Device Development History
Ultrafast Electron Devices (1) – Development of Hybrid ICs
This issue features the story of Anritsu's high-speed electronic device product development.
The words IC/LSI are usually associated with CPUs and memory used in personal computers and smartphones. These integrated circuits consist of a monolithic circuit on a semiconductor substrate, and the scale of integration and production volume is very large. In contrast, hybrid ICs integrate the circuits of specific electronic devices. The small integration scale allows for a short development period, and the resistors, capacitors, and electronic components can be mounted on an insulated substrate to constitute a single unit. It is suitable for high-mix, low-volume production, and is expected to provide small, high-density mounting, optimized characteristics, reduced manufacturing costs, and improved quality. It can be used in fields requiring high precision, high frequency, high withstand voltage, and high power, which are difficult to achieve with monolithic ICs. Hybrid ICs are classified into thin-film and thick-film types according to the thickness of the film parts to be formed.
1. Thick-film Hybrid ICs
Conductors and resistors are formed on ceramic substrates using screen printing technology, and after high-temperature sintering, active components, such as transistors and ICs, are mounted. This process provides a stable and uniform resistive film, which can be fine-tuned by laser trimming.
In 1968, our research department began studying introduction of the technology, and a pilot plant was completed in 1970. The first step was to attempt mass-production of thick-film coaxial attenuators. Creation of high-precision, stable resistive films, and patterning techniques were mastered, leading to development of thick-film hybrid ICs. We developed oscillators and synchronous circuits for tele-controllers in 1970 and hybrid ICs for maritime communications equipment in 1975, which contributed to in-house needs. We began selling our products outside the company in 1976. Downsizing has also been achieved through using multilayer boards and double-sided mounting. Introduction of function trimming to absorb differences in semiconductor and peripheral-circuit characteristics supports non-adjustment and higher equipment precision. Since there were no PCs in those days, it took a long time to create and trace the layout of parts from circuit drawings on paper. Manufacturing also required a lot of patience, because the small electronic components had to be arranged one-by-one using tweezers. Production was scaled-up with use of products for in-house measuring instruments, reaching the scale of mass production at group companies in Japan.
Subsequently, the mounting density on printed-circuit boards has increased, and the need for thick-film hybrid IC products has decreased except for special applications, such as secrecy. We switched from in-house production to outsourcing due to aging equipment and declining demand, and eventually integrated our resources into thin-film products, which are high precision and suitable for high-frequency applications. Production and sales of thick-film products was discontinued around 2000.
2. Thin-film Hybrid ICs
Active components are mounted after forming conductor and resistor films by vacuum evaporation or sputtering on a ceramic substrate with a circuit pattern created by a photomask. MMICs* are often used as bare chips connected using gold wire and are suitable for high-frequency circuits due to the short wiring and precise patterning. Thin-film products tend to require a larger capital investment than thick-film products but have superior accuracy and characteristics.
*MMIC: Monolithic microwave integrated circuits. An integrated circuit in which microwave circuits are integrated on a semiconductor substrate by fine processing.
We started by manufacturing in-house resistive attenuators for use in waveguides for microwave test equipment. Prototyping started with a nichrome alloy film vapor-deposited on a mica substrate and production began in 1972 with a coaxial attenuator, which was used in a 1-GHz amplifier for a frequency counter in 1973 as well as in a 2-Gbit/s pulse pattern generator in 1975. Eleven different thin-film hybrid ICs were installed in a Microwave Radio Transmitter (MRTS) for AT&T in 1979, which became a key device with its excellent characteristics for high-frequency testing. The number of models incorporating this device, such as the signal quality analyzer and BERTWave, continues to expand. Several ICs are usually used in each test instrument in recent years, and the production volume continues to increase every year. When there were no automated machines, the entire manufacturing process consisted of manual operations. As shown above, IC chips and packages are connected using gold wires and ribbons, but since the wiring affects the product characteristics and many wires are needed, it is a delicate process requiring skilled workers. Craftsmanship is necessary at each process and making high-frequency products sometimes feels like craftwork rather than industrial production. The Group company in charge of manufacturing operated temporarily at full capacity as the main plant for devices, such as relays and thick- and thin-film hybrid ICs, but it was hard for personnel, equipment, and parts to travel back and forth between Atsugi and the factory each time problems occurred during full production, so resources were eventually consolidated at the Atsugi head office.