|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. In most cases, the functionality of the device
remains unchanged and suitable for failure analysis or functionality
analysis (reverse engineering).
|Several methods of decapsulation are
available depending upon the device and the customers 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.
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. At Silicon
Investigations, we use the Nippon Scientific Company's PA-103 acid
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. This is
accomplished with an end mill to make the depression, then the device
is heated on a hot plate while the chemicals are dripped into the
cavity. This method is rarely used with today's advanced devices, as
the package epoxy is very thin and likely to crack or otherwise damage
the die if improperly done.
Total package removal is performed by
using a special attachment to the PA-103 that allows acid to circulate
around the entire
package, thus removing all epoxy and the lead frame, leaving only the
silicon die and some amount of undissolved metal (usually only the gold
bond wire attached to the die). This technique is primarily used to
inspect for cracks on the back of die or to document die features where
no post decapsulation
chip functionality is required.