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China is about to become home to the world’s printed circuit boards

PCB (printed circuit board) is the electronic components of the support and electrical connection carrier, the global PCB industry output value accounted for more than 1/4 of the total output value of electronic components industry, industrial scale of 60 billion US dollars. Due to China’s huge domestic market, as well as lower labor costs and perfect industrial support and other advantages, the global PCB production capacity from 2000 to continue to transfer to China, since 2006, China has surpassed Japan as the world’s largest PCB producer The
China’s PCB industry from catching up to beyond, through an extraordinary road. Now, China’s PCB industry has accounted for nearly 50% of the global proportion, becoming the world’s largest PCB supply base. This will be the best proof from the Shenzhen International Circuit Board (CS Show 2017). August 29 – 31 this year, CS Show 2017 exhibition will be held the fourth, this PCB / FPC procurement as the theme of the industry exhibition, exhibition area and the number of visitors record high, fully shows that the global PCB development focus is to China transfer. However, China to become a real PCB power, there is still a long way to go. Prior to this, industry experts have reminded, PCB enterprises should be noted that the operation of China’s PCB industry in the future will not have been in high growth, and PCB product structure will have a greater change in density, the difficulty will increase. Therefore, PCB enterprises to optimize the process, and continuously improve the enterprise automation and intelligence capabilities.
The Status Quo of China ‘s PCB Industry Development from the Top 100 List
China’s printed circuit list from the list of view, more than a decade China’s PCB industry in the production capacity has been rapid development. From the sales perspective, in 2002 released the first list, the 2001 annual sales of enterprises reached 100 million yuan more than 28, the first Guangzhou Tim Lee sales of 1.30 billion yuan. From 2005 onwards, to enter the list of enterprises has reached 100. To 2016 of the fifteenth, integrated PCB business income of 100 million yuan of enterprises reached 131, is the first 4.7 times. In the revenue, the integrated enterprise ranked No. 1 Zhen Ding technology has reached 16.819 billion yuan, 15 years ago, the first one of Guangzhou Tim Lee’s 13 times. From the regional development, PCB hundred enterprises are mainly located in Shenzhen, Huizhou, Suzhou, Shanghai, Kunshan, Taiwan, Hong Kong and other regions.
Domestic PCB products are from the low-end to high-end forward
Now, China’s PCB industry has entered a period of steady development, the products are mainly concentrated in the cost advantage of the low-end PCB. According to the market statistics of the China Chamber of Commerce and Industry, in 2016, the market share of domestic hard board and composite board was 13.0% and 3.7% respectively, while the market share of 4-layer board, 6-layer board and 8- Respectively, 19.1%, 13.5% and 10.4%, IC carrier board, 18 layers and above high-board sales accounted for a small, respectively, only 2.7% and 1.2%. HDI board and flexible board market share were 16.5%, 17.1%. With the continuous improvement of China PCB industry technology, the product structure is gradually optimized, the traditional product single / double panel and multilayer board sales are gradually reduced, high-tech, high value-added HDI board, packaging substrate, flexible Plate and other products accounted for the proportion of sales continue to increase.

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Liang Zhili: China PCB in the steady development

How does this article come from this topic? China PCB how can we say that the steady development?
Yes, I read the 16th (2016) China’s electronic circuit industry list (common name China PCB hundred enterprises list) and participated in the fourth CPCA outstanding national brand enterprises after the selection, deeply in China PCB in the steady development, And will be able to become larger and stronger. Looking back over the past 2016, it was a challenging year. Performance in the weak demand, especially Tablet PC, high-end smart phone segmentation, this year the price competition for many companies to breathe, such as FPC (flexible board), IC carrier board, smart phone printed circuit board; Prices soaring, resulting in a sharp rise in the cost of CCL, the market and the supply chain is very anxious.
By the chairman of the board summary of the general situation in 2016 eight words “price, listing, smart manufacturing” is the first two words “price”. This led to a decline in global production of almost all countries in 2016, except for China. The global PCB has been declining for two consecutive years, – 3.7 percent in 2015 and -2.0 percent in 2016. Taiwan (-3.5%), Japan (-7.74%), South Korea (-6.10%), North America (-0.03%) are negative growth. China is an exception, in recent years (2013-2016) global PCB growth: 0.9%, 2.3%, 3.7%, -2.0%; and China 2013-2016 PCB growth figures are: 7.3%, 6.7%, 2.0%, 1.5% See Table 1 for details.

That is, although China’s PCB growth from double-digit into a single digit, to micro-growth, but the performance of China’s PCB is the world’s best in the country / region. China PCB share of the global output ratio, from 48.3% in 2015 rose to 50.0% in 2016, in short, half of the global PCB production in China. In recent years, the global electronics industry downturn in the overall situation, the Chinese PCB against the world trend is still growing, accounting for the proportion of the world is still expanding, indicating that the development of China’s PCB industry in the world counterparts is safe and healthy.
2,2016, China PCB in the global counterparts in the performance is the best. In 2016 16th China PCB hundred enterprises list, we compare with the previous year (2015), see the following facts.
2.1 China PCB, the scale becomes larger
2016 the largest domestic business income of more than 4 billion yuan. Shennan Circuit 2016 annual revenue of 4.6 billion (695 million US dollars), the world’s top 100 PCB enterprises rose from 29 to 21;
Revenue more than 3 billion yuan also has a King King Electronics (3.383 billion);
China (Hong Kong) has over 2 billion yuan has six: Eton Electronics (2.355 billion yuan), Zhuhai Founder (27.39 billion yuan), Xing Sen fast (2.94 billion yuan), Chongda circuit (2.246 billion yuan) Five technology (2.14 billion yuan), according to Lianda Group (2.501 billion yuan);
Revenue of 10-20 billion yuan of domestic enterprises have 12, such as Shantou ultrasound, wins Hong Technology, Guangdong World Yun, Bo Min Electronics, Oshikang, Kunshan Huaxin, deep circuit.
Mainland China to enter the world’s total number of PCB hundred enterprises (annual revenue of more than 100 million US dollars) in September 2016 published data is 35, accounting for the total number of 104 enterprises in the ratio of 1/3, is the world’s top 100 enterprises the largest number of countries The
China FPC enterprises, a few years ago is a short board, from 2016 hundred list to see, more than 1 billion yuan of domestic enterprises have two (Xiamen Hong 10.88 billion yuan, BYD 1.05 billion), there are a number of FPC business development The momentum is very fierce, revenue is close to 1 billion yuan, such as up to electronics, Ansett, Yuan Sheng, Nai electric, Xinyu jump and so on. (Indeed, we also see that Nippon Mektron, the world’s largest PCB company, earned $ 3.307 billion in revenue in 2016, compared with 4.8 times the gap with the largest domestic business revenue. In 1616 the 16th comprehensive PCB enterprise ranking, 137 billion yuan revenue 137 companies, an increase of 6 over the previous year, the total revenue of 16.426 billion yuan, up 1.56 trillion yuan over the previous year growth of 2.76%. Into the list of the 16th domestic-funded enterprises 87, the number of enterprises in the same list the same as last year, the total revenue of 62.07 billion yuan, compared with 54.703 billion yuan in 2015 increased by 13.47%. Domestic enterprises grow faster.

2.2 China PCB, the benefits better
Business is good, the key to see the sound and earn no money. According to the statistical analysis of the operating results of China’s PCBs on the Shanghai Stock Exchange, the Shenzhen Stock Exchange and the HKEx’s 27 listed companies, the net profit of more than 100 million yuan is 13, the leader is Shengyi Technology (748 million yuan) Eton Electronics (588 million yuan), Jing Wang Electronics (538 million), Chongda Technology (376 million), Jin’an State (341 million).
2016 PCB industry 27 listed companies average profit rate of 11.3%, of which 17 purely PCB enterprises, net profit margin averaged 5.6%, up 1.3% over the previous year. 2016 PCB listed companies earnings per share, the best companies are: Jing Wang (1.99 yuan / share), Dayton (1.19 yuan / share), Chongda (1.01 yuan / share), Kingboard Chemical (4.88 Hong Kong dollars ), Kingboard Laminates (HK $ 1.45 / share). (16.73%), Jing Wang (16.37%), World Shipping (16.19%), Shenghong (13.51%), the number of PCB enterprises with more than 10% net profit margin. In the PCB industry chain for the equipment or materials listed companies, the development of healthy and stable, net profit rate of ≥ 10% are: Industry Technology (12.1%), Jinan Guoji (11.2%), Han’s laser (10.8%), Materials (15.7%), bulk sensitization (11.0%), Kingboard Chemical (17.2%), Kingboard Laminates (28.0%). The world’s leading CCL Enterprise Health Technology revenue this year reached 8.538 billion yuan, an increase of 12.2%, net profit of 748.2 million yuan, net profit rate of 8.8%, really cattle! In my statistics of China’s PCB listed companies 27, 2016 operating loss of two enterprises, the largest loss of nearly 100 million yuan.
2.3 China PCB business, revenue ≥ 10% a lot
The 16th China PCB list enterprises (not the industrial chain), annual revenue growth of 10% of a total of 68, accounting for about 50%. Among them, the growth rate ≥ 50%, 4; growth rate ≥ 40%, 8, such as Shenghong Technology, Guangzhou Guanghe, Meizhou Huasheng, Jiangsu Di Feida, etc .; growth rate ≥ 30%, 18, The growth rate of ≥ 20%, a total of 18, such as Shennan Circuit, Chongda, Oshikang, Jing Wang, Guangdong Branch Xiang, Meizhou Branch Jie, four will be Fuji, Kunshan million and so on; growth rate ≥ 10%, 23, such as the Guangdong World Shipping, Bo Min Electronics, up to electronics, animal husbandry Taylor, Zhuhai Founder, sincere up, Shenzhen Fu, Xiamen Hongxin, Hangzhou new triple, And so on.
2.4 China PCB industry chain, in the qualitative change
The 16th output value of over 100 million yuan, in addition to PCB enterprises, CCL (CCL) 13 companies, 15 special materials, special equipment / equipment 9, 9 special chemicals, environmental protection 4, all list of enterprises The total number is 187.
CCL list enterprises, in addition to the mentioned mentioned Health and benefit technology, there are two revenue in the decline, the remaining 11 business revenue growth rate in the (4-12)% range, listed CCL corporate profits are still good. R & D investment increased, independent innovation capability, invented the utility patent soared, high-frequency high-speed, high Tg, ultra-thin, metal, green, communication 4G, 5G with a variety of special CCL products continue to emerge. Can be expected, not a few years, China is not only CCL power, high-end high-quality special copper-clad copper plate substrate will be able to replace imports, become the world CCL power.
Special materials, in a single segment of the domestic and international counterparts occupy the leading position of the product has a number of varieties. For example, dedicated to the copper anode for more than 20 years R & D and production of Foshan Cheng’an, revenue of 2.29 billion yuan, as the domestic and international copper anode subdivision of the Big Brother; specifically focus on PCB drill Shenzhen Jinzhou, revenue reached 6.84 Billion yuan, in the country is the boss, in the world is the youngest, youngest; focus on PCB ink listed company Shenzhen Rongda, revenue reached 310 million yuan, an increase of 11%, development potential and momentum are good; focus on PCB pad Plate Liu Xin Industrial, revenue 387 million yuan, an increase of 21.2%, Liu Xin determination in the scale, variety, quality of all aspects of domestic and foreign enterprises to become the leading enterprises.
Special chemicals, the leader is Guangdong Guanghua (including Guangdong Dongshuo), Shenzhen Baikal, Guangdong Hafu, Shenzhen is Tianwei, Shenzhen Shuo and so on. These enterprises in recent years, steady growth, R & D investment, and its products into the domestic and international PCB high-end customers increased year by year, vibrant in the forward development. For example, Guangdong Guanghua 2016 years, made two high-end PCB chemical technology identification, the experts concluded that the product reached or exceeded the international advanced level. Guangdong Guanghua PCB chemical revenue in 2016 to reach 613 million yuan, is listed companies, R & D investment, production facilities, laboratory construction and talent to attract both first-class, very unique, such enterprises become a well-known international PCB chemicals business is full of hope The
Special equipment / equipment, industry peers have seen, domestic high-end equipment / equipment, especially intelligent, digital PCB equipment / equipment, its level and quality are making great strides and rapid development. The most gratifying is that domestic high-end equipment / equipment in the alternative import, domestic and foreign well-known PCB enterprises recognized the order and use more and more. Such as laser drilling machine, laser cutting machine, CNC drilling machine, LDI (automatic laser imaging system), vertical continuous plating automatic line (VCP), automatic intelligent on-off detection, high-end characteristic impedance tester. (2016 annual revenue of 1.43 billion yuan, the growth rate of 26.3%), the universe group (revenue 620 million yuan, the growth rate of 10.9%), is the industry technology (revenue 6.0 (Figure), the main business of the market, 100 million yuan, an increase of 68.2%), Kunshan Dongwei (revenue 350 million yuan, the growth rate of 85.2%). Shenzhen Mason, Nanjing, Guangzhou, Guangzhou dragon and other business performance are quite good. From the above data, China’s PCB industry chain development momentum sound, the product in the upgrade, the quality of the upgrade, the effectiveness of the gradual emergence.

3, corporate brand is a good reason for the steady development of China’s PCB in recent years
“Brand is good, affordable, business development on the sound”, this makes sense. When we analyze China’s PCB environment at home and abroad not very good circumstances, still able to sound and healthy development, there is a deep connotation of the reasons.
3.1 corporate strategy vision – look at the world, revitalize the Chinese strategy, is the way to win.
Strategy, is to be in the business activities to create their own unique position. I participated in the end of June the end of the fourth CPCA outstanding national brand enterprise selection activities. Reporting enterprises 105, enterprises registered more than 10 years a total of 82, accounting for 82% of the total number of enterprises, of which more than 15 years 58, accounting for 55% of the total. A considerable number of enterprises are established in the eighties and nineties of last century. These companies, together with the high-speed development of registered companies in recent years, star enterprises, one from the date of the establishment, to shoulder the revitalization of China’s ambition, fighting in the very bitter and very challenging PCB manufacturing industry, quietly Year after year deep plowing secretly, insisted and then insisted, step by step forward, twenty or thirty years of accumulation formed today’s corporate brand, only today’s enduring. To give a few examples: Shantou ultrasound was established in March 1985, 32 years; Shennan circuit was established in July 1984, 33 years; Jing Wang Electronics was established in March 1995, 22 years; Anjie Li was established in April 1994, 23 Year-old into the prime of life; Jin Bazai set up in May 1997, 20 years; Guangdong Chengde 1987 set up, 30 years of history; Suzhou Airlines in January 1986 was established, 31 years; Kunshan Huaxin set up in June 1993, 24 years old; Hussein Electronics was established in April 1992 and worked in China for 25 years …….
3.2 enterprise core competitiveness – its own unique, difficult to imitate
Enterprises can be sustainable and sustainable development, the need for enterprises with core competitiveness. This is a long-term ability to take advantage of the enterprise, is unique to the enterprise stand the test of time, and competitors are difficult to imitate the technology and ability. Steady development and good efficiency of the enterprises tend to have this unique core competitiveness. (Shenzhen), the global service, a large number of domestic and foreign mother board (backplane) are concentrated to the Shennan and Hushi, the company has a large number of motherboards, Has become their unique advantage. Jing Wang Electronics to rigid multi-layer board as the basis, the lateral development of FPC and metal substrates, the formation of Jing Wang unique technical capabilities and advantages. Xing Sen fast and Chongda technology focus on the model and small batch PCB, multi-species, short delivery, good service, a world-renowned fast board model bones of the leading manufacturers. Thousands of years only for the PCB copper ball anode Foshan Chengan, “copper ball dream, with the Chinese dream”, a small product made a big business! China PCB enterprises to withstand the fierce domestic and international market competition in the wind and waves, and gradually become an internationally competitive leader in the field of subdivision, which is China’s PCB industry, one of the reasons for the enduring.
3.3 win customers and the market – good products, good quality
Business survival and development, there must be a good market demand for products; have a good product, must have a good quality system to run; today’s quality, that is tomorrow’s market; quality and service must meet customer needs and expectations. These quality concepts in the brand of enterprises have been deeply rooted. “PCB enterprises engage in quality, it is important to do, do not dry up, do not busy, catch delivery is more important than anything else,” this backward idea abandoned, “when the quality and cost of conflict, quality first; Period with the quality of the conflict, the quality of the first “quality awareness set up, the enterprise will really long lasting. The outstanding national enterprise brand selection, joined the “customer praise and provide the corresponding medal certificate” as an important part of the selection. We see that Shennan Circuit won the title of “Core Gold Supplier”, and was awarded the “Best Partner of the World” award.
Rockwell Colins “Best Supplier of the World” and “President’s Special Award”. It is “Gold Award Silver Award as a customer praise, Gold Cup Silver Cup as the reputation of customers!”, Shennan circuit brand good cattle ah!
China PCB enterprises in the quality assurance capabilities, in addition to access to UL certification, a large number of enterprises also received national or provincial standardization of good behavior enterprise title, the provincial brand-name products honor, well-known trademarks or well-known trademarks, The title of the government quality award. In the quality assurance system certification, many enterprises in addition to ISO-9001 and ISO-14001 system certification, but also access to aerospace defense management system, medical management system, the national. military standard system recognized

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Decrypting PROTEL DXP software for PCB design techniques

Protel DXP is the first board-level design system that integrates all design tools, and electronic designers can plan their own design from the initial project module to the final production data. Protel DXP runs on an optimized design browser platform with all of today’s advanced design features to handle complex PCB design processes. Protel DXP as a new circuit design software, based on the previous version of the addition of many new features. The new customizable design environment features dual monitor support, fixed, floating and pop-up panels, powerful filtering and object positioning capabilities, and enhanced user interface. Protel DXP provides a comprehensive design solution through the design of input simulation, PCB rendering editing, topology automatic routing, signal integrity analysis and design output.
This article references the address:
PCB board design of the general principles include: circuit board selection, circuit board size, component layout, wiring, pad, fill, jumper and so on.
The circuit board is generally made of copper laminates, board selection from the electrical performance, reliability, processing technology requirements and economic indicators and other considerations. Common copper laminates are copper phenolic paper laminates, copper-coated epoxy paper laminates, copper-coated epoxy glass cloth laminates, copper-clad epoxy phenolic glass cloth laminates, copper-coated polytetrafluoroethylene glass Cloth laminates and multilayer printed circuit boards with epoxy glass cloth and so on. Different materials of the laminate has different characteristics. Epoxy resin and copper foil has an excellent adhesion, so the copper foil adhesion strength and operating temperature is high, can be 260 ℃ in the melting tin does not blister. Epoxy resin-impregnated glass cloth laminates are less affected by moisture. Ultra-high frequency circuit board is best deposited copper polystyrene glass cloth laminate.
In the requirements of flame-retardant electronic equipment, also need flame retardant circuit boards, these boards are immersed in the flame retardant resin laminate. The thickness of the circuit board should be determined according to the function of the circuit board, the weight of the components installed, the specifications of the circuit board socket, the dimensions of the circuit board and the mechanical load.
Mainly should ensure sufficient rigidity and strength.
Common circuit board thickness of 0.5mm, 1.0mm, 1.5mm, 2.0mm
From the cost, copper wire length, anti-noise ability to consider, the smaller the better the size of the circuit board, but the board size is too small, the poor heat dissipation, and adjacent wires easily lead to interference. The production cost of the circuit board is related to the area of the circuit board, the larger the area, the higher the cost. When designing a circuit board with a housing, the size of the board is also limited by the size of the chassis. Be sure to determine the size of the chassis before determining the board size. Otherwise, the board size can not be determined. In general, the wiring range specified in the forbidden wiring layer is the size of the board size. The best shape of the circuit board is rectangular, the aspect ratio is 3: 2 or 4: 3, when the circuit board size is greater than 200mm × 150mm, should consider the mechanical strength of the circuit board. In short, should consider the pros and cons to determine the size of the circuit board.
Although the Protel DXP can automatically layout, but in fact the layout of the circuit board is almost done by hand.
To carry out the layout, generally follow the following rules:
1. The layout of special components
The layout of special components from the following aspects:
1) high-frequency components: the connection between the high-frequency components as short as possible, try to reduce the distribution of the parameters and the electromagnetic interference between each other, vulnerable components can not be too close. The distance between the components belonging to the input and the components belonging to the output should be as large as possible.
2) Components with high potential difference: The distance between the elements with high potential difference and the connection should be increased to avoid damage to the components when an unexpected short circuit occurs. In order to avoid the occurrence of creepage phenomenon, generally require 2000V potential difference between the copper film line distance should be greater than 2mm, if the higher potential difference, the distance should also increase. With high voltage devices, should be arranged as far as possible when debugging difficult to reach the place.
3) too much weight components: such components should have a fixed bracket, and for large and heavy, more heat and more components, should not be installed on the circuit board.
4) heat and thermal components: Note that the heating element should be away from the thermal components.
5) can adjust the components: for the potentiometer, adjustable inductance coil, variable capacitor, micro switch and other adjustable components of the layout should consider the structural requirements of the machine, if the machine is adjusted, it should be easy to adjust on the circuit board Of the place, if the machine outside the adjustment, its position with the adjustment knob in the chassis panel on the corresponding position.
6) Board mounting holes and bracket holes: The mounting holes for the circuit board and the mounting holes of the brackets should be reserved because they can not be routed near the holes and holes.
2. According to the circuit function layout
If there is no special requirements, as far as possible in accordance with the schematic components of the arrangements for the layout of the components, the signal from the left into the output from the right, from the top input from the bottom of the output. In accordance with the circuit process, the arrangement of the various functional circuit unit position, so that the signal flow more smoothly and maintain the same direction. With each functional circuit as the core, around the core circuit layout, component arrangement should be uniform, neat, compact, the principle is to reduce and shorten the lead between the various components and connections. The digital circuit part should be separated from the analog circuit section.
3. The distance of the component from the edge of the board
All components should be placed within 3mm from the edge of the board, or at least the distance from the edge of the board is equal to the thickness of the board, which is due to the use of high-volume production line plug and wave soldering, But also to prevent the deformation caused by the shape of the circuit board edge, causing copper film broken lead to waste. If the components on the circuit board too much, had to be more than 3mm, you can add the edge of the circuit board 3mm auxiliary side, in the auxiliary side to open V-shaped groove, in the production by hand breaking apart.
4. The order in which the components are placed
First place the fixed position with the structure in close contact with the components, such as power outlets, lights, switches and plug-ins and so on. And then placed special components, such as heating elements, transformers, integrated circuits. Finally, place small components, such as resistors, capacitors, diodes, and so on.
The rules of wiring are as follows:
1) line length: copper film should be as short as possible, in the high-frequency circuit should be the case. The fillet should not be rounded or beveled, and the right angle or sharp corners may affect electrical performance in the case of high frequency circuits and high wiring densities. When the double-panel wiring, the two sides of the wire should be perpendicular to each other, oblique or curved alignment, to avoid parallel to each other to reduce the parasitic capacitance.
2) line width: the width of the copper film should be able to meet the electrical characteristics of the requirements and easy to produce as a criterion, its minimum value depends on the current flowing through it, but generally should not be less than 0.2mm. As long as the board area is large enough, copper wire width and spacing the best choice 0.3mm. Under normal circumstances, 1 ~ 1.5mm line width, allowing the flow of 2A current. For example, the ground and power lines are best to use a line width greater than 1mm. When the two wires are between the integrated circuit board pads, the pad diameter is 50 mils, the line width and line spacing are 10 mils. When the pad is taken between a line, the pad diameter is 64 mils, line width and line The spacing is 12mil. Note the conversion between metric and imperial, 100mil = 2.54mm.
3) Line spacing: the spacing between adjacent copper film lines should meet the electrical safety requirements, and in order to facilitate the production, the spacing should be as wide as possible. The minimum spacing can withstand at least the peak of the applied voltage. In the case of low wiring density, the spacing should be as large as possible.
4) Shield and ground: copper wire of the public ground should be placed on the edge of the circuit board as much as possible. In the circuit board should be as much as possible to retain the copper foil to do the ground, so that can enhance the shielding capacity. In addition, the shape of the ground wire is preferably made into a loop or a grid. Multi-layer circuit board as a result of the use of inner power and ground special layer, which can play a better shielding effect.
The size of the pad size of the pad must be determined by the diameter of the metal lead and the thickness of the solder layer, the thickness of the tin layer, the pore size tolerance, and the thickness of the hole metallized plating. The diameter of the hole of the disk. For example, the resistance of the metal pin diameter of 0.5mm, the pad hole diameter of 0.7mm, and the pad diameter should be pad diameter plus 1.2mm, the minimum should be pad diameter plus 1.0mm. When the pad diameter is 1.5 mm, a square pad may be used in order to increase the peel strength of the pad. For holes with a hole diameter less than 0.4 mm, the outer diameter of the pad / pad hole diameter is 0.5 to 3. For holes with a hole diameter greater than 2 mm, the pad diameter / pad hole diameter is 1.5 to 2.
Common pad size
Pad hole diameter / mm
0.4 0.5 0.6 0.8 1.0 1.2 1.6 2.0
Pad outer diameter / mm
1.5 1.5 2.0 2.0 2.5 3.0 3.5 4
Consider the following when designing the pad:
1) The edge of the pad hole to the edge of the circuit board is greater than 1mm, which can avoid the processing lead to pad defects.
2) When the copper film is connected with the pad, the connection between the pad and the copper film is designed as a teardrop-like, so that the pad can not be easily peeled off. The connection between the copper film and the pad is not easy to disconnect.
3) adjacent pads to avoid an acute angle.
Large area filled
The large area on the circuit board filled with two purposes, one is the heat, the other is to use shield to reduce interference, in order to avoid the heat generated when the welding of the circuit board to produce no gas emissions leaving the copper film off, The area is filled with a window, which fills the grid. The use of copper can also achieve the purpose of anti-interference, and copper can automatically bypass the pad and can be connected to the ground.
Jumper wire
In the design of single-sided circuit boards, when some copper film can not be connected, the usual practice is to use the jumper, the length of the jumper should choose the following: 6mm, 8mm and 10mm.
1. Ground impedance of the common impedance of the circuit on the ground diagram of the circuit that the zero potential and used as a common reference point in the other points in the circuit, in the actual circuit due to ground (copper film line) impedance exists, Bring together a total impedance interference, so when wiring, can not be connected with the ground symbol of the points together, which may cause harmful coupling and affect the normal work of the circuit.
2. How to connect the ground is usually in an electronic system, the ground is divided into systematically, chassis (shield), digital (logical) and analog ground, etc., in the connection should pay attention to the following ground point:
1) Properly select single point ground and multipoint ground. In the low-frequency circuit, the signal frequency is less than 1MHz, wiring and components between the inductance can be ignored, and ground circuit resistance generated by the voltage drop on the circuit a greater impact, it should be a single point grounding method. When the frequency of the signal is greater than 10MHz, the impact of ground inductance, it is appropriate to use the nearest ground multi-point grounding method. When the signal frequency between 1 ~ 10MHz, if the use of single-point grounding method, the ground length should not exceed the wavelength of 1/20, or should be multi-point grounding.
2) digital ground and analog ground separately. The circuit board has both digital circuits and analog circuits, so that they should be separated as much as possible, and the ground wire can not be muted and connected to the ground side of the power supply (preferably the power supply terminals are also connected separately). To maximize the area of the linear circuit. General digital circuit anti-interference ability, TTL circuit noise margin of 0.4 ~ 0.6V, CMOS digital circuit noise margin for the power supply voltage of 0.3 ~ 0.45 times, while the analog circuit as long as the micro-level noise, Enough to make it work is not normal. So the two types of circuits should be separated from the layout and wiring.
3) as thick as possible. If the ground is very fine, the ground potential will change with the current changes, resulting in the interference of the electronic system signal, especially the analog circuit part, so the ground should be as wide as possible, generally more than 3mm is appropriate.
4) The ground wire forms a closed loop. When there is only a digital circuit on the circuit board, it should make the ground loop, which can significantly improve the anti-jamming capability, because when the circuit board has a lot of integrated circuits, if the ground is very fine, will cause a larger grounding The potential difference, and the ring ground can reduce the grounding resistance, thereby reducing the ground potential difference.
5) the same level of circuit grounding should be as close as possible, and the level of the power supply filter capacitor should also be connected to the level of the ground.
6) the connection of the ground line. The total ground line must be strictly in accordance with the high frequency, intermediate frequency, low frequency order level from weak to strong electrical connection. High-frequency part of the best use of large area surrounded by ground to ensure a good shielding effect.
Electronic systems with microprocessors, anti-jamming and electromagnetic compatibility are issues that must be considered in the design process, especially for systems with high clock rates and fast bus cycles; systems with high power, high current drive circuits; Signal and high-precision A / D conversion circuit system. In order to increase the system anti-electromagnetic interference ability should consider the following measures:
1) Select the microprocessor with low clock frequency. As long as the controller performance to meet the requirements, the lower the clock frequency the better, low clock can effectively reduce noise and improve the system’s anti-jamming capability. As the square wave contains a variety of frequency components, the high-frequency components can easily become a noise source, under normal circumstances, the clock frequency of 3 times the high-frequency noise is the most dangerous.
2) to reduce the distortion in signal transmission. When the high-speed signal (high signal frequency = rising edge and falling edge of the fast signal) in the copper film transmission, due to the copper film line inductance and capacitance, the signal will be distorted, when the distortion is too large, it will make System work is unreliable. General requirements, the signal on the circuit board to spread the copper film as short as possible, the less the number of viable the better. Typical values: no more than 25cm in length, no more than 2 holes.
3) to reduce the cross-interference between signals. When a signal line has a pulse signal, it will interfere with another weak signal line with a high input impedance. In this case, it is necessary to isolate the weak signal line by adding a grounded contour to surround the weak signal, or Increase the distance between lines, for different levels of interference can be used to increase the power and ground level solution.
4) Reduce the noise from the power supply. Power supply to the system while providing energy, but also its noise added to the power supply system, the system reset, interrupt and some other control signals are most vulnerable to external noise interference, so should be appropriate to increase the capacitance to filter out these Noise from the power supply.
5) pay attention to the circuit board and components of the high-frequency characteristics. In the case of high frequency, the circuit board on the copper film, pads, vias, electricity