DDR 器件高温环境失效分析

眼图扫描，分析是否高温环境下变差（常温不出错，和常温比较），眼图差异不多。分析derate是否enable，高温下refresh需增多。

高温下阻抗增加，cell 电荷损失加快。

1, Try to double refresh frequency (reduce refresh interval) and see if failure rate changed, because high temperature needs more refresh count.

2, Try to increase drive strength (reduce DS resistor value) and see if failure rate change, because high temperature increases the resistor.

3, Try to reduce ODT (reduce ODT resistor value) and see if failure rate change, because high temperature increases the resistor.

Please notice that controller side DQ drive strength and DRAM side DQ ODT affect write operation, DRAM side DQ drive strength and controller side ODT affect read operation; and CA bus controller side drive strength and DRAM side CA ODT will affect all operations (but might not be a single bit error).

4, Solder ball is not melted enough will also see single bit error, because high temperature increases the resistor of solder ball.