Whisker　formation　mechanism　has　been　widely　investigated　for　recent　decades　since　its　great　influence　on　degrading　the　reliability　of　the　electronic　devices.　In　our　work,　effect　of　current　stressing　on　whisker　growth　in　Cu/Sn3.8Ag0.7Cu/Cu　and　Cu/Sn58Bi/Cu　solder　joints　was　investigated.　Results　show　that　after　current　stressing　for　a　long　time,　many　whiskers　are　observed　in　some　local　regions　at　the　cathode　interface.　What　is　most　important　thing　is　that　the　whisker　growth　occurred　at　the　cathode　interface　in　the　crack　region.　These　whiskers　are　all　with　filament-type　morphology,　and　no　column-type　is　formed.　In　general,　they　can　reach　beyond　10μm　in　length.　EDX　reveals　that　these　whiskers　are　mixtures　of　Sn　and　Bi　for　Sn58Bi　solder　and　single　Sn　crystal　for　Sn3.8Ag0.7Cu　solder.　However,　as　the　stressing　time　increases,　the　whiskers　seem　to　stop　growing　any　more.　In　conclusion,　this　filament-type　whisker　growth　at　the　cathode　interface　may　be　responsible　for　the　current　density　accumulation　at　the　crack　region,　leading　to　much　Joule　heat　aggregation　that　triggers　the　whisker　formation.　©　2014　IEEE.