First of all, we need to understand the process of SMT processing.SMT (Surface Mount Technology) is a method of mounting electronic components directly onto the surface of a printed circuit board. The technology has the advantages of simple structure, small size, fast signal transmission rate, etc. It has become the main way of modern electronic manufacturing.
In SMT processing, the generation of PCB voids is mainly related to the mounting process. SMD process generally includes three steps: unloading, mounting, and soldering.
Step 1: Unloading. In SMD processing, the need to use automatic unloading machine components from the material tray, due to the material surface adsorption of air dust and other impurities, thus leaving a large number of tiny air holes in the material surface.
Step 2: Mounting. During the mounting process, the component is clamped by a positioning device and moved to a predetermined position after being positioned. However, due to the presence of tiny air holes on the surface of the component, when the component comes into contact with the PCB surface, the air between it and the PCB surface is squeezed out and holes are formed.
Step 3: Soldering. During the soldering process, the hole is further heated, and under the action of the brazing material, the metal between the brazing material and the PCB pads is melted, and the component is soldered to the PCB surface.
In short, in the process of SMT processing, the generation of voids is mainly due to the presence of tiny air holes on the surface of the component, when the component is in contact with the PCB surface, the air between it and the PCB surface is squeezed out, forming voids.
There are other reasons for PCB voids:
Insufficient flux activation:
Voids form when the flux (a chemical used for soldering) is not sufficiently activated. The flux is critical to removing oxides and promoting proper wetting of the solder to the surfaces being joined.
Captured Volatiles:
Certain materials, such as moisture or solvents, may become trapped in the solder paste. During the soldering process, these materials become gaseous and create voids in the solder joint.
Insufficient preheating:
Inconsistent preheating of the PCB and components can cause the volatiles in the solder paste to evaporate quickly, creating voids.
Incorrect solder paste composition:
The composition of the solder paste, including the type and size of the solder particles, can affect the formation of voids. Using the wrong solder paste for a particular application may increase the likelihood of voids.
