Accelerated Lifetime Test for TMR Heads by Ramped Stress

Ramped stress breakdown test was applied to estimate lifetime of tunneling magnetoresistance (TMR) heads for the intrinsic and extrinsic breakdown failure mode based on both E and 1/E models. The ramp voltage stress failure was transferred into the constant voltage stress prediction and closed form expressions of time-to-failure for both E and 1/E models were deduced. The parameters for these expressions were fitted by the experimental data at various ramp step times and the time-to-failure was calculated using these fitted parameters. The heads with larger breakdown voltage showed longer lifetime for the same ramp step time, and the shorter lifetime heads were from the lower magnetic reader resistance range. The thermal acceleration was too slow for TMR lifetime projection, and the lifetime showed bimodal distribution due to the extrinsic and intrinsic breakdown behaviors, the extrinsic breakdown heads showed shorter lifetime compared with the intrinsic breakdown heads.