PCB printing, also known as a printed circuit board , is today very developed a new industry, and the rapid development of screen printing has injected vitality into the industry , to bring a major change in the electronics industry . The current screen printing process is fully able to adapt to high-density PCB production .
Introduction
CB is in English (PrintedCircuieBoard) PCBs for short. Usually on the insulating material , according to predetermined design , made of printed circuits, printing member or a combination of both conductive patterns called printed circuits. Providing electrical connection between the conductive pattern on the insulating base material components , referred to as printed wiring . This put printed circuit or printed circuit board called the finished printed circuit boards , also known as PCB or printed circuit board.
Application
We can see almost all electronic equipment without it , small electronic watches, calculators , general computer , large computers, electronic communication equipment, military weapon systems , as long as there is no integrated circuits and other electronic devices, among them electrical interconnects to be used in PCB. It provides an integrated circuit and other electronic components of the mechanical support fixed assembly , achieve various integrated circuits and other electronic components and electrical connections between the wiring or electrical insulation, to provide the desired electrical characteristics , such as characteristic impedance . While providing for the automatic soldering solder graphics ; Cartridge for the components , inspection, maintenance provide identification characters and graphics.
How PCB Manufacturing
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 .
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 .
Production process
Production process is usually one-sided , double-sided PCB and multilayer general , in deepening its understanding.
Sided Rigid PCB : Single CCL --- Cutting --- ( washing, drying ) --- drilling or punching --- screen printing line anti- etched graphics or use dry cured inspection --- repair etched copper plate --- India --- to resist material , drying --- scrub , dry --- screen printing solder graphics ( common green oil ), UV -curable screen printing characters --- mark graphics , UV curing --- preheating, punching and shape --- electrical open circuit test --- washing, drying --- pre-coated anti -oxidant flux (dry ) or HAL HASL --- test packaging --- finished product .
Sided Rigid PCB : double CCL --- Cutting --- pack --- CNC drilling vias --- inspection , deburring brushing --- plating ( metal vias ) - - ( full plate thin copper plating ) --- --- scrub test negative circuit pattern screen printing and curing ( dry or wet film , exposure, development ) --- test pattern plating line repair plate --- tin plating ( resist Ni / Au ) --- to printed materials ( photographic film ) --- etched copper --- ( stripping ) --- cleaning brush --- graphics Screen Printing solder used thermal curing green oil ( Post a photosensitive dry film or wet film , exposure, development , heat curing , thermal curing of the photosensitive green oil used ) --- clean , dry screen printing mark character pattern --- cured --- ( spray -welding film or an organic tin ) --- contouring → washing, drying --- electrical continuity test to detect --- packing --- finished product .
Manufacturing method of the through hole metallization process --- multilayer inner open-sided copper-clad material brushing --- positioning hole drilled paste dry film photoresist or a photoresist -coated --- exposure --- development --- etching and stripping --- inner coarsening, go check --- oxide --- inner (outer sided CCL production lines , B- stage adhesive sheet , plate bonding sheet inspection , drilling positioning holes ) --- laminating --- number of control --- hole drilling holes checked before treatment with copper plating --- All --- plated thin copper plate coated check --- posted photoluminescence dry plating or coating resistant to light-induced plating agent --- resistant floor surface exposure --- development , repair the line graphics board --- plated tin-lead alloy plating or nickel / gold --- plated to film and etching --- check --- screen printing solder solder graphics or photo- printed graphics --- character graphics --- ( hot air solder leveling or organic protection film ) --- NC wash appearance --- washing, drying --- electrical --- finished off detection check --- packaging factory.
As can be seen from the flow chart multilayer technology is developed from the dual face metallization process basis. Following a two-sided process which in addition , there are several unique content : metal interconnect inner hole , drill and epoxy to smear , positioning systems , laminating, special materials.
The most common computer boards are basically epoxy glass cloth -sided printed circuit boards , which side is the other side of the cartridge element for the component foot welding surface , can be seen very spot the rules of these joints foot discrete components soldered to the pad surface we call it . Why do not other copper conductor patterns on the tin it . Because in addition to the need of soldering pads and other parts of the rest of the surface layer of resistance to soldering the solder mask . Most of its surface is green solder mask , there are a few in yellow , black, blue and so on , so the solder PCB oil industry is often called a green oil . Its role is to prevent the occurrence of a bridge phenomenon wave soldering , welding quality and economical effects such as solder . It is also a permanent protective layer PCB , can play moisture, corrosion , mildew , and mechanical abrasion and so on. From the outside , the surface is smooth and bright green solder mask for photographic film on the plate heat curing green oil . Not only look more attractive, it is important that their pads higher accuracy , thus improving the reliability of solder joints .
We can see from the computer boards, there are three ways to install the components . One is inserted into the drive installation process, the electronic component inserted in the printed circuit board vias . This double-sided printed wiring board is easy to see that there are several vias : First the simple insertion hole element ; two insertion elements are interconnected with vias duplex ; three -sided guide is a simple through Hole ; fourth hole board mounting and positioning . Another way is to install two kinds of surface mount and chip installed directly. In fact, the chip technology can be considered to be directly mounted branch of surface mount technology , which is directly bonded to the chip on the PCB , and then wire bonding method or carrier tape method, flip-chip , beam lead method interconnect packaging technologies to India system board. The welding surface on the component surface.
Surface Mount Technology Advantages
1 ) Due to the elimination of a large number of large PCB vias or buried vias interconnect technology improves wiring density on the PCB , reducing PCB area ( typically one-third -order plug-in installed ) , while can reduce the cost of design and PCB layers .
2 ) reduce the weight and improve the seismic performance , using a colloidal solder and new welding technology , improve product quality and reliability.
3 ) Since the wiring density increases and shorter lead lengths , reducing the parasitic capacitance and inductance, more conducive to improving the PCB electrical parameters .
4 ) than the cartridge installation easier to automate , improve the speed of installation and labor productivity , the corresponding lower assembly costs.
Circuit board technology is improving and improving and the surface of the chip packaging technology with the installation of improved technology. Now we look at the sticky surface mounted computer board rates are constantly on the rise. In fact this is the circuit board and then the transmission line screen printing graphic is unable to meet the technical requirements . So ordinary high precision circuit boards, solder its line graphics and graphic lines and light-sensitive photoreceptor basically green oil production process.
Trends
Circuit board production have become increasingly demanding , more and more new technologies used in circuit board production , such as laser technology , the photosensitive resin and so on. These are just some of the superficial presentation , circuit board production surface there are many things because of space limitations did not specify , such as blind and buried vias , around the plates , Teflon plate , lithography technologies.
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