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PCB Design below are a number of guideline rules to follow and keep in mind when designing PCBs upto 16 layers. Board Size :
PCB manufacturers have a maximum size board they can handle. Typically this is also their panel size. Normal board spacing for routing is 0.3", plus there is typically a 1.0" to 2.0" border on the board for handling it during processing.
 Trace Width and Spacing :
The chemical and photographic processes used to produce a PCB put requirements on the minimum width of trace and the minimum spacing between traces. If a trace is made smaller than this minimum width there is some chance it will open (no connection) when manufactured. If two traces are closer together than the minimum spacing there is some chance they will short when manufactured. These parameters are usually specified as "x/y rules", where x is the minimum trace width and y is the minimum trace spacing. For example, "8/10 rules" would indicate 8 mil minimum trace width and 10 mil minimum trace spacing. These rules (especially spacing) apply to any metal on the PCB, including pad to track spacing and line widths for strings on the PCB.
Pad Sizes :  | The biggest issues with pad size are solderability and manufacturability. Manufacturability is concerned with whether or not the pad will be broken when the hold is drilled in it. This is mainly a function of the accuracy of the PCB manufacturer's drilling. If a drill hole is slightly off center the pad may be broken at one edge possibly leading to an open in the circuit. A standard requirement for pad sizes is a 5 mil annulus. This means there must be .005" all around the hole. Something a little larger than this (may be 10 mils) is recommended for solderability. |
Hole Sizes : When choosing a hole size we remember that the plate-through will cause the hole to effectively be more narrow. The plate-through thickness varies from .001" to .003". SMD Circuit's plate-through thickness is approximiately .015" (meaning the "finished hole" diameter is 3 mils smaller).
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