. Annular Ring – Pad Ring
A copper ring attached flat on the board surface around the wall of a plated through-hole. On inner layers, it is often connected to the ground plane via a cross bridge and serves as a line endpoint or via. On outer layers, it acts as a via or a soldering pad for component pins. Synonyms: Pad, Land.
2. Artwork – Film
In PCB manufacturing, this usually refers to black-and-white film. Brown diazo film is separately called Phototool. PCB films are divided into Master Artwork (original film) and Working Artwork (production copy).
3. Basic Grid – Basic Grid
The orthogonal grid for positioning conductor layout in PCB design. Early grid pitch was 100 mil; now it is reduced to 50 mil due to fine-line technology.
4. Blind Via Hole – Blind Via
In complex multilayer PCBs, some vias are not drilled through the entire board as they only connect specific layers. A via with one opening connected to an outer-layer pad ring is called a blind via.
5. Block Diagram – Circuit Block Diagram
A systematic architecture diagram that frames assembled boards and components with squares/rectangles and connects them with electrical symbols.
6. Bomb Sight – Alignment Target
Originally a bomber sight; used as alignment marks at film corners in PCB production. Formal name: Photographers’ Target.
7. Break-away Panel – Breakaway Panel
Small PCBs are combined into a large panel for easier assembly, placement and soldering. After processing, they are connected by tie bars or V-grooves for easy breaking. Example: IC cards.
8. Buried Via Hole – Buried Via
A via buried inside a multilayer PCB, connecting inner layers only and not exposed to outer surfaces.
9. Bus Bar – Bus Bar
Refers to cathode/anode bars in plating tanks or connecting cables. On PCBs, it is a conductive strip near gold fingers for electroplating, removed after final profiling. The small strips connecting individual fingers are called Shooting Bar.
10. CAD – Computer Aided Design
Uses specialized software and hardware for digital PCB layout, converting data into original film via a photoplotter, greatly improving pre-production efficiency.
11. Center-to-Center Spacing – Center-to-Center Distance
The nominal distance between centers of any two conductors. For uniformly arranged conductors (e.g., gold fingers), it is also called Pitch.
12. Clearance – Clearance / Isolation Ring
An empty ring etched around vias on inner layers to isolate them from copper areas. Also refers to the gap between solder mask and pad rings on outer layers.
13. Component Hole – Component Hole
A through-hole for component pins, typically about 40 mil. With the popularity of SMT, large through-holes are reduced, only used for connector pins.
14. Component Side – Component Side
Traditionally the top side for through-hole component mounting; the reverse is the Solder Side. In SMT, both sides mount components, so they are called Top and Bottom Side.
15. Conductor Spacing – Conductor Spacing
The insulating distance between edges of adjacent conductors on the board surface.
16. Contact Area – Contact Resistance
Resistance at the contact interface between gold fingers and connectors. Plating is used to reduce oxide formation and contact resistance.
17. Corner Mark – Corner Mark
Special marks at the four corners of PCB film to define the board boundary. Connecting inner edges forms the finished board outline.
18. Counterboring – Counterbore Hole
A stepped non-plated through-hole (NPTH) to recess a screw head below the board surface.
19. Crosshatching – Cross-Hatched Pattern
A grid pattern etched on large copper areas to improve adhesion to the substrate and solder mask, reducing warping and peeling caused by thermal expansion.
20. Countersinking – Countersink Hole
A tapered hole for screw heads, rarely used in precision electronics.
21. Cross-section Area – Cross-Sectional Area
The cross-sectional area of a PCB trace, which directly affects its current-carrying capacity.
22. Current-Carrying Capability – Current-Carrying Capacity
The maximum continuous current a trace can carry without electrical or mechanical degradation.
23. Datum Reference – Datum Reference
A point, line or hole used as a positioning reference during PCB manufacturing and inspection.
24. Dummy Land – Dummy Pad
Non-functional copper pads added for height leveling, current balancing during plating or mechanical support.
25. Edge Spacing – Board Edge Clearance
The distance from the board edge to the nearest conductor, required for safety and insulation (specified by UL).
26. Edge-Board Contact – Gold Fingers
Gold-plated contact arrays on board edges for connecting to connectors.
27. Fan Out / Fan In Wiring – Fan-Out / Fan-In Routing
Trace routing from closely spaced QFP pads to vias in a fan shape for interconnection.
28. Fiducial Mark – Fiducial Mark
Optical alignment marks on the board for automated assembly vision systems.
29. Fillet – Fillet
A curved fill at vertical intersections of planes or lines, enhancing mechanical strength and current flow at solder joints or trace intersections.
30. Film – Film
Photosensitive film with circuit patterns, usually 4 mil or 7 mil thick, including silver halide (black-and-white) and diazo (brown) types. Also called Artwork.
31. Fine Line – Fine Line
Traces with an average width ≤5–6 mil or four traces between pads.
32. Fine Pitch – Fine Pitch
Lead/pad pitch ≤0.635 mm (25 mil).
33. Finger – Gold Finger
Short for Edge-Board Contact; a series of gold-plated contacts on the board edge.
34. Finishing – Surface Finishing
Surface treatment for appearance, protection and texture, such as plating, anodizing and coating.
35. Form-to-List – Wiring Specification List
A written document specifying wiring systems and connections.
36. Gerber Data / Gerber File – Gerber File
A standard PCB data format (RS-274) developed by Gerber for transferring design data to manufacturing.
37. Grid – Grid
The basic orthogonal grid for PCB layout, originally 100 mil, now 50/25 mil for dense assembly.
38. Ground Plane Clearance – Ground Plane Isolation Ring
An isolation ring around vias passing through the ground plane without connection, allowing thermal expansion and preventing short circuits.
39. Ground Plane – Ground Plane
An inner copper layer serving as common ground, shielding and heat dissipation for components.
40. Hole Density – Hole Density
The number of drilled holes per unit board area.
41. Indexing Hole – Index Hole
Tooling holes at board corners/edges for alignment in imaging, drilling, profiling and lamination.
42. Inspection Overlay – Inspection Overlay Film
A translucent film used to overlay and inspect PCB patterns for first-article verification.
43. Key – Keying Slot
A slot in the gold finger area to prevent reversed insertion (foolproof design).
44. Land – Pad
Refers to through-hole pad rings (traditional) or SMT square pads. Synonymous with Pad.
45. Landless Hole – Padless Via
A via without an outer-layer pad ring, saving space for routing in dense designs, only used for inner-layer interconnection.
46. Laser Photogenerator / Laser Photoplotter – Laser Photoplotter
A device that uses laser and computer control to produce high-precision PCB original film, replacing manual pasting.
47. Lay Out – Layout
The overall arrangement of components, trace routing and via placement in PCB design.
48. Layer to Layer Spacing – Layer-to-Layer Distance
The distance between two copper conductor layers or the thickness of the insulating dielectric in a multilayer PCB.
49. Master Drawing – Master Drawing
The primary reference document for PCB manufacturing, recording dimensions and special requirements; also known as blueprint.
50. Metal Halide Lamp – Metal Halide Lamp
A light source with high brightness and long life, used in exposure, photography and printing, with energy concentrated in the 410–430 nm ultraviolet band.
51. Mil – Mil
A unit of length: 1 mil = 0.001 inch. Often confused with “strip” (10 μm) in the industry; uppercase MIL refers to military standards.
52. Minimum Electrical Spacing – Minimum Electrical Clearance
The minimum distance between two conductors to prevent dielectric breakdown or corona under a specified voltage.
53. Mounting Hole – Mounting Hole
A large non-conductive hole for securing the PCB to the chassis with screws.
54. Mounting Hole – Assembly Hole
A large hole (~160 mil) for fastening the PCB to equipment. Modern designs use NPTH to avoid solder clogging.
55. Negative – Negative Film
A film where conductors are transparent and the substrate is dark (blocking UV light). Also describes a drill bit with narrowed flanks due to improper regrinding.
56. Non-Circular Land – Non-Circular Pad
An enlarged irregular pad for high-strength soldering of large or heavy components, common on single-sided PCBs.
57. Pad Master – Pad Master Film
An early positive film showing only hole locations, used for programming drilling machines and producing solder mask films.
58. Pad – Pad
The soldering base for component pins: through-hole pad rings (traditional) or SMT square pads. Synonymous with Land.
59. Panel – Panel
A production board containing multiple finished PCBs. Larger panels improve production efficiency.
60. Pattern – Pattern
Refers to conductor or non-conductor patterns on PCBs, films or blueprints.
61. Photographic Film – Photographic Film
The carrier of PCB circuit patterns, including Mylar film and glass plate, using silver halide or diazo materials.
62. Photoplotter / Plotter – Photoplotter
A device that converts digital design data into precise PCB film using laser exposure, replacing traditional camera methods.
63. Phototool – Phototool
Generally refers to diazo film, which can be handled under yellow light, more convenient than black-and-white silver halide film.
64. Pin – Pin
Tinned or gold-plated component pins inserted into PCB holes for mechanical support and electrical connection.
65. Pitch – Pitch
The center-to-center distance between two units (pads, leads, traces). Different from Spacing (edge-to-edge insulation width).
66. Plotting – Plotting
The process of drawing actual circuit patterns from coordinate data using mechanical or optical methods.
67. Polarizing Slot – Polarizing Slot
An offset slot in the gold finger area to prevent reversed insertion. Also called Keying Slot.
68. Process Camera – Process Camera
An early tool for enlarging/reducing films or copying manual taped masters into original films, now replaced by digital photoplotters.
69. Production Master – Production Master Film
1:1 original film directly used for PCB mass production.
70. Reference Dimension – Reference Dimension
A dimension for information only, without tolerance, not used for production or inspection.
71. Reference Edge – Reference Edge
A board edge or corner used as a dimensional reference for the entire PCB.
72. Register Mark – Alignment Mark
Special marks on films or boards for checking layer-to-layer registration.
73. Registration – Registration
The accuracy of matching actual conductor positions to the original design or film, a key quality indicator for PCBs.
74. Revision – Revision
A modified version of a specification or design, indicated by uppercase letters.
75. Schematic Diagram – Schematic Diagram
A simplified circuit layout drawing using symbols and electrical connections.
76. Secondary Side – Secondary Side
Formerly called Solder Side (the back side for wave soldering). In SMT, both sides mount components, so renamed Secondary Side.
77. Slot / Slotting – Slot
A groove on the board edge or inside for assembly matching; polarizing slots prevent reversed insertion of gold fingers.
78. Solder Dam – Solder Dam
A solder mask barrier around solder joints to prevent short circuits caused by molten solder flow.
79. Solder Plug – Solder Plug
Solder that fills and solidifies in plated through-holes during wave soldering. Small vias (<20 mil) are covered with solder mask to avoid solder plugs.
80. Solder Side – Solder Side
Traditionally the back side for wave soldering, with traces routed along the board length.
81. Spacing – Spacing
The insulation width between two parallel conductors, often paired with trace width as “line pair”.
82. Span – Span
The width between two specific targets or the distance from a target to a reference point.
83. Spur – Spur
An unwanted protrusion on film pattern edges due to poor resolution.
84. Step and Repeat – Step-and-Repeat Exposure
Repeating a small PCB pattern on a large film for mass production using a special exposure machine.
85. Supported Hole – Plated Through-Hole (PTH)
A normal drilled hole with a metallic wall for conduction and soldering.
86. Tab – Tab
An informal term for gold fingers on the board edge.
87. Tape Up Master – Manual Taped Master
An early original film made by manually pasting black patterns on grid paper, now replaced by CAD/CAM.
88. Terminal Clearance – Terminal Clearance
Isolation space around terminal pads.
89. Terminal – Terminal
A general term for electrical connection devices; narrowly refers to inner/outer pad rings in PCBs. Synonyms: Pad, Land.
90. Thermal Relief – Thermal Relief
A “tennis racket” hollowed pattern on large copper areas to reduce thermal stress, warping and peeling during soldering.
91. Thermal Via – Thermal Via
A via under high-power components (CPU, driver IC) for heat dissipation, not for electrical connection, often connected to large copper areas.
92. Throwing Power – Throwing Power
The ability of plating solution additives to improve coating thickness uniformity across high and low current areas.
93. Thermo-Via – Thermal Via
A dedicated PTH for transferring heat from high-power ICs to the back-side copper area for cooling.
94. Tie Bar – Tie Bar
A temporary conductive strip connecting gold fingers to the bus bar for electroplating, removed after final profiling.
95. Tooling Feature – Tooling Feature
General term for positioning, alignment and reference markers in PCB production: tooling holes, fiducials, slots, etc.
96. Trace – Trace
A general conductor on a PCB, excluding vias, planes, pads and pad rings.
97. Trim Line – Trim Line
The boundary line for final board profiling.
98. True Position – True Position
The theoretical design position of holes or features. Parts are acceptable if within the specified tolerance radius.
99. Unsupported Hole – Non-Plated Through-Hole (NPTH)
A hole without copper plating, used only for mechanical purposes (e.g., screw holes).
100. Via Hole – Via
A PTH only for electrical interconnection, not for component insertion. Types: through via, blind via, buried via.
101. Voltage Plane Clearance – Voltage Plane Isolation Ring
An isolation ring etched on the voltage plane to insulate through-holes from the copper area.
102. Voltage Plane – Voltage Plane
An inner copper layer supplying power to components (e.g., 5V, 12V, marked Vcc), also for heat dissipation and shielding.
103. Wiring Pattern – Wiring Pattern
The overall routing pattern of a PCB design.
104. Working Master – Working Master Film
1:1 original film used for production, which can be copied into working films for manufacturing.
Abbreviations
- CAD: Computer Aided Design
- CAE: Computer Aided Engineering
- CAM: Computer Aided Manufacturing
- MLB: Multilayer Board
- PCB: Printed Circuit Board
- PWB: Printed Wiring Board
- SMOBC: Solder Mask Over Bare Copper
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