ABSTRACT
Consider a desktop computer and a DVD player as two examples of electronic systems. Both of these require power to function. That is usually provided by connecting them to power outlets through appropriate cables and wall plugs. They also require some form of input to provide the desired outputs. A computer receives input from a mouse, keyboard, or voice and displays the output on a monitor. A DVD player receives its input from a DVD and its output signal is transferred to a TV and is displayed on a TV monitor. In both cases there are input and output connectors; USB, serial, parallel, microphone, headphone, and other connectors for computer and coaxial, video, and audio connectors for DVD player. These input-output (I/O) connectors for power and signal are usually located on enclosures that contain the electronics of these systems. These enclosures or packages also protect the electronic devices against undesired contacts with other objects and exposure to dust, condensate, and so forth. Another role for these enclosures is that they usually come with some form of cooling method. Almost all desktop computers have one or more cooling fans that blow or draw air through the enclosure. This air is used to cool hot components such as a CPU, graphics module, hard disk drives, CD and DVD players, PCI cards, and power supply. The DVD players, on the other hand, may not come with a cooling fan. However, there are air vents on their enclosures that allow fresh air to enter and hot air to leave. This natural motion of air cools the electronic components inside the DVD player. These two examples show that packaging of electronics provides I/O interface for power and signal, protects electronic devices against a possibly harmful environment, and provides necessary cooling for heat dissipating electronics.
