Reliability of Hybrid Supercapacitor for Persistent Memory Application

Abstract

Supercapacitor technology is able to bridge the application gap between chemical batteries and conventional capacitors. Supercapacitors possess a higher energy density than capacitors and a higher power density than electrochemical batteries. The quick charge/discharge ability and long cycle life makes them reliable and applicable where power bursts are required. In efforts to avoid data loss in critical computer applications, such as defense-related, banking, healthcare, etc., persistent memory was created. Persistent memory utilizes backup power from a battery to retain data in Dynamic Random-Access Memory (DRAM) long enough for the data to be transferred to the non-volatile flash in case of a power interruption. To identify failure modes, different reliability tests were performed on the Backup Power Module (BPM): Temperature, Humidity, Bias test, the shelf life test, the cycling test, and the accelerated aging test. From these reliability tests, it was observed that when there is variation in potential across individual cells in the pack, it will accelerate the aging of all the cells connected in series. Also, the cycling test gave an indication of reducing charge/discharge time when cycles were extended beyond the predefined cycle test count. An experimental design is suggested for future work that varies temperatures and voltages, with the response variable being the ability of a supercapacitor to hold charge in a prolonged cycling test. As a result of these reliability assays, it was determined that a major reliability concern was traced to a manufacturing process and a suggestion for the improving a manufacturing step is made.