NFF (No-fault-found) 의 현상

NFF 의 정의

NFF 의 종류

TNI (trouble-not-identified), CND (can-not duplicate), NTF (no-trouble found), RTOK (retest OK)

Intermittent Failures

The impact of intermittents

NFF test sensitivities

C&E diagram (fishbone diagram)for NFF conditions in electronic products

Characteristics of Intermittent Failures

NFF 발생이 증가하는 원인

An approach to assess NFF

People category

Machine category

Method category

Intermittent failure category
▷ PCB, Components, Connects, Interconnects
▷ C&E diagram (Ishikawa diagram) of intermittent failures in electronic assemblies

NFF 고장 메커니즘

Printed circuit board category

ECM (electrochemical migration)

CFF (conductive filament formation) or CAF (conductive anodic filament)

Via cracking due to environmental stress or manufacturing method

PCB warpage due to CTE mismatch : open trace

Black pad phenomena (ENIG pad finish)

Kirkendall voiding (ENIG pad finish)

Connector category

Galvanic corrosion : Bond pad corrosion, battery spring contact, etc.

Fretting corrosion phenomena

Component – PCB interconnects category

Intermittent failure due to improper Micro-via plating in PCB

Intermittent failure due to open trace in PCB

Inner layer separations or inclusions

Separation or inclusions between plating layers

Solder joint cracks due to thermal cycling or vibration environmental loading conditions

Stress relaxation due to CTE mismatch

High homologous temperature of solder alloys

Component category : IC level or Package level

Intermittent failures due to creep corrosion

Intermittent failures due to tin whiskers

Wire bond lifts
▷ Delamination
▷ Popcorning
▷ IMC growth
▷ Fatigue

Single event upset (SEU)
▷ Soft error

COMS의 Latch-up

MOSFET의 Snapback breakdown

ESD (electrostatic discharge)

HCI (hot carrier injection)

반도체 package의 응력에 의한 leak 불량

Component category : Passive components

Relay on/off 반복동작시 접촉저항 변화에 의한 오동작

Switch 의 접촉저항 변화에 의한 오동작

Switch 의 bounce 및 chattering 에 의한 신호 출력 불량에 의한 오동작

Ceramic capacitor 의 압전효과에 의한 오동작

MLCC crack에 의한 intermittent failure