Thermal Shock Cycles Optimization of Sn-3.0 Ag-0.5 Cu/OSP SolderJoint with Bonding Strength Variation for Electronic Components

Abstract

When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between <TEX>$-40^{\circ}C\;and\;+125^{\circ}C$</TEX> for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and <TEX>$45^{\circ}$</TEX> lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock.