In the field of electronic manufacturing, sealing glue potting is a key process to ensure the reliability, insulation and protection of electronic components. However, bubbles generated during the glue potting process will not only weaken the sealing performance, but may also cause insulation failure, poor heat dissipation, and even cause product failure. This article will start from the root cause of the bubble generation and elaborate on the all-round solution for you.
Causes of Bubble Generation
The bubbles generated in electronic sealing glue potting are mainly caused by the four major factors of materials, processes, equipment and environment.
Material Factors: The characteristics of the potting glue itself are an important cause of bubbles. The viscosity of the glue is too high and the fluidity is poor, which makes it easy to entrain air during the glue potting process; the volatile components contained in some glues evaporate to form bubbles during the curing process; in addition, if the ratio of the two-component glue is not accurate, the reaction will not be complete and gas will be generated.
Process Factors: Improper operation of the glue potting process is the direct cause of bubbles. If the speed is too fast and the direction is chaotic during the stirring process, a large amount of air will be drawn into the glue; if the speed is too fast and the method is unreasonable during the glue filling, such as direct impact filling from a high place, air will be brought in; if the temperature rises too fast during the curing process, the gas inside the glue will be solidified before it can be discharged, thus forming bubbles.
Equipment Factors: The performance and state of the glue filling equipment have a significant impact on the generation of bubbles. Unstable pressure and inaccurate flow rate control of the glue filling machine will cause uneven glue filling and bubbles; leaks in the internal pipes or valves of the equipment will also cause air to mix into the glue.
Environmental Factors: Environmental conditions should not be ignored. When the ambient humidity is high, some glue will absorb moisture and react to produce gas; too low temperature will increase the viscosity of the glue, which is not conducive to the discharge of bubbles; and too high temperature may accelerate the curing of the glue, causing bubbles to be trapped inside.
Multi-dimensional Efficient Solutions
Material Optimization: give priority to potting glue with low viscosity, low volatility and defoaming agent, and avoid using fillers that are easy to produce gas; strictly control the quality of materials to ensure the stability of the quality of potting glue and related auxiliary materials, and vacuum degas the glue before use, and properly seal and store it after opening.
Process Improvement: stir the glue at a low speed and uniform speed to prevent air from being drawn in; use the method of slow pouring along the wall to control the pouring speed and avoid bubbles caused by impact; use step-by-step heating during curing to leave time for bubbles to be discharged.
Equipment Upgrade: choose a precision glue pouring machine to accurately control the flow rate and pressure, and regularly maintain and calibrate to prevent leakage and blockage.
Environmental Control: control the workshop humidity below 50% RH and the temperature at 25-30℃, while keeping the workshop clean and reducing pollutants adsorbing air.
Add Activate Molecular Sieve Powder: In the process of electronic sealing glue pouring, powdered molecular sieve is used as an amorphous desiccant, which can effectively inhibit the generation of bubbles by adsorbing gas and optimizing the performance of glue. Choose 3A or 4A activated molecular sieve powder with suitable pore size, and use their structural properties to preferentially absorb water and low-boiling-point solvents in the glue liquid, blocking the generation of bubbles caused by the reaction of water and curing agent and solvent volatilization.
PM molecular sieve powder has the characteristics of good dispersibility, fast adsorption speed, and strong activity. It can adsorb impurities such as water that affect the quality of electronic sealing tank glue without changing its physical and chemical properties.
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