Solder Joint Reliability Enhancement through Surface Mounting Solder Joint Reflow Optimization in Enterprise Grade Solid State Drives (SSDs)

In high reliability Surface Mount Technology (SMT) assembly applications, the ability to inspect the solder joints visually has been standard and has been key factors in providing confidence in solder joint reliability. Inspection techniques such as X-ray can be used to detect gross manufacturing defects such as solder bridging, but are not suitable for detection of other defects such as cracks. Temperature cycling test (TCT) is a standard solder joint reliability assessment method in semiconductor reliability for ball grid array (BGA) packaging. SMT reflow process and CTE (coefficient of thermal expansion) between solder materials, PCB and BGA package have high influence in solder joint reliability. A careful experimental investigation was undertaken to evaluate the reliability of solder joints of SAC BGA components formed using Sn-2Ag-Cu-Ni solder paste. This evaluation specifically looked at the impact of time above liquidus, peak temperature and thermal interface material (TIM) on solder joint reliability. Four types of samples prepared with the peak temperature of 250 degrees C and no TIM, 250 degrees C with TIM, time above liquidus (TAL) 90 seconds and no TIM and TAL 90 seconds with TIM. A total of 60 drives were assembled and subjected to accelerated thermal cycling (ATC) test in the temperature range of 0 degrees C to 100 degrees C for a maximum of 2000 cycles with reference to JESD22-A104 standard. Based on the results from the deisgn of experiment (DOE), TAL 90s profile have demonstrated better TCT reliability margin compared to peak temperature of 250 degrees C.