In　this　paper,　the　tin-lead　(Sn-37wt%Pb)　eutectic　solder　joints　of　plastic　ball　grid　array　(PBGA)　assemblies　are　tested　using　temperature　cycling,　random　vibrations,　and　combined　temperature　cycling　and　vibration　loading　conditions.　The　fatigue　lives,　failure　modes　for　the　solder　joints　and　the　typical　locations　of　the　failed　solder　joints　for　single-variable　loading　and　combined　loading　conditions　are　compared　and　analyzed.　The　results　show　much　earlier　solder　joint　failure　for　combined　loading　than　that　for　either　temperature　cycling　or　pure　vibration　loading　at　room　temperature.　The　primary　failure　mode　is　cracking　within　the　bulk　solder　under　temperature　cycling,　whereas　the　crack　propagation　path　is　along　the　intermetallic　compound　(IMC)　layer　for　vibration　loading.　The　solder　joints　subjected　to　combined　loading　exhibit　both　types　of　failure　modes　observed　for　temperature　cycling　and　vibration　loading;　in　addition,　cracking　through　the　IMC　and　the　bulk　solder　is　observed　in　the　combined　test.　For　temperature　cycling　and　vibration　loading,　the　components　in　the　central　region　of　the　printed　circuit　board　(PCB)　have　more　failed　solder　joints　than　other　components,　whereas　for　combined　loading,　the　number　of　failed　solder　joints　in　the　components　in　different　locations　of　the　PCB　is　approximately　the　same.