Removing the package without losing the chip
A chip’s circuits are usually sealed inside a hard plastic package, which protects the delicate silicon die—the tiny piece of silicon where the circuitry is built—from moisture and physical damage. To inspect that circuitry, a researcher first opens a small well in the package, creating a path for acid to reach the surrounding plastic without flooding the whole component at once.
Fuming nitric acid is a powerful oxidizer: it reacts with the package’s organic material, breaking it down into products that can be removed. Heat speeds the reaction, so the plastic disappears while the silicon die is left exposed. The process is called acid decapsulation.
A controlled tradeoff
The aim is not simply to dissolve everything. A chip package can also contain metal connections and layers that matter to an investigation, and harsh acid can damage some of them. Researchers therefore control how much acid reaches the package, how long it reacts, and how the exposed components are handled. The work requires specialized equipment because fuming nitric acid is highly corrosive and releases dangerous fumes.
Once the package is removed, the exposed die can be examined under a microscope or prepared for further analysis. That can help reveal how a chip is laid out, whether its physical structure matches expectations, or where a defect occurred. The striking tradeoff is that a protective shell built to keep the circuitry untouched must be destroyed to make the circuitry visible.
