Surface Mount Technology – SMT Explained

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The technique of directly attaching electronic components to the surface of a printed circuit board is referred to as SMT. As the leads are placed into the PCB using the through-hole approach, a problem will arise if the leads are not properly fitted, slowing down the production pace. All electrical items require more functionality in a smaller package. As a result, the circuit PCB got more compact. The leads that were utilized for connections were eliminated, and the components were directly soldered on the PCB’s routes, saving the cost of drilling holes on the board.

Because SMT components have smaller or no leads, they are frequently smaller than their through-hole counterparts. It may contain a variety of short pins or leads, flat contacts, a matrix of solder balls (BGAs), or terminations on the component’s body.


What Are the Benefits of SMT?

Surface mount technology has various advantages over through-hole (TH) technology, which was formerly used. The two key advantages of SMT are its smaller size and lighter weight.
Components can be aligned closer together, resulting in more compact and lightweight end products.

  • Simpler assembly automation and maintenance
  • Higher overall product quality
  • Improved electrical performance
  • Increased circuit density
  • Decreased production and handling expenses

SMT components utilize up less space than TH components of equal size. SMTs can also be mounted on both sides of a printed circuit board, unlike through-hole components.

What are the drawbacks of Surface Mount Technology?

Surface mount technology, on the other hand, has significant disadvantages.
The solder compound that joins components to the board has a number of drawbacks, including:

  • Broken connections caused by heat cycling
  • The diameters of ultra-fine solder joints may have voiding, resulting in joint failure.

Other drawbacks include ambiguous ID codes, incompatibility with plug-in breadboards, and possible incompatibility with sockets due to a lack of space on SMT components for identification marks.

Surface mount boards may also require additional support to avoid strain or flexing. Through-hole components, by definition, are more flexible than those soldered directly to the board surface. Solder can crack if it is subjected to too much stress or distortion. By putting components at a right angle to the longest board dimension, a good design can reduce this (the most likely to flex.)

The Difference Between SMT and SMD

Surface Mount Technology (SMT) is the method of mounting electrical components directly to the surface of a printed circuit board, as we’ve seen. So, what exactly is SMD?
A Surface Mounted Device (SMD) is a component that is meant to mount directly to the board’s surface utilizing surface mount technology (SMT). SMD (surface mount device) refers to an electronic component that is mounted on a PCB. SMT (surface mount transistor) refers to an electronic component that is mounted on a circuit board. SMT (surface mount technology), on the other hand, refers to the method of placing electronic components on a printed circuit board.

SMD (surface mount device) refers to an electronic component that is mounted on a PCB. SMT (surface mount transistor) refers to an electronic component that is mounted on a circuit board.

SMT (surface mount technology), on the other hand, refers to the method of placing electronic components on a printed circuit board.

What Is Surface Mount Technology and How Does It Work?

SMT is a semi-automated method of assembly. Solder is used to join components to copper pads, or traces, on top of a circuit panel.

Pick-and-place machines are commonly used by modern factories to orient, locate, and place components. Before the components are attached, solder paste is stenciled onto the board using a stencil printer. Manufacturers can mount tens of thousands of components every hour using this technology. In order to verify that the solder has made full contact between the component and the board, the boards must be “heated” in an oven as a final step.

Soldering Paste Application

One of the initial steps in the SMT assembly process is to apply soldering paste. The silk-screen method is used to “print” soldering paste on the boards. Different stainless-steel stencils for “printing” the paste onto the board and various product-specific pastes are employed depending on the design of the board. The soldering paste will be applied just to the regions where components will be soldered, using a laser-cut stainless-steel stencil custom produced for the project.

Placement and Assembly of Components

The electrical components to be assembled are put into the SMT machine in trays or reels. Intelligent software systems ensure that components are not exchanged or misloaded accidentally during the loading process. The SMT assembly machine then uses a vacuum pipette to autonomously extract each component from its tray or reel and install it on the board using accurate pre-programmed X-Y coordinates.

Soldering of Components

We employ two different methods to solder electrical components, each with its own set of benefits based on the order number. The Reflow-soldering method is utilized for series production orders.
Boards are placed in a nitrogen environment and gradually warmed with hot air until the soldering paste melts and the flux vaporizes, fusing the components to the PCB. The boards are cooled after this stage. The components become permanently affixed to the board as the tin in the soldering paste solidifies, and the SMT assembly process is done.

AOI and Visual Check

The second-to-last step of the SMT assembly process is AOI and Visual Check Soldering. AOI visual inspections are performed on practically all series production orders to assure the quality of the assembled boards or to catch and remedy a mistake. The AOI system uses numerous cameras to automatically inspect each board and compare its look to the correct, pre-defined reference image.

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