Semiconductor package

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A semiconductor package is a metal, plastic, glass, or ceramic casing containing one or more discrete semiconductor devices or integrated circuits. Individual components are fabricated on semiconductor wafers (commonly silicon) before being diced into die, tested, and packaged. The package provides a means for connecting it to the external environment, such as printed circuit board, via leads such as lands, balls, or pins; and protection against threats such as mechanical impact, chemical contamination, and light exposure. Additionally, it helps dissipate heat produced by the device, with or without the aid of a heat spreader. There are thousands of package types in use. Some are defined by international, national, or industry standards, while others are particular to an individual manufacturer.

Contents

Package functions

A semiconductor package may have as few as two leads or contacts for devices such as diodes, or in the case of advanced microprocessors, a package may have several thousand connections. Very small packages may be supported only by their wire leads. Larger devices, intended for high-power applications, are installed in carefully designed heat sinks so that they can dissipate hundred or thousands of watts of waste heat.

In addition to providing connections to the semiconductor and handling waste heat, the semiconductor package must protect the "chip" from the environment, particularly the ingress of moisture. Stray particles or corrosion products inside the package may degrade performance of the device or cause failure. [1] A hermetic package allows essentially no gas exchange with the surroundings; such construction requires glass, ceramic or metal enclosures.

This replica of the first laboratory transistor shows connecting leads and a glass jar for protection; packaging the device was critical to its success. Replica-of-first-transistor.jpg
This replica of the first laboratory transistor shows connecting leads and a glass jar for protection; packaging the device was critical to its success.

Date code

Manufacturers usually print the manufacturer's logo and the part number on the package using ink or laser marking. This makes it easier to distinguish the many different and incompatible devices packaged in relatively few kinds of packages. The markings often include a 4 digit date code, often represented as YYWW where YY is replaced by the last two digits of the calendar year and WW is replaced by the two-digit week number, [2] [3] typically the ISO week number.

Very small packages often include a two-digit date code. One two-digit date code uses YW, where Y is the last digit of the year (0 to 9) and W starts at 1 at the beginning of the year and is incremented every 6 weeks (i.e., W is 1 to 9). [2] Another two-digit date code, the RKM production date code, use YM, where Y is one of 20 letters that repeat in a cycle every 20 years (for example, "M" was used to represent 1980, 2000, 2020, etc.) and M indicates the month of production (1 to 9 indicate January to September, O indicates October, N indicates November, D indicates December).

Leads

To make connections between an integrated circuit and the leads of the package, wire bonds are used, with fine wires connected from the package leads and bonded to conductive pads on the semiconductor die. At the outside of the package, wire leads may be soldered to a printed circuit board or used to secure the device to a tag strip. Modern surface mount devices eliminate most of the drilled holes through circuit boards, and have short metal leads or pads on the package that can be secured by oven-reflow soldering. Aerospace devices in flat packs may use flat metal leads secured to a circuit board by spot welding, though this type of construction is now uncommon.

Sockets

Early semiconductor devices were often inserted in sockets, like vacuum tubes. As devices improved, eventually sockets proved unnecessary for reliability, and devices were directly soldered to printed circuit boards. The package must handle the high temperature gradients of soldering without putting stress on the semiconductor die or its leads.

Sockets are still used for experimental, prototype, or educational applications, for testing of devices, for high-value chips such as microprocessors where replacement is still more economical than discarding the product, and for applications where the chip contains firmware or unique data that might be replaced or refreshed during the life of the product. Devices with hundreds of leads may be inserted in zero insertion force sockets, which are also used on test equipment or device programmers.

Package materials

Many devices are molded out of an epoxy plastic that provides adequate protection of the semiconductor devices, and mechanical strength to support the leads and handling of the package. The plastic can be cresol-novolaks, siloxane polyimide, polyxylylene, silicones, polyepoxides and bisbenzocyclo-butene. [4] Some devices, intended for high-reliability or aerospace or radiation environments, use ceramic packages, with metal lids that are brazed on after assembly, or a glass frit seal. All-metal packages are often used with high power (several watts or more) devices, since they conduct heat well and allow for easy assembly to a heat sink. Often the package forms one contact for the semiconductor device. Lead materials must be chosen with a thermal coefficient of expansion to match the package material. Glass may be used in the package as the package substrate to reduce its thermal expansion and increase its stiffness, which reduce warping and facilitate mounting of the package to a PCB. [5] [6]

A very few early semiconductors were packed in miniature evacuated glass envelopes, like flashlight bulbs; such expensive packaging was made obsolete when surface passivation and improved manufacturing techniques were available. [1] Glass packages are still commonly used with diodes, and glass seals are used in metal transistor packages.

Package materials for high-density dynamic memory must be selected for low background radiation; a single alpha particle emitted by package material can cause a single event upset and transient memory errors (soft errors).

Spaceflight and military applications traditionally used hermetically packaged microcircuits (HPMs). However, most modern integrated circuits are only available as plastic encapsulated microcircuits (PEMs). Proper fabrication practices using properly qualified PEMs can be used for spaceflight. [7]

Hybrid integrated circuits

A hybrid integrated circuit IntegratedCircuit1966.JPG
A hybrid integrated circuit

Multiple semiconductor dies and discrete components can be assembled on a ceramic substrate and interconnected with wire bonds. The substrate bears leads for connection to an external circuit, and the whole is covered with a welded or frit cover. Such devices are used when requirements exceed the performance (heat dissipation, noise, voltage rating, leakage current, or other properties) available in a single-die integrated circuit, or for mixing analog and digital functions in the same package. Such packages are relatively expensive to manufacture, but provide most of the other benefits of integrated circuits.

A modern example of multi-chip integrated circuit packages would be certain models of microprocessor, which may include separate dies for such things as cache memory within the same package. In a technique called flip chip, digital integrated circuit dies are inverted and soldered to a module carrier, for assembly into large systems. [8] The technique was applied by IBM in their System/360 computers. [9]

Special packages

Semiconductor packages may include special features. Light-emitting or light-sensing devices must have a transparent window in the package; other devices such as transistors may be disturbed by stray light and require an opaque package. [1] An ultraviolet erasable programmable read-only memory device needs a quartz window to allow ultraviolet light to enter and erase the memory. Pressure-sensing integrated circuits require a port on the package that can be connected to a gas or liquid pressure source.

Packages for microwave frequency devices are arranged to have minimal parasitic inductance and capacitance in their leads. Very-high-impedance devices with ultralow leakage current require packages that do not allow stray current to flow, and may also have guard rings around input terminals. Special isolation amplifier devices include high-voltage insulating barriers between input and output, allowing connection to circuits energized at 1 kV or more.

The very first point-contact transistors used metal cartridge-style packages with an opening that allowed adjustment of the whisker used to make contact with the germanium crystal; such devices were common for only a brief time since more reliable, less labor-intensive types were developed. [1]

Standards

Just like vacuum tubes, semiconductor packages standards may be defined by national or international industry associations such as JEDEC, Pro Electron, or EIAJ, or may be proprietary to a single manufacturer.

See also

Related Research Articles

<span class="mw-page-title-main">Integrated circuit</span> Electronic circuit formed on a small, flat piece of semiconductor material

An integrated circuit (IC), also known as a microchip, computer chip, or simply chip, is a small electronic device made up of multiple interconnected electronic components such as transistors, resistors, and capacitors. These components are etched onto a small piece of semiconductor material, usually silicon. Integrated circuits are used in a wide range of electronic devices, including computers, smartphones, and televisions, to perform various functions such as processing and storing information. They have greatly impacted the field of electronics by enabling device miniaturization and enhanced functionality.

<span class="mw-page-title-main">Transistor</span> Solid-state electrically operated switch also used as an amplifier

A transistor is a semiconductor device used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more in miniature form are found embedded in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.

<span class="mw-page-title-main">Dual in-line package</span> Type of electronic component 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 (PCB) 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.

<span class="mw-page-title-main">Ball grid array</span> Surface-mount packaging that uses an array of solder balls

A ball grid array (BGA) is a type of surface-mount packaging used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be put on a dual in-line or flat package. The whole bottom surface of the device can be used, instead of just the perimeter. The traces connecting the package's leads to the wires or balls which connect the die to package are also on average shorter than with a perimeter-only type, leading to better performance at high speeds.

<span class="mw-page-title-main">Surface-mount technology</span> Method for producing electronic circuits

Surface-mount technology (SMT), originally called planar mounting, is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). An electrical component mounted in this manner is referred to as a surface-mount device (SMD). In industry, this approach has largely replaced the through-hole technology construction method of fitting components, in large part because SMT allows for increased manufacturing automation which reduces cost and improves quality. It also allows for more components to fit on a given area of substrate. Both technologies can be used on the same board, with the through-hole technology often used for components not suitable for surface mounting such as large transformers and heat-sinked power semiconductors.

<span class="mw-page-title-main">Pin grid array</span> Type of integrated circuit packaging with the pins mounted on the underside of the package

A pin grid array (PGA) is a type of integrated circuit packaging. In a PGA, the package is square or rectangular, and the pins are arranged in a regular array on the underside of the package. The pins are commonly spaced 2.54 mm (0.1") apart, and may or may not cover the entire underside of the package.

<span class="mw-page-title-main">Flip chip</span> Technique that flips a microchip upside down to connect it

Flip chip, also known as controlled collapse chip connection or its abbreviation, C4, is a method for interconnecting dies such as semiconductor devices, IC chips, integrated passive devices and microelectromechanical systems (MEMS), to external circuitry with solder bumps that have been deposited onto the chip pads. The technique was developed by General Electric's Light Military Electronics Department, Utica, New York. The solder bumps are deposited on the chip pads on the top side of the wafer during the final wafer processing step. In order to mount the chip to external circuitry, it is flipped over so that its top side faces down, and aligned so that its pads align with matching pads on the external circuit, and then the solder is reflowed to complete the interconnect. This is in contrast to wire bonding, in which the chip is mounted upright and fine wires are welded onto the chip pads and lead frame contacts to interconnect the chip pads to external circuitry.

<span class="mw-page-title-main">Integrated circuit packaging</span> Final stage of semiconductor device fabrication

Integrated circuit packaging is the final stage of semiconductor device fabrication, in which the die is encapsulated in a supporting case that prevents physical damage and corrosion. The case, known as a "package", supports the electrical contacts which connect the device to a circuit board.

<span class="mw-page-title-main">Quad flat package</span> Surface mount integrated circuit package with "gull wing" pins extending from all sides

A quad flat package (QFP) is a surface-mounted integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 pins with a pitch ranging from 0.4 to 1.0 mm are common. Other special variants include low-profile QFP (LQFP) and thin QFP (TQFP).

<span class="mw-page-title-main">Solid Logic Technology</span> IBM hybrid circuit technology introduced in 1964

Solid Logic Technology (SLT) was IBM's method for hybrid packaging of electronic circuitry introduced in 1964 with the IBM System/360 series of computers. It was also used in the 1130, announced in 1965. IBM chose to design custom hybrid circuits using discrete, flip chip-mounted, glass-encapsulated transistors and diodes, with silk-screened resistors on a ceramic substrate, forming an SLT module. The circuits were either encapsulated in plastic or covered with a metal lid. Several of these SLT modules were then mounted on a small multi-layer printed circuit board to make an SLT card. Each SLT card had a socket on one edge that plugged into pins on the computer's backplane.

<span class="mw-page-title-main">Hybrid integrated circuit</span> Type of miniature electronic circuit

A hybrid integrated circuit (HIC), hybrid microcircuit, hybrid circuit or simply hybrid is a miniaturized electronic circuit constructed of individual devices, such as semiconductor devices and passive components, bonded to a substrate or printed circuit board (PCB). A PCB having components on a Printed wiring board (PWB) is not considered a true hybrid circuit according to the definition of MIL-PRF-38534.

<span class="mw-page-title-main">TO-3</span> Metal can semiconductor package for power semiconductors

In electronics, TO-3 is a designation for a standardized metal semiconductor package used for power semiconductors, including transistors, silicon controlled rectifiers, and, integrated circuits. TO stands for "Transistor Outline" and relates to a series of technical drawings produced by JEDEC.

<span class="mw-page-title-main">Thermal copper pillar bump</span>

The thermal copper pillar bump, also known as the "thermal bump", is a thermoelectric device made from thin-film thermoelectric material embedded in flip chip interconnects for use in electronics and optoelectronic packaging, including: flip chip packaging of CPU and GPU integrated circuits (chips), laser diodes, and semiconductor optical amplifiers (SOA). Unlike conventional solder bumps that provide an electrical path and a mechanical connection to the package, thermal bumps act as solid-state heat pumps and add thermal management functionality locally on the surface of a chip or to another electrical component. The diameter of a thermal bump is 238 μm and 60 μm high.

<span class="mw-page-title-main">Failure of electronic components</span> Ways electronic components fail and prevention measures

Electronic components have a wide range of failure modes. These can be classified in various ways, such as by time or cause. Failures can be caused by excess temperature, excess current or voltage, ionizing radiation, mechanical shock, stress or impact, and many other causes. In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits.

<span class="mw-page-title-main">Chip carrier</span> Surface mount technology package for integrated circuits

In electronics, a chip carrier is one of several kinds of surface-mount technology packages for integrated circuits. Connections are made on all four edges of a square package; compared to the internal cavity for mounting the integrated circuit, the package overall size is large.

<span class="mw-page-title-main">TO-5</span> Standardized metal semiconductor package

In electronics, TO-5 is a designation for a standardized metal semiconductor package used for transistors and some integrated circuits. The TO element stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC. The first commercial silicon transistors, the 2N696 and 2N697 from Fairchild Semiconductor, came in a TO-5 package.

Decapping (decapsulation) or delidding of an integrated circuit (IC) is the process of removing the protective cover or integrated heat spreader (IHS) of an integrated circuit so that the contained die is revealed for visual inspection of the micro circuitry imprinted on the die. This process is typically done in order to debug a manufacturing problem with the chip, or possibly to copy information from the device, to check for counterfeit chips or to reverse engineer it. Companies such as TechInsights and ChipRebel decap, take die shots of, and reverse engineer chips for customers. Modern integrated circuits can be encapsulated in plastic, ceramic, or epoxy packages.

<span class="mw-page-title-main">Chip on board</span> Method of circuit board manufacture

Chip on board (COB) is a method of circuit board manufacturing in which the integrated circuits (e.g. microprocessors) are attached (wired, bonded directly) to a printed circuit board, and covered by a blob of epoxy. Chip on board eliminates the packaging of individual semiconductor devices, which allows a completed product to be less costly, lighter, and more compact. In some cases, COB construction improves the operation of radio frequency systems by reducing the inductance and capacitance of integrated circuit leads.

Glossary of microelectronics manufacturing terms

References

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  2. 1 2 "Quality & Lead-free (Pb-free): Marking Convention". Texas Instruments. Archived from the original on 2015-10-04. Retrieved August 6, 2015.
  3. Vintage Calculators Web Museum: Frequently Asked Questions: "Date codes on electronics components and circuit boards". Retrieved 2020-04-23.
  4. "Encapsulant - an overview | ScienceDirect Topics".
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  6. Delmdahl, Ralph & Paetzel, Rainer. (2014). Laser Drilling of High-Density Through Glass Vias (TGVs) for 2.5D and 3D Packaging. Journal of the Microelectronics and Packaging Society. 21. 53-57. 10.6117/kmeps.2014.21.2.053.
  7. Ronald K. Burek, Johns Hopkins APL Technical Digest. “The NEAR Solid-State Data Recorders.” 1998. Retrieved August 6, 2015.
  8. Keyan Bennaceur, Nature.com. “Mechanical Flip-Chip for Ultra-High Electron Mobility Devices.” September 22, 2015. April 23, 2015.
  9. Michael Pecht (ed) Integrated circuit, hybrid, and multichip module package design guidelines: a focus on reliability, Wiley-IEEE, 1994 ISBN   0-471-59446-6, page 183