Printed Board
Cemented Joint Program Based on
UL/IEC 60950-1 and IEC 62368-1
Presented by
Crystal Vanderpan
Principal Engineer, Printed Circuit Technologies and PV Materials
Underwriters Laboratories Inc.
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Crystal Vanderpan
Principal Engineer for Printed Circuit
Technologies and PV Materials
Joined UL in 1995
UL’s Technical Rep for
• UL PWB and PV Material Standards
• IEC TC82, WG2 PV Materials project team
leader
• Subcommittee Chairman of ASTM D09.07,
Electrical and Electronic Insulating Materials
BS degree in Chemical Engineering and Materials
Science from University of California - Davis
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2
Agenda
Introduction
Background on End Product Standards
End Product Requirement for Printed Boards
UL Certification Programs for Printed Boards
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3
Introduction
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History of Underwriters Laboratories
1894 founded by William H.
Merrill
Opens Underwriters
Electrical Bureau, the
Electrical Bureau of the
National Board of Fire
Underwriters in Chicago,
Ill., USA
First test conducted on a
non-combustible insulation
material
7,024 employees now located
throughout the globe
“Working for a Safer World”
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5
UL’s Global Organization
Major Test Laboratories
North America
United States
- Camas
- Northbrook
- Melville
- Materials Lab
- Research TP
- San Jose
- Materials Lab
Canada
Latin America
Argentina
Brazil
Mexico
Europe
Denmark
Finland
France
Germany
- Materials Lab
Italy
Netherlands
Poland
Spain
Sweden
Switzerland
United Kingdom
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Asia
China (2012)
- Materials Lab
Hong Kong
India
Japan
Malaysia
New Zealand
Singapore
South Korea
Taiwan
- Materials Lab
6
Third Party Safety Testing
Why safety testing?
• To prevent risk of electric shock, fire or injury to persons
Why third party?
• More confidence to customers and/or consumers
• Better market access
• Lower insurance fees
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7
Miniature
Linear
Switcher
Planar
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Prepreg
Core Laminate
Prepreg
Core Laminate
Prepreg
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Background on End Product Standards
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IEC TC108 – Safety of Electronic Equipment within the
Field of Audio/Video, Information Technology and
Communication Technology
Responsible for the following key equipment standards:
• IEC 60065, Audio, Video and Similar Electronic Apparatus:
- Audio/Video equipment, including consumer electronics
• IEC 60950-1, Information Technology Equipment:
- Information Technology Equipment (ITE) and Office Appliances
- Communication Technology Equipment, aka, telecommunication
equipment
• IEC 62368-1, Audio/Video, Information Technology and
Communication Technology Equipment:
- Combines above two only in scope and uses new hazard-based safety
engineering (HBSE) approach
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Key Considerations
UL/IEC 60950-1 & IEC 62368-1 are equipment (systems) safety
standards
• Component requirements, such as printed boards, are derived from
applicable parts of the Standard, thus may not always be as clear as
component manufacturers would like.
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Approach
High level discussion of parallel requirements in 60950-1 & 62368-1
•
IEC 60065 requirements generally are aligned with 60950-1 for PWBs, so
will concentrate on 60950-1 since it is more prevalent
Core requirements are IEC-based, disagreements with the IEC-based end
product requirements ultimately should be addressed with IEC TC108 via:
•
ANSI US TAG TC108 (or appropriate National Committee), and/or
•
IEC (e.g., TC91, Electronics Assembly Technology).
US TAG TC108 leadership always open to membership/participation by
component manufacturers!
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13
End Product Requirements for PWBs
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“Hazard-Based” Engineering Approach
Analyze the installation
• Location and intended use
• Attachment systems, wiring systems, hazards
Analyze the product
• Materials, construction, hazards
Utilize existing standards & knowledge
• Standards may exist for similar products / situations
• Code requirements may exist
Test to provide confidence
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Printed Board Hazards in End Products
Two main ‘hazards’ (energy sources) addressed by printed board
requirements:
• Risk of Fire (Electrically-caused fire)
- Material flammability
• Risk of Electric Shock (Electrically-cause injury)
1.
Outside Surfaces
2.
Inter Layer (layer-to-layer)
3.
Intra Layer (within same layer)
National Differences (ND) require printed boards used as safety critical
components comply with UL 796
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Risk of Fire
In general, the risk of fire is addressed by either:
• The risk of ignition is reduced by:
- Limit the maximum temperature of components under normal
operating conditions and after a single fault, or
- Limit the power available in a circuit, or
- Performing intensive fault testing (e.g., open-/short-circuit all relevant
components).
• The spread of flame in the event of ignition is controlled by:
- Use of flame retardant materials (control of fuel), or
- Use of flame retardant insulation (control of thermal coupling), or
- Use of physical separation (e.g., distance).
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Options for Demonstrating Fire Compliance
Three (3) options for printed boards to demonstrate compliance
for fire safety:
1. Printed board rated V-1 or better;
2. Printed board rated V-2;
3. Printed board rated HB.
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Options for Demonstrating Fire Compliance (cont’)
Printed board rated V-1 or better
Most beneficial option to ODMs/OEMs:
• Allows ODMs/OEMs to have no investigation of individual
components on board
- Such as IC packages, optocoupler packages, passive components and
other small parts
- Standard assumes ignition/fire will be localized
• In high-tech applications, most printed boards are V-0, so the
practice meets minimum requirement.
- NOTE  VTM-0, -1, and -2 CLASS MATERIALS are considered equivalent
to V-0, -1, and -2 CLASS MATERIALS, respectively, but only for
flammability property
• Electrical & mechanical properties are not necessarily equivalent
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Risk of Electric Shock
The risk of electric shock is reduced by provision of insulation
• If the insulation fails, hazardous voltage may be present to operator
access area or accessible conductive parts or circuits
Accessible
Conductive
Parts
Insulation
Breakdown
Insulation
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Options for Demonstrating Shock Compliance
60950-1 & 62368-1 Clearance & Creepage Distance requirements based on
IEC 60664 series standards
IEC TC109, Insulation co-ordination for low-voltage equipment
• Horizontal safety function
• IEC TC109 also responsible for:
-
IEC 60664-1: Insulation coordination for equipment within low-voltage systems - Part 1:
Principles, requirements and tests
-
IEC 60664-3: Insulation coordination for equipment within low-voltage systems - Part 3: Use of
coating, potting or moulding for protection against pollution
-
IEC 60664-5: Insulation coordination for equipment within low-voltage systems - Part 5:
Comprehensive method for determining clearances and creepage distances equal to or less
than 2 mm
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Options for Demonstrating Shock Compliance
Three (3) applications need to determine suitable spacings:
(a) Conductors on outside surfaces
(b) Conductors on different layers (inter-layer, or between layers)
(c) Conductors on same layers (intra-layer, or same layer)
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Conductors on Same Layer
Reduced spacings:
• Design for distances between circuits on same inner layer
• Solid insulation allowed for Basic or Reinforced Insulation
- Distance through Insulation
-
Basic: distance acceptable that passes the Electric Strength test
-
Reinforced: 0.4 mm, minimum
• Performance criteria:
- Thermal cycling, followed by, Humidity conditioning & Electric strength
- External inspection: No cracks or delamination
0.4 mm
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Conductors on Same Layer
Test voltages of Electric strength dependent on:
• Circuit Type (Primary or Secondary),
• Working Voltage, and
• Insulation Grade (e.g., Basic or Reinforced)
Representative Test Voltages (ac, rms)
between circuits for printed boards used in Primary Circuits, and
between Primary Circuits and Secondary Circuits
Insulation Grade
WV ≤ 210 Vpk or dc
WV ≤ 420 Vpk or dc
WV ≤ 1.41k Vpk or dc
Basic
1000
1500
Table 5B
Reinforced
2000
3000
3000
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UL Certification Programs for
Printed Boards
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UL Certification Programs for PWBs
Standard & Category:
•
UL 796, Printed Wiring Boards
•
ZPMV2, Printed Wiring - Component
Adjunct Program:
•
Cemented Joint Program per 60950-1 to meet reduced spacings
(distance thru insulation) on same inner layer of a multilayer PWB
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Cemented Joint Program per 60950-1
Program Objective:
• Allow ITE End product to ‘pre-select’ boards that comply with IEC 60950-1
cemented joint requirements (within stated parameters) so lengthy end
product performance testing (e.g., 30 day thermal cycling) is not required.
Assumptions:
• Insulation Grade: Reinforced Insulation (default) or Basic Insulation (upon
need)
• Overvoltage Category: II
• Evaluation is part of new board evaluation or additional evaluation of
existing UL796 board construction
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Cemented Joint Program per 60950-1
Required Information from PWB manufacturer:
• Recognized MOT > 90C
- For printed boards made of pre-preg, standard only requires special performance tests if the
printed board temperature exceeds 90 C.
• AC or DC Mains application
- AC mains, default
• Maximum Working Voltage
- or V dc
• Distance Through Insulation (DTI)
Note - Min 0.4mm minimum is applicable to Reinforced insulation, i.e., printed board manufacturer
can request any distance 0.4mm or greater and UL will qualify the construction for that distance.
Distances less than 0.4 mm can only be qualified for Basic insulation.
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Cemented Joint Program per 60950-1
Samples required from PWB manufacturer:
• Eleven (11) coupons per UL specification (layout)
• One (1) sample for Microsectioning to measure the spacing
• Five (5) samples for thermal-cycling, humidity conditioning and electric strength
• Five (5) samples for thermal-cycling and electric strength
• Sample Coupon
• A sample coupon is available. It includes multiple DTI options.
• Reinforced insulation requires meeting both construction (min. 0.4 mm DTI) and
performance criteria.
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Test Start
11 samples
Test Flow
Measure Spacing
(MSA for 1 Sample)
5 samples
Thermal Cycling (x 10 times):
1. T1 ± 2°C x 68 hrs
2. 25°C ± 2°C x 1 hr
3. 0°C ± 2°C x 2 hrs
4. 25°C ± 2°C x > 1 hr
5 samples
Thermal Cycling (x 10 times)
1. T1 ± 2°C x 68 hrs
2. 25°C ± 2 °C x 1 hr
3. 0°C ± 2 °C x 2 hrs
4. 25°C ± 2 °C x > 1 hr
Humidity Condition
5. 25°C ± 2 °C, 93 ± 2% RH x 48 hrs
Dielectric Strength
Test (V)
T1 = MOT+10oC
V – Default Voltage is
3000 x 1.6 = 4800 V
Dielectric Breakdown ?
Visual Check or MSA verify
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Data Recording
31
Sample Coupon with Different DTI
(pattern-to-pattern)
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Sample Coupon – Actual Sample
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PWB Construction for the Test Coupon
(pattern-to-pattern)
Cu Plating for PTH
Ext. Cu
Prepreg #
Max Int. Cu
Minimum Laminate Core
Max Int. Cu
Prepreg #
# - Prepreg need to use at least one minimum individual prepreg to build-up to the minimum
overall build-up dielectric thickness. Prepreg ply number and prepreg thickness are not limited, for
example: 106 + 1080 or 106 + 2116, depend on DFM (Design for Manufacturing).
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34
Example of Actual Sample – Microsection
Distance Through Insulation Spacing: 0.25 mm
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Cemented Joint Program per 60950-1
Published UL Report/Certification will specify:
• Rated Board MOT
• Insulation Grade (Reinforced)
• AC Mains (default) or DC Mains
• Maximum Working Voltage
• Minimum DTI (minimum 0.4 mm for reinforced insulation)
• Electric Strength Value (minimum 4800 Vrms for reinforced insulation used
in primary circuit)
• Note: A test voltage of 4800 V rms corresponds to a maximum 1550 Vpk
working voltage per Table 5B, Part 2.
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36
Cemented Joint Program 60950-1:
Example scenario
Construction:
Requirement:
Product rating (AC Mains):
PWB:
Working Voltage:
Planar transformer with primary & secondary
(SELV) winding on same inner layer.
Reinforced insulation required between Primary
& SELV circuits.
100 - 240 Vac
R/C PWB rated 130 °C (MOT)
DTI:
Maximum Working Voltage seen by Reinforced
insulation is 600 Vpk
Minimum DTI required is 0.4 mm
Electric Strength Value:
Test Voltage = 3000 Vrms X 1.6 = 4800 Vrms
Note (1): 3000 Vrms is from Table 5B, Part 1.
Note (2): x1.6 factor is specified in 2.10.11
ZPMV2 LIS Info:
CEMENTED JOINT
Tested per UL60950-1, Sec 2.10.5.5; Working
Voltage: 1550V; Insulation Grade: Reinforced;
Minimum Distance Through Insulation: 0.40mm.
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37
Test voltage of 3,000 V
(1.6x = 4,800 V), the upper
limit of end product
working voltage can be
extended to
1,550 V peak or d.c.
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38
THANK YOU
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Learn more about 60950-1
UL University - http://www.uluniversity.com/
ITE: Designing for Compliance to UL 60950-1 2nd Edition,
CAN/CSA-C22.2 No. 60950-1-07; 2007 and IEC 60950-1 2nd edition;
2005
This newly designed two-day workshop will review product safety of information
technology and communications equipment from the technical design
perspective and in the context of accessing global markets with single
equipment designs. Your experienced UL instructors will cover the based
content of UL 60950-1, and all notable differences between the first and more
recently published second editions.
Also available as online course.
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40
Learn more about 62368-1
High Tech Section of UL.com
White Paper:
IEC 62368-1: A New Safety
Standard for High-Tech
Products
Technical Briefs:
20+ Miscellaneous Topics
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41
Learn more about 62368-1
UL University - http://www.uluniversity.com/
Audio/Video, Information Technology and Communications
Technology Equipment Safety Requirements: Introduction to IEC
62368-1
This one-day workshop provides an introduction to the new safety standard for
Audio/Video, Information Technology and Communications Technology
Equipment Part 1 - Safety Requirements, IEC 62368-1
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42
Learn more about HBSE & Safety Science
UL University - http://www.uluniversity.com/
Applied Safety Science and Engineering Techniques (ASSET)™
The two-day course on Applied Safety Science and Engineering Techniques merges
Safety Science and Hazard Based Safety Engineering principles within the overall
framework of a safety management process. The objective of this ASSET Process is
to achieve, maintain and continuously improve safety. This ASSET Process has been
synthesized from other current, mainstream principles of risk assessment and risk
management, including ISO/IEC Guide 51, IEC Guide 116, ISO 31000, ISO/IEC
31010, ISO 14121, ISO 14971 and IEC (60)300-3-9.
You will learn the basic relationship between hazards, exposure and harm to persons,
property and the environment and the means to safeguard against harm. As an
example of these relationships, the mechanisms by which products can cause injury
to the human body are explored in the workshop. You will also learn to use models
and tools that can help you analyze those mechanisms and determine how best to
prevent harm from occurring, in the framework of risk management, systems
engineering and other relevant principles.
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Key Terminology
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Properties of Insulation
CLEARANCE (Distance Through Air)
• Shortest distance between two conductive parts, or between a
conductive part and the bounding surface (outer surface of
enclosure) of the equipment, measured through air
CREEPAGE DISTANCE (Distance Over Surface)
• Shortest path between two conductive parts, or between a
conductive part and the bounding surface (outer surface of
enclosure) of the equipment, measured along the surface of the
insulation
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Properties of Insulation (cont’)
SOLID INSULATION (Distance Through Insulation, or Thickness)
• Material that provides electrical insulation between two opposite
surfaces, not along an outer surface
Distance Through Air
Distance Along Insulation
DTI
Prepreg
Core Laminate
DTI
Prepreg
DTI (Distance Through Insulation)
Core Laminate
Prepreg
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Types of Insulation
FUNCTIONAL INSULATION
• Insulation needed only for the correct functioning of the equipment
- Does not protect against electric shock, but may reduce the likelihood of
ignition and fire
BASIC INSULATION
• Insulation to provide basic protection against electric shock
SUPPLEMENTARY INSULATION
• Independent insulation applied in addition to BASIC INSULATION in
order to reduce the risk of electric shock in the event of a failure of
the BASIC INSULATION
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Types of Insulation (cont’)
DOUBLE INSULATION (between Primary and Secondary)
• Insulation comprising both BASIC INSULATION and
SUPPLEMENTARY INSULATION
REINFORCED INSULATION (between Primary and Secondary)
• Single insulation system that provides a degree of protection
against electric shock equivalent to DOUBLE INSULATION under the
conditions specified in the standard
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Pollution Degrees
Pollution Degree 1 (PD1)
• No pollution or only dry, non-conductive pollution which has no
influence
• Achieved by enveloping or hermetic sealing components and
subassemblies so as to exclude dust and moisture
Pollution Degree 2 (PD2)
• Only non-conductive pollution that might temporarily become
conductive due to occasional condensation
• IEC 60950-1 & IEC 62368-1 generally assume a PD2 environment,
unless requested otherwise by the manufacturer.
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Pollution Degrees (cont’)
Pollution Degree 3 (PD3)
• Conductive pollution, or dry non-conductive pollution which could
become conductive due to expected condensation
• Local environment within the equipment
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Circuits and Circuit Characteristics
PRIMARY CIRCUIT
• circuit that is directly connected to the AC MAINS SUPPLY
SECOND CIRCUIT
• circuit that has no direct connection to a PRIMARY CIRCUIT and
derives its power from a transformer, converter or equivalent
isolation device, or from a battery
Accessible
Conductive
Parts
Insulation
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Circuits and Circuit Characteristics (cont’)
WORKING VOLTAGE
• Highest voltage measured in peak or d.c., to which the insulation or
the component under consideration is, or can be, subjected when
the equipment is operating under conditions of normal use.
• Overvoltages that originate outside the equipment are not taken
into account.
HAZARDOUS VOLTAGE
• Voltage exceeding 42.4 V peak (30 V r.m.s.) or 60 V d.c., existing in
a circuit that does not meet the requirements for either a LIMITED
CURRENT CIRCUIT (LCC) or a TNV CIRCUIT.
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Circuits and Circuit Characteristics (cont’)
HAZARDOUS VOLTAGE (cont’)
• ELV (Extra Low Voltage), maintained only under normal operating
conditions
• SELV (Safety Extra Low Voltage), maintained under both normal
operating and single fault conditions
• IEC 62368-1 modified concept with introduction of ES1, ES2 and
ES3; voltage, frequency and current dependent
- ES = electrical energy source, defined by electrically-caused injury
- ES1 = meets ES1 limits under normal and abnormal operating
conditions, and does not exceed ES2 under single fault conditions
- ES2 = meets ES2 limits under normal, abnormal & single fault conditions
- ES3 = exceeds ES2
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Overvoltage Category (per IEC 60664-1)
Depends on the manner of connection of the equipment to the
building power supply arrangements.
Is the largest peak value of transient overvoltage likely to be
experienced at the power input interface of equipment
connected to a MAINS SUPPLY is known as the MAINS
TRANSIENT VOLTAGE.
• Minimum CLEARANCES for insulation in PRIMARY CIRCUITS are
based on the MAINS TRANSIENT VOLTAGE.
• Note: IEC 60950-1 & IEC 62368-1 generally assume an Overvoltage
Category II, unless requested otherwise by the manufacturer.
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Circuits and Circuit Characteristics
AC MAINS SUPPLY
• AC power distribution system external to the equipment for
supplying power to a.c. powered equipment.
• These power sources include public or private utilities and, unless
otherwise specified in the standard equivalent sources such as
motor-driven generators and uninterruptible power supplies.
MAINS TRANSIENT VOLTAGE
• Highest peak voltage expected at the
power input to the equipment, arising
from external transients on the MAINS
SUPPLY.
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