F A Q ' s
  What is the most efficient method of providing a PCB manufacturer with artwork?

Most companies have moved away from hard copy artwork these days. The generally accepted method is to transfer electronic (Gerber and HPGL) data by modem or Internet. However modems can sometimes be troublesome with compatibility problems, busy lines and the expense of long distance calls. So increasingly the Internet offers a trouble free, cost effective service. An important point, most PCB manufacturers prefer customers to include the machining details in the form of a drawing within the electronic data package. This enables work to begin immediately - often this item is forgotten.

Apart from the data file of the track work, what other information does a PCB manufacturer need before production can begin?

Basic specification data is often omitted. We need to know finished board thickness, copper weight of inner and outer layers, silk screen legend color, solder mask color, profile tolerance and ML build if impedance is critical.

What is the best way to dimension the finished profile of the board?

The profile of a board should always be referenced to an easily recognized datum. This can either be a component hole or the finger of a gold edge connector. Clear, uncluttered dimensions eliminate any chance of error or confusion. The golden rule must be keep it clear and simple.

How much space do I have for silk screen legend?

All the area not occupied by drilled holes or surface mount pads. It is often difficult to design a board that meets this requirement. When designs are received where silk screen legend encroaches upon the holes or pads a competent manufacturer will have the facility in its front end work stations to clip out the offending text. This obviously needs the customer's permission and can delay the commencement of production.

What is the practical limit for solder mask dams between surface mount pads?

This should be considered as 0.1 mm for the production of cost effective boards.

Do via holes need pads on the outer layers?

Yes, and it should be remembered that these must be at least 0.3mm larger than the finished hole size to ensure that the drilled hole is adequately surrounded by copper at all stages of manufacture.

Can I leave isolated tracks on the surface of the board?

This is a most unwise procedure. These isolated tracks will become over plated and will be difficult to cover with solder mask. If the design needs an isolated track then it is advisable to cross hatch the unpopulated area.

What is the smallest via hole that can be incorporated before incurring additional cost?

As boards are stacked for drilling, the size of the smallest hole determines the drilling stack height. Often via holes are unnecessarily made too small with the effect of increasing drilling costs. For most manufacturers, the smallest via before incurring a cost penalty would be around 0.45mm finished size.

What are the cost implications of buried vies?

The cost of a blind and buried via board depends upon the quantity of holes between different layers as this will dictate the number of bonding and drilling operations. Typically a 50% increase in price occurs. It is often more cost effective to increase the layer count by 2 layers than move to blind and buried via.

How can I differentiate between development and production boards?

One method is to use a different color resist to the standard green. In particular, boards with red resist are very easy to spot. An alternative method is to print legends with a different silk screen color, white or yellow being standard.

What format can you read?

We prefer to receive Gerber data, HPGL, extended Gerber (RS274X) or ACAD DWG/DXF, but if you cannot output in these formats, send your design data and we will arrange for it to be post processed.

Manufacturing Guidelines

Starting Requirements, Standards Specifications
The following is a list of the desired components needed to start a job.
  1. Gerber Data for All Artwork Layers
  2. Aperture* List or Lists for all layers.
  3. Drill file in Gerber or Excellon format.
  4. Prints that show:
    ( Print should be a hard copy, or in Gerber or HPGL format.)
  • Fab dimensions with tolerances.
  • Datum.
  • Hole coding.
  • Overall thickness.
  • Hole size reference with the following info. For each symbol.
  • Finished Hole Size.
  • Tolerance.
  • Plated vs. Non plated.
  • Hole quantity.
  1. Special Notes or "Read Me" file that pertains to:
  • color and type of soldermask.
  • color of Silkscreen.
  • Plating thickness for Copper, Nickel and Gold
    (If applicable ).
  • Notes for Cross sectioning or Serialization .
  • Controlled Impedance Requirements and tolerances if any.
  • Any other special requirements or instructions.
  1. Standards and Specifications:
  • IPC-A-600 Acceptability of printed wiring boards.
  • IPC-RB-276 Qualification and performance specs.
    ( Class 2 )
  • IPC-D-275 Design standards for rigid printed boards.
  • IPC-TM-650 Test methods manual.
  • IPC-SM-840 Qualification and performance of permanent polymer coatings.