Icko E. T. Iben

Dynamic temperature rise of shielded MR sensors during simulated electrostatic discharge pulses of variable pulse width

The temperature rise from Electrostatic discharge (ESD) of shielded AMR sensors used for magnetic tape storage devices is studied using square wave voltage pulses with widths from 35 ns to 2 ms. A phenomenological model has been developed to describe the dynamic stripe temperature versus pulse width and power for the time range studied as well as for a wide range in sensor geometries. The temperature required to melt the stripes was determined to be 1437 plusmn 69degC. The activation energy required to achieve a 2% increase in stripe resistance for pulses between 100 ns and 1 ms was determined to be 2.8 eV and is associated with interdiffusion of the stripe metals.

Steady-state thermal characteristics of AMR read/write heads used in tape storage drives

Tape storage drives use lithographically deposited anisotropic magnetoresistive (AMR) sensors to read magnetic transitions written on tape. The read-back signal and the reliability of an AMR sensor are both affected by sensor temperature. Because current passes through the sensor, it is subject to joule heating, dependent on both the geometry of the sensor and the thermal conductivities of its material. Because of the resources required to build new sensors, the ability to predict the effects of dimensional changes on sensor temperature is important. This paper describes an analytical model and a three-dimensional finite element analysis (FEA) of the heat transfer for a shielded rectangular-sheet AMR sensor under joule heating over a range of sensor dimensions. The novel analysis consolidates the experimental and FEA data into a few parameters that make it possible to calculate the sensor temperature as a function of power for a wide range of geometries, thus assisting designers who need to set current limitations on the read elements of extant drives and to extrapolate to next-generation drives. We also evaluate the temperature of a sensor and the substrate in a drive, combining the heating from writers and readers. Heat flow away from the head substrate was found to be significantly higher when the tape is moving than when it is stationary, and a simple model is developed to describe the heat dissipation of the substrate as a function of tape velocity.

Head reliability of AMR sensors based on thermal stress tests

Tape storage drives use robust shielded anisotropic magnetoresistive (AMR) read sensors. Under normal operating conditions, changes in sensor properties are undetectable. To estimate end-of-life conditions, sensors are exposed to elevated temperatures, and changes in relevant physical parameters are measured. Then, using thermodynamic models, these measurements are extrapolated to normal operating conditions. Thermal stress experiments using elevated electrical currents for heating were conducted on AMR read sensors designed for use up to about 200 Mb/in.2 in tape storage drives. Physical parameters that are relevant to tape-drive function include stripe resistance, AMR amplitudes and asymmetries, and stripe and shield oxidation. Changes in these parameters were measured as functions of time and temperature. The experimental results were fit to thermodynamic models, which were then used to extrapolate the observed changes to normal operating temperatures and extended times. The data shows that, at the lowest temperatures, the important processes are stripe oxidation and annealing-induced changes in magnetic characteristics. For the materials studied, the projected time-to-failure for use in a drive is greater than ten years.

ESD damage and solutions in tape head manufacturing

Magnetic tape heads use a multiplicity of highly ESD sensitive read sensors. With 36 or more sensors per head in a magnetic storage tape drive, a loss in a manufacturing environment of 1000 ppm per sensor is very costly. ESD damages caused by manufacturing processes, fixtures, material and faulty testers are investigated and reviewed. A new type of ESD failure is revealed in the study. Solutions are suggested to improve and amend the observed problems.

Tunable diode protection for GMR and TMR sensors

TMR and GMR sensors used today are highly susceptible to ESD damage with failure voltages as low as 0.5 V. Diode protection using a single diode connected in parallel with the sensor does not work for many advanced MR sensors due to the fact that the voltage at which diodes begin conducting significant current exceeds the damage voltage of many advanced MR sensors. This is due to limitations of the band gaps of the diode materials (Si and Ge) and the resistance of the diodes while conducting. Here we report several novel diode protection circuits which enable protecting the most sensitive devices while tuning the circuits to the electrical characteristics of the particular sensor being used.

TMR tape drive for a 15 TB cartridge

This paper highlights the development of tunnel magnetoresistive (TMR) sensors for magnetic tape recording applications. This has led to the introduction of a tape drives supporting a 15 TB native tape cartridge, currently the highest capacity available. Underscoring this development is the fact that the TMR sensors must run in continual contact with the tape media. This is contrasted with modern hard disk drive (hdd) sensors, which fly above the disk platters. Various challenges encountered in developing and deploying TMR are presented. In addition, advances to the write transducer are also discussed. Lastly, the authors show that future density scaling for tape recording, unlike that for hdd, is not facing limits imposed by photolithography or superparamagnetic physics, suggesting that cartridge capacity improvements of 4 to 6x will be achieved in the next 4 to 8 years.This paper highlights the development of tunnel magnetoresistive (TMR) sensors for magnetic tape recording applications. This has led to the introduction of a tape drives supporting a 15 TB native tape cartridge, currently the highest capacity available. Underscoring this development is the fact that the TMR sensors must run in continual contact with the tape media. This is contrasted with modern hard disk drive (hdd) sensors, which fly above the disk platters. Various challenges encountered in developing and deploying TMR are presented. In addition, advances to the write transducer are also discussed. Lastly, the authors show that future density scaling for tape recording, unlike that for hdd, is not facing limits imposed by photolithography or superparamagnetic physics, suggesting that cartridge capacity improvements of 4 to 6x will be achieved in the next 4 to 8 years.

EMI generated EOS in a wire-bonder

Wire-bonding equipment is essential to modern electronics manufacturing lines. Equipment, such as motors, either from components within or external to the wire-bonder can generate EMI. This is a study of EMI on a wire-bonder, determining the EOS levels, the potential for damage to sensitive electronics devices and means of eliminating the unwanted EMI.