Table of Contents
Complete SMT LINE PROCESS
What does SMT stand for?
SMT Stands for Surface Mount Technology. A technology used for the assembly of PCB Boards with the help of automated machines is called SMT Machine. SMT Machine places the components on the PCB Board for the assembly of electronic products led lights, home appliances.
What is the SMT LINE Process?
SMT LINE Process represents assembly lines of the PCB Board using SMT machines and peripherals. Two main categories of SMT Lines are Full Automatic SMT Line and Semi-Automatic SMT Line.
1. PCB Loader:
Starting of SMT Assembly Line Begins with Automatic PCB Loading of PCB boards into the SMT assembly line with the help of PCB Loader. The operator installs the PCB boards into the magazine of the PCB Loader. PCB Loader automatically Loads PCB boards from the Magazine into the conveyor.
There are numerous kinds of PCB Loaders depend on the requirement of the PCB Board.
2. Solder Paste Printer:
The second step is to apply the solder paste on the PCB board during the SMT line process. PCB Loader loads the PCB board and transferred it to the Solder Paste Printer. An automatic solder paste printer applies the solder paste onto the PCB Board.
To accurately place the solder paste on each pad of PCB board the solder paste printer. It takes 25mm per second to apply solder paste on the PCB board but the total time depends on the size of the PCB board.
The squeegee speed, squeegee pressure, and angle are adjusted according to the requirement of the product.
3. Solder Paste Inspection “SPI”
As the components become smaller. The SMT line process will become more complex it is necessary to maintain the quality of applied solder paste on the PCB board. The applied paste with the help of a Soldering Paste Inspecting machine called “SPI”.
The SPI Inspection machine uses 3D technology to detect the bridges of the solder paste. and can accurately measure the applied amount of solder paste. as a result the use of SPI significantly improves yield by saving time during inspection.
4. Pick and Place Machine
Above all Placing, the components on the PCB board is one of the most important stages during the SMT line process. SMT Machine handles this process known as pick and place machines. The process begins by the receiving applied solder paste on PCB board from the solder paste printer into SMT Machine.
SMT Machines scans the mountable components and points PCB board with a modern linear camera. The camera scans each component with a modern Artificial Intelligence Algorithm and the head picks pick the component from the feeder and places it onto the PCB board.
A pick and place machine can have multiple heads with multiple spindles. Normally Modern Pick and place machines have two heads and each head has eight spindles. In each spindle, there are nozzles of different sizes which are capable of different kinds of components from the feeders.
5. Pre – AOI (Automated Optical Inspection)
Aoi Inspection is a necessary part of the PCB Assembly. However, pre-AOI works to inspect components placed by SMT machine before soldering results for detection of wrong mounted chips on PCB Board. AOI uses Optical Image Processing technology to inspect the mounted components on the PCB board.
There are two kinds of AOI.
In short Inline AOI is more expensive than offline AOI because they have a high image processing capability than offline AOI. The biggest advantage is the Inline AOI is installed inside the SMT Line process which makes the line fully automatic.
In addition, Offline AOI is cheaper than the online AOI because offline AOI will be used to inspect the PCB board after the soldering process is done. In case of faults in the PCB board, they can be repaired by doing PCB board reworking.
6. Reflow Oven:
Reflow Oven is a device that is used for the soldering of PCB boards in the SMT Line process. After the mounting and inspection of components on the PCB board, the next section is to attach the components with the PCB board this process can be done with the help of a reflow oven and the process is called soldering of PCB boards.
There are different kinds of soldering processes such as wave soldering and reflow oven soldering process.
- The reflow oven soldering process begins with the passing of the PCB board into the reflow oven. The PCB board undergoes different temperature levels.
- The first two zones of reflow ovens are preheating zones in which hot air is passed into the chamber of the reflow oven and the solder paste becomes preheated results in the partial melting of solder paste.
- The third and onward zones are heading zones of the reflow oven in which the hot air passed on the chamber of the reflow oven melts down the solder paste properly and makes the accurate shape and position of the component attached on PCB board.
- The last two zones are cooling zones during normal soldering the cooled air passes into the reflow oven which results in the attachment to components onto the PCB board.
Type of Reflow Oven :
- Lead-Free Air Reflow Oven
- Nitrogen Reflow Oven
Zones Types in Reflow Oven :
- 6 Zones Reflow Oven
- 8 Zones Reflow Oven
- 10 Zones Reflow Oven
- 12 Zones Reflow Oven
In addition, Each zone type has different cooling zones as well as heating zones such as standard reflow oven has 8 zones. In which the first two zones are preheating zones and third, fourth, fifth, and sixth are heating zones and the last two zones are cooling zones.
7. PCB Unloader and Cooling Buffer:
Each type of zone has different cooling and heating zones, for example, a standard reflow oven has 8 zones where the first two zones are preheating zones and the third, fourth, fifth, and sixth zones are heating zones and the last two zones are cooling zones.
After the soldering, the PCB board is not completely cooled to cool the PCB board completely the Cooling buffer help to decrease the temperature of the PCB board.
- PLC Control
- Touch Panel
- Smema Communication
- Individual operation of lift rack
- PCB Loading : 10EA
- Simple Operation