Printed Circuit Board (PCB) Etching

Section 1-CAD File processing

• The PCB CAD files (or Gerber files) are sent to the PCB Manufacturer, by modem
• The PCB manufacturer inspects the files, making a drill list and adding identification
• The CAD files are processed and sent to a photoplotter to turn into film artwork

Section 2-Laminate drilling and electroplating

• The laminates, (with copper on both sides, but no pattern yet) are drilled with holes. For reasons of economy, the laminates are larger panels that often contain several PCBs
• The drilled laminates are coated in a chemical to enhance electroplating of holes
• 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.

Section 3-Laminate etching

(for more information , see -photolithography)

• 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

Section 4-Laminate solder masking and tinning

• The bare copper PCB is silkscreened with a solder mask (usually green)
• The solder mask is dried or cured
• The PCB is tinned - solder is applied to exposed pads
• The PCB is leveled - bumps in the solder is made flat by using hot air or hot oil

Section 5-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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        Equipment and Machinery used for PCB Manufacture l EMI PCB Layout l  Design Methods