IEC PAS 61191-10:2022

IEC PAS 61191-10 ®
Edition 1.0 2022-07
PUBLICLY AVAILABLE
SPECIFICATION
colour
inside
Printed board assemblies –
Part 10: Application and utilization of protective coatings for electronic
assemblies
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IEC PAS 61191-10 ®
Edition 1.0 2022-07
PUBLICLY AVAILABLE
SPECIFICATION
colour
inside
Printed board assemblies –
Part 10: Application and utilization of protective coatings for electronic

assemblies
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.180; 31.190 ISBN 978-2-8322-3981-0

– 2 – IEC PAS 61191-10:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PRINTED BOARD ASSEMBLIES –
Part 10: Application and utilization of protective
coatings for electronic assemblies

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
A PAS is an intermediate specification made available to the public and needing a lower level
of consensus than an International Standard to be approved by vote (simple majority).
IEC-PAS 61191-10, submitted by GfKORR – Gesellschaft für Korrosionsschutz e.V. was
processed by IEC technical committee 91: Electronics assembly technology. It is based on
Guidelines for the application and utilization of protective coatings for electronic assemblies –
Selection, fields of application, requirements and application recommendations – provided by
the working party “Corrosion protection in electronics and microcircuitry”. The structure and
editorial rules used in this PAS reflect the practice of the organization which submitted it.

The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft PAS Report on voting
91/1781/DPAS 91/1788/RVDPAS
This PAS shall remain valid for an initial maximum period of 2 years starting from
the publication date. The validity may be extended for a single period up to a
maximum of 2 years, at the end of which it shall be published as another type of
normative document, or shall be withdrawn.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

– 4 – IEC PAS 61191-10:2022 © IEC 2022
G U I D E L I N E S
for the
APPLICATION AND UTILIZATION OF PROTECTIVE COATINGS
FOR ELECTRONIC ASSEMBLIES
Selection, fields of application,
requirements and application
recommendations
Provided by the working party
“Corrosion protection in electronics and microcircuitry”
GfKORR – Gesellschaft für Korrosionsschutz e.V.

CONTENT
Part A INTRODUCTION
Part B REQUIREMENTS FOR THE COATING OF ASSEMBLIES
1 General requirements
2 Climate impact requirements
3 Regulations for protective coating
3.1 Reference to the general requirements
3.2 Reference to climate impact

Part C CLASSIFICATION OF COATINGS
1 Subdivision according to binding agent
1.1 Acrylates
1.2 Alkyds
1.3 Epoxides
1.4 Polyesters
1.5 Polyurethanes
1.6 Silicones
1.7 UV acrylic hybrids
1.8 Thixotropic protective coatings ®
1.9 ORMOCER s
1.10 Parylenes
2 Subdivision according to solvent
3 Subdivision by drying and curing mechanism
3.1 Physically drying coating materials
3.2 Oxidatively drying coating materials
3.3 Chemically curing coating materials
3.4 (UV-)radiation-curing coating materials

4 Subdivision according to coating thickness

– 6 – IEC PAS 61191-10:2022 © IEC 2022
Part D Film properties of protective coatings
1 Mechanical properties
1.1 Adhesion
1.2 Elasticity
1.3 Hardness
1.4 Further mechanical properties

2 Electrical properties
2.1 Insulation and moisture resistance

3 Thermal properties
3.1 Stress factors
3.2 Thermal mismatch
3.3 Fatigue - the Wöhler curve and its consequences
3.4 Thermal stress load
3.5 Thermal shock resistance
4 Condensation
5 Water absorption and water vapor permeability
5.1 Requirements
5.2 Transport of moisture
6 Thermal resistance
7 Flexibility (modulus of elasticity) and CTE

Part E INFLUENCE OF THE ASSEMBLY ON THE PROTECTIVE COATING
1 Base material
2 Component and circuit board layout
3 Solder resist
4 Soldering materials and soldering process
4.1 Flux types
4.2 Composition of NoClean fluxes
4.3 Residues from the soldering process
4.4 Detection of residues
5 Drying parameters
6 Keeping areas clear and exposing areas

Part F SUBSTRATE AND PRETREATMENT OF PROTECTIVE COATINGS
1 Requirements for the cleaning of assemblies
2 Decision on cleaning
3 Purity requirements
4 Minimum surface purity before protective coating
5 Measurement and analysis of ionic impurities
6 Detection of critical impurities
6.1 ZESTRON Flux Test
6.2 ZESTRON Resin Test
6.3 SIR measurement
6.4 Surface tension
6.5 Technical cleanliness
7 Implementation of the cleaning processes
7.1 Cleaning types
7.2  Cleaning systems
7.3  Microphase Cleaner
8 Optimization of the cleaning processes

Part G APPLICATION METHODS FOR PROTECTIVE COATINGS
1 Subdivision of the application procedures
2 Application by brush or brush method
3 Application by spray cans
4 Application by spraying
5 Application by dipping processes
5.1 Vertical dipping
5.2 Horizontal dipping
6 Flood method application
6.1 Form cup flooding
6.2 Form cup
7 Application by spray process
8 Automatic and selective coating in the casting process

8.1 How the SelectCoat process works
8.2 Closed and circulating coating supply
8.3 Software for the coating system
8.4 Process control
8.5 Coating system

8.6 Non-contact jetting with the PreciseCoat technology

– 8 – IEC PAS 61191-10:2022 © IEC 2022
9 Application via dispensing procedure
10 Application via vacuum process

Part H HANDLING PROTECTIVE COATINGS DURING PROCESSING
1 Requirements for coating rooms and equipment
1.1 Overview and definition
1.2 Explosion-protected areas
1.3 Storage of coating materials
1.4 Mixing and staging areas
1.5 Coating equipment
1.6 Extraction and ventilation in rooms and areas
1.7 Evaporation and drying rooms or areas
1.8 Processing of UV-curing coating systems
1.9 Operation
1.10 Rules and regulations
2 Monitoring processing parameters
2.1 Viscosity and flow time
2.2 Flow time and temperature influences
2.3 Viscosity and temperature

3 Contamination
4 Maintenance of dipping systems
5 Aging of protective coatings
5.1 Coating aging
5.2 Dust and dirt absorption
5.3 Solulibizing substances not related to coating
5.4 Service life extension
6 Environmental protection with regard to protective coating
6.1 Regulations and laws for air pollution control
6.2 EU Solvents Directive (VOC Directive)
6.3 Technical instructions (TA) air
6.4 Hazardous substances in the workplace
6.5 Summary
6.6 Literature
Part I AVOIDANCE OF TYPICAL ERRORS DURING PROTECTIVE COATING
1 Application of too high coating thicknesses
2 Double coating
3 Early hermetic capsules of coated circuit boards
4 Avoidance of defects in the protective coating
5 Typical fault patterns in the protective coating
5.1 Chemical causes of error patterns
5.2 Process-related causes of error patterns
5.3 Flow defects
Part J TESTING METHODS FOR PROTECTIVE COATING
1 General verification of the protective coating

2 Methods for testing climate resistance
2.1 Water immersion test
2.2 Coating Reliability Test (CoRe Test)
2.3 Climate-cycle test
2.4 Condensation water test
3 Method for testing coating result
3.1 Coating adhesion
3.2 Coating thickness
3.3 Special features for surface modifications

4 Methods for testing and designing the drying of protective coatings by thermal
analysis
4.1 Problem definition
4.2 Procedure
4.3 Application examples
Part K  REPAIR OF COATED ASSEMBLIES
1.1 Stripping of assemblies
1.1 Chemical coating stripping
1.2 Mechanical coating stripping

2 Soldering through of coatings
3 Repair coating
– 10 – IEC PAS 61191-10:2022 © IEC 2022

PART L BIBLIOGRAPHY
PART M LIST OF AUTHORS
PART N COMPARISON OF THE GUIDELINE WITH THE IPC MANUAL

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