Sn　whisker　growth　is　considered　as　a　crucial　reliability　issue　in　the　electronic　packaging　industry,　especially　with　the　massive　application　of　Pb-free　solder　alloys.　In　this　paper,　we　report　our　fundamental　studies　on　Sn　whisker　growth　through　accelerated　tests.　Excessive　rare　earth　element　addition　is　one　way　we　employed　to　investigate　the　kinetics　of　whisker　growth.　Several　aspects　of　the　morphological　features　were　characterized　and　modelled.　The　growth　mechanism　was　clarified　through　observing　the　diffusion　path　of　oxygen　atoms　to　form　rare　earth　oxides.　Our　attempt　to　clarify　the　growth　mechanism　of　the　whiskers　observed　during　electromigration　test　was　be　presented　based　on　the　experimental　efforts　on　the　one-dimensional　joint　specimens.　Such　mechanism　was　investigated　from　a　series　of　comparative　experiments　to　understand　whether　mass　movement　from　electrical　current　or　internal　stresses　from　Joule　heating　induced　diffusion　plays　the　crucial　role　to　form　such　whiskers.