What is the difference between SMT and SMD?

Overview: A lot of technical terms are usually used in the electronics manufacturing industry, and it is not very familiar to newbies in this industry or just electronics enthusiasts. This article will explain two professional terms commonly used in PCBA – SMT and SMD.

What is SMT

SMT, short for Surface Mount Technology, is a new method of arranging components on a PCB, which can be implemented by almost 90 percent of PCBA companies. In the 70’s, THT technology was commonly used, that is, components were arranged through through holes, with component leads placed in drilled holes on a bare PCB. Surface Mount Technology, it is soldering the components directly on the boards. Since there is no need to pass leads through the PCB, the process is faster and more cost-efficient.  That is to say, SMT is now the most popular technology used in PCBA assembly. The advantage with PCB SMT assembly is that it saves space, which means more components can be soldered on a smaller board. 

SMT assembly equipment

SMT assembly process

  • Printing: The SMT instrument aligns the prepared PCB template with the PCB that needs to be patched. While the squeegee is smearing the stencil, the solder paste drips onto the corresponding solder joints along the holes of the stencil.
  • NMounting: The SMD components are precisely placed in place by a pick-and-place machine, where the solder paste acts as a temporary adhesive.
  • Reflow Soldering: FS Technology uses 10-drive advanced reflow equipment to melt the solder paste that connects the board and components.
  • Testing and Inspection: PCBA testing is performed by manual inspection and AOI inspection in the SMT placement link to ensure the quality of the circuit board, such as component alignment and checking for solder bridges.

Features and advantages of SMT assembly

  • The SMD body is on the same side as the solder joints.
  • SMD has no leads or only short leads.
  • The hero of the reduction of electronic equipment.
  • Through new assembly equipment, fully automated installation and mass production are realized.
  • It is very helpful to reduce parasitic capacitance and parasitic inductance.
 

Summary, SMT assembly is an process that refer to apply the right amount of solder paste to mount each component. SMT also lends itself to automation as machines can be programmed to mount components on the PCB. This ensures accuracy, and it also speed up the production process and delivery it much quicker. Of course, this article is mainly written to compare the difference between SMT and SMD, and the topic of what is SMT is not discussed in depth. If you want a more detailed look at this assembly technique, you can find this article on the FS Technology blog.

What is SMD

SMD, short for Surface Mount Device, is an electronic component that is soldered on a printed circuit board and is designed to be mounted directly on the PCB. SMD PCBA components have the characteristics of miniaturization, no leads, and are suitable for SMT technology. However, with the needs of PCB assembly technology, manual soldering has gradually failed to achieve the ideal state, so the SMD placement machine was born. Surface mount devices allow more components to be soldered to the board and improve its functionality. With no holes to be drilled, they also make the process quicker and cost-effective. What the important is to choose the right SMD, and then install them correctly on the board. SMD can be automatically mounted onto the electronic board as opposed to manually soldering them.

Different Types of SMD

It took only 20 years for surface mount components to become popular, and they have dominated the field of components today. Tracing the development history of components, the components of electronic equipment used by human beings range from passive components to active components and integrated circuits, and are finally 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, MCM). The SMD components are classified below.

Резистор

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

picture of resistor

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 SMT chip technology to mount SMD ceramic capacitors.

Ceramic Capacitor

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).

nine different transistors

Integrated Circuit

Small-outline SMD active integrated circuits that are common in life generally use shrink packaging. Small outline integrated circuits have lead centers of about 0.050 inches and are primarily used to accommodate larger integrated circuits than SOT packages.

PWB Integrated Circuit

The reason why FS Technology has a comprehensive understanding of SMD components and SMT technology is that we provide a one-stop Сборка печатной платы service, which starts from Закупка компонентов печатной платы and continues until customers receive satisfactory products.

SMT VS SMD

After reading the above content, I believe that you have a comprehensive understanding of the difference between SMT and SMD. Let us distinguish the two in one sentence: PCBA factory installs SMD components on PCB boards through SMT technology and equipment.

Even two things that are completely different in nature and concept have an overlap in that they depend on each other. It is the proper selection and arrangement of SMD that is the primary process behind SMT. Automated SMT machines can mount several SMD on the board in a short period of time. SMD determine the capacity of the board, while SMT involves the installation of these components on the board. SMD and SMT became stronger because of each other’s advantages, while DIP and THT were gradually abandoned.

Summary: The advancement of science and technology has brought us opportunities and challenges, and with these advancements, the living habits of human beings are also changing. Making the right choice in this fast-changing era will be as smooth as SMT technology, and if the wrong choice is made, it will become replaced like THT technology. Choose Технология FS to serve your PCBA project and you will get more profit margins, higher quality products and more pleasant cooperation. The above is our introduction to the difference between SMT and SMD. If you want to know more about PCB, you can click on Блог о PCBA.

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