printed board cemented joint program based on ul/iec 60950 ... · printed board cemented joint...

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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.


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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Agenda

Introduction

Background on End Product Standards

End Product Requirement for Printed Boards

UL Certification Programs for Printed Boards

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Introduction


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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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

Asia China (2012)

- Materials Lab

Hong Kong

India

Japan

Malaysia

New Zealand

Singapore

South Korea

Taiwan

- Materials Lab

UL’s Global Organization Major Test Laboratories

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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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Linear

Switcher

Planar

Miniature


Prepreg

Core Laminate

Core Laminate

Prepreg

Prepreg


Background on End Product Standards


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


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.


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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End Product Requirements for PWBs


“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


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


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).


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.


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


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

Insulation

Accessible Conductive

Parts

Insulation Breakdown


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


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


UL Certification Programs for Printed Boards


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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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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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 Flow Test Start 11 samples

Measure Spacing (MSA for 1 Sample)

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

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 Breakdown ? Visual Check or MSA verify

Dielectric Strength Test (V)

Data Recording

5 samples 5 samples

T1 = MOT+10oC

V – Default Voltage is

3000 x 1.6 = 4800 V


Sample Coupon with Different DTI

(pattern-to-pattern)

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Sample Coupon – Actual Sample

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Minimum Laminate Core

Max Int. Cu

Max Int. Cu

Prepreg #

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).

PWB Construction for the Test Coupon

(pattern-to-pattern)

Cu Plating for PTH

Ext. Cu

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Example of Actual Sample – Microsection

Distance Through Insulation Spacing: 0.25 mm



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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Cemented Joint Program 60950-1:

Example scenario

Construction: Planar transformer with primary & secondary

(SELV) winding on same inner layer.

Requirement: Reinforced insulation required between Primary

& SELV circuits.

Product rating (AC Mains): 100 - 240 Vac

PWB: R/C PWB rated 130 °C (MOT)

Working Voltage: Maximum Working Voltage seen by Reinforced

insulation is 600 Vpk

DTI: 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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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.


THANK YOU


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.

40



High Tech Section of UL.com

White Paper:

IEC 62368-1: A New Safety

Standard for High-Tech

Products

Technical Briefs:

20+ Miscellaneous Topics

41




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

42


Learn more about HBSE & Safety Science


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


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


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

Prepreg

Core Laminate

Prepreg

Core Laminate

Distance Through Air

DTI (Distance Through Insulation)

Prepreg

Distance Along Insulation

DTI

DTI


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


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


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


• 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.


Pollution Degrees (cont’)


• Conductive pollution, or dry non-conductive pollution which could become conductive due to expected condensation

• Local environment within the equipment


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

Insulation

Accessible Conductive

Parts


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.


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


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.


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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