The solderability of circuit board holes affects the quality of soldering
1.Poor solderability of circuit board holes can result in virtual soldering defects, affecting the parameters of components in the circuit and causing unstable conductivity between multi-layer board components and inner layer wires, leading to the failure of the entire circuit function. The so-called solderability refers to the property of the metal surface being wetted by molten solder, that is, a relatively uniform and continuous smooth adhesive film is formed on the metal surface where the solder is located. The main factors affecting the solderability of printed circuit boards are:
2. Composition of solder and properties of the solder material
Solder is an important component in the chemical treatment process of welding, which is composed of chemical materials containing flux. The commonly used low melting point eutectic metals are Sn Pb or Sn Pb Ag. The impurity content should be controlled in a certain proportion to prevent the oxide generated by impurities from being dissolved by the flux. The function of solder is to help wet the surface of the circuit board by transferring heat and removing rust. Generally, white rosin and isopropanol solvents are used.
3. Welding temperature and cleanliness of metal plate surface
The welding temperature and the cleanliness of the metal plate surface can also affect weldability. If the temperature is too high, the diffusion speed of the solder will accelerate, and it will have high activity, which will quickly oxidize the surface of the circuit board and solder melting, resulting in welding defects. The surface of the circuit board will also be contaminated, which will affect the solderability and cause defects, including tin beads, tin balls, open circuits, poor glossiness, etc.
4. Welding defects caused by warping
During the soldering process, circuit boards and components may warp, resulting in defects such as virtual soldering and short circuits due to stress deformation. Warping is often caused by temperature imbalance between the upper and lower parts of the circuit board. For large PCBs, warping can also occur due to the weight of the board itself falling. Related article recommendation: Ordinary PBGA devices are about 0.5mm away from printed circuit boards. If the devices on the circuit board are large, as the board cools down and returns to its normal shape, the solder joints will be under stress for a long time. If the device is raised by 0.1mm, it is enough to cause virtual soldering and open circuit.
5. The design of the circuit board affects the welding quality
In terms of layout, when the size of the circuit board is too large, although soldering is easier to control, the printed lines are long, impedance increases, noise resistance decreases, and costs increase; If it is too small, heat dissipation will decrease, welding will be difficult to control, and adjacent lines may interfere with each other, such as electromagnetic interference from circuit boards.
