Introduction
Surface Mount Device (SMD) components are integral elements in the world of electronics. These tiny devices have paved the way for miniaturized circuits, enabling sleeker designs and enhanced performance. SMD components play a crucial role in the functioning of electronic circuits, making it essential for anyone involved in electronics to understand them. Whether you're an electronics enthusiast, a professional engineer, or simply curious about the inner workings of your everyday devices, this guide will provide you with a comprehensive understanding of SMD components.
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Understanding SMD Components
Surface-mount devices (SMDs) are electronic components mounted directly to the surface of a printed circuit board (PCB). They have largely replaced through-hole technology (THT) components, which require holes to be drilled in the PCB for installation. SMD components are preferred due to their smaller size and higher component density, which allows for more compact and efficient circuit design.
SMD components play a critical role in the functioning of electronic devices. They are used in virtually all modern electronic equipment, including computers, mobile phones, and home appliances. Their primary function is to control the flow of electricity in a circuit, but they can also perform various other tasks depending on the specific component type.
The use of SMD components offers several advantages over traditional through-hole components. Firstly, they are smaller and lighter, which allows for the creation of smaller and more portable electronic devices. Secondly, they can be placed on both sides of a PCB, increasing the circuit density and allowing for more complex circuit designs. Finally, SMD components can be installed using automated equipment, which reduces manufacturing costs and increases production speed.
Basic Types of SMD Components
Surface Mount Device (SMD) components come in a variety of types, each with its unique function in an electronic circuit. The basic types of SMD components include resistors, capacitors, and inductors.
Resistors
Resistors are one of the most common types of SMD components. They are used to limit the flow of electric current in a circuit. The resistance of a resistor is measured in ohms (Ω), and SMD resistors typically have resistance values ranging from 1 ohm to several megaohms.
Resistors on the Printed Circuit Board Assembly (PCBA) of an electronic device
SMD resistors come in various types, each designed for a specific application. For instance, thin-film resistors are known for their high precision and stability, making them ideal for precision applications such as instrumentation. They are typically available in resistance values ranging from 1 ohm to 3 megaohms, with tolerance values as low as 0.01%. [1]
On the other hand, thick-film resistors are more common and less expensive than thin-film resistors. They are typically used in general-purpose applications where high precision is not required. Thick-film resistors are available in a wide range of resistance values, from 1 ohm to several gigaohms, with tolerance values typically ranging from 1% to 5%.
Another type of SMD resistor is the current sense resistor, which is used to measure electric current. These resistors have very low resistance values, typically less than 1 ohm, and are designed to produce a voltage drop, proportional to the current flowing through them. This voltage drop can then be measured and used to calculate the current.
In addition, specialty resistors such as wire-wound resistors, known for their high power handling capability, and metal foil resistors offer extremely high precision and stability. The choice of resistor type depends on the specific requirements of the application.
Capacitors
Capacitors are another fundamental type of SMD component. They store and release electrical energy in a circuit, acting like a temporary battery. Capacitors are used in various applications, including filtering noise, stabilizing voltage, and storing energy for later use.
Capacitors on the Printed Circuit Board of an electronic device
The capacitance of a capacitor, which measures its ability to store electrical charge, is measured in farads (F). However, most capacitors used in electronic circuits have capacitance values in the microfarad (µF), nanofarad (nF), or picofarad (pF) range.
SMD capacitors come in several types, each with its unique characteristics. Ceramic capacitors are the most common type of SMD capacitor. They are inexpensive, have a wide range of capacitance values, and are non-polarized, meaning they can be installed in either direction. However, their capacitance can vary with temperature and voltage, which can disadvantage precision applications.
Tantalum capacitors are another type of SMD capacitor. They offer higher capacitance values and better stability than ceramic capacitors, but they are polarized and more expensive. Tantalum capacitors are typically used in power supply circuits due to their high capacitance-to-volume ratio. [2]
Another type of SMD capacitor is the film capacitor. Film capacitors are known for their high precision, stability, and reliability. They are typically used in high-frequency applications such as RF circuits and high-quality audio equipment.
Finally, there are electrolytic capacitors, which offer very high capacitance values but have lower precision and stability than other capacitors. They are polarized and have a limited lifespan, especially when operated at high temperatures. Electrolytic capacitors are typically used in power supply circuits requiring high capacitance.
Each type of capacitor has its strengths and weaknesses, and the choice of capacitor type depends on the specific requirements of the application.
Recommended Reading: How to Discharge a Capacitor: Comprehensive Guide
Inductors
Inductors are another type of SMD component that play a crucial role in electronic circuits. They are used to store energy in a magnetic field when electric current flows through them. Inductors are primarily used in analog circuits and power supplies to filter out high-frequency noise and stabilize the current flow.
Toroidal inductors and a transformer during the PCB manufacturing of an electronic device
The inductance of an inductor, which measures its ability to store energy in a magnetic field, is measured in henries (H). However, most inductors used in electronic circuits have inductance values in the microhenry (µH) or nanohenry (nH) range.
SMD inductors come in several types, each with its unique characteristics. Wirewound inductors are the most common type of SMD inductor. They are made by winding a wire around a magnetic core, offering high inductance values and high current handling capability. However, their inductance can vary with frequency, disadvantaging high-frequency applications.
Another type of SMD inductor is the multilayer inductor. Multilayer inductors are made by stacking multiple layers of a magnetic material, and they offer high inductance values in a small package. However, they have lower current handling capability compared to wire-wound inductors.
Ferrite bead inductors are a particular type of inductor used to filter out high-frequency noise in electronic circuits. They are made by threading a wire through a bead made of ferrite material. [3] Ferrite bead inductors have high resistance at high frequencies, which allows them to filter out the high-frequency noise.
Each type of inductor has its strengths and weaknesses, and the choice of inductor type depends on the specific requirements of the application. For instance, a wire-wound inductor might be chosen for a power supply circuit due to its high current handling capability. In contrast, a ferrite bead inductor might be chosen for a signal processing circuit due to its noise-filtering capability.
Advanced Types of SMD Components
Advanced types of SMD components or Small Outline Transistors (SOT) include diodes, transistors, and integrated circuits (ICs). These components are more complex than basic surface mount components and are used in a wide range of applications, from power management to signal processing.
Diodes
Diodes are semiconductor devices that allow current to flow in one direction while blocking it in the opposite direction. They are used in various applications, such as rectification, voltage regulation, and signal processing.
Semiconductor diode during the PCB assembly process of an electronic device
SMD diodes come in several types, each with its unique characteristics and applications. One common type is the rectifier diode, which converts alternating current (AC) to direct current (DC) in power supplies. Rectifier diodes have a high current handling capability and can withstand high reverse voltages.
Another type of SMD diode is the Schottky diode, known for its low forward voltage drop and fast switching speed. Schottky diodes are used in high-frequency applications, such as radio frequency (RF) circuits and switching power supplies. [4]
Zener diodes are another type of SMD diode, used for voltage regulation. They have a specific voltage limit beyond which they begin to conduct in the reverse direction. This property allows them to maintain a constant voltage across their terminals, making them useful for voltage regulation in electronic circuits.
Light-emitting diodes (LEDs) are a particular type of diode that emits light when a current flows through them. SMD LEDs are used in a wide range of applications, from indicator lights to display panels.
A triode is a vacuum tube consisting of three electrodes: a heated filament or cathode, a grid, and a plate (anode). SMD triodes are used in a wide variety of electronic devices, and they offer a number of advantages over traditional through-hole triodes.
Each type of diode has its strengths and weaknesses, and the choice of diode type depends on the specific requirements of the application. For instance, a rectifier diode might be chosen for a power supply circuit due to its high current handling capability, while a Schottky diode might be chosen for a high-frequency application due to its fast switching speed.
Transistors
Transistors are semiconductor devices that amplify or switch electronic signals and electrical power. They are one of the most important components in modern electronics industry and are used in various applications, from digital logic circuits to power amplifiers.
Transistor on an LCD TV printed circuit board
SMD transistors come in several types, each with its unique characteristics and applications. One common type is the bipolar junction transistor (BJT), which consists of two semiconductor junctions and can be NPN or PNP. BJTs are used in various applications, such as amplification, switching, and voltage regulation.
Another type of SMD transistor is the field-effect transistor (FET), which operates by controlling the flow of current through a semiconductor channel. FETs are further divided into two main categories: junction gate field-effect transistors (JFETs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). [5] JFETs are typically used in low-noise, high-input impedance applications, while MOSFETs are used in high-speed switching and power management applications.
MOSFETs are particularly popular in modern electronics due to their high switching speed, low power consumption, and high input impedance. They come in two main types: enhancement-mode MOSFETs and depletion-mode MOSFETs. Enhancement-mode MOSFETs are normally off and require a gate voltage to turn on, while depletion-mode MOSFETs are normally on and require a gate voltage to turn off.
Each type of transistor has its strengths and weaknesses, and the choice of transistor type depends on the specific requirements of the application. For instance, a BJT might be chosen for a linear amplifier circuit due to its high current gain, while a MOSFET might be chosen for a switching power supply due to its high switching speed and low power consumption.
Recommended Reading: PMOS VS NMOS: Focus on Two Main Forms of MOSFET
Integrated Circuits (ICs)
Integrated Circuits (ICs) are complex electronic components that contain multiple transistors, diodes, resistors, capacitors, and other components on a single semiconductor chip. ICs are used in various applications, from microprocessors and memory chips to analog-to-digital converters and power management circuits.
Integrated Circuit (IC) on computer motherboard
SMD ICs come in various types, each designed for a specific application. One common type is the digital IC, which includes microprocessors, microcontrollers, and digital signal processors (DSPs). Digital ICs are used in applications requiring processing and manipulating digital data, such as computers, smartphones, and digital audio equipment.
Another type of SMD IC is the analog IC, which includes operational amplifiers (op-amps), comparators, and voltage regulators. Analog ICs are used in applications that involve the processing of analog signals, such as audio amplifiers, sensors, and power supplies. Mixed-signal ICs combine digital and analog circuits on a single chip. They are used in applications requiring digital and analog processing, such as data converters and radio frequency (RF) circuits.
Power management ICs are a specialized type of SMD IC, designed to manage and distribute power in electronic devices. They include voltage regulators, battery chargers, and power switches. Power management ICs are used in various applications, from mobile phones and laptops to electric vehicles and solar power systems.
Each type of IC has its strengths and weaknesses, and the choice of IC type depends on the specific requirements of the application. For instance, a digital IC might be chosen for a computer motherboard due to its high processing capability. In contrast, an analog IC might be chosen for an audio amplifier circuit due to its ability to process analog signals.
Recommended Reading: What is a Semiconductor? A Comprehensive Guide to Engineering Principles and Applications
SMD Component Sizes and Codes
SMD components come in various sizes and codes, which are essential to understand when selecting and using these components in electronic circuits. The size and code of an SMD component provide information about its physical dimensions and electrical characteristics, allowing engineers and technicians to choose the appropriate component for a specific application.
SMD components are typically identified by a standardized code system, which consists of alphanumeric characters. This code system varies depending on the type of component, such as resistors, capacitors, or inductors.
Resistor Sizes and Codes
SMD resistors are identified by a three or four-digit code, which indicates their resistance value, and tolerance. The first two or three digits represent the significant figures of the resistance value, while the last digit indicates the multiplier. For example, a resistor with the code "103" has a resistance value of 10 x 10^3 ohms, or 10 kilohms.
Resistors of different codes and sizes
SMD resistors also come in various standard sizes, denoted by a two-digit code, such as , , or . The first two digits represent the length of the resistor in hundredths of an inch, while the last two digits represent the width. For example, a resistor measures 0.06 inches in length and 0.03 inches in width.
Capacitor Sizes and Codes
SMD capacitors are identified by a three-digit code, which indicates their capacitance value and voltage rating. The first two digits represent the significant figures of the capacitance value, while the last digit indicates the multiplier. For example, a capacitor with the code "104" has a capacitance value of 10 x 10^4 picofarads, or 100 nanofarads.
Capacitors of different colors and sizes
Like resistors, SMD capacitors come in various standard sizes, such as , , or . The size code follows the same convention as resistors, with the first two digits representing the length and the last two digits representing the width.
Inductor Sizes and Codes
SMD inductors are identified by a four-digit code, which indicates their inductance value and tolerance. The first three digits represent the significant figures of the inductance value, while the last digit indicates the multiplier. For example, an inductor with the code "" has an inductance value of 10 x 10^2 microhenries or 1 millihenry.
Toroidal inductors and transformers of different specifications
SMD inductors also come in various standard sizes, similar to resistors and capacitors. The size code follows the same convention, with the first two digits representing the length and the last two digits representing the width.
Understanding surface mount component sizes and codes is crucial for selecting the appropriate components for a specific application and ensuring the proper functioning of electronic circuits.
SMD Component Selection and Application
Careful selection of SMD components
Selecting the appropriate SMD packages for a specific application is crucial to ensure the proper functioning and performance of an electronic circuit. Several factors need to be considered when choosing SMD components, which include:
Electrical Characteristics
The electrical characteristics of an SMD component, such as resistance, capacitance, or inductance, must be suitable for the intended application. For example, a resistor with the correct resistance value is necessary to limit the current flow in a circuit. In contrast, a capacitor with the appropriate capacitance value is required for filtering or energy storage purposes. It is essential to consult datasheets and reference designs to determine the appropriate electrical characteristics for a specific application.
Physical Dimensions
The physical dimensions of an SMD component, such as its length, width, and height, must be compatible with the available space on the printed circuit board (PCB). Additionally, the component size should be suitable for the manufacturing process, as smaller components may require more precise placement and soldering techniques. Standard SMD component sizes, such as , , or , can be used as a starting point when selecting components for a specific application.
Compatibility with Other Components
SMD components must be compatible with other components in the circuit, both electrically and mechanically. For example, a capacitor with a high voltage rating may be required if it is connected to a high-voltage power supply, while a resistor with a high power rating may be necessary if it is used in a high-current application. Additionally, components with similar temperature coefficients should be used in temperature-sensitive applications to ensure consistent performance over a wide temperature range.
Examples of SMD Component Selection and Application
In a power supply circuit, a combination of SMD resistors, capacitors, inductors, diodes, and transistors may be required to regulate and filter the output voltage. The selection of these components will depend on factors such as the input voltage, output voltage, load current, and efficiency requirements.
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In a radio frequency (RF) circuit, SMD capacitors and inductors may create filters that allow specific frequencies to pass while blocking others. The selection of these components will depend on the desired filter characteristics, such as the center frequency, bandwidth, and attenuation.
In a microcontroller-based circuit, SMD resistors and capacitors may be used for pull-up or pull-down resistors, decoupling capacitors, and timing circuits. The selection of these components will depend on factors such as the microcontroller's input and output requirements, power supply voltage, and timing constraints.
By carefully considering the electrical characteristics, physical dimensions, and compatibility with other components, the appropriate SMT components can be selected for a specific application, ensuring the optimal performance of the electronic circuit.
Soldering and Handling SMD Components
Soldering and handling SMD components require specific techniques and precautions to ensure the proper functioning and reliability of electronic circuits. SMD connectors are typically soldered to the PCB using a surface mount technology (SMT) process. The small size and delicate nature of SMD components make them more susceptible to damage during soldering and handling processes.
Soldering SMD component on Printed Circuit Board
Soldering Techniques
Soldering SMD components typically involves solder paste, a mixture of solder particles and flux. The solder paste is applied to the PCB pads using a stencil or a syringe, and the SMD components are then placed on the pads using tweezers or automated pick-and-place machines. The PCB is then heated in a reflow oven, which melts the solder paste and forms a reliable electrical and mechanical connection between the component and the PCB. Ball Grid Array (BGA) components are typically more difficult to solder and desolder than other SMD components, as they are located on the underside of the package.
Several key factors are to consider when soldering SMD components:
Solder paste quality: The solder paste should have the appropriate viscosity and metal content to ensure proper wetting and adhesion to the PCB pads and component terminals.
Stencil design: The stencil should be designed to provide the correct amount of solder substrate on each pad, ensuring a reliable connection without causing solder bridges or insufficient solder joints.
Reflow profile: The reflow oven should be programmed with the appropriate temperature profile, which includes preheating, soaking, reflow, and cooling stages. This ensures that the solder paste melts and forms a reliable joint without damaging the components or the PCB. [6]
Component alignment: The SMD components should be accurately placed on the PCB pads to ensure proper alignment and electrical connection.
QFP packages are commonly used for high pin count SMD integrated circuits, SOIC, or Plastic Leaded Chip Carrier (PLCC) components such as microprocessors, memory chips, and field-programmable gate arrays.
Handling Precautions
Handling SMD components requires care and attention to avoid damage and ensure the reliability of the electronic circuit. Some key precautions to consider when handling SMD packages include:
Electrostatic discharge (ESD) protection: Many SMD components, such as ICs and transistors, are sensitive to electrostatic discharge, which can cause permanent damage. It is essential to use ESD-safe tools, such as tweezers and workstations, and to wear ESD wrist straps when handling these components. [7]
Mechanical stress: SMD components can be damaged by excessive mechanical stress, such as bending or twisting. Care should be taken when handling and placing these components to avoid applying excessive force.
Temperature and humidity control: SMD components can be sensitive to temperature and humidity, which can affect their electrical characteristics and reliability. It is essential to store and handle these components in a controlled environment to ensure their long-term performance.
By following the appropriate soldering techniques and handling precautions, SMD or SMT components can be successfully integrated into electronic circuits, ensuring optimal performance and reliability.
Recommended Reading: Solder Reflow: An In-Depth Guide to the Process and Techniques
Conclusion
In conclusion, understanding the various types of SMD components, their functions, and applications is essential for anyone involved in electronics. From SOT components like resistors, capacitors, and inductors to advanced components such as diodes, transistors, and integrated circuits, each component plays a crucial role in the functioning of electronic circuits. Proper selection, soldering, and handling of these components are vital to ensure the optimal performance and reliability of electronic devices.
FAQs
Q: What are SMD components?
A: SMD (Surface Mount Device) components are electronic components that are mounted directly onto the surface of printed circuit boards (PCBs). They are used in a wide range of electronic devices and offer advantages such as smaller size, higher component density, and compatibility with automated manufacturing processes.
Q: What are the basic types of SMD components?
A: The basic types of SMD components include resistors, capacitors, and inductors. Each type has a specific function in electronic circuits, such as limiting current flow, storing electrical energy, or filtering signals.
Q: What are some advanced types of SMD components?
A: Advanced types of SMD components include diodes, transistors, and integrated circuits (ICs). These components are more complex than basic SMD components and are used in a wide range of applications, from power management to signal processing.
Q: How are SMD components sized and coded?
A: SMD components are sized and coded using standardized alphanumeric codes that indicate their physical dimensions and electrical characteristics. These codes vary depending on the type of component, such as resistors, capacitors, or inductors.
Q: What precautions should be taken when soldering and handling SMD components?
A: When soldering and handling SMD components, it is essential to use appropriate soldering techniques, such as using solder paste and a reflow oven, and to follow handling precautions, such as protecting against electrostatic discharge (ESD), avoiding excessive mechanical stress, and controlling temperature and humidity.
References
[1] Passive Components Blog. SMD Surface Mount Chip Resistor Selection Guide [Cited October 17] Available at: Link
[2] Electronics Notes. Understanding Tantalum Capacitors: technology, types, leaded, SMD [Cited October 17] Available at: Link
[3] Altium. How Do Ferrite Beads Work and How Do You Choose the Right One? [Cited October 17] Available at: Link
[4] Byjus. Schottky Diode [Cited October 17] Available at: Link
[5] ScienceDirect. Field Effect Transistor [Cited October 17] Available at: Link
[6] Research Gate. SMD Reflow Soldering: A Thermal Process Model [Cited October 17] Available at: Link
[7] ST Microelectronics. ESD Protection [Cited October 17] Available at: Link
I have lately been trying to familiarize myself with SMT/SMD packages of electronics components and I thought I&#;ll share my findings with all of you so that it might be of some use to others
An overview of the most common surface mount package sizes and formats, such as QFP, TSOP, , ,etc. will be discussed here.
Surface mount technology, SMT components come in a variety of packages.
As surface mount technology has improved many packages have decreased in size. Additionally there is a variety of different SMT packages for integrated circuits dependent upon the interconnectivity required, the technology being used and a variety of other factors.
Integrated circuits (ICs) and electronic components come in a bewildering variety of shapes and sizes (often called &#;packages&#;), and it can be difficult for any beginner to keep track of what the main characteristics are of each package type. ICs are often referred to by abbreviations such as LQFP, TQFP, TSOP, SSOP, etc., and discrete components (resistors, capacitors, etc.) are typically given names that correspond to their physical dimensions, such as , , , and . To make things even worse, the names of discrete components are sometimes different depending on whether you are using metric or imperial measurements (cms versus inches), although imperial names (, , etc.) are common even in European and other metric regions.
This guide will hopefully serve two purposes: To give you an overview of the most common IC and component packages and sizes, and to help you decide which package type you should be buying or using in different situations.
Discrete Components
A &#;discrete component&#; is a fancy label for the single circuit electronic components that make up most of your board, and they are generally divided into two categories: passive components (Resistors, Capacitors, Diodes, etc.) and active components (Transistors, LEDs, etc.). Most of these discrete components come in common shapes and sizes, and are relatively easy to identify.
Resistors
Resistors, along with many other discrete components, most commonly come in rectangular packages named after their physical dimensions. The most common of these standard packages sizes are , , and . The numbers represent &#;1/100th of an inch&#;, meaning an package is theoretically 0,06&#; x 0,04&#; (1,524mm x 1,016mm). I say &#;theoretically&#; because there is always some variation between manufactuers and different component types.
It&#;s worth noting that resistors are only able to handle a certain amount of electrical current before burning out (a 1/4 watt resistor, for example, can handle twice as much power &#; or about 41% more current &#; as a 1/8 watt resistor). Since there is a relationship between the physical size of a component and the amount of current that it can safely handle, manufacturers need to increase the size of the resistors as the rating goes up. For example, 1/8 watt resistors are widely available in packages, but you will need to move up to or larger if you need a 1/2 watt or higher resistor.
If you are manually placing the components on the board, or hand-soldering them, it&#;s best to use or larger components. can be difficult to precisely handle due to its very small size. , and resistors (seen below) can all be hand-soldered with a bit of practice and perhaps some magnification.
Capacitors
Capacitors act as &#;mini-batteries&#; of sorts, helping ensure that you have a smooth, steady power supply available to all your on-board components and peripherals. They come in a wide variety of packages, depending on the type of capacitor used and their technical specifications. There are three main types of capacitors you are likely to encounter in electronics:Ceramic, Tantalum and Electrolytic, with each type generally having it&#;s own set of standard package sizes.
Ceramic capacitors typically come in the common , or packages. Tantalum capacitors have their own standard rectangular package sizes, referred to by letters A, B, C, D, E, etc. Electrolytic capacitors are usually round and &#;stick up&#; from the board, but there aren&#;t really any strictly followed standard sizes used by all manufacturers. As such, you may need to pay a bit more attention when adding electrolytic capacitors to your board. For all capacitors, the larger their &#;capacity&#;, the larger the physical package will necessarily be.
While there are no fixed rules, tantalum capacitors are often yellow, and electrolytic capacitors are typically round, as can be seen in the photos below. As well, you need to be careful when placing tantalum and electrolytic capacitors since they are &#;polarised&#;, meaning they have a + and a &#; side, and absolutely have to be placed in the proper direction. To help you with this, the + side on tantalum and electrolytic capacitors is usually marked by a solid line or bar, as seen in the last two images below. Ceramic capacitors are not polarised and can be place in any direction.
LEDs
Surface-mount LEDs (or Light Emitting Diodes) most commonly come in , and packages, and are polarised meaning that they need to be placed in the right direction on your board. The electrical current on your LEDs should flow from the Anode (A) to the Cathode (K) side of your LED, with a current-limiting resistor to keep the LED from drawing too much current and burning out (see our entry on &#;Ohm&#;s Law&#; for information on this and a calculator to help you determine which resistor to use with your LED). Before placing any LEDs on your board, be sure to read the datasheet to determine which side is A and which is K.
Diodes, Transistors, and other discrete components
While Diodes are available in SOT223 and SOT23 packages (see below), they also have their own standard package sizes, with one of the more common sets being SMA, SMB and SMC (an SMA diode can be seen in the second photo below). SMA is probably the most common in small microcontroller projects.
Other discrete components: While many discrete components come in standard package sizes (, , etc.), there are certain components that require three or more pins to function and they often come in a set of standard package sizes with the SOT prefix such as SOT223 or SOT23. A very common example is the LM adjustable voltage regulator seen in the first photo below, which is in a four pin SOT223 package. Depending on the number of pins, the package names vary slightly. For example, while a SOT223 device has four pins (three on the bottom and one on top), a SOT223-4 device has 5 pins (four on the bottom), and a SOT223-5 device has 6 pins (five on the bottom). The same is true for SOT23 packages: while a normal SOT23 has 3 pins (one on top, and two on the bottom) a SOT23-5 has 5 pins (two on top, and three on the bottom). A third SOT package you may encounter is the three pin SOT323, which has one pin on top and two pins on the bottom. (If you&#;re having a hard time to understand the differences between these admittedly similar package sizes, we&#;ve added some footprint outlines in the images below.)
Large Integrated Circuits
QFP, SOIC, TSOP, and other &#;leaded&#; packages
These types of IC packages are easy to identify because they have external &#;leads&#; (or &#;pins&#;) that are soldered directly to the PCB. They are probably the most common type of IC package that you are likely to encounter, though &#;leadless&#; packages like QFN (see below) are becoming more and more common.
While a wide variety of leaded packages exist, three of the most common families are QFP (Quad-Flat Package), TSOP (Thin Small-Outline Package) and SOIC (Small-Outline Integrated Circuit). Variations exist in each of these &#;families&#;, such as LQFP, TQFP, etc., but the differences are minimal and often refer to the physical height of the package.
In general, leaded packages will probably be the easiest to work with for prototyping and small scale production and should be given preference if you have the choice since they can be easily hand-soldered and removed from PCBs, and arevery easy to inspect. (QFN packages, which have their leads hidden underneath the edge of the chip can still be hand-soldered, but inspection is harder and some care is required when working with them. BGA packages can&#;t be hand-soldered at all, and generally require expensive equipment for both placement and inspection.)
QFN (Quad Flat No leads)
QFN packages have their leads hidden underneath the chip, and are visible when you look at the chip from the side. They are becoming more and more common due to the fact that they are less fragile than QFP or other &#;leaded&#; parts (where the external leads can be bent or damaged) and because they take up less physical space than parts with external leads.
QFN packages can be hand-soldered, but it takes a bit more effort, and you will likely find them easier to solder with solder paste than a with traditional soldering iron.
BGA (Ball-Grid Array) and CSP (Chipscale)
Ball-Grid Array and Chipscale are miniaturised packages that are designed to add the maximum number of pins in the smallest physical package size possible. Rather than having one row of pins along the edge of the chips &#; as is the case with both QFP/SOIC/TSOP and QFN/DFN &#; BGA and Chipscale packages have several rows of &#;balls&#; underneath, allowing manufacturers to add a much higher pincount to their chips than would be possible with any other package type. This is essential in situations where space is at a premium, such as in mobile phones or small hand-held devices, but as microcontrollers become more and more complex and add more features the need for more physical pins also necessitates the use of BGA in most modern MCUs. It&#;s difficult to find ARM9 processors in anything other than BGA, for example.
Unfortunately, BGA packages are much more difficult and expensive to work with since they require specialised equipment for inspection and are very difficult to place by hand. They&#;re designed for large production volumes and automated machinery, and you should probably choose a QFP (etc.) or QFN variety if one is available for your IC or MCU. (Unfortunately, this isn&#;t always the case). An exception to this is Chipscale (CS/CSP) packages, which often have only a few pins (6 or 8 isn&#;t uncommon). While somewhat challenging to work with due to their size, you can hand-place and inspect small chipscale packages under a microscope, so long as there is only one row of balls on each side (i.e., there isn&#;t a second layer of balls in the middle that you wouldn&#;t be able to see by turning the chip 90° on it&#;s side and looking at it under a microscope).
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