Electroless Nickel Immersion Gold Hyper Corrosion Detection in Board Assembly
Detecting ENIG hyper corrosion requires destructive micro-sectioning and FIB-SEM to identify phosphorus-rich nickel spikes before assembly reflow.
FIB Sectioning
Meaning
Advanced microscopy techniques utilizing a focused beam of ions enable the removal of specific material layers to reveal the internal structure of semiconductor devices or composite materials. Within a laboratory setting, fib sectioning provides a precise way to inspect the integrity of sub micron features without destroying the entire sample. The equipment uses a column of liquid metal, typically gallium, accelerated toward the target area to mill away small quantities of material through physical sputtering.
This process creates a smooth vertical face that can be imaged at high resolution using an integrated electron beam. It is an indispensable tool for failure analysis in Chinese electronics factories where identifying the root cause of a broken circuit requires looking inside the layered architecture of the chip.
Operational Procedure
Execution of the site specific cut begins with the identification of the target coordinates under a high magnification electron scan. During fib sectioning, a protective layer of platinum or tungsten is first deposited on the surface to prevent damage from the aggressive ion bombardment. The operator then tilts the sample stage to an angle that allows the ion beam to clear a wedge shaped hole adjacent to the area of interest.
As the milling progresses, the ion current is gradually reduced to polish the surface to a mirror finish, ensuring that the internal components are visible without artifacts. Real time monitoring allows for the detection of voids, cracks, or metallic migration that might explain a component failure. This precision allows the technician to target specific transistors or interconnects located deep within the 3D stack of a modern processor.
Technical utility
Applications for this diagnostic method span from quality control of batch production to the reverse engineering of competitive components. The clear view provided by fib sectioning allows manufacturers to check if the layers deposited during the lithography and etching phases match the intended design thicknesses. It is also used to create thin membranes for subsequent transmission electron microscopy which requires samples to be less than one hundred nanometers thick.
Beyond electronics, the technique helps in studying the interface between different metals in specialized alloys or the adhesion of coatings in high performance tools. This helps the material scientists understand the bond at the atomic level and improve the durability of future products. The speed of the process compared to traditional mechanical cross sectioning saves days of preparation time in critical investigations.
Measurement Accuracy
Limits on the accuracy of the images produced depend on the stability of the beam and the skill of the operator in managing the charging effects on non conductive samples. While fib sectioning is incredibly accurate, the interaction between the gallium ions and the sample can introduce small quantities of contamination or local heating. If the beam dwell time is too long, it might alter the very structure the engineer is trying to observe.
Modern systems integrate automated patterns to minimize these risks and produce reproducible results across different shifts. Despite these challenges, the ability to selectively target a ten nanometer area makes it the gold standard for microanalysis in the modern manufacturing sector. The data gathered from these sections forms the basis for substantial design updates and production adjustments.