JP2007254803A - Titanium-copper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide titanium-copper having excellent plating adhesion. <P>SOLUTION: The titanium-copper having excellent plating adhesion can be obtained by adding, by mass, 25 to 500 ppm Al to a copper alloy having a composition comprising 1.0 to 4.5% Ti, and the balance Cu with inevitable impurities. By regulating the Al concentration in the surface of the titanium-copper to 0.05 to 1.0%, its plating adhesion further improves. The titanium-copper may comprise one or more kinds selected from Fe, Sn, Ni, Ag, Mn, Zn and Cr by ≤0.3% in total. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to titanium copper having excellent plating adhesion.

Materials such as various terminals, connectors, relays, and switches of electronic devices are required to have electrical conductivity and springiness. Conventionally, inexpensive brass is used for cost-sensitive applications, phosphor bronze is applied for applications where spring characteristics are important, and white is applied for applications where spring characteristics and corrosion resistance are important. It had been. However, with recent trend toward downsizing and thinning of electronic devices and their components, these materials cannot satisfy the strength, and demand for high-grade spring materials having high strength such as beryllium copper and titanium copper is increasing. .
In the manufacturing process of “titanium copper” typified by JIS-C1990, Ti is solid-dissolved in Cu by solution treatment, cold rolling is performed, and then aging treatment is performed. In this aging treatment, fine particles of Cu ₃ Ti or Cu ₄ Ti are precipitated, and strength characteristics such as proof stress and spring limit value are improved.
Thereafter, the titanium copper strip is pressed and incorporated into electronic components such as connectors, relays, and switches. Usually, the electrical contact portion of the titanium copper strip is plated in a step before or after press working in order to increase the reliability as an electrical contact. Examples of plating include Ni base Au plating and the like.

The research related to conventional titanium copper is mainly aimed at increasing the strength. For example, a technique of adding Ni and Al (Patent Document 1), a technique of adding Al and Mg (Patent Document 2), Cr , Zr, Ni and Fe are added (Patent Document 3). On the other hand, few studies on the plating characteristics of titanium copper strips have been reported.
JP-A-50-53228 JP-A-50-110927 JP 2002-356726 A

The plating material of titanium copper has a drawback that the adhesion strength between the plating layer and the base material (copper alloy strip) is weak compared to a plating material such as phosphor bronze. This difference in adhesion strength is relatively small and has not been a practical problem in the past. However, with the recent miniaturization of electronic components, the contact area between the metal materials in the electrical contact portion has become smaller. As a result, higher electrical reliability (such as more stable contact resistance) has been required due to the electrical characteristics of the contacts, and it has become necessary to improve the titanium copper plating adhesion. The subject of this invention is providing the titanium copper which is excellent in plating adhesiveness.

When the inventors add a small amount of Al to titanium copper and perform aging and subsequent pickling polishing under appropriate conditions, Al segregates at an appropriate concentration on the titanium copper surface, and the plating adhesion is improved. I found.

That is, the present invention
(1) Titanium copper containing 1.0 to 4.5 mass% Ti and 25 to 500 mass ppm Al, the balance being Cu and inevitable impurities, and having excellent plating adhesion,
(2) The titanium copper of (1) above, wherein the Al concentration on the surface is 0.05 to 1.0% by mass,
(3) Titanium copper according to (1) or (2) above, which contains one or more of Fe, Sn, Ni, Ag, Mn, Zn and Cr in a total amount of 0.3% by mass or less,
I will provide a.

  Titanium copper excellent in plating adhesion, which is suitable as a material for various terminals, connectors, relays, switches, etc. of electronic equipment, can be provided.

The reason for limitation of the present invention will be described below.
Ti concentration Ti concentration is adjusted according to the strength and conductivity required of the alloy. When Ti is less than 1.0% by mass, sufficient strength cannot be obtained, and when Ti exceeds 4.5% by mass, the conductivity is remarkably lowered. Therefore, the Ti concentration is 1.0 to 4.5 mass%, preferably 1.5 to 3.5 mass%.
Al concentration Addition of Al to titanium copper improves plating adhesion. When Al is 25 mass ppm or more, the plating adhesion improving effect is exhibited. On the other hand, if the Al content exceeds 500 ppm by mass, the adhesion of the plating is lowered, and the adverse effect of Al on other properties such as conductivity is also caused. Therefore, the Al concentration is specified to be 25 to 500 mass ppm.
A more preferable Al concentration is 50 to 250 ppm by mass. By adjusting Al to 50 ppm or more, the plating adhesion improving effect is further stabilized, and by setting it to 250 ppm or less, the influence of Al on other characteristics is further reduced. A more preferable Al concentration is 50 to 100 ppm by mass.
Although attempts to add Al to titanium copper can also be seen in Patent Documents 1 and 2, etc., the purpose is to increase the strength, and the Al concentration of the alloys disclosed in the examples of these documents is It is higher than the Al concentration proposed by the present invention. That is, conventional research is not a motivation for the present invention.

Surface Al concentration Al in the titanium copper is segregated on the titanium copper surface. The improvement in plating adhesion is due to this segregated Al. Therefore, by controlling the surface segregation state of Al in Al-added titanium copper, good plating adhesion can be obtained more stably. In the present invention, the segregation state of Al is evaluated based on the Al concentration of the surface measured by GDS (Glow Discharge Optical Emission Spectrometer). A preferable surface Al concentration is 0.05 to 1.0 mass%.
Other additive elements Elements other than Ti and Al can be added for high strength. However, if an active element that affects the generation behavior of the oxide film is added, the effect of the present invention is reduced, so the addition of active elements such as Ca, Mg, Zr, P, B, and Si should be avoided. Fe, Sn, Ni, Ag, Mn, Zn, and Cr are effective elements for increasing the strength without inhibiting the effect of improving the plating adhesion by Al. In particular, Fe is an element effective for improving the strength of titanium copper. The total addition amount of these is 0.3% by mass or less. Addition exceeding 0.3% by mass inhibits the effect of improving plating adhesion by Al. A more preferable addition amount is 0.15 to 0.25% by mass. When the total addition amount is 0.15% or more, the strength improvement effect becomes clear, and when the total addition amount is 0.25% by mass or less, good plating adhesion can be obtained more stably.

Hereinafter, embodiments of the invention will be described by way of examples.
In a high-frequency vacuum melting furnace, electrolytic copper was melted and a predetermined amount of Ti, Al and other elements were added, and then the molten metal was cast into a mold to produce an ingot having a thickness of 30 mm, a width of 60 mm, and a length of 120 mm. . Table 1 shows the composition of the ingot. These ingots were processed in the following steps.

(Step 1) After heating at 950 ° 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 sheet thickness of 0.3 mm.
(Step 4) As a solution treatment, the solution was heated in the air at 800 ° C. for 10 seconds and rapidly cooled in water.
(Step 5) As a pickling treatment, the surface was mechanically polished using # 600 emery paper after being immersed in a 30% by mass sulfuric acid-1% by mass aqueous hydrogen peroxide solution for 60 seconds. This mechanical polishing was performed until the fine surface irregularities caused by the corrosion during pickling disappeared and a uniform surface gloss was obtained.
(Step 6) Cold rolling to a plate thickness of 0.2 mm.
(Step 7) As an aging treatment, heating was performed at 420 ° C. for 3 hours using an electric furnace. The atmosphere in the furnace was Ar gas, and the dew point of Ar gas was changed at two levels of −25 ° C. and −10 ° C.
(Step 8) After dipping in a 30% by mass sulfuric acid-1% by mass hydrogen peroxide aqueous solution for 30 seconds as a pickling treatment, the surface was mechanically polished using # 1200 emery paper. This mechanical polishing was performed until the fine surface irregularities caused by corrosion during pickling disappeared and a uniform surface gloss was obtained.
(Step 9) As a pretreatment for plating, electrolytic degreasing was performed using a sample as a cathode in an aqueous alkaline solution, and then immersed in a 10% by mass sulfuric acid aqueous solution for 10 seconds.
(Step 10) Ni base plating with a thickness of 1 μm was applied under the following conditions.
Plating bath composition: nickel sulfate 250 g / L, nickel chloride 45 g / L, boric acid g / L.
Plating bath temperature: 50 ° C. Current density: 5 A / dm ² . Stirring: 5 m / min. Ni plating thickness is adjusted by electrodeposition time.
(Step 11) Au plating with a thickness of 0.2 μm was performed under the following conditions.
Plating bath composition: potassium cyanide 7 g / L, potassium gold cyanide 12 g / L, surfactant 5 g / L.
Plating bath temperature: 60 ° C. Current density: 1 A / dm ² . Stirring: 5 m / min. Au plating thickness is adjusted by electrodeposition time.
About the sample produced in this way, the Al concentration on the surface and the plating adhesion were evaluated.

(1) Surface Al Concentration A sample after the step 8 (pre-plating sample) was ultrasonically degreased in acetone, and then an Al concentration profile was obtained by GDS (glow discharge optical emission spectrometer). FIG. 1 shows data of Invention Example 3 and Comparative Example 1 described later as an example of the Al concentration profile. The measurement conditions are as follows.
-Apparatus: JY5000RF-PSS type made 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 = 30se, Sampling Time = 0.020 sec / point.

(2) Plating adhesion step 11 The plating adhesion was carried out by the following two types of methods specified in JIS H8504 (2005) for the samples that had gone up. The “bending test method” is a method generally used as a plating adhesion evaluation method for copper alloy strips for terminals and connectors, and the “soldering test method” is to meet the recent needs for improving plating adhesion. This is a stricter test method that was newly adopted this time.
(2-1) Bending test method After bending a sample with a width of 10 mm to 90 ° and returning it to the original position (bending radius 0.4 mm, Good Way direction), the bending portion was observed using an optical microscope (magnification 10 times). The presence or absence of plating peeling was determined. The case where plating peeling was not recognized was evaluated as ◯, and the case where plating peeling occurred was evaluated as x.

(2-2) Soldering Test Method A brass Sn plated plate was soldered to the sample surface (Au plated surface), and the brass Sn plated plate was peeled off from the sample surface. In this case, if the plating adhesion of the sample is good, peeling (breakage) occurs in the solder layer, and the peeling surface on the sample side is gray. On the other hand, when the plating adhesion of the sample is insufficient, peeling occurs at the boundary between the plating and the base material (titanium copper), and the peeling surface on the sample side exhibits a copper color.
The peeled surface on the sample side was observed using an optical microscope (magnification 10 times), and the area of the copper-colored portion in the entire area was determined. The case where the area ratio was 5% or less was evaluated as ◯, the case where it was 5 to 30% was evaluated as Δ, and the case where it exceeded 30% was evaluated as ×. In this test, the “surface polishing of the plating surface” described in JIS H8504 was not performed, and the plating surface was only washed with acetone.

The evaluation results of each sample are shown in Table 1. Invention Example No. 1 to 32, 25 to 500 ppm of Al was added, aging was performed in Ar gas having a dew point of −25 ° C., and then pickling and polishing were performed under the above conditions. It was within the range of 0.0 mass%, and good plating adhesion was obtained.

Comparative Examples 1 to 3 correspond to conventional general titanium copper. Al is less than 25 ppm, and the surface Al concentration after pickling and polishing is also as low as 0.01% by mass or less. In these cases, plating peeling did not occur in the bending test method (conventional test method), but plating peeling occurred in the soldering test method (strict test method).

In Comparative Examples 4 to 7, 25 ppm or more of Al was added, but since the dew point of Ar used as an aging atmosphere gas was bad at −10 ° C., the Al concentration on the surface after pickling and polishing was 0.05 mass%. It was not reached. In these cases, slight plating peeling (Δ) occurred in the soldering test method. From this result, although (1) the effect of improving plating adhesion can be obtained only by adding Al to the alloy (comparison with Comparative Examples 1 to 3), in order to stably obtain better plating adhesion, the surface It is understood that control of the Al concentration is also necessary, and (2) it is necessary to suppress surface oxidation during aging in order to effectively concentrate the Al contained in the alloy on the surface. The reason why the surface Al concentration was suppressed was thought to be that the Al concentration in the vicinity of the surface decreased due to oxidation wear during aging.

In Comparative Example 8, in addition to low Al content of less than 25 ppm, aging was performed in Ar gas having a dew point of −10 ° C., and plating peeling occurred in both the bending test method and the soldering test method.
In Comparative Examples 9 to 12, Al exceeded 500 ppm, and the Al concentration on the surface after pickling and polishing exceeded 0.1 mass%, and plating peeling occurred in both the bending test method and the soldering test method. . The plating adhesion of titanium copper added with a large amount of Al for increasing the strength (Patent Documents 1, 2, etc.) corresponds to the level of plating peelability of Comparative Examples 9-12.
In Comparative Example 13, the total addition amount of elements other than Ti and Al exceeded 0.3% by mass, and plating peeling occurred in the soldering test method regardless of the addition of 25 ppm or more of Al.

Comparative Example 14 is the result of evaluating the plating adhesion of phosphor bronze (C5210 defined by JIS H3130). Phosphor bronze shows good plating adhesion even when the Al concentration is low, and it has been shown that improvement of plating adhesion is a problem of titanium copper.

Invention Example No. 3 and Comparative Example No. 1 is the Al concentration profile of the surface in FIG.

Claims (3)

Titanium copper containing 1.0 to 4.5 mass% Ti and 25 to 500 mass ppm Al, the balance being Cu and inevitable impurities, and excellent plating adhesion. The titanium copper according to claim 1, wherein the Al concentration on the surface is 0.05 to 1.0 mass%. The titanium-copper according to claim 1 or 2, wherein the total amount of one or more of Fe, Sn, Ni, Ag, Mn, Zn, and Cr is 0.30 mass% or less.

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