This part of IEC 60664 specifies the dimensioning of clearances and creepage distances for spacings equal to or less than 2 mm for printed wiring board and equivalent constructions, where the clearance and the creepage distance are identical and are along the surface of solid insulation, such as the paths described in 6.2 of Part 12 (Examples 1, 5 and 11).
The dimensioning in this standard is more precise than that provided by Part 1. However, if the precision provided by this standard is not required, Part 1 may be applied instead.
This standard can only be used in its entirety. It is not permitted to select one or more clauses from this standard and to use them in place of the corresponding clauses of Part 1. In addition, this part of IEC 60664 can only be used together with Part 1.
When this Part 5 is applied to the dimensioning of clearances and creepage distances equal to or less than 2 mm, all clauses are used in place of the corresponding clauses given in Part 1. For clearances and creepage distances larger than 2 mm, and for solid insulation in general, Part 1 applies.
NOTE 1 The limitation to distances equal to or less than 2 mm applies to basic or supplementary insulation. The total distance of a reinforced or double insulation may be larger than 2 mm.
This standard is based on the following criteria for dimensioning:
minimum clearances independent of the micro-environment (see Table 2);
minimum creepage distances for pollution degrees 1, 2 and 3 to avoid failure due to tracking (see Table 4);
minimum creepage distances to avoid flashover across the insulating surface (see Table 5).
NOTE 2 For minimum creepage distances to maintain adequate insulation resistance, see Table A.2.
NOTE 3 This standard is not applicable to micro-environmental conditions worse than pollution degree 3 or humidity level 3.
A test method is specified for allocating unclassified insulating material to the relevant water adsorption group.