Causes and Elimination Methods of Bubbles in Electronic Potting Compounds

During the encapsulation and protection of electronic components, PCBA modules, inverter inductors, and new energy power battery modules, the appearance of bubbles in potting compounds is a persistent challenge for process engineers. If these bubbles are not completely eliminated before curing, they create localized depressions, shrinkage cavities, and even cracking on the cured surface.

More critically, hidden internal bubbles significantly degrade electrical insulation, moisture resistance, and thermal dissipation efficiency, failing to meet rigorous industrial quality standards. As a professional electronic adhesives manufacturer,  Songxi Technology  leverages its extensive R&D expertise in high dielectric strength potting compound to analyze the three core causes of potting bubbles and share actionable elimination methods.

Air Entrainment via Mechanical Stirring and Improper Operation

Analysis of Causes

When mixing two-component potting compounds (such as silicone, epoxy, or polyurethane systems), high-speed mechanical stirring inevitably forces ambient air into the liquid mixture. If the subsequent vacuum degassing process lacks sufficient vacuum depth or duration, or if the potting speed is too rapid during injection into the component housing, the trapped air fails to escape completely before curing begins.

Elimination Solutions

Standardize Vacuum Degassing: After mixing the main agent and curing agent thoroughly according to the specified ratio, a secondary vacuum degassing step is mandatory to ensure the liquid is completely free of visible bubbles. Songxi Technology's  Potting Protection Adhesive Series features optimized air-release properties built directly into the molecular formulation to simplify this degassing step.

Component Preheating: Preheating the PCBA modules or external housings prior to potting effectively drives off micro-moisture on the material surfaces. Additionally, when the liquid compound makes contact with the warm component, its localized viscosity decreases immediately, accelerating the upward escape of bubbles.

Optimize Initial Curing Speed: Where process cycle efficiency permits, lowering the initial curing temperature extends the surface dry (tack-free) time, offering a wider natural degassing window for trapped air molecules.

Physical and Chemical Transformations During the Curing Process

Analysis of Causes

Many industrial potting compounds undergo an exothermic reaction during cross-linking. If the curing speed is excessively fast and the total heat output is too high, the internal temperature climbs sharply, causing trace solvents or plasticizers within the compound to volatilize into gas. Furthermore, if the compound exhibits a high curing shrinkage rate, the sudden volumetric contraction can tear microscopic voids within the matrix, producing shrinkage cavities that resemble bubbles.

Elimination Solutions

Deploy Automated Dispensing Equipment: For large-scale industrial manufacturing (such as EV power battery cell potting or automotive electronics protection), utilizing professional automatic potting machines ensures quantitative, steady-velocity dispensing, eliminating human errors and air inclusion from manual operations.

Select low viscosity flowable silicone: When selecting raw materials, prioritize high-quality formulations characterized by low viscosity, excellent fluid mobility, and low shrinkage rates. Songxi Technology's two-component series serves as an exceptional low shrinkage potting resin offers low viscosity, superb leveling properties, and exceptionally low curing and thermal stress, effectively minimizing shrinkage fractures and bubble trapping.

Moisture Infiltration and Secondary Reactions with Curing Agents

Analysis of Causes

This is the most frequently overlooked root cause. Certain curing agents are highly sensitive to ambient humidity. If the main agent packaging is not tightly sealed during repetitive multi-dose usage, or if the production workshop operates under high humidity, the material absorbs moisture. During curing, this water content undergoes a chemical side-reaction with active curing agent components (such as isocyanates), continuously generating carbon dioxide gas within the compound matrix.

Elimination Solutions

Execute a Material Contamination Test: If moisture contamination is suspected due to repeated container unsealing, mix the main agent and curing agent in a clean, dry beaker and place it directly into a laboratory oven at 60–80°C. If intensive bubbling persists after thermal curing, the compound has degraded via moisture absorption and should be discarded.

Strictly Regulate Shop Humidity and Bake Components: Maintain workshop relative humidity within a managed range (ideally 45%–65%). Plastic housings and multi-layer PCBAs prone to moisture absorption must be baked in an oven to thoroughly dehumidify before entering the potting line.

Prevent Cross-Chemical Contamination: Ensure that the workpieces are completely cleaned and dried. Avoid letting liquid adhesives touch un-evaporated cleaning solvents, mold release agents, conformal coatings, or incompatible adhesive tapes before curing, eliminating secondary chemical gas production.

Polyurethane potting compound with ≥25kV/mm dielectric strength for industrial instrument transformers

Eliminating bubbles in electronic potting compounds requires a systematic approach encompassing optimized material selection, rigorous process parameters, and tight environmental control. As your trusted high-performance polymer materials partner, Songxi Technology offers a versatile portfolio of potting solutions with thermal conductivities ranging from 0.6 W/m·k to 4.0 W/m·k, characterized by low viscosity and exceptional mechanical and physical stability. Whether you are addressing process bottlenecks in PCBA fixing, inverter encapsulation, or EV battery module thermal management, contact our expert technical team for customized adhesive engineering support.