printed circuit board (PCB) Etching
The process of manufacturing the Printed circuit board laminate is handled by a subcontractor. It is a very interesting process to watch (well, if you enjoy seeing factories...) - we have some photos,We outline the steps in the process below.
The PTH Printed Circuit board manufacturing process.
CAD File processing
The PCB CAD files (or Gerber files) are sent to the manufacturer by email
The PCB manufacturer has their own pre-production inspection of the files at which they add a drill list and identification
The CAD files are rasterised and photoplotted to make film artwork
Laminate drilling and electroplating
The process starts with bare laminate material - usually FR-4
The laminates, (with copper on both sides, but no pattern yet) are drilled with holes. For reasons of economy, the laminates arelarger panels that often contain several PCBs
The drilled laminates are coated in a chemical to enhance electroplating of holes. This is usually done using a multistep process called electroless copper.
The laminates are put in a copper plating bath, all the holes are electroplated.This connects pads on opposite sides of the PCB, electrically, through copper in each hole.
Laminate etching
The laminates are coated with a UV-sensitive photo-resist
The track pattern is imaged onto each side of each PCB, using the photoplots and UV light
The photo-resist is developed, leaving photo-resist only where copper is required
The laminates are put in acid, to etch away unrequired copper, forming the track pattern
The bare copper PCB, with tracks and pads now finished, is cleaned
Laminate solder masking and tinning
The bare copper PCB is silkscreened with a solder mask (usually green)
(Sometimes the solder mask is applied by photoimaging or dry film)
The solder mask is dried or cured
The PCB is tinned or plated - solder, silver or gold is applied to exposed pads
The PCB is levelled - bumps in the solder are made flat by using hot air
Final stages
The PCB is silkscreened with component Identification lettering (usually white)
The silkscreen legend is dried or cured
Any final drilling is done of holes that are not to be plated through, any routing is done, and the laminate is cut into individual printed circuit boards
