failure analysis introduction - isu.edu.t · pdf filepresented by ase confidential /...

Presented by
ASE Confidential / SecurityASE Confidential / Security--BB
Curtis Chen ASE GroupNov. 17, 2009
Failure Analysis Introduction

2 ASE Group. All rights reserved.ASE Group. All rights reserved.
Content
0. Key Concepts for failure analysis
1. Necessary Data for FA Analysis
2. Failure Analysis Flow
3. Failure Analysis Equipments/ Functions

0. Key Concepts for failure analysis
0.1: ()
0.2: ():////
///;;;-
---..
0.3: ()
0.4: (;plan)
0.5: (; do)
0.6: (;check)
0.7: (co-work)
0.8: (action)
0.9:

HTST (1) 150oC, 168hrs
Function test (2)
HTST (2) 150oC, 500hrs
Function test (3)
HTST (3) 150oC, 1000hrs
Function test (4)
Function test (1)
Short failure was detected for 1 ea
Short failure was detected for 1 ea
Passed
Passed
Customer : XXX
Package : STK TFBGA XXX L
Failure Point: after HTST 500/ 1000hrs
Failure Mode: gold ball short to exposed Al pad
Evidence:
Why it can escape twice test?
VSS
PIN J13
IMC
ASE confidential ASE Group. All rights reserved.ASE Group. All rights reserved.

ASE Confidential / SecurityASE Confidential / Security--BB ASE confidential ASE Group. All rights reserved.ASE Group. All rights reserved.
FIB cutting on the failed unit after HTST
Gold ballGold ball
Al padIMC IMC
Continue FIB cutting,then found the IMC growth had over the edge of adjacent pad.
The edge of Al pad

ASE Confidential / SecurityASE Confidential / Security--BB ASE confidential ASE Group. All rights reserved.ASE Group. All rights reserved.
There was still a gap (voids and Al oxide) between extruded Al and its adjacent Al pad, hence no short failure occurred.
FIB cutting on the passed unit after THT
Gap
Gap

(1) After assembly, ball shift had occurred. Al metal was extruded out, and almost connected with adjacent Al pad.
(2) IMC growing during HTST
(3) IMC crossed the adjacent bond pad to cause the short failure.
Failure mechanism
ASE confidential ASE Group. All rights reserved.ASE Group. All rights reserved.

1. Necessary Data for FA Analysis
a. Confirming the failure symptom at the beginningb. More correct history input is necessary to come out right
conclusionc. Necessary tools for the electrical traceability during
failure analysis
Why we need it?

Necessary Data for FA Application
Failure mode
Relevant data Necessary Option
eFA application/Request form
VBe sure to obtain approval form your manager or supervisor forurgent case. Remember to attach all the drawing files.
Clear History V1. Failure after assembly or reliability test (what's the testcondition) or SMT (what's the reflow profile)
B/D drawing V1.Complete and clear wire bonding drawing.2. Identify the power and ground ring.
Substrate drawing V Complete and clear substrate drawing (autoCAD format).
Failure pin V
1. If you can not provide a good sample for comparison, then youmust provide failure pins.2. If the customer has provided net name of the failure pin, therequestor will need to provide netlist for comparison.
Good sample V For comparison.
Net list V
1. For real die package.2. The data should include net name / finger no. or bonding padno. / solder ball no.3. Transfer the failure pin from solder ball to finger of B/Ddrawing.
Checking PointO/S Fail

B/D Drawing Substrate Drawing

Note: 1. If the package is daisy chain design, pls mark it in the request form.
2. If the wafer is CUP (circle under pad) design, pls mark it in the request form.
3. If the failure pin is provide by customer/test house, pls provide a file that can be used to transfer thefailure location from test name to solder ball/finger no.4. Please feel free to contact us if you have any question while you apply a FA case, June Shyu (83773),Jetter Tseng (83754)
Failure mode
Relevant data Necessary Option
Daisy chain designwithin the package
V For daisy chain design package, confirm the daisy chain layout.
electrical testcriteria
V For comparison.
Bare substrate V for TDR
Please refer to SPEC no. 62-21-0000-0026 Failure analysis guidline
Checking PointO/S Fail
Necessary Data for FA Application

2. Failure Analysis Flow
Failure analysis entrust
Data correct/failure confirm?
Failure analysis
Failure mode identification
Result/Report issue
Yes
No
No
Yes
Improvement (own by CQE)
Non-destructive analysis
Destructive analysis

Non-destructive analysis items are aimed to collect as much information as possible prior to any destructive actions and are applied where appropriate analysis method is defined as item below:
Non-destructive analysis
a. External visual inspection
b. Electrical verification
c. SAT inspection
d. X-ray inspection
e. SEM inspection

External visual inspectionThe exterior features of the samples shall be checked under low power/ high power optical microscope for any visual defects.
Electrical verificationThe sample shall be subjected to electrical verification to confirm electrical failure.
SAT inspectionThe sample shall be subjected to SAT inspection to check for any possible delamination cracking or voiding problems.

X-ray inspection
The sample shall be subjected to x-ray inspection to check for any obvious defect within the package.
SEM inspection and EDS analysis
In order to detect smaller defect mode, SEM/EDS were used to get higher resolution images and composition analysis to get more solid evidences for failure modes identification.

Destructive analysis items are aimed to collect as much hard evidence as possible to support the final conclusionAnd are applied where appropriate analysis method is defined as item below:
Destructive analysis
a. Isolation test
b. Chemical de-capsulation
c. Horizontal cross-section
d. Vertical cross-section
e. Dry or Wet etching

Isolation test
This process involved techniques that allow the identification of the electrical failure location. Based on substrate and wire bonding information, substrate copper trace or gold wires can be sectioned to isolate whether the failure is located on the die side or the substrate/lead frame side.
Chemical de-capsulationThis process removes the portion of compound covering the wire-bonding and die area for all wire-bonding packages using fuming nitric acid and/or sulfuric acid.

Horizontal cross-sectionIn-plane cross-sectional techniques that is useful to check for copper traces and solder extrusion types of failures.
Vertical cross-sectionCross-section that is performed perpendicular to the package. Useful to check for gold balls, wires, stitch bonds, substrate via/through holes, solder bumps, and layer structure types of failure inside package.
Dry or Wet etchingThese techniques include passivation removal, solder mask removal, compound removal, underfill removal, cratering test, solder bump/ solder ball etching, metal materials etching, etc.

3. Failure Analysis Equipments/ Functions
Item Analysis item Function
1 Optical microscopeThe

failure analysis introduction - isu.edu.t · pdf filepresented by ase confidential /...

Documents