Printed circuit boards are a natural part of almost all modern electronic devices and therefore of Electronics Manufacturing Service (industrial electronics). It is impossible to imagine computers, printing devices, radio alarm clocks and the like without them. But what exactly are PCBs, how does PCB assembly work and how are they manufactured?#
Printed circuit boards, also called circuit boards or printed circuits, are the part of an electronic device to which the electronic components are attached. It is therefore a carrier element, without which the most diverse electronic devices would not function at all.
The circuit boards or printed circuit boards are made of a non-conductive material. They are used to mechanically fix the components of an electronic circuit and to pass on the electrical signals. The various components of an electronic circuit that are connected to the PCB as part of the PCB assembly process include transistors, circuits, resistors, capacitors and coils.
Untreated printed circuit boards consist of electrically insulating material on which there is usually a copper layer on the underside. Depending on the type of circuit board, the copper layer may also be on the top side. The components are soldered onto soldering surfaces or into so-called soldering eyes and thus simultaneously mechanically and electrically connected to the circuit board.
Usually the components are inserted into the holes in the board from one side only. However, some modern PCBs can also be assembled on both sides. If larger components are involved, these are sometimes also fastened with adhesive, cable ties or screw connections. Fiber-reinforced plastic is often used as the insulating material for the board, while hard paper is often used for less expensive devices.
A layout or PCB design specifies how the PCB is to be assembled, i.e. which components are to be plugged in where in order to connect them electrically to the copper conductors. This means that the design specifies which circuits, diodes or resistors go in which place so that the device will ultimately work.
Whether it’s a household appliance or an entertainment system, the electronics are crucial for the function of the respective devices. At the heart of these electronics is always a printed circuit board. Printed circuit boards are used in mobile devices – for example tablets and notebooks, smartphones and smart watches -, in industrial electronics – for example process control and sensor technology – and in the automotive sector – for example transmission control and camera and safety systems. There, printed circuit boards also play a major role as industrial spare parts. However, they also find applications in the healthcare industry and medical technology, for example in pacemakers or hearing aids.
Depending on the complexity of the requirement, the demands on the electronic circuits and PCB assembly also increase. This means that components must become smaller and smaller in order to drive powerful, compact devices.
THT circuit boards (through hole technology) are circuit boards in electronic devices that consist of material laminated on one side and wired components. As through-hole components, these PCBs can only be assembled at the top.
The so-called SMD circuit boards (Surface Mounted Device) are considered to be more modern. These emerged with the advancing miniaturization and have a mountable top and bottom side. In addition, the components of SMD PCBs can also be glued, which prevents them from falling off during PCB soldering.
In addition to the insulating material, the most important part of the printed circuit board is the conductive connections adhering to it. These so-called conductor tracks are usually etched from a thin copper layer of mostly 35 micrometers. The components used are then joined together with small soldering points of the PCB material. The THR (through-hole reflow) soldering technique is used for this. This represents a combination of the particularly stable solder joints of the through-hole technique with the production processes of surface mounting, which can be automated.
Two main techniques are used for production. In the economically very attractive screen printing process, a stencil is placed on the base plate, covering it at the relevant points. Due to pressing during screen printing, the printing ink reaches only the places where there is no foil. Afterwards, the plate is etched to obtain the desired design.
Another variant for producing printed circuit boards is the photo technique. Here, the circuit boards are coated with a thin layer of copper and then a UV light-sensitive varnish is applied. The photo negative of the desired design is then projected onto the circuit board using UV light (on a scale of 1:1). This makes the design visible on the copper layer. Through the subsequent etching bath, only the illuminated lines remain after presentation of the photo.
Smart home appliances, foldable laptops and automated vehicles – printed circuit boards are at the heart of modern electronic devices. Given the endless array of electrical devices we use every day, they are also part of daily life. Just to be able to make phone calls and surf the Internet, electrical signals have to be relayed in the smartphone or laptop. Many companies have focused on the manufacture and further development of these small basic elements and are therefore involved in technical progress in industry and everyday life. As a result, it is already possible to produce very small, high-performance components and make visions possible that seemed unattainable just a few years ago. In the future, printed circuit boards will be further optimized to serve new, innovative technologies. Artificial intelligence and automation technology, for example, rely on increasingly complex circuits. The next few years will therefore see the realization of printed circuit boards that are only a few millimeters wide and enable complex electronic connections.
