Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-03-26
2004-03-09
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C029S025350, C029S412000, C029S415000, C029S417000, C156S257000, C156S278000, C427S212000, C427S214000
Reexamination Certificate
active
06703767
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the manufacture of piezoelectric crystals (PZT) and, more particularly, to the processing of PZT wafers to produce peripherally coated PZT crystals that will not contaminate their use environment, such as disk drive suspensions and hard disk drives. In a particular aspect the invention relates to improved methods of coating the PZT crystals, using a resin coating placed between adjacent crystal precursors in a kerf of a predetermined width that permits subsequent cutting of a narrower kerf that leaves the crystal sides coated upon later separation of the crystals from the wafer.
2. Description of the Related Art
PZT crystals are used to effect micromovements of the sliders in disk drives. The crystals may flake in this use environment and introduce contamination into the disk drive. To avoid this efforts have been made to shroud the crystals after their separation from the PZT wafer with plasma sprayed coatings. This is a costly expedient requiring expensive equipment, increased manufacturing time, and repeated handling of the individual crystals.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to provide a less costly solution to the PZT crystal contamination problem. It is a further object to modify the PZT crystal preparation at the wafer cutting level to have a coating formed on the crystal peripheries as a part of the crystal separation steps normally used. It is a further object to provide a wider first kerf between adjacent crystals, fill the first kerf with coating resin, such as epoxy resin, and then cut a second kerf in the first kerf to isolate the crystals with the coating resin adhered to their peripheries.
These and other objects of the invention to become apparent hereinafter are realized in a method for the manufacture of peripherally coated PZT crystals suitable for microactuation of a disk drive suspension from a wafer comprising a plurality of PZT crystal precursors, including cutting in a locus between adjacent precursors a first kerf of a predetermined width to cut apart the precursors and reveal the sides thereof, depositing into the first kerf a coating resin that fills the first kerf and coats the precursor sides, solidifying the coating resin in place, cutting in the solidified coating resin at the locus a second kerf of less width than the first kerf, the second kerf cutting through the coating and between the adjacent precursors in spaced relation to the precursor sides to again cut apart the precursors while maintaining the solidified coating resin in place on the precursor sides, whereby the precursors become PZT crystals having a side coating against flaking of detritus therefrom into a disk drive suspension containing the crystals.
In this and like embodiments, typically, the method further includes cutting the wafer in a grid pattern comprising a series of intersecting first kerfs to define the plurality of crystal precursors, and using as the coating resin a flowable resin that cures to a solid, such as an epoxy resin,
The invention further provides a peripherally coated PZT crystal made by the above method, and more specifically a PZT crystal suitable for microactuation of a disk drive suspension, in which the crystal has on the vertical sides thereof a peripheral coating of a resin applied at a first thickness and cut to a second thickness to block flaking of detritus from the crystal into a disk drive suspension, the coating resin comprising an epoxy resin.
In another aspect the invention provides a wafer comprising a plurality of PZT crystal precursors separated by a first kerf, the first kerf being filled with a coating resin, and in which the first kerf has a second kerf formed therein.
REFERENCES:
patent: 3230402 (1966-01-01), Nightengale et al.
patent: 5305507 (1994-04-01), Dvorsky et al.
patent: 5891595 (1999-04-01), Takeuchi
patent: 6393681 (2002-05-01), Summers
Bachand Louis J.
Magnecomp Corporation
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