Introduction of some knowledge about silicon nitride sheet
Silicon nitride plate is a heat dissipation substrate for high-power devices and LED high-power packaging. It is based on the high thermal conductivity of silicon nitride plate, which can reach more than 170 watts, which is more than 5 times that of alumina ceramic substrate and 100 times that of ordinary PCB. It far exceeds the heat dissipation capacity of copper substrate, aluminum substrate and PCB.
The silicon nitride sheet is metallized by the silicon nitride sheet for better thermal conductivity.
Silicon nitride plates are processed from silicon nitride plates. After surface treatment such as copper plating, silver plating, gold deposition and silver deposition, the thermal conductivity is stronger and therefore has better electrical properties. Since the silicon nitride plate is made of a ceramic substrate and the crystal is AIN, its hardness is higher than that of alumina, and it is thermally conductive and insulating. It is a "hot cake" in the field of heat dissipation.
More and more high-power devices, modules and LED packages are switching to silicon nitride sheets.
As far as LED packaging is concerned, in the past, the production process of ceramic boards was immature, and the cost was very expensive, which could not keep up with market demand, so metal substrates such as copper substrates and aluminum substrates had to be used for heat dissipation. Aluminum substrate or copper substrate is used for heat dissipation. Due to insufficient thermal conductivity, it is easy to cause a lot of heat and heat, and it is easy to burn out the circuit, resulting in abnormal operation of the device. Aluminum nitride ceramic heat dissipation substrate has high thermal conductivity, low expansion coefficient, dielectric loss and insulating material, which can make the device work for a long time with less loss and maintenance pressure.
It can be seen that the silicon nitride plate is a good heat dissipation substrate. Although the manufacturing cost is high, the overall performance is stable. In the long run, using a silicon nitride plate for heat dissipation is a wise choice. Silicon nitride sheet adopts mature thin film circuit technology or AMB technology, which can realize precision circuit, solid copper hole filling and damming. In addition to surface treatments such as gold deposition, silver deposition, copper plating, and copper plating, it can also be made with gold-tin alloys and platinum.
When silicon nitride plate manufacturers package ceramics and metals, they must first complete the metal packaging structure through design. So, how is the ceramic metal package structure designed? What are the design principles?
1. The primary expansion coefficient of metal parts and ceramic parts inoculated with ceramic metal seals should be the same or close, and the difference between the room temperature and the welding temperature should be within 7% to 10%.
2. The principle of low elastic modulus and low yield limit. In mismatched seals, a low modulus of elasticity should be chosen due to large differences in thermal expansion. Metallic materials with low yield limit are listed as oxygen-free copper as parts.
3. Since the tensile strength of ceramics is about one-tenth of the compressive strength, it is necessary to stress the ceramics as much as possible when designing sealing parts. For example, for stainless steel with high strength and high coefficient of linear expansion, the sheath seal structure should be adopted.
4. The thermal conductivity is close to the principle. When choosing the matching material, the thermal conductivity of the two materials should be close, which is beneficial to the thermal stress of the small sealing parts.
5. Stress reduction principle Under the premise of ensuring sufficient strength of the butt joint, the metal thickness on the sealing surface should be reduced as much as possible to release part of the pressure. For example, the metal thickness on the sealing surface is usually 0.5 ~ 1.0 mm, and the tubular thin tube is better than a strong needle.