Surface Mount Technology and Surface Mount Device

SMT and SMD are related terms in electronics, especially in the manufacturing and assembly processes.

SMT is a process technology and methodology used to mount electronic components that are mounted on the surface of a PCB. This includes designing the PCB, adjusting the solder paste application, component placement (pick and place), reflow soldering and automatic optical control (AOI). SMT enables the use of various surface-mountable components, designed specifically to be directly mounted, including CHIP, MELF, QFN (Quad Flat No Leads), QFPs (Quad Flat Packages), SOICs (Small Outline Integrated Circuits) and BGA (Ball Grid Array).

SMD components differ from THT components, as they concern only those mounted directly onto the PCB surface. These components have soldering pads, terminals, or balls on their lower surface, facilitating their surface mounting onto the PCB. SMD components come in a wide range of types and functionalities. From the typical passive chip resistors, chip capacitors, through semiconductor diodes, LED diodes, transistors, and various very large-scale integration components (IC).

SMT is a broad term that encompasses the entire surface-mount assembly process, while SMD refers specifically to those components mounted using the SMT process. Understanding this distinction enables effective communication and collaboration with professionals in the industry, to ensure the successful integration of these advanced technologies into electronic designs.

How to Identify SMD Components from Appearances - Fast and Easy

SMD components, or surface mount components, are electronic components to be mounted on printed circuit boards to function. How to identify SMD components from their appearances? This article will guide you to identify surface mount components fast and easily.

Part 1: Identify SMD Resistors

SMD resistors are basic surface mount components that limit the current passing through them. "R" stands for resistance, and the unit of resistance is Ohm (Ω). 1KΩ equals to 1000Ω, 1MΩ equals to 1000000Ω.

There are two methods to indicate the resistance value on the SMD resistors' appearance.

1.In Arabic numbers: the first two numbers indicate the absolute numbers of the resistance value, and the last number means the power of 10.

For example, 103 means 10000Ω, 391 means 390Ω, and 473 means 47000Ω.

2.In a combination of Arabic numbers and R: the Arabic numbers before the R stand for the whole part of the resistance value, and those after the R stand for the fractional part of the resistance value.

For example, R100 means 0.100Ω, 5R60 means 5.60Ω, 30R9 means 30.9Ω.

Classification of SMD resistors: according to the use differences, there are normal resistors, precision resistors, power resistors, high voltage resistors, high-resistance resistors, and high-frequency resistors.

Part 2: Identify SMD Capacitors

SMD capacitors are PCB parts consisting of two metal pieces separated by an insulator and mainly used to store energy. " C" stands for capacitance, and the unit of capacitance is Farad (F).

The unit F is too big for SMDs' capacitance, and we usually use the smaller unit μF, nF, pF. 1μF equals to 1000nF, 1nF equals to 1000pF.

There are two methods to indicate the capacitance value on the SMD capacitors' surface.

1. Directly denote the capacitance and working voltage on the capacitors, for example, 10μF/16V.

2. In a combination of Arabic numbers and working voltage: the first two numbers indicate the absolute numbers of the capacitance value, and the last number means the power of 10.

For example, 107 means 10 × 10^7pF (= 100μF), 225 means 22 × 10^5pF (=2.2μF)

Besides, on SMD capacitors, the capacitance is denoted by a combination of numbers and a letter.

The letter stands for capacitance tolerance. Here is a chart:

For example, 104J means 10 × 104pF (= 0.1μF), and the capacitance tolerance is ±5%.

Classification of SMD Capacitors

Ceramic capacitors: made up of a ceramic insulator with two terminals sprayed with silver and then sintered. On SMD capacitors' surface, C.CAPstands for ceramic capacitors.

Aluminum electrolytic capacitors: made up of an aluminum cylinder filled with liquid electrolyte (together as the negative electrode) and a curly aluminum strip (as the positive electrode) covered with an oxide film (as the insulator) plugged in it.

Tantalum electrolytic capacitors: made up of tantalum or niobium (as the positive electrode) and dilute sulfuric acid (as the negative electrode), the oxide film covered on tantalum or niobium as the insulator. TAN.CAP or TC stands for tantalum capacitors.

Note

All electrolytic capacitors are polar capacitors. The positive and negative electrodes of polar components can't be reversed during PCB assembly . On tantalum capacitors, the terminal printed with lines is the positive electrode. The sizes of tantalum capacitors from minimum or maximum are denoted by A, B, C, D ... J.

Part 3: Identify SMD Inductors

SMD inductors are basic electronic components that convert electrical energy into magnetic energy and store it. Inductors are made up of an enameled wire winding around an insulator. "L" stands for inductance, and the unit of inductance is Henry (H). 1H equals to 1000mH, and 1mH equals to 1000μH.

The method to indicate the inductance value on the SMD inductors' appearance is below.

In Arabic numbers: the first two numbers indicate the absolute numbers of the inductance value, and the last number means the power of 10.

For example, 470 means 47H, 101 means 100H, and 100 means 10H.

Part 4: Identify SMD Diodes and SMD Triodes

SMD diodes are unidirectional conductive electronic components. Diodes are also polar components, and the positive and negative electrodes can't be reversed. When currents flow from the positive electrode, the diode's resistance is extremely small. Vice versa, the resistance is extremely large. CR or D stands for diodes.

On SMD diodes, the terminal printed with lines is the negative electrode.

SMD triodes are control components that amplify currents. Q stands for triodes.

Part 5: Identify SMD ICs

SMD ICs are surface-mounted integrated circuits that integrate components such as diodes, resistors, capacitors, and inductors on an extremely small semiconductor and then packaged them. According to the packaging differences, the integrated circuits include PLCC, PPGA, PQFP, QFP, BGA, CSP, SSOP, etc.

Part 6: Identify SMD Crystal Oscillators

An SMD crystal is a quartz piece with two terminals polished and sprayed with a silver film. When an IC is packaged with the quartz piece to form the oscillation circuit, it is an SMD oscillator. Y stands for crystal oscillators.

SMD crystal oscillators provide basic clock signals for the system.

On a component, if you see a combination of numbers and HZ or Z, that is a crystal oscillator.

You can see crystal oscillators in the below image. DIP crystal oscillators have two long pins, and the rest are SMD crystal oscillators. SMD crystal oscillators have two or four pins.

Part 7: Identify SMD Connectors

SMD connectors provide temporary or permanent electrical connections for circuits, and they are usually used in pairs.

Part 8: Identify SMD Button Switches

SMD button switches are surface mount switches that use a button to connect or separate the two contacts to realize the circuit switch.

SMD Components Sourcing and PCB Assembly One-Stop Solutions

 

PCBONLINE provides one-stop-shop solutions for SMD electronic components sourcing, PCB Assembly, and advanced PCB manufacturing. PCBONLINE is an ISO-certified electronics manufacturing services provider founded in 1999.

Relying on our EMS factory for manufacturing, PCBONLINE takes part in joint components procurement with other large EMS and enjoys bargaining power.

From PCBONLINE, you can enjoy these benefits in SMD components sourcing:

High-quality SMD components directly sourced from original factories.

SMD components at possibly the lowest prices because we pick up the best prices from hundreds of distribution points around the globe.

Quality refund guarantee. You can buy one tray of SMD components to try before bulky purchase.

Strict quality control of SMD components and free IC counterfeit detection.

You can let PCBONLINE mount SMD components on printed circuit boards, complete all PCBA tests, and do the end-product assembly.

Please feel free to send your BOM to PCBONLINE by email at info@pcbonline.com to get a quote for your electronic components.

Conclusion

This article gives a brief introduction to common SMD components, displays their images, and provides tips to identify components from their appearances. If you have any concerns or needs for SMD components or PCBs, welcome to contact PCBONLINE by email or from the online chat window on the right of our website pages.

 

List of integrated circuit packaging types

 

Integrated circuits are put into protective packages to allow easy handling and assembly onto printed circuit boards and to protect the devices from damage. A very large number of different types of package exist. Some package types have standardized dimensions and tolerances, and are registered with trade industry associations such as JEDEC and Pro Electron. Other types are proprietary designations that may be made by only one or two manufacturers. Integrated circuit packaging is the last assembly process before testing and shipping devices to customers.

Occasionally specially-processed integrated circuit dies are prepared for direct connections to a substrate without an intermediate header or carrier. In flip chip systems the IC is connected by solder bumps to a substrate. In beam-lead technology, the metallized pads that would be used for wire bonding connections in a conventional chip are thickened and extended to allow external connections to the circuit. Assemblies using "bare" chips have additional packaging or filling with epoxy to protect the devices from moisture.

 

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