Surface Mount Device Packages

What Are the Popular Types of Surface Mount Device Packages?

Aug 04,2021

Printed circuit boards have evolved tremendously over the last few decades and most of them now have a compact size and accommodate several components and dense circuitry. Accurate mounting of components on a circuit board along with the wires is of paramount importance as incorrect mounting will not only hamper the functioning but also cause shorting of circuits. The components or surface mount devices (SMDs) must be chosen carefully. There are many SMD packages you can choose from based on size, dimensions, and other factors. This post discusses the details of surface mount device packages and how to choose the right one.

What Are Surface Mount Device Packages?

Surface mount devices are electronic components which are mounted onto a circuit board, usually using surface mount technology (SMT). There are other mounting methods too, such as thru-hole technology and soldering. However, SMT is popular as it offers accurate output and does not require drilling of holes. There are various SMD packages. In a single package, there are a specific type of devices or components, which are usually mass produced. These packages act as component categories which help recognize their type and physical characteristics. The nomenclature of these SMD packages is based on their dimensions and physical attributes. They need to comply with the EIA specifications and are defined by the JEDEC Solid State Technology Association. A major reason behind the popularity of SMT is that it supports automated processes, which means they can be transferred from one place to another by using pick and place automated tool. This makes it easy for the PCB manufacturer and assembler.

Commonly Used Types of SMD Packages

With the increasing demand for miniature devices, the size of the boards and that of the components has shrunk too. But the fact that the mounting of SMDs can be totally automated has made it convenient for manufacturers. Else, it would have been difficult to mount extremely small components and connecting them to the right wires. There are SMT packages for resistors, capacitors, integrated circuits, microprocessors, and so on. Here are some of the popular surface mount device packages.

  • Packages for Resistors and Capacitors: These are rectangular packages with the dimensions mentioned in inches and millimeters. Each package type is numbered based on dimensions. For instance, the package type 2920 has resistor and capacitor components with dimensions of 0.29 x 0.20 inches or 7.4 x 5.1mm.
  • Packages for SMD Transistors:SOT-23, SOT-323, and SOT-523 are some of the widely used transistor SMDs. SOT-23 are typically small-signal transistors, while the other two are meant for fitment in small spaces or on a compact-sized board.
  • Packages for Integrated Circuits: These are categorized on the level of interconnectivity aside from the dimensions. Here are some of the popular SMD IC packages.
    • Small outline integrated circuit (SOIC): This has emerged as an effective replacement for through-hole and dual inline packages in recent years because of its obvious benefits. SOIC has lead with 0.050-inch centers, and is generally placed on its two sides.
    • Small outline package (SOP): These packages are thinner than SOIC. There are many varieties of these packages such as thin small package outline (TSOP) which has a small pin spacing of 0.5mm. Another version called shrink small outline package (SSOP) has a pin spacing of 0.635mm. Likewise, there are many versions depending mainly of the pin spacing and thinness.
    • Quad flat pack (QFP): This device is used for various complex parts that demand high pin counts. You can find them in microcontrollers as well as multi-channel codes. Shrink quad flat pack (SQFP) is one of the popular variants of QFP. Both these packages have thin leads, and demand a thin land pattern. The pricing of QFPs usually varies based on the number of pads included.
    • Plastic leaded chip carrier (PLCC): This package is square shaped and uses J-lead pins. The pin spacing here is 1.27mm.
    • Ball grid array (BGA): BGAs can be availed in various pin counts and pitch sizes. They do not have leads and are available in various types. These surface mount devices can self-align even during reflow, which makes them popular. There are two main types of BGAs- plastic and ceramic BGA. The ceramic BGAs are further categorized into Ceramic Column Grid Array (CCGA) and Ceramic Ball Grid Array (CBGA). Plastic BGAs are known as PBGA.

While these packages have identical IC SMDs, there are some packages with multiple types of IC SMDs, which are gradually gaining traction. Some of these include thin small outline package (TSOP), shrink small outline package (SSOP), and very small outline package (VSOP).

If you are an OEM who requires a complex circuitry for your product to function, you can partner with an experienced PCB manufacturer and service provider. You may want to share your application requirements with the service provider and seek help in choosing the right materials, components, SMD packages, and so on for the PCBs. Sierra Assembly is a US-based manufacturer of PCBs and assemblies offering customized and end-to-end PCB assembly solutions.