Conformal coating standards are a series of specifications and tests which a coating must pass in order to be considered for use in certain environments such as Military or Automotive applications.
Most conformal coatings are either qualified to MIL-I-46058C or meet the requirements of the closely related IPC-CC-830B specification. In addition they may be recognised by Underwriters Laboratories, either as a permanent coating, in which case the flammability of the coating is assessed to UL94V0, or as a conformal coating, where the electrical properties will be assessed as part of the UL746E standard.
These tests all require flat coupons to be coated with the conformal coating in question and are subjected to a variety of temperature and humidity conditions to assess the material’s properties. Whilst perfectly acceptable to assess the potential performance of the material, the actual protective capability of the coating in the end use environment is of greater concern to the user. The rest of this article will be devoted to understanding the issues that relate to end use performance in potentially corrosive environments.
MIL-I-46058C
Military Insulating Compound this is a common standard used throughout the industry for conformal coating materials. While it has been inactive for new designs since 1998, it is still a standard often required by military contractors. The main advantage of MIL-I-46058C is that it requires independent testing by a MIL approved laboratory (although at least one conformal coating manufacturer is an approved test laboratory so not completely independent!) and the military maintains a Qualified Product List (QPL) drawn from successful independent test reports.
Def Stan 59/47
The UK Ministry of Defence standard similar to the MIL-I-46058C this is a standard used by the British military for coatings used in high end electronics.
IEC 61086
International Electrotechnical Commission. Whilst similar in requirements to MIL-I-46058C, this standard is based on supplier self-certification. Of course, an independent test laboratory can be used, but the IEC does not maintain a QPL.
IPC-CC-830B
IPC-CC-830B is closely related to MIL-I-46058C and was introduced to provide an alternative to the MIL spec when it was declared inactive. CC-830 is an active specification and is continually being updated. Once again, there is no requirement to use an independent test laboratory, and there is no QPL maintained for this specification. Materials qualified to MIL-I-46058C are automatically deemed to meet the requirements of IPC-CC-830B.
UL94V0
UL94 relates to the flammability or self-extinguishing nature of the conformal coating on an FR4 substrate. V-0 is the highest classification that can be achieved, with other categories such as V-1 and V-2 denoting materials that burn for longer durations.
UL746E
UL746E is composed of a series of dielectric breakdown evaluations in addition to the UL94 flammability testing, and is intended to denote products that can be safely used on products that are required to meet UL safety standards. By documenting the use of UL recognised materials throughout the design, manufacturers can avoid the requirement to test their device to the applicable UL safety standards.
Environmental Standards
Here at Electrolube we believe that it is everyone’s responsibility, both individually, and as a business look after the world in which we all inhabit. Our R&D team are always looking at ways to minimise our environmental impact and we have several groundbreaking products as a result.
Policy:- Environmental Policy
VOCs – The Need for Change
Volatile solvents used in conformal coatings are classed as VOCs (Volatile Organic Compounds).
VOCs contribute towards the formulation of ground level ozone.
Such pollution can have many detrimental effects on the environment, damaging forests and vegetation.
In addition, some materials classed as VOCs can act as irritants and over exposure can lead to a variety of health problems.
VOC Definitions:
EPA
‘Volatile Organic Compounds (VOC) means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates and ammonium carbonate, which participates in atmospheric photochemical reactions.’
EU Solvents Emissions Directive
‘Any organic compound with a boiling point less than or equal to 250˚C at a standard pressure of 101.3 kPa.’
Previously the directive referred to the definition as ‘Any organic compound, having at 20˚C a vapour pressure of 0.01KPa or more, or having corresponding volatility under the particular conditions of use’.
As stated on the European Commission website, either method is suitable:
The ‘boiling point approach’ was adopted for Directive 2004/42/CE because during negotiations Member States were generally more in favour of this definition of VOCs than the ‘vapour pressure approach’ definition in Directive 1999/13/EC. The main reason is that the boiling point of a substance is easier to identify (and presumably more data are available) than the vapour pressure at room temperature of the same substance. Nevertheless, the results of the two approaches for any one substance are, to the knowledge of the EU Commission, in most cases identical.’
Low VOC Alternatives
Products such as the Electrolube water-based coatings help to keep VOC levels to an absolute minimum without compromising on performance:
WBP ” Utilising hybrid technology, WBP offers the performance characteristics of a polyurethane coating, exhibiting excellent flexibility and solvent resistance. WBP is for dipping application methods.
WBPs – Is based on the same chemistry as WBP but specifically designed for spraying applications.
UVCL” utilises hybrid technology to provide extremely fast curing under suitable UV radiation. UVCL provides excellent protection under a wide range of environments and is characterised by better ‘no-clean’ compatibility and improved thermal shock resistance compared with other UV curable materials.
Electrolube are continually developing ‘greener’ technologies, helping to minimise solvent emissions and their impact on the environment.
REACH
Registration, Evaluation and Authorisation of Chemicals – the REACH system
RoHS regulations
