General characteristics of alumina ceramic substrates
An essential substrate material utilized extensively in RF microwave devices is alumina ceramic substrates. Their high dielectric constant helps circuits to be small-sized possible. Their strength and chemical stability are stronger than those of most other oxide materials; they also have great thermal stability and minor temperature drift properties. These properties enable alumina ceramic substrates to operate well in thin film circuits, hybrid circuits, microwave component modules, thin film circuits, thin film circuits, thin film
Capabilities for precision processing of alumina ceramic substrates
Based on thin film lithography, alumina ceramic substrates may be precisely processed in circuits; their micron level of accuracy is really remarkable. The intended device size is lower as the dielectric constant of alumina ceramic substrates is greater than that of conventional PCB substrates; this has major benefits in the development trend of shrinking of different component modules. Furthermore fulfilling the requirement for high-performance circuits and playing a significant part in the microwave RF area are alumina ceramic substrates.
Variations in alumina ceramic substrate performance based on purities
Alumina ceramic substrates split into 90, 96, 99, and other models depending on their purity. The key distinction is the varying substrate doping levels. The purity of the substrate increases with decreasing doping level. Electrical and mechanical characteristics of alumina ceramic substrates varying in purity differ. The dielectric constant increases with increasing alumina ceramic substrate purity; the dielectric loss decreases and the substrate's smoothness improves.
The dielectric constant of an alumina ceramic substrate with a purity of 99.6% is 9.9, for instance, at a frequency of 1MHz; the dielectric constant of an alumina ceramic substrate with a purity of 96% is 9.6. Even if the two dielectric constants vary by a few tenths, this is already a major mistake in microwave RF design. Devices manufactured using 99 ceramic and 96 ceramic might exhibit qualitative variations in electrical characteristics depending on the little change in dielectric constant. Usually speaking, the alumina ceramic substrate's price increases with increasing purity.
Thin film microstrip circuit use of alumina ceramic substrates
Using an alumina ceramic substrate, the gold layer of the thin film microstrip circuit built may reach 3.5um and be coupled to the external circuit by gold wire bonding. Common plate thicknesses include 0.127mm, 0.254mm, 0.381mm, and 0.508mm; their transmission frequencies may reach beyond 40GHz, therefore fulfilling the frequency range criteria of most microwave RF component modules. Thin film technique generates thin film circuit line precision of ±5um. Microstrip transmissions lines or very precise circuit designs are made from alumina ceramic substrates often used in the microwave RF area.
Design and thin film filter application
Widely employed as functional units for frequency selection in many microwave component modules and systems, thin film filters composed of alumina ceramic substrates may reach up to 40GHz. Thin film technology processes thin films; sputtering, photolithography, wet or dry etching, cleaning, and scribing generates the substrates. Alumina ceramic substrates may guide design of common filter designs including interdigital, hairpin, comb, parallel coupled line, and C-type. The thin film filters created have excellent electrical parameter indicators as their dielectric constant is greater than that of typical PCB substrates.
Precision production of thin film loading
Terminal matching of microwave circuit modules to absorb extra reflected power frequently uses the thin film loads made on alumina ceramic substrates. The processing correctness of the resistance value is really crucial for the load. The performance suffers more the more deviates there are. A high-precision thin film load may be generated from the controlled square resistance of the Tantalum Nitride Film Layer in the thin film process; the volume is extremely tiny, which is appropriate for the needs of the component module.
Uses and functions of thin film equalizers
Broadband power flatness correction of microwave circuits makes extensive use of thin film equalizers made of alumina ceramic substrates. The output waveform of the device is adjusted to get the balance of the power signal by varying the square resistance of the integrated tantalum nitride film layer and designing various resistance values in the graphic.
Design benefits of thin film power dividers
Multi-channel communication network systems employ thin film power dividers built with alumina ceramic substrates to distribute power depending on a specified percentage, one input and many outputs. Avoiding the issues of chip resistor welding and resistance instability in the microstrip power divider, the tantalum nitride film layer can be designed with a suitable resistance value and integrated in the thin film circuit and is easily realized multi-order ultra-wideband design, small size and good performance.
Attractive qualities of thin film attenuators
Large signal attenuation in microwave RF component modules or multi-speed adjustment in programmable attenuation circuits may employ thin film attenuators built with alumina ceramic substrates. In ultra-wideband, the thin film attenuator achieves high attenuation flatness and stable performance based on the suitable design of Tantalum nitride film layer and the thin film method of alumina ceramic circuit.
Design and implementation of a thin film coupler
In microwave component systems, the thin film coupler made of alumina ceramic substrate is utilized for signal separation or power sensing. Any weak coupling degree may be employed in design; integrated isolation loads can be created from tantalum nitride. One may build the port as a surface mount package and straight-weld in the circuit.
Uses of thin film bridges and resistors
Often employed to isolate signals and provide a phase difference of 90° or 180°, the thin film bridge built on alumina ceramic substrate is often called 3dB bridge. One of its most often utilized forms is a Lange bridge, and gold wire bonding achieves signal connectivity. Simultaneously, low-noise, high-stability, high-precision circuits make extensive use of thin film resistors built on alumina ceramic substrates. Usually, they are included into microstrip thin film circuits. Additionally configured into resistor networks or thin film resistors of different resistance kinds, their necessary resistance values are determined by gold wire bonding.
Stability of capacitors made of films
High-frequency filtering uses alumina ceramic substrates for construction of film capacitors. Any capacitance may be used in design for circuit application using film capacitors. Fit for high-frequency circuits, the performance is more constant than that of ordinary chip capacitors.
alumina ceramic substrates: development trend
Although some local producers are creating domestic alumina ceramic substrates as an alternative, the need for alumina ceramic substrates in my nation mostly depends on imports. Although the production of domestic alumina ceramic substrates in my nation has quadrupled 2.5 times from 2012 to 2022 and has risen year by year in recent years, it still cannot completely satisfy the rising domestic demand. Alumina ceramic substrates will keep a strong market share for a long period in the future despite the fast expansion of the electronics sector.