Important milestones in the development of printed circuit boards
PCB (Printed Circuit Board) is no longer unfamiliar to us. It is the core component of electronic equipment such as mobile phones, computers, radios, and lamps. Without the development of circuit boards, we would not be able to enjoy the convenience brought by these electronic devices. Various types of printed circuit boards, such as rigid PCBs, rigid-flex PCBs, multilayer PCBs, and high-density PCBs, are widely used in the market and have undergone many evolutions. Let’s have a look.
In 1903, Albert Hanson, a famous German inventor, applied for a British patent. He pioneered the concept of using “wires” in telephone switching systems, cutting line conductors with metal foil, pasting paraffin paper on the top and bottom of line conductors, and setting wires at intersections. Vias realize the electrical interconnection between different layers. This is different from our modern method of manufacturing printed circuit boards.
At that time, phenolic resin had not yet been invented, and chemical etching technology was not yet mature. The method invented by Albert Hansen can be said to be the prototype of modern circuit board manufacturing, laying the foundation for later development.
Development stage (1920s-1940s)
In 1925, Charles Ducas from the United States had an innovative idea of printing circuit patterns on an insulating substrate, and then electroplating to make conductors for wiring. It was at this time that the term “PCB” was coined, a method that made it easy to manufacture electrical appliances.
In 1936, Austrian Dr. Paul Eisler, known as the “Father of Printed Circuits”, published foil technology in the UK and developed the first printed circuit board for radios. The method used by Dr. Paul Eisler is very similar to what we use for printed circuit boards today. This method is called a subtractive process, and it removes unwanted metal parts.
Around 1943, Paul Eisler’s technological invention was widely used by the United States to manufacture proximity fuzes for World War II. At the same time, this technology was widely used in military radios.
Turning point (1948)
1948 was a turning point in the historical development of circuit boards. The United States officially recognized the invention of printed circuit boards for commercial use. At that time, there was very little history of using circuit boards in electronic equipment, but this decision greatly promoted the development and application of circuit boards.
Boom stage (1950s-1990s)
From the 1950s to the 1990s, the circuit board industry was formed and grew rapidly, that is, the initial stage of circuit board industrialization, and PCB has become an industry at this time. In the 1950s, the electronic market began to use transistors, which effectively reduced the size of electronic products and made it easier to integrate circuit boards. In addition, the reliability of electronic products was also significantly improved.
In 1953, Motorola developed a double layer PCB with plated vias. Around 1955, Japan’s Toshiba Corporation introduced a technology to generate copper oxide on the surface of copper foil, and copper clad laminates appeared. It is precisely because of these two technologies that multilayer PCB were successfully invented and applied on a large scale.
In the 1960s, printed circuit boards were widely used at this time, and circuit board technology became more and more advanced. Thanks to the widespread use of multilayer PCBs, the ratio of wiring to substrate area was effectively improved.
In the 1970s, multilayer PCB developed rapidly, pursuing higher precision and density, small holes, exquisite lines, high reliability, low cost and automated production. At that time, circuit board design work was still done manually. Circuit board design engineers use colored pencils and rulers to draw circuits on transparent polyester films. In order to improve drawing efficiency, they have made several package templates and circuit templates for some commonly used devices.
In the 1980s, surface mount technology gradually replaced through-hole mount technology and became the mainstream at that time, and circuit board technology also entered the digital age.
Maturity stage (1990s to present)
With the development of electronic equipment such as personal computers, CDs, cameras, and game consoles, great changes have taken place accordingly, and the size of circuit boards must be reduced to accommodate these small electronic equipment.
Digital board design automates many steps, making it easier to design small and lightweight components. As for component suppliers, they also need to improve their designs by reducing power consumption. At the same time, they also need to consider the issue of cost reduction.
In the 2000s, PCB became more and more complex, with more functions and smaller sizes. Especially multi-layer and flexible circuit board designs make these electronic devices more practical and practical, with small board size and lower cost.
At the beginning of the 21st century, the emergence of smart phones led to the development of high-density circuit board technology. While retaining laser-drilled micro-vias, stacked vias began to replace staggered vias, and combined with “arbitrary layer” construction technology, the final line width/line spacing of the high-density circuit board reaches 40 μm. This arbitrary layer approach is still based on a subtractive process, and it is safe to say that most high-end and high-density circuit boards still use this technology for mobile electronics.
However, in 2017, high-density circuit boards began to enter a new stage of development, and began to shift from the subtractive process to the pattern-based electroplating process.
Looking back on the development history, with the continuous advancement of science and technology, the circuit board industry is constantly updated and evolving, and the circuit board plays an important role in today’s era.
With the continuous emergence of electronic product applications in the consumer market, such as wearable electronic devices, electronic hearing aids, blood glucose meters, electric vehicle smart devices, aerospace and other fields, people have put forward higher requirements for the design, materials and manufacturing of circuit boards.