I. Core Performance Requirements for Mini LED Encapsulation Adhesives

Optical Performance

• High Light Transmittance: Transmittance ≥ 95% at the visible light wavelength of 450nm to avoid luminous efficacy loss.
• High Refractive Index: Mainstream demand ranges from 1.50 to 1.55; for high-end scenarios, it can reach above 1.57 (achieved by adjusting phenyl content) to reduce photon escape loss.
• Light Aging Resistance: Pass anti-sulfuration and UV resistance tests to ensure no yellowing after long-term operation (e.g., transmittance attenuation ≤ 3% after the double 85 test).

Thermal Stability and Stress Compatibility

• Temperature Resistance Range: Withstand cyclic temperatures from -50℃ to 250℃ (reflow soldering temperature reaches 250℃); the Si-O bond backbone structure enhances thermal stability.
• Low Shrinkage Rate: Curing shrinkage rate < 0.5% to avoid squeezing chips and gold wires; silicone elastomers can absorb stress from temperature cycles.
• Thermal Conductivity and Heat Dissipation: Cooperate with high thermal conductivity substrates to reduce chip junction temperature (e.g., epoxy adhesive with thermal conductivity ≥ 0.3W/(m·K)).

Adhesion and Protection Capability

• Multi-Substrate Compatibility: Strong adhesion to PPA brackets, ceramic aluminum substrates, sapphire substrates, etc. (no penetration in red ink test).
• Environmental Tolerance: Pass reliability tests such as thermal shock (-40℃ to 125℃ cycles) and moisture resistance (1000h of double 85 test).

Process Compatibility

• Controllable Viscosity: Dam-and-fill processes require low viscosity (1800-2800cPs) for leveling; lens molding requires thixotropic viscosity to prevent slumping.
• Curing Efficiency: Support medium-temperature rapid curing (80℃×1h + 150℃×1h) to match mass production rhythms.

II. Mainstream Adhesive Types and Characteristic Comparison

III. Benchmark Products and Application Cases

Representatives of Innovative Materials

• Taihong Laser Debonding Adhesive: Adapts to Mini LED mass transfer processes; adhesiveness disappears upon laser irradiation, improving transfer yield.
• Hairong One-Step Encapsulation Adhesive: Replaces traditional inkjet processes, achieves both protection and optical regulation simultaneously, reducing comprehensive costs by 30%.

IV. Key Application Processes and Operational Points

Adhesive Mixing and Defoaming

• Mix strictly according to weight ratio (e.g., 1:1 for silicone, 3:1 for epoxy). It is recommended to use a vacuum centrifugal defoamer to eliminate bubbles (vacuum degree -0.095MPa).
• Use the mixed adhesive within the pot life (8h for silicone, 1h for epoxy) to avoid sudden viscosity increase.

Substrate Preprocessing

• Dry the substrate at 120℃ for 2h before potting to remove oil and moisture (moisture content > 0.1% is prone to bubble generation).
• Avoid sulfur-containing or amine-containing substances on the substrate (e.g., flux residues) to prevent curing inhibition.

Curing and Post-Processing

• Step curing is preferred: First shape at low temperature (80℃), then enhance performance at high temperature (150℃) to reduce internal stress.
• Store sealed after curing; avoid moisture absorption before reflow soldering (humidity > 60% may cause pad oxidation).

V. Technology Development Trends

1. High-Refractive-Index Hybridization: Push the refractive index to 1.8-2.0 by introducing sulfur elements (epithio groups) or nano-inorganic fillers to further improve luminous efficacy.
2. Process Integration: Develop integrated “dam-fill-lens” adhesives to reduce processes (e.g., DuPont solid film materials enable lamination encapsulation).
3. Environmental Friendliness and Low Cost: Optimize silicone synthesis processes to reduce phenyl monomer usage while maintaining high refractive index.
4. Smart Responsive Type: Develop temperature-sensitive and light-sensitive adhesives to adapt to dynamic optical regulation needs (e.g., adaptive dimming modules).