Does FR4 plastic absorb water?

FR4 is a widely used material, especially in the electronics industry for making printed circuit boards (PCBs). It is a composite of woven fiberglass and epoxy resin, which gives it its strong and durable properties. However, one common concern is whether FR4 plastic absorbs water and how it affects the material.

Water Absorption in FR4

FR4 plastic is not highly porous, meaning it doesn’t absorb water as readily as some other materials like wood or certain types of plastics. However, it is not completely impermeable to moisture. When exposed to high humidity or submerged in water for extended periods, the material can absorb a small amount of water through its surface. This is especially true if the resin is not fully cured, leading to moisture infiltration.

Effects of Water Absorption

While FR4 does absorb some water, its absorption rate is relatively low compared to other materials. When moisture does enter, it can affect the dielectric properties of the material, potentially altering the performance of electronic components mounted on the PCB. Over time, this water absorption can lead to swelling, warping, or degradation of the resin, especially if the FR4 is exposed to extreme conditions.

Preventing Water Absorption

To minimize the impact of water absorption, manufacturers often apply protective coatings to the FR4 surface. Additionally, ensuring that the FR4 is properly cured and stored in dry conditions helps reduce the chances of moisture infiltration. Using encapsulation techniques for critical applications can further protect the material from water damage.

Conclusion

FR4 plastic does absorb water to a small degree, but its performance is generally stable under normal conditions. Proper care in handling and storage can mitigate any potential negative effects of moisture absorption.