Browse Prior Art Database

2X Wash of Swage Balls

IP.com Disclosure Number: IPCOM000118909D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Nagarajan, R: AUTHOR [+2]

Abstract

In Hard Disk Drive (HDD) manufacture, aluminum oxide (alumina) was identified as the predominant cause of hard-particle related Thermal Asperity (TA) and hard error fails. More detailed microprobe analysis of the TA sites revealed that nearly 90% of the alumina particles found at these sites also showed traces of tungsten and sulfur. An investigation of sources of these contaminants in HDD and Head Stack Assembly (HSA) manufacturer zeroed in on the swage operation in HSA as the culprit. Stainless-steel swage balls in use at the time were manufactured in the following sequence: balls were degreased, then blasted with an abrasive slurry containing alumina in order to remove surface oxides and to roughen the surface.

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This is the abbreviated version, containing approximately 52% of the total text.

2X Wash of Swage Balls

      In Hard Disk Drive (HDD) manufacture, aluminum oxide (alumina)
was identified as the predominant cause of hard-particle related
Thermal Asperity (TA) and hard error fails.  More detailed microprobe
analysis of the TA sites revealed that nearly 90% of the alumina
particles found at  these sites also showed traces of tungsten and
sulfur.  An investigation  of sources of these contaminants in HDD
and Head Stack Assembly (HSA) manufacturer zeroed in on the swage
operation in HSA as the culprit.  Stainless-steel swage balls in use
at the time were manufactured in the following sequence:  balls were
degreased, then blasted with an abrasive slurry containing alumina in
order to remove surface oxides and to roughen the surface.  A rough
surface is necessary  in order to get the dry-film solid lubricant,
tungsten disulfide, to stick uniformly and strongly to the balls
during the deposition process.  Lubricated balls were then shipped in
an unwashed state for use  in the swage operation.  During swage,
excess tungsten disulfide and loose alumina were transferred to the
swage hole and, hence, during operation of the drive, to the
head-disk interface.  Described is a cleaning procedure implemented
to successfully reduce these contaminants  by an order-of-magnitude.

      The process of lubricating is comprised of the following
sequence of steps:  After alumina-blasting, the balls are washed in
an ultrasonic bath using IsoPropyl Alcohol (IPA) as the medium.  This
cleaning step reduces residual alumina particles very effectively.
Subsequent to application of tungsten disulfide, the coated  balls
are rewashed using the same method to remove excess coating material
and to remove more loosened alumina particles.  The net result  of
this '2X' washing process was a reduction in free alumina and free
tungsten disulfide by a factor of about 250.  Compared to unwashed
swage balls in prior art processes, products...