Why is process control measurement crucial for preventing defects in SMT PCB components?
 
The design of printed circuit boards is based on circuit schematics to achieve the functions required by circuit designers. The design of printed circuit boards mainly refers to layout design, which needs to consider the layout of external connections. Optimization layout of internal electronic components, optimization layout of metal wiring and vias, electromagnetic protection, heat dissipation, and other factors. Excellent layout design can save production costs, achieve good circuit performance and heat dissipation effect.
 
The integrity of printed circuit boards is crucial for ensuring the reliability of electronic products. Therefore, process control measurements must be performed to optimize SMT PCB assembly. This ensures that costly errors will not be discovered in the future, otherwise it may lead to high product failure rates and damage the reputation of electronic manufacturers.
   
The process control of SMT PCB assembly essentially involves adopting reliable processes during the printing, installation, and reflow soldering stages.
 
Let's take a closer look at them used for SMT PCB assembly:
 
Solder paste printing
Before SMT printing, the following must be checked:
The board has no deformation and a smooth surface.
The circuit board solder pads are not oxidized.
There is no exposed copper on the surface of the circuit board.
 
When printing solder paste, the following issues should also be noted:
Wooden boards should not be stacked vertically, nor should they collide.
The reference mark on the label should be consistent with the positioning hole on the template.
A thorough visual inspection is required. It is recommended that in this visual inspection, the distance between the eyes and the board should be 30-45 centimeters. Why is process control measurement important for preventing defects in SMT PCB components?
For optimal results, the temperature during solder paste use should be around 25 ° C, and the relative humidity should be within the range of 35-75%.
It is necessary to ensure that the solder paste used is effective and has not expired.
If using new solder paste and old solder paste, the mixing ratio should be 3:1.
You need to ensure that the bridge is not visible during printing.
The printing thickness must be uniform.
The template needs to be cleaned, so there is no dry soldering flux.
 
Chip installation
This is a crucial step that requires a high degree of accuracy. Some aspects that need to be noted at this stage include:
SMD must be compatible with the design files.
Debugging needs to be accurately carried out on the surface mount machine.
Control command signals and their editing should be carried out with caution.
You need to analyze the logical relationships between the driver components.
Need to clarify the operational process.
An appropriate maintenance plan is needed to ensure that the equipment is in good condition and that errors do not occur due to the condition of the equipment.

Reflow Soldering
This process mainly involves pasting SMD onto the circuit board. Essentially, solder paste will melt with increasing temperature, and components will stick to the board with increasing cooling temperature. Some process control aspects that need to be noted at this stage include:
Set the correct temperature curve and perform some real-time tests to avoid errors.
Vibration can cause serious damage during the welding process, so it needs to be avoided.
The solder joint must be crescent shaped.
There should be no residue or solder balls on the surface of the circuit board.
No bridging or false welding is allowed.
The solder joints should be smooth.