In ICs, the epoxy encapsulant must be removed to expose the die for failure analysis. Sometimes the die needs to be placed in a different package. This must be done without altering the electrical functionality of the device.
Semiconductor devices are very fragile and must be packaged so they can be mounted on printed circuit boards. Depending on the nature of the device, the package may range from very simple to very complex. A diode laser, for example, has only a few terminals while a microprocessor may have several hundreds.
The package facilitates electrical access to the device and sheds the heat generated during operation. It protects the fragile semiconductor chip from environmental humidity, chemical contamination, and mechanical stresses.
Acids or solvents are generally used to "open" devices, exposing the semiconductor device while keeping its connections to the package intact. When the package geometry makes that impossible, the device can be removed and attached to a different package.