Tensile Test of Fine Wires

Fine wires are widely employed in the microelectronic industry. These wires are most commonly used for forming interconnections between ICs (integrated circuit) and PCBs (printed circuit boards). Most interconnection wires today are less than 50µm in diameter and the mechanical characteristics of these wires are crucial in ensuring proper functioning and reliability of the semiconductor device.

Tensile tests are often conducted to evaluate the wire’s tensile strength, yield strength, and elongation. When testing fine wires, it is often challenging to determine the most suitable test configuration. Grips selected should be able to hold the specimen firmly, without causing any specimen slippage or breaks near the jaws. Since these wires are usually very delicate, clamping pressure and closing speed of the grips must be carefully controlled to prevent any premature failure. Some users attach the test specimen to an aperture card prior to inserting the specimen into the grips. These aperture cards allows for better specimen alignment and easier insertion of specimens into the grips.

A tensile test was conducted on 20µm diameter wire using our table model electromechanical machine, together with custom 10 N pneumatic side acting grips and Bluehill® Software. The wire specimen was attached to an aperture card and clamped by the grips. The two vertical sections of the aperture card were then cut before starting the test. As the load readings are very low, it is recommended to use a load cell of capacity 10 N or lower. To maximize the working range of the load cell, it is best that the weight the grip does not exceed 50% of the load cell capacity. Our custom pneumatic grips are lightweight and the jaw faces feature a special coating to minimize slippage and breaks within the jaw faces. The low load readings also imply that the test results are highly sensitive to surrounding conditions. For this reason, to obtain accurate results, it is critical that the test area be free of external sources of error such as vibration and wind.