EP2340318A1

EP2340318A1 - Copper-tin alloy, composite material and use thereof

Info

Publication number: EP2340318A1
Application number: EP09744964A
Authority: EP
Inventors: Michael KÖHLER; Andreas Heide; Ralf Hojda; Udo Riepe
Original assignee: Sundwiger Messingwerk GmbH and Co KG
Current assignee: Sundwiger Messingwerk GmbH and Co KG
Priority date: 2008-10-31
Filing date: 2009-10-27
Publication date: 2011-07-06
Anticipated expiration: 2029-10-27
Also published as: KR20110079638A; CN102177265A; WO2010049118A1; BRPI0921441A2; CN102177265B; US20110206941A1; JP2012506952A; ES2623604T3; RU2482204C2; RU2011121810A; EP2340318B1

Abstract

The invention relates to a copper-tin alloy, comprising 0.2 to 0.8 wt % Sn, 0.1 to 0.6 wt % Ni and / or Co, 0 to 0.05 wt % Zn, 0 to 0.2 wt % Fe, 0.008 to 0.05 wt % P and the remainder Cu. The invention furthermore relates to a corresponding composite material having a base material of such an alloy and to applicable uses thereof. The technological and physical properties are comparable to those of a CuFe2P alloy. However, the alloy according to the invention and a tinned composite material derived herefrom can be easily recycled.

Description

Copper-tin alloy, composite and use

The invention relates to a copper-tin alloy, a composite material with such a copper-tin alloy and a use of the copper-tin alloy and the composite material. The copper-tin alloy and the composite material comprising it are particularly suitable for connection elements in electrical engineering and in electronics. The invention is particularly concerned with the problem of recyclability.

In general, copper alloys based on Cu-Zn, Cu-Sn and Cu-Fe are widely used today for connecting elements in electrical engineering and in electronics. In particular, such copper alloys are used for lead frames and connectors. Important criteria for the selection of materials are modulus of elasticity, yield strength, relaxation behavior and bendability. In addition to a sufficient mechanical strength, the electrical conductivity and the corrosion resistance are important criteria for the reliable function of the components over the lifetime of the overall system. Often there is an overlap of property requirements, which in principle preclude each other, such as the combination a good conductivity with high corrosion resistance. On the other hand, alloying elements in copper, such as nickel and chromium, on the one hand improve the corrosion resistance, on the other hand they considerably reduce the conductivity.

The topic of weldability, in particular laser welding, with other metallic materials is also gaining in importance. Against the backdrop of the exorbitant increase in metal prices in recent years, the subject of recyclability of the alloys used is becoming more and more important. Cu-Zn or brass alloys are solid solution hardening materials. They are binary alloys, which usually contain between 5 and 40 wt .-% of zinc. With increasing zinc content, tensile strength and hardness increase. The elongation reaches a maximum at 30% by weight of zinc. Higher strength and hardness values can only be achieved by cold forming.

For connectors in the form of spring bands, for example, from a

CuZn 30 or a CuZn 37 alloy, a Vickers hardness of Hv = 150 is usually required. In addition, compliance with a minimum bending radius r / s = 1 normalized to the sheet metal thickness must exist for a 90 ° rebate. The disadvantage of the Cu-Zn alloys, however, lies in the relatively poor weldability, because the alloying element zinc has a relatively high vapor pressure. Pure zinc boiling at 1, 013 bar already at 907 ⁰ C. Further, Cu-Zn alloys have a low elastic modulus of about 110 KN / mm ² (Sl unit: GPa) on. In addition, tinned brass bands can not be recycled well due to the tin included for corrosion protection reasons. The relaxation behavior of Cu-Zn alloys is also pronounced, limiting the operating temperature.

Cu-Sn alloys, ie tin bronzes, are among the oldest technically usable copper alloys. The Cu-Sn alloys are usually added some phosphorus, which is why these alloys are also referred to as phosphorus bronzes. The properties of these alloys are determined primarily by the tin content, which is usually between 4 and 8 wt .-%. Depending on the Sn content, the modulus of elasticity of phosphorus bronzes is between 115 and 120 kN / mm ² (SI unit: GPa). The bendability of tin bronzes is excellent. Rising Sn levels improve the flexibility for a given temper. Phosphor bronze tapes can be solidified to a hardness level of Hv = 200 Vickers hardness without problems, and still have a flexibility of r / s = 1 at a bend of

90 ° up. The laser weldability of tin or phosphorus bronzes is given, because these alloys have no volatile elements (especially zinc) and no disturbing second phases. The relaxation behavior of tin or phosphorus bronzes is better than that of brass alloys, although it does not reach the level of thermosetting copper materials.

Cu-Sn alloys are used in the form of bands for stamped parts and connectors, if a good to very good spring characteristic, a good electrical cal and thermal resistance, low stress relaxation, good flexibility, good weldability and solderability are required. Even in tinned form, phosphorus bronzes are easy to recycle. Tin is already included in the alloy as such.

The low-alloyed copper materials include the Cu-Fe alloys. By small additions of iron and phosphorus, the material property of pure copper, e.g. the strength, the softening or relaxation behavior can be improved. In particular, a CuFe2P alloy in the tempering stage FH is widely used for stamped grids in automotive engineering. Of the

Material has a tensile strength of Rm = 420 to 500 N / mm ² (SI unit: MPa) in this tempering stage. The Vickers hardness is Hv = 130 to 150. The sharp-edged bendability is still present. Among the benefits of the CuFe2P alloy is that the modulus of elasticity is about 125 KN / mm ² (GPa) and thus the material has good spring properties. The electrical conductivity is between 60% and 70% IACS (International Annealed Copper Standard: 100% IACS equals about 58 MS / m). A tinning of the material for corrosion protection reasons is well possible.

Among the disadvantages of the CuFe2P alloy is that these are not homogeneous

Material forms, but has Fe2P precipitates. In particular, this makes laser welding difficult. If the laser beam encounters coarser Fe2P precipitates during spot welding, it can be deflected, making the penetration result unsatisfactory. Another disadvantage is the poor recyclability of tinned scraps of CuFe2P-

Alloy. The electrical conductivity of a CuFe2P alloy is reduced by 25% upon reflow by a dissolving tin of about 1% by weight. The tinned punching scrap, which usually make up 50% to 70% of the material used in the manufacture of stamped laths, can not be returned directly to the melting process, but rather must be smelted and electrochemically separated. The return to the material cycle is therefore as a cathode. This process is very energy intensive and thus very expensive compared to the direct melting of the scraps.

From Fig. 1 for a CuFe2P alloy described the influence of a proportion of tin on the electrical conductivity. The electrical conductivity drops drastically even from levels above 0.3 wt .-% tin. If, for example, a 0.4 mm thick band of a CuFe2P alloy of corrosive For protection reasons, coated on both sides with about 3 microns of tin, so would in direct recycling based on this scrape with about 1, 5 wt .-% tin contaminated CuFe2P alloy arise. In addition to drastic losses in the electrical conductivity, this tin content also has a strong negative effect on the solidification behavior.

The object of the invention is to specify an alloy and a composite material whose physical and technological properties are as close as possible to that of a CuFe2P alloy, which are laser-weldable as well as possible and can be readily recycled. Another task is a

Use for such an alloy and to specify such a composite material.

With regard to the alloy, the above object is achieved by a copper-tin alloy having the composition according to claim 1. Accordingly, the copper-tin alloy comprises 0.2 to 0.8% by weight of tin (Sn), 0.1 to 0.6% by weight of nickel (Ni) and / or cobalt (Co), 0 to 0.05% by weight of zinc (Zn), 0 to 0.02% by weight of iron (Fe), 0.008 to 0.05% by weight of phosphorus (P) and the remainder copper (Cu).

The invention is based on the idea of specifying an alternative to the CuFe2P alloy, new alloy, which has comparable properties, but can be easily recycled even in tinned state. Pure Cu-Sn alloys, such as a CuSnO, 15 alloy, undoubtedly have the potential to be used as such an alternative.

Coated with tin, the scrap of such an alloy can be fed directly to the recycling cycle. The mechanical and technological properties correspond to those of a CuFe2P alloy relatively well. Significant weaknesses occur, however, in the softening behavior and the oxidation resistance.

Extensive investigations have now shown that a copper-tin alloy with a specific tuning of the alloying elements tin, nickel and / or cobalt and phosphorus has comparable mechanical and technological properties to a CuFe2P alloy as well as for the respective further processing and end use required property profile in the area of the softening behavior and the relaxation, ie the creep of the component under tension at elevated temperature achieved. It is either Nickel or cobalt with the specified content. In this case, part of the nickel is preferably replaced by cobalt, in which case the sum of the two alloying elements together gives the stated proportion.

A comparison of the technological and physical properties of the given Cu-Sn alloy with a CuFe2P alloy gives the following picture:

It can be seen from the table that the given Cu-Sn alloy meets the specified requirements in terms of technological and physical properties

Properties fulfilled.

When using the specified Cu-Sn alloy in tinned form, an alloy layer forms between the base material and the tin pad. An adaptation of the production facilities is not required when converting to the new material.

In addition, the aforementioned Cu-Sn alloy exhibits a property profile comparable to the CuFe 2 P alloy in the area of the softening behavior and the relaxation. This will be apparent from FIG. There, the relaxation is plotted in percent over the temperature in ⁰ C. The dashed line shows the course of the CuFe2P alloy and the solid line the course of the aforementioned new Cu-Sn alloy. The experiments were for one Load time of 5,000 hours and an initial voltage of 65% Rp 0.2 performed.

The new Cu-Sn alloy is further distinguished by the direct traceability of tin-coated scrap from the individual stages of the value-added chain. The tin-coated scrap can be returned directly to the smelting process, so that the recycling costs are significantly lower than smelting. The smelting costs, for example, can quickly reach the level of manufacturing costs with a scrap content of 70% and put into question the economic efficiency. For this reason, consideration of the metal values between a copper-iron alloy such as the CuFe2P alloy and the Cu-Sn alloy given here does not alter the fact that the alloy given is economically and ecologically (the additional use of electricity and acid for the electrolytic treatment of the scrap can be omitted) represents a useful alternative to tinned copper-iron alloys.

With regard to the required properties, it is advantageous if the stated copper-tin alloy contains a proportion of Sn between 0.3 and 0.7% by weight, in particular between 0.4 and 0.6% by weight , A further advantageous adaptation of the properties can be made if the proportion of Ni and / or Co in the copper-tin alloy between 0.2 and 0.55 wt .-%, in particular between 0.3 and 0.5 wt. -% lies.

By a preferred amount of phosphorus between 0.008 and 0.03 wt .-%, in particular between 0.008 and 0.015 wt -.%, The strength can be improved.

In a preferred alloy composition, the copper-tin alloy has 0.3 to 0.7 wt% Sn, 0.2 to 0.55 wt% Ni and / or Co, 0 to

0.04 wt .-% Zn, 0 to 0.015 wt .-% Fe, 0.08 to 0.03 wt .-% P ₁ and the balance Cu on.

The copper-tin alloy is further improved when it contains 0.4 to 0.6% by weight Sn, 0.3 to 0.5% by weight Ni and / or Co, 0 to 0.03% by weight. % Zn, 0 to 0.01% by weight

% Fe, 0.008 to 0.015 wt .-% P, and the remainder comprises Cu. A further advantageous precise adjustment of the properties of the copper-tin alloy can be carried out if there is a total of impurities and other admixtures of at most 0.3% by weight.

As a concrete embodiment having excellent properties, mention is made of a copper-tin alloy containing 0.38 wt% Sn, 0.30 wt% Ni and / or Co, 0.003 wt% Zn ₁ 0.008 wt%. % Fe, 0.014 wt .-% P, and the remainder comprises Cu.

The new copper-tin alloy is very good laser weldable, since no volatile elements are included and the alloy is free of a second phase. In particular, the alloy does not exhibit NiP precipitates.

The alloy is ideally suited for a good laser-weldable composite material, which can be used in particular for stamped grid. Such

Punching grids are used today, for example, in automotive technology for ABS and ESP systems. For this purpose, a base material of the aforementioned copper-tin alloy is provided with a tin layer or covered, which can be made in particular by the method of hot tinning. In this respect, there is a layer of pure or free tin on the base material of the specified copper-tin alloy. The composite is characterized by a high relaxation resistance up to temperatures of 100 ⁰ C. It has inside the core as the specified copper-tin alloy with a composition in accordance with the then-directed claims on. The outer coating or tin cover ensures high corrosion resistance. The thickness of the tin layer is preferably between 1 and 3 μm.

When tinning the specified copper-tin alloy, a transition layer between the base material and the tin layer is formed. The tin layer is preferably applied in such a way that the transition layer comprises an intermetallic phase of Cu, Ni and / or Co and Sn. The formation of the transition layer is in particular designed such that it has a thickness between 0.1 and 1 micron. In this respect, the composite material in the interior or core of the specified copper-tin alloy with the corresponding proportions of nickel and / or cobalt and phosphorus. The alloy of the core transitions through the transition layer into a layer of pure tin. Via the formed transition or alloy layer, a good connection of the tin layer is achieved.

Considering a three-dimensional structure like a stamped grid made of composite material, the overall result is a five-layer structure. On one core of the specified copper-tin alloy as a base material sits on both sides of a layer of an intermetallic phase, consisting of CuNiCoSn with a thickness between 0.1 and 1, 0 microns. The composite material is finally covered for corrosion protection reasons with a layer of free or pure tin, which has a thickness of 1, 0 to 3.0 microns. The layer composite material has a total thickness of 0.2 to 1 mm, preferably up to 2 mm, particularly preferably up to 3 mm.

The electrical conductivity of the specified composite material corresponds to that of the previously used comparison material CuFe2P. Thermal conductivity and other technological values of the composite are also fully comparable.

Both the specified copper-tin alloy and the tinned composite material is excellent for tapes, foils, profiled strips, stampings or

Connector, in particular for applications in electrical engineering or electronics suitable.

Claims

claims

1. copper-tin alloy comprising: 0.2 to 0.8% by weight of Sn,

0.1 to 0.6% by weight of Ni and / or Co, 0 to 0.05% by weight of Zn, 0 to 0.02% by weight of Fe,

0.008 to 0.05 wt .-% P, and the balance Cu.

2. copper-tin alloy according to claim 1, with a proportion of Sn between 0.3 and 0.7 wt .-%, in particular between 0.4 and 0.6 wt .-%.

3. copper-tin alloy according to claim 1 or 2, with a proportion of Ni and / or Co between 0.2 and 0.55 wt .-%, in particular between 0.3 and 0.5 wt .-% ,

4. Copper-tin alloy according to one of the preceding claims, with a proportion of P between 0.008 and 0.03 wt .-%, in particular between 0.008 and 0.015 wt .-%.

The copper-tin alloy of claim 1, comprising:

0.3 to 0.7% by weight Sn, 0.2 to 0.55% by weight Ni and / or Co, 0 to 0.04% by weight Zn,

0 to 0.015 wt .-% Fe, 0.008 to 0.03 wt .-% P, and the remainder Cu.

A copper-tin alloy according to claim 5, comprising:

0.4 to 0.6% by weight Sn, 0.3 to 0.5% by weight Ni and / or Co, 0 to 0.03% by weight Zn,

0 to 0.01 wt .-% Fe, 0.008 to 0.015 wt -.% P ₁ and the balance Cu.

7. copper-tin alloy according to any one of the preceding claims, with a total of impurities and other admixtures of at most 0.3 wt .-%.

8. Composite material with a base material according to one of the preceding claims and a tin layer applied thereto.

9. The composite material of claim 8, wherein the tin layer has a thickness between 1 and 3 microns.

10. A composite material according to claim 8 or 9, comprising a transition layer between the base material and the tin layer, wherein the transition layer comprises an intermetallic phase of Cu, Ni and / or Co and Sn.

11. A composite according to claim 10, wherein the transition layer has a thickness between 0.1 and 1 micron.

12. Use of a copper-tin alloy according to one of claims 1 to 7 for strips, wires, foils, profiled strips, stamped parts or plug connectors.

13. Use of a composite material according to any one of claims 8 to 11 for tapes, wires, foils, profiled strips, stampings or connectors.