The three main causes of bubble formation: 

The main sources of air bubbles in potting compounds lie in three stages: the mixing and stirring process, the curing reaction process, and the influence of ambient moisture. Identifying the root cause of the bubbles is the first step toward completely resolving the issue. 

1. Air bubbles entrained during mixing and blending 

If manual or mechanical stirring is too fast or carried out in random directions, a large amount of air will be entrained into the adhesive. Bubbles in high‑viscosity adhesives are difficult to eliminate by natural rising, whereas in low‑viscosity adhesives with slower curing speeds, bubbles have sufficient time to rise to the surface and disappear on their own. 

2. Air bubbles generated during the curing process 

If the curing temperature is too high or the proportion of curing agent is excessively large, the adhesive surface will quickly form a skin, preventing gases or volatile substances generated internally from escaping. These trapped within the adhesive layer result in pinholes. A high shrinkage rate during adhesive curing, as well as an excessive addition of solvents and plasticizers to the adhesive, can also easily lead to bubble formation during the curing process. Such bubbles typically require adjustments at the formulation level to be resolved at their root. 

3. Bubbles related to dampness 

Polyurethane materials are extremely sensitive to moisture. If the printed circuit boards and components are not thoroughly dried, or if the ambient humidity is too high, the isocyanate component in the adhesive… -NCO ) It will undergo a chemical reaction with water to produce carbon dioxide ( CO ₂ ) Gases can form bubbles or even pinholes. In addition, if the adhesive packaging is not tightly sealed and absorbs moisture, this issue can also occur.

There are air bubbles during the grouting process—how can this be resolved? 

1. Adjust the temperature 

During the potting process, if bubbles appear, you can try adjusting the temperature. Generally speaking, increasing the temperature can enhance material fluidity and help eliminate bubbles. However, it’s also important to avoid overheating, as this could cause discoloration or degradation of the material. 

2. Increase Air Pressure 

Applying pressure is also an effective method for eliminating air bubbles during potting. Before pouring the adhesive, increasing the pressure inside the container can help force the air to rise and escape, thereby removing bubbles. However, it’s equally important to avoid overpressurizing, as this could damage the product. 

3. Add Vibration 

Adding vibration can help distribute liquid materials more evenly, expel air bubbles, and eliminate voids. Vibrators or vibration platforms can be used to apply vibration during the potting process. 

4. Screening Materials 

If the above methods fail to completely eliminate bubbles, you can try replacing the potting compound—especially by using high‑quality potting materials, which can effectively prevent bubble formation. 

In summary, encapsulating adhesives that produce bubbles can severely compromise construction quality. To address bubble issues, one can select appropriate materials and formulations, reasonably adjust process parameters, ensure stable equipment operation, and employ specialized defoaming agents to tackle bubble problems. It is hoped that, through the introduction in this article, readers will gain a better understanding of the causes of bubble formation in encapsulating adhesives and the corresponding solutions, enabling them to handle various challenges associated with encapsulating adhesives more effectively. 

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