The PCB industry used to fabricate boards by using the through-hole approach during the mounting phase. However, the companies have adopted the new SMT approach, which proved to deliver a better outcome and be more efficient.
The SMT stands for surface-mount technology. The idea was to eliminate the requirement that the leads of the components go through the PCB. The alternative suggested was to solder the elements, and that turned out to be an improved solution.
The SMT assembly procedure enhanced over time, and it is the primary approach to PCB fabrication today. You can use boards manufactured this way throughout all electronic industries. The chances are you will find them in smart phones, computers, refrigerators, TVs, etc.
What are the benefits of SMT assembly?
The surface-mount technology requires familiarity with the entire process. It has specific demands for the design phase as you need to use special PCB tools. Once the design is ready, the manufacturer will do the testing with a single board.
The prototype has the task of confirming that the fabrication based on that design is possible and error-free. Once you confirm that, the entire process is virtually automated, and requires minimal involvement. The only thing needed is the right machines that can meet the challenge of fabricating the particular PCB.
Thanks to that automation, SMT assembly minimizes errors that may happen due to human involvement. It secures improved reliability and consistency of the boards. Here are some other advantages that this approach ensures:
Reduced size and weight – by soldering components directly on the board, the SMT saves plenty of room. That is how you can maintain the reliability and performance of a PCB while reducing its size and weight.
More components in a smaller space – it is not only about reducing the size, but SMT also enables us to put more elements in a restricted area. That is how these boards can perform better than their predecessors while keeping their compact design.
Money savings – if you don’t use the same amount of materials as before, the cost should be decreased, too. Additionally, there is no need to go through hole-drilling operations to mount components. Thanks to that, you can also lower the labor costs.
What is the placement of components?
The first part of the procedure we will discuss is component placement. It may seem like a basic step of the process, but it is essential. The reason for that you need to mount the components on the printed circuit board properly.
The designing process must be error-free. Since the fabrication will merely follow the commands received in the design, that is how you ensure everything goes smoothly.
The task of the designer is to assess the position carefully. The idea is to have the production phase in mind when placing the components. The current manufacturing capabilities need to be capable of meeting the expectations. If that is not possible, the manufacturer might be unable to print the parts, which will automatically discard the PCB, and return the entire process to the beginning.
The experts recommend starting the component writing with simple structures. Once you complete that part, you can move on to those parts that have a complex structure chip type.
First, let’s clarify what do we refer to when we mention SMT printing. The process involves the solder paste added to the pads of the board, which involves screen printing that doesn’t require direct contact, as well as contact stencil printing. The specifics of the SMT assembly imply that this technology requires screen printing that belongs to the contact type.
Everything starts by stirring the paste for soldering. You must keep in mind the uniformity and viscosity of the paste while you are getting in ready. As for the viscosity, it may affect the printing quality significantly. The idea is to follow the current printing standard and adhere to its requirements. You don’t want the viscosity to be far from the recommended range because you may disrupt the printing quality.
You will need to store the paste in a suitable environment, too. The industry experts recommend keeping the temperature low. The ideal temperature range goes from 0 to 5C. The reason why is that the segments of the paste can separate naturally in those conditions.
Now, when you plan to use the paste, you should take it out of the fridge and allow it to rest at room temperature. Give it about 20-30 minutes to heat naturally, and use a glass rod to stir it. It will take about 15 minutes of stirring to get the paste ready for use.
You should aim to keep the optimal room temperature while using the paste. That means the heat range should be between 20C and 25C. Another important factor to consider is humidity because too much humidity may affect the paste. That is why you should give your best to keep it around 50%.
Once you apply the paste to the pad, they will become an integral part of the SMT assembly. That is because they are an essential requirement for component soldering.
Here is what happens during the printing phase – the pressure of the blade will spread the paste throughout the pad. Next, the stencil’s thickness will keep at up to 0.15mm for optimal results. It is interesting to mention that the industry experts believe the silkscreen paste for soldering makes the paste fuller and improves the quality of the soldering.
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