This is another method that is involved in the process of PCB manufacturing for the mounting of the components.
- Also known as planner mounting.
- Its discovery came in in the 1980s.
- This is the most popular method that is being employed in today’s PCB manufacturing process.
- As you can hear from the name suggests, the components are mounted on the surface.
- Initially, the process was done manually but today it is done by the use of advanced machinery thanks to the technology revolution that has taken place.
- Surface Mount Technology is not used in Single Layer PCB much, it’s normally used in Multilayer PCB and Flexible PCB boards.
Surface mount technology involves a very critical process where components are mounted on the surface of the board instead of them being mounted through the holes as the names suggest. The components are then soldered by the assembler onto pads and boards.
- Using the assembler, you apply the solder pastes into the parts where the components will be placed.
- Use the stencil or the solder screen to ensure that the solders have been placed in the exact required position for the component placement.
- After that, inspect the board to check for the solder defects and ensure that all the solders are in a good position.
- Any time you detect the defects, it is either the assembler corrects the defects or if they are too much the assembler will remove them and reapply afresh.
- The process of inspection is very important because it will determine the quality of the solder during the end of the process hence affecting the functionality of the board.
- After inspection, the assembler will now place the components accurately following the designs given by the designer. Originally, this was done manually by workers by the use of hand tools. Today development of the pick and place machines has made the work easy, accurate and fast.
- After placement, the components are soldered into pads to make sure that they remain together as expected. Here, the board undergoes a reflow process in which it is passed through the furnace to remelt and liquefy.
The SMT employs the use of vias in order to connect different components together. There are three types of vias that are employed throughout the process. That is, blind vias, through vias and burred vias. Also, special devices are used in the process of SMT. These devices are called the Surface Mount Devices.
Types of the Surface Mount Technology.
It is a full SMT board that has parts on both sides of the PCB or on one side of the PCB.
Only SMD components are found in this type of board.
Active surface mount devices and DIPs are located on the primary side of the PCB while the surface mount chips are the secondary side of the board.
I this type, you will find passive SMCs on the secondary side of the board while the primary side is made of the DIPs only.
It contains only discrete mount components and they are all mounted on the bottom side.
The discrete components include; transistors, resistors and capacitors.
Applications of the SMT components.
- Making of very small and compact PCB boards.
- Smartphones boards
- Computer and laptops motherboards.
- Internet of things devices.
- Involved in the manufacture of communication and telecommunication equipment.
- Manufacture of the medical devices
- Finds application in the transport components
- Applied in the lighting components
Advantages of the SMT components.
- They have very low RF interference because they do not have leads. Due to this same reason, the distribution of parameters must be very lower.
- It takes lower packaging materials and this is due to the advanced manufacturing that is being involved.
- The production cost has been drastically lowered compared to that of the THT product of the equivalent magnitude.
- Component failure is very low due to the consistent of the fabrication process being involved.
- Less expensive process and very economical due to the use of more advanced technologies like PCB panelization and pick and placing mechanism.
Disadvantages of the SMT components.
- It is not the best method to mount high wattage components since they can dissipate a lot of heat which end up damaging the SMTs.
- This is made up of very tiny components and therefore, if there is damage it is very complex to repair them compared to the THT components. This means time consuming in repairing and also very expensive.
- This type of board cannot be used in a place where rough holding is involved. Hence it is limited in where it is applied.