Equipment and services for electronics production in Bulgaria

Digitalization, Internet of things and automation technologies are to be among the driving factors of Industry 4.0, economists anticipate. Other recent tendencies in industry such as green technologies, smart technologies for energy consumption and e-mobility, pave the path to both traditional and newly emerging entrepreneurships. This interesting global stage setting is a chance for a fresh impetus to the sector of electronics in Bulgaria as well. Equipment, services and electronics manufacturing has a long history in Bulgaria and the most insightful experts already predict its significant contribution to development of Bulgarian economy in the long term.

In recent years electronics has become the biggest export sector in Bulgaria. In 2017 the export of electronics and electric equipment totalled BGN 5,6 billion. The steady growth in the industry over the years has historical grounds as the creation of vast expert community has started in 70s and 80s when a large number of people received higher engineering qualifications and started gaining key competences in the manufacturing plants at that time. Today the intellectual capacity in the sector is still the main factor that attracts investors from all over the world. Meanwhile, a number of local entrepreneurial initiatives has been launched and has proved to be successful not only in fabrication but also in the supply of equipment and services for electronic production.

Historical and process-specific factors to the electronics sector

Semiconductor manufacturing is an industry with long history in Bulgaria. "ELKA 42" – the world’s first calculator with MOS integrated circuits was created in Bulgaria. Elka’s success passed beyond the expectations and its name became a synonym for calculators.

Digital revolution would have been impossible without the invention of MOS integrated circuits. Without MOS integrated circuits, modern processors, computers, smartphones and all kinds of smart gadgets would not exist. The technology based on metal oxide semiconductors (MOS) and the miniaturization of the electronic circuit has proven to be a game-changer for all industries and for the development of world economy, as the technology later became the standard. The importance of integrated circuits has risen with the increase of the variety of their application.

Manufacture of electronics includes a suite of complex processes where depending on the technique different types of equipment and services are utilized. Manufacturing of PCB for example starts with the fabrication data generated by computer aided design, and component information. The fabrication data is read into the CAM (Computer Aided Manufacturing) software. These services are offered by a number of companies in Bulgaria, which either provide their own solutions or those of their partners.
The processes that follow include covering the copper foil PCB layers with protective mask so that the copper pattern replicates the pattern in the CAM system. Subsequent etching removes the unwanted copper unprotected by the mask. Some fabrication methods utilize an alternative process involving ink-jetting of conductive ink on a blank (non-conductive) board. Inkjet printing, being an additive process, means less process steps compared to traditional solder mask coating or Laser Direct Imaging (LDI). Photo and development processes are eliminated as is the need for full surface flooding. This speeds up production while reducing waste, material and energy consumption.
Photoengraving uses a photomask and developer to selectively remove a UV-sensitive photoresist coating and thus create a photoresist mask that will protect the copper below it. Direct imaging techniques are sometimes used for high-resolution requirements. PCB milling uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine operates in a similar way to a plotter, receiving commands from the host software that control the position of the milling head in the x, y, and (if relevant) z axis.

Laser etching is a manufacturing process where the copper may be removed directly by a CNC laser. Like PCB milling, this is used mainly for prototyping. Plasma etching machines are used for the removal of material from surfaces via plasma processes. It is also described as dry etching because conventional etching processes are carried out with wet chemical methods using aggressive acids. The plasmas of the process gases change the aggregate state of the material to be etched from solid to gaseous, and a vacuum pump extracts the gaseous products. Masks can be used to etch partial areas or structures only. Plasma etching is carried out in low-pressure plasma because longer treatment duration is necessary to achieve noticeable etching effects, and because most etching gases can only be used in low-pressure plasma.
Surface-mount technology (SMT) is a method, in which the electronic components are mounted directly onto the surface of a printed circuit board (PCB). An electronic component mounted in this manner is referred to as a surface-mount device (SMD).

Flip chip, also known as controlled collapse chip connection is a method for interconnecting dies such as semiconductor devices, IC chips, integrated passive devices and microelectromechanical systems (MEMS), to external circuitry with solder bumps that have been deposited onto the chip pads.
Large variety of electronics fabrication equipment and services are offered on the market by companies based in Bulgaria. The article further presents statistic data representing the current situation in the sector.

Current production and market statistics

Growing share of renewable energy production, smart grid integration and e-mobility in future will also stimulate higher demands in electronic components urging the rapid development of the sector. According to analysts there are over 400 enterprises in the industry in Bulgaria, the majority of them owned by foreign investors, but many local companies flourishing as well. Over 40 000 people are working in the sector. Companies are predominantly located in Sofia but there are still many large organizations spread across the country.

According to data by National Statistical Institute in 2020 the quantity of integrated circuits produced amounts to 9 703 540 pcs, and production sold totals BGN 101 304 thousand excluding VAT. Cards containing electronic integrated circuits (smart cards) produced were 4 003 380 pcs and the quantitiy of sales was 4 079 130 pcs, which in value totals BGN 2618 thousand. The production of printed circuit boards containing conductive elements equalled 3 532 101 pcs. Mounted printed circuit boards produced in 2020 were 45 537 944 pcs; total quantity sold 59 664 070 pcs; sales were estimated at BGN 88 051 thousand. The quantity of laptops and tablets produced was 45 649 pcs; total quantity sold 45 649 pcs for the amount of BGN 30 785 thousand. Desktop computers produced were 3721 pcs; total quantity sold – 3722 pcs. Sales were for BGN 3049 thousand.

Enhanced solutions and services offered on Bulgarian market

Some of the Bulgarian distributors of cutting-edge industrial instruments and equipment provide novel solutions for ground-breaking automation based on collaborative robots, complete automatization for processes substituting manual-labour tasks associated with the ICT industry.

A number of companies offer complete suite of services for design and fabrication of PCBs including execution of personalised projects by clients. Professional CAD designs of printed boards can be easily created with specialised CAD software. The PCB file contains the topology of the printed circuit board, and all the necessary information for production, as well as bill of materials. These services are suitable for prototyping. Stencils fabrication processes include laminating, exposure, developing of photoresist, acid etching, stripping of photoresist. Finishing involves covering circuit elements with tin-lead coating. In surface finishing infra-red dipping is applied to track and pads coated with Sn/Pb. Hot air leveling (HAL) – soldermask areas are covered with Sn/Pb – 0,0005~0,035 mm.

Electronic components require advanced and high-precision manufacturing processes with potential for repeatability. With this respect laser systems are largely used in electronics manufacturing. Innovative laser technologies and advanced resources for electronic parts and components are present on the market. Variety of laser system configurations are available to serve extensive applications in laser welding, laser marking and laser cutting. Modern laser solutions reduce cycle times, produce precision parts and achieve increased productivity while lowering cost per unit. Manufacturers offer specially designed equipment in terms of appropriate laser source in order to make them versatile, robust, and easy to use.

UV lasers use “cold” cutting technology, which makes it easy to control the thermal charring of the edge. A UV laser is a better option if reducing char is more vital than speed. The advantages of UV laser cutting include high accuracy and very clean cuts, low HAZ, narrow kerf width, accurate cuts of copper leads. However, the technology takes longer cut times and is more expensive compared to other laser methods.

When utilizing a UV laser to get clean cuts, several repetitions of laser scanning are utilized to singulate the PCBs. To control the cut speed, software controls are utilized.
A CO2 laser is a preferable option if cycle time is important. CO2 lasers are more commonly used to create perforated cuts. Making use of the perforation technique helps reduce char as well as allows for easier load and unload of panels and boards from the cutting machine. The amount of charring and cycle time increases as material thickness increases. If V-grooves can be used to manufacture panels at cut locations, laser cuts can be faster and cleaner.

Some manufacturers focus on meeting the demands of middle and small volume production sites. Examples include local based companies offering manual stencil printers designed for such fabrications, which at the same time are capable of precise printing of fine-pitch components down to 0,4 mm / 16 mill pitch, where the linear bushing guidance ensures vertical separation of the template from the PCB without blurring. Printers have adjustable print pressure of the squeegees and angle adjustment possibility to ensure precise printing. Insightful manufacturers and distributors insist on offering equipment with features ensuring reliability, ease of use and maintenance. Flexibility and fast changeover are also characteristics largely sought after in the stencil-printer market as these features make them suitable for small series of PCBs, for designer teams or handling of more than one pick-and-place machines.

Large distributing companies offer completely autonomous stencil-printing systems for serial fabrication. Those printing specialists represent the future of PCB fabrication. Some models run completely autonomously for up to eight hours. These systems have numerous smart features. The printers enable a product change in less than two minutes, the NPI is done in less than ten minutes without Gerber data (Gerber format, an open ASCII vector format for (PCB) designs that is the standard used by PCB industry software to describe the printed circuit board images: copper layers, solder mask, legend, drill data, etc). Different print formats can be processed while maintaining the same cycle times. Such printing systems provide highest precision and flexibility and are characterized with dynamic scalability. It is possible to integrate any options and features in order to adapt the systems as per individual needs of the client. Printers are scalable and can be retrofitted on-field at any time. This allows adaptability and flexibility as well as easy short-term changes.

An important step in the assembly process is placing the components on the board and for surface mount devices (SMD) this is done with an automated pick-and-place machine. Using automated pick-and-place machines is much faster and more accurate than manual placement of the surface mount components. Such machines have automated registration and super fast component placement with built-in checks that use a variety of cameras.

Engineers continue their work on extending the autonomy of systems in order for the machines to be able to carry out job changes almost independently without requiring significant manpower and time as this is an essential step towards building an autonomous, smart factory. Autonomous stencil printing systems reduce training effort, increase effective use of personnel and smooth production processes as well as avoid errors. Due to reduced setup times usability and traceability increase. Stencil and screen printers allow application of solder paste to printed circuit boards precisely and with repeatable accuracy.

Bulgarian companies offer some of the state-of-the-art precision soldering robotic systems incorporating innovative design concepts and precision components to ensure highest accuracy. The combination of high precision hardware and intelligent software ensures precision soldering and low operator training costs. System equipment varies depending on the model to suit different applications. Solutions include dual-arm, six-axis soldering robots as well as 8-axis soldering/dispensing platforms, full vision mapping and fiducial marks. Robots may be equipped with intelligent compensation for PCBA variance, image recognition and integrated mapping systems, laser height measurement functionalities, Curie heat technology for precise temperature control.

Both types of precision positioning systems are available – robots with typical Cartesian mechanical structure and soldering robots equipped with full vision (camera resolution 0,015 mm) to verify the procedure being undertaken. The latter solution does not simply follow a pre-determined program but the soldering robot has an observation mode, a verification mode and decision-making capabilities. This capability of collecting and utilizing data for production processing is one of the most important factors necessary to meet the requirements of Industry 4.0 standards.

Through the use of servomotors and precision ballscrews, modern soldering robotic systems are capable of accurately meeting the requirements of high speed operation, repeatability and durability. Application programming is made simple by using full image-merging and mapping techniques. Dynamic laser height measurement/adaptive control, ensures precision soldering repeatability. A full vision mapping and matching system, provides for intelligent decision-making during procedural operations.

Electronics sector in Bulgaria in recent years has demonstrated huge market potential involving some of the most advanced automation manufacturing processes. Innovative techniques are introduced in film coating as well. Highly sophisticated atomic layer deposition (ALD) is an advanced thin film coating method, which is used to fabricate ultra-thin, highly uniform and conformal material layers for several applications.

ALD uses sequential, self-limiting and surface-controlled gas phase chemical reactions to achieve control of film growth in the nanometer/sub-nanometer thickness regime. Due to the film formation mechanism the gases won’t react until in touch with the surface, which means the film growth proceeds by consecutive atomic layers "up" from the surface – the ALD film is dense, crack-, defect- and pinhole-free and its thickness along with structural and chemical characteristics can be precisely controlled on atomic scale.

The ALD process is digitally repeatable and it can be performed at relatively low temperatures. This gives the possibility to construct not only single material layers but also doped, mixed, or graded layers and nanolaminates. Low process temperature on the other hand allows coating of sensitive materials such as plastics and polymers. In addition to IC component manufacturing, other large scale industrial applications for ALD can be found in sensor, LED and MEMS manufacturing.

However, soldering issues can often be traced to cheap solder paste printing. Any mistakes in solder paste printing may lead to unreliable assembly. In such cases solder paste inspection systems (SPI) are implemented, which check if the paste is appropriately printed onto the board. The SPI machine uses cameras to capture 3D images and evaluate the solder paste through solder volume, alignment, and height. It can also identify unsuitable sizes and imperfections so manufacturers can correct them.