PCB Assembly

Explained: What are the Steps in SMT Assembly Process?

Surface Mount Technology Assembly Process

Printed circuit boards continue to be in high demand as they are a fundamental component of every working electronic in existence. To meet the fluctuating demands of the market, a new manufacturing approach was created which is the SMT assembly process or surface mount technology assembly. The idea for this method of manufacturing is to automate the mass production of quality printed circuit boards which are going to be used to integrate with different devices.

With that said, we’ll be delving into the world of surface mount technology and learning about the steps that entail the whole process from start to finish; and an optional step if ever the boards don’t meet the desired quality.

Components Placement in SMT Assembly

The appeal of using surface mount technology

Before we proceed further into the topic, let’s explore what makes the SMT assembly process an attractive choice for many electronic brands. What’s the appeal that draws the attention of companies to this methodology of manufacturing printed circuit boards? In this section, we’ll get to learn about what makes companies drawn to the usage of SMT technology.

  • Opens up miniaturization – some electronic brands are drawn to the idea of miniaturization and SMT assembly can provide that since the boards made through this method are noticeably smaller than through-hole assembled ones. In short, smaller circuit boards give way to more compact devices. One good example of this case is the smartphone we use every day.
  • Heightened electrical performance – SMT-assembled PCBs also have a higher performance and functionality since the components are tightly packed on a small board. This high component density results in a near-perfect signal integrity making the device that it is integrated into highly responsive.
  • Efficient, can be automated – the main appeal of the SMT assembly process is that it is a very efficient way to manufacture PCBs. The assembly setup consists of an assembly line with pick and place machines which heightens production speed and cuts down costs.
  • Less prone to manufacturing errors – SMT-assembled PCBs rely on the use of an assembly line managed by automated machinery. As a result, manufacturing errors are not or least likely to happen.
  • Affordable due to reduced manufacturing costs – SMT-assembled PCBs also use fewer steps and processes which could influence the final purchasing cost. As a result, they are a budget option for electronic brands that want PCBs but are cutting down expenses for the time being.

The steps in surface mount technology (SMT) assembly

The steps in the SMT assembly process are pretty straightforward due to their automated nature. However, we’ll still cover them in detail so that you can have a clearer understanding of what happens to the PCBs whenever a step in the process is finished. Here are the steps that encompass the SMT method of assembling printed circuit boards.

1. Mounting the components on the board

The first step that entails the SMT assembly process for PCBs is to mount the components. What happens here is that blank laminates which serve as the base material for PCBs will pass along the assembly line where pick-and-place machines will install components on the blank PCB.

The position of the components will correspond to the design files submitted by the client and uploaded to the assembly line so that the machinery can follow the layout and not miss a placement.

2. Soldering the components via reflow soldering

Reflow Soldering in SMT Assembly

Once the components are in position on the printed circuit board, the next step is to get these components locked into place. This is done through reflow soldering in which the solder paste is melted and then soldered into the mounted components to keep them in place once the soldering paste has cooled down.

The process of soldering the components is done on the manufacturing line through a machine that dispenses the solder paste.

3. Cleaning the SMT-assembled printed circuit board

Once the components are soldered into place, the next step in the SMT assembly process is cleaning the assembled PCB. Sometimes, after soldering the components into their respective positions, traces of toxins and hazardous residues continue to linger on the printed circuit board. The finished PCBs undergo cleaning through a dedicated cleaning machine to remove these hazardous remnants from reflow soldering.

A note regarding this step is that cleaning can occur on either the assembly line with the cleaning machine being the next stopover for the assembled PCBs or done after manufacturing in which the cleaning machine is a standalone station away from the assembly line.

4. Post-assembly inspection

AOI After SMT Assembly

After cleaning, factory personnel will check and inspect the printed circuit boards that were manufactured through the SMT approach. The personnel will use specialized machines such as an automated optical inspection and X-rays to assess the quality of the PCBs and the soldered components.

If the quality meets the desired standards of the clients, the PCBs are given final preparations before they are shipped to their recipients. However, if defects from mounting are detected during inspection – the PCBs will have to go through an optional step in the process.

5. Reworking the printed circuit board, if necessary

PCBs that are discovered to be defective during the inspection will have to undergo an optional step in the SMT assembly process which is reworking. Reworking can go in one or two ways – repairing or re-manufacturing. In repairing, defective parts are fixed and tweaked and then tested to see whether the PCB is working as intended.

However, in re-manufacturing – the SMT-assembled boards are dismantled with care, cleaned, and thoroughly inspected. Any components that can be fixed are repaired whereas parts that are beyond fixing are replaced. Tests will follow after repairs and replacement of parts and if the PCB is functioning as intended; it is then prepared for packaging.

Straightforward and efficient manufacturing

The SMT assembly process is a straightforward yet effective approach to mass-producing printed circuit boards over a short period. However, these boards will have to undergo a process wherein the components are assembled, soldered, cleaned, and tested before they are delivered to the clients that filed the order.

After all, the end goal of your manufacturer is to ensure that the SMT-assembled boards you’ll receive soon meet your standards and work for the function that it is made for.

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