Immersion　tin　(I-Sn)　coatings　on　copper　were　prepared　in　a　stannous　methanesulfonate　bath　with　thiourea　being　the　potential　altering　agent.　The　electrochemical　displacement　process　was　studied　by　the　galvanic　couple　current　method　(GCCM)　on　an　electrochemical　workstation.　The　morphology　of　the　I-Sn　coatings　were　observed　by　field-emission-gun　scanning　electron　microscopy　(FEG-SEM).　The　I-Sn　process　can　be　divided　into　three　stages:　(i)　rapid　increase　in　galvanic　current,　(ii)　sudden　decrease　in　galvanic　current　after　a　peak　current,　and　(iii)　low　or　residual　galvanic　current　stages.　It　is　demonstrated　that　the　galvanic　current　method　is　a　useful　and　efficient　tool　to　identify　the　optimum　ending　time　of　the　immersion　plating　process.　This　optimum　immersion　time　results　in　a　smooth　and　conformal　deposit　with　a　fine　grain　size.