 seconds, Sn is 50 ° C., plating time is 30 seconds, and the Si concentration at the interface between the base material and the plating phase is 110% or less of that of the base material immediately after plating. It is.

Inventive Examples 27 to 29 and 31, and Comparative Examples 32 to 34 are examples of the Cu base plating material. In Invention Examples 27 to 29 and 31, plating peeling did not occur even when heated at 150 ° C. for 1000 h.
Comparative Example 32 has a Sn thickness after reflow exceeding 1.5 μm, Comparative Example 33 has a Sn—Cu alloy phase thickness after reflow exceeding 1.5 μm, and Comparative Example 34 has a Cu phase thickness after reflow. It exceeded 0.8 μm. Plating peeling occurred in these alloys whose plating thickness exceeded the specified range.
Invention Examples 35 to 37, 39 and Comparative Examples 40 to 41 are examples of Cu / Ni undercoat. In all samples, the plated Cu was consumed for forming the Cu—Sn alloy phase during reflow, and its thickness became zero. In Invention Examples 35 to 37 and 39, plating peeling did not occur even when heated at 150 ° C. for 1000 h.
The Si concentration ratio at the interface between the base material and the plating phase in Invention Examples 30 and 38 is within the range of 100 to 110% of that of the base material both after the plating and after the heat resistance test at 150 ° C. for 1000 hours. When both the Cu / Ni bases were heated for a long time, plating peeling occurred. However, the peeling is slight and there is no problem in practical use.
Comparative Example 40 has a Sn thickness after reflow exceeding 1.5 μm, Comparative Example 41 has a Sn—Cu alloy phase thickness after reflow exceeding 1.5 μm, and Comparative Example 42 has a Ni phase thickness after reflow. It exceeded 1.0 μm. Plating peeling occurred in these alloys whose plating thickness exceeded the specified range.

Claims

1.0 to 4.5% by mass of Ni, 1/6 to 1/4 of Si with respect to the mass% of Ni, and further Zn, Sn, Mg, Co, Ag, Cr as required And at least one selected from the group of Mn is 2.0% by mass or less in total, the remainder being a copper alloy tin plating strip composed of copper and inevitable impurities, a copper alloy and a plating phase immediately above it A Cu—Ni—Si alloy tin-plated strip characterized in that the Si concentration at the interface is 110% or less of the Si concentration of the copper alloy composition.
From the surface to the base material, a plating film is composed of layers of Sn phase, Cu—Sn alloy phase, and Cu phase, the average thickness of Sn phase is 0.1 to 1.5 μm, and the average thickness of Sn—Cu alloy phase is 0 The Cu-Ni-Si alloy tin-plated strip according to claim 1, wherein the Cu-Ni-Si alloy tin-plated strip has an average thickness of 1 to 1.5 µm and a Cu phase of 0 to 0.8 µm.
From the surface to the base material, a plating film is composed of layers of Sn phase, Cu—Sn alloy phase and Ni phase, the average thickness of Sn phase is 0.1 to 1.5 μm, and the average thickness of Sn—Cu alloy phase is 0 The Cu—Ni—Si alloy tin-plated strip according to claim 1, wherein the Ni-phase alloy has an average thickness of 0.1 to 1.0 μm.