For LED packaging purposes, Japan's YOKOWO has developed a low-temperature co-fired ceramic (LTCC: Low Temperature Co-fired Ceramics) CSP substrate with high heat dissipation and high reflectivity and a thickness of 0.075~0.150mm. The electrode material uses silver (Ag) conductor. The inner layer of the LTCC substrate is equipped with a heat dissipation plate, and thousands of tiny CSPs are assembled together. The CSP and the front and back through holes are bonded with bonding pad processing on at least one of the front or back sides.
Generally, only 25% of the energy of high-brightness LEDs is converted into light, and the rest of the energy is converted into heat. The higher the temperature, the lower the luminous efficiency of LEDs, so users strongly demand to improve the heat dissipation of the package. Therefore, in high-current LEDs, considering the heat dissipation characteristics, more and more packaging substrates are using aluminum oxide substrates and aluminum nitride ceramic substrates.
However, due to the low reflectivity and dimensional accuracy of the alumina substrate, it lacks reliability when packaging LED chips. In addition, there is also the problem that the price of aluminum nitride substrates is very high. Therefore, Youhua has developed an LTCC substrate that has high heat dissipation characteristics, supports miniaturization and thinning, and helps reduce costs.
The outer peripheral edge of the LTCC substrate is equipped with an "outer frame" that is slightly thicker than the CSP part in an integrated structure, thereby improving the processing capability when packaging chips. In addition, a self-developed process is also used to greatly improve the bonding strength between the substrate and the equipped LED chip. Dimensional error is below ±0.15%. Surface treatment was implemented by electroplating nickel gold (Ni-Au).
The packaging substrate developed this time is currently undergoing sample evaluation by LED packaging manufacturers. Production is planned at the "Advanced Device Center" (Tomioka City, Gunma Prefecture), LTCC's development and production base. The new factory under construction in the center with a construction area of approximately 500m2 is scheduled to be completed by the end of May 2015. Youhua will arrange workshops in the new factory. According to reports, a production line will be built to produce 500,000 LTCC assembly substrates with a size of 50mm square per month. Each substrate is arranged with thousands of CSPs with a size of 1.0×1.0×0.15mm. Mass production is planned to begin in October 2015.
ANNA