What is the Difference Between SMT and SMD For An Electronic Manufacturer?

An SMD, or surface-mounted device, is an electronic component that you would find on a board. An SMT, or surface mount technology, is the method of placing components (like an SMD) on the board.

 

SMT and SMD.

 

These two little acronyms get mixed up a lot in the electronics manufacturing service world. For electronic manufacturers on paper, they only vary by a single letter, but in practice, there’s a lot more separating SMTs and SMDs.

 

Chiefly, one is a process and the other is a device.

 

An SMD, or surface-mounted device, is an electronic component that you would find on a board.

 

An SMT, or surface mount technology, is the method of placing components (like an SMD) on the board. In electronic manufacturing services, the SMT process often works with SMDs, perhaps adding to the confusion. And while it is important to know the difference between the two, the value of either is amplified when they are used in concert.

 

What are Surface-mounted Devices, or SMDs?

 

Surface-mounted devices (SMDs) are small components that electronic manufacturers attach to circuit boards in electronics manufacturing. These components were designed to be more compact than their predecessors to meet the market's growing demand for smaller, faster, and cheaper electronics. The older through-hole technology could not keep pace with the increasingly compact and complex technological advancements seen from the latter part of the 20th century into the 21st.

 

In contrast to older, bulkier components that required wire leads to go through the board, SMDs use pins that are soldered directly onto the board's pads. This design not only reduces the need for drilling holes but also maximizes the board's available space, allowing both sides to be utilized more efficiently.

 

SMDs were developed for use with the highly efficient and precise surface mount technology (SMT).

 

 

What is Surface Mount Technology, or SMT?

 

Surface mount technology (SMT) is the process used to mount and solder surface-mounted components onto a circuit board. This process begins with the application of solder paste in precise amounts, ensuring that a stencil can be perfectly aligned with the board's surface. Next, a pick-and-place machine mounts the components onto the board through the stencil. Following this, the boards pass through infrared ovens that melt the solder paste, forming secure solder joints. To ensure precision and quality, an Automatic Optical Inspection (AOI) machine checks the alignment and quality of the soldered components.

 

SMT gained popularity in the 1980s and has since become a cornerstone of electronics manufacturing services. Over time, advancements in this technology have reduced costs and improved performance. A significant advantage for manufacturers using SMT is the reduction in the number of devices needed, lower error rates, enhanced performance, and increased functionality. These factors contribute to significant reductions in manufacturing costs due to fewer errors, a streamlined process, and the use of smaller components.

 

The precision and efficiency of SMT have attracted industries where quality and function are paramount. It is widely used in sectors such as aviation, automotive, medicine, communications, and consumer electronics. While less efficient and more error-prone processes might have sufficed in the past, SMT has facilitated significant growth and expansion in these fields.

 

Where SMT and SMD Combine

 

In the early days of surface-mounted devices (SMDs), the placement and soldering of smaller and more intricate components were often done manually by electronic manufacturers. Machines could handle some parts, but their capabilities were limited by the size and type of the components. Today, the process of manufacturing boards using surface mount technology (SMT) has evolved significantly, becoming much faster and far more accurate.

 

In the past, small bits of silver or lead were placed on the board to attach components. While these materials are still in use, they are now part of a solder paste, which is a mixture of flux and tiny solder particles. Modern SMT machines can attach thousands of SMDs per hour, a stark contrast to the few hundred components that could be placed by hand. As a result, nearly every through-hole process now has an SMT equivalent.

 

The rise in popularity of SMDs is closely linked to the efficiency gains provided by SMT. The smaller size of SMDs allowed for better utilization of both time and space in manufacturing. SMDs enabled more functionality within a smaller, more precise device. At the same time, SMT revolutionized the assembly process, achieving faster and more accurate results than any previous method. The combined cost savings and enhanced efficiency have led to an increasing number of electronics manufacturing services adopting SMDs in conjunction with SMT.

 

Conclusion

 

Understanding the difference between SMT and SMD is vital for electronic manufacturers aiming to produce high-quality, reliable, and efficient products. SMT refers to the technology and process used to mount components onto PCBs, while SMDs are the components themselves. Together, they form the backbone of modern electronics manufacturing, enabling the creation of compact, high-performance devices.

 

If you have further questions or need assistance with your electronics manufacturing needs, please contact us. As a leading supplier in the industry, we are here to provide the expertise and solutions you need.

 

FAQs

 

1. What is the main advantage of SMT over through-hole technology?

SMT offers higher component density, better performance at high frequencies, and greater compatibility with automation, making it ideal for modern, compact electronic devices.

 

2. Can SMDs be used in through-hole assemblies?

Generally, SMDs are not designed for through-hole assemblies. However, adapters and special techniques can sometimes be used to integrate them into through-hole PCBs.

 

3. What are the common issues encountered in SMT assembly?

Common issues include soldering defects such as bridging, tombstoning, and cold joints, as well as placement inaccuracies that can affect the functionality and reliability of the PCB.

 

4. How does the choice of SMD affect the overall PCB design?

The choice of SMDs impacts the PCB layout, pad design, and thermal management. It also influences the selection of solder paste and reflow profiles.

 

5. What factors should be considered when selecting an SMD for a project?

Consider the component size, package type, electrical characteristics, availability, and cost, as well as how well it fits with the overall design and manufacturing process.