Previous　studies　have　indicated　that　silanol　in　the　form　of　polyhedral　oligomeric　silsesquioxane　(POSS)　trisilanol　could　form　strong　bonds　with　solder　matrix　without　agglomeration,　and　inhibit　diffusion　of　metal　atoms　when　subjected　to　high　ambient　temperature　and/or　high　current　density.　Addition　of　POSS-trisilanol　has　also　been　shown　to　improve　the　comprehensive　performance　of　Sn-based　Pb-free　solders,　such　as　shear　strength,　resistance　to　electromigration,　as　well　as　thermal　fatigue.　The　current　study　investigated　the　whisker　formation/growth　behaviors　of　Sn-based　Pb-free　solders　(eutectic　Sn-Bi)　modified　with　3　wt.%　POSS-trisilanol.　Solder　films　on　Cu　substrates　were　aged　at　ambient　temperature　of　125A　degrees　C　to　accelerate　whisker　growth.　The　microstructural　evolution　of　the　solder　films＇　central　and　edge　areas　was　examined　periodically　using　scanning　electron　microscopy.　Bi　whiskers　were　observed　to　extrude　from　the　surface　due　to　stress/strain　relief　during　growth　of　Sn-Cu　intermetallic　compounds　(IMCs).　Addition　of　POSS-trisilanol　was　shown　to　retard　the　growth　of　Bi　whiskers.　The　IMCs　formed　between　POSS-modified　solders　and　the　Cu　substrate　showed　smoother　surface　morphology　and　slower　thickness　growth　rate　during　reflow　and　aging.　It　was　indicated　that　POSS　particles　located　at　the　phase　boundaries　inhibited　diffusion　of　Sn　atoms　at　elevated　temperatures,　and　thus　limited　the　formation　and　growth　of　IMCs,　which　resulted　in　the　observed　inhibition　of　Bi　whisker　growth　in　POSS-modified　solders.