In this section I will outline the basic stages in the manufacture of a Plated Through Hole PCB. Many of the stages used are common to other PCB types so a basic understanding can be obtained.
1) Board Design |
2) Front-End |
3) Photoplotting |
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The PCB starts its life as a schematic diagram. The logic is defined and then the components are added to the board and routed. |
The output from the CAD package is checked for manufacturability and arranged in a suitable manner for manufacture. |
The Front-End output is plotted on a laser photoplotter to produce working photographs. |
4) Drilling |
5) Direct Metalisation |
6) Photomech |
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Holes are drilled into the laminate as defined by the customer design using CNC drilling machines. |
Thin film of graphite is deposited in the holes to provide electrical continuity through the drilled laminate. |
Photosensitive film is laminated onto the PCB and the photographic pattern is exposed and developed from the surface. |
7) Electrolytic plating |
8) Etching |
9) Printing |
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The circuitry and holes are plated with 25-30 microns of copper and 5 microns of tin plate. |
The copper that is not required is etched off to leave the desired circuit. |
The solder mask & ident is printed onto the board to protect and aid component placing. |
10) Hot Air Leveling |
11) Profiling |
12) Inspection/Test |
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The copper areas of the pads and holes are coated with an even layer of a Tin based alloy to aid soldering. |
Boards are either scored or routed depending on the customer requirements. |
Boards are 100% visually inspected and/or tested before despatch. |
