History of Printed Circuit Boards

The history of Printed Circuit Boards (PCBs) is a fascinating story that traces back to the beginnings of electronics, encompassing innovations that fundamentally changed the way electronic devices are manufactured. In an era when most electronic components were of significant size, a method of connecting these parts had to be developed, leading to the technologies we use today to manufacture printed circuit boards.

The First Steps Towards PCBs: Metal Strips and Wires

As early as the 1850s, long before the advent of modern circuit boards, simple technological methods were used to connect electronic components. At this time, components were large and their connections were made using metal strips or wires attached to wooden or metal boards. Initially, wooden boards were replaced by metal chassis, which allowed for more stable and durable constructions. Although this technology was quite primitive, it was sufficient for the first experiments with electronic circuits.

The First Step Toward "Printed Circuits"

The true history of printed circuit boards, as we know them today, began in 1925 when Charles Ducas patented a method of printing conductive material onto an insulating substrate using a printing die. This invention laid the foundation for the future development of printed circuits, which began to be produced in larger quantities in the 1930s. During this time, terms such as "printed circuits" or the abbreviation "PCBs" emerged, becoming synonymous with modern printed circuit boards. Although the technology of the time had several drawbacks, such as low conductivity, these early attempts laid the groundwork for future developments.

The First True PCBs: Paul Eisler and Copper Etching

In the 1930s, a technology was developed that allowed the creation of copper connections on an insulating substrate. In 1943, Paul Eisler patented the method of etching copper foil, which was used for the first mass-produced printed circuit boards. His groundbreaking invention found applications in radio manufacturing, where the PCB technology we recognize today was first introduced.

The Development of Transistors and Integrated Circuits

With the arrival of transistors and the onset of miniaturization of electronic components in the 1950s, new technologies for connecting smaller and smaller components quickly emerged. As transistors and other components became smaller, there was a need to develop new methods for connecting them on the board. In 1957, Jack Kilby from Texas Instruments introduced the first integrated circuit (IC), a breakthrough moment in electronics history.
This transition to miniaturized circuits required new methods of connection—one key technology was the use of wire bonding and paste soldering into holes in the board. However, these methods were relatively challenging and not always efficient, especially with increasing component density.

Innovations: Hole Plating and Multilayer Boards

In 1961, the American company Hazeltyne patented the technology for hole plating, which led to a new development in printed circuit board technology. This technology allowed the internal layers of multilayer boards to be interconnected, which was crucial for higher-density connections and enabled the creation of boards with far more components in a smaller area.
Thus, multilayer printed circuit boards (multilayer PCBs) were born, consisting of several layers of insulating material and conductive layers, with interconnections made through plated holes between the layers. This development significantly improved circuit integration density and laid the foundation for more complex electronic devices.

Surface Mount Technology (SMT)

As components continued to shrink and miniaturization progressed, Surface Mount Technology (SMT) became essential for accelerating production and reducing device size. In SMT, components are not inserted through holes in the board but instead mounted directly onto the surface of the board using solder paste. This technology allowed for smaller component packages and enabled components to be mounted on both sides of the board. It significantly sped up production and reduced costs.

The Beginning of PCB Manufacturing in Czechoslovakia

The history of PCB manufacturing in the former Czechoslovakia dates back to the 1950s when the first attempts at introducing mass PCB production were made, specifically at Tesla Prelouc. The first printed circuit boards were produced for the transistor receiver T 58.
Initially, the boards were single-sided, but over time, a two-sided version with plated holes was developed. Following this, the production of multilayer boards and flexible circuits was introduced. A significant role in this development was played by the collaboration between engineers from Tesla Přelouč and the Tesla Research Institute of Telecommunications A.S. Popova Prague.

Challenges in the Early Stages

The early days of PCB production in Czechoslovakia were difficult. At that time, there were very few resources and technical literature available, and the methodology was not yet fully established. Nevertheless, the workers at Tesla Prelouc demonstrated determination and enthusiasm, which allowed the production of printed circuit boards to begin in Czechoslovakia. The first screen for PCB production was created, and a hand-built rotating drum for etching with ferric chloride laid the foundation for a new production technology.
This progress led to the introduction of the screen-printing method, which was replaced in 1960 with etching in tanks, allowing production to increase from 30,000 to 100,000 units per month. Simultaneously, the regeneration of ferric chloride was introduced.

Further Technological Developments

In 1961, a new method based on Diazolit Resist boards with photoemulsion, developed by Novoborska Machinery, was added to the screen-printing technology. This process, used for the production of channel coils, became the precursor to modern photographic PCB manufacturing methods known as the photo process.
Another significant development involved the progress in connector plating with hard gold and the introduction of new technological procedures.

Technological Advancements in 1970s

In 1970, Tesla Prelouc achieved a major technological breakthrough by introducing hole plating, pilot production of multilayer boards, and the production of flexible circuits. This enabled the manufacturing of boards with plated holes using the so-called metal resist method, made possible by a license acquired for the production of TESLA 200 computers. In 1982, the construction of a new production hall began, dedicated to the production of multilayer boards with a capacity of up to 21,000 m². This capacity also included the production of wire PCBs, developed in cooperation with VUMS Prague and Aritma Prague.

By the late 1980s, Tesla Prelouc had become the largest manufacturer of printed circuit boards in the former Czechoslovakia. By 1988, approximately 390 employees were working in the PCB production technology. In 1973, the PCB Expert Council was established, which brought together over 40 organizations focused on the production, development, and research of PCBs and materials for their production. The Council coordinated technological, standardization, and material issues until its dissolution in 1991.

Microvias and Miniaturization

Another significant step in global PCB manufacturing technology was the reduction of via hole diameters, which allowed for even greater miniaturization of the boards. New technologies, such as laser drilling for microvias, enabled the production of boards with much smaller dimensions and higher connection density. Over time, technologies for directly mounting silicon chips on boards also emerged, leading to further reductions in size and improvements in performance.

PCBs as Active Elements

Today, printed circuit boards are no longer just passive carriers of connections; they have become active components in the entire electronic system. Due to the increasing complexity of signals and demands for high-frequency signal transmission, the quality of PCBs has become a critical factor for the performance of devices. PCB manufacturing must now involve not only connection accuracy but also the optimization of impedances and other electrical properties of the connections.

Conclusion

The history of printed circuit boards is an example of continuous technological advancement accompanying the development of electronics. From the earliest experiments with metal strips to the complex multilayer boards with microvias, PCB technology has undergone a long journey, enabling the realization of ever smaller, more powerful, and more complex electronic devices. The historical era of Czechoslovak PCB production was crucial not only for domestic electronics but also for export markets and laid the foundation for the development of modern PCB manufacturing as we know it today.
With increasing miniaturization and circuit density, PCBs have become an indispensable element in modern electronic systems that define our technological future.