IEC 61051-1:2018 is a generic specification and is applicable to varistors with symmetrical voltage-current characteristics for use in electronic equipment. It establishes standard terms, inspection procedures and methods of test for use in sectional and detail specifications for quality assessment or any other purpose. This edition includes the following significant technical changes with respect to the previous edition:
a) 10 new terms and definitions - leaded varistors, surface mount varistors(SMV), electrostatic discharge (ESD), ESD clamping voltage, equivalent rectangular pulse duration, maximum peak current derating characteristic, rated average dissipation power, rated energy, abnormal overvoltage withstanding duration and temperature derating curve - have been added (see 3.6, 3.7, 3.14, 3.15, 3.19, 3.20, 3.23, 3.24, 3.25 and 3.29);
b) General requirements for electrical tests and 7 new test items - clamping voltage, ESD clamping voltage, maximum peak current, rated average dissipation power, rated energy, electrostatic discharge (ESD), robustness of terminations of surface mount varistors - have been added (see 6.5, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16 and 6.17.8);
c) In 6.6, 6.7, 6.8, 6.9.3, 6.23.2, 6.23.4 and 6.26, following test items have been revised:
- Varistor voltage, leakage current and capacitance: more detailed requirements and information have been added;
- Voltage proof - foil method: the space between the edge of the foil and each termination has been changed from 1 mm ~ 1,5 mm to 3 mm ~ 3.5 mm for testing varistors not having axial terminations and the minimum space between the foil and the termination has been changed from 1 mm to 3 mm for testing varistors having axial terminations;
- Climatic sequence - dry heat: the method has been changed from Ba to Bb;
- Climatic sequence - cold: the method has been changed from Aa to Ab;
- Endurance at upper category temperature: the method of 'applying test voltages in cycles of 1,5 h on and 0,5 h off' has been changed to the method of applying test voltages continuously throughout the test lasting for 1 000 h;
d) The test items of pulse current, voltage under pulse condition and bump have been deleted from the section of test and measurement procedures;
e) Annex A and the contents referring to the test fixture specified in Annex A have been deleted;
f) All contents related to silicon carbide varistors have been deleted;
g) A new normative annex entitled 'Test pulses used in this specification' (Annex B) has been added;
h) A new informative annex entitled "Recommended measurement/test methods for characteristics and parameters for application reference" (Annex C) has been added, in which guidelines of measuring/testing characteristics and parameters for application reference including voltage vs. current characteristic, maximum peak current derating characteristic, thermal resistance and abnormal overvoltage withstanding duration have been given.