For Rigid Disks

Glossary of Disk and Substrate Terms

Purpose The purpose of this glossary is to create common usage and understanding among disk and substrate users and interested groups. This glossary is also useful for training persons entering the disk drive industry.

Scope The scope of the glossary is limited to disks and substrates.

DEFINITIONS

-A- 1. ADHERED GLASS - Small transparent glass particles adhered or fused to the glass surface.

2. ADHESION – Physical attraction or bonding forces at any interface of the disk and substrate structures; may apply to nickel phosphate on aluminum, or any sputtered layer to its substrate.

3. AIRLINE (Glass) - An elongated gaseous inclusion.

4. ALLOY - Name given to metal mixtures composed of several elements. Aluminum alloys use a system of four digits to identify particular compositions, the first digit indicates the alloy group, 5xxx indicates a magnesium bearing aluminum alloy, 6xxx indicates a magnesium and silicon aluminum alloy.

5. AMP-TURNS - Used in the interface process of controlling the coupling of magnetic field to or from a magnetic layer relative to the recording head signal output.

6. ANNEAL – An elevated temperature treatment applied to aluminum or glass substrates or PMR (perpendicular recording) media, at various points in the manufacturing process for the purpose of either stress relief, homogenizing material composition, or achieving a desired material microstructure.

7. ASPERITIES – a protrusion from the surface of a disk or substrate.

8. BLISTER (Glass) - A bubble in glass. May be open at surface and may contain an inclusion.

9. BOUNCE – A dynamic characteristic where the surface morphology reaches a critical condition resulting in unwanted slider disk separation and return. See also Contact/Separation.

10. BOW (Glass) - A term more properly applied to glass tubing; for sheet glass see Warp. Fran to review/update/delete

Update—not for distribution Page 1 of 11 -C- 11. CAMBER (Glass) - A slight convex curve of a surface; for sheet glass see Warp.

12. CARBON OVERCOAT – A thin protective layer applied on the topmost layer of a recording media for corrosion and tribology protection. Can be made of sputter, CVD (chemical vapor deposition), IBC (ion beam carbon), and cathodic arc process.

13. CERTIFICATION – Magnetic defect testing of finished media based on read/write performance.

14. CHECK - A fissure in the glass which does not extend through the thickness of the material.

15. CHEMICAL STRENGTHENING – A process in which the surface compression and bending strength of amorphous glass is increased through a chemical ion-exhange on the surface of the glass. Waiting for committee approval.

16. CHIP - Region of material missing from the surface or edge of a substrate material. This defect does not pass through both sides. See INDENT.

17. CHIP (Glass) - A depression or irregularity on the surface caused by the unintentional removal of glass (as in flaking).

18. CIRCUMFERENTIAL - Points of reference which are equidistant from an axis of rotation.

19. CLEANLINESS - A term used to describe the degree of particulate contamination or foreign material allowable on a part or laboratory environment.

20. CLIP LEVEL – Amplitude level as defined as rejectable defect in glide or magnetic test. Mike Sullivan and/or Jeff Aufderheide to confirm

21. COMET - The visual pattern created by thickness variations in an epoxy media spun on a disk. This pattern occurs if the surface is not perfectly smooth or if a particle of solid material rest on the surface during spinning. TED TO UPDATE

22. CONCAVE - Surface area which has a depression relative to the immediate surrounding area. (ID depressed with respect to OD).

23. CONTACT ANGLE – Consider the drop of a liquid resting on a solid surface. The drop of liquid forming an angle may be considered as resting in equilibrium by balancing the three forces involved. Namely, the interfacial tensions between solid and liquid SL, that between solid and vapor SV, and that between liquid and vapor LV. The angle within the liquid phase is known as the contact angle or wetting angle.

25. CONTACT SEPARATION – Separation of the transducer from the recording medium in a contact recording system. A characteristic (and design parameter) considered for contact head slider/disk interface systems where the static and dynamic repulsive forces (e.g. surface morphology changes, flutter) overcome the static and dynamic attractive forces (e.g. head down force, lubricant meniscus attraction, etc.) reach a critical condition resulting in head slider/disk separation. See also Bounce.

Update—not for distribution Page 2 of 11

26. CONTACT SEPARATION AVALANCHE – The point where the dynamics of the head/disk interface and a combination of surface conditions causes the slider to begin to suffer extremely high levels of contact separation. JEFF to ADD GHA Def’n and combine

27. CONTACT SEPARATION MODULATION – Any periodic variation caused by transducer to medium separation (see also Contact Separation). Contact/Separation Modulation or CSM is a dynamic characteristic of contact recording systems. CSM is unwanted excitation of slider air bearing caused either by variations in disk/substrate topography and/or flutter. CSM measurements are typically made with two high speed, high-resolution measurement systems.

28. CONVEX - The opposite of concave, having a protrusion relative to the surrounding area. (ID protruding with respect to OD).

29. CORD - A narrow inhomogeneous band of glass having a different refractive index than the surrounding glass.

30. CORROSION – The destruction or deterioration of a material because of reaction with its environment.

31. CRACK - A fissure in the glass extending through both surfaces and body of the material.

32. CRUSH (Glass) - A lightly pitted area resulting in a gray appearance, usually the result of the abrasive action of a glass chip between two sheets of glass.

33. CRYSTALLIZED GLASS – Glass that has some degree of crystal structure in an amorphous matrix. FRAN to review

35. DEVITRIFICATION - The process by which glass returns to its non-glassy state. The glass is said to have “devitrified.”

36. DIAMOND TURNED - Micromachining operation using a diamond cutting tool to obtain a microscopic finish.

38. DINGS - Marks left on disk surface due to physical mishandling.

39. DOUBLE DISK GRIND - The process of surface polishing a substrate using two polishing wheels counter rotating.

40. DRAW LINES - A surface irregularity or waviness caused during glass fabrication.

41. DUB-OFF – See Roll-off.

Update—not for distribution Page 3 of 11 42. EDGE-BREAK - The physical deformation which occurs at the edge area when material is cut, sheered and punched. The edge usually has a raised deformation.

43. ELECTROLYTE - A solution that will conduct an electric current. Chemically a compound whose water solution will conduct an electric current. Acids, bases, and salts are electrolytes.

44. ELECTROLYTIC - Chemical action of or having to do with an electrolyte.

-F- 45. FEMTO – A slider form factor with the following dimensions: L=0.85mm, W=0.70mm, T=0.23mm. Slider mass is approximately 0.6mg.

46. FLARE (Glass) - Cutting fin or projection on a score cut edge.

47. FLAT BAKE - The process of clamping a stack of substrates between two massive rigid plates under extreme pressure then subjecting the assembly to an elevated temperature. The assembly is allowed to cool slowly to stress relieve the disks and flatten them after rough machining.

48. FLATNESS – Vertical deviation from a perfect plane over the area of a disk or substrate. Also see Surface Morphology. JEFF TO REVIEW

49. FLUTTER – Flutter is the disk/substrate vibration due to the natural frequency responses of the substrate material to such factors as uneven air flow, spindle vibration and disk imbalance. Higher stiffness to density ratios typically reduces flutter amplitude and increases frequency.

50. FLY AWAY – The condition in a very low fly application where the head suffers a sudden increase in fly height due to disk surface conditions such as nano-waviness, micro-waviness, sudden changes in roughness or other defective characteristics.

51. FLYABILITY – Flyability is the measure of how consistent the head to disk interface is maintained in a dynamic system. It consists of all factors and is a direct measurement of the disk dynamics and the head reaction to the surface.

52. FLY HEIGHT MODULATION – Fly Height Modulation (FHM) is any variation from the nominal fly height of a slider over the disk surface. The amplitude of FHM is a direct response of slider air bearing excitation due to disk/substrate morphology and flutter. FHM measurements are typically made with a high bandwidth, high- resolution instrument with two measurement channels.

-G- 54. GASEOUS INCLUSION - Void in the body of the glass as a result air or reaction gases from the melt becoming trapped in the solidifying glass.

55. GAUSS - The unit of magnetic induction or magnetic flux density in the SI system — equivalent to one maxwell per square centimeter. NOTE: The earth’s magnetic field is approximately 0.3 to 0.5 gauss.

56. GLASS CERAMIC – See Crystallized Glass

Update—not for distribution Page 4 of 11 57. GLIDE HEIGHT – Head fly height at which media has been demonstrated by testing to be free of head/disk contact of a specified amplitude.

58. GLIDE HEIGHT AVALANCHE – Rapid increase of head/disk contact as glide test fly height is lowered.

60. GRIND - A method of material removal using an abrasive stone to achieve desired flatness and thickness dimensions of a substrate.

-H- 61. HARDNESS - The resistance to plastic deformation due to local stress. For disk and substrate applications hardness is normally measured by micro or nano methods allowing thin layer properties to be accurately determined. Hardness is proportional to the dimension of a permanent indentation from a standard indenter applied at a known load. Hardness is of interest for wear properties and resistance to damage.

62. HAZE - The cloudy aspect of a particulate coating or thin film as opposed to a glossy appearance.

63. HAZE (Glass) - A smoky or cloudy film on the surface of the glass, may be either washable or permanent haze.

64. HEAT TREATMENT - The process of raising metal to a high temperature then cooling in a controlled profile. This process will give a known physical property and stabilize the structure.

-I- 65. INCLUSION - A small solid body or a gaseous or liquid substance contained in a crystal or a mineral mass.

67. INTERDIFFUSION - Microscopic intermixing of thin film materials with one another occurring at the boundaries of the films.

68. INTERMETALLICS - Intermediate crystal structures occurring in alloys.

69. ION BEAM – Refers to Ion Beam sputtering or Ion Beam CVD (Chemical Vapor Deposition). High intensity ion beam in high vacuum is used for deposition thin films. It differs from the plasma enhanced sputtering/CVD for thin film deposition.

70. I-50 – Ted to update (or delete)

-K- 71. KNOT (Glass) - An embedded glassy transparent lump having an irregular or tangled appearance. Its size shall be determined by the size of the distorted area.

-L- 72. LAMINATED – a magnetic structure with more than one magnetic layer

73. LANDING ZONE – The area of the disk designed to start and stop the head. See also DDT

Update—not for distribution Page 5 of 11 74. LASER ZONE TEXTURE – Array of small bumps generated by laser to create texture in landing zone.

75. LOOSE GLASS (Glass) - Small glass particles which cling to the main surface of the glass by electrostatic charge or moisture, and can be physically removed without surface damage.

76. LUBE RIPPLES - Periodic thickness variations in a lubricant layer.

-M- 78. MICROWAVINESS – See Surface Morphology. Range between 100 µm < λ<400µm

-N- 81. NANO – 1) A slider form factor with the following dimensions: L=2.00mm, W=1.60mm, T=0.43mm. Slider mass is approximately 5.9mg. 2) Nano is a prefix meaning 10-9. It also refers to devices or measurements on the order of 1X10-9m or 1nm.

82. NANO HARDNESS –(see HARDNESS) Measurement of surface hardness based on depth of indentation of a stylus loaded by a force, typically milinewtons/minute. The indentation should not exceed 20% of the thickness of the layer being measured. Waiting for committee approval

83. NANO INDENTATION - small concave surface feature, whose depth can be measured in nanometers. Waiting for committee approval

84. NANO-SCRATCH – Very fine scratches made by using the stylus of a AFM (Atomic Force Microscope) on the deposited thin films. It is a test of thin film wear resistance.

85. NANO-WAVINESS – See Surface Morphology

86. NICKEL PHOSPHATE – A phosphate layer applied between a substrate and a magnetic thin film.

87. NODULE - Small aggregates or clusters of material protruding from the surface.

88. NON-MAGNETIC NICKEL – Nickel phosphorous layer with sufficient phosphorous to maintain a nonmagnetic amorphous structure throughout disk processing

90. OPEN GASEOUS INCLUSION (Glass) - A gaseous inclusion which so near the surface that it is obviously “open” and/or one so close to the surface that it may be broken open with the point of a soft lead pencil.

Update—not for distribution Page 6 of 11 91. ORANGE PEEL - Refers to the appearance of a substrate surface with small irregularities in coating thickness resembling, an orange peel texture (see also nano- waviness, roughness).

92. ORIENTATION - A term used to describe the process of aligning the magnetic particles of a particulate media in a specific direction. This is done by applying a strong magnetic field to the revolving disk before hardening the epoxy binder to its final setting. Mike Sullivan to update – combine with orientation ratio

-P- 94. PARTICULATE CONTAMINATION – Solid contamination in the form of small particles. The particle size and number of particles per unit volume is used to calculate the level of cleanliness in clean rooms. Typical sizes of particles measured are from 0.3um to 5um in diameter when measured on the disk or substrate.

96. PE/CVD (Plasma Enhanced Chemical Vapor Deposition) – used for deposition of protective carbon overcoats

97. PERMEABILITY (also called Magnetic Permeability) -- a constant of propostionality that exists between magnetic induction and magnetic field intensity.

98. PERPENDICULAR RECORDING – MAJID TO DEFINE

99. PICO – A slider form factor with the following dimensions: L=1.25mm, W=1.00mm, T=0.30mm. Slider mass is approximately 1.6mg.

100. PIEZO-ELECTRIC – A material that generates an electric charge when mechanically deformed. Conversely, when an external electric field is applied to piezoelectric materials they mechanically deform. Piezoelectric material is attached to special heads called glide heads to convert mechanical contacts with media into electrical signal.

101. PIN-ON-DISK – Pin-on-disk denotes the geometry set-up in a common wear test. Typically, a stationary spherical pin is put in contact with the surface of a rotating disk. Often times the frictional force is monitored with strain gages and the surface condition of the interface monitored optically.

102. PIT - A particle of glass having been removed from the glass surface unintentionally.

103. POROSITY - The property of a substance whose atomic structure allows microscopic voids to exist.

104. PULL-OUTS - Microscopic removal of base material either substrate or magnetic layer.

105. PZT – Lead (P) Zirconate (Z) Titanate (T). A common piezoelectric material.

106. REFRACTIVE INDEX – A sensitive measure of the deflection of light wave entering the surface of a material; a sensitive indicator of composition.

Update—not for distribution Page 7 of 11 107. REMNANT (also called Remnant Magnetization) -- the magnetization left behind in a magnetic medium after an external magnetic field is removed.

108. ROLL-OFF – Negative deviation of edge of plane (substrate or media). Can be ID or OD. Can be measured by a variety of optical or stylus tools.

109. ROUGHNESS – See Surface Morphology

110. ROUNDNESS - Describes the transition between a substrate’s surface and edge at either the ID or OD. Also used to describe the circularity of the ID and OD diameters.

111. RUB (Glass) - (Also see Roller Scuff, Scratch and Scuff). A surface scratch or series of small scratches generally caused in handling.

113. SCUFF (Glass) - The marring of the glass surface leaving a milky white, grayish, or matte appearance and having appreciable width as opposed to a scratch.

114. SCRATCH - A single linear abrasion of the glass surface which may be of any length, width or direction.

115. SECTOR - A wedge-shaped portion of a disk’s surface, referred to in error testing.

116. SEED (Glass) - A small elongated bubble. A gaseous inclusion.

117. SHEET - Refers to one method of producing raw stock for the substrate blanks before processing.

118. SHELL - A depression or irregularity on the glass surface.

119. SKI JUMP - That area at the OD of the disk where the surface height increases followed by a sharp drop. This depression area at the OD during plating will cause excessive buildup resulting in a ski jump effect when heads fly over area.

120. SLIDER – Ceramic body of the head whose lower surface forms the air bearing.

121. SLURRY - A compound consisting of a selected abrasive material (i.e. diamond dust, alumina, silica, etc.) suspended in a liquid form used for polishing or texturing.

123. SNELL’S LAW –

124. SNR -

125. SPUTTERING - The process of depositing a target material on the surface of a disk, via discharge of plasma.

126. SQUARENESS –

Update—not for distribution Page 8 of 11 127. SQUEEZE -

128. STAIN (Glass) - Any thin film contaminant of the glass surface, cloudy in appearance, sometimes exhibiting apparent color.

129. STATIC FRICTION –

130. STICK-SLIP –

131. STONE (Glass) - Opaque or partially melted particles of rock, clay or batch material embedded in the glass.

132. STRESS RELIEVING - The reduction of the effects of internal residual stresses in substrate blanks.

133. STRIBECK CURVE –

134. SURFACE ENERGY – (propose to delete)

135. SURFACE MORPHOLOGY – The physical surface characteristics of the disk/substrate morphology are defined in terms of wavelength. The actual upper and lower limits of the wavelength bands of interest are primarily determined by the drive head slider geometry. In general, the following descriptions of surface morphology wavebands are as follows:

Flatness: λ>5mm (NOTE: check symbols) Macro-waviness 2mm < λ<5mm Waviness 400µm < λ<2mm Micro-waviness 100µm < λ<400µm Nano-waviness 50µm < λ<100µm Macro-roughness 25µm < λ<50µm Roughness 15µm < λ<25µm Nano-roughness λ<5µm

-T- 136. TAPER (Glass) - Thickness deviation measured in the direction of drawing sheet glass. This is a total thickness deviation measured over the entire length of the sheet in question. (See wedge for total thickness deviation across the direction of drawing.) (propose to delete)

137. TAPPING MODE -

138. TEMPER - Physical property of metal grain structure obtained by subjecting an alloy to specific thermal treatments. The sequence of letters and digits following an aluminum alloy designation specify the temper. All current aluminum substrates are fully annealed or zero temper.

139. TEXTURE –

Update—not for distribution Page 9 of 11 140. THERMAL ASPERITY -

141. THERMAL EXPANSION - Dimensional increase caused by temperature changes. Each material has its own characteristic coefficient of expansion.

142. THICKNESS DEVIATION, LONG TERM (Glass) - Variation in thickness across a sheet of glass that does not change slope relative to location across the sheet. This long-term thickness deviation is also called Wedge or Taper, depending upon direction of measurement. (propose to delete)

143. THICKNESS DEVIATION, SHORT TERM (Glass) - Variation in thickness across a sheet of glass that changes slope direction or rate relative to location across the sheet. (propose to delete)

144. THICKNESS DEVIATION, TOTAL (Glass) - Maximum thickness minus minimum thickness, within a sheet of glass that changes slope direction or rate relative to location across the sheet. (propose to delete)

145. THIN FILM –

146. TOPOGRAPHY – (propose to reference surface morphology)

147. UHV –

148. VERTICAL RECORDING

149. WALLACE EQUATION –

150. WARP - A large surface irregularity; any deviation from a true plane.

151. WAVINESS – see Surface Morphology.

152. WEAR –

153. WEDGE (Glass) - Departure of the opposite surfaces from parallelism; usually measured in minutes or seconds of arc or in interference fringes per inch. Thickness deviation measured across the direction of drawing sheet glass. This is a total thickness deviation measured over the entire width of the sheet in question. (See taper for total thickness deviation in the direction of drawing.) (propose to delete)

154. WINCHESTER –

155. WORKING DISTANCE - (propose to delete)

Update—not for distribution Page 10 of 11 -Y-

156. YIELD STRENGTH –

157. YOUNG’S MODULUS -

Update—not for distribution Page 11 of 11