Most effective PCB Prototyping Techniques for Better Performance

2. PCB Fabrication

Once the PCB layout design is completed, the following files are to be sent to the fabrication house for PCB fabrication:

1. Gerber files for all copper layers, solder mask layers if required, silkscreen (legend) layer, board outline
2. NC Drill files

• Mechanical drawing

Gerber has been the standard format for PCB manufacture for many years.  It is recommended to generate the gerber files in the RS-274x format.  This will eliminate need for the PCB manufacturers to load the apertures during the tooling process.

The NC Drill files are the program input for the numerically controlled drilling machine for the PCB.  NC drill files should be in the excellon format.

The Mechanical drawing should contain the following:

1. Exact board outline with dimensioning.
2. Exact position of mechanical features of the board such as cutouts, slots etc.

• A reference hole

1. Positional indication of all drills using symbols
2. Tolerance of the holes
3. Layer stack up details

Additionally a text file with the following fabrication parameters need to be provided :

1. Board Name/Part number
2. Board size/tolerance

• Board thickness (typically 1.6mm)

1. Number of layers
2. Dielectric material (typically FR4)
3. Copper thickness (typically 0.5oz/1 oz)

• Solder mask type (typically LPI)
• Silkscreen on either side of the PCB

1. If design requires controlled impedance, Blind/buried via
2. Surface finish
3. Stencil requirement

• Bare board testing (BBT)

BBT is a testing done by the PCB manufacturer on request, which test the bare PCB for any open/short in the circuit connections which are defined by the netlist provided.

Once a newly fabricated PCB is received from the PCB manufacturer, a visual inspection can be performed to personally make sure that nothing is amiss.  Simple testing, like checking for a power – ground short using a multimeter will give you that confidence about the PCB.

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