| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系 === 90 === Lead-free solders are replacing traditional SnPb solders gradually due to environmental concern in microelectronic packaging industry. In most lead-free solders, tin is the richest element and weighs over 95% of the solders. Therefore, tin whisker growth driven by electrical currents would be one of the most crucial reliability issues in lead-free microelectronic packaging.
Blech structure is used to investigate the electromigration effect in pure tin, in which 5000 Å tin strips are on 700 Å titanium films. Current density of 7.5 ×104 A/cm2 and 1.5 ×105 A/cm2 are applied in the Blech samples. We observed tin whiskers and hillocks on the anode side and voids on the cathode side. The average growth rate of tin whiskers is measured as a function of current density. Also, to investigate temperature effect, samples are stressed at room temperature and 50°C respectively. The average growth rate is about 3 Å/sec at the current densities 1.5 ×105A/cm2 at room temperature, and the rate is 7.7 Å/sec at 50°C. The rate is 0.4 Å/sec at the current densities of 7.5 ×104 A/cm2. The average growth rate of tin whisker as a function of time, current density and temperature are presented in this thesis. The mechanism of tin whisker growth driven by electrical force is discussed.
|
|---|
