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Effect of humidity on PCBA

2022-03-06

Effect of humidity on PCBA

Due to the precision and severity of PCB, the environmental sanitation requirements of PCB workshops are very high, and some workshops are even exposed to "yellow light" all day. Humidity is one of the indicators that needs to be strictly controlled,
Low humidity can lead to dryness, increased ESD, increased dust levels, easier plugging of formwork openings, and increased formwork wear. Practice has proved that low humidity will directly affect and reduce the production capacity. Too high will cause the material to absorb moisture, resulting in delamination, popcorn effect and solder ball. Moisture also reduces the TG value of the material and increases the dynamic warpage during reflow welding.
The surface is wet. Almost all solid surfaces (such as metal, glass, ceramics, silicon, etc.) have a wet water absorption layer (single molecular layer or multi molecular layer). When the surface temperature is equal to the dew point temperature of the surrounding air (depending on temperature, humidity and air pressure), this wet water absorption layer becomes a visible layer. The friction between metal and metal increases with the decrease of humidity. When the relative humidity is 20% RH and below, the friction is 1.5 times higher than that when the relative humidity is 80% RH.
When the surface of the epoxy resin contains moisture or condensation, the moisture absorbing layer or the like can not be seen on the surface of the plastic. The water in the monolayer on the surface penetrates into the plastic packaging device (MSD). When the monolayer is close to 20 layers in thickness, the water absorbed by these monolayer will eventually lead to the popcorn effect during reflow soldering.
The in the manufacturing process has many effects on production and manufacturing. Generally speaking, humidity is invisible (except for weight increase), but its consequences are pores, cavities, solder spatter, solder balls and bottom filling cavities.

In the process of any process, we attach great importance to the control of moisture and humidity, ranging from abnormal body surface appearance to unqualified finished products. Therefore, the normal workshop should ensure that the moisture and humidity on the substrate surface are properly controlled to ensure that the environmental indicators in the production process of finished products are within the specified range.