This paper presents the results of tensile and high cycle fatigue tests for copper thin film. Copper films coated by Sn are often used in various electro devices. Especially, when the film is used in tape carrier package (TCP), the film is repeatedly exposed to mechanical or(and) thermal stresses which results often in the failure of the component. Therefore, to guarantee the reliability of the electrical devices using a film, tensile and fatigue characteristics of the film are important. In this study, to obtain the tensile and fatigue characteristics of the film, the specimen was fabricated by an etching process to make a smooth specimen of 2000 lm width, 8000 lm length and 15.26 lm thickness. The tensile and high cycle fatigue tests were performed with the specimen using the test machine developed by the authors. These specimens had measured values of Young's modulus (72 GPa) and a 0.2 % offset yield and an ultimate strength of 358 MPa and 462 MPa, respectively. A closed-loop feedback control of the magnetic-electric actuator allowed loadcontrolled fatigue tests with 20 Hz frequency, in ambient environment and at two levels of mean stresses. The fatigue strength coefficient and exponent at 0.5 times of the ultimate tensile strength were 431 MPa and -0.0843, respectively. The fatigue strength coefficient and exponent at 0.6 times of the ultimate tensile strength were 371 MPa and -0.0923, respectively. The Goodman method is recommended when the fatigue life of thin film with mean stress will be estimated. The fatigue strength coefficient and exponent of copper thin film modified using Goodman method were 910 MPa and -0.0896, respectively.

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A B S T R A C T Measurements of the mechanical properties of a thin film are strongly influenced by the test procedures. The aim of this paper is to introduce specimen aligning techniques for tensile and fatigue tests with thin films. The calculated modulus for polycrystalline silicon can vary from 100 to 160 GPa according to the alignment condition and reaches a peak at the best alignment as determined from an extensive pre-tensile test. The 'modulus alignment method' is utilized to ensure the specimen alignment before doing tensile and fatigue tests based on the fact that the better the alignment, the higher the modulus. In addition to that, a closed loop control scheme is applied during a fatigue test to maintain the constant load. An S-N curve for polysilicon film is obtained and compared with the results of other researchers. E = Young's modulus L = gauge length of specimen m = Basquin's exponent N f = cycles to failure P = load R = stress ratio, σ min /σ max α = in-plane misalignment angle δ = displacement = engineering strain λ = wave length σ = engineering stress σ f = initial strength σ max = peak/maximum stress

In this study, fatigue tests were performed for NiCo alloy which is commonly used in probe tips of test machines of semiconductors. The smooth specimens were fabricated by MEMS process including electro-plating process on a single-side polished 6 inches (100) silicon wafer. The NiCo thin film consists of about 66.2 % Ni and 33.8 % Co. The specimen is 2000 lm long, 9 lm thick and 100 lm wide. The tests were performed using a novel test procedure, a structure of the specimen is easy to manipulate, align and grip a thin-film and a test machine proposed by the authors. The closed-loop feedback control of the magnetic-electric actuator allowed load-controlled and high cycle fatigue tests with 5 Hz frequency, in ambient environment and with a stress ratio of R = 0.1. The fatigue strength coefficient and exponent were 1324 MPa and -0.0558, respectively. In a fatigue test of thin film, it is difficult to perform the fatigue test at R = -1. However, the result of the fatigue test at R = -1 should be required when fatigue life prediction is performed under variable loading. Therefore, in this study, the modified Goodman method, Gerber method and Soderberg method were considered to investigate which method is most reasonable when mean stress is considered.