Glossary of Disk / Substrate Industry Terms
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.
The scope of this glossary is limited to disks and substrates.
IDEMA D2-91, Specification for Substrates for Rigid Disks.
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.
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.
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.
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.