Key Terms, Important Notes & Design Dimensioning
Copper bonded to polyimide without the use of an adhesive. Annular Ring: Distance from edge of hole to edge of pad or solder mask.
Automated Optical Inspection
(Material thickness)/(diameter of drill) OR (height)/width. Base Copper: Copper thickness before plating. Copper can be RA or ED.
Rectangular pad which will be wirebonded. Surface finish is thick soft gold.
Electroplate requires current flow. If plating occurs after the traces have been defined the traces/pads which require plating cannot be isolated. They must be connected to areas outside the perimeter via buss/tie bars. The connection is broken by drilling through the traces.
BT (Bismaleimide Triazine)
Material commonly used for rigid circuits. Higher Tg than FR4. Core: Standard material consisting of a dielectric with base copper on both sides.
Standard material used for solder mask consisting of polyimide and adhesive.
Diameter of hole created by laser or mechanical.
Datum and reference points should be located in the center of pads or holes.
Dimensions from the edge of copper will include etch tolerance (2x if edges face each other). Datum placed on the perimeter will include one of the larger tolerances if mechanically routed.
Copper type used in static situations, also known as ’flex to install’ applications.
Standard material consisting of a layer of copper.
The surface finish is applied before solder mask. The surface finish will adhere to the top of all the traces. The sidewalls of the traces may or may not receive the finish depending upon the process.
Diameter of Finished Hole Size (FHS).
Non plated holes = drill
Plated holes = drill + (2 x via wall)
Rigid Board Specification.
Flex Board Specification.
High Density Interconnect Board Specification.
A replacement process. The base metal goes into solution and is replaced with the surface finish. Once the base metal is covered the process stops resulting in a very thin finish.
Refers to layer of copper in most instances.
LPI (Liquid Photo Imageable)
Thin layer of liquid which is applied, imaged and cured to create a solder mask. Micron: Equal to 0.0394” or 39.4 mil.
0.001 inch. Equal to 25.4 microns.
NPTH (Non Plated Thru Hole)
Holes typically used for mounting. No copper wall.
Typically, a test point, used for a solder connection, or surrounds a via.
Thickness of copper added by electro-plate (ED copper).
Material commonly used for flex circuits.
Prepreg (Preimpregnated glass cloth)
Glass cloth with B stage (semi cured) epoxy.
RA (Rolled-Annealed Copper)
Copper type used in dynamic applications which require frequent flexing.
Tolerance between center to center (c-c).
A layer of material (tin, dryfilm, gold) which protects (masks) areas from subtractive or additive processes. SMOBC (Solder Mask Over Bare Copper): Finish applied after solder mask, only exposed copper effected.
Total surface thickness
Base copper + plated copper.
Area where the material steps down due material removed to form a cavity or flex extending from rigid. Units: Mil (0.001”) unless noted.
Hole in dielectric whose walls are plated with copper to make an electrical connection between layers.