Non-destructive Analysis

Techniques for Advanced Package

Dr. Chih Hsun Chu, CTO

Materials Analysis Technology Inc.

Content

• Introduction of package trend

– Complex routing

– Multi-chip and incorporating passive components.

– 3D structure

• Advanced non-destructive failure analysis tools

– 3D X-ray microscope

– Scanning acoustic tomography (SAT)

– Lock-in thermography

– Time domain reflectometer (TDR)

• Examples of failure cases

• Summary

Why go for 3D package?

• Performance driven

– Higher speed, complex function

– Global wires length reduction

– Clock frequency increase

– Power reduction

– Better noise performance

• Real estate driven

– Thinner

– Smaller

New Challenges of Failure Analysis

• Previous, simple connection

between lead frame to chip

• Now, complicated routing,

stacking, and passive

components embedded.

3D X-ray microscope image of a small PCB module

Top view X-ray image of a stack die package Cross sectional view X-ray image of a stack die package

Tilted view X-ray image of a simple package

Advanced Non-destructive Analysis Tools

• 3D X-ray microscope

• Scanning acoustic tomography (SAT)

• Lock-in thermography

• Time domain reflectometer (TDR)

Comparison among Tools

TDR Thermal Emission

SAT X-ray

Microscope

Stimulus Electric Electric Acoustic X-ray

Delivery Electrical

wires Electrical

wires Water Air

Direct contact

Yes Yes No No

O/P form Reflection

profile image Image Image

Failure location

Good Good Good Good

Spatial resolution

~ 1 mm 15 um/pixel ~ 5 um 0.7 um

3D X-ray Microscope

• Below um spatial resolution (0.7 um)

– Two-stage magnification system

• First stage: Geometric magnification

• Second stage: Optical magnification

• 3D tomography

• Composition contrast

• Phase contrast to differential light element

Scanning Acoustic Tomography (SAT)

• Reduced edge effect

• Improved spatial resolution

• Enhanced penetration capability

Lock-in Thermal Emission Microscope

• Abnormal current

generates power

dissipation and raises

the temperature

• Heat diffuses to the top

surface of a package

• Long wave-length IR

detected by the InSb

camera

Time Domain Reflectometer (TDR)

• From final test to obtain the failed pin/solder ball

• Narrow down the location of the failed electrical

path from the failed pin/solder ball

• Using X-ray to focus on the TDR indicated failure

location

Examples of Failure Cases

• Open

– TDR to narrow down the failure location and followed

by 3D X-ray microscope investigation

– SAT localization and followed by PFA investigation

• Short

– Lock-in thermal emission microscope followed by 3D

X-ray microscope or PFA

• Wire to wire bridge

• Wire to wire short by large particle

• Trace to trace short by Nano Particle inside PCB

Crack of the PCB Trace

Delamination of MEMS

normal

peeling was found

Delamination of Cu Pillar

Location: X2 Location: X3

% of delaminated area

X1: 15.1 % (dark)

X2: 100.0 % (grey)

X3: 40.2 % (gray)

Location: X1

Wire to Wire Short

• Pin to pin short

identified by I-V

• Thermal emission

microscope to

localized the short

X-RAY Radiography

Wire to Wire Short

Hot spot area.

Wire to Wire Short

• Reconstructed

3D X-ray

image

Wire to Wire Short

Wire to Wire Short

Wire to Wire Short: Large Particle

• I-V shows pin to pin short

• Thermal emission microscope locates hot spot

Wire to Wire Short: Large Particle

• Partial removal of top molding

Wire to Wire Short: Large Particle

• Reconfirm the hot spot by thermal emission

microscope

Wire to Wire Short: Large Particle

• Cross sectioning at the hot spot

• Large particle containing carbon was identified

by SEM/EDX

Nano Particle inside PCB

• Impendence was measured from failure dies

Nano Particle inside PCB

• Hot spot detected by OBIRCH

Nano Particle inside PCB

• Cross sectioning across the hot spot area

• Nano particles (Au, Ni, Cr) were found by

TEM/EDX

Summary

• Advanced non-destructive analysis tools were

successfully utilized to investigate package

process resulted failure

• Combining usage of different tools is necessary

to find the failure site and localize the fault

• When chip function is recovered after decap of

the package, non-destructively analysis the

failure part before decap provides the evidence

that either the failure is due to the abnormal

packaging process or incompatibility of the

package materials.