Furukawa Electric Develops Copper Alloy Strip (EFCUBE-ST) for Ultra-compact Connectors

October 25, 2017

Developed in response to need for smaller connectors in smartphones and tablets

Furukawa Electric Co., Ltd. has developed various copper alloy strips for a range of applications, in its position as a copper material professional. With smartphones, tablets, and other devices becoming increasingly smaller, thinner, and multipolarized, such products require increasingly smaller connectors.

However, this required products to possess contradictory properties—namely, high springing properties and favorable bending workability. It also required favorable elasticity (a low Young's modulus) that resists permanent deformation and high electrical conductivity, in line with the decrease in length and the cross-section area of terminals. Conventional high-strength copper alloys (titanium-copper alloy and beryllium-copper alloy) do not offer sufficient electrical conductivity or elasticity, and also pose issues in terms of costs.

Technology applied to arrange crystal orientation in the same direction

While maintaining high springing properties using a copper alloy (Corson alloy) with a higher concentration of nickel and silicon, Furukawa Electric has applied its proprietary technology to arrange the orientation of crystals inside the alloy in the same direction, resulting in favorable bending workability. Further, the Young's modulus is as low as that of phosphor bronze, providing stable connection pressure and more reliable connectivity. With roughly triple the electrical conductivity of phosphor bronze and titanium-copper alloys combined with high thermal resistance, the product is also ideal for connectors used in batteries and other power source systems loaded with large electrical currents.

Texture control

Mr. Shimada, manager of the Furukawa Electric NIKKO Copper Rolling Plant, had the following to say about future development for this product.

“EFCUBE-ST is an alloy made by precipitation of Ni-Si compounds at a high concentration. The annealing equipment installed in the Copper & High Performance Material Products Division (NIKKO Copper Rolling Plant) boasts the highest achieving temperature in the industry, and this allowed us to develop these innovative copper alloy strips in a way that truly realized texture control technology. We were also able to achieve industry-leading plate thickness accuracy and surface quality using the production technologies we developed for lead frame materials and other products. EFCUBE-ST has been developed to meet the need for more advanced functions than those provided by EFCUBE-820, and is set to help reduce the sizes of thin mobile electronic devices that continue to evolve. “

Comparison of properties with other materials

Numbers represent typical values
Product type		Phosphor bronze （C5240）	Titanium-copper alloy （C1990）	Furukawa Electric developed product EFCUBE-ST
Properties		Phosphor bronze （C5240）	Titanium-copper alloy （C1990）	Furukawa Electric developed product EFCUBE-ST
Electrical property	Conductivity （%IACS）	× 10	× 10	○ 35
Springing property	0.2% yield strength (MPa)	○ 800	○ 900	○ 900
Resistance against permanent deformation	Young's modulus （GPa）	○ 110	× 135	○ 110
Bending workability	MBR^(note) (Width: 1 mm)	× 2t	○ 1t	○ 1t
Thermal resistance	Stress relaxation properties	×	○	○
Costs		◎	×	○

(note) Minimum bendable radius: The minimum bending radius that allows bending without cracks, usually indicated in multiples of plate thickness. The smaller the bendable radius, the better the bending workability.