Continuing our series on how to select components, we will discuss different IC packages in this blog. ICs are the backbone of electronic devices, and choosing the right IC requires considering factors like price, reliability, performance, and package, among others. In this blog, we will focus on demystifying different IC packages, so that you can make an informed decision when you select the IC for your next project. We have also included some links to popular ICs.
Before integrated circuits (ICs) are assembled onto the printed circuit boards (PCBs), they are put into packages with terminals called pins (or pads). Pins electrically connect the IC with rest of the PCB. There are many different types of IC packages which differ by size, pin count, pin location and mounting type — surface-mount or through-hole.
Each pin in an IC has a unique function, which you can see by looking at its datasheet. The dot on the IC shows the first pin, and you count the pins counter-clockwise. The corresponding function of the pin is identified from the datasheet.
Below is ATmega328P-AU along with corresponding pin diagram:
TQFP Package and the pin diagram of ATMEGA328P-AU
IC packages can either be through-hole or surface-mount. Through-hole ICs are easier to work with, because they can be used with breadboards or inserted into a PCB and soldered on the other side. Surface-mount ICs are meant to be soldered directly onto the surface of the PCB, and may be harder to assemble but have the advantage of smaller form factors. Some ICs such as DIPs or PLCCs can be placed into a socket for the easy replacement of devices during development. Let’s take a look at the different IC packages:
I. DIP Packages
DIPs or Dual Inline Packages are the most popular through-hole IC packages, and has two parallel rows of pins with rectangular housing. DIPs have a pin pitch of 0.1” or 2.54mm, and are commonly used with breadboards. They are commonly referred to as DIPn, where n is how many pins it has. DIP8 has two rows of 4 vertical pins. DIP28 has two rows of 14 vertical pins, and so on.
Applications: DIP ICs are easy to handle and are widely used in prototyping applications, like with breadboards. DIP ICs are commonly used with DIP sockets, which allow the easy replacement of the ICs without re-soldering. A popular example of this is the Arduino Uno, which has a DIP socket to help replace the ATmega328P-PU MCU when needed. For mass production, surface-mount packages are preferred as they are smaller in size.
DIP4 package: Vishay’s VO617A series optocoupler
DIP8 package: Some TI’s OPA series op-amps
DIP14 package: LM339N comparators
DIP28 package: ICM7218 LED drivers
DIP IC Sockets: TE Connectivity’s 1-2199 series
II. SOIC Packages
SOICs or Small Outline Integrated Circuit packages are surface-mount equivalents of DIP packages. Among the surface-mount packages, SOIC packages are the easiest to solder. The pin pitch, or the distance between pins, for an SOIC package is 0.05” or 1.27mm which is half of DIP package. While it may depend on a specific part, the maximum height of an SOIC package is 1.75mm. They are commonly referred as SOIC-n or SO-n, where n is the number of pins.
Applications: SOIC ICs are preferred over DIP ICs, as they take up to 50% less space than DIP ICs, so more ICs will fit into the the same printed circuit board area. As they are surface-mount, SOIC packages are easier to assemble for mass production with reflow soldering compared to DIP ICs.
III. SOP Packages
SOPs or Small Outline Packages are surface-mount packages that are smaller than SOIC packages and with pin pitches lesser than 1.27mm. They can have a few different variants:
SSOP Packages: SSOPs, or shrink small outline packages, have a pin pitch of 0.65mm which is almost half of the SOIC package. Their height is similar to SOIC package.
TSOP Packages: TSOPs, or thin small outline packages, have a thinner bodies than SSOP packages and can have a pin spacings as small as 0.5mm. They are commonly used with memory modules, like Flash memory.
TSSOP Packages: TSSOPs or thin-shrink small outline packages, are even smaller and come with a maximum height of 1.2mm (SOIC packages have a maximum height of 1.75mm). Pin pitches can vary, so it’s best to check the data-sheets, but 0.5mm and 0.65mm pin pitches are common.
IV. QFP Packages
QFPs or Quad Flat Packages are surface-mount packages with pins extending from all four sides. QFP packages can have pins ranging from 32 to over 300 pins with pin pitches between 0.4mm and 1mm. QFP packages have a high number of pins and thus enable large number of connections with rest of the PCB. High pin counts can lead to high track density, so take care to ensure you follow design rules.
There are a few different kinds of QFP packages, but LQFPs, or low profile quad flat packages, and TQFPs, or thin quad flat packages, are the most popular. High quality versions of QFPs are made using ceramic and it is called ceramic QFP or CQFP. Package can also be made of plastic and it is called plastic QFP or PQFP.
LQFP Package: Low profile QFP package has lower height compared to QFP package – height of 1.4mm is common. Pin pitches of 0.4mm, 0.5mm, 0.65mm and 0.8mm are available.
TQFP Package: Thin QFP package has even lower height compared to LQFP package, with height of 1mm is quite common. TQFP can be placed on the QFP footprint if they have the same pitch.
LQFP Package: STM’s STM32F series microcontrollers
TQFP Package: Microchip’s PIC32M microcontrollers
V. QFN Packages
QFNs or Quad Flat No-Leads Packages do not have lead pins on the sides and all the connections are at the bottom of the chip. QFN packages also include an exposed thermal pad at the bottom of the package to ease the heat transfer into the PCB. Also, QFN ICs have shorter bond wire lengths and hence have lower inductance than leaded packages. Pin pitch of 0.5mm is common and the body height can be as low as 0.9mm.
Applications:. QFN ICs are very popular because of lower cost, smaller form factor, good electrical and thermal performance. Many of the microprocessors, sensors and other ICs come in QFN package. As QFN ICs do not have leaded terminals, they are harder to assemble by hand and need techniques like reflow soldering.
There are a few different kinds of QFN packages, but TQFN – thin quad flat no-leads package, and VQFN – very thin quad flat no-leads package are most popular. DFN or dual flat no-leads package has dual rows of pins compared to four rows of QFN package.
VI. BGA Packages
BGAs or Ball Grid Array packages have pins placed in a grid pattern on the under-surface of the package. Instead of using the usual method of providing connections using pins, BGA ICs use balls of solder to provide connection.
Advantages: They provide high density of connections as the entire under-surface can be utilized for connections. They have superior thermal performance as the heat generated by the IC can be conducted out into the PCB more effectively. Also, since they have short distance between package and the PCB, they have lower inductance – which leads to superior electrical performance too.
Disadvantages: The main disadvantage of BGA ICs is assembling them as it is often very difficult to hand-solder them, and reliable reflow techniques are needed to solder them. Another issue is difficulty of inspection after soldering. Often, X-ray machines or special scanning machines are needed.
LGA or Land Grid Array packages are similar to BGAs but instead of using solder balls to provide connection, they use flat contacts to connect to the PCB. PGA or Pin Grid Array uses pins for connection to PCB. Below is a picture comparing BGA and LGA with the latter having flat contacts:
BGA has solder balls, LGA has flat contacts for connections
Apart from the IC packages discussed in this guide, there are Plastic Leaded Chip Carrier or PLCC which has J-shaped terminals and have the advantage that they can be soldered directly to the PCB as well as can be used with PLCC sockets.
VII. SOT Packages
SOT or small outline transistor is a footprint commonly used for discrete surface mount transistors, diodes and voltage regulators. SOT23 and SOT223 are popular variations of the SOT package. SOT223 is used for devices with more power requirements, and one of the terminals is usually an exposed thermal pad.
SOT23-3: MMBT3904 NPN transistor
SOT23-5: TI’s LP2985 LDO voltage regulator
SOT223-5: Microchip’s MCP1755 LDO voltage regulator
Packages for Discrete Semiconductors:
Among the packages for discretes is SOD or small outline diode package which comes with two terminals and mainly used for diodes.
Also, TO or transistor outline packages are commonly used for through-hole applications.
TO-92 is popular for transistors and are popular for hobbyist applications. They are cheap but they cannot handle a lot of power.
TO-220 on the other hand can dissipate more power, and can even be mounted to a heat sink to dissipate power. TO-220 is also used for voltage regulators such as LD1117, L7805 and LM317.
TO-263 or D2PAK is the surface mount equivalent of TO-220 and can dissipate higher amounts of power. The pins are bent so that the IC can be placed on the surface of PCB. Examples of voltage regulators using this package are UA7805 and LM2576.
SOD: 1N4148WS diode
TO-92: 2N7000 N-Channel MOSFET
TO-220: TIP120 high power NPN BJT
TO-263 or D2PAK: FQB22P10 P-Channel MOSFET
You are likely to find most of the ICs available in the packages that we discussed in this guide. To learn about the packages for passive components (such as 0402, 0603, and 0805) and connectors, do read our blogs on how to select a capacitor, resistor, inductor and connectors.
It was great demystifying all the different IC packages, if you have any comments or feedback leave it below, or in our community Slack chat room.