The　wetting　behavior　of　Sn-9Zn　solder　on　Cu　substrates　with　three　types　of　novel　soldering　fluxes　(Flux　1,　Flux　2　and　Flux　3　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.　Flux　2　and　Flux　3　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　Flux　1　in　two　test　methods.　Surface　insulation　resistance　(SIR)　test　estimated　performance　of　electric　insulation　of　the　fluxes　residues.　Samples　soldered　with　Flux　2　and　Flux　3　had　higher　SIR　readings　than　Flux　1,　which　indicated　higher　reliability　of　Flux　2　and　Flux　3.　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.