Browse Prior Art Database

High Yield Thin Film Heads

IP.com Disclosure Number: IPCOM000082245D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Parker, JE: AUTHOR

Abstract

The number of usable multielement thin-film heads yielded from manufacture is significantly increased, by providing redundant elements to substitute for defective ones.

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High Yield Thin Film Heads

The number of usable multielement thin-film heads yielded from manufacture is significantly increased, by providing redundant elements to substitute for defective ones.

As the number of elements on a substrate increases, the probability of obtaining a single defect-free substrate decreases. For example, a manufacturing process yielding 98% on a single-element head can be expected to yield about 82% "good" substrates carrying 10 elements, but only 13% for substrates carrying 100 elements. Similarly, a process yielding 85% on a single-element substrate can be expected to yield 20% for 10 elements and 0.0000087% for 100 elements.

If a matching set of elements is provided on a different substrate and the pair of substrates mounted face-to-face in such a way that the corresponding elements are electrically interchangeable, then the effective or combined yield of the double substrate increases because of the low probability of two defects in corresponding pairs of elements. Assuming the same 98% initial single element yield, the new yields become 99.6% for 10 tracks and 96% for 100 tracks. Figuring the individual track yield per substrate as 85%, the 10 element yield becomes 80% and the 100 element yield 10.3%.

In the figure, two sets of inductive elements are deposited on two substrates and mated against a thin center section. Magnetoresistive, Hall or other elements could be used. Defective elements on substrate 1, indicated by X's, are rep...