В чем разница между SMT и SMD?

The electronics manufacturing industry is a highly professional industry. Those who are familiar with it, prefer to use basic abbreviations to express their needs, such as PCB (printed circuit board), PCBA (PCB assembly), Through Hole Technology (THT), etc. This is not friendly to novices or electronics enthusiasts. In this article, FS Technology will explain two commonly used terms in the PCBA industry, SMT and SMD, from the concept, use, and combination of these three aspects.

What is SMT?

Basic Concept Explanation

The full name of SMT is surface mount technology, a new method of arranging components on PCB. This technology is widely used in the PCBA industry, and almost all companies that provide Услуги по сборке печатных плат can provide SMT assembly services. In the early 1970s, electronic manufacturers used through-hole assembly to realize component mounting and soldering work, that is, the leads of components were placed in drilled holes on bare PCBs, and permanent component through-hole arrangements were achieved through soldering guns. However, with the development of technology, people gradually found that through-hole PCB assembly is not the best solution, and SMT assembly may serve as a replacement.

Unlike plug-ins, SMT technology uses leadless assembly to solder components directly to the bare PCB, which is a faster and more cost-effective assembly method. For some consumer electronic devices (mobile phones, computers, etc.), their update frequency is less than a year, which means that electronics manufacturers urgently need automated PCB assembly to achieve large-scale production, and SMT technology simply meets this requirement.

Процесс SMT-сборки

Printing: The SMT instrument aligns the prepared stencil with the PCB board requiring patching. As the squeegee spreads the stencil, the solder paste is deposited onto the corresponding solder joints through the holes in the stencil.
Mounting: The SMD components are accurately positioned by a pick-and-place machine, utilizing the solder paste as a temporary adhesive.
Reflow Soldering: At this stage, the solder paste remains in a semi-liquid state and needs to be melted and solidified to form a robust solder joint. Пайка оплавлением is commonly employed in the SMT process for handling delicate-pin components like BGA и QFN, providing precise temperature control and uniform heat distribution, resulting in highly reliable solder connections.
Testing and Inspection: Once the entire Технологический процесс SMT is completed, the manufacturer conducts a range of inspection methods to ensure welding quality, including component alignment, solder bridges, circuit short circuits, etc. These inspections involve manual examination, Инспекция AOI, and other techniques.

Features of SMT

Reduce parasitic capacitance and parasitic inductance;
Reduce the demand for components in PCBA projects;
Automated new equipment enables fast and reliable large-scale production;
Facilitating the development of tiny electronics or implantable devices.

In summary, SMT refers to an assembly technique that involves applying the right amount of solder paste to mount each component. It also lends itself to automation as machines can be programmed to mount components on the PCB. This ensures accuracy, and it also speeds up the production process and delivery quicker. So far, our introduction to SMT is over. If you want to learn more about SMT, please read “What does SMT stand for in electronics".

What is SMD?

Basic Concept Explanation

Firstly, it is essential to comprehend the operational principle of a PCB, which comprises two main elements: the bare board and the components. The bare board serves as a platform for mounting the components and establishing electrical pathways. When current is applied, it traverses the circuitry and reaches the components, enabling their functionality. Therefore, it is the components themselves that actively contribute to the operational capabilities of the PCBA board. SMD represents a specific type of component.

SMD, short for Surface Mount Device, is an electronic component that is soldered to a printed circuit board and is designed to be mounted directly on the PCB. Currently, we have a variety of installation methods for PCB components. According to different installation methods, PCB components can be divided into various types, including DIP-компоненты and SMD components, that is, plug-in components and patch components. Affected by the trend of miniaturization, more SMDs are being used in the production of PCBA nowadays.

Types of SMD Component

It took only 20 years for surface mount components to become popular, and they have dominated the field of components today. Tracing the developmental history of components, the components of electronic equipment used by consumers ranged from passive components to active components and integrated circuits, and finally, is now ruled by SMD. Surface mount equipment can be roughly divided into two categories: transistors and integrated circuits (SOP, SOJ, PLCC, LCCC, QFP, BGA, CSP, FC, and MCM). Several common SMD components are classified below.

Резистор

This type of SMD resistor is usually surface mounted in SMT technology and needs special attention when it is mounted. Taking SMDs on a ceramic PCB as an example, when the керамическая печатная плата is patched, it is necessary to apply a glass passivation film on the surface in order to prevent the metal material from overflowing by welding.

Ceramic Capacitor

Applications such as engine engines, military communication equipment and aerospace equipment are very dependent on high frequency circuits, so we need to use SMD SMT chip technology to mount SMD ceramic capacitors.

Transistor (SOT)

The three- and four-lead SOT devices are considered one of the pioneers of surface mount active devices. Three-lead SOTs are identified as SOT 23 (EIA TO 236) and SOT 89 (EIA TO 243). The four-lead device is called SOT 143 (EIA TO 253).

Integrated Circuit

An integrated circuit, or IC chip, is a collection of components such as resistors, capacitors, and transistors. Engineers integrate a “small PCB” with specific functions through IC programming and semiconductor processing. Small-outline SMD active integrated circuits that are common in life generally use shrink packaging. Small outline ICs have lead centers of about 0.050 inches and are primarily used to accommodate larger ICs than SOT packages.

Features of Surface Mount Device

The SMD body is on the same side as the solder joints;
SMD has no leads or only short leads;
Smaller size but better performance;
Уменьшите риск ошибок при изготовлении PCBA, сократив количество сквозных отверстий.

В целом, SMD относится к определенному типу компонентов, которые монтируются на плату PCBA, используя технологию поверхностного монтажа для обеспечения своей функциональности. SMD-компоненты соответствуют тенденции миниатюризации в отрасли и гарантируют качество сборки, благодаря чему они широко используются в производстве PCBA. Для более глубокого понимания SMD-компонентов, пожалуйста, обратитесь к статье "Что такое SMD-компоненты?"

SMD в сравнении с SMT

Разница

Концептуальное различие: SMT относится к определенному типу технологии сборки и обычно ассоциируется с такими терминами, как сборка, пайка и процесс. С другой стороны, SMD представляет собой тип электронного компонента и обычно используется в сочетании с такими словами, как компонент, деталь и т.д.
Разница в использовании: Процесс SMT специально разработан для SMD-компонентов и не рассчитан на установку компонентов со сквозными отверстиями. В отличие от этого, SMD-компоненты могут быть установлены на печатные платы с помощью различных процессов пайки, в зависимости от их свойств и характеристик. Эти процессы включают ручную пайку, плавление горячим воздухом, нагрев на горячей плите, пайку волной и др.
Разница в целях: Основной целью процесса SMT является достижение автоматизации и точного монтажа, что обеспечивает эффективное производство. И наоборот, использование SMD электронных компонентов направлено, прежде всего, на достижение миниатюризации и высокоплотной интеграции в электронных системах.

Комбинация

Хотя SMD и SMT представляют собой разные концепции, они дополняют друг друга в сфере производства электроники. Учитывая историю развития PCBA, упадок DIP-компонентов можно отчасти объяснить ограничениями ручной пайки, что привело к появлению машин для сборки и размещения компонентов. Если раньше ручная пайка использовалась для традиционной сборки SMD-компонентов, то с появлением машин для размещения компонентов этот метод стал неактуальным. В современную эпоху простота, эффективность и экономичность являются решающими факторами прогресса, и объединение SMT и SMD в точности отвечает этим требованиям.

Автоматизированный режим производства направлен на оптимизацию затрат на сборку печатных плат, и SMD предлагает в этом отношении экономически эффективное решение.
SMT-оборудование позволяет быстро устанавливать тысячи SMD-компонентов на плату в короткие сроки.
Компактные размеры SMD-компонентов позволяют увеличить емкость печатной платы, а технология SMT эффективно использует это преимущество.
В SMD-компонентах используется бессвинцовая пайка, Компании, производящие PCBA может использовать это для уменьшения количества отказов во время сборки и повышения общей надежности процесса SMT.

Печатная плата по сравнению с PCBA

Что такое печатная плата

Что такое PCBA

Из чего сделаны печатные платы?

В чем разница между SMT и SMD?

What is SMT?

Basic Concept Explanation

Процесс SMT-сборки

Features of SMT

What is SMD?

Basic Concept Explanation

Types of SMD Component

Features of Surface Mount Device

SMD в сравнении с SMT

Разница

Комбинация

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