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Printed Circuit Board (PCB) is honored by many as the mother of all electronic products, and it is a key component of electronic products. Throughout the brief history of PCB development, every technological advancement has directly or briefly affected all mankind. PCB is composed of interconnected electronic components of independent modules, from our side of the daily use of electronic equipment, such as: mobile phones, routers, personal computers to complex radar, missiles, satellites, can be found in their figures, but their beautiful light by the equipment casing to cover up your genius-like design is often overlooked by the user until the equipment malfunctions or need to expand functionality, open The moment you remove the shell of the equipment to appreciate its beauty.
The origin of electronics can be traced back to 1897, when Joseph Thomson discovered the existence of electrons, electronics is based on the early development of electromagnetism and electrical engineering. Before the birth of electronics, the phenomenon of electromagnetism had been studied in great depth. A series of physical laws had been established, such as Coulomb's law, Ampere's law, Ohm's law, Corrugator's law, Faraday's law of electromagnetic induction and so on.
On June 13, 1831, James Clerk Maxwell (June 13, 1831 - November 5, 1879) was born at 14 India Street, Edinburgh, England. Maxwell is generally regarded as one of the most influential of the nineteenth-century physicists in the great advances in physics at the beginning of the twentieth century. Maxwell is generally regarded as the most influential of the nineteenth-century physicists who contributed to the great advances in physics in the early twentieth century. In his paper “The Kinetic Theory of the Electromagnetic Field” published in 1864, he collected the great achievements of previous electromagnetic studies, proposed that the electric and magnetic fields propagate in space in the form of waves with the speed of light, and proposed that light is the electromagnetic disturbance that causes many phenomena in the electric and magnetic fields in the same medium, and at the same time theoretically predicted the existence of electromagnetic waves, and united the electricity, magnetism, and light as the phenomena in the electromagnetic field, put forward the famous Maxwell's system of equations, and established the first complete set of equations that can be used to predict the existence of the electric and magnetic fields. He proposed the famous Maxwell's equations and established the first complete theoretical system of electromagnetism, which laid a strong theoretical foundation for the application of electromagnetism in production and life.
Electromagnetism is the most important subject in modern science and technology, and its high-speed development has brought mankind into the era of electricity and information.It can be said that without the development of electromagnetism, there would be no human modern civilization. The results of this natural science theory have laid the foundation for the modern electric,electronic and radio industries. Of course, without Maxwell, there would be no PCB, there would be no PCB Layout industry, perhaps now the old wu or the village selling pork the most beautiful boy.
With the support of the theory of electromagnetism, the use of electromagnetism has reached a certain level, cable telegraph and cable telephone have been invented,and there is a transcontinental American telegraph, telephone lines and submarine cables across the Atlantic Ocean. Alexander Graham Bell's invention of the telephone in 1876, Thomas Edison's invention of the incandescent lamp in 1879,and Nikola Tesla's invention of the electric motor in 1888, all prepared the ground for the birth of electronics.
The two major historical events that marked the birth of electronics were the discovery of the Edison Effect and the experiments to verify the existence of electromagnetic waves.
In 1883,when Edison was working on extending the life of carbon incandescent lamps,he accidentally discovered that there was an electric current between the filament and the electrode with positive voltage, but no current when the electrode was negative, which was the Edison effect. This discovery led to the invention of the electron tube.
In 1887, H.R. Hertz of Germany conducted an experiment in which he used a spark gap to excite a ring antenna and another ring antenna with a gap to receive it,confirming Maxwell's prediction about the existence of electromagnetic waves, and this important experiment led to the invention of wireless telegraphy. The invention of wireless telegraphy is the first great achievement of human beings in utilizing electromagnetic waves, and electronics has since begun an extremely prosperous period of research and utilization of electromagnetic waves. Electromagnetic waves are the cornerstone of interconnection and communication between electronic components, and the invention of the electron tube gave birth to the PCB.
In 1897, the German scientist Braun produced the first vacuum tube, and the vacuum tube era of electronics began. Basically, Braun's vacuum tube was just a prototype Cathode Ray Tube (Cathode Ray Tube), which was not very functional.
In 1904, John Fleming of the United Kingdom invented the vacuum diode (diode, also known as valve), which consists of a heated filament that radiates electrons and a screen that receives them. When a positive voltage was added to the screen electrode, a current was generated; when a negative voltage was added, no current was generated.
By 1906, De Forest (De Forest) in the two-pole vacuum tube to add the gate pole, the invention of the three-pole vacuum tube (audion, or triode), you can control the activities of the electrons, so that it has to amplify the signal and control the power of the powerful function, and thus make the electronic circuit technology has entered the stage of practical application, but also to promote the development of the radio and other electronic industries, the next 20 years. This after 20 years, a variety of electronic devices continue to emerge, DeForest is also known as the father of radio “,” the originator of television “,” the father of the tube “.
The electron tube is the first generation of electronic devices, in nearly half a century before the invention of the transistor,the electron tube is almost the only available electronic devices in various electronic equipment. Many subsequent achievements in electronics,such as television,radar,computer invention, are inseparable from the electron tube.Even in the solid-state electronics is very prosperous in the modern era,to high-power tubes (especially microwave power tubes) and electron beam tubes as a representative of the vacuum electronics is still an active field.
Through the picture above we see that before the large-scale application of PCB technology, the production of such an electronic device is so troublesome and inefficient,a large number of electronic tubes, you need to use the wire coated with insulating resin in the device between the manual wiring and welding, which brings some problems: low efficiency of manual wiring, no way to realize the mechanization of large-scale production of manual wiring is prone to installation errors, checking the difficulties Terminal welding reliability is low, easy to loosen the contact caused by poor In order to simplify the production of electronic machines,reduce the wiring between electronic parts,reduce production costs, improve the reliability of electronic machines, people began to study the printed pipeline instead of wiring method,in order to use the machine to achieve precision large-scale production.
After Faraday published the law of electromagnetic induction in 1831, people began to study how to use the electromagnetic principle to realize long-distance communication. Samuel Morse invented the telegraph in 1837, and Bell obtained a patent for the invention of the telephone in 1876. By 1904 there were three million telephones in the United States connected by artificial telephone exchanges.
Printed Circuit Boards (PCBs) were developed along with electronic connection systems to solve the connection problems of the telegraph/telephone system. Initially, metal bars or rods were used to connect large electronic components mounted on wooden bases. Over time, the metal bars were replaced by screw terminals and cables that could be screwed into them to make the connection more flexible, and the wooden base was replaced by a metal backing plate. However, as the telegraph/telephone business grew, the increasing number of telephone exchanges and the complexity of the electronic operations associated with the telephone system required smaller, more compact designs.
In 1903, a famous German inventor by the name of Albert Hanson applied for a British patent for the first application of the concept of “wiring” to a telephone switching system, which utilized metal foil cut into wire conductors with paraffin paper glued to the top and bottom of the wire conductors to set the conduction at the intersections of the wires. Then, paraffin paper was glued on the top and bottom of the circuit conductors, and conduit holes were set on the intersection points of the circuits to realize the interconnection of electricity between different layers. There is a clear difference between this and our modern PCB manufacturing method, because phenol 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 PCB manufacturing.
In 1907, Leo Hendrik Baekeland (1863-1944), a Belgian-born American chemist, improved the production technology of phenolic resins, making them practical and industrialized. This created the necessary conditions for the introduction and development of printed circuit boards.
1920's - Early PCB boards were made of almost everything, from Bakelite (the phenolic resin mentioned above, commonly known as Bakelite) and turquoise to ordinary old thin wood boards. Holes can be drilled in the data and flat copper wire riveted to the data. The shape may not look very pretty, but this is where the idea of printed circuit boards was born. At the time, these boards were mainly used in radios and phonographs. After Hertz confirmed Maxwell's prediction about electromagnetic waves through experiments in 1887, by the 1920s, radio had attracted worldwide attention, and tube technology had matured to the extent that radio broadcasting could be started, and radio broadcasting would soon be introduced to every household.
In 1925, Charles Ducas of the United States printed wire patterns on insulated substrates,and then plated pipes to successfully establish conductors for wiring. At this time, the term “PCB” was born. This method made it easy to manufacture electrical devices.
In 1936, Dr. Paul Eisler, an Austrian, published his foil technology in the United Kingdom,where he used a printed circuit board in a radio device. Also in 1936, Kinnosuke Miyamoto of Japan successfully patented the spray-on wiring method. Of the two, Paul Eisler's method is the most similar to today's printed circuit boards, which are called subtractive, removing unwanted metal. Charles Ducas and Kiyonosuke Miyamoto's approach is to add only the required wiring, which is called the additive method. Paul Eisler is also known as the “father of the printed circuit”,but because of the large amount of heat generated by the electronic tube components at the time, bulky and heavy, not convenient for installation on the printed circuit board, Paul Eisler's major invention at the time was not emphasized by the United Kingdom, and in the United States is only the PCB manufacturing technology applied to military products. In the United States, PCB manufacturing technology was only applied to military products.
In 1942, Dr. Paul Eisler continued to refine his PCB production methods and invented the world's first practical double-sided PCB, which was formally manufactured at Pye. The patent application was granted in 1943.
In 1943, the U.S. began to utilize Paul Eisler's technology on a large scale for the manufacture of proximity fuses for use in World War II.The technology was also used extensively in military radios.
In 1947, epoxy resins were used in the manufacture of substrates.At the same time,NBS began researching the use of printed circuit technology to form coils, capacitors, resistors, and other manufacturing technologies.
In 1948, the U.S. officially recognized the invention of printed circuit boards for commercial use.
In 1950, there were very few electronic devices that used PCBs.For example, this 1948 Motorola TV still does not have a PCB. Goodness, it's full of electronic tubes, so it would have been a real challenge to repair it. If you had a working Motorola tube TV today, how much would it be worth?The people who could afford a TV in 1948 were rich. From the 1950s to the 1990s. This is the formation of the PCB industry and the rapid growth of the stage, that is, the early stage of PCB industrialization, at this time PCB has become an industry.
In 1948, the U.S. officially recognized the invention of PCB for commercial use, which also means that PCB from the military field of use to start the pace of large-scale commercial use.
In 1947, the U.S. Bell Labs, Shockley, Bardeen and Bratton research team developed a transistor, lower heat generation volume more compact transistor from the 50's began to replace a large number of the status of the electronic tube, which also creates the conditions for the widespread use of printed circuit board technology.
In 1950, Japanese companies experimented with coating glass substrates with silver as a conductor and using copper foil as a conductor on phenolic paper substrates. Etching played a leading role in the widespread acceptance of printed circuit manufacturing technology from 1950 onward. Along with the transistors began to be practical, with the metal foil etching method into a single-sided PCB in the United States developed successfully, and quickly industrialized applications.
In 1951, polyimide data was born.
In 1953, Motorola developed a double-sided PCB with electroplated vias. Around 1955, Toshiba of Japan introduced a technology to generate copper oxide on the surface of copper foil, and copper clad laminate (CCL) appeared. Both technologies were later widely used in the manufacture of multilayer printed circuit boards, and they contributed to the emergence of multilayer printed circuit boards. Since then, multi-layer PCBs have been widely used.
In 1958, Robert Noyce of Fairchild and Kilby of DEI invented integrated circuits a few months apart, starting the history of microelectronics in the world.
In 1960, multi-layer (4+ layers) PCBs began production. And electroplated through-hole metallized double-sided PCB to achieve mass production. In the 1960s, printed circuit boards (PCBs) were widely used. 10 years later, in the 1960s, PCB technology was becoming more and more sophisticated. Since the introduction of Motorola's double-sided PCBs, multi-layer PCBs began to appear, increasing the ratio of wiring to substrate area.
In 1964, Intel Moore proposed Moore's Law, predicting that transistor integration would increase by a factor of one every 18 months.
In 1971, Intel introduced 1kb Dynamic Random Memory (DRAM), signaling the emergence of large-scale integrated circuits.
In 1971, the world's first microprocessor, the 4004, was introduced by Intel, using the MOS process, a landmark invention. With the large-scale application of integrated circuits, the production of electronic products without the use of printed circuit boards, that production will bring trouble.
In the 1970s, the rapid development of multi-layer PCB, and continue to high-precision, high-density, fine-line small hole, high reliability, low cost and automated continuous production direction to adapt to the pace of Moore's Law. Although the rapid development of multi-layer PCBs began in the 1970s, the PCB design work at that time was still done manually.
At that time, PCB Layout engineers with colored pencils and rulers, drawing circuits on transparent polyester film sheets, in order to improve the efficiency of drawing, there will be some common device packaging templates and circuit templates.
In the 1980s, surface mount technology began to gradually replace through-hole mount technology into the mainstream, also began to enter the digital era, with the development of electronic devices such as personal computers, CD-ROMs, cameras, game consoles, Walkman, etc., so that we in the media consumption pipeline has undergone a huge change.
Microsoft released the MS-DOS 1.0 system in 1981, Apple released the Macintosh Macintosh computer (now known as Mac) in 1984, Lenovo was founded in 1984, began to assemble personal computers, personal computers began to become popular, based on the DOS CAD software began to appear and rapid development.
The emergence of CAD software to improve the efficiency of the designers drawing, but also to improve the PCB design of the reuse rate, saving time to repeat the design, PCB design is completed, directly exported Gerber file input to the optical drawing equipment, while the PCB manufacturing also began a large number of mechanical alternative to manual, PCB production efficiency, before the need for weeks to deliver the PCB is now the fastest! PCB production efficiency increases, before it takes weeks to deliver the PCB can now be delivered in a few hours at the earliest, at this time the PCB fast board factory began to appear.
In 1993, Paul T. Lin of Motorola applied for a patent called BGA (Ball Grid Array) package, which marks the beginning of the organic package substrate.
In 1995, Panasonic developed ALIVH (Arbitrary Layer Via Hole) structure of the BUM PCB manufacturing technology. This also meant that PCBs began to enter the HDI high-density interconnect era.
In the early 2000s, PCBs became smaller and more complex. 5-6 mil line width/space was the norm, and for high-end PCB manufacturers, 3.5-4.5 mil line width/space boards began to be manufactured. At the same time, flexible PCBs became more common. In 2006, the Every Layer Interconnect (ELIC) process was developed. This process uses stacks of copper-filled microvias to make connections through each layer of the board. This unique process allows developers to create stacked connections between any two layers in a PCB. Although this process increased the level of flexibility and allowed designers to maximize interconnect density, it wasn't until the 2010s that ELIC PCBs became widely used.
With the development of smartphones, the second generation of HDI was born in the early 21st century. While retaining laser-drilled microvias, stacked vias began to replace staggered vias, and combined with “any-layer” construction technology, HDI boards ultimately achieved 40 μm line width/space.
This arbitrary layer approach is still the basis for, and certainly still utilized in, most high-end HDI for mobile electronics. However, in 2017, HDI started to move into a new phase of development and began to shift away from the reduced-format process.
For example, in a 0.3mm pitch BGA design, two alignments are crossed between the BGA pads, with through-hole sizes typically at 75µm and pad sizes at 150µm. The layout design requires a line width/space of 30µm/30µm. Realizing this fine line structure with existing subtractive processes is challenging. Etchability is one of the key factors, where finished copper thickness and plating uniformity need to be optimized along with the imaging process. This is why the PCB industry is now adopting the mSAP process. Compared to subtractive processes, the mSAP process can easily produce traces with optimized conductor shapes, where the top width of the etched end face of the PCB is almost equal to the width of the bottom end of the entire PCB panel - the shape of the trace is easy to control. Another advantage of mSAP is that it utilizes existing resources and technology, adopts standard PCB processes such as drilling, plating, etc., and uses conventional data to provide good adhesion between copper and dielectric layers, ensuring high reliability of the final product.
The semi-additive process (mSAP) and modified semi-additive process (amSAP) are modified and advanced modified versions of what is now expected to be the predominantly used process for the next generation of HDI PCBs.
Due to miniaturization, HDI and microvias provide a huge boost to high density. These technologies will continue to evolve as the geometry of the IC cell continues to get smaller. So the next revolution will be in the field of optical conductors.
As the processor performance of computer systems improves with the continuous improvement of large-scale integrated circuits, but electronic computers still use traditional copper wires to realize the connection between the chip, processor processor, circuit boards and circuit boards, the International Transistor Technology Blue ITRS has already pointed out that future electronic systems will be limited by the interconnections between the chips.
This is because the main problems faced by the copper wires currently in use are:
1.High-speed signal distortion and limited bandwidth.
2.The transmission loss of metal wires increases as the signal frequency increases,limiting the transmission distance of high frequency signals.The transmission loss of metal wires increases with the increase of signal frequency, which limits the transmission distance of high-frequency signals.
3.It is susceptible to electromagnetic interference.
4.Optical communication has a lot of advantages that traditional electric signals do not have, such as high bandwidth, low loss, no crosstalk, anti-electromagnetic interference and so on. In fact, optical fiber has completely replaced the traditional copper wire used in long-distance communication for decades, the future development trend is that the communication distance of optical interconnection will gradually become shorter, from the long-distance communication between countries to the signal transmission within the chip in the future.
Nowadays, the industry generally believes that when the single-channel rate reaches Gb/s or above, electrical interconnections will face great challenges in terms of both technological realization and cost comparison. In order to overcome the “bottleneck” of electronic computers, it is necessary to change the traditional copper-based interconnection pipeline, the introduction of optical technology into the electronic system, with the new optical interconnection instead of the traditional electrical interconnection, in order to significantly increase the operating speed of computers and high-speed information and communication network development, and thus to meet the needs of the development of society.
Current situation of China's PCB industry
In the global PCB industry to Asia under the overall trend of transfer, China as a major electronic product manufacturing country,with a huge domestic market and relatively low production costs to attract a large number of foreign and local PCB enterprises to invest in promoting China's PCB industry in just a few years to show explosive growth.
Currently, China has become the world's largest PCB producer, and is also one of the regions in the world that can provide the largest PCB production capacity and the most complete product types. In 2021, the output value of China's PCB industry reached 44.2 billion U.S. dollars, with the deepening of the PCB industry transfer, the proportion of China's PCB output scale will be further enhanced.
