What is the influence of dew point of production environment on PCB welding?

What is the influence of dew point of production environment on PCB welding?

The circuit board manufacturer and the circuit board designer explain to you how the dew point of the production environment affects the welding of circuit boards

The working environment of tin on the circuit board is usually full of atmosphere. Most gases have no dew point at room temperature or high temperature, but will have an impact on water vapor. Generally speaking, the dew point refers to the condensation of water vapor when the partial pressure P of water vapor is higher than the saturated vapor pressure at the same temperature. Under a certain pressure, when the gas temperature is lowered, there is a chance for water vapor to start to condense. Dew point can also be used to indicate the dryness of gas. When the water vapor in the air is far away from the saturated vapor pressure, it can be determined that the relative humidity is low or the air is dry. Typical temperature

The working environment of tin on the circuit board is usually full of atmosphere. Most gases have no dew point at room temperature or high temperature, but will have an impact on water vapor.

Generally speaking, the dew point refers to the condensation of water vapor when the partial pressure P of water vapor is higher than the saturated vapor pressure at the same temperature. Under a certain pressure, when the gas temperature is lowered, there is a chance for water vapor to start to condense. Dew point can also be used to indicate the dryness of gas. When the water vapor in the air is far away from the saturated vapor pressure, it can be determined that the relative humidity is low or the air is dry. Typical temperature and humidity curve.

As for the influence of condensation on PCB welding, the main concern is the interference on wettability. The most important role of soldering operation is wettability. However, when there is a problem with environmental humidity and condensation, the wettability of soldering tin may be affected by the base metal (substrate) due to the easy formation of oxide film. The more serious the condensation of the environment is, the more easily the oxidation speed and removal ability of the metal surface become problematic. Therefore, keeping the soldering environment moderately dry is relatively important for the solderability of parts and circuit boards.

In addition to reducing the impact of moisture on circuit board welding, the well-known passive gas reflow operation is also one of the operation modes frequently used by circuit board manufacturers. For example, nitrogen protection is one of the typical methods. If the oxidation degree of the welding surface can be properly maintained, the interference to the wettability of the circuit board welding can be reduced.

The above is about the influence of dew point of production environment on PCB welding explained by PCB manufacturers and PCB designers.