• August 18, 2022

What's the Key Materials for High-Frequency PCB Circuit Boards The circuit material of a printed circuit board (PCB) is a key building block for RF/microwave circuits - essentially the starting point for these circuits. PCB materials come in many different forms, and the choice of material depends largely on the requirements of the intended application. For example, materials that reliably support high-frequency circuits in commercial wireless products can fail rapidly when exposed to the extremes of a military environment. A basic understanding of PCB material types and their parameters can help match materials to applications. As with many RF/Microwave components, PCB materials are classified and compared by a number of key parameters, including relative permittivity (Dk or εr), dissipation factor (Df), coefficient of thermal expansion (CTE), dielectric thermal coefficient constant ( TCDk) and thermal conductivity. When classifying different PCB materials, many circuit designers start with Dk. The Dk value of a PCB material refers to the capacitance or energy available between a pair of very close conductors fabricated on the material compared to the same pair of conductors in a vacuum. A vacuum creates a reference of 1.0, other dielectric materials provide higher references. For example, commercial PCB materials typically have Dk values in the range of about 2 to 10, depending on how they are measured and how often they are tested. Conductors on materials with higher Dk values can store more energy than conductors on materials with lower Dk values. Printed Circuit Board (PCB) The Dk value of a PCB material affects the size, wavelength, and characteristic impedance of transmission lines fabricated on that material. For example, for a given characteristic impedance and wavelength, the dimensions of a transmission line fabricated on a PCB material with a high Dk value will be much smaller than a transmission line fabricated on a PCB material with a lower Dk value, although other material parameters may vary . Designers facing circuits where loss is a critical performance parameter often prefer to use PCB materials with lower Dk values because these materials have lower losses than materials with higher Dk values. In practice, PCB materials can lose signal power in four ways: dielectric loss, conductor loss, leakage loss, and radiation loss, although both dielectric and conductor losses can be better controlled through the choice of PCB material. For example, the Df parameter provides a way to compare the dielectric loss of different materials, where a lower Df value indicates a material with lower dielectric loss. For a given transmission line impedance (e.g. 50Ω), the transmission line on the low Dk material will be physically wider than the transmission line on the high Dk material, and the conductor loss of the wider transmission line will be smaller. These wider transmission lines also translate into higher manufacturing yields (and savings i...

• August 05, 2022

PCB accelerates upward breakthrough, high-end products are shining According to Prismark's forecast, the PCB industry is expected to grow at a growth rate of 8.6% in 2021, and will grow at a compound annual growth rate of 5.8% between 2020 and 2025. By 2025, the global PCB industry output value will reach 86.33 billion US dollars. With the continuous development of science and technology, new technologies and new applications such as 5G communication, cloud computing, big data, artificial intelligence, Internet of Things, and electric vehicles continue to emerge, and the demand for PCBs is also increasing. It is worth noting that although my country is a big manufacturing country and there are many PCB companies, the product homogeneity is relatively serious, and it is excessively concentrated on low-end PCBs with cost advantages, traditional products such as single-layer/double-layer boards and multi-layer boards. In terms of high-end PCBs, the proportion of high-end PCBs is still relatively low, especially in terms of packaging substrates, high-end HDI boards, and multi-layer boards. At present, the market demand for high-end PCB boards has exploded rapidly, but the output of production capacity has increased slowly, resulting in a large gap between market demand and supply. With the continuous improvement and gradual optimization of China's PCB manufacturing technology, the market share of traditional single/double-sided PCB and multi-layer PCB has gradually declined, while the market share of high-tech and high-value-added PCB boards has continued to rise. Faced with the constant iteration and update of market demand, many PCB companies have begun to move towards the high-end PCB field with higher technical thresholds and greater capital investment. Although some technologies or production capacity are lagging behind, the market competition in the PCB industry is still fierce. The supply of high-end PCB market is still dominated by foreign manufacturers. Due to the imperfect supporting facilities around domestic PCBs, some key PCB-specific materials, high-end equipment and engineering software are dependent on imports. With the step-by-step breakthrough of domestic manufacturing technology, the relevant supply chain will also achieve good growth. Domestic PCB enterprises will gradually grow up, develop independent innovation technologies and equipment, and respond to the rapidly changing needs of the market. When the domestic PCB industry is booming, domestic PCB manufacturers have vigorously increased their high-end board business. On the one hand, they have the opportunity to escape from the low-end PCB Red Sea market, and on the other hand, they also have the opportunity to grow together with the domestic high-end industry. , to achieve a double breakthrough in technology and performance. With the market, high-end PCB products have higher requirements in terms of high-speed pcb material application, processing density and design layers. Th...

• July 15, 2022

The Technical Development of PCB Circuit Board In recent years, the focus of the printed circuit board market has shifted from computers to communications, and in the past two years, it has shifted to mobile terminals such as smartphones and tablet computers. Therefore, HDI boards for mobile terminals are the main point of PCB growth. Mobile terminals represented by smart phones drive HDI boards to be higher density and thinner. PCBs are all developing towards high-density thin lines, especially HDI boards. In the past, the definition of HDI board was that the line width/line spacing was 0.1 mm/0.1 mm and below, but now the industry basically achieves 60µm, and the advanced one is 40µm. PCB circuit pattern formation, traditionally is a chemical etching process (subtraction method) after photoimaging on a copper foil substrate. This method has many processes, difficult to control and high cost. The current fine circuit fabrication tends to be semi-additive or improved semi-fabrication. The bonding force between the conductor and the insulating substrate, the customary practice is to increase the surface roughness to increase the surface area and improve the bonding force, such as strengthening the decontamination treatment to roughen the surface of the resin layer, and use high-profile copper foil or oxidation to treat the copper surface. For thin wires, this physical method is not enough to ensure the bonding force. Therefore, the electroless copper-plated high-adhesion copper foil on the smooth resin surface was developed. For example, "molecular bonding technology" is to chemically treat the surface of the resin substrate to form a functional group that can be closely combined with the copper layer. In addition, there is the transfer of dry film imaging patterns during the production of fine lines, and the surface treatment of copper foil is one of the key factors for success. Use the best combination of surface cleaners and microetchants to provide a clean surface with sufficient area to promote dry film adhesion. Use chemical cleaning to remove the anti-discoloration treatment layer on the surface of the copper foil, as well as to remove dirt and oxides. Select an appropriate chemical cleaner according to the type of copper foil, followed by micro-etching the surface of the copper foil. In order to combine the imaging dry film with the copper layer, the solder mask pattern and the thin circuit reliably, the method of non-physical roughening of the surface should also be adopted. Semi-Additive Laminated Substrates At present, the hot spot of the semi-additive method is to use insulating dielectric film laminates. SAP is more advantageous than MSAP in terms of fine circuit realization and production cost. The thermal curing resin for SAP lamination is formed by electroplating copper after laser drilling to form via holes and circuit patterns. At present, the international HDI laminate materials use epoxy resin with different curing agents to ad...

• June 22, 2022

Why High TG Materials Are Used in PCB Production? In addition to the basic FR-4 material in PCB production, some customers also indicate that high TG material should be used in the materials. Then why do they use high TG material in PCB production? Used in PCB production is the full name of the TG glass transition temperature, on behalf of the glass transition temperature. The circuit board must be flame resistant and cannot burn at a certain temperature, only to soften. This temperature point is called glass state transition temperature (Tg point), this value is related to the size stability of the PCB board. When the temperature rises to a certain area of Tg PCB, the substrate will change from "glass state" to "rubber state", which is called the glass transition temperature of the sheet (TG). In other words, Tg is the substrate temperature that remains high (℃). That is to say, ordinary PCB substrate materials at high temperature, not only produce deformation, melting and other phenomena, but also on the mechanical and electrical properties of the sharp decline. Why high TG materials are used in PCB production? The increase of Tg base, the characteristics of heat resistance, moisture resistance, chemical resistance and resistance stability of Shenzhen circuit board proofing will be strengthened and improved. The higher the TG value, the better the temperature and other properties of the plate, especially in the lead-free manufacturing process, high TG is more widely used. High Tg refers to high heat resistance. With the rapid development of the electronic industry, especially the electronic products represented by computers are developing towards high functionalization and high multilayer, which requires the higher heat resistance of PCB substrate materials as an important guarantee. The appearance and development of high density installation technology represented by SMT and CMT make PCB more and more dependent on the support of high heat resistance of substrate in small aperture, fine line and thin form. This is also a big reason to use high TG materials in PCB production. Therefore, in PCB production, the difference between general FR-4 and high Tg FR-4 is that in the hot state, especially after hygroscopic heating, the material has differences in mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, thermal expansion and other conditions, and the high Tg product is obviously better than the common PCB substrate material.

• June 10, 2022

The Difference between High Speed PCB Board and High Frequency PCB Board With the development and construction of 5G communication, the electronic equipment industry needs more and more high frequency board and high-speed board. Because of the different use environment, high frequency board and high speed board have many common characteristics, but also have some differences. In this paper, the characteristics of high frequency and high speed plates are described, and the future development of high frequency and high speed plates is predicted. I. Demand of 5G network for high frequency and high speed pcb 5G, the fifth generation of mobile communications. Cellular communications have undergone four upgrades from analog communications (1G) to LTE (4G). Research and testing of 5G networks has progressed rapidly since 2012. In the past, from 1G to 4G, the main scene was the network communication between people, but 5G network will meet the Internet of everything, and open a new round of information network revolution. The 5G communication industry chain mainly includes the following five important links: (1) Network planning and design (preliminary technical research and network construction planning); (2) Wireless main equipment (core network, base station antenna, RF device, optical device/optical module, small base station, etc., wireless supporting, network coverage and optimization have been deployed); (3) Transmission equipment (after wireless equipment, wired transmission links are required, followed by optical fiber and cable, system integration, IT support, value-added services, etc.); (4) Terminal equipment (chip and terminal matching); (5) Operators. In addition to the above five important aspects, the following two aspects are also important: (6) PCB/CCL industry chain (used for base station RF, baseband processing unit, IDC and core network router, etc.); (7) Dielectric waveguide filter (base station radio frequency). In the process of 5G construction, products in different industries use different frequency bands, which leads to different requirements for high frequency and high speed plates for different products in different industries. It can be seen that 5G network is the comprehensive application of multi-frequency microwave. Therefore, products in different industries choose high-speed board and high-frequency board will be different. 2, the characteristics of high frequency board and high-speed board 2.1 Dielectric constant Dk and dielectric loss Df of materials When it comes to high frequency high-speed board, it is inevitable to talk about two concepts "dielectric constant -Dk" and "dielectric loss -Df". The PCB dielectric layer used for high-speed digital signal transmission not only acts as an insulating layer between conductors, but more importantly as a "characteristic impedance", which also affects signal transmission speed, signal attenuation and heating. The size of the dielectric loss (Df) indicates the attenuation...

• June 06, 2022

Aluminum Circuit Board Manufacturing and What Manufacturing Difficulties & Matters Needing Attention As the substrate material of PCB aluminum substrate manufacturing, aluminum clad plate mainly plays the role of interconnecting conduction, insulation and support to aluminum PCB substrate, and has great influence on signal transmission speed, energy loss and characteristic impedance in circuit. The performance, quality, manufacturability, manufacturing level, manufacturing cost, and long-term reliability and stability of PCB aluminum substrate are largely determined by aluminum clad copper plate. Aluminum based circuit boards have excellent electrical performance, heat dissipation, electromagnetic shielding, high dielectric strength and bending resistance. As a metal core PCB, whether it is single, double-side aluminum pcb or multi-layer aluminum circuit board, they have many similarities with FR4 circuit board in the manufacturing process, such as etching thick copper foil, aluminum surface etching protection, aluminum plate manufacturing and solder blocking printing. However, as a kind of advanced PCB, aluminum base PCB still has special aspects of manufacturing process, which requires strict and effective management and control. So, what are the precautions and manufacturing difficulties in aluminum based circuit board production? Machining: Drilling aluminum substrate can be done, but the inner edge of the drilled hole should not have any burrs, which will affect the pressure test. Milling the profile is very difficult. And the shape, the need to use advanced mold, mold production is very skilled, as one of the difficulties of aluminum substrate. After the shape is flushed, the edge is required to be very neat, without any burr, and does not touch the welding resistance layer of the plate edge. Usually use the soldier die, hole from the line, shape from the aluminum surface, circuit board when the force is on the shear pull, and so on are skills. After punching the shape, the warpage of the board should be less than 0.5%. The whole production process is not allowed to wipe the aluminum base surface: the aluminum base surface by hand touch, or by some chemicals will produce surface discoloration and blackening, which is absolutely unacceptable. Some customers do not accept the re-polishing of the aluminum base surface, so the whole process does not touch the aluminum base surface is one of the difficulties in the production of aluminum base circuit board. Some enterprises use passivation process, some in hot air leveling (tin spraying) before and after each affixed with a protective film many small skills, the eight imfairy across the sea, each brilliant. Over high voltage test: aluminum base plate of communication power supply requires 100% high voltage test. Some customers require DIRECT current, and some require alternating current. The voltage is 1500V and 1600V, and the time is 5 seconds and 10 seconds. Dirt, holes, aluminum edge...