TC Reliability Enhancement Technology for SSD with Low Temperature Solder Paste Material

Abstract

The present study relates to the acquisition of optimal design and reliability enhancement technology using new solder paste material in the development process of new products in order to enter the SSD market with rapid customer response. As SAC paste material is reduced to about 70°C, the customer is able to reduce power and cost, CO2 emissions (35%), and PCB/Substrate warpage 50%. Based on these advantages, customer wants to lead a new industry change and are hoping for the generalization of the application of LTS solder paste material. In general, package causes process failure due to warpage at high and low temperature [1]. Warpage can be reduced by more than 50% from reflow peak temperature of LTS material. However, material bonding technology of SAC ball and LTS material SnBi paste of package is required. It is possible to improve the warpage of SSD set and array by lowering 70°C, but there is a disadvantage that the TAT of the reflow process increases. The SMT reflow profile is mainly managed by dividing it into ramp-up, soak range, and peak temp. In addition, it is necessary to build an additional assembly process line for customer’s LTS paste material application. Various DOE evaluations of peak temp. and duration were performed with the goal of reflow profile optimization. Under the TC 0-125°C conditions of DRAM module products, the reliability was weak due to hot tearing effect in close proximity to melting temp. 138°C of Bi paste. First, BMR 42.1% was confirmed under 180°C and 50sec conditions, and 900cycle defect occurred. Second, to improve this, the duration of the peak temperature section was increased from 50 to 120sec. BMR was confirmed to be 53.8% at 180°C and 120sec, and 1, 200cycle passed. Under the TC -40-85°C conditions of SSD M.2 products, the existing SAC paste failed at 2, 000cycle, but the LTS paste of S/PB material passed at 3, 024cycle and it has been improved by about 50% compared to mass production solder paste.