IC packaging is a method of protecting semiconductor components from external physical damage or corrosion, by encasing them in packaging materials made of ceramic or plastic. There are many different types of integrated circuits, following different circuit designs and outer shell needs. This translates to different types of IC packaging designs and different ways of classifying them.
Modern IC packaging designs are good avenues to achieve functional density, heterogeneous integration, and silicon scaling. Furthermore, they are ideal for reducing the general packaging size of many electronic applications that have enhanced device functionality and silicon yield resilience.
IC packaging is the shortened term for Integrated Circuit packaging. It is a component or material in which a semiconductor device is contained. This means that the package encases or surrounds the circuit device, and in doing so, protects it from physical damage or corrosion.
Plastics or ceramics are the commonly used materials for IC packaging because they have better electrical conductivity. This feature is vital since IC packaging also serves the purpose of facilitating the mounting of electrical contacts that are connected to the printed circuit board (PCB) of an electronic device. The organization of connections on an IC and how they are laid out using a standard IC package must be in accordance with the use cases and applications of particular ICs.
IC packaging is the final stage in the manufacture of semiconductor devices, after which the integrated circuit is sent for testing to determine if it measures up to industry standards. [1]
Integrated circuits are typically fragile and do not have their connectors or pins to be connected to a circuit board. By introducing circuit packaging, chip carriers will be used to protect the delicate structure of the integrated circuits and provide pin connectors as well. The aforementioned protection is possible due to the plastic, glass, metal, or ceramic material that the packages can be made of, providing a physical barrier against external impact and corrosion. IC packaging also has the added benefit of thermal regulation in the devices that they are used for.
Furthermore, the packages are made up of individual parts that facilitate the general performance of the integrated circuit and ensure reliability. The leads are typically made of copper and a thin plating of tin with finer wires connected to the package. These are useful for establishing a strong connection between the leads and the integrated circuit. After this, the leads are bonded with conductive pads on the semiconductor die, then connected to the PCB on the outer part of the package, through soldering. Even discrete parts like capacitors, transistors, or diodes have a wide range of small pin count packages utilized for them. [2]
There are many IC packages and different ways of classifying them. On the subject of IC packages, it is common to come across technical abbreviated terms such as DIP, SIP, SOP, SSOP, TSOP, MSOP, QSOP, SOIC, QFP, TQFP, BGA, etc. These are all names of different IC packages and they can be categorized in different ways.
IC package types can be distinguished by their mounting style, as they fall into two broad categories, namely Through-hole and Surface Mount Technology (SMT). Through-hole packages have their leads inserted through holes on the PCB and then soldered, while surface mount packages have components mounted directly on the exterior of the board. Surface mount packaging components are called surface mount devices (SMD).
Another way to classify IC packages is by their pin layout. Integrated circuits are usually linear, square, or rectangular shaped, so the pin layout can be linear, in two parallel directions, on the four sides, or in matrix form. Further classification can be done by pin or terminal shape. The shapes can be linear, L-shape, J-shape, needle shape, mutual folding, and tape/film shape, among others. Lastly, IC packages can be distinguished by terminal or pin count. There are two-terminal, three-terminal, four-terminal, five-terminal, six-terminal, and over six terminal packages. The terminal dimensions may also serve as a differentiating factor for similar package types. [3]
Some common types of integrated circuit packaging are discussed in the subsequent sections.
A chip carrier is a type of SMT package for integrated circuits. Also known as chip container or chip package, chip carrier allows semiconductor chips to be plugged into, or soldered onto a printed circuit board (PCB), whilst keeping the fragile components protected. A chip carrier may be attached to a circuit board by being plugged in, soldered, or held in with springs, depending on its design.
Carriers with plugs, also known as socket mounts, have J-shaped metal pins, or leads, which can be used for connections on a board by solder or by a socket. When a carrier is soldered directly onto the board, it is called a surface mount.
The spring mounting method is introduced in cases where the force of soldering or pins will damage delicate components. It is usually done by installing a spring mechanism in the area where the component will be attached, then the springs are carefully pushed to the side enough to lock the piece in place. Chip carriers may also be lead-less with metal pads for connections. When the leads extend beyond the package, it is called a flat pack.
There are several different types of chip carriers, made with a wide variety of materials such as ceramics, silicone, metal, and plastic. Chip carriers are usually square or rectangular shaped and connections are made on all four sides of the package. They also come in different sizes and thicknesses. [4]
Types of chip-carrier packages are usually indicated by acronyms and they include:
Through-hole package components have lead pins that are stuck through one side of a circuit board and soldered onto the pads on the other side of the board to mechanically and electrically connect them to the PCB. These packages come in ceramic and plastic, and they are typed in these categories:
Single in-line Pin Package (SIP or SIPP): This has a single row of connecting pins that are vertically arranged along the boundary line of the package. It is not as popularly used as DIP (Dual In-line Package), but it has come in handy for the packaging of network resistors and RAM chips. Common single in-line packages include SIP (Single In-line Package), SSIP (Shrink Single In-Line Package), and HSIP (Single In-line Package with Heat Sink).
Dual In-line Packages (DIP): The dual in-line package or dual in-line pin package (DIPP) has two parallel rows of electrical connecting pins in a rectangular plastic housing. It may be through-hole mounted to a PCB or inserted in a socket. Also, it varies in size due to the difference in the number of pins in different packages, which usually range from 4 to 64.
Common dual-inline packages include DIP (Dual In-line Package), SDIP (Shrink Dual In-line), CDIP (Ceramic Dual In-line), CER-DIP (Glass-sealed Ceramic DIP), PDIP (Plastic DIP), SKDIP (Skinny DIP), WDIP (Dual In-line with Window Package), and MDIP (Molded DIP).
DIP Chip Package
Zig-Zag in-Line Packages (ZIP)- This PTH package is similar to SIP with lead pins lined on the boundary line of the package, but it has a zigzag folding. Common zigzag in-line packages include ZIP (Zigzag In-line Package) and SZIP (Shrink Zigzag In-line Package). [5]
Surface mount packaging technology is done by mounting or placing the electronic components directly on the surface of the printed circuit board. Surface mount components are usually smaller than their through-hole counterparts because they can either have smaller leads or no leads at all. It may have short pins or leads of various styles, and also uses ceramic or plastic molding.
There are five main package types for surface mount integrated circuits:
Pin Grid Array (PGA) IC packages arrange their pins in a square or rectangular grid that contains rows and columns, and the pins are arranged in a regular array on the underside of the package. They use tiny pins to create connections, which are arranged in a regular array on the underside of the package. PGA has many variants, determined by the array arrangement and the number of connections. They may be mounted on PCBs using the through hole method or inserted into a socket, and are mainly used to make processors. [7]
Variants of Pin Grid Array include:
Flat IC packages have two or four rows of terminals arranged along the edges of the integrated circuit. The mounting style used for these packages is usually surface-mount with leads taking the L-shape, J-shape, or being totally absent, in which case they are called leadless terminals. Common flat pack IC packages include: QFP (Quad Flat Package), TQFP (Thin Quad Flat Package), STQFP (Small Thin Quad Plastic Flat Package), FQFP (Fine-pitch Quad Flat Package), (Low profile Quad Flat Package), VQFP (Very-small Quad Flat Package), ETQFP (Exposed thin quad flat-package), PQFN (Power quad flat-pack), PQFP (Plastic quad flat-package), QFJ (Quad Flat J-leaded package), QFN (Quad Flat Non-leaded package), etc. [8]
TQFP Circuit Chip
The small outline package, called 'Small Outline Integrated Circuit', or SOIC, is a small rectangular surface-mount package with gull-wing leads and either plastic or ceramic molding. The pins are drawn in an L shape from both sides of the body, with the leads extending from the longer edge of the package. [9]
The small outline package has some IC packaging variants, which include:
The Chip Scale Package (CSP) is a surface mountable integrated circuit (IC) package that has an area not more than 1.2 times the original die area. Originally, CSP was the acronym for chip-size packaging, but it was adapted to chip-scale packaging since there are not many packages that are chip size.
IPC's (Institute for Interconnecting and Packaging Electronic Circuits) standard J-STD-012 for Implementation of Flip Chip and Chip Scale Technology states that a chip must be a single-die and have a ball pitch of not more than 1 mm before it can qualify as a chip scale package. [10]
Chip scale packages are classified as:
Ball grid array or BGA package is a type of surface-mount packaging that employs an array of metal spheres called solder balls for electrical interconnection. The underside of the package is used for the connections, where solder balls are attached to a laminated substrate in a grid pattern. This substrate has conductive traces on the inside that connect the die-to-substrate bonds to the substrate-to-ball array bonds, using wire bonding or flip-chip technology. [11]
Ball Grid Array variants include:
Integrated circuit packaging is an integral part of semiconductor manufacturing. It has become indispensable in modern electronics production due to its protective benefits, heat regulation, and wide application, which is important for both IC designing as well as PCB designing.
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