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

[mmitchell]

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

 

[FvM]

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.

 

[mmitchell]

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

 

[senilicus]

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.

 

[mmitchell]

senilicus,

I got it, thanks for suggestion.

Matt