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IDEMA STANDARDS
Disks and Substrates Document No. D18-96
GLOSSARY OF DISK/SUBSTRATE TERMS
PURPOSE: The purpose of this glossary is to create common usage and understanding among disk and substrate uses and interested groups. This glossary is also useful for training persons entering the disk drive industry.
SCOPE: The scope of this glossary is limited to disks and substrates.
REFERENCED STANDARDS: IDEMA D2-91, Specification for Substrates for Rigid Disks.
DEFINITIONS
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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1. ADHERED GLASS - Small transparent glass
particles adhered or fused to the glass surface.
2. AIRLINE (Glass) - An elongated gaseous
inclusion.
3. 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.
4. 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.
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5. BLISTER (Glass) - A bubble in glass
greater than .030" in length. A gaseous inclusion. May
be open at surface.
6. BOW - The measure of curvature relative
to a perfectly flat disk. MILS or MICROINCHES per linear
distance are its units.
7. BOW (Glass) - A term more properly applied to glass tubing;
for sheet glass see Warp.
8. BREAK-THROUGH - The physical void of material between two
holes or adjacent voids.
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9. CAMBER (Glass) - A slight convex curve
of a surface; for sheet glass see Warp.
10. CHECK - A fissure in the glass which
does not extend through the thickness of the material.
11. CHIP - Region of material missing from
the surface or edge of a substrate material. This defect
does not pass through both sides. See — INDENT.
12. CHIP (Glass) - A depression or irregularity
on the surface caused by the unintentional removal of glass
(as in flaking).
13. CIRCUMFERENTIAL - Points of reference
which are equidistant from an axis of rotation.
14. CIRCUMFERENTIAL LINES - Visual circular
lines (scratches) on the surface of the substrate after the
final finish.
15. CLEANLINESS - A term used to describe
the degree of particulate contamination or foreign material
allowable on a part or laboratory environment.
16. 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.
17. CONCAVE - Surface area which has a depression relative to
the immediate surrounding area.
(ID depressed with respect to OD).
18. CONVEX - The opposite of concave, having a protrusion relative
to the surrounding area.
(ID protruding with respect to OD).
19. CORD - A narrow inhomogeneous band of glass having a different
refractive index than the surrounding glass.
20. CORROSION - Destructive chemical deterioration of a metal
by reaction with its environment.
Corrosion in disks occurs at thin film interfaces (substrate to thin film, thin
film to thin film or thin
film to environment).
21. CRACK - A fissure in the glass extending through both surfaces
and body of the material.
22. 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.
23. CUT-OFF - The term given the length of a sinewave whose amplitude
is transmitted with 75% of its actual
height. The selection of a cut-off length determines which feature of the profile
is regarded as roughness
and therefore constitutes thoroughness profile.
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24. DEFECT, PROTRUDING - Asperities, particles,
contamination, or foreign debris above the surface of substrates.
25. DEVITRIFICATION - The process by which
glass returns to its non-glassy state. The glass is said
to have “devitrified.”
26. DIAMOND TURNED - Micromachining operation
using a diamond cutting tool to obtain a microscopic finish.
27. DIGS - Pulled out surface micro-structure
caused by burnishing, polishing or other process machining.
28. DINGS - Marks left on disk surface
due to physical mishandling.
29. DIRT (Glass) - Foreign material which
contaminates the glass surface.
30. DOUBLE DISK GRIND - The process of
surface polishing a substrate using two polishing wheels
counter rotating.
31. DRAW LINES - A surface irregularity
or waviness caused during glass fabrication.
32. DUB-OFF - A lesser degree of chamfer,
slight rounding of the intersection of two surfaces.
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33. 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.
34. 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.
35. ELECTROLYTIC - Chemical action of
or having to do with an electrolyte.
36. EPOXY COATING - Pertains to the magnetic
layer spun on top of a substrate. Epoxy coating describes
the polymeric material in which the magnetic particles
and alumina are suspended.
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37. FLARE (Glass) - Cutting fin or projection
on a score cut edge.
38. 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.
39. FLY-CUT - Machinist term of process
used to cut the substrate blanks to rough dimension.
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40. 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.
41. 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
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42. HARDNESS - The resistance to plastic
deformation of a locally stressed substance. The hardness
of metals is called out as BRINELL or a ROCKWELL hardness
number representing different measurement methods by permanent
impression in the material made by an indenter. Higher numbers
represent higher resistance of the surface to indentation
by inference to wear or abrasion.
43. HAZE - The cloudy aspect of a particulate
coating or thin film as opposed to a glossy appearance.
44. HAZE (Glass) - A smoky or cloudy film
on the surface of the glass, may be either washable or
permanent haze.
45. 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.
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46. INCLUSION - A small solid body or a
gaseous or liquid substance contained in a crystal or a mineral
mass.
47. INTERDIFFUSION - Microscopic intermixing
of thin film materials with one another occurring at the
boundaries of the films.
48. INTERMETALLICS - Intermediate crystal
structures occurring in alloys.
49. IRON OXIDE - The most common magnetic
constituent of a particulate magnetic coating.
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50. 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.
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51. 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.
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52. MEDIA, ELECTROLESS - Magnetic media
deposited by immersion in a chemical bath without recourse
to an external electrical source.
53. MEDIA, ELECTRON-BEAM EVAPORATION -
Magnetic layer deposited by vacuum process in which an
electron-beam is used as a heat source to evaporate the
magnetic material.
54. MEDIA, ELECTROPLATED - Magnetic layer
deposited by immersion in a chemical bath using the passage
of electric current to transport the metallic ions.
55. MEDIA, EVAPORATED - Magnetic layer
deposited by a process in which the magnetic layer is evaporated
in a vacuum chamber. The metallic vapor condenses on the
disk to form the thin magnetic film.
56. MEDIA, PHYSICAL DEPOSITION - Magnetic
layer deposited by a vacuum process such as sputtering
or ion beam i.e. involving ionic or molecular bombardment
in a plasma.
57. MEDIA, THERMAL EVAPORATION - Magnetic
layer deposited by vacuum process in which the metal to
be deposited is heated to the evaporation point by a filament
carrying a heavy current, by R.F. (Radio Frequency) induction
or by electron bombardment.
58. MEDIA, VAPOR DEPOSITION - Magnetic
layer deposited by a vacuum process where the magnetic
material is thermally evaporated than condensed on the
surface of a disk. See media evaporated.
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59. NODULE - Small aggregates or clusters
of material protruding from the surface.
60. NON-MAGNETIC NICKEL - A sub-layer
applied between a substrate and a magnetic thin film.
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61. 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.
62. ORANGE PEEL - Refers to the appearance
of an epoxy coated disk with small irregularities in coating
thickness resembling, an orange peel texture.
63. 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.
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64. PATTERNING - Visual effect or reflection
of surface texture when light is used to inspect disk for
surface flaws. EXAMPLE - Particulate media greenish bands
due to orientation.
65. PIT - A particle of glass having been
removed from the glass surface unintentionally.
66. POROSITY - The property of a substance
whose atomic structure allows microscopic voids to exist.
67. PULL-OUTS - The removal of weakly
bound microscopic agglomerates of material occurring in
a lapping or polishing operation.
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68. RELUCTANCE - The resistance offered
to the passage of magnetic lines of force. It is equivalent
to the ratio of the magneto-motive force to the magnetic
flux.
69. RIPPLES - Periodic thickness variations
in a coating.
70. ROLLER MARK or ROLLER PRINT - A deviation
or deformation in thickness caused by excessive pressure
or a squeezing action on the substrate material.
71. ROLLER SCUFF (Glass) - A marring or
abrasion of the surface, a series of small fine scratches
caused by detrimental roller contact.
72. 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.
73. RUB (Glass) - (Also see Roller Scuff,
Scratch and Scuff). A surface scratch or series of small
scratches generally caused in handling.
74. RUB-OFF - Pertains to the chamfered
area used mainly to describe the mechanical method of relieving
an edge deburring).
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75. SCALE - Particles of carbon or metallic
substances adhered to or embedded in the glass, usually red
or black.
76. SCHLIEREN - Disk flatness testing
technique displaying pseudo interferometric colors.
77. 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.
78. SCRATCH - A single linear abrasion
of the glass surface which may be of any length, width
or direction.
79. SEED (Glass) - An elongated bubble
less than .030" length. A gaseous inclusion.
80. SEGMENT - A wedge-shaped portion of
a disk’s surface, referred to in error testing.
81. SHEET - Refers to raw stock for the
substrate blanks before processing.
82. SHELL - A depression or irregularity
on the glass surface.
83. SIGNAL AMPLITUDE - The measurement
of magnetic flux reversals coupled through the read heads
controlled by their amp-turns of pickup coil. Note — Amplitude
is maximum at OD and minimum at ID. Amplitude increases
as magnetic layer gets thicker and head flies closer to
disk.
84. SIZING - The machining operation on
a blank substrate which assigns accurate dimensions to
the inner and outer diameter.
85. SKI JUMP - That area of disk where
the average surface height increases followed by a sharp
This depression area at the OD during plating will cause
excessive buildup resulting in a ski jump effect when heads
fly over area.
86. SLEEK - A very fine surface abrasion
or hairline scratch.
87. SLURRY - 1. A process of manufacturing
disk coating which uses a chemical compound or mixture
and the disk is spun up depositing a magnetic layer. This
method is subject to variations of thickness. TOP COATING
uses 1. A mixture of insoluble fine material in suspension
in an aqueous or chemical carrier solution. 2. A compound
consisting of a selected polishing material (i.e. diamond
dust, alumina, etc.) suspended in a viscous liquid form.
88. SPUTTERING - The process of depositing
a target material on the surface of a disk, via discharge
of plasma.
89. STAIN (Glass) - Any erosion of the
glass surface, cloudy in appearance, sometimes exhibiting
apparent color.
90. STONE (Glass) - Opaque or partially
melted particles of rock, clay or batch material embedded
in the glass.
91. STONE GRIND - A method of material
removal to achieve desired flatness and thickness dimensions
of a substrate.
92. STREAK - Surface distortion or irregularity,
visible when illuminated from a point light source, may
also be related to thickness variation.
93. STRESS RELIEVING - The reduction of
the effects of internal residual stresses in substrate
blanks. lanks.
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94. 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.) (See Figure 1.)
95. TEAR-OUTS - Microscopic removal of
base material either substrate or magnetic layer.
96. TEMPER - Physical property of metal
grain structure obtained by subjecting the alloy to specific
sequence of basic treatments. The sequence of letters and
digits following an aluminum alloy designation specify
the temper.
97. THERMAL EXPANSION - The effect of
dimensional changes caused by temperature variations. Each
material has its own characteristic coefficient of expansion.
98. 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.
99. 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.
100. 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.
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101. WARP - A large surface irregularity;
any deviation from a true plane.
102. 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.)
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103. YIELD STRENGTH - The stress applied to a material which will cause a specific permanent deformation.
