Track & Gap size

It can be difficult for PCB designers to instinctively know what to do about track size and the spacing between tracks when starting a new layout. Very often what happened in the past is the starting point, however this could lead equally to 'over specifying' or 'under specifying' the design details to the manufacturer.

IPC-2221 contains very useful information, in the form of a table, regarding best practice for conductor spacing (voltage clearance) under varying conditions.

Conductor cross sectional area for thermal management can be found in IPCs new standard 'Standard for Determining Current-Carrying Capacity In Printed Board Design', IPC-2152.

But what about a generic guidelines for track & gap? This will largely be dictated by the designs complexity and any fabricators capabilities. In general track & gap should always be as large as you can 'get away with' as this enables the manufacturer to produce a cheaper and more reliable board. For low to medium density boards a minimum track & gap 'X' might apply and for denser designs a minimum track & gap of 'Y' might apply. The values for X and Y could be aligned with a fabricators capabilities, e.g. some fabricators specify their capabilities as 'standard' and 'advanced'. Typical values for 'standard' may be 90um and for 'advanced' 75um.