What does SMT stand for in electronics

Overview: The process of making technology smaller is moving at a crazy fast pace that never stops amazing us. The only thing that makes gradual shrinking conceivable is using a suitable automatic SMT assembly process. Instead of using standard components connected by wires, this method lets boards be covered with components that can be mounted on the surface. 

The word SMT may not be unfamiliar to lovers of electronic products, but they do not know what it is. In fact, we have long been unable to leave the use of this patch technology, and you can find their traces in various electronic devices such as mobile phones, laptops, refrigerators, and TVs. In this article, FS Technology will introduce you to the most important part of the PCB assembly process – PCBA SMT assembly.

What does SMT stand for in manufacturing

The full name of SMT is surface mount technology, which is used together with THT in the assembly process of circuit boards. This high-precision electronic assembly technique is used to attach or solder surface mount components on PCB pads. Its workflow is roughly as follows:

Firstly , print solder paste coated on the PCB pads , and then place the surface mount component (SMD) accurately on the solder paste coated pad, by heating the printed circuit board until the solder paste melts, after cooling will realize the connection between the components and printed circuit.

Introduction to terms related to SMT technology

THT: Its full name is through-hole technology. Various components are placed on the surface of the PCBA board, some are patches, and some are plug-ins.

SMD: A surface mount component, the difference between SMT and SMD can be found in FS Technology’s PCBA blog.

DIP: The full name is dual in-line package. Its relationship to THT is similar to that of SMT and SMD.

The concept of SMT Process

FS Technology mainly uses two processes in SMT PCB assembly: reflow soldering and wave soldering. The following figure shows the reflow soldering process.

So in the SMT production line, what is the role of reflow soldering and wave soldering, and what is the difference between them? Let FS Technology explain the above questions for you:

Regarding Reflow: the soldering paste precoated on the pad is melted by heating to realize the electrical interconnection between the pins or solder ends of the electronic components premounted on the pad and the PCB pad, so as to achieve the purpose of welding the electronic components on the PCB board. Reflow welding is generally divided into preheating zone, heating zone and cooling zone.

Reflow soldering process: Printing solder paste > mount components > Reflow soldering > cleaning

Reharding Wave soldering: the pump is used to spray the melted solder into a solder wave peak, and then the pins of the electronic components to be welded pass through the solder wave peak to realize the electrical interconnection of electronic components and PCB board. A wave soldering is divided into spray, preheating, tin furnace, cooling four parts.

Wave soldering process: plug-in > Flux coating > preheat > wave soldering > edge cutting > inspection.

The main differences between wave soldering and reflow soldering are as follows:

  • Reflow soldering, there already coated with solder paste on the PCB before into the machine , then welding by melting the solder paste . In wave soldering, there is no solder paste coated on the pcb before into machine, and it welds by wave machine creating solder paste to paint on pcb pads which need solder .
  • Wave soldering is molten solder to form solder wave for welding components; Reflow soldering is high temperature hot air form circumfluence molten solder to weld components.
  • Reflow is suitable for patch electronic components, wave soldering is suitable for pin electronic components.
 
Wave soldering and reflow are two important processes in SMT PCB Assembly machining.

History of Surface Mount Technology

To get a clear idea of what a technology stands for, you have to understand its history. Throughout the development of SMT technology, FS Technology divides it into four stages, the specific time and characteristics are as follows:

Phase 1: 1960 to 1975

This stage was a historic moment when circuit boards came out and changed the electronics manufacturing industry. Humans have changed from using primitive breadboards to PCBA boards, and have completely entered the era of miniaturization. The representative works of this stage are calculators and quartz watches.

The second stage: 1976 to 1980

A stage in which SMT technology becomes mainstream. Before this period, THT technology was mainly used for circuit board assembly, but with the popularity of small-volume electronic products all over the world, SMT gradually began to replace THT. Using this PCB assembly technique allows electronics to have a smaller footprint and be more functional. The main representative works are camcorders, video recorders and digital cameras.

Phase III: 1980 to 1995

PCBA boards have become an indispensable product in the electronics manufacturing industry, and enterprises have begun to vigorously develop production equipment to improve product cost performance. VLSI was the best electronic product produced during this period.

Current stage: 1995-present

Micro-assembly, high-density assembly, and three-dimensional assembly technology are developing rapidly. According to reports, the global electronic products using through-hole assembly technology are declining at an annual rate of 11%, while the electronic products using SMT patches are increasing at a rate of 8%.

Technology development has always been the mainstream of the world. FS Technology has always advocated advancing with the times, committed to creating automated, intelligent and flexible production lines, and used the latest SMT assembly technology to serve customers. As a person in the electronics manufacturing industry, it is very important to understand the development history of PCB, which can help your business find the right direction of change.

Why SMT is favored by the electronics manufacturing industry

Advantages of using SMT for electronic products

As mentioned above, SMT has gradually replaced THT, so what advantages does this technology have, and why do turnkey PCB assembly manufacturers prefer it? FS Technology will take you through the advantages of this technology.

High assembly density

Compared with traditional DIP technology, SMD components can make the assembly area and mass smaller. The PCBA product assembled using SMT is 40% of the volume of the DIP and only 35% of the mass. DIP components are mounted on a 2.54mm grid, while SMD can perform better. In order to meet customers’ requirements for smaller electronic products, FS Technology’s SMT technology is becoming more and more mature. Our surface mount assembly component grid has grown from 1.27mm to the current 0.63mm grid, and some special components can even be mounted on a 0.5mm grid.

More reliable technology

Because SMD components are small and light, their shock resistance and reliability are higher. When producing SMT assembled products, FS Technology uses 7 fully automatic production lines. Our production line has strict quality control standards, and the general bad solder joint rate is less than 10 parts per million. The wave soldering technology of through-hole components is an order of magnitude lower, and the average MTBF of electronic products assembled with SMT is 250,000 hours, which is the main reason why 90% of electronic products use the SMT process.

Good high frequency characteristics

SMD components are different from plug-ins. Generally, no leads or short leads are used for direct patch welding, which can greatly reduce the impact on circuit inductance, large-capacity capacitance and resistance. For a project, the MHz of the PCBA board is very important, and the frequency of the circuit can be increased by using the patch method. By comparing SMD and THT, FS Technology found that the maximum frequency of the circuit designed with surface mount technology can reach 3GHz, while the maximum frequency of through-hole technology is only 500MHz. Due to its high frequency characteristics, SMD can shorten the transmission time of your circuit board, which is very important for electronic products such as computers that require the most transmission time.

Reduce the cost of assembly projects

  • Reduce the number of holes drilled on the PCBA board
  • Reduced cost and time to debug circuit boards
  • Reduced packaging, shipping and storage costs
  • The price of chip resistors is comparable to that of through-hole resistors

Easy to automate production

Surface mount is a technology that makes it easier to automate mass production. Taking FS Technology as an example, we have 7 SMT lines, all of which use automated SMT equipment to pick up and mount SMD components with vacuum nozzles. Due to the smaller size of these vacuum nozzles, the assembly equipment can be assembled with higher precision. In fact, most PCBA companies are now produced by automated placement. If a turnkey PCB assembly company wants to use THT technology for large-scale automated production, it needs to expand the area of the PCB bare board to at least 140%.

If you need a comprehensive understanding of the significance of surface mount technology, then you need to know not only the advantages of SMT, but also its disadvantages.

Disadvantages of electronic SMT technology

  • The nominal value of SMD electronic components is not easy to see
  • Difficulty repairing PCBAs assembled using SMT
  • Difficulty replacing components on PCBA
  • Poor Coefficient of Expansion Consistency of SMD Components
  • Component leakage, component misalignment and component damage are prone to occur during the assembly process
 

In order to deal with these shortcomings, FS Technology recommends solutions for you.

  • Maintain good wettability of SMD components
  • The solder maintains continuity on the surface of the solder joint. The closer to the edge of the solder joint, the thinner the solder layer will be.
  • The edge line of the pad is small, so the contact angle between the SMT device and the pad should be less than 30 degrees
  • No contamination such as solder mask is allowed on the surface of the metal to be welded
  • Solder joint solder layer should be moderate, avoid too much or too little
  • The solder spot position must be accurate, the end/pin of the PCB component should be in the center of the pad, width and length direction should not exceed the phenomenon.
  • The solder joint plane should be continuous and smooth, and the solder joint formed by reflow welding should have a bright appearance.

How to Choose Manufacturers for PCBA SMT Assembly?

The above has covered almost everything that electronics enthusiasts may be interested in, but if you are a PCBA engineer and need to find an SMT manufacturer to serve you, then the following content is what you have to see!

An engineer put much effort into the printed circuit board project before the assembly. Hence, it’s crucial to choose a better SMT vendor for the assembly. Selecting a company to work with can be challenging because there are so many options, and this choice is so important. If you need to choose a PCB assembly firm, how can you determine the ideal fit for your project? To make it easy for you, we are listing the services that should be available to the customers by the company:

  • The manufacturing facility with cutting-edge machinery and tools, making it capable of meeting the difficulties posed by constructing even the most complicated PCBs.
  • Engineers with years of experience who are ready to assist you throughout the whole procedure and ensure that everything runs efficiently.
  • Materials of the highest quality – The firm only utilizes SMT SMD components of the highest quality to ensure that the boards’ quality can match and surpass the user’s expectations.
  • Delivery within the specified time frame. It indicates that the company can feasibly fulfill mass production orders in the shortest amount of time. The completion of the manufacturing within the allotted time is something the firm assures.
  • Prices are reasonable; the clientele’s satisfaction is the organization’s primary focus. Because of this, you may anticipate reasonable costs suitable for any financial plan.

No matter what you want to use the printed circuit board for, it would be best to look for one that is reliable and has a high-performance level during its lifetime. If you have a reliable SMT electronics manufacturer on your team, you should be able to accomplish this goal.

Even though it has more electronic components, assembling a printed circuit board is just as important as designing and making it. As you can see, SMT assembly plays a significant role in almost all contemporary forms of electronic product design. If your PCB design still uses the through-hole method, SMT assembly could help your product move forward. Make sure you work with a trustworthy and knowledgeable assembly partner to avoid any problems that might arise with SMT.

The above is FS Technology’s entire explanation of “What does SMT represent in electronic products”, FS Technology will continue to update more SMT knowledge in the blog, so stay tuned.

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