Printed circuit boards have developed from single-layer to double-sided, multilayer, and flexible boards. And continue migration toward highly precise, high density, and high-reliability features. Parallel with shrinking size, reducing cost, and improving performance, printed circuit boards still maintain a strong vitality in the development of electronic products in the future.
From the 1950s to the 1990s, the PCB industry was founded and grew rapidly, that is, the early stage of PCB industrialization, when PCB became a separate industry.
In the 1950s, transistors were used in electronic devices, which helped to effectively reduce the size of electronic products and made it easier to integrate PCBs. In addition, engineers have made significant progress in improving the electronic reliability of PCBs.
In 1953, Motorola developed a double-sided board with plated vias. Around 1955, Toshiba of Japan introduced the technology to generate copper oxide on the surface of copper foil, and copper-clad laminates (CCLs) appeared. Thanks to these two technologies, multilayer circuit boards were invented successfully and applied on a large scale.
In the 1960s, printed circuit boards were widely used, PCB technology became increasingly advanced, and due to the widespread use of multilayer printed circuit boards, the ratio of wiring to substrate area was effectively increased.
In the 1970s, multilayer PCBs developed rapidly, pursuing higher precision and density, fine-line holes, high reliability, lower cost, and automated production. At that time, PCB design work was still done by hand. PCB Layout engineers use colored pencils and a ruler to draw circuits on clear mylar. They made several packaging and circuit templates for some common devices to improve drawing efficiency.
In the 1980s, Surface Mount Technology (SMT) gradually replaced through-hole mounting technology as the mainstream. It also entered the digital age.
With the evolution of electronic devices such as personal computers, CDs, cameras, game consoles, etc., correspondingly have changed considerably. The size of the PCB must be reduced to accommodate these small electronic devices. Computerized design automates multiple steps of PCB design and makes designing small and light components easier. Regarding component suppliers, they also need to improve their equipment by reducing power consumption, but at the same time, they need to consider the issue of cost reduction.
In the 2000s, PCBs became more complex, functional, and smaller. Especially multilayer and flexible circuit PCB designs made these electronic devices more maneuverable and functional, with small size and low-cost PCB. The advent of smartphones boosted the development of HDI PCB technology. While retaining laser-drilled microvias, stacked vias began to replace interleaved vias, and combined with “any layer” construction techniques, HDI boards resulted in final line widths/lines. The distance reaches 40μm.
This arbitrary-layer approach is still based on a subtractive process, and it is certain that for mobile electronics, most high-end HDIs are still using this technology. However, in 2017, HDI entered a new development phase, shifting from subtractive processes to Processes based on pattern plating.