LED Power Supply Silicone Potting Compound Issues: Causes and Solutions
Time:2024-11-11
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Causes and Solutions for Issues in LED Power Supply Silicone Potting Compounds
Bubble Formation in Potting Compounds: Primary Causes and Analysis
1. Air Entrapment During Mixing
Air may enter during mixing and is not completely removed during the pouring and curing process, leading to small bubbles.
• Observed Issue: Small bubbles in the potting compound.
• Solution: After mixing the base resin and curing agent, apply vacuum degassing. Preheating the product to be potted can also help release trapped air. Curing in a room with low temperature and humidity can allow more time for air to escape.
2. Moisture Reaction with the Curing Agent
Moisture can react with the curing agent, resulting in the formation of gas bubbles.
• Observed Issue: Large bubbles in the potting compound.
• Solution: Potential causes of moisture reacting with the curing agent include:
• The base resin may have absorbed moisture over multiple uses or due to an improperly sealed container. To confirm the cause, mix the base resin and curing agent in a dry cup and cure in an oven at 60-80°C. If bubbles still form, the base resin may have deteriorated and should not be reused.
• Excessive moisture within the product being potted. Preheat the product before retrying.
• Reaction between the mixture surface and ambient humidity. In this case, cure in a dry environment or use an oven if suitable for the product.
• Contact of the mixed resin and curing agent with other chemicals (e.g., solvents, release agents, varnishes, adhesives). Ensure that any such contaminants are removed before the next trial.
Soft or Sticky Cured Potting Compound
To address issues of overly soft or tacky cured compounds:
• Solution: First, try a quick cure at 60-80°C for 1-2 hours. If no further curing occurs, likely causes include an incorrect mixing ratio or inadequate mixing of the base resin before curing. Contact with other chemicals, such as solvents, release agents, grease, or partially cured base resin, can also affect the cure. If some areas remain soft after curing, this may indicate uneven mixing of the base resin and curing agent. To prevent this, ensure thorough mixing and transfer to a clean container before pouring into the product.
Adjusting Potting Compound Curing Time and Working Time
The working time of most two-part potting compounds ranges from 1 to 45 minutes. In certain conditions, external factors may significantly alter the working time, so it’s essential to communicate with the supplier rather than attempt to change working time by adding more curing agent, which can irreversibly alter the product characteristics. For manual operations, the working time is approximately 45 minutes, and curing time ranges from 4 to 24 hours, depending on the base resin type, temperature, and potting volume. Heat curing (60-80°C) in an oven or with infrared heat can accelerate curing.
Viscosity and Hardness of LED Power Supply Potting Compounds
Do not alter viscosity by adding more or less curing agent, nor adjust hardness by changing the base resin or curing agent amounts, as these modifications can negatively impact the mechanical properties of the cured polyurethane. The viscosity of two-part potting compounds can be adjusted by:
• Using a low-viscosity curing agent, though this may alter the mechanical and thermal properties of the cured material.
• Adding thixotropic agents to increase viscosity, which helps improve the stability and thixotropy of the liquid mixture without affecting mechanical and thermal properties.
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