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PCB clone

Patterning PCB Manufacture

  Time:2012-06-01 10:49

The vast majority of printed circuit boards are made by bonding a layer of copper over the

entire substrate,sometimes on both sides(creating a blank PCB), then removing unwanted

copper after applying a temporary mask(e.g.,by etching), leaving only the desired copper

traces. A few PCBs are made by adding traces to the bare substrate(or a substrate with a

very thin layer of copper) usually by a complex process of multiple electroplating steps.The

PCB manufacturing method primarily depends on whether it is for production volume or

sample/prototype quantities. Double-side boards or multi-layer boards use plated-through

holes, called vias. to connect traces on opposite sides of the substrate.

Patterning method for large volume :
Silk screen printing :the main commercial method
Photographic methods:used when fine linewidths are required.

Patterning method for small volume :
pringting onto transparent film and use as photomask along with photo-sensitized boards.

(i.g.,pre-sensitized boards),then etch.Alternatively, using a film photoplotter.
Laser resist ablation:Spray black paint onto copper clad laminate, place into CNC laser

plotter.The laser raster-scans the PCB and ablates(vaporizes) the paint where no resist is

Use a CNC-mill with a spade-shaped(i.e., a flat-ended cone) cutter or miniature end-mill to

rout away the undesired copper,leaving only the traces.
Subtractive processes
Subtractive methods,that remove copper from an entirely copper-coated board,used for the

production of printed circuit boards:

1. Silk screen printing uses etch-resistant inks to protect the copper foil.Subsequent

etching removes the unwanted copper.Altenatively, the ink may be conductive,printed on a

blank (non-conductive) board.The latter technique is also used in the manufacture of hybrid


2. Photoengraving uses a photomask and developer to selectively remove a photoresist

coating.The remaining photoresist protects the copper foil.Subsequent etching removes the

unwanted copper. The photomask is usually prepared with a photoplotter from data produced by

a technician using CAM, or computer-aided manufacturing software. Laser-printed

transparencies are typically employed for phototools,however, direct laser imaging

techniques are being employed to replace phototool for high-resolution requirements.

3. PCB milling uses a two or three-axis mechanical milling system to mill away the copper

foil from the substrate. A PCB milling machine(referred to as a PCB Prototyper) operates in

a similar way to a plotter, receiving commands from the host software that control the

position of the milling head in the x,y, and z axis .Data to drive the Prototyper is

extracted from files generated in PCB design software and stored in HPGL or Gerber file

format .