Printed Board Cemented Joint Program Based on UL/IEC and IEC

Transcription

1 Printed Board Cemented Joint Program Based on UL/IEC and IEC Presented by Crystal Vanderpan Principal Engineer, Printed Circuit Technologies and PV Materials Underwriters Laboratories Inc.

2 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 2

3 Agenda Introduction Background on End Product Standards End Product Requirement for Printed Boards UL Certification Programs for Printed Boards 3

4 Introduction

5 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 5

6 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 Asia China (2012) - Materials Lab Hong Kong India Japan Malaysia New Zealand Singapore South Korea Taiwan - Materials Lab 6

7 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 7

8 Miniature Linear Switcher Planar

9 Prepreg Core Laminate Prepreg Core Laminate Prepreg

10 Background on End Product Standards

11 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 , Information Technology Equipment: - Information Technology Equipment (ITE) and Office Appliances - Communication Technology Equipment, aka, telecommunication equipment IEC , Audio/Video, Information Technology and Communication Technology Equipment: - Combines above two only in scope and uses new hazard-based safety engineering (HBSE) approach

12 Key Considerations UL/IEC & IEC 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.

13 Approach High level discussion of parallel requirements in & IEC requirements generally are aligned with for PWBs, so will concentrate on 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! 13

14 End Product Requirements for PWBs

15 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

16 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

17 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).

18 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.

19 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

20 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 Breakdown Accessible Conductive Parts Insulation

21 Options for Demonstrating Shock Compliance & Clearance & Creepage Distance requirements based on IEC series standards IEC TC109, Insulation co-ordination for low-voltage equipment Horizontal safety function IEC TC109 also responsible for: - IEC : Insulation coordination for equipment within low-voltage systems - Part 1: Principles, requirements and tests - IEC : Insulation coordination for equipment within low-voltage systems - Part 3: Use of coating, potting or moulding for protection against pollution - IEC : 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 21

22 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) 22

23 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

24 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 Table 5B Reinforced

25

26 UL Certification Programs for Printed Boards

27 UL Certification Programs for PWBs Standard & Category: UL 796, Printed Wiring Boards ZPMV2, Printed Wiring - Component Adjunct Program: Cemented Joint Program per to meet reduced spacings (distance thru insulation) on same inner layer of a multilayer PWB 27

28 Cemented Joint Program per Program Objective: Allow ITE End product to pre-select boards that comply with IEC 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 28

29 Cemented Joint Program per 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. 29

30 Cemented Joint Program per 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. 30

31 Test Flow Test Start 11 samples Measure Spacing (MSA for 1 Sample) 5 samples 5 samples Thermal Cycling (x 10 times): 1. T1 ± 2 C x 68 hrs C ± 2 C x 1 hr 3. 0 C ± 2 C x 2 hrs C ± 2 C x > 1 hr Thermal Cycling (x 10 times) 1. T1 ± 2 C x 68 hrs C ± 2 C x 1 hr 3. 0 C ± 2 C x 2 hrs C ± 2 C x > 1 hr Humidity Condition C ± 2 C, 93 ± 2% RH x 48 hrs Dielectric Strength Test (V) T1 = MOT+10 o C V Default Voltage is 3000 x 1.6 = 4800 V Dielectric Breakdown? Visual Check or MSA verify Data Recording 31

32 Sample Coupon with Different DTI (pattern-to-pattern) 32

33 Sample Coupon Actual Sample 33

34 PWB Construction for the Test Coupon (pattern-to-pattern) Prepreg # Max Int. Cu Minimum Laminate Core Max Int. Cu Prepreg # Cu Plating for PTH Ext. Cu # - 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: or , depend on DFM (Design for Manufacturing). 34

35 Example of Actual Sample Microsection Distance Through Insulation Spacing: 0.25 mm 35

36 Cemented Joint Program per 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. 36

37 Cemented Joint Program : Example scenario Construction: Requirement: Product rating (AC Mains): PWB: Working Voltage: DTI: Electric Strength Value: Planar transformer with primary & secondary (SELV) winding on same inner layer. Reinforced insulation required between Primary & SELV circuits Vac R/C PWB rated 130 C (MOT) Maximum Working Voltage seen by Reinforced insulation is 600 Vpk Minimum DTI required is 0.4 mm Test Voltage = 3000 Vrms X 1.6 = 4800 Vrms Note (1): 3000 Vrms is from Table 5B, Part 1. ZPMV2 LIS Info: Note (2): x1.6 factor is specified in CEMENTED JOINT Tested per UL , Sec ; Working Voltage: 1550V; Insulation Grade: Reinforced; Minimum Distance Through Insulation: 0.40mm. 37

38 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. 38

39 THANK YOU

40 Learn more about UL University - ITE: Designing for Compliance to UL nd Edition, CAN/CSA-C22.2 No ; 2007 and IEC nd 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 , and all notable differences between the first and more recently published second editions. Also available as online course. 40

41 Learn more about High Tech Section of UL.com White Paper: IEC : A New Safety Standard for High-Tech Products Technical Briefs: 20+ Miscellaneous Topics 41

42 Learn more about UL University - Audio/Video, Information Technology and Communications Technology Equipment Safety Requirements: Introduction to IEC 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

43 Learn more about HBSE & Safety Science UL University - 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 and IEC (60) 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. 43

44 Key Terminology

45 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

46 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 DTI Distance Through Air Distance Along Insulation Prepreg DTI Core Laminate Prepreg DTI (Distance Through Insulation) Core Laminate Prepreg

47 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

48 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

49 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 & IEC generally assume a PD2 environment, unless requested otherwise by the manufacturer.

50 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

51 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

52 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.

53 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 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

54 Overvoltage Category (per IEC ) 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 & IEC generally assume an Overvoltage Category II, unless requested otherwise by the manufacturer.

55 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.