[SOLVED] (Via hole – Trace) separation: undefined in IPC-2221?

Hi,

IPC-2221 Table 6-1 (page 51) defined conductor clearance for internal and external layers and different coating conditions. For B-1 (Internal Conductors) class, the description (highlighted in red) says it is also applicable to conductor-PTH spacing.



However, there are still {B2, B3, B4, A5, A6, A7} classes:

• B2 - External Conductors, uncoated, sea level to 3050 m
• B3 - External Conductors, uncoated, over 3050 m
• B4 - External Conductors, with permanent polymer coating (any elevation)
• A5 - External Conductors, with conformal coating over assembly (any elevation)
• A6 - External Component lead/termination, uncoated
• A7 - External Component lead termination, with conformal coating (any elevation)

For which in descriptions following, no particular words have been given on whether they also apply to conductor-PTH spacing.

Are Table 6-1 columns for columns other than B1 applicable to conductor-PTH spacing?

I am asking this because of the case showing in the lower part of the attached image: How far should I separate a via’s hole with tracks in same and different nets, only considering the separation between track and hole alone, not including via land (annular ring) at the time being?


Matt

The table is related to safe isolation, not PCB manufacturing problems. Consequently, it doesn't distinguish between different kinds of copper features, e.g. trace, pad or via as they appear from a manufacturing view. They are however distinguished by their electrical functionality. In this table, only the copper-to-copper clearance and possible encapsulation of the gap matters.

In practice, PCB design must consider both aspects, safe isolation for a particular voltage level and design rules imposed by the PCB technology. The latter are discussed in different chapters of IPC-2221.

FvM,

For manufacturing ability (rather than safe isolation) regarding {conductor-to-conductor, conductor-to-PTH}, is there a place to find reference? Is it in IPC-2221 as you have mentioned?

Matt

If this is about manufacturing capabilities, you should contact your manufacturer or look at their website. Most pcb manufacturers have a capabilty manaul available where you can find this type of information.

senilicus,

I got it, thanks for suggestion.

Matt