Introduction:
Failure analysis is the process of investigating the failure for the purpose to identify the failure mode and failure mechanism. The results then were used to improve and to produce necessary input to improve the process and to prevent the failure to be re-produced.

Basically the analysis divided into two categories as below:

Non Destructive Test:

Generally it means the analysis or the inspection done on the sample or product did not damage or change the characteristic of the product itself. In other words, the sample or the product still useable after the analysis has been done. Below are the lists of the analysis which can be done under this category

Destructive Test:

Processes whereby the sample will be analyze with the method which can be damage the cosmetic condition of the sample. Sample could not be used after the process.

NON DESTRUCTIVE TEST
EXTERNAL VISUAL INSPECTION

Visual inspection is referring to the process of validation from any defects on the exterior site. Commonly the inspection will check for any cosmetic defects whereby the defect might be influence to the Failure Mode. Normally the basic reference standard is referring to the IPC and JEDEC specification. For the others product than IC, the reference normally will be used known good sample to compare on the bad part. Hence any abnormalities upon the inspection will be considered as findings.

In most of the case, the visual inspection was done in a low magnification which is around 5X – 60X. However, in the case of required confirmation, High Power Scope or SEM might be using to re-confirm on the defects.
This process is considered very important and critical since some of the defects part is actually found to be externally having a defects. As example, whisker on the lead may cause to the short failure and corrosion on the lead contact may cause to the open or electrical parameter failure.

Below are some of the images of the defects observed upon the visual inspection:

Solderability Condition on Lead Side:   


Visual Inspection on Package Level:

NON DESTRUCTIVE TEST
2D XRAY INSPECTION

X-Ray Radiography inspection is one of the non-destructive techniques to inspect and analyze the interior part of the component. The inspection produces early input on how the condition looks like on the sample itself. Some of the sample, the root cause of the failure will be easily detected upon the inspection by X-Ray. Since, it’s non-destructive test method, the inspection can go to a large number of sampling and it’s really helpful to do screening process.

It operates on the principle of dissimilar transmission of X-Rays through different materials.  The ability of a material to block X-Rays increases with its density. It is this dissimilar transmission of X-rays through different materials that is utilized to create an image of various contrasts.

Below are some of the examples of the X-Ray Capability:

1. Die and Wire Bond Defect Inspection:
2. Internal Package Crack Inspection
3. Die Attached Inspection
4. EOS/ESD Burn Mark Inspection
5. Mold and Die Attach Void Inspection
6. BGA Solder Ball Void Inspection

NON DESTRUCTIVE TEST
SAM [SCANNING ACOUSTIC MICROSCOPE]

Scanning Acoustic Microscopy [SAM] is a failure analysis used to detect delamination or disbands between the package interfaices. For example, interfaces between the die and plastic compound, between the leadframe and compound. Etc [Refer Illustration diagram below for more details].
                          
It basically consists of sending a sound wave through the package, and interpreting the interaction of the sound wave with the package.  A typical scanning acoustic microscope may employ either pulse echo or through transmission inspection to scan for disbonds or delaminations.  Pulse echo inspection consists of interpreting echos sent back by the package while through transmission inspection consists of interpreting the sound wave at the other end of the package, after it has passed through the latter. The ultrasonic wave frequency used ranges from 5 to 150 MHz.

NON DESTRUCTIVE TEST
CURVE TRACE TEST
Curve tracing is the process of analyzing the current-voltage characteristics of an electrical path. The curve trace equipment normally been used to do this activity by probing two pins [normally between the ground and tested pin] to determine the behavior of the current as the voltage is varied. Below some of the example images, obtained from the curve tracer.

Curve trace is useful to verify the failure pins and this information is normally very important to perform the next step of the analysis.   

Below are some of the images of the curve tracer output

DESTRUCTIVE TEST
CHEMICAL DECAPSULATION
Decapsulation is a method to expose the internal part of the component by chemical methods for IC and BGA component or by mechanical method for the hermetic known as delidding or decapping.

Upon completion of the Decap, the samples are being able to inspect for any evidence of defect or damage on die or wire structure. The inspection later will provide the root cause of the failure or defect based on the evidence seen on the sample itself.

Below are the images of the decap sample:

DESTRUCTIVE TEST
CROSS SECTION ANALYSIS
Cross-sectioning or microsectioning is a failure analysis technique for mechanically exposing a plane of interest in a die or package for further analysis or inspection.

The process of cross sectioning normally involves few steps as below:


Example of Cross Section Images

DESTRUCTIVE TEST
DYE & PRY ANALYSIS
Dye and Pry Testing applied to the component for the purpose to check for the any sign of micro crack on the solder joint especially for the BGA, Leadless such as QFN and others SMT product. The sample will be place on the vacuum environment in order to get the Dye to penetrate on the pre-existing crack if there is. By doing this method, we can observed the crack or solder ball defect call HOP [Head On Pillow] present.

Below are some of the images after the dye penetration test:

DESTRUCTIVE TEST
HOT SPOT DETECTION
One of the fundamental truths of electronics is thus: all devices generate heat to some degree. Some heat emitted by devices is normal – after all, millions of transistors, switching off and on millions of times a second, will consume sizeable amounts of power and therefore produce a considerable amount of heat. However, there are certain types of defects that increase power consumption, thereby increasing the amount of heat given off by a device. While this additional heat is immaterial to the engineering team responsible for the design and production of a device, it can provide a useful avenue for isolating the item that they’re truly interested in – the defect itself. Using thermal emission microscopy, slight differences in temperature can be turned into useful data about a device, enabling a failure analyst to drive to the heart of a defect and determine the root cause of failure.

DESTRUCTIVE TEST
CROSS SECTION ETHCING
Metallographic Etching encompasses all processes to reveal particular structural characteristic of a metal which could not be revealed after the polishing.

Below are the images of the samples after the etching process:

DESTRUCTIVE TEST
SEM INSPECTION & ANALYSIS:
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition. The electron beam is scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens can be observed in high vacuum in conventional SEM, or in low vacuum or wet conditions in variable pressure or environmental SEM, and at a wide range of cryogenic or elevated temperatures with specialized instruments.

1. All Conductive material inspection analysis
2. Wire Bond  in Electronic Component
3. Cross Section Inspection.
4. Metallurgical sample
5. Non Conductive material inspection such as rubber and plastic
6. Surface contamination analysis
7. Non organic contamination analysis
8. Chemical Compound analysis.
9. Metal Structure and Gain Boundaries inspection

Benefit Of the Process:

1. Clear images provided for the analysis purposes.
2. Not limited to only inspection but also analyzing others element factor causing to the failure.
3. Guide to problem solving with the proper evidence visualize.
4. For EDX, first step of identifying the contamination.
5. Tools of problem solving upon Failure Analysis investigation.

Example Of SEM – Solder Ball Condition on BGA Products
Inspection of the solder ball condition:  SEM was used to inspect the severity of the Crack and void damages. This image for example shows how the crack was happen propagating from one end to the other. Others information can be gathering from these images are how the internal void pattern and in most of the case we also can see a very clear image of the intermetallic formation.



Example Of SEM – Gold Wire Condition on IC Product
Inspection on the Gold Wire Condition on IC Package

Wire bond inspection, in most of the time required high magnification for the inspection.  Inspection under 1000X Magnification of Optical High Power Scope, normally unable to conclude any findings which will help the FA team to drive the root cause of the failure. Whenever FA team unable to give solid evidence, hence the case might be repeated due to improper solution given.

Below are some of the images of SEM on wire bonding.

Example Of SEM – Solder Fills and Solder Condition on Lead:
SEM image, inspection on the solder fills and solders condition on the lead.  Inspection normally focus on the percentage of the solder fill up and solder coverage. Limitation on the optical scope such as blur image, over contrast and brightness, light reflection will be solve by using the SEM inspection. Below images shows how the perfect cross section on the PTH and Lead shows the solder coverage.

DESTRUCTIVE TEST
EDX ANALYSIS
Energy Dispersive X-Ray Analysis (EDX), referred to as EDS or EDAX, is an x-ray technique used to identify the elemental composition of materials.

Example of the EDX Output
Most common analysis can be performed is the Mapping and Point Analysis.
Below images show the Mapping technique and the spectrum shows the Point Analysis End Results.

DESTRUCTIVE TEST
FTIR ANALYSIS
FTIR (Fourier Transform Infrared) Spectroscopy, or simply FTIR Analysis, is a failure analysis technique that provides information about the chemical bonding or molecular structure of materials, whether organic or inorganic. It is used in failure analysis to identify unknown materials present in a specimen, and is usually conducted to complement EDX analysis.
    
The technique works on the fact that bonds and groups of bonds vibrate at characteristic frequencies. A molecule that is exposed to infrared rays absorbs infrared energy at frequencies which are characteristic to that molecule. During FTIR analysis, a spot on the specimen is subjected to a modulated IR beam. The specimen's transmittance andreflectance of the infrared rays at different frequencies is translated into an IR absorption plot consisting of reverse peaks. The resulting FTIR spectral pattern is then analyzed and matched with known signatures of identified materials in the FTIR library.

DESTRUCTIVE TEST
FOCUSED ION BEAM
Focused Ion Beam (FIB) techniques are used in a variety of applications.  In terms of failure analysis, FIB techniques are commonly used in high magnification microscopy, die surface milling or cross-sectioning, and evenmaterial deposition.
A FIB system works very similarly to a scanning electron microscope, except that it uses a finely focused beam of gallium (Ga+) ions instead of the latter's use of electrons.    This focused primary beam of gallium ions is rastered on the surface of the material to be analyzed.  As it hits the surface, a small amount of material is sputtered, or dislodged, from the surface.

The dislodged material may be in the form of secondary ions,atoms, and secondary electrons.  These ions, atoms, and electrons are then collected and analyzed as signals to form an image on a screen as the primary beams scans the surface.  This image forming capability allows high magnification microscopy.

The higher the primary beam current, the more material is sputtered from the surface.  If only high-mag microscopy is intended, only a low-beam operation must be employed.  High-beam operation is used to sputter or remove material from the surface, such as during high-precision milling or cross-sectioning of an area on the die.

DESTRUCTIVE TEST
XPS ANALYSIS
Electron Spectroscopy for Chemical Analysis (ESCA) or X-ray Photoelectron Spectroscopy (XPS) is a failure analysis technique primarily used in the identification of compounds on the surface of a sample.
 
It utilizes X-Rays with low energy (typically 1-2 keV) to knock off photoelectrons from atoms of the sample through the photoelectric effect.  The energy content of these ejected electrons are then analyzed by a spectrometer to identify the elements where they came from.
      
The incident X-Rays used in knocking off the electrons must possess energy that is both monochromatic and of accurately known magnitude.  The X-ray source material must also be a light element since X-ray line widths, which must be as narrow as possible in ESCA, are proportional to the atomic number of the source material. It is for these reasons that commercial XPS systems typically use the K-alpha X-rays of aluminum (Al K-alpha E = 1.487 keV) and magnesium (Mg K-alpha E = 1.254 keV).
         
Although the X-rays penetrate deep into the sample, only the electrons on the surface of the sample are able to escape without significant loss of energy for analysis. As such, ESCA, just like AES, is basically a surface analysis technique.

DESTRUCTIVE TEST
COUNTERFEIT INSPECTION / ANALYSIS
Counterfeiting becomes profitable when scrapped components, components from recycled products, or inexpensive components can be “remarked” and sold as a new, more expensive, higher reliability version. Reasons for the proliferation of counterfeiting include profitability, the low probability of being caught, and the exporting of US electronic waste for disposal in poorer countries.

External Visual Inspection involving below activity: