PCB News - What factors affect the welding process of PCBA board

What factors affect the welding process of PCBA board
With the development of electronic products in the direction of multi-function, high-density, miniaturization, and three-dimensionality, a large number of micro-devices are increasingly used, which means that there are more and more device I/Os per unit area, and heating elements will also More and more, the need for heat dissipation is becoming more and more important. At the same time, the thermal stress and warpage caused by the different CTE of many materials makes the risk of assembly failure increasing, and the subsequent probability of early failure of electronic products will also increase. Come bigger. Therefore, the soldering reliability of PCBA boards has become more and more important. What are the factors that affect the welding process of PCBA board?

The factors that affect the processing of PCBA board A are based on the existence of water in the PCBA board, the way of water vapor diffusion and the change of water vapor pressure with temperature to reveal that the existence of water vapor is the primary cause of PCBA board A bursting.

The moisture in the PCBA board mainly exists in the resin molecules, as well as the macro-physical defects (such as voids, microcracks) existing in the PCBA board. The water absorption rate and equilibrium water absorption of epoxy resin are mainly determined by the free volume and the concentration of polar groups. The larger the free volume, the faster the initial water absorption rate, and the polar group has an affinity for water, which is the main reason why epoxy resin has a higher water absorption capacity. The greater the content of polar groups, the greater the equilibrium water absorption. In summary, the initial water absorption rate of epoxy resin is determined by the free volume, while the equilibrium water absorption is determined by the content of polar groups.

On the one hand, the temperature of the PCBA board increases during lead-free reflow soldering, which causes the water in the free volume and the polar group to form a hydrogen bond, which can obtain enough energy to diffuse in the resin. The water diffuses outward and gathers in the voids or microcracks, and the molar volume fraction of water in the voids increases. On the other hand, as the welding temperature increases, the saturated vapor pressure of water also increases, which affects the processing.
Pay attention to standardized operation methods and processing techniques when producing PCBA boards to ensure product quality while improving production efficiency. And realize the construction of a safe production environment.
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