JP4538424B2 - Cu-Zn-Sn alloy tin-plated strip - Google Patents

Description

  The present invention relates to a Cu—Zn—Sn alloy Sn plating strip that is suitable as a conductive material for connectors, terminals, relays, switches, and the like and has good heat-resistant peelability.

In various terminals, connectors, relays, switches, etc. of electrical and electronic equipment, inexpensive brass is used when manufacturing cost is important. Further, phosphor bronze is used in applications where springiness is important, and white is used in applications where spring properties and corrosion resistance are important. These copper alloys are solid solution strengthened alloys, and the strength and spring property are improved by the action of the alloy elements, but the conductivity and thermal conductivity are lowered.
In recent years, the amount of precipitation-strengthened copper alloys used has increased in place of solid solution strengthened alloys. The precipitation-strengthened alloy is characterized in that an alloy element is precipitated as fine compound particles in a Cu matrix. As the alloying elements precipitate, the strength increases and at the same time the conductivity increases. Therefore, in the precipitation strengthening type alloy, higher conductivity can be obtained with the same strength than the solid solution strengthening type alloy. Examples of the precipitation strengthening type copper alloy include a Cu—Ni—Si alloy, a Cu—Be alloy, a Cu—Ti alloy, a Cu—Zr alloy, and the like.
However, in precipitation-strengthened alloys, there are high-temperature and short-time heat treatment (solution treatment) for once dissolving the alloy elements in Cu and low-temperature and long-time heat treatment (aging treatment) for precipitating the alloy elements. It is necessary and its manufacturing process is complicated. Moreover, since an active element such as Si, Ti, Zr, or Be is contained as an alloy element, it is difficult to build ingot quality. Therefore, the manufacturing cost of the precipitation strengthening type alloy is very high compared with the manufacturing cost of the solid solution strengthening type alloy.

  Therefore, development of inexpensive copper alloys having necessary and sufficient electrical conductivity and strength has been promoted by improving solid solution strengthened alloys. A Cu—Zn alloy typified by brass is an alloy that is easy to manufacture and can be manufactured at a particularly low cost due to the fact that Zn is inexpensive. The inventors adjusted the Zn content of the Cu-Zn alloy, added a small amount of Sn, and further adjusted the metal structure to obtain an alloy having necessary and sufficient conductivity, strength and bending workability. Developed (Patent Document 1). Necessary and sufficient electrical conductivity, strength and bending workability are as follows.

(A) Conductivity: 35% IACS or higher.
This conductivity is a value comparable to the conductivity of a Cu—Ni—Si based alloy (Corson alloy) which is a precipitation strengthening type alloy. The conductivity of brass (C2600) is 28% IACS, and the conductivity of phosphor bronze (C5210) is 13% IACS.
(B) Tensile strength: 410 MPa or more.
This tensile strength corresponds to the value of the tensile strength of grade H of brass (C2600) defined by the JIS standard (JIS 3100).
(C) Bending workability: Good contact bending of Good Way and Bad Way is possible.
If no cracks or rough skin occur in this bending test, the most severe level of bending applied to the connector is possible.
The Cu—Zn—Sn alloy of Patent Document 1 developed by the present inventors has both the strength of brass, the conductivity of the Corson alloy, and the bending workability equal to or higher than that of brass and the Corson alloy. It is a copper alloy suitable as a material for advancing electronic device parts.

The Cu—Zn—Sn alloy strip is often subjected to Sn plating depending on the application. The alloy Sn plating strips are used as terminals and connectors for automobiles and consumer use, taking advantage of Sn's excellent solder wettability, corrosion resistance, and electrical connectivity. For example, Patent Document 2 discloses a Sn plating strip of a Cu-4.97 mass% Zn-0.39 mass% Sn alloy.
For the Sn-plated strip of Cu-Zn-Sn alloy, after degreasing and pickling, an underplating layer is formed by electroplating, then an Sn plating layer is formed by electroplating, and finally reflow treatment is performed. It is manufactured in the process of melting the Sn plating layer.

As the base plating of the Cu—Zn—Sn-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 base plating is a plating obtained by performing reflow treatment after performing electroplating in the order of Ni base plating, Cu base plating, and Sn plating. To Sn phase, Cu—Sn phase, Ni phase, and base material. Details of this technique are disclosed in Patent Documents 3 to 5 and the like.
When the reflow Sn plating strip of a copper alloy is held at a high temperature for a long time, a phenomenon that the plating layer generally peels from the base material (hereinafter referred to as thermal peeling) occurs. Usually, when Zn is added to a copper alloy, the thermal peeling property is improved, so that the heat-resistant peeling property of the Cu—Zn—Sn alloy is relatively good.

Japanese Patent Application No. 2005-207556 JP 7-258777 A JP-A-6-196349 JP 2003-293187 A JP 2004-68026 A

However, in recent years, long-term reliability at higher temperatures has been required for heat-resistant peelability, and even for conventional Cu-Zn-Sn alloys having relatively good heat-resistant peelability. Further, better heat-resistant peelability has been demanded.
An object of the present invention is to provide a Cu—Zn—Sn alloy tin plating strip having improved heat-resistant peelability of tin plating, and particularly improved with respect to Cu undercoat or Cu / Ni bilayer undercoat. It is to provide a Cu—Zn—Sn alloy tin-plated strip having heat-resistant peelability.

As a result of earnestly researching measures for improving the heat-resistant peelability of the tin-plated strip of the Cu—Zn—Sn-based alloy, the present inventor has found that when the C concentration at the interface between the plating layer and the base metal is kept low, It was found that can be improved significantly.
The present invention has been made based on this discovery and is as follows.
(1) 2 to 12% by mass of Zn, 0.1 to 1.0% by mass of Sn, and the mass% concentration of Sn ([% Sn]) and the mass% concentration of Zn ([% Zn]) Relationship
0.6 ≦ [% Sn] +0.16 [% Zn] ≦ 2.0
Characterized in that a copper base alloy composed of Cu and inevitable impurities is used as a base material, and the C concentration at the interface between the plating layer and the base material is 0.10% by mass or less. Cu-Zn-Sn alloy tin-plated strip.
(2) 2 to 12% by mass of Zn and 0.1 to 1.0% by mass of Sn, and the mass% concentration of Sn ([% Sn]) and the mass% concentration of Zn ([% Zn]) Relationship
0.6 ≦ [% Sn] +0.16 [% Zn] ≦ 2.0
The plating film is composed of the Sn phase, Sn-Cu alloy phase, and Cu phase layers from the surface to the base material. The Sn phase has a thickness of 0.1 to 1.5 μm, the Sn—Cu alloy phase has a thickness of 0.1 to 1.5 μm, and the Cu phase has a thickness of 0 to 0.8 μm. A Cu—Zn—Sn alloy tin-plated strip having a C concentration of 0.10% by mass or less at the interface.
(3) 2-12 mass% Zn and 0.1-1.0 mass% Sn are contained, and the mass% concentration of Sn ([% Sn]) and the mass% concentration of Zn ([% Zn]) Relationship
0.6 ≦ [% Sn] +0.16 [% Zn] ≦ 2.0
The plating film is composed of the Sn phase, Sn-Cu alloy phase, and Ni phase layers from the surface to the base material. The thickness of the Sn phase is 0.1 to 1.5 μm, the thickness of the Sn—Cu alloy phase is 0.1 to 1.5 μm, the thickness of the Ni phase is 0.1 to 0.8 μm, the plating layer and the base material Cu-Zn-Sn alloy tin-plated strips, characterized in that the C concentration at the boundary surface between the two is 0.10% by mass or less.
(4) The base material further contains at least one of Ni, Fe, Mn, Co, Ti, Cr, Zr, Al, and Ag in the range of 0.005 to 0.5 mass% (1) to (3 ) Any one of the Cu-Zn-Sn alloy tin-plated strips.
Note that tin plating of a Cu—Zn—Sn alloy may be performed before pressing a part (pre-plating) or after pressing (post-plating). In both cases, the effect of the present invention is achieved. Is obtained.

(1) Concentration of Zn and Sn The copper alloy base material of the present invention contains Zn and Sn as basic components, and creates mechanical characteristics and conductivity by the action of both elements. The ranges of Zn concentration and Sn concentration are 2 to 12% by mass and 0.1 to 1.0% by mass, respectively. If the Zn content is less than 2% by mass, the effect of Zn for improving the heat-resistant peelability of Sn plating is lost. When Zn exceeds 12% by mass, a conductivity of 35% IACS or more cannot be obtained even if the Sn concentration is adjusted. Sn has the effect | action which accelerates | stimulates the work hardening in the case of rolling, and intensity | strength will be insufficient when Sn is less than 0.1 mass%. On the other hand, when Sn exceeds 1.0 mass%, the heat-resistant peelability of Sn plating will deteriorate.
The total concentration (T) of Sn and Zn is adjusted as follows.
0.6 ≦ T ≦ 2.0
T = [% Sn] +0.16 [% Zn]
Here, [% Sn] and [% Zn] are the mass% concentrations of Sn and Zn, respectively. If T is 2.0 or less, a conductivity of 35% IACS or more can be obtained. If T is 0.6 or more, a tensile strength of 410 MPa or more can be obtained by appropriately adjusting the metal structure. Therefore, T is defined as 0.6 to 2.0.
A more preferable range of T is 1.0 to 1.7. By adjusting to this range, a conductivity of 35% IACS or more and a tensile strength of 410 MPa or more can be obtained more stably.

(2) Ni, Fe, Mn, Co, Ti, Cr, Zr, Al and Ag
The copper alloy base material of the present invention is a kind of Ni, Fe, Mn, Co, Ti, Cr, Zr, Al and Ag for the purpose of improving the strength, heat resistance and stress relaxation resistance of the alloy. A total of 0.005 to 0.5 mass% of the above can be added. However, the addition of the alloy element may cause a decrease in conductivity, a decrease in manufacturability, an increase in raw material cost, and the like, and thus this point needs to be considered.
When the total amount of the above elements is less than 0.005% by mass, the effect of improving the characteristics is not exhibited. On the other hand, when the total amount of the above elements exceeds 0.5% by mass, the decrease in conductivity becomes significant. Therefore, the total amount is specified to be 0.005 to 0.5 mass%.

(3) C concentration at the interface between the plating layer and the base material When the C concentration at the interface between the plating layer and the base material exceeds 0.10% by mass, the heat-resistant peelability decreases. Therefore, the C concentration is specified to be 0.10% by mass or less. Here, the C concentration at the boundary surface between the plating layer and the base material is, for example, a concentration profile in the depth direction of C of the sample after degreasing obtained by GDS (glow discharge emission spectroscopy analyzer). The C concentration at the peak apex that appears at the position corresponding to the boundary surface with the material.

Manufacturing condition factors affecting the C concentration at the interface between the plating layer and the base material include final cold rolling conditions and subsequent degreasing conditions. That is, since rolling oil is used in cold rolling, the rolling oil is interposed between the roll and the material to be rolled. When this rolling oil is sealed on the surface of the material to be rolled and remains without being removed by degreasing in the next step, a C segregation layer is formed at the plating / base material interface through a plating step (electrodeposition and reflow).
In the cold rolling process, the material is repeatedly passed through a rolling mill to finish the material to a predetermined thickness. FIG. 1 schematically shows a process in which rolling oil is sealed on the surface of a material to be rolled during rolling. (A) is a to-be-rolled material cross section before rolling. (B) is a cross-section of the material to be rolled after rolling using a roll having a large surface roughness that is usually used, where the surface of the material to be rolled is uneven, and rolling oil is accumulated in the recess. (C) is a cross section of the rolled material after rolling using a roll having a small surface roughness as the final pass after (b), and the rolling oil accumulated in the recesses in (b) is applied to the surface of the rolled material. It is enclosed.

FIG. 1 shows that it is important to use a roll having a low surface roughness in the pass before the final pass using a roll having a low surface roughness in order to suppress the inclusion of rolling oil. An important factor other than the surface roughness of the roll is the viscosity of the rolling oil. The rolling oil having a lower viscosity and better fluidity is less likely to be encapsulated on the surface of the material to be rolled.
As a method for reducing the surface roughness of the roll, there are a method of polishing the roll surface using a grindstone having a fine particle size, a method of plating the roll surface, etc., but these require considerable labor and cost. Moreover, if the surface roughness of the roll is made small, slips are likely to occur between the roll surface and the material to be rolled, and problems such as the inability to increase the rolling speed (decrease in efficiency) occur. For this reason, although rolls with a small surface roughness were used in the final pass to create the surface roughness of the product, those skilled in the art should avoid using rolls with a low surface roughness in passes other than the final pass. It was done. Also, the use of rolling oil having a low kinematic viscosity has been avoided for reasons such as increased wear on the surface of the rolling roll. That is, in the conventional rolling of the Cu—Zn—Sn alloy tin-plated strip disclosed in Patent Document 2 and the like, no measures for preventing rolling oil sealing have been taken.
For the first time, it has been found that it is important to reduce the C concentration at the interface between the plating layer and the base material in order to improve the thermal peelability of tin plating according to the present invention. For that purpose, it is effective to suppress the inclusion of the rolling oil by using a roll having a small surface roughness in the pass before the final pass and using a rolling oil having a low kinematic viscosity and good fluidity. It has been shown.

The maximum height roughness Rz of the roll having a small surface roughness used before the final pass is preferably 3.0 μm or less, more preferably 2.0 μm or less, and most preferably 1.0 μm or less. When Rz exceeds 3.0 μm, rolling oil is likely to be enclosed, and the C concentration at the boundary surface is unlikely to decrease. The kinematic viscosity (measured at 40 ° C.) of the rolling oil used is preferably 15 mm ² / s or less, more preferably 10 mm ² / s or less, and most preferably 5 mm ² / s or less. When the viscosity exceeds 15 mm ² / s, the rolling oil is easily enclosed, and the C concentration at the boundary surface is difficult to decrease.
Patent Document 5 also focuses on the C concentration. This C concentration is the average C concentration in the Sn plating layer, and the C concentration at the interface between the plating layer and the base material, which is a component of the present invention. Is different. The average C concentration in the Sn plating layer varies depending on the amount of brightener and additive in the plating solution and the plating current density. If it is less than 0.001% by mass, the Sn plating thickness is uneven, and 0.1% by mass. It is said that the contact resistance increases when the value exceeds. Therefore, it is clear that the technique of Patent Document 5 is different from the technique of the present invention.

(4) Thickness of plating (4-1) Cu base plating In the case of Cu base plating, a Cu plating layer and a Sn plating layer are sequentially formed on a Cu-Zn-Sn alloy base material by electroplating, and then reflow treatment is performed. I do. By this reflow treatment, the Cu plating layer and the Sn plating layer react to form an Sn—Cu alloy phase, and the plating layer structure becomes an Sn phase, an Sn—Cu alloy phase, and a Cu phase from the surface side.
The thickness of each phase after reflow is
-Sn phase: 0.1-1.5 μm,
Sn-Cu alloy phase: 0.1 to 1.5 μm
Cu phase: 0 to 0.8 μm
Adjust to the range.
When the Sn phase is less than 0.1 μm, the solder wettability decreases, and when it exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. A more preferable range is 0.2 to 1.0 μm.
Since the Sn—Cu 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 Sn—Cu alloy phase exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. A more preferable thickness is 0.5 to 1.2 μm.

In the Cu—Zn—Sn alloy, the solder wettability is improved by performing the Cu base plating. Therefore, it is necessary to apply a Cu base plating of 0.1 μm or more during electrodeposition. This Cu base plating may be consumed and lost for Sn—Cu alloy phase formation during reflow. That is, the lower limit value of the Cu phase thickness after reflow is not regulated, and the thickness may be zero.
The upper limit value of the thickness of the Cu phase is 0.8 μm or less in the state after reflow. 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. A more preferable thickness of the Cu phase is 0.4 μm or less.
In order to obtain the above plating structure, the thickness of each plating at the time of electroplating is adjusted as appropriate within the range of 0.5 to 1.8 μm for Sn plating and 0.1 to 1.2 μm for Cu plating. The reflow treatment is performed under appropriate conditions in the range of ˜600 ° C. and 3 to 30 seconds.

(4-2) Cu / Ni foundation In the case of Cu / Ni foundation plating, a Ni plating layer, a Cu plating layer and a Sn plating layer are sequentially formed on a Cu-Zn-Sn alloy base material by electroplating, and then reflow is performed. Process. By this reflow treatment, the Cu plating reacts with Sn to become a Sn—Cu alloy phase, and the Cu phase disappears. On the other hand, the Ni layer remains almost in the state after electroplating. As a result, the structure of the plating layer becomes Sn phase, Sn—Cu alloy phase, and Ni phase from the surface side.
The thickness of each phase after reflow is
-Sn phase: 0.1-1.5 μm,
Sn-Cu alloy phase: 0.1 to 1.5 μm
・ Ni phase: 0.1-0.8μm
Adjust to the range.
When the Sn phase is less than 0.1 μm, the solder wettability decreases, and when it exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. A more preferable range is 0.2 to 1.0 μm.
Since the Sn—Cu 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 Sn—Cu alloy phase exceeds 1.5 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. A more preferable thickness is 0.5 to 1.2 μm.

The thickness of the Ni phase is 0.1 to 0.8 μm. If the thickness of Ni is less than 0.1 μm, the corrosion resistance and heat resistance of the plating deteriorate. When the thickness of Ni exceeds 0.8 μm, the thermal stress generated inside the plating layer when heated is increased, and the plating peeling is promoted. A more preferable thickness of the Ni phase is 0.1 to 0.3 μm.
In order to obtain the plating structure, the thickness of each plating during electroplating is in the range of 0.5 to 1.8 μm for Sn plating, 0.1 to 0.4 μm for Cu plating, and 0.1 to 0.4 μm for Ni plating. It adjusts suitably in the range of 0.8 micrometer, and performs a reflow process on suitable conditions in the range of 230-600 degreeC and 3 to 30 second.

The manufacturing, plating, and measuring methods employed in the examples of the present invention are shown below.
Using a high frequency induction furnace, 2 kg of electrolytic copper was dissolved in a graphite crucible having an inner diameter of 60 mm and a depth of 200 mm. After covering the molten metal surface with charcoal pieces, a predetermined amount of Zn, Sn and other alloy 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 underlayer reflow Sn plating material and a Cu / Ni underlayer reflow Sn plating material in the following steps. In order to obtain samples with different C concentrations at the plating / matrix interface, the conditions of step 9 were varied.

(Step 1) After heating at 900 ° C. for 3 hours, it was hot-rolled to a thickness of 8 mm.
(Step 2) The oxidized scale on the surface of the hot rolled plate was ground and removed with a grinder.
(Process 3) Cold rolled to a plate thickness of 1.5 mm.
(Step 4) Heating was performed at 400 ° C. for 30 minutes as recrystallization annealing.
(Step 5) Pickling with a 10 mass% sulfuric acid-1 mass% hydrogen peroxide solution and mechanical polishing with # 1200 emery paper were sequentially performed to remove the surface oxide film.
(Step 6) Cold rolling to a plate thickness of 0.5 mm.
(Step 7) Heating was performed at 400 ° C. for 30 minutes as recrystallization annealing.
(Step 8) Pickling with a 10% by mass sulfuric acid-1% by mass hydrogen peroxide solution was performed to remove the surface oxide film.

(Step 9) Cold rolling to a plate thickness of 0.3 mm. The number of passes was two, and the first pass was processed to 0.38 mm, and the second pass was processed to 0.3 mm. In the second pass, a roll whose surface Rz (maximum height roughness) was adjusted to 1.0 μm was used. In the first pass, Rz on the roll surface was changed at four levels of 1, 2, 3, and 4 μm. Further, the kinematic viscosity of the rolling oil (common to the first pass and the second pass) was changed at three levels of 5, 10 and 15 mm ² / s.
(Step 10) Electrolytic degreasing was performed under the following conditions in a alkaline aqueous solution using the sample as a cathode.
Current density: 3 A / dm ² . Degreasing agent: Trademark “Pakuna P105” manufactured by Yuken Industry Co., Ltd. Degreasing agent concentration: 40 g / L. Temperature: 50 ° C. Time 30 seconds. Current density: 3 A / dm ² .
(Step 11) Pickling was performed using a 10% by mass sulfuric acid aqueous solution.

(Step 12) Ni base plating was performed under the following conditions (only in the case of Cu / Ni base).
-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 13) Cu base plating was 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 14) Sn plating was performed under the following conditions.
-Plating bath composition: stannous oxide 41 g / L, phenolsulfonic 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 15) As a reflow treatment, the sample was inserted into a heating furnace adjusted to 400 ° C. and the atmosphere gas to nitrogen (oxygen 1 vol% or less) for 10 seconds and cooled with water.

The following evaluation was performed about the sample produced in this way.
(A) Analysis of component of base material After the plating layer was completely removed by mechanical polishing and chemical etching, the concentrations of Zn, Sn, and other alloy elements were measured by ICP-emission spectroscopy.
(B) Measurement of conductivity of base material After the plating layer was completely removed by mechanical polishing and chemical etching, the conductivity was measured by a four-terminal method.
(C) Strength A specimen No. 13B defined in JIS-Z2201 (2003) was collected in a direction in which the tensile direction was parallel to the rolling direction. Using this test piece, a tensile test was conducted according to JIS-Z2241 (2003) to determine the tensile strength. This measurement was performed with plating.
(D) Bending workability Using a strip-shaped sample having a width of 10 mm, in accordance with JIS Z 2248, Good Way (direction in which the bending axis is perpendicular to the rolling direction) and Bad Way (direction in which the bending axis is parallel to the rolling direction) The 180 degree adhesion bending test was conducted. About the sample after a bending, the presence or absence of a crack was observed from the surface and cross section of the bending part, and when the crack was not recognized, it determined with 180 degree | times contact | adherence bending.
(E) Plating thickness measurement by electrolytic membrane pressure gauge The thickness of the Sn phase and the Sn—Cu alloy phase was measured on the sample after reflow. Note that the thickness of the Cu phase and Ni phase cannot be measured by this method.

(F) Surface analysis by GDS After the reflowed sample was ultrasonically degreased in acetone, the concentration profile of Sn, Cu, Ni, and C in the depth direction was determined by GDS (glow discharge emission spectroscopic analyzer). The measurement conditions are as follows.
Apparatus: JY5000RF-PSS type manufactured by JOBIN YBON.
-Current Method Program: CNBintel-12aa-0.
Mode: Constant EleCtriC Power = 40W.
Ar-Presser: 775 Pa.
-Current Value: 40 mA (700 V).
-Flush Time: 20 sec.
Preburn Time: 2 sec.
Determination Time: Analysis Time = 30 sec, Sampling Time = 0.020 sec / point.

From the C concentration profile data obtained by GDS, the C concentration at the plating / base metal interface was determined. As a typical concentration profile of C, FIG. 2 shows data of Invention Example 2 (Table 1, Cu base plating material) described later. A peak of C is observed at a depth of 1.6 μm (a boundary surface between the plating layer and the base material). The peak height was read and used as the C concentration at the plating / base metal interface.
Further, from the Cu concentration profile, the thickness of the Cu base plating (Cu phase) remaining after the reflow was obtained. FIG. 3 shows data of Invention Example 24 (Table 2, Cu base plating) described later. A layer having a Cu concentration higher than that of the base material is observed at a depth of 1.7 μm. This layer is the Cu base plating remaining after the reflow, and the thickness of the portion where the Cu concentration is higher than that of the base material is read as the thickness of the Cu phase. In addition, when the layer whose Cu is higher than a base material was not recognized, it was considered that Cu undercoat disappeared (the thickness of Cu phase was zero). Similarly, the thickness of the Ni base plating (Ni phase) was determined from the Ni concentration profile data.

(G) Heat-resistant peelability A strip test piece having a width of 10 mm was collected and heated at a temperature of 160 ° C. in the air for up to 3000 hours. In the meantime, the sample was taken out from the heating furnace every 100 hours, and 90 ° bending and bending back with a bending radius of 0.5 mm were performed (90 ° bending was reciprocated once). Next, an adhesive tape (# 851 manufactured by 3M) was applied to the surface of the inner periphery of the bend and peeled off. Thereafter, the surface of the inner periphery of the sample was observed with an optical microscope (magnification 50 times), and the presence or absence of plating peeling was examined.

Relationship between C concentration of plating layer / base material interface and heat-resistant peelability (Invention Examples 1 to 21 and Comparative Examples 1 to 9)
Table 1 shows an example in which the influence of the C concentration at the plating layer / base metal interface on the heat-resistant peelability was investigated. In Step 9, the C concentration of the plating layer / base material interface is changed by adjusting the Rz and rolling oil dynamic viscosity of the roll surface to 1 to 4 μm and 5 to 15 mm ² / s, respectively.
For the Cu base plating material, electroplating was performed with a Cu thickness of 0.3 μm and a Sn thickness of 1.0 μm, and after reflowing at 400 ° C. for 10 seconds, all the inventive examples and comparative examples were Sn phase. The thickness was about 0.6 μm, the thickness of the Cu—Sn alloy phase was about 1 μm, and the Cu phase disappeared.
For the Cu / Ni base plating material, electroplating was performed with a Ni thickness of 0.2 μm, a Cu thickness of 0.3 μm, and a Sn thickness of 0.8 μm, and reflowed at 400 ° C. for 10 seconds. In both examples and comparative examples, the thickness of the Sn phase is about 0.4 μm, the thickness of the Cu—Sn alloy phase is about 1 μm, the Cu phase disappears, and the Ni phase remains at the thickness during electrodeposition (0.2 μm). It remained.
In any of the alloys shown in Table 1, 180 degree adhesion bending of Good Way and Bad Way was possible.
In Invention Examples 1 to 21, which are the alloys of the present invention, the C concentration at the plating layer / base metal interface is 0.10% by mass or less, and plating peeling does not occur even when heated at 160 ° C. for 3000 hours. On the other hand, in Comparative Examples 1-7, C density | concentration exceeds 0.10 mass% and peeling time is less than 3000 hours. It can also be seen that the C concentration at the plating layer / base metal interface can be lowered by reducing the surface roughness of the rolling roll and lowering the viscosity of the rolling oil. In Comparative Example 8, Zn was less than 2.0% by mass, and in Comparative Example 9, Sn was more than 1.0% by mass, so that the peeling time was notwithstanding that the C concentration was 0.10% by mass or less. Is less than 3000 hours.

表中の「−」は無添加を表す。

"-" In the table represents no addition.

Relationship between plating thickness and heat-resistant peelability (Invention Examples 22 to 36 and Comparative Examples 10 to 15)
Tables 2 and 3 show examples in which the influence of the plating thickness on the heat-resistant peelability was investigated. The composition of the base material is Cu-8.0 mass% Zn-0.3 mass% Sn, the electrical conductivity is 40.7% IACS, the tensile strength is 503 MPa, both Good Way and Bad Way are 180 degree adhesion bending Was possible. In Step 9, a rolling roll having an Rz of 2 μm in the first pass was used, and a rolling oil having a kinematic viscosity of 10 mm ² / s was used in the first pass and the second pass. As a result, the C concentration at the plating layer / base material interface in each sample was within the range of 0.07 to 0.09 mass%.
Table 2 (Invention Examples 22 to 29 and Comparative Examples 10 to 12) shows data for Cu base plating. With respect to Invention Examples 22 to 29 which are the alloys of the present invention, plating peeling does not occur even when heated at 160 ° C. for 3000 hours.
In Invention Examples 22 to 25 and Comparative Example 12, the Sn electrodeposition thickness is 0.9 μm and the thickness of the Cu base is changed. In Comparative Example 12 in which the Cu underlayer thickness after reflow exceeds 0.8 μm, the peeling time is less than 3000 hours.
In Invention Examples 24, 26 to 29 and Comparative Examples 10 to 11, the electrodeposition thickness of the Cu base was 0.8 μm, and the Sn thickness was changed. In Comparative Example 10 in which the Sn electrodeposition thickness was 2.0 μm and reflow was performed under the same conditions as the others, the thickness of the Sn phase after reflow exceeded 1.5 μm. In Comparative Example 11 in which the Sn electrodeposition thickness was 2.0 μm and the reflow time was extended, the Sn—Cu alloy phase thickness after reflow exceeded 1.5 μm. In these alloys in which the thickness of the Sn phase or the Sn—Cu alloy phase exceeds the specified range, the peeling time is less than 3000 hours.

Table 3 (Invention Examples 30 to 36 and Comparative Examples 13 to 15) shows data in the Cu / Ni base plating. With respect to Invention Examples 30 to 36, which are the alloys of the present invention, plating peeling does not occur even when heated for 3000 hours.
In Invention Examples 30 to 32 and Comparative Example 15, the electrodeposition thickness of Sn is 0.9 μm, the electrodeposition thickness of Cu is 0.2 μm, and the thickness of the Ni base is changed. In Comparative Example 15 in which the thickness of the Ni phase after reflow exceeded 0.8 μm, the peeling time was less than 3000 hours.
In Invention Examples 33 to 36 and Comparative Example 13, the electrodeposition thickness of the Cu base was 0.15 μm, the electrodeposition thickness of the Ni base was 0.2 μm, and the Sn thickness was changed. In Comparative Example 13 in which the thickness of the Sn phase after reflow exceeded 1.5 μm, the peeling time was less than 3000 hours.
In Comparative Example 14 in which the Sn electrodeposition thickness was 2.0 μm, the Cu electrodeposition thickness was 0.6 μm, and the reflow time was extended from the other examples, the Sn—Cu alloy phase thickness exceeded 1.5 μm, and peeling The time is less than 3000 hours.

It is a schematic diagram which shows the process in which rolling oil is enclosed by the to-be-rolled material surface during cold rolling. It is the profile of the depth direction of C density | concentration of the sample of invention example 2 (Table 1, Cu base plating). It is the profile of the depth direction of Cu and Sn density | concentration of the sample of invention example 24 (Table 2, Cu base plating).

Claims (3)

2 to 12% by mass of Zn and 0.1 to 1.0% by mass of Sn, the relationship between the Sn mass% concentration ([% Sn]) and the Zn mass% concentration ([% Zn])
0.6 ≦ [% Sn] +0.16 [% Zn] ≦ 2.0
The plating film is composed of the Sn phase, Sn-Cu alloy phase, and Cu phase layers from the surface to the base material. The Sn phase has a thickness of 0.1 to 1.5 μm, the Sn—Cu alloy phase has a thickness of 0.1 to 1.5 μm, and the Cu phase has a thickness of 0 to 0.8 μm. A Cu—Zn—Sn alloy tin-plated strip having a C concentration of 0.10% by mass or less at the interface. 2 to 12% by mass of Zn and 0.1 to 1.0% by mass of Sn, the relationship between the Sn mass% concentration ([% Sn]) and the Zn mass% concentration ([% Zn])
0.6 ≦ [% Sn] +0.16 [% Zn] ≦ 2.0
The plating film is composed of the Sn phase, Sn-Cu alloy phase, and Ni phase layers from the surface to the base material. The thickness of the Sn phase is 0.1 to 1.5 μm, the thickness of the Sn—Cu alloy phase is 0.1 to 1.5 μm, the thickness of the Ni phase is 0.1 to 0.8 μm, the plating layer and the base material Cu-Zn-Sn alloy tin-plated strips, characterized in that the C concentration at the boundary surface between the two is 0.10% by mass or less. The Cu- of claim 1 or 2 , wherein the base material further contains at least one of Ni, Fe, Mn, Co, Ti, Cr, Zr, Al, and Ag in a range of 0.005 to 0.5 mass%. Zn-Sn alloy tin plating strip.

Images