Study On Water Glass Based Heat Conduvtive Adhesive For High Power LED Packaging

To reduce the thermal resistance of high-power LED packaging, this paper investicates a insulate heat conductive adhesive, which is water glass based and filled with hexagonal sheet boron nitride. There are two types of BN(0.1-0.5μm, 5-10μm). This paper determines the concentration of the best adhesive strength by comparing different concentration of sodium silicate. This paper investigates the dispersion stability of BN in water glass and the composition of cured adhesives by XRD and FTIR. Combined with the DSC/TG curve, we determine the best cured temperature of water glass by comparing the adhesive strength of different concentration of water glass. Investigate the effect of BN content and size on the adhesive strength. Finally, this paper tests the heat conductivity and interface resistance of water glass based adhesive by Steady-State Heat Flow method and the Laser-Flash method.It was found that 40wt% water glass has the best adhesive strength 30MPa when cure at 80℃for 1.5 hours. Then the adhesion strength decreases with temperature and concentration increasing 0.1-0.5μmBN can react with water glass and release ammonia. Howere, 5-10μmBN can only react with it under heated conditions. Neither of the reactios can complete, because that reaction will stope when the surface of BN has been completely oxidated. Experimental results demonstrate that BN partical can disperse in water glass stability by maechanical stirring and ultrasonic vibrating under heated conditions. With the increase of BN content and size, the bonding strength of water glass decreases, while the thermal conductivity changes in contrast. Steady-state heat flow method test results for the 5-10μmBN show that thermal conductivity increases linearly with increasing concentration. When BN content is 30Phr thermal conductivity can be achieved 3.96W/m?K. For 0.1-0.5μmBN, thermal conductivity increases slowly after the concentration is more than 10Phr. when the content increases to 50PHR,the thermal conductivity can reaches 2.436W/m?K. Laser method test data show 30PhrBN (5-10μm) thermal conductivity is 4.852W/m?K, 30PhrBN(5-10μm) thermal conductivity is 2.639W/m?K. The water glass based adhesive has high thermal conductivity, stability and low cost advantages. Water glass adhesive can meet the heat dissipation requirements of LED packaging and has a certain applied prospects.