Dual in-line package
In microelectronics, a dual in-line package is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board or inserted in a socket. The dual-inline format was invented by Don Forbes, Rex Rice and Bryant Rogers at Fairchild R&D in 1964, when the restricted number of leads available on circular transistor-style packages became a limitation in the use of integrated circuits. Increasingly complex circuits required more signal and power supply leads ; eventually microprocessors and similar complex devices required more leads than could be put on a DIP package, leading to development of higher-density chip carriers. Furthermore, square and rectangular packages made it easier to route printed-circuit traces beneath the packages.
A DIP is usually referred to as a DIPn, where n is the total number of pins, and sometimes appended with the row-to-row package width "N" for narrow or "W" for wide. For example, a microcircuit package with two rows of seven vertical leads would be a DIP14 or DIP14N. The photograph at the upper right shows three DIP14 ICs. Common packages have as few as four and as many as 64 leads. Many analog and digital integrated circuit types are available in DIP packages, as are arrays of transistors, switches, light emitting diodes, and resistors. DIP plugs for ribbon cables can be used with standard IC sockets.
DIP packages are usually made from an opaque molded epoxy plastic pressed around a tin-, silver-, or gold-plated lead frame that supports the device die and provides connection pins. Some types of IC are made in ceramic DIP packages, where high temperature or high reliability is required, or where the device has an optical window to the interior of the package. Most DIP packages are secured to a PCB by inserting the pins through holes in the board and soldering them in place. Where replacement of the parts is necessary, such as in test fixtures or where programmable devices must be removed for changes, a DIP socket is used. Some sockets include a zero insertion force mechanism.
Variations of the DIP package include those with only a single row of pins, e.g. a resistor array, possibly including a heat sink tab in place of the second row of pins, and types with four rows of pins, two rows, staggered, on each side of the package. DIP packages have been mostly displaced by surface-mount package types, which avoid the expense of drilling holes in a PCB and which allow higher density of interconnections.
Applications
Types of devices
DIPs are commonly used for integrated circuits. Other devices in DIP packages include resistor networks, DIP switches, LED segmented and bar graph displays, and electromechanical relays.DIP connector plugs for ribbon cables are common in computers and other electronic equipment.
Dallas Semiconductor manufactured integrated DIP real-time clock modules which contained an IC chip and a non-replaceable 10-year lithium battery.
DIP header blocks onto which discrete components could be soldered were used where groups of components needed to be easily removed, for configuration changes, optional features or calibration.
Uses
The original dual-in-line package was invented by Bryant "Buck" Rogers in 1964 while working for Fairchild Semiconductor. The first devices had 14 pins and looked much like they do today. The rectangular shape allowed integrated circuits to be packaged more densely than previous round packages. The package was well-suited to automated assembly equipment; a PCB could be populated with scores or hundreds of ICs, then all the components on the circuit board could be soldered at one time on a wave soldering machine and passed on to automated testing machines, with very little human labor required. DIP packages were still large with respect to the integrated circuits within them. By the end of the 20th century, surface-mount packages allowed further reduction in the size and weight of systems. DIP chips are still popular for circuit prototyping on a breadboard because of how easily they can be inserted and used there.DIPs were the mainstream of the microelectronics industry in the 1970s and 1980s. Their use has declined in the first decade of the 21st century due to the emerging new surface-mount technology packages such as plastic leaded chip carrier and small-outline integrated circuit, though DIPs continued in extensive use through the 1990s, and still continue to be used today. Because some modern chips are available only in surface-mount package types, a number of companies sell various prototyping adapters to allow those surface-mount devices to be used like DIP devices with through-hole breadboards and soldered prototyping boards.
For programmable devices like EPROMs and GALs, DIPs remained popular for many years due to their easy handling with external programming circuitry However, with in-system programming technology now state-of-the-art, this advantage of DIPs is rapidly losing importance as well.
Through the 1990s, devices with fewer than 20 leads were typically manufactured in a DIP format in addition to the newer formats. Since about 2000, newer devices are often unavailable in the DIP format.
Mounting
DIPs can be mounted either by through-hole soldering or in sockets. Sockets allow easy replacement of a device and eliminates the risk of damage from overheating during soldering. Generally sockets were used for high-value or large ICs, which cost much more than the socket. Where devices would be frequently inserted and removed, such as in test equipment or EPROM programmers, a zero insertion force socket would be used.DIPs are also used with breadboards, a temporary mounting arrangement for education, design development or device testing. Some hobbyists, for one-off construction or permanent prototyping, use point-to-point wiring with DIPs, and their appearance when physically inverted as part of this method inspires the informal term "dead bug style" for the method.
Construction
The body of a DIP containing an IC chip is usually made from molded plastic or ceramic. The hermetic nature of a ceramic housing is preferred for extremely high reliability devices. However, the vast majority of DIPs are manufactured via a thermoset molding process in which an epoxy mold compound is heated and transferred under pressure to encapsulate the device. Typical cure cycles for the resins are less than 2 minutes and a single cycle may produce hundreds of devices.The leads emerge from the longer sides of the package along the seam, parallel to the top and bottom planes of the package, and are bent downward approximately 90 degrees. In ceramic packages, an epoxy or grout is used to hermetically seal the two halves together, providing an air and moisture tight seal to protect the IC die inside. Plastic DIP packages are usually sealed by fusing or cementing the plastic halves around the leads, but a high degree of hermeticity is not achieved because the plastic itself is usually somewhat porous to moisture and the process cannot ensure a good microscopic seal between the leads and the plastic at all points around the perimeter. However, contaminants are usually still kept out well enough that the device can operate reliably for decades with reasonable care in a controlled environment.
Inside the package, the lower half has the leads embedded, and at the center of the package is a rectangular space, chamber, or void into which the IC die is cemented. The leads of the package extend diagonally inside the package from their positions of emergence along the periphery to points along a rectangular perimeter surrounding the die, tapering as they go to become fine contacts at the die. Ultra-fine bond wires are welded between these die periphery contacts and bond pads on the die itself, connecting one lead to each bond pad, and making the final connection between the microcircuits and the external DIP leads. The bond wires are not usually taut but loop upward slightly to allow slack for thermal expansion and contraction of the materials; if a single bond wire breaks or detaches, the entire IC may become useless. The top of the package covers all of this delicate assemblage without crushing the bond wires, protecting it from contamination by foreign materials.
Usually, a company logo, alphanumeric codes and sometimes words are printed on top of the package to identify its manufacturer and type, when it was made, sometimes where it was made, and other proprietary information
The necessity of laying out all of the leads in a basically radial pattern in a single plane from the die perimeter to two rows on the periphery of the package is the main reason that DIP packages with higher lead counts must have wider spacing between the lead rows, and it effectively limits the number of leads which a practical DIP package may have. Even for a very small die with many bond pads, a wider DIP would still be required to accommodate the radiating leads internally. This is one of the reasons that four-sided and multiple rowed packages, such as PGAs, were introduced.
A large DIP package has long leads inside the package between pins and the die, making such a package unsuitable for high speed devices.
Some other types of DIP devices are built very differently. Most of these have molded plastic housings and straight leads or leads that extend directly out of the bottom of the package. For some, LED displays particularly, the housing is usually a hollow plastic box with the bottom/back open, filled with a hard translucent epoxy material from which the leads emerge. Others, such as DIP switches, are composed of two plastic housing parts snapped, welded, or glued together around a set of contacts and tiny mechanical parts, with the leads emerging through molded-in holes or notches in the plastic.