Learn this trick ,you can classify Ceramic PCB easily
2018-11-23 17:52Writer: qyadminReading:
In accordance with ceramic PCB fabrication methods, they can be classified into three categories: high-temperature co-fired ceramic PCB, low-temperature co-fired ceramic PCB and thick film ceramic PCB.
• High-Temperature Co-fired Ceramic (HTCC) PCB
As a traditional manufacturing method, high-temperature co-firing is achieved through mixing aluminum oxide and adhesive, plasticizer, lubricant and solvent, leading to raw ceramics by roll forming and curtain coating and implementing circuit tracing on refractory metals like tungsten and molybdenum. Then, it will enter high-temperature oven under 1600°C to 1700°C temperature and carry out baking for 32 to 48 hours after cutting and lamination. To stop tungsten and molybdenum from being oxidized in high temperature, baking should be done in reducing gas such as hydrogen or mixed gas.
Ceramic PCBs manufactured by high-temperature co-firing can be applied on small-scale boards, derived boards or carrier circuits. When it comes to large-scale boards, however, high-temperature co-fired ceramic PCBs are challenged due to their unsuitable shrinking tolerance, warpage and relatively high tracing resistance of refractory metals.
• Low-Temperature Co-fired Ceramic (LTCC) PCB
Low-temperature co-fired ceramic PCB is fabricated by mixing crystal glass, glass composite and non-glass with adhesive with sheet generated and circuit tracing will be implemented by gold paste with high conductivity. After being cut and accurately being formed, it will be placed into oxidizing gas oven at a temperature of 900°C for baking. Low-temperature co-fired ceramic PCB provides a pathway to precious metal paste for circuit tracing and PCB baking can be completed as long as slight improvement is made to thick film baking. Product precision and shrinking tolerance can be improved as well and further optimizations need to be implemented on mechanical intensity and thermal conductivity.
• Thick Film Ceramic PCB
Thick film gold paste and dielectric paste is repeatedly and alternately printed on ceramic base and goes through baking at a temperature below 1000°C. Although this type of fabrication technology is optimal to large-scale ceramic PCB manufacturing and features relatively high assembly base number, its application is limited due to high cost of gold that also stops solder paste from precipitation. As a result, multi-layer thick film copper circuit technology is developed, which is the most noticeable and popular ceramic PCBs. To prohibit copper from being oxidized, this type of ceramic PCB has to be baked in nitrogen gas, which is the key point of this technology. Furthermore, dielectric paste is generated in nitrogen gas depending on complex multi-layer interconnection structures, which is also a core technology.
Application Fields of Ceramic PCB
Ceramic PCBs are widely applied owing to their high thermal conductivity, low CTE, chemical erosion resistance and low dielectric constant.
• Memory Module
AGC company from Japan created 1Mbit SRAM memory module by taking advantage of multi-layer ceramic PCB containing 4 IC chips, contributing to high reliability and high density assembly. Vitarel company from the US created missile, telecommunication products and aerospace products with ceramic PCBs. The common feature all of them are sharing lies in the fact that they can be applied in extreme environment. At warhead, multi-layer ceramic PCB and packaging components on it perform sufficient intensity and shock vibration resistance capability.
• Receiving/Transmission Module
Westinghouse company from the US produced receiving/transmission module for radar with ceramic PCB. Aluminum nitride features high thermal conductivity and low CTE, laying solid foundation for the application of ceramic PCBs in receiving/transmission module.
• Multi-layer Interconnect Board
To be compatible with miniaturization of electronic products, ceramic PCBs are able to hold more components within the same board area, which adds more possibilities for ceramic PCBs in the applications of multi-layer interconnect board.
• Analog/Digital PCB
AGC company from Japan took advantage of LTCC PCBs to produce analog/digital PCB boards so that parasitic capacitance can be reduced by approximately nine tenths. It not only effectively overcomes crosstalk interference of circuit tracing, but also reduces volume and weight of circuit.