Wear 271 (2011) 604–609 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear The use of surface segmentation methods to characterise laser zone surface structure on hard disc drives Liam Blunt ∗ , Shaojun Xiao Centre for Precision Technologies, School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, United Kingdom article info Article history: Received 29 March 2010 Received in revised form 16 June 2010 Accepted 17 June 2010 Available online 14 July 2010 Keywords: Surface topography Segmentation Structured surfaces Hard disc drives Laser zone texturing Sobel operator morphological analysis abstract All surfaces, be they at the nano-, micro- or even macroscale are made up of a collection of funda- mental features at many different scales which constitute the surface topography. The new generation of so called structured surfaces have features which are organised in deterministic patterns; these include MEMS/NEMS surfaces, micro-fluidic device surfaces and surfaces with repeating features to improve their tribological properties. These types of surface are becoming both technologically and economically critical to high added value manufacturing. The deterministic features on these surfaces include tessellations, rotationally symmetric features and linear features. Surfaces possessing domi- nant deterministic features are considered to have a defined structure and are termed “structured surfaces” where the features are manufactured on the surface in order to give a specific functional response. Surfaces with repeating features are of particular importance to tribological applications and have been designed to have specific contact, lubrication and bearing properties. Identification and of the bound- aries of such features presents particular problems in terms of measurement and characterisation and much recent research has focussed on “segmenting” measured surface data to allow for efficient char- acterisation of functional features. The characterisation methodology is based around extracting and characterising individual elements of the surface and secondly characterising their spatial relationships or pattern. The present paper uses the example of a laser zone textured (LZT) surface used in the landing zones of hard disc drives to illustrate the latest developments in this type of surface metrology. These types of surface are used to “scrape out” or relieve pressure the air bearings of read–write head and park the head effectively and without damage. The feature dimensions and spacing are therefore critical and efficient measurement and characterisation is the critical element in assessing the disc and read–write head functionality and life. © 2010 Elsevier B.V. All rights reserved. 1. Introduction An integral part of all desktop computers, laptop computers, games consoles and some mobile devices is the hard disk drive where programs and data are stored. The hard disk is a metallic or glass disk that is coated with magnetic medium, iron oxide (Fe 3 O 3 ) particles. In hard disk drives used in computers the binary information is written to and read from the disk using a magnetic head referred to as the read–write head. The read–write head passes over the disk surface writing or reading data. Most hard drive systems have multiple rotating platters each with its own read–write head, Fig. 1. Manufacturers of hard disk drives (HDDs) are striving to con- stantly increase the storage capacity without increasing physical ∗ Corresponding author. Tel.: +44 1484 472037; fax: +44 1484 472161. E-mail address: l.a.blunt@hud.ac.uk (L. Blunt). size or the access time to retrieve data. To achieve this requires a number of approaches; increasing the speed of rotation of the plat- ters from the current rotational speeds of 10,000 or 15,000 rpm. Reducing in the area of individual magnetic domains can also increase capacity. This however means that the read–write heads (sliders) must be smaller, so that they can interact with a smaller area on the disk platter. Also, a smaller slider will have a smaller inertia, improving access times. Additionally reducing the flying height of the slider over the disk improves the data storage capacity [1]. The slider does not contact the platter except at rest, when it is parked on a specially textured area on the hard disc referred to as the landing zone. When in motion the slider is supported on an air bearing, generated and maintained by the rotational speed of the platter. The smaller the slider, the closer to the surface it must fly; HDDs currently in production operate with a clearance of approximately 5–20 nm and typically operate under hydrodynamic lubrication. 0043-1648/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2010.06.014