Common problems and solutions in the process of plug-in LED packaging

Packaging glue type:

1. Epoxy Resin

2. Silicone

3、胶饼 Molding Compound

4. Silicone Hybrid

According to the molecular structure, epoxy resins can be roughly divided into five categories:

1. Glycidyl ether epoxy resin

2. Glycidyl ester epoxy resin

3. Glycidylamine epoxy resin

4. Linear aliphatic epoxy resin

5. Cycloaliphatic epoxy resin

Introduction to epoxy resin characteristics:

A glue:

Epoxy resin refers to an organic polymer compound containing two or more epoxy groups in the molecule, generally bisphenol A type epoxy resin

B glue:

Common organic compounds are anhydride compounds, such as: MHHPA

EPOXY:

Ether Bond is a weaker bond in epoxy encapsulation resin, which is prone to yellowing and light decay. A high proportion of A agent leads to more Ether Bond, which is prone to yellowing. Silicon resin replaces it with Si-O bond.

LED requirements for epoxy resin:

1. High reliability

2. High light transmittance.

3. Low viscosity, easy to degas.

4. The heat of hardening reaction is small.

5. Low thermal expansion coefficient and low stress.

6. High thermal stability.

7. Low hygroscopicity.

8. Excellent adhesion to metal, glass, ceramic, plastic and other materials.

9. Resistance to mechanical impact.

10. Low elasticity.

1. Glue cracking caused by poor hardening

Phenomenon: Cracking occurs in the colloid.

Cause: The hardening speed is too fast or the baking temperature is uneven, resulting in excessive internal stress accumulation in the colloid itself or between it and the metal material.

Treatment method:

1. Determine Tg to see if there is any poor hardening phenomenon.

2. Confirm the actual temperature inside the oven.

3. Check whether the temperature inside the oven is uniform.

4. Lower the initial baking temperature and extend the initial baking time.

2. Abnormality caused by poor stirring

Phenomenon: The colloid on the same surface is partially colored or the measured Tg and gelation time are different.

Cause: During stirring, the wall surface and bottom dead corners of the stirring container were not stirred evenly.

Treatment method:

1. Stir again.

2、升高A胶预热温度，藉以降低混合粘度。

3. Vacuum degassing bubble residue

Phenomenon: Bubbles continue to be generated during vacuum degassing.

reason:

1. The resin and hardener are preheated too high, resulting in continuous volatilization of the hardener during the bubbling process.

2. The bubbles that enter the injection molded object after viscosity increase are difficult to degas.

Treatment method:

1. Reduce the resin preheating temperature to 50~80℃, and maintain the bubble temperature at 50℃.

2. The hardener is not preheated.

4. Abnormal occurrence of colorants

Phenomenon: After using the same batch or the same can of colorant, there will be color difference and some cracks in the colloid.

reason:

1. Crystallization occurs in the colorant.

2. Uneven concentration leads to crystallization and sedimentation.

Treatment method:

According to the supplier's recommendations, different colors were given different pre-treatment temperatures and stirred evenly.

5. Abnormalities caused by moisture absorption of hardener

Phenomenon:

1. There are floating or sinking insoluble substances.

2. Opaque to milky white.

reason:

1. The hardener will turn into white crystals after hydrolysis.

2. Leave it for a long time after use.

3. The bottle cap is not locked tightly.

Treatment method:

1. Check whether there is any hydrolysis before use.

2. Anti-moisture measures.

Specific reaction process:

The normal colloid reaction process when B glue does not absorb moisture:

B glue hardener hygroscopic hydrolysis process:

After absorbing moisture, the hardener of glue B reacts with glue A. The reaction performance is poor, which reduces the mechanical and optical properties of the material:

6. Discoloration during long-bake hardening

Phenomenon: After being removed from the mold by short baking, there will be discoloration during long baking and hardening.

reason:

1. The temperature distribution in the oven is uneven.

2. The hardening materials are placed too close together in the oven. In addition to the reaction heat generated by the colloid, uneven heat convection may also cause it.

Treatment method:

Confirm the distribution location and quantity of hardened materials in the oven and the effect of oven heat circulation.

7. Poor quality of release from the mold after initial baking

Phenomenon: Difficult to release from the mold.

reason:

1. Moulding quality.

2. The initial baking hardening is incomplete and the hardening rate is too fast.

3. The mold machine is offset.

Treatment method:

1. Confirm the curing temperature and check the gelling time.

2. Make sure the demoulding machine maintains vertical demoulding.

Phenomenon: After leaving the mold, the surface of the colloid becomes atomized.

reason:

1. Excessive use of release agent.

2. The mold strip is used too many times.

3. Before spraying the demoulding agent, the temperature of the mold strip is too low.

Treatment method:

1. Adjust the amount of release agent used.

2. Pay attention to the number of times the mold strip is used.

8. Hardener discoloration

Phenomenon: The hardener turns yellow-brown.

reason:

1. Caused by thermal oxidation.

2. Caused by oxidation by UV-VIS light.

3. The hardener is left for a long time or in a high temperature place.

Treatment method:

1. The hardener cannot be preheated.

2. Keep in a dark place.

9. Solidification of diffusant

Phenomenon: No fluidity, solid shape.

Reason: After adding inorganic substances, the resin becomes solid.

Treatment method: Heat to melt.

10. Bracket Climbing

Phenomenon: The bracket cannot be tinned when it is glued or passed through the tin furnace.

Cause: The surface of the bracket is uneven, causing capillary phenomena, or it contains release agent.

Treatment method:

1. Confirm the quality of the bracket.

2. Use glue or thinner with low VOC content.

3. Use external spray glue.

11. There are bubbles on the rack after the initial baking

Phenomenon: Bubbles occur continuously around the support in the hardened material.

Cause: The bracket is stored in a place with high humidity, and the operating environment humidity is high.

Treatment method: Pay attention to the humidity of the operating environment.