Common problems and countermeasures of glue in LED packaging process

LED Yellowing

LED yellowing is a common issue that can occur during the manufacturing or curing process. Here are the main reasons and solutions:

Causes:

  1. The baking temperature is too high or the time is too long.
  2. An incorrect ratio of the glue is used, especially when there is more A-component than B-component, which increases the likelihood of yellowing.

Solutions:

  1. Cure and demold the AB glue at 120-140°C for 30 minutes. Exceeding 150°C may cause yellowing.
  2. For better results, cure at 120-130°C for 30-40 minutes. If the temperature goes above 150°C or the curing time is extended, yellowing is likely to occur.
  3. When producing large lamp holders, consider reducing the curing temperature to avoid discoloration.

LED Bubble Problem

Bubbles in LED components can affect performance and appearance. The causes include:

Causes:

  1. Bubbles in the bowl: Poor adhesion of the bracket.
  2. Bracket bubbles: High curing temperature causing excessive epoxy reaction.
  3. Cracking rubber or bursting top: Insufficient curing time leading to incomplete or uneven curing of the epoxy resin. This may also happen if the AB glue has exceeded its service life.
  4. Surface bubbles on the lamp head: Difficulty in defoaming the epoxy glue or insufficient vacuum application by the user. Long glue time can also contribute to this issue.

Solutions:

  1. Improve the process or consult with your epoxy supplier for recommendations based on usage conditions.

LED Bracket Creep

This occurs when the bracket appears to move or shift after the curing process. Possible reasons include:

Causes:

  1. Uneven surface of the bracket leading to capillary action.
  2. The presence of volatile substances in the AB glue.

Solution:

  1. Contact the supplier for further assistance and product support.

LED Package Short-Baked Off-Die and Long-Baked Discoloration

Discoloration or off-die issues can occur due to improper baking conditions:

Causes:

  1. Dense stacking in the oven leading to poor ventilation.
  2. High local temperatures in the oven.
  3. Pollutants of different colors present in the oven environment.

Solutions:

  1. Improve air circulation within the oven.
  2. Clean any color stains and verify the actual temperature inside the oven.

Uneven Color or Gelling Time Among Lamps on the Same Row of Brackets

This issue often arises from inconsistent mixing of materials:

Causes:

  1. Inadequate stirring during the mixing process.

Solutions:

  1. Ensure thorough mixing, especially in the corners of the container, to achieve uniform consistency.

Difficulties in Demolding

If the product is hard to demold, it could be due to:

Causes:

  1. Issues with the AB glue or the glue not reaching the required hardness.

Solutions:

  1. Contact the supplier to confirm the correct curing temperature and time.

Same Dose, Different Colors

If the same amount of material is used but the color varies, consider the following:

Causes:

  1. Uneven toner concentration or sedimentation of the toner.

Solutions:

  1. Warm the toner before use and mix thoroughly to ensure even distribution.

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