The　wetting　behavior　of　Sn-9Zn　solder　on　Cu　substrates　with　three　types　of　novel　soldering　fluxes　(Flux1,　Flux2　and　Flux3　as　abbreviation)　and　the　effect　of　fluxes　residues　on　reliability　of　PCB　were　investigated.　Two　methods,　spreading　test　and　wetting　balance　test　were　used　to　estimate　the　wettability　of　Sn-9Zn　solder　on　Cu　substrates.　Flux2　and　Flux3　were　promising　fluxes　for　Sn-9Zn　solder　in　electronic　assembly　due　to　little　corrosion　of　fluxes　residues　and　halide-free　in　their　flux　formulations,　though　Sn-9Zn　solder　exhibited　better　wettability　with　Fluxl　in　two　test　methods.　Surface　insulation　resistance　(SIR)　test　estimated　performance　of　electric　insulation　of　the　fluxes　residues.　Samples　soldered　with　Flux2　and　Flux3　had　higher　SIR　readings　than　Fluxl,　which　indicated　higher　reliability　of　Flux2　and　Flux3.　By　means　of　SEM　and　EDS,　it　was　found　that　serve　corrosion　was　caused　by　the　chloride　residues　of　Flux　1　which　contained　chloride　activators.　©2007　IEEE.