Introduction to the printed circuit board (PCB)
PCB top no standard parts, also often referred to as "the PCB Printed Wiring Board (PWB)".
PCB we can see almost all electronic devices can not do without it, small electronic watches, calculators, general computer, large computers, electronic communication equipment, military weapon systems, integrated circuits and other electronic components as long as they are to be used in the electrical interconnection between the PCB. In addition to fixing a variety of small parts, but it offers a variety of integrated circuits and other electronic components fixed mechanical support assembly to achieve integrated circuits and other electronic components and electrical connections between wiring or electrical insulation, provide the required electrical characteristics as characteristic impedance. While providing for the automatic soldering solder graphics; Cartridge for the components, inspection, maintenance provide identification characters and graphics. As electronic devices become more complex, the need for more and more parts, PCB top of the line with the part of the increasingly dense.
Manufacturing principles
We open generic computer will be able to see a healthy dish of soft films ( flexible insulating substrate ) , silver white ( silver ) and a conductive pattern printed on health -bit graphics . Because Universal serigraphy method to get this graphic , we call this a flexible printed circuit boards for the Silver PCB . The printed circuit board computer city we went to see the variety of computer motherboards , graphics cards, network cards , modems , sound cards and household appliances on different. It is used by the paper-based substrate (commonly used in single-sided ) or glass cloth ( commonly used in double-sided and multilayer ) , phenolic or epoxy prepreg , surface glue on one side or both sides of the copper-clad laminate curing book again made . This circuit board copper book plate, we call it a rigid plate . Then made PCB, we call it a rigid printed circuit boards . There are single -sided printed circuit pattern we said PCB, double-sided printed circuit pattern , and then double-sided printed wiring board formed by metallization interconnect holes , we called double panel . If you use a double-sided for the inner , two -sided or two -sided as to make the outer lining , two -sided printed circuit boards for the outer layer , through the positioning system and insulation material are alternately bonded together and conductive pattern according to the design requirements for the interconnection of printed circuit boards become four , six of the printed circuit board , also known as multi-layer printed circuit boards . Now there are more than 100 layers of the PCB and practical .
Production process of PCB
PCB production process is more complex, it involves a wide range of technology , from simple to complex machining machining, as well as ordinary chemical reactions , such as photochemical electrochemical thermochemical processes , aspects of knowledge , such as computer-aided design CAM . And technological problems in the production process and will always meet a lot of new problems and some problems have not disappeared identify the cause of the problem , due to its production process is a non-continuous line form , will result in any one part of the problem across the board cut consequences or a lot of scrap , scrap printed circuit board if recycling is not larger process engineers work under pressure , so many engineers left the industry to printed circuit board equipment or material supplier to do the work of sales and technical services .
The board itself is made of an insulating substrate insulation, not easy to bend the material made into . Can be seen on the surface of the fine copper wiring material , the original copper foil covering the entire board , part of the manufacturing process and in the etching process is away , leaving to become part of a fine mesh lines the . These lines are called conductors (conductor pattern) , or said wiring and connecting the circuit to provide the parts on the PCB .
Parts to be fixed above the PCB, we will take their feet welded directly on the wiring . At the most basic PCB ( single panel ) , the parts are concentrated in one side , the wire is focused on the other side. Suppose we need burrows on the board , so that the pin to pass through to the other side of the board , so the parts are welded pin on the other surface. Because of this , PCB 's are called positive and negative parts surface (Component Side) and the welding surface (Solder Side).
If there are certain parts PCB top , you need to complete post-production can also be removed or put back , it will be used when the part is installed socket (Socket). Because the socket is soldered directly to the board , the parts can be any disassembly.
If you want two interconnected PCB, generally we will edge connector commonly used in " Goldfinger " in (edge connector). Goldfinger contains many exposed copper pad, the copper pads in fact is a part of the PCB wiring . Typically connections, which we will insert a finger on the PCB appropriate slot on another piece of PCB ( commonly called slot Slot). In the computer, such as graphics card , sound card or other similar interface cards are connected to the motherboard through the finger .
Green or brown on the PCB is solder mask (solder mask) color. This layer is an insulating protective layer can protect the wire can be prevented from being welded to the part not the right place . In addition will be printed on the solder layer on the surface layer of screen printing (silk screen). Usually in it will be printed on text and symbols ( mostly white ) to mark the location of the parts on the board . Also referred to silkscreen icon plane (legend). Printed circuit board between the copper complex circuit components and parts , after careful planning neatly etched on a board , providing installation and interconnection of electronic components in the main support is an integral part of all electronic products the base part .
The printed circuit board by a flat plate made of non-conductive material , on this plate with pre-drilled holes often have design chips and other electronic components mounted . Components help make holes in the metal predefined path of the printed surface of the plate are connected electronically , the electronic component through the pin PCB, then adhesion of the conductive metal electrode is formed on the PCB circuit .
PCB applications can be classified according to their single- sided, double sided , multilayer and flexible four-layer board above board . In general , the more complex features of electronic products , the longer the loop distance , the more the number of contacts feet , also needed more PCB layers , such as high-end consumer electronics , information and communications products ; rather soft board is mainly applied to bend around products : such as notebook computers, cameras, cars and other instruments.
A brief history of the PCB
The basic concept of the printed circuit has been proposed in the patent at the beginning of this century, in 1947 the U.S. Bureau of Standards Aviation Administration and the U.S. launched the first printed circuit technology seminars, then lists 26 different method of manufacturing printed circuits. and summarized in six categories: coating method, a spray coating method, a chemical vapor deposition method, a vacuum evaporation method, a powder press molding method , and then these methods have failed to achieve large-scale industrial production , until the early age of fifty , the copper foil and . bonded laminate problem solved, stable and reliable performance copper clad laminate , and to achieve a large-scale industrial production , copper etching , PCB manufacturing technology into the mainstream , has been developed so far. sixties, metal hole double-sided and multilayer printed circuit board printed achieved mass production , collecting seven decades in LSI and the rapid development of computer and eighties to promote the rapid development of surface-mount technology and multi-chip assembly technology nineties PCB production technology continues to progress , the number of new materials, new equipment, new test instruments have emerged . printed circuit further surgery to produce high density, fine wire , multi-layer, high reliability, low cost and automated continuous the direction of the development of production .
China from the mid-1950s the development of single-sided PCB , first applied to the transistor radio in the sixties in the development of self-reliance of foil covered board substrate , so that the copper foil etching become China 's leading PCB production process . sixties has been able to produce large quantities of a single panel , small batch printed double-sided plated through hole and started to develop in a few units of plywood . seventies in the country to promote the etching pattern plating process , However, due to various disturbances , printed circuit special materials and special equipment not kept pace , the entire production technology lagged behind the international advanced level . the 1980s , due to the reform and opening up policy approved guidelines, not only with the introduction of a large number of foreign eighties advanced level of single-sided , double-sided , multi-layer printed circuit board production line, but after ten years of digestion, absorption , and rapid increase of China's printed circuit production technology.
Since 1990, Hong Kong, Taiwan and Japan, PCB manufacturers have come to our country to foreign joint ventures or wholly-owned factories , so that our PCB production yields soared, growing fast. 1995 China Printed Circuit Association conducted a national survey , a national survey of 459 printed circuit board production enterprises, including 128 state-owned enterprises , collective enterprises, 125 , 86 joint ventures , private 22 foreign enterprise 98 . Total PCB production reached 16.56 million square meters , of which 3.62 million square meters of double-sided , multilayer of 1.24 million square meters , with total sales of 90 billion yuan (about 1.1 billion U.S. dollars ) . America IPC Association data released China including Hong Kong 1994 sales of printed circuit $ 1.17 billion , accounting for 5.5% of the world total , ranking fourth in the world in production technology , due to the massive introduction of foreign advanced equipment and advanced production technology, greatly reducing the gap and abroad , has made great progress. However, China's PCB business mostly smaller, lower per capita sales and industrial labor productivity , low level of technology.
PCB use in the industry
Computers and peripherals: motherboards, monitors, network cards, memory cards, IC, mouse, router, camera, U disk, fan motor, game consoles, game card board (cheat sheet)
Mobile: Mobile plate, charger electronic anti-theft lock stereo, printers, copiers, fax machines, telephones, scanners, surveillance systems, video head DV, camera meter board
Automotive products: car stereo, air conditioning switch, LED lighting control system board (LCD monitors, LCD billboard) sensor various machines
Sanitary equipment: motors, controllers, switches as well as the high-end sector of the PCB board: such as medical equipment, military equipment, aerospace equipment, etc.
PCB Design
1. POWER PCB layers and the similarities and differences PROTEL
We do have a lot of design have more than using a software , because the characteristics of PROTEL easy to get started , after a lot of friends are the first school to learn PROTEL POWER, of course, there is a lot to learn directly POWER, there are two software used together . Due to some differences in these two software layer settings , the beginners are prone to confusion , so we first compare them together .
PROTEL positive MIDLAYER pure line layer
MIDLAYER hybrid electric layer ( containing lines, large copper )
Negative INTERNAL pure negative ( no segmentation, such as GND)
INTERNAL with inner partition ( the most common case of multi- power supply )
POWER
Multiply line layer of pure NO PLANE
NO PLANE hybrid electric layer ( copper with paved way COPPER POUR)
SPLIT / MIXED hybrid electric layer ( inner layer segmentation method PLACE AREA)
Negative CAM PLANE pure negative ( no segmentation, such as GND)
As can be seen from Table 1, POWER and PROTEL electrical layer can be divided into positive and negative film two properties , but these two types of layers contained in the layer properties is not the same .
(1). PROTEL only two types of layers , corresponding to positive and negative film properties. The POWER is different , POWER of positives divided into two types , NO PLANE and SPLIT / MIXED.
(2). PROTEL negative can be used in dividing the inner layer , only the negative- POWER pure negative ( not within the application layer partition , it is better PROTEL). Inner partition must use positive to do . By SPLIT / MIXED layer , can also be a common positive (NO PLANE) + Shop copper.
In other words, POWER PCB inner layer for power regardless of the division or hybrid electric layer should use positive to do , and the only difference between ordinary positives (NO PLANE) with a dedicated hybrid electric layer (SPLIT / MIXED) of Shop copper is not the way ! Only a single negative negative . ( Segmentation method using 2D LINE negative , because there is no network connectivity and design rule constraints , error-prone , not recommended ) .
The main difference between these two is that they are set up in layers and inner aspects of the division .
Shop differences copper SPLIT / MIXED layer segmentation and NO PLANE inner layer between the two .
(1) SPLIT / MIXED: You must use the inner split command (PLACE AREA), can automatically remove the inner separate pads , can trace , you can easily perform other network segmentation on a large copper inner split intelligent higher .
(2) NO PLANEC layers : copper shop must use the command (COPPER POUR), use the same outer lines will not automatically remove the separate pads , can trace , can not be done on other network segmentation chunks copper . That does not appear large copper surrounded by small copper phenomenon.
3. POWER PCB inner layer settings and segmentation methods have seen the future structure of the above should POWER layer structure has been very clear, determine what you want to use layers to complete the design , the next step is to add electrical layers of the operation.
Below a four-layer board as an example:
First, create a design netlist guide , complete the basic layout, and then add a layer SETUP-LAYER DEFINITION, in ELECTRICAL LAYER area , click MODIFY, enter 4 in the pop-up window, click OK. At this point in the middle of TOP and BOT 've got two new electrical layers, respectively, to name the two layers , and set the layer type. The INNER LAYER2 named GND, and is set to CAM PLANE, and then click ASSIGN distribution network on the right , because it is a whole layer of copper negatives , so you can assign a GND , do not division multiple network ! The INNER LAYER3 named POWER, and set to SPLIT / MIXED ( because multiple sets of power , so use the inner split ) , click ASSIGN, the need to go in the inner power distribution network to the right of the ASSOCIATED window ( assuming three power distribution network ) .
Next wiring , except for the outer completed all the power to the circuit . Power ground network to automatically connect directly to the inner perforated ( tips , first temporarily POWER layer type definition for CAM PLANE, so all of the power distribution network to the inner vias and hit line system will be considered already connected , and automatically canceled mouse line ) . Can be carried out after dividing the inner wiring are all completed. The first step is to network color, to distinguish between the various contacts in order to facilitate location of the shortcut keys CTRL + SHIFT + N, specify the network color ( omitted here ) .
Then layer the layer properties changed back POWER SPLIT / MIXED, then click DRAFTING-PLACE AREA, Next to draw copper to the first power supply network.
1 network ( yellow ) : the first network to spread across the board , and then specify the maximum size for the connection , the largest number of the network name.
2 network ( green ) : below the second network , pay attention because this network is located in the middle of the whole board , so we want to have a large paved surface cut out a piece of copper as the new network. Or click PLACE AREA, then follow the instructions to draw the color cutting area , double-click the mouse when the cut is completed , the system will automatically appear cut the current network ( 1 ) and the current network ( 2 ) of the regional isolation line ( because it is paved with positive copper the way to do the cutting , it is not as negative as do the cutting line with a positive side to complete a large copper division ) . While assigned to the network name.
3 network ( Red ) : The following third network , because the network closer to the plate edge , so we can also use another command to do it. Click DRAFTING-AUTO PLANE SEPARATE, then began to draw from from the plate edge , and then back after the contacts needed to surround plate edge , double-click the mouse to complete . Will also automatically appear isolation belt , and a pop-up window distribution network , requiring continuous attention to this window to assign two networks , one is you just cut out of the network , a network the remaining area ( there will be highlighted ) .
International PCB industry development
Currently, the global PCB industry accounted for a quarter of GDP over the electronic components industry , is the various industry segments in the electronic components industry, the largest proportion , scale up to $ 40 billion industry . Also, because of its unique position in the electronic -based industries , has become the industry's most active contemporary electronic components industry, 2003 and 2004 , global PCB output value is $ 34.4 billion , respectively, and $ 40.1 billion , representing growth rates of 5.27% and 16.47% .
Domestic PCB industry development :
Our PCB development work began in 1956 , 1963 to 1978 , and gradually expand to form the PCB industry . After 20 years of reform and opening up , due to the introduction of foreign advanced technology and equipment , single sided, double sided and multilayer boards have received rapid development of domestic PCB industry gradually developed from small to big . In 2002, China over Taiwan's PCB production value to become the third largest PCB production abroad . In 2003 , PCB production value and export volume are more than 6 billion U.S. dollars , becoming the world's second largest PCB production abroad . China's PCB industry maintained a rapid growth in recent years, about 20% , and is expected around 2010 surpassed Japan to become the world's largest PCB production value and technological development of the most active countries. From the yield components , the main products Chinese PCB industry has been by a single panel , double panel turned plywood , and is 6-8 or more layers to upgrade from 4 to 6 layers . With the rapid growth of multilayer , HDI boards, flex board , China's PCB industry structure is gradually optimized and improved. However, while China's PCB industry has made considerable progress, but compared with the advanced countries there is a large gap , the future is still a lot of improvement and upgrading of space . First, China has entered the PCB industry late, no special PCB R & D institutions in the number of new technology research and development capabilities and foreign manufacturers have a larger gap. Secondly, the product structure, still in the lower plate production -based, although the FPC, HDI and other growing rapidly, but due to the small base , the proportion is still not high . Once again, our PCB production equipment most dependent on imports , part of the core can only rely on imported raw materials , incomplete industry chain also hindered the development of domestic enterprises in the footsteps of PCB series .
PCB industry chain
According to the classification of the chain can be divided into raw materials - CCL - printed circuit boards - electronic applications , the relationship simply expressed as:
Fiberglass cloth : fiberglass cloth is one of the raw materials CCL , textile made from the glass fiber yarn , about 40% of the cost of the CCL ( thick ) and 25% ( thin ) . Glass fiber yarn by the silica sand and other raw materials in the kiln firing into a liquid through a very fine nozzle alloy pull into a fine glass fiber, fiberglass wrapped around the mountain and then hundreds of root fiberglass yarn. Kiln building huge investment, which normally takes millions of money, and once the ignition must be 24-hour production, the huge cost of entry and exit . Fiberglass cloth and weaving companies manufacturing the like , can be controlled by controlling the speed of the production capacity and quality , and specifications relatively simple and stable , almost did not change much on the specification since World War II . And different CCL, fiberglass cloth prices affected the relationship between supply and demand , price volatility in recent years between U.S. $ 0.50-1.00 / m. Currently produced in Taiwan and mainland China to account for about 70 % of the world .
Copper : copper is accounted for the largest proportion of the cost of raw materials, CCL , CCL costs about 30% ( thick ) and 50% ( thin ) , so copper 's price is the main driving force of CCL prices . Copper prices closely reflect changes in the price of copper , but the bargaining power is weak, with the recent rises in copper prices , copper manufacturers are struggling , many companies were forced to close down or merge , even CCL manufacturers to accept foil copper prices each vendor is still in widespread loss. As the price gap appeared , the first quarter of 2006 is likely to occur after wave of market prices , which could drive the CCL prices.
CCL : CCL is a fusion agent to epoxy fiberglass cloth and pressed together copper products , raw materials, direct PCB 's , after etching, plating , made of multilayer laminated printed circuit board. CCL industry capital demand is not high , is about 3000-4000 yuan , and can be discontinued at any time or converting. In the upstream and downstream industry chain structure , CCL strongest bargaining power , not only to have a strong voice in fiberglass cloth, copper and other raw materials procurement , and as long as the downstream demand is acceptable , you can pass the pressure of rising costs downstream PCB manufacturers. Three quarters of this year , CCL began to raise prices , price increases at around 5-8 % , the main driving force is a reflection of copper prices and lower demand CCL manufacturers can pass on price increases to digest the pressure . CCL world's second largest manufacturer in South Asia on December 15 also increased the prices , showing at least the first quarter of 2006, demand in the form of a good PCB .
Overall industry
As the most widely used electronic component products , PCB has a strong vitality. From a historical point of view , whether or cycle to determine the beginning of 2006 is the industry's climbing into the boom phase, continued strong downstream demand has been gradually pulling level on the PCB industry chain manufacturers shipments , formed in 2006 from the supply and demand relationship for at least in the first quarter , " is not short off " situation. The industry rating from " avoidance" upwards " good ."
PCB is the basic information of the electronic components industry , which belongs to the electronic components industry in the electronic components industry . Layers according to points , PCB into a single panel (SSB), double panel (DSB) and MLB (MLB); according to points softness , PCB into rigid printed circuit boards (RPC) and flexible printed circuit board ( FPC). In industrial research , in general, classified in accordance with the above-mentioned basic PCB product , PCB industry will be broken down into a single panel , double panel of six major segments , conventional multilayer, flexible board , HDI ( high density sintered ) board, package substrate , etc. industries.
PCB industry is a typical cyclical industry . From a historical point of view , the cycle is generally 7-8 years, but updated with the accelerated pace of downstream demand , and gradually reduced to about four years , the recent boom were the high point in 1995 , 2000 and 2004 . And memory products such as LCD panels and different , CCL 's price trend is mainly driven by the cost of raw materials , and PCB 's prices by supply and demand balance greater impact.
PCB board terminal concept
Applied to the printed circuit board electrical connections in the industry is becoming PCB terminals PCB terminals or connectors , used to achieve an electrical connection accessories .
PCB terminal classification
The current common market categories :
1 PCB Screw Terminal
2 Pluggable PCB Terminal Block , also known as male and female socket
3 Fixed PCB Terminal Block
4 PCB Spring Terminal
5 modular PCB terminal blocks
6 . Fence PCB terminals
PCB terminal board material
Metal : copper, steel
Plastic Material : PA66 , etc.
Plating: tin , zinc , etc.
PCB Terminal conventional spacing
Also known as pitch , 3.50mm/3.81mm/5.00mm/5.08mm/7.50mm/7.62
Terminals national identification standards
This standard is equivalent to international standards IEC455 (1988) " device -specific wire terminals and terminals alphanumeric identification system and application General ."
1 . Subject Matter and Scope
This standard provides a variety of methods to identify electrical equipment ( hereinafter referred to as device ) terminals , and developed a system to identify equipment alphanumeric terminals and specific wire line side of General. This standard applies to the identification mark of the combination of the terminal equipment ( such as resistors, fuses, relays, contactors, transformers, rotary motors, etc. ) , and these devices , but also to identify the specific wire line side . If necessary, these can be given to the General detailed application of certain products and the necessary supporting identification method in the relevant standard.
2 . Reference Standard
GB 4728 GB5465 Graphical symbols for electrical diagrams Graphical symbols for electrical equipment
3 . Recognition
One or more of the following may be used to identify a particular device terminals and wire terminals .
3.1 marking system using related products to determine the actual or relative location identification device terminals or specific wire line side .
3.2 using related products and identification marking system to identify specific equipment terminals and wire line side of the color marker .
3.3 using graphic symbols specified in GB5465 . For the use of auxiliary symbols, should be consistent with the GB4728 graphics.
3.4 This standard uses alphanumeric symbols prescribed in Chapter 5 .
About PCBway
Since 2003 PCBWAY has been the leading PCB quick turn manufacturer specializing in both Prototype and Production quantities, Initially produced single-sided and double-sided printed circuit boards for the consumer electronics market. PCBWAY is ranked among the top 4 board fabricators in asia and is well-known for its expedited turn time capabilities and its reliable best on-time shipping record.
Today, we have over 450 operators with high modern facilities to manufacture multi-layer PCB up to 12 layers. Backing up with a group of professional engineers, and well established quality system. PCBWay has grown to become a major PCB manufacturer in Asia to serve in diverse customers base such as electronics appliance, communication, educational electronics, power supplies, Automationsetc.
Our mission is to become one of leading PCB manufacturer that provide in high quality product with total customer satisfaction.
