Printed Circuit Board (PCB) Etching

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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 electroplatingConventional PCB section

  • 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 etchingSMT PCB section

  • 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 padsPCB section
  • 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

 

 

 

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2018-08-07T04:08:29+00:00