Construction analysis is the investigation of the construction quality and materials used in the manufacture of an electronics component. A construction analysis is performed when we are having doubts about the authenticity of a component (prevent counterfeiting), to ensure that the construction of the components is reliable or to help understand a failure of the component (also known as failure analysis).
Construction analysis performed for Watt & Well answer to the military specification for test method standard STD 1580 and the ESA standard: ECSS-Q-ST-60-13C. There are both destructive and nondestructive analysis sequences.
The sequence of a complete construction analysis might slightly defer if the component’s the die is sealed in plastic resin or airtightly sealed in a ceramic package. But to perform an acceptable construction analysis, five devices are needed.
The typical construction analysis sequence for a plastic SOIC-8 component is as follows:
1. External visual inspection
External visual inspection is the observation of the component under analysis under a microscope. This step verifies that the device marking on a component are legible and that there are no defects in the molding.
The pictures above show correct marking of components.
2. X-Ray Inspection
X-Ray inspection is a radiography of the component, very similar to an x-ray of the lungs or a broken bone at a medical x-ray center. The purpose of this test is to verify that the die is correctly positioned on its lead frame, that there are no voids in the die attach, that the spacing and connection of the wires are ok, without opening the component.
The picture below shows the x ray picture of a SOIC 8. The die attaches and die position are acceptable.
3. C-SAM or Acoustic Microscopy Inspection
Acoustic microscopy inspection used focused sound waves from a transducer targeted at a small point on an object. The sound that hits the object is either absorbed, reflected, transmitted or scattered. A CSAM analysis detects delamination and peeling or flaking of the resin.
The picture below shows the CSAM analysis of a SOIC 8 component:
The picture shows a correct component, with no delamination on this side of the component, near the die.
4. Internal Visual Inspection
The internal visual inspection consists of opening (usually chemically) the package of the component to have a clear view of the die circuitry, to observe the design, construction, and assembly of the die. We also use internal visual inspection to verify the date code and mask number of the die.
Below is a picture of a die under internal visual inspection. The component is an operational amplifier packaged in a SOIC-8 package.
The following picture shows a zoom on the date code and mask number of the device under analysis.
5. Scanning Electron Microscope (SEM) Assembly Inspection
A scanning electron microscope sends an electron beam through the component. The image produced by the microscope is a translation of how the electrons interact with the atoms of the components.
We can observe with this technique, the die placement and the wiring of the die to the lead frame. SEM also gives the opportunity of checking the ball bonds, check if it is correctly formed and well centered on the pad areas and control the stitch bonds, whether they are correctly positioned and formed on the leads.
The pictures below show the ball bonds and stitch bonds of the operational amplifier:
SEM also allows us to check for glassivation (or passivation) of the die. Glassivation or passivation is the deposition of a final passivating layer on top of the die, to protect the latter from mechanical damage and corrosion. SEM is one of the only techniques to check for the presence of glassivation of a die.
6. Wire pull test
This test is performed on a chemically opened component. It consists of applying an upward force under the wire bond under test, effectively pulling the wire away from the die. And this test requires a wire pull tester.
This test is used to measure the strength of the wire bonds and to verify that they are compliant to military standard MIL.STD.883K Method 2011
7. Ball shear test
This test is also performed on the chemically opened component. It consists of shearing individually with a tool aligned at an accurate position above the device’s surface and the force is simultaneously measured. This test is used to verify that the ball bonds are in accordance with the JEDEC standard JESD22-B116
8. Package microsection
Package microsection is a process allowing us to observe the different layers in a component. The component is molded in a fluorescent resin before being cut along an axis.
We can observe the die positioning on the lead frame, the layer of resin or resins if there are many, if there is porosity in the resin, observe the die attaches, if there is the presence of purple plague, observe the soldered connection, measure the epitaxial layer of the die or witness some delamination (when SEM performed on cut component).
How is construction analysis applicable
Construction analysis are indispensable on space equipment project to justify the use of some components on the equipment’s design. Among the 32 analyzed components to date, 4 were rejected since the results were unsatisfactory.
2 of the references analyzed showed severe signs of delamination which is unacceptable for design and one of the rejected components had no glassivation on its die.