Decapsulation is a chemical etching technique for opening IC plastic packages in order to expose their internal components for examination. Although physically destructive in nature, the process leaves the die, bond pads, and wire bonds intact.
Several methods of decapsulation are available depending upon the device and the customer’s requirements. Such methods include jet etching, manual cavity etching, and total package removal. Fuming nitric acid (HNO3), sulfuric acid (H2SO4) or a mixture of the two acids are used to dissolve the encapsulant.
Jet etching is an automated version of chemical decapsulation. The jet etcher dispenses a stream of acid onto the package creating a cavity and exposing the die. With manual etching, a depression is first milled into the surface of the package after which acid is dropped into the cavity to dissolve the encapsulant over the die. Total package removal is performed by dissolving the entire package in a beaker of sulfuric acid leaving only the silicon die and some amount of undissolved metal. This last technique is primarily used to inspect for cracks on the back of die.