Before you decide
SMD, SMT, and package names describe different parts of the assembly decision. Separate the component package, PCB land pattern, reflow process, inspection method, and serviceability before deciding what your production line can support.
Table of Contents
What is SMD?
SMD stands for Surface Mount Device, which refers to a component used in Surface-Mount Technology (SMT). SMT is a commonly used assembly method in modern electronics. The biggest advantage of this technology is that it allows for the rapid assembly of many electronic components onto a PCB (Printed Circuit Board). As electronic components become smaller, products that use these components, like smartphones, also become lighter, thinner, and more compact.
| Term | Full name | What it is |
|---|---|---|
| SMT | Surface Mount Technology | The mass-production method for mounting parts onto a PCB surface |
| SME | Surface Mount Equipment | The machines that do the surface mounting |
| SMP | Surface Mount Package | The package a part needs so SME can place it on the PCB |
| SMC | Surface Mount Components | General term for components mounted onto a PCB |
| SMD | Surface Mount Device | A single-element surface-mount component (simplest SMC) |
| SMA | Surface Mount Assembly | A component of one or more elements packaged via SMP |
In the industry, you might hear terms like “This IC uses a QFN package.” QFN is one type of packaging for SMD components, and IC stands for integrated circuits, a type of electronic component. There are other terms related to SMT as well, such as SMP (Surface Mount Package), SMA (Surface Mount Assembly), SMC (Surface-Mount Components), and SME (Surface Mount Equipment). We will explain these terms individually later in this article.
To clarify what’s SMD / SMA / SMT / SMC / SMP / SME
| SMP Term | Expended Form |
| SMD | Surface-Mount Device |
| SMT | Surface-Mount Technology |
| SMA | Surface-Mount Assembly |
| SMC | Surface-Mount Components |
| SMP | Surface-Mount Packages |
| SME | Surface-Mount Equipment |
SMT ( Surface Mount Technology )
The SMT stand for the ” Surface Mount Technology “. This technology is the mostly used mass production technology for modern electronic product to automatic assemble large amount of electronic component to PCB ( Printed Circuit Board ) .
SME ( Surface Mount Equipment )
The equipment for Surface Mount Technology is called Surface Mount Equipment. This is the equipment to do the Surface Mount Components to PCB. The major equipment includes:
SMP ( Surface Mount Package )
The device need a special package for Surface Mount Equipment to assembly SMC ( Surface Mount Components ) to PCB ( Printed Circuit Board ) is call SMP ( Surface Mount Package ).
▲ SMP－QFN(quad flat non-leaded package) 28 pin(REF:Wikipedia)
SMC ( Surface Mount Components )
Surface Mount Components (SMC) and Surface Mount Package (SMP) are two terms that seem quite similar in meaning. However, Surface Mount Package (SMP) refers to the type of packaging used for electronic components, focusing on what kind of SMD packaging is used. On the other hand, Surface Mount Components (SMC) refers to the components that, after being packaged, can be assembled onto a PCB ( Printed Circuit Board ) using Surface-Mount Technology (SMT) and Surface Mount Equipment (SME).
Surface Mount Components (SMC) can be divided into two categories: Surface Mount Package (SMP) and Surface Mount Assembly (SMA). For more details, you can refer to the Venn diagram explaining the relationships between SMD, SMA, SMT, SMC, SMP, and SME.
SMA ( Surface Mount Assembly )
If an electronic component is made up of one or more electronic elements and is packaged using Surface Mount Package (SMP), then this component can be called a Surface Mount Assembly (SMA). Common examples of these assemblies include seven-segment displays, dot matrix displays, alphanumeric displays, Bluetooth modules, and WiFi modules.
SMD (Surface Mount Device)
Each electronic component can be packaged as an SMC (Surface Mount Component), different name were call depend on it’s complexity. Generally, only one electronic component was package for Surface Mount Technology is called SMD ( Surface Mount Device ) , for example, 0402 package LED(OPS-L0510 series), 0603 package LED(OPS-L0816 series).
SMD Size chart
This article use USB Type C connector and NTD 10 coin to compare the common SMD package size in picture comparison. Not only We compare the most used two terminal device. We also compare SMD IC Package and SMA Module package for reader. Let Reader have some basic SMD size with daily item.
NTD 10 coin VS 2020 SMD Package OPS-L2020F7 VS 0808 SMD Package OPS-L0808F5 VS 0404 SMD package OPS-L0404F6
0603 SMP SMD capacitor VS Type-C USB connector
1206 SMP SMD capacitor VS Type-C USB connector
SSOP24 SMP SMD IC VS Type-C USB connector
QFN28 SMP SMD IC VS Type-C USB connector
QFN28 SMP SMD IC (PT6950 From Princeton Technology Corp.) VS Type-C USB connector
0.2″ Digit height single digit 7-segment display SMA VS Type-C USB connector
0.2″ Digit height single digit 7-segment display(OPS-S2010) SMA VS Type-C USB connector
Venn diagram for SMD / SMA / SMT / SMC / SMP / SME
We try to use Venn diagram to show the relationship for this term. some of these term were misuse in many daily conversion and article. For example, call SMA as SMD or even SMC. Hope this diagram clarify these professional term.
Simple SMT Assembly process breakdown
A product use SMT ( Surface Mount Technology ) to assembly electronic component to PCB may have different name. Such as, SMT Line Stand for Surface Mount Technology Product Line. SMTA Line stand for Surface Mount Technology Assembly Line. Or even call SMA, Surface Mount Technology Assembly. You have to check SMA meaning from the paragraph. but all abbreviation mention above means a product line that use SMT ( Surface Mount Technology ) to assembly electronic component to PCB, Which have 3 main process:
- Solder paste printing process
- Use SME: Automatic solder paste screen printer
- Pick-and-place process
- Use SME: Pick-and-place machine / Mounter machine
- Reflow soldering process
- Use SME: Re-flow oven
Below is the simple diagram for SMT process, for example, we are going to SMT a 0603 packaged resistor. Firstly, we need to clean the PCB, and then use the solder paste screen printer to print the solder on the solder pad. At this moment, the solder is in cream type. Then, use the pick & place machine to assemble the resistors onto the solder paste. At this stage the paste is still in cream form and only holds the resistor in place temporarily. The board then passes through the reflow oven: the solder paste melts, and the surface tension of the molten solder pulls the component toward the centre of the pad. This is the self-alignment effect of the surface-mount process — the part is not held by its own weight, it is positioned by surface tension and fixed when the solder solidifies. Once the solder has solidified it forms both the mechanical and the electrical joint, so the resistor stays attached to the PCB unless it is subjected to excessive force or heat. Then, the SMT process is completed.
Conclusion
This article is just to introduce the related technology for SMD & SMT, and do hope it can help readers to verify the difference in between simply. Opto Plus LED Corp. is the professional manufacture for SMD package 7-segment display, SMD package 16-segment display and SMD package dot matrix display.Reader can go to product and know more about SMD package datasheet. If you have any inquiry or questions related to LED display, please send your questions via sales. last update ：2022-06-23
FAQ
In simple terms, SMT (Surface-Mount Technology) is a manufacturing process, while SMD (Surface-Mount Device), SMC (Surface-Mount Component), and SMA (Surface-Mount Assembly) refer to the components or finished products used in this process. Think of SMT as the assembly method and SMD/SMC/SMA as the building blocks.
The small size of modern electronics is largely due to SMT and SMD components. Unlike traditional through-hole components with long pins that require holes in the circuit board, SMDs have no or short pins, allowing them to be mounted directly on the PCB surface, significantly reducing space.
The SMT process includes three core steps:
Solder Paste Printing: Applying solder paste to precise locations on the PCB using a stencil.
Pick and Place: Using automated robotic arms to place SMD components accurately on the solder paste.
Reflow Soldering: Heating the PCB in a reflow oven to melt and solidify the solder, securing components to the board.
Yes, SMD (Surface-Mount Devices) can be hand-soldered, but it requires specialized tools and skills. Common tools include a hot air gun, soldering iron with a fine tip, a microscope or magnifying glass, and steady hands. Due to the tiny size of SMDs (e.g., 0402 resistors or micro ICs), precision is critical. Hand soldering is suitable for prototyping or small-scale repairs but is less efficient and reliable than automated reflow soldering.
SMT (Surface-Mount Technology) enhances reliability through automated production and precise soldering. It uses solder paste printing and reflow soldering to ensure strong connections between SMD components and PCBs, reducing contact issues. Automation minimizes human errors, and the compact design of SMDs improves heat dissipation and signal integrity, especially in high-frequency circuits like smartphones and automotive electronics. Quality checks like AOI (Automated Optical Inspection) further ensure consistency.
Despite its efficiency, the SMT process faces challenges such as:
Soldering Defects: Issues like cold joints (weak soldering) or short circuits (pins accidentally connected).
Component Misalignment: Uneven heating or other factors causing components to shift or lift during reflow.
Solder Balls: Small, unwanted solder beads forming during soldering, potentially causing shorts.
These issues can be mitigated by precise temperature control, high-quality solder paste, and well-maintained equipment.
SMT is viable for small-batch production but can be costly due to the need for specialized equipment like pick-and-place machines and reflow ovens. For small batches, combining hand soldering or semi-automated SMT equipment may be more cost-effective. Compared to through-hole technology, SMT still offers higher precision and miniaturization benefits.
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