| eMMC’s full name is embedded Multimedia Card that the specification is developed by the MMC association, mainly for intelligent terminal products, such as, smartphone. As the storage media of operation system and user data, the failure of eMMC will lead to the collapse of the application system. Therefore, the failure analysis and avoiding of eMMC have great commercial value, which can be contribute to improving of stability and lifetime of hardware system.With the great deal of failure analysis work on JEDEC5.0 eMMC devices, we separate the causes of eMMC failure as two parts, the hardware system abnormity of smartphone and the eMMC monomer failure.For the eMMC failure caused by the abnormity of hardware system, this thesis focused on the abnormity of power system The failure modes and causes had been analysed. And to avoid this kind of failure, innovative method of electric two had been conducted through changing of configuration of PMU registers.In the hardware system of our experiment, DRAM VDD1 and eMMC VCCQ shared the power supply. To keep the running data in DRAM safety when the phone restarted abnormally, the power supply of VDD1 would not be closed. So the VCCQ would not be powered down. Then VCCQ would be powered up prior to CPU when the phone was powered up again, so the eMMC I/O bus powered by VCCQ would be out of control. Therefore the abnormal signals and glitches might be appear in the signal lines of eMMC_CLK and eMMC_CMD, and they would cause the CRC check error of eMMC. By changing the configuration of PMU registers, the method of electric two had been conducted when the abnormal restart happened. The experimental results showed that the power up sequence of hardware system was normal. The abnormal signals and glitches in the signal lines of eMMC_CLK and eMMC_CMD disappeared.For monomer failure analysis of eMMC, this thesis focused on two aspects.(1) Various damage of Nand Flash had been summarized and the detail failure process of eMMC caused by the damage of Nand Flash had also been deduced. To avoid the damage of Nand Flash, manufacturers need to optimize the production and packaging process.(2) We analysed the failure of eMMC caused by Nand Flash interface abnormity and summarized the failure modes and failure causes. Then the ATE selection scheme of Nand Flash had been optimized. For the Nand Flash whose interface rate greater than 400MHz, failure rate decreased about 13ppm and 33pm with the screening rate increase of 10MHz and 30MHz, respectively. The total failure rate was less than 10ppm. So it can eliminate the Nand Flash with abnormal interface effectively.The failure analyses of eMMC in this thesis can be helpful for the project development later. The method to avoid the power up sequence anomaly of hardware system had actually been proved to be effective, which could be used to improve the robustness of the hardware system of smartphone. |
