Glossary: the terms around old boards and new manufacturing data
Purchasing, engineering and the fabricator often use different words for the same thing. Here are the terms you will meet in our offers and reports.
Updated:
- Assembly drawing
- Drawing that shows where each component sits, with reference designators and polarity.
- BOM (Bill of Materials)
- Parts list with quantity, reference designators, manufacturer and part number for every component.
- Centroid / pick-and-place data
- Table with position, rotation and side of every component, used to program assembly machines.
- DMSMS
- Diminishing Manufacturing Sources and Material Shortages – the aerospace and defence term for obsolescence.
- Drop-in replacement
- A component that replaces another without any change to the board.
- ENIG
- Electroless Nickel Immersion Gold – flat, solderable surface finish for fine-pitch SMD.
- EOL (End of Life)
- Announcement that a product will be discontinued.
- Excellon
- Standard file format for drill data: hole positions and diameters.
- Fabrication drawing
- Drawing with outline, stack-up, material, finish, tolerances and special requirements for the bare board.
- FFF (Form, Fit, Function)
- Replacement that is mechanically and functionally interchangeable at board or system level.
- FR-4
- Glass-fibre reinforced epoxy laminate, the standard base material for PCBs.
- Gerber (RS-274X, X2)
- Standard file format describing each copper, solder mask and silkscreen layer of a PCB.
- HASL
- Hot Air Solder Levelling – surface finish where the board is dipped into solder and levelled with hot air; available leaded and lead-free.
- IPC-2581 / ODB++
- Intelligent data formats that contain all layers, drilling, netlist and stack-up in one file.
- LTB (Last-Time Buy)
- Final date for ordering a discontinued part.
- Netlist
- List of all electrical connections between component pins.
- NRND
- Not Recommended for New Designs – the part is still produced, but its end is in sight.
- PCN
- Product Change Notification – formal notice of a change to a component.
- Reflow soldering
- Soldering SMD components by melting printed solder paste in an oven.
- Reverse engineering
- Reconstructing design data from an existing physical product.
- SMD / SMT
- Surface-mount device / technology – components soldered directly onto pads on the board surface.
- Stack-up
- Sequence and thickness of copper and insulating layers in a PCB.
- THT
- Through-hole technology – component leads inserted through holes and soldered on the other side.
- Via
- Plated hole that connects copper layers.
- Wave soldering
- Soldering process in which the underside of the board passes over a wave of molten solder; classic for THT.