제이에스알티

PCB/PWB/PWA 관련 고장분석

PCB의 역할

History of the PCB

IPC standard for PCBs

Classification of PCB

PCB Dielectric Materials

PPG (Prepreg) : CCL (Copper Clad Laminate), RCC (Resin Coated Copper)

Phenolic Novolac Resin

Epoxy Resin (DGEBA)

BT (Bismaleimide Triazine) Resin

Kapton Polyimide (Thermoset)

What can 5G mean for PCB?

PTFE (PolyTetraFluoroEthylene)

Polyester (PET), PEN

Constituents of FR-4 Laminates

Resin

Curing agents

Coupling agents

Fillers

Accelerators

Flame retardants

Reinforcement:E-Glass

Woven fiberglass fabric

Glass fabric styles

Laminate fabrication

Copper Foil : ED (electrodeposited) copper foil, DSTF (drum side treated foils 혹은 RTF: reverse treated foils), RA (rolled-annealed) copper foil

Typical Polyimide PCB Assembly Supply Chain

Aluminum PCB (MCCL : Metal Copper Clad Laminate)

Methods for dissipating heat from PCBs : Thermal Via vs Copper Inlay (Coinning)

PCB Manufacturing Process

Process steps for double sided circuit board

Inner layer process steps

Outer layer process steps

PCB surface finishes : HASL, OSP, ENIG, ENEPIG, Immersion Silver, etc.
▷ Failure modes specific to PCB surface finishes (Black pad mechanism & Kirkendall voiding, etc.)
▷ Advantage and Disadvantage
▷ ENIG less than minimum

Multilayer Standard Process

Panel plating (Subtractive process) and Pattern plating

FPCB Manufacturing Process

Process flow for double sided flex

Fine line resolution by different process

MSAP (Modified Semi-Additive Process) approach
▷ Flash etch (differential etch) and ETS (Embedded Trace Substrate)

EPP (Embedded Pattern Process)

Flex and Rigid-Flex Circuits

High performance materials for multilayer rigid/flexible circuits

Types of Flex Circuits : IPC-6013D:2017

Base material : Polyester (PET), PI, PEN, LCP

Adhesive Materials

Conductor Materials

FPCB Design

Flex PCB and its materials : Adhesive-based, Adhesive-less

How to prepare the rigid-flex board outline

Calculating the bend radius : Static flex PCB, Dynamic flex PCB

Guidelines for routing flex PCBs & Pad design for outer layers

Designing and manufacturing vias in flex PCBs : As per IPC 6013

Designing and assembling rigid-flex PCBs

Flex PCB design checklist

IPC standards for flex PCBs

PCB Back Drilling Process (CDD: controlled depth drilling)

What is PCB back drilling process?

Back drilling design values

Advantages of back drilling PTH vias

Step involved in back drilling process

PCB BBT (Bare Board Test) Method : IPC-9252B:2016, MIL-PRF-55110/31032/50884, IPC-6012C:2010

Continuity test (open)

Isolation test (short and/or leakage)

Hi-pot test : IPC-6012C:2010

Test fixtures

Universal grid tester (2-wire measurement & 4-wire measurement) & Dedicated wired grid tester

Frying probe testing

Non contact electrical testing

Cause and Effect Diagram (Electrical Opens in PCBs and Electrical Shorts in PCBs)

PSR (Photoimageable Solder Resist) thickness : IPC-6012, IPC-A-600

Hole plugging ink

Copper foil thickness : ANSI/IPC-A-600H:2010, IPC-4562, IPC-2221, IPC-4101

Internal layer foil thickness after processing

External conductor thickness after plating

Current carrying capacity and sizes of etched copper conductors

Effects of Moisture in PCB

Inner layer delamination

Blistering

Increases dielectric constant (Dk) and dissipation factor (Df)

Oxidation of copper surfaces

Ionic corrosion (Electrochemical migration)

Interfacial degradation (CFF)

Effect of lead-free soldering exposures on PCB laminates

Effects of moisture on glass transition temperature (Tg)

Effects of moisture on coefficient of thermal expansion (CTE)

Concerns with Rigid-Flex circuits

Common mechanisms of moisture transport

Fickian, Wicking, Capillary

Moisture absorption - Dominant sites

Bound and Free water molecules

Wicking and Capillary action in PCBs

Effects of trapped moisture

Moisture control guidelines

IPC-1601:2010

Controls during inner layer production

Bake post-lamination?

Post drill bake

Controls implemented during assembly

Guidelines for baking

Adverse Effects of Baking

Recommendations for Flex, Rigid-Flex Circuits

Moisture Barrier Bags (MBB) : IPC J-STD-033D:2018, MIL-PRF-81705

Desiccant : MIL-D-3464E, MIL-P-116J, IPC J-STD-033D:2018, EIA 583

Humidity Indicator Card (HIC) – Cobalt dichloride free : IPC J-STD-033D:2018, MIL-I-8835

Recommendations – Prior to packaging : IPC-1601

Recommendations packaging, shipment and storage

Measures for moisture control during receiving & handling

PCB packing 방법 및 보관 환경 : IPC-1601:2010

PCB delamination & blistering 사례 : IPC-A-600 Section 3.1.4

Dry Film 및 PSR Tenting 불량 분석 사례

PTH failure 사례

Phenomenon in cross section of PCB PTHs

IPC-6012(Qualification and Performance Specification for Rigid Printed Boards) : Analyzing Top 5 Severities of Supplier’s Nonconformance

Electroless Cu & Electrolytic Cu 시 불량 발생 원인 : IPC-6012

Circumferential fatigue cracking

Opening in PTH/Via

PTH/Via wall-pad separation : Innerlayer copper-to-copper adhesion failures (ICD)

Intermittent failure due to open trace in PCB

Resin Recession과 Hole Wall Separation의 비교 : IPC-A-600

Drill smear & Etchback : Desmear (Permanganate, Plasma 등)

Inner layer separations or inclusions : IPC-6012

Separation or Inclusions between plating layers : IPC-6012

Manufacturing Defects in PTH 사례 : ANSI/IPC-A-600

Drill bit point defect illustrations

Drilling defects

Copper wicking in excess of 2.0 mil : IPC-6012

Internal annular ring less than 2.0 mil : IPC-6012

Electroplating (Aspect Ratio, Throwing Factor) : PCB Copper-plating defects

Drill hole microsection 각도, Glass fabric style, Substrate 종류에 따른 Gouging 영향

The Physics of Microvia Failure

Failure modes: Interfacial separation, Barrel cracks, Corner/Knee cracks, Target pad cracks

Microvia crack 발생 원인 및 사례

Laser drilling : Reduced target pad contact, Barrel shape, Microvia corner crack, Penetration on the target pad

Nano void formation in electroless copper films (non-cyanide-based stabilizer system)

Copper crystal structures (epitaxial structure) in plated Microvias : Bottom-up and Top-down recrystallization

Thermal Expansion : Test Method – IPC TM 650 2.6.26 (IST : Interconnect Stress Testing)
▷ Interface separation (Delamination), Barrel crack, Corner crack, Target pad pull-out

Impurity at grain boundary : 무전해동의 grain boundary 미성장
▷ Due to a heavy incorporation of electroless and electrolytic plating additives

PCB Pattern Corrosion 사례

PCB contaminants 업체별 분석 (by Ion Chromatography) : IPC-TM-650 2.3.28

Corrosion resistance of different PCB surface finishes in harsh environments

Surface finishes 종류별로 Corrosion Test : SO2 Gas test, Kesternich test, Salt Spray test, Surface Insulation Resistance (SIR) test

PCB surface finishes 종류별 creep corrosion 사례 (by MFG test)

Failure Mechanisms in PWAs (printed wiring assemblies)

Board Level Failures

Assembly Level Failures

Common Failures in Today’s PCB

Reliability issues of PWAs

Micro-sectioning of Printed Circuit Board

Goal of Specimen Preparation

Sectioning

Mounting

Grinding and Polishing

Etching

Dye penetrate technique – solder joint failure analysis

PCB & FPCB 업종 공정 실사 평가 (약 60 항목의 check list 에 대한 구체적인 설명)

생산조건 관리 : 각 공정 단계별 중점 관리 points 설명

검사시험

설비관리

자재관리

품질경영체계

ECM / CFF (CAF) / Tracking 관련 고장분석

Failure Analysis of a PCB - CFF (Conductive Filament Formation)

Initial inspection

Electrical testing

X-ray analysis

Removal of components

Removal of metallization traces

Cross-sectioning

Optical & SEM examination

CFF mechanism

Which parameters affect filament formations?

How do the filaments grow?

Factors affecting CAF (conductive anodic filament)

CAF (or CFF) paths and PCB internal conductor spacings

Glass fibers and Coupling (Sizing) agents

Resin-Glass interface/interphase : FIB Sections – Glass/Resin separation

Hydrolysis of siloxane bonds

Board orientation respective to fabric weave (Drill hole 90도 warp & 45도 weft)

Effect of voltage and humidity on time to failure (Rudra Model)

Failure accelerators of CAF

Current assessment methods for PCB : IPC, Military, ISO 9001 & 9002

Identification of PCB defects (Decrease in strength & Increase on stress)

Laminate delamination/Cracking

Fiber & Resin interface delamination

Hollow fiber assessment

Defect description

Hollow fibers and their impact on reliability : IPC-9691, IPC-TM-650, Method 2.6.25

Hollow fiber detection and screening

An example of a hollow fiber causing a short between two path in a PCB

Manufacturing defects which can accelerate and precipitate CFF

Misregistration of PTHs

Drilling damage

Wicking of copper along the fibers due to drill crazing

Irregular copper plating

Copper plating to board interface separation

Board contamination

Hollow fibers

Electrochemical migration 및 CFF (혹은 CAF) 메커니즘에 의한 PCB의 발화 사례

Electrochemical Migration (=Ion migration, Dendritic growth) : IPC-TR-476A:1997, IPC-9201:1996

습도 stress 와 failure mechanism

전자부품에서 나타날 수 있는 부식 고장의 형태

Electrochemical migration (ECM) 에 대한 신뢰성 설계

Electrochemical migration 에 의한 절연 열화

Metal migration mechanism의 차이점 : Electrochemical migration, CFF, Electromigration (EM), Stress induced electromigration

Ion migration 과 Creep corrosion 의 특징과 차이점

Creep corrosion mechanism 과 고장 사례

Creep corrosion 재현 MFG Test : Telcordia GR-63-CORE Section 5.5

Background on dendritic growth

What is ECM?

Ion migration의 성장 모양 분류와 고장 사례

ECM Video

Ion migration 현상의 판단 기준

Acceleration factors for electrochemical migration

Ion migration 에 영향을 미치는 조건 (재료, 환경, 공정)

각종 금속 재료 및 Solder 합금의 Ion migration

Ion migration의 관찰 및 분석 방법

Ion migration 의 간이 시험 방법 : Water-drop test

Ion migration 의 환경시험 방법 : IPC, JEITA, JEDEC, IEC

온습도 bias 시험

불포화가압시험 (HAST)

호흡작용에 의한 수분 침투

온도변화에 의한 결로

Product qualification standards

Current qualification procedures

Ion migration 의 발생 검출법 (Static & Dynamic 측정법)

Contaminants

What are the sources of contaminants?

PCB의 Ion Chromatography 분석 : IPC-TM-650 Test Method No. 2.3.28

PCB 제조 업체별 contaminants 측정 사례

Ion migration 의 방지법

Why conformal coating? : IPC-2221, IPC-HDBK-830, MIL I-46058C, IPC CC-830

Required performance for conformal coating

Conformal coating specifications

Conformal coating : Physical properties, Electrical properties

Classes of conformal coatings

Conformal coating types and thickness

Why is ECM important?

ECM 의 failure mechanism

EMF series, Pourbaix diagram, Electrophoresis, Rate determining step (diffusion & reaction), Electron shielding effect

Ag migration 사례 분석

Tracking Failure Mechanism

PCB의 연면/공간 절연거리 : IEC 60335-1 Edition 6:2020-09, IPC-2221

PCB의 안전 설계

PCB의 공간거리/연면거리 측정 사례

내 Tracking 성의 계측과 시험법

전해액 적하법 : IEC 60112

고분자 절연재료의 CTI (comparative tracking index : 비교트래킹지수) 와 PTI (proof tracking index : 보증트래킹지수) 측정 방법과 지표 : IEC 60112:2020, UL 746E:2023

내트래킹 지표 : 유리탄소의 생성

LOI (Limiting Oxygen Index) : KS M ISO 4589-2.3, ATSM D2863

Tracking 정의 : KC 60112 (2015)

Tracking 발생 요인

Mechanism in the occurrence of tracking

Tracking과 금원(金原) 현상의 차이점

Solder Joints 관련 고장분석

Soldering의 정의

Reflow soldering 동영상

Wave soldering : Marangoni Effect

Lead-free solder 조성 (상태도, 융점, 물성)

단면기판 wave & reflow soldering 방법

양면기판 wave & reflow soldering 방법

SMD 부품의 solder bridge 방지 설계

Soldering bridge 방지를 위한 dummy land 의 설계

기판의 Hole clearance 기본 설계 : IPC-2222A:2010

표면실장 부품의 고정 접착 공정 및 경화조건

Wave soldering 의 solder bath/pot 불순물 관리 : J-STD-002D:2011

Chip 부품의 Manhattan (drawbridge, tombstoning) 현상 원인

Soldering 판정 기준 (PTH & Solder ball) : IPC J-STD-001D, IPC-A-610E, MIL-STD-883L

Lead Protrusion 및 Clinch 각도 관리기준 : IPC J-STD-001D:2005, IPC-A-610F:2014

Metal Mask 관리기준 및 세척 방법

Solder paste의 교반 조건

SMD 부품의 접착 강도 : JEDEC JESD22-B117B:2020

Solder cream의 구성 요소 (금속성분, rosin, activator, thixotropy, solvent)

Soldering 과정에서 flux 역할 (carboxylic acid)

Flux 규격 : IPC-J-STD-004B:2011

Solderability Test – wetting balance solderability : J-STD-002D:2011, MIL-STD-883L Method 2022.2

Smart Factory : SMT In-Line 구성도

Solderability에 영향을 미치는 인자 (설계, 재료, 공정, 환경)

Soldering 육안 검사 기준

Solder Paste 인쇄 작업 기준

Wave & Reflow Soldering (온도 profiler 및 산소농도 profiler) : IEC 61760-1:2006, IPC/JEDEC J-STD-020E

Manual Soldering 작업 기준

PWA (Printed Wiring Assembly) 출하검사 및 샘플링 검사 : MIL-STD-105E, KS A ISO 2859-1

ICT (In-Circuit-Test) 정합성 관리기준

Pb-free 실장기판의 신뢰성 평가 순서

Solder 접합부의 내구수명시험방법 – Coffin-Manson law : JEITA ET-7407B:2012

Failure mechanisms in solder joints (고장분석 사례 포함)

Non-wetting & Dewetting : IPC-A-600H:2010

Thermal fatigue

Creep & Solder alloy의 homologous temperature

Stress relaxation

Excessive intermetallic growth : Kirkendall Effect

Electromigration

Leaching (Ag 혹은 Cu dissolution)

Failure Analysis Procedure (systematic process)

Initial visual inspection

Electrical testing

X-ray analysis

Mechanical cross-section (X-Section)

Optical examination

SEM & EDS (compositional analysis) examination

Verification of design through FEM (finite element method) modeling

Soldering 업종 공정 실사 평가 (약 200 항목의 check list 에 대한 구체적인 설명)

자재 보관 관리 항목

제전 (ESD/EOS) 환경 관리 항목 및 필수 ESD 점검 check list : JESD625-A (Revision of EIA-625)