smt - typical failure analysis and countermeasures

SMT - Typical Failure Analysis and Countermeasures

1.1 Failure Analysis by Process

Failure Symptoms Failure Modes Possible Root

Causes* Verification

Methods

SMT/ Reflow

Short Bridge, Warpage, Pop-corn

Paste print error, placement error

Visual, X-ray, Electrical, Solderability test

Open Miss component, solder, wrong component

Pick and place error, paste print error, Wrong part or reel ID

Non-wetting Solderability of component, PCB and solder paste

Solder paste issue, reflow error, Component or PCB defect

Other SMT failures

Refer IPC-A-610

Solder paste issue, reflow error, Component or PCB defect

Wave Soldering

Open

Missing component, drop off; fluxing, non-wet pad or component.

Component too heavy, improper gluing, fluxing; non-wet pad or component.

Visual, X-ray, Electrical

Short

Solder bridge, contamination/residues, component defect, PCB defect

Improper gluing, fluxing; Component or PCB defect

Underfill/ Adhesive and Cure

Open Weak solder joints, warpage, thermal stress

Improper material, dispense or cure schedule

Visual, X-ray, CSAM, electrical

Intermittent Failure

Weak solder joints, warpage, thermal stress


Short Warpage of board or component


Hand Solder/ Rework

Open

Insufficient solder, cold solder joints, warpage component/PCB, broken PCB trace

Rework process error, too much heat, not enough heat, component warpage, mechanical

Visual, Strain (warpage) measurement, electrical, CSAM, X-Ray, dye

damage, improper moisture sensitive component handling, no solder

penetration, X-section

Intermittent Failure

Cold or cracked solder joint, warpage component / PCB

Rework process error, too much heat, not enough heat, component warpage, mechanical damage, improper moisture sensitive component handling

Visual, warpage measurement, electrical, CSAM, X-Ray, dye penetration, X- section

Short/leakage

Solder mask damage, solder splash, improper flux, contamination, warp component / PCB

Rework process error, too much heat, not enough heat, component warpage, mechanical damage, improper moisture sensitive component handling

Visual, warpage measurement, electrical, CSAM, X-Ray, dye penetration, X-section, Ion Chromatography

ICT/Functional Test

Open

No solder joint, broken solder joint, component defect, PCB defect

Overload, component or PCB defect, SMT assembly error

Visual, CSAM, X-Ray, Dye penetration, X-section, Decap, Strain measurement

Intermittent failure

No solder joint, broken solder joint, component defect, PCB defect

Overload, component or PCB defect, SMT assembly error

Visual, X-Ray, Dye penetration, X-section, Decap

Short/leakage

Solder bridge, contamination/residues, component defect, PCB defect

Pick and place error, paste print error, contamination at SMT assembly/rework area, component fab/test/tape and reel process

Visual, X-Ray, dye penetration, X-section, Decap, IC, FT-IR, SEM/EDX

Burn-in Test/ Reliability Test

Open Solder joint crack, lead lifted

Overload, fatigue, component or PCB defect, SMT

Visual, X-ray, X-section, Dye penetration

assembly error

Lead break, package failure (wire bond, delamination)

Overload, fatigue, component defect, SMT assembly error

X-ray, CSAM, X-section, Dye penetration, Decap

PCB failure PCB defect, moisture/blister delamination

X-ray, CSAM, X-section, Dye penetration


Solder joint crack

Overload, fatigue, component or PCB defect, SMT assembly error

Visual, X-ray, CSAM, Test under hot/cold, pressure

Package failure (physical or electrical)

Popcorn/delamination

Visual, X-ray, CSAM, Test under hot/cold, pressure

PCB failure PCB defect, moisture/blister delamination

Visual, electrical, X-ray

Short/leakage

Solder bridge; Solder ball and flux contamination;

Paste print error, placement error, improper rework process, pad design electromigration

X-ray, Visual, Electrical

Electro migration or dendrite grow

X-ray, Visual, Electrical, FTIR, IC, SEM/EDX

Customer/Field Return

Open

Damaged parts / boards/ connectors

Assembly damage, abusive handling

Visual, Check marking, seals, evidence of excessive heating, contaminants, cracks, etc.

Component malfunction

Component defect, ESD damage, thermal damage, abusive handling

FCT @ room, cold or hot temperature

Cracked solder joint

Fatigue, overload, abusive handling, SMT/component/PCB defect

Visual, X-ray, dye penetration, X-section and FCT

Burnt component Thermal damage, ESD damage,

Visual, smell, FCT

abusive handling

Corrosion of trace/ pin

Contamination, electromigration

Visual, FT-IR, IC, SEM/EDX





Thermal stress

Component defect, ESD damage, thermal damage, abusive handling

FCT under heating, heat gun, cooling gas

Solder joint crack

Fatigue, overload, abusive handling, SMT/component/PCB defect

Visual, X-ray, Dye penetration and X-section, FCT, HALT, vibration

Component malfunction

Thermal damage, ESD damage, abusive handling

FCT @ room, cold or hot temperature, X-ray and CSAM, Decap and electrical probing

Corrosion/ Contamination of trace or pin


Visual, FT-IR, SEM/EDX

Short/leakage




Component leakage Contamination, electromigration

Electrical test for the component

Corrosion/ Contamination of trace or pin


Visual, FT-IR, IC, SEM/EDX

Note: * One or more factors can contribute simultaneously to a root cause.

1.2 Failure Analysis by Material/Location

Materials Failure Modes

Symptoms Possible

Root Causes*

Verification Methods

Possible Solution

s

SMT Related*

Miss solder/ insufficient solder

Visual and electrical failure (open/short)

SMT process error, clogged aperture, paste issue

Visual including optical

measuring and X-ray

SMT Process Control

Miss component

Pick and place error

Wrong/ damage component

Pick and place error, wrong reel ID or component part

Bridge Print process or placement error

Excessive solder

Print process error, damaged stencil, dirty stencil, poor/no PCB support plate

Misalignment

Placement error or component issue

Component

Delamination Open

Moisture sensitivity or component adhesion failure, reflow process error (too hot)

CSAM, X-ray, X-sectioning

Moisture handling

Cracking (component/die)

Visual failure, open

Assembly damage at SMT or component fab/test/tape and reel

X-ray, C-SAM

Component handling, moisture and thermal stress

Damaged component

Open, short

Cracking, handling damage/tape and reel issue, lead skew/bend

Visual Replace component

Electrical fail Open, short Component fab or design

Electrical test Replace component

Wire bond crack/break/lift

Open, intermittent failure

Contamination, improper bonder setup, popcorn, thermal damage, fatigue

X-ray, Decap Wirebond process

Popcorn Open, short

Moisture sensitivity or component adhesion failure, reflow process error (too hot)

C-SAM, X-ray, surface scan

Moisture handling

Contaminated lead

Intermittent failure, open

Contamination at SMT assembly/rework area, component fab/test/tape and reel process

Wetting balance, Solderability test, FT-IR

Clean, replace component

Warpage Open, short

Moisture sensitivity or component adhesion failure, reflow process error, component package defect

Surface scan, visual gauge

Reflow profile, replace component

Coplanarity Open

Handling damage/tape and reel issue, or improper lead form

Visual

Replace component, add more solder paste

Interconnection

Joint crack Open, visual

Overload, fatigue, component, PCB and SMT defect

Visual, X-section, Dye penetration

Replace PCB and component, revise reflow profile

Weak solder joint

Visual

Assembly process defect, component or PCB defect

Pull test

Change stencil design, fix individual defects

Interface failure

Open / intermittent

Contamination, assembly defect, component or PCB defect

Vibration, Temperature baking, Dye penetration

Replace PCB or component or modify process

Excessive void

Open

Contamination, reflow process error, solder paste issue, design related

X-ray, X-section

Change solder paste, reflow profile, design, moisture

Voiding or delamination in adhesive/underfill

Voiding, uncure, low adhesion

Contamination, dispense error, cure error, material issue

C-SAM, X-ray, X-section, SIR

Materials handling

Wrong flux/paste

Short/leakage

Process setup error

Visual, Ion Chromatography, SIR

Cleaning and rework process control

Wrong Reflow Profile

Visual, open Process setup error

Visual, X-ray Rework

Decolorizing Contamination, oxidation

Contamination, process error, abuse

FT-IR, Auger, X-section, XRF

Reflow profile, check component plating

PCB Trace/via/through hole crack

Open

PCB assembly defect, thermal or mechanical

Visual, X-ray Replace PCB

overload

Trace/pattern defect

Short/leakage

PCB assembly defect

Visual, X-section, X-ray

Replace board

Contaminated board

Open, intermittent failure

PCB fab process error, handling/storage, SMT process error

Wetting balance, Solderability test, FT-IR, X-section

Clean PCB, board handling

Black pad Open, intermittent failure

PCB fab process error

X-section, dye penetration, SEM/EDX and pull test

Check PCB plating

Solder mask defect

Bridge, open, intermittent failure

PCB fab process error

Visual, X-section

Replace PCB

Warpage Open, short

PCB fab process error, SMT process error

Visual, surface scan

Check PCB and handling

Poor wettability

Open, visual reject

PCB fab process error, SMT process error, solder paste issue

Visual, X-section, Solderability test

Clean or replace PCB

Over/under etch, non uniform thickness

Open PCB fab process error, design issue

Visual, X-section

Replace PCB

Delamination Open, visual reject

PCB fab process error, design issue

Visual, X-section

Replace PCB

Pad misregistration

Open, visual reject

PCB fab process error, design issue

Visual, X-section

Replace PCB

Design error Open, short Design issue Visual, X-section

Rebulid PCB

Note: * One or more factors can contribute simultaneously to a root cause.

1.3 Typical Failure Analysis Flowchart

1.3.1 Typical Deep Dive Failure Analysis Flowcharts

1.3.1.1 Deep Dive FA Flowchart (Overall)

Identify Category of Candidate for FA

Manufacturing Failure

Field Return ORT/ Specific Test/Eng. Evaluation Failure

Data Mining - Failure Pareto - Repair Pareto - Trend Chart

Database

Data analysis and correlation study - Process mapping - Failure correlation - Initial failure categorization - Pattern analysis


Data analysis and correlation study - Manufacturing data vs. Field return correlation - History data review - Escapee /NTF review - Defect repeatability - ORT Input - Correlation study

- Process mapping - Failure correlation - Initial failure categorization - Pattern analysis


Data analysis and correlation study - Manufacturing data vs. ORT failure correlation - History Record review - Manufacturing parameter/CP/CPK/Spec review - Pattern analysis

Test/ Software

Design related

Process/ Workmanship

Component

Possible root cause analysis (Level 1) / Prioritization - Fishbone for each failure - DFMEA/PFMEA - Risk analysis - Prioritization

A

Refer to 7.3.1.4 Refer to 7.3.1.2 Refer to 7.3.1.3 Refer to 7.3.1.5

Failure

1.3.1.2 FA Flowchart for Test Related Failure

Test/Software

DOE for test

Confirm abnormality

Yes

Raise to TE

Yes

No

TE Confirm SW related

Yes

Test Suite update

Improved?

Verify improvement - Trend chart - Pareto review

Yes

Review effectiveness of DOE

No

Test suite related?

No

Yes

Go back

to A

No

Go back

to A

Close

Re-confirm test/ SW related

1.3.1.3 FA Flowchart for Component Related Failure

Component

Component Module

*Work together with supplier and component team in customer for consign and strategic parts to confirm the failure and root cause (Deep Dive and FA)

Possible root cause analysis /Prioritization

- Fishbone for each failure - DFMEA/PFMEA - Risk analysis - Prioritization

Component related

Design related

Process related

Test /SW related

PowerSupply Related?

PCBA Related?

Mechanical parts Related?

Electrical/Electronic parts Related?

Optical electrical parts Related?

No

No

No

Work with the 2nd tier supplier on Deep dive and further FA

Refer to 7.3.1.4 Refer to 7.3.1.5 Refer to 7.3.1.2

No

Go back

to E

No

Yes

Yes

Yes

Yes

Yes

C E

1.3.1.4 FA Flowchart for Design Related Failure

Design related failure

Component Test System Test Environment / Field

2nd level study further brainstorming, analysis and experiment based on the 4 items as below:

Component quality: - Design margin too tight; - Supplier control system issue - Test method is different - Reliability is not characterized - Not compliant to the manufacturing - Not compatible in the system etc

Design failure verification test

Yes

Proposal for design change (component process/ test)

Design change/ ECO

*Work in conjunction with customer

Test related - Test setup is not appropriate - Test coverage is not 100% - Some item is not testable - Test environmental is change Software issue

System related - Design limitation by individual failure risks - Random failures is not understood - Process impact is not well calibrated - Component interference issue

Test Environmental/Field - Test/field environmental was not clear statistically - Test/field conditions changed

Improved?

Yes

No

Customer to verify approve

Verify improvement - Trend chart - Pareto review

Yes

No

Go back

to A

Close

Positive result?

1.3.1.5 FA Flowchart for Process/Workmanship Related Failure

Process/ Workmanship

PCBA Failure Box build Failure

No

Improve incoming material dimension Dimension

Related?

Yes

Improved?

Yes

Assembly related?

Improve process

Environmental related?

No

Go back to A

Improve environment

No

Yes

Yes

No

Close

B

1.3.1.6 PCBA FA

Electrical open/ short/ abnormality? Use multimeter or other test equipment

Visual inspection at 5X-50X Document as received condition of test samples record all identification markings, serialize Failure Detected?

Retest ICT Test Function Failure Duplicated?

Yes No

Yes No

X-ray inspection for hidden solder joints and related components and PCB traces Failure Detected?

Document defect Photomicrographs determine possible causes

TDR, Probe test under hot or cold temp. or Pressure Failure Detected?

No Yes

Replace the suspect component 1 by 1 Failure Detected?

Report Findings

No Yes

No Yes

Fails at ICT Return to verify electrical open /short and Test Hot/Cold or with slight pressure

No Yes

Document Defect

Corrective measures implement & verify effectiveness

Debug PCB pad /trace/via/hole solder mask Failure Detected?

Component Identified Submit to Vendor

Root Cause FA on Component

B

Detailed PCB FA methodology

1. Submit to PCB vendor 2. Report

D

C

1. X-ray and C-SAM delamin /die crack/wire break 2. Decap and probe (detail see FA for Component

1. Possible solder joint failure 2. Submit to FA lab for destructive tests

Document Defect

Corrective measures implement & verify effectiveness

Report Findings Corrective Implement & verify effectiveness

1.3.1.7 Component FA

Yes


Document Defect

C

Yes

Yes No

No Yes

No Yes

No Yes

No

No

Visual Inspection-Failure Found? (Stereo Microscope 5X-50X Document as-received condition of test samples Record all identification markings, serialize)

Visual Inspect Record test results

Decapsulation /Cross section disassembly of package

Internal Inspection-Failure Detected? (Stereo microscope 5X-50X Compound Microscope50X-2000X SEM 10X-100,000X)

Document Internal Characteristics Photomicrographs

Electrical microprobe use probe station and multimeter or curve tracer

Probe test external lead to associated bond pad and to ground and Vcc Failure Detected?

Probe test and pad to bond pad Failure Detected?

Wire bond strength test Non-destruct pull test destructive pull test ball bond shear test

Document Defect Device delayering may be required to determine root cause

Re-Test Hot and cold and/or with power applied to Vcc pin and ground GND pin.

X-ray radiography Open/Short Verified?

C-SAM verify package integrity Failure Detected?

Document Defect

Request further component debug

Electrical Open/ Short/ Abnormality Verified? (Use Multimeter, RLC bridge and/or curve tracer, record rest results, compare with known good part Obtain component specification) (Level 2 or 3 study)

Document Defective areas Photomicrographs Determine possible causes

Document Defect

Yes No



Report Findings Corrective Implement/verify effectiveness



1.3.1.8 FA for BGA Solder Joint Crack

Go back to

B

Visual inspect. at 5-50X (where?)

Electrical Probe (Open?)

Data collection: Sample condition / loading history Failure rate, location and symptoms Reflow profile and PCB and Component Info, etc.

PCB check (plating & thickness, pad design)

PCB & Assembly processes are OK?

Component (e.g. size, type)

SMT Process Workmanship

Warpage (during reflow) Coplanarity

Overstress? (ICT, press fit, handling)

Reflow profile

Dye Penetration Pull Test

Failure modes

Visual inspect. Black pad? Wetting defect?

Yes

No

X-section SEM/EDX

X-section SEM /EDX

No

Close

Cracked at PCB pad interface? (BGA is OK?)

Effective?

D

Yes

* (Level 2 Study)

1.3.2 Failure Analysis for Electrical/ ICT/ Function Open/ Short

Electrical open/ short? (Multimeter or probe)

Visual inspection at 5-50X Ersascope

X-ray inspection (hidden joints, Component& traces)

Electrical Probe Under hot, cold or pressure

Retest ICT Failure duplicated?

Go to component FA if no failure

Dye Penetration Pull Test

X-section SEM/EDX

Y

N

N

Y

N

Y

SOLDER JOINT FA

Component check (warp., standoff, etc.)

Assembly status Failure modes/Quantity SMT Reflow/ printing Board Handling ICT/FCT

N

®

Swap Components (use known-good component)

Failure Fixed?

Removed Component Fail? (CSAM, reball & replace or test by supplier)

N

Y

®

Visual (crack, contamination) for bare board Pad/trace/via/hole

Electrical Probe

PCB FA

X-section, FT-IR, Metrology, SEM/EDX

Failure Detected?

N

N

Y

*Note: Step may go earlier before; for failures from prototype, burn-in, mechanical and reliability

tests.

Start

Report/ Corrections End

®

smt - typical failure analysis and countermeasures

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