Abstract: Finite element method was used to study the stress distribution in soldered joints of CPGA gull wing lead.Results indicate that the innerside of soldered joint underside is the weakest position where the stress is relatively concentrated,so it is easily to be destroyed.The relationships between different sizes of gull wing lead and the max-stress in soldered joints were calculated and the thermal stress distribution in soldered joints was analyzed with different sizes of gull wing lead experienced alternating thermal effects.Results show that the stress distribution is affected by the size of gull wing lead.With the increasing of lead's thickness,the stress will increase in soldered joints;With the increasing of lead's hight,the stress in soldered joints will increase firstly and then decrease,which has a maximum value.With the increasing of lead's length contacted with solder pad,the stress in soldered joints will decrease firstly and then increase,which has a minimum value.