Learn zirconia application in LED packaging

Light emitting diode (LED) has gradually replaced incandescent lamp and fluorescent lamp as a new generation of lighting source due to its characteristics of environmental protection, energy saving, high efficiency, stability and low cost.

LED packaging  

As a downstream industry, LED packaging is the only way to practical and market industrialization of LED.  The LED chip is placed on the heat sink of the plastic shell and sealed in the package to protect the chip and complete the electrical interconnection.  The main objectives of LED packaging are:  

1. Protect the chip from oxygen, moisture, radiation and other effects;  

2. Support wire, realize the input electrical signal;  

3. Prevent components from mechanical vibration and impact damage;  

4. Timely and effective heat dissipation, improve LED performance;

5. Packaging design and optical layout optimization according to different application requirements;  

6. Add phosphor powder to the packaging material as a color conversion layer to improve the light extraction efficiency.

Packaging materials  

Encapsulation materials as an integral part of the LED, the LED chips have the effect of protection and sealing, from environmental humidity or temperature, ensure the normal work, improve the device is practical, and heat conduction chip, help the heat dissipation, and can be reduced by LED encapsulation materials and refractive index of air gap and increase the optical output.  

For this purpose, packaging materials must have high refractive index (RI), high light transmittance, high thermal conductivity and good heat resistance.  Commonly used LED packaging materials include epoxy, silicone, polycarbonate (PC) and polymethyl methacrylate (PMMA).  Among them, PC and PMMA are used as outer lens materials, epoxy resin and silicone resin are mainly used as packaging materials, but also can be used as lens materials.  At present, epoxy resin and silicone resin are widely used in LED packaging field.  

Zirconia application in packaging  

At present, the simple resin material can not meet the requirements of LED packaging.  In recent years, nanoparticles (titanium dioxide, zirconia, zinc oxide, silicon dioxide, etc.) with excellent physical and chemical properties have attracted extensive attention.  Introduction of nanoparticles into organic polymers can effectively improve their optical properties, mechanical properties and thermal stability. The performance of polymer matrix composites depends on the size, shape, concentration of nanoparticles and the interaction between nanoparticles and polymers.  

Zirconia (ZrO2) has unique properties, such as high refractive index, high hardness, high chemical stability and thermal stability, and low absorption and dispersion in the visible and near infrared spectral regions, so it is widely used in optics, sensing, catalysis and other fields, often used in the preparation of organic-inorganic nanocomposites.  Yufeng Huang prepared high-performance zirconia/organosilicon nanocomposites for LED packaging by blending method and sol-gel method.  The results show that the organosilicon doped with zirconia has excellent performance, which improves the applicability of organosilicon resin in the field of high-power LED packaging.  Ochi et al. obtained epoxy/zirconia hybrid materials by in-situ polymerization of bisphenol A diglycidyl ether, zirconium n-propanol and hexahydrophthalic anhydride (HHPA).  The ZrO2 particle size of the nanocomposites prepared by this method is not more than 10nm, and the transmittance is more than 80% in the visible light range. The material RI increases from 1.542 to 1.599 when the amount of nano-particles increases from 0% to 20%.  

In addition, in the LED packaging substrate materials, ZTA (zirconia toughening alumina substrates by doping the alumina ceramic improves the reliability of zirconium, corrosion resistance, good chemical stability, high fracture toughness and bending strength, high temperature resistant ability, high current carrying capacity, high voltage insulation, high heat capacity and thermal diffusion capacity and the coefficient of thermal expansion (CTE) with similar silicon,  Make it become DBC copper cladding and LED circuit board urgently needed high-performance ceramic material circuit carrier.