Effect of additives on mechanical properties of electroplating nickel

Since the additives is necessary for eliminating the residual stress of the nickel structure in MEMS devices, the effect of additives on mechanical properties of electroplating nickel was studied in this paper. Two types of nickel specimens was electroplated in electrolytes with both saccharine and butynediol (type A), and only saccharine (type B), respectively. The test chips were then tested in our tensile system. The average ultimate tensile strength and hardness of type A and type B specimens are 1954MPa and 4.47GPa, 923Mpa and 2.87GPa, respectively; the average elongation of type A, and type B are 7.94% and 12.38%, respectively, when the gauge length is 100μm. The mean grain sizes of type A and type B specimens are about 20nm, 160nm. The results indicates that nickel film fabricated in an electrolyte added by both saccharine and butynediol leads to much more smooth surface, finer nano-grain, and higher ultimate tensile strength-1954Mpa, which is two times of that of another type-923Mpa. The SEM images also show differences in fractography of two types. All the results indicate that additives could affect the mechanical properties dramatically, and it is essential for the designer to consider this effect during the MEMS devices designing process.