The　epoxy(EP)-based　Sn-58Bi　solder　paste　consists　of　a　curable　flux　and　Sn-58Bi　particles.　In　addition　to　its　function　as　a　flux,　the　curable　flux　forms　a　cured　shell　on　the　periphery　of　the　solder　joint.　Under　appropriate　process　parameters,　the　EP-based　Sn-58Bi　solder　paste　can　form　solder　joints　with　a　shell-core　structure　on　the　Cu　substrate.　Compared　to　conventional　Sn-58Bi　solder　paste,　the　solder　joint　of　EP-based　Sn-58Bi　solder　paste　has　a　higher　heat　resistance　and　joint　strength.　To　investigate　the　heat　resistance　of　the　solder　joint　of　EP-based　Sn-58Bi　solder　paste,　the　thermal　cycle　test　was　carried　out　in　the　temperature　range　of　130-170°C.　Metallographic　microscopy　and　scanning　electron　microscopy　(SEM)　were　used　to　observe　the　interfacial　microstructure　of　the　solder　joints　and　to　analyze　the　difference　in　the　microstructure　of　the　solder　joints　in　relation　to　the　thermal　history.　The　results　show　that　the　solder　joint　interface　of　the　EP-based　Sn-58Bi　solder　paste　is　more　stable　than　that　of　the　conventional　Sn-58Bi　solder　paste,　indicating　that　the　cured　EP　shell　on　the　periphery　of　the　solder　joint　can　effectively　improve　the　thermal　stability　of　the　solder　joint.　©　Published　under　licence　by　IOP　Publishing　Ltd.