Edward John Yarmchuk

Spatial structure of media noise in film disks

Measurements of the spatial structure of media noise across the track direction are made using new techniques involving computer processing of digitized transient read signal waveforms. Images of media noise having spatial resolution much finer than available head widths are obtained, and are used to study the scaling of media noise with read head width. Results are presented for two types of metal film disks and a particulate disk. Uniformly DC erased media noise is found to decrease less rapidly with decreasing head width for the metal film disks than for the particulate disk, in which it scales approximately as the square root of head width. A strip of excess noise is found at the edges of written tracks on the metal film disks but not the particulate disk.

A self-servowrite clocking process

A high-speed process for servowriting hard-disk assemblies (HDAs) without an external clock head has been developed. This robust process achieves servo-pattern alignment accuracy comparable to or better than that achieved with conventional clock-head based servowriters at a substantially reduced capital and process cost.

Chains of permeable spheres in an applied magnetic field

A multipole expansion is used to solve for the magnetic field of a chain of permeable spheres. The formalism allows treatment of chains involving spheres of differing radii and at arbitrary spacings along a line. The only restriction on the applied field is that it be curl-free over the volume of interest. We have examined in detail cases involving finite numbers (up to 10) of identical spheres at equal spacings in a uniform applied field. Predictions of the average magnetization of the individual spheres are in good agreement with the values obtained from pickup coil measurements on steel balls. We find that at close spacings (spheres nearly touching) accurate solutions require the inclusion of a large number of terms in the multipole expansion. In such cases, the simple dipole approximation is inadequate.

Thermal Development, Modeling and Characterization of the Cell Processor Module

Optimal package thermal design for todays high power processors is critical to meet demanding performance, cost, and reliability objectives. This paper describes the thermal characterization and development of the first generation CELL processor, developed jointly by Sony, Toshiba and IBM. The package not only provides the very high bandwidth necessary for electrical performance, but also achieves low thermal resistance to dissipate high power and maintain low die temperatures with superior reliability. The focus of the paper is the first level package. The target thermal resistance for the package is explained as determined from detailed 2nd level modeling and novel power map calculation and validation techniques are discussed. Thermal and mechanical modeling are used characterize the effects of the thermal interface material (TIM) on the thermal performance and mechanical response of the package. The thermal test strategy and the TIM characterization techniques are described. In summary, the paper describes the novel thermal modeling and characterization methodology used in the design process, allowing high heat flux in a low cost system application

Latent defect screening for high-reliability glass-ceramic multichip module copper interconnects

Nonlinear electrical conduction effects arising from local heating provide a means for detecting the presence of latent defects that are at risk of becoming open electronic circuits under stress. A special choice of ac drive current results in a dc intermodulation signal produced by nonlinear conduction, and offers several practical advantages over previous techniques involving ac harmonics. A key feature is the use of digital signal processing to provide speed, accuracy, and flexibility of measurement. A manufacturing screening system involving an automated prober integrated with the defect-detection tool is used to test high-performance glass-ceramic substrate interconnects used in advanced microelectronic packaging.

A technique for the measurement of track misregistration in disk files

The authors describe a noninvasive technique for measuring track misregistration (TMR) in disk files using variations in read signal amplitude as an indicator of relative motion between the read head and the written track. The readback signal amplitude from a magnetic recording head can be used as a sensitive linear position transducer for measuring dynamic head-to-track misregistration in disk files. Subtracking the repeatable part of the signal amplitude eliminates virtually all non-TMR related modulation, leaving only small contributions from electronics noise and nonrepeatable fly height fluctuations. These error terms can be measured in isolation by locating the head directly on-track, where sensitivity to TMR vanishes. This technique can provide detailed information about the electromechanical performance of completely assembled and installed disk files. >