Dictionary of Electronics Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

IC Semiconductor Cavity Orientation

The cavity on an integrated circuit is the void that holds the semiconductor die within the package.

The terms Cavity Up and Cavity Down refers to the orientation of the package body cavity opening, away from the seating plane for cavity-up or toward the seating plane for cavity-down. The cavity orientation of an integrated circuit which holds the semiconductor die [the semiconductor die and pad facing up or down].

Examples of a cavity-up and cavity-down PGA package
IC Cavity Orientation

The location of the cavity and the body is the same regardless of the package style used, but this example shows a PGA. Very few semiconductors use the cavity-down orientation. There is also an open-cavity or air cavity semiconductor.

Because the cavity-up orientation is common it may not be mentioned in the data sheet, while the cavity-down orientation will be noted. Although very rare, an integrated circuit [a semiconductor residing in a package containing leads or terminals] may have more than one cavity, each holding a semiconductor die. The graphic to the right shows a 36 pin dual in-line package with two semiconductor cavities. The dimensions are not shown because the package could be almost any size with any number of pins. Although this package does relate to a common dip package, the actual size is not relevant to the topic of a cavity holding the semiconductor die.

Of course with a dual cavity, one semiconductor die is not effected by the other semiconductor die, unless they interconnect via the package leads or from the external circuitry. Assuming two different power and ground pins; noise on one semiconductor does not effect the other, or ground bounce may not be translated.

Unless otherwise specified in the data sheet most semiconductor IC packages, cavity orientation is standard in the "cavity-up" position; However some parts are designed for the cavity down configuration. The semiconductor chip rests on the longer portion of the cavity, the taller portion of the cavity is used to run the bonding wires. Cavity-down is usually used in a package that dissipates heat into the printed wiring board, either by using a copper pad under the component or by thermal vias passing through the printed wiring board.

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