Dual beam electron microscopy allows for the simultaneous milling of material samples with an ion beam and the high resolution imaging of the resulting surface with electrons. In a metallurgical laboratory, fib sem microstructural analysis provides the ability to excise microscopic sections from a specific location on a sample without large scale mechanical cutting. It identifies internal grain orientations, void distributions, and chemical phases within layers as thin as a few nanometers inside an intermetallic joint.
This process reveals the precise location of hidden defects such as Kirkendall voids or micro cracks that typical sectioning methods would smear or destroy. The method is used primarily for root cause investigation when traditional imaging fails to identify the origin of a catastrophic failures in high precision manufacturing.
Gallium ions focus into a narrow high energy point to strip away atoms from the surface of a solder ball or a semiconductor die in a controlled manner. Utilizing fib sem microstructural analysis involves positioning the sample inside a vacuum chamber where the two separate beams converge on the precise area of interest. As the ion beam digs a trench into the target, the electron beam scans the vertical wall of the trench to create a live feed of the subsurface structure.
This ensures that the user can see exactly where the boundaries of each metallic phase sit within the stack. Because the ions remove material atom by atom, the resulting surface is extremely smooth, allowing for crystallographic orientation measurements that are impossible with sandpaper polishing. One major benefit is the ability to create thin lamella samples for even more powerful transmission electron microscopy if the investigation requires atomic level detail.
Samples undergo a protective platinum or tungsten deposition over the target site before the actual milling process begins to prevent surface charging or beam damage. Inside the environment of fib sem microstructural analysis, this coating ensures that the edges of the trench remain sharp and the delicate upper layers do not curl under the heat of the ion stream. Once the area is prepared, the robot arm positions the beam to cut out a u shaped wedge that is then lifted out by a tiny mechanical needle.
This slice contains the cross section of interest and can be analyzed for years without losing the data from the original hardware. Such portability makes it an essential tool for communicating failure data between global design offices and local manufacturing hubs. By looking at the grain structure at this scale, teams can determine if a failure resulted from overheating in the reflow oven or from high strain during the drop test.
Digital detectors capture the backscattered signals which highlight differences in atomic number between tin, copper, silver, and gold components of a joint. The depth of fib sem microstructural analysis is limited by the size of the vacuum chamber and the time required to mill deep into solid metallic structures. While it is perfect for small components, analyzing an entire circuit board would be prohibitively slow and expensive for standard quality checks.
It functions as a surgical tool, aimed specifically at the suspected point of failure once larger scale inspection has narrowed the field. The resulting images give designers the proof they need to adjust the alloy mix or the board thickness in the next production iteration.
Tightening peak reflow temperatures and limiting phosphorus content in electroless nickel plating prevents microvoid coalescence under thermal stress.
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