PCBA details daquan

PCBA is the abbreviation of English Printed Circuit Board +Assembly, that is to say, the whole process of PCB blank through SMT loading or DIP plug-in program, which is called PCBA for short. This is a common writing method in China, while the standard writing method in Europe and America is PCB'A with "'",which is called official idiom. Basic introduction Chinese name: PCBA mbth: Printed Circuit Board +Assembly process: PCB blank board is mounted by SMT or DIP plug-in program essence: manufacturing process substrate: bakelite board, glass fiber board metal coating: copper-tin-gold-nickel circuit board, development history, practicality, scope, new project, Base material, metal coating, circuit design, basic fabrication, introduction, subtraction method, additive process, lamination method, ALIVH, production mode, introduction, DIP, industrial status, introduction, North America, Japan, Taiwan Province, transfer to China, application, introduction, smart phone, touch panel, computer, e-book, digital camera, LCD TV, LED lighting, future trend. PCB(Printed circuit board), which is commonly used in English, is an important electronic component, a supporter of electronic components and a provider of circuit connection of electronic components. Because it is made by electronic printing technology, it is called "printed" circuit board. Before the appearance of printed circuit board, the interconnection between electronic components depended on the direct connection of wires to form a complete circuit. Now, the circuit bread board only exists as an effective experimental tool, and the printed circuit board has become an absolute dominant position in the electronic industry. At the beginning of the 2th century, in order to simplify the manufacture of electronic machines, reduce the wiring between electronic parts and reduce the manufacturing cost, people began to study the method of replacing wiring by printing. In the past 3 years, engineers have constantly proposed to use metal conductors as wiring on insulated substrates. The most successful is that in 1925, Charles Ducas of the United States printed circuit patterns on an insulated substrate, and then successfully established conductors for wiring by electroplating. [1] Until 1936, Austrian Paul Eisler published the foil technology in Britain, and he used printed circuit boards in a radio device; In Japan, Hayosuke Miyamoto successfully applied for a patent by spraying the wiring method "メタリコンン blowing the wiring method (Patent No.119384)". [2] Paul Eisler's method is the most similar to the current printed circuit board. This kind of practice is called subtraction method, which removes unnecessary metals; The method of Charles Ducas and Hayashi Miyamoto is to add only the required wiring, which is called additive process. Even so, because of the high calorific value of electronic parts at that time, the substrates of the two were difficult to be used together, so there was no formal practical work, but it also made the printed circuit technology further. History of development In 1941, the United States painted talc with copper paste for wiring to make proximity fuse. In 1943, Americans used this technology extensively in military radios. In 1947, epoxy resin began to be used to manufacture substrates. At the same time, NBS began to study the manufacturing technology of coils, capacitors and resistors formed by printed circuit technology. In 1948, the United States officially recognized the invention for commercial use. Since 195s, transistors with low calorific value have largely replaced vacuum tubes, and printed circuit board technology has been widely adopted. At that time, etching foil technology was the mainstream [1]. In 195, Japan used silver paint as wiring on glass substrates; And copper foil is used as wiring on a paper phenolic substrate (CCL) made of phenolic resin. [1] In 1951, the appearance of polyimide further improved the heat resistance of resin, and a polyimide substrate was also manufactured. [1] In 1953, Motorola developed a double-panel electroplating through-hole method. This method is also applied to the later multilayer circuit board. [1] Printed circuit boards were widely used for 1 years, and their technology became more and more mature in the 196s. Since Motorola's double-panel appeared, multi-layer printed circuit boards began to appear, which made the ratio of wiring to substrate area even higher. In 196, V. Dahlgreen made a flexible printed circuit board by sticking a metal foil film printed with a circuit to a thermoplastic plastic. [1] In 1961, Hazeltine Corporation of the United States made a multilayer board with reference to the electroplating through-hole method. [1] In 1967, the "Plated-up technology", one of the storey-adding methods, was published. [1] [3] In 1969, FD-R made a flexible printed circuit board with polyimide. [1] In 1979, Pactel published the "Pactel method", which is one of the methods of adding layers. [1] In 1984, NTT developed the "Copper Polyimide method" for thin film circuits. [1] In 1988, Siemens Company developed the additional layer printed circuit board of Microwiring Substrate. [1] In 199, IBM developed a layer-increasing printed circuit board (SLC). [1] In 1995, Panasonic developed ALIVH's multilayer printed circuit board. [1] In 1996, Toshiba developed B2it multilayer printed circuit board. [1] Practicality At the end of 199s, when many schemes of adding layer printed circuit boards were put forward, adding layer printed circuit boards were formally put into practice in large quantities, until now. It is important to develop a robust test strategy for large-scale and high-density printed circuit board assembly (PCBA) to ensure the conformity and function with the design. In addition to the establishment and testing of these complex assemblies, the money invested in electronic parts alone may be high-it may reach $25, when a unit is finally tested. Because of such high cost, the problem of finding and repairing assembly is now an even more important step than it used to be. Today's more complex assembly is about 18 square inches, with 18 floors; There are more than 29 components on the top and bottom; Contains 6 circuit nodes; There are more than 2, welds to be tested. The scope is in Lucent's accelerated manufacturing plant (N. Andover, MA), manufacturing and testing art-class PCBA and complete transmission system. Assemblies with more than 5 nodes are a concern for us, because they are close to the resource limit of our existing ICT, in circuit test) equipment (Figure 1). We now manufacture about 8 different PCBA or "nodes". Among these 8 kinds of nodes, about 2 kinds are in the range of 5~6 nodes. However, this number has increased rapidly. New projects New development projects require more complex, larger PCBA and tighter packaging. These requirements challenge our ability to build and test these units. Furthermore, larger circuit boards with smaller components and higher number of nodes may continue. For example, a design that is drawing a circuit board diagram now has about 116, nodes, more than 5,1 components and more than 37,8 solder joints that need to be tested or confirmed. This unit also has BGA on the top and bottom, and BGA is followed. Using the traditional needle bed to test this size and complexity of the board, ICT is impossible. In manufacturing process, especially in testing, the increasing complexity and density of PCBA is not a new problem. Realizing that increasing the number of test pins in ICT test fixture is not the direction to go, we began to observe alternative circuit verification methods. Seeing the number of non-contact probes per million, we found that at 5 nodes, many errors (less than 31) may be due to probe contact problems rather than actual manufacturing defects (Table 1). Therefore, we set about reducing the number of test needles, not increasing them. Nevertheless, the quality of our manufacturing process is evaluated to the whole PCBA. We decided that the combination of traditional ICT and X-ray layering is a feasible solution. Substrate Substrate is generally classified by the insulating part of the substrate. The common raw materials are bakelite, glass fiber board and various plastic boards. PCB manufacturers generally use an insulating part composed of glass fiber, nonwoven fabric and resin, and then press it into a "preg" with epoxy resin and copper foil. The common substrates and main components are: FR-1-phenolic cotton paper, which is commonly called bakelite (more economical than FR-2) FR-2-phenolic cotton paper. FR-3 Cotton paper, epoxy resin FR-4 Woven glass, epoxy resin FR-5 glass cloth, epoxy resin FR-6 frosted glass, polyester G-1 glass cloth, epoxy resin CEM-1 cotton paper and epoxy resin (flame retardant). Epoxy resin (non-flame-retardant) CEM-3-glass cloth, epoxy resin CEM-4-glass cloth, epoxy resin CEM-5-glass cloth, polybasic ester ain-aluminum nitride sic-silicon carbide metal coating is not only the wiring on the substrate, but also the place where the circuit of the substrate is soldered with electronic components. In addition, different metals also have different prices, which will directly affect the production cost; Different metals also have different solderability and contact, and also have different resistance values, which will directly affect the performance of components. Commonly used metal coatings are: the thickness of copper and tin is usually 5-15μm[4] Lead-tin alloy (or tin-copper alloy), that is, solder, the thickness is usually 5-25μm, and the content of tin is about 63%[4] Gold is generally only plated on the interface [4] Silver is generally only plated on the interface, or the printed circuit board is designed with an alloy circuit that is also silver as a whole. The design is based on the electronic circuit diagram to realize the functions required by circuit users. The design of printed circuit board mainly refers to layout design, which requires various factors such as internal electronic components, metal wiring, layout of through holes and external wiring, electromagnetic protection, heat dissipation, crosstalk and so on. Excellent circuit design can save production costs and achieve good circuit performance and heat dissipation performance. Simple layout design can be achieved by hand, but complex circuit design generally needs the help of computer-aided design (CAD), and famous design software includes Protel, OrCAD, PowerPCB, FreePCB and so on. According to different technologies, the basic production introduction can be divided into two categories: elimination and addition. Subtractive method is to use chemicals or machinery to remove unnecessary places on a blank circuit board (that is, a circuit board covered with a whole piece of metal foil), and the rest is convenient for the needed circuit. Screen printing: make the pre-designed circuit diagram into a screen mask, and the unnecessary circuit parts on the screen will be covered by wax or impermeable materials, then put the screen mask on the blank circuit board, oil the screen with a protective agent that will not corrode, put the circuit board in an corrosive solution, and the parts that are not covered by the protective agent will be corroded away, and finally clean the protective agent. Photosensitive board: Make the pre-designed circuit diagram on a transparent film mask (the simplest way is to print the slides with a printer), and then print the required parts into opaque colors, and then coat the blank circuit board with photosensitive pigments. Put the prepared film mask on the circuit board and irradiate it with strong light for several minutes. After removing the mask, use a developer to display the patterns on the circuit board, and finally corrode the circuit like screen printing. Engraving: use milling machine or laser engraving machine to directly remove the unnecessary parts on the blank circuit. In Additive process, additive process, photoresist (D/F) is generally covered on a substrate plated with thin copper in advance, which is exposed by ultraviolet light and then developed to expose the required places. Then, the copper thickness of the official circuit on the circuit board is thickened to the required specifications by electroplating, and then a layer of metal thin tin is plated. Finally, the photoresist is removed (this process is called stripping), and the copper foil layer under the photoresist is etched away. Lamination method [1] Lamination method is one of the methods for manufacturing multilayer printed circuit boards. The outer layer is wrapped after the inner layer is made, and then the outer layer is processed by subtraction or additive process. Repeatedly repeating the operation of the lamination method, a multilayer printed circuit board can be obtained, while the sequential lamination method is used. The inner layer is laminated (that is, the action of bonding different layers), and the lamination is completed (the outer layer containing metal foil film is subtracted; Additive process) Drilling Subtraction Panel Electroplating The whole PCB is electroplated with a resist layer at the place where the surface is to be reserved. The Pattern electroplating method removes the barrier layer by etching to prevent it from being etched. The required surface is electroplated to a certain thickness. The barrier layer is removed by etching until the unnecessary metal foil film disappears. additive process makes the surface rough completely. additive process (full-additive) adds the barrier layer where the conductor is not needed to form a circuit part additive process (semi) without electrolytic copper. -additive) Cover the whole PCB with electroless copper, add a barrier layer where there is no conductor, remove the barrier layer by electrolytic copper plating, and etch until the electroless copper disappears under the barrier layer. The layer-adding method is one of the methods for manufacturing multilayer printed circuit boards, as the name implies, adding printed circuit boards layer by layer. Each layer is processed to the required shape. Alivh [1] Alivh (any layer intermittent via hole, Any Layer IVA) is a layer adding technology developed by Matsushita Electric. This is based on Aramid fiber cloth. Immerse fiber cloth in epoxy resin to become a "preg" laser drilling hole, fill conductive paste in the outer layer and stick copper foil to make circuit pattern by etching, and stick the semi-finished product in the second step on the copper foil to build it up, and then repeat the fifth to seventh steps until B2IT [1] B2IT (Buried Bump Interconnection Technology) is a build-up technology developed by Toshiba. Firstly, make a double-faced or multi-layered board, print conical silver paste on copper foil, put an adhesive sheet on the silver paste, and make it