BS 7822-3:1995

Committees responsible
National foreword
Introduction
SPECIFICATION
1 Scope
2 Normative references
3 Definitions
4 Design requirements
5 Test specimens
6 Tests
Annexes
A (normative) Test sequence for type A coating
B (normative) Test sequence for type B coating
C (informative) Measuring the insulation distance of a
   coated printed board
Table
1 Degrees of severities for rapid change of
   temperature
Figures
1 Test specimen
2 Examples of land configurations
C.1 Measurement of the insulation distance

Applies to rigid printed board assemblies with an insulating coating applied to one or both sides of the printed board. Describes the requirements and test procedures for printed board assemblies provided with coatings.

This part of IEC 664 applies to rigid printed board assemblies with an insulating coating applied to one or both sides of the printed board. Such coatings are used to provide insulation and to protect the microenvironment of the printed board assembly surface against pollution, for the purpose of insulation coordination. It describes the requirements and test procedures for printed board assemblies provided with coatings.

This part covers two types of coatings:

• type A coating only provides protection against pollution. The clearance and creepage distance requirements of IEC 664-1 apply to the printed board assembly under the coating;
• type B coating provides protection against pollution and insulation. There are no requirements for clearances and creepage distances under the coating. Only the requirements of IEC 664-1 for solid insulation apply.

NOTE 1 For type B coating, the conductors are embedded in solid insulation consisting of the base material and the coating.

NOTE 2 Clearances and creepage distance requirements apply to all uncoated parts of the board and between conductive parts over the coating.

The principles in this part are applicable to functional and basic insulation.

NOTE 3 For supplementary and reinforced insulation, additional requirements, which are under consideration, may apply.