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01 The main salt refers to the salt that can deposit the required coating metal on the cathode in the plating solution, which is used to provide metal ions. The main salt concentration in the bath must be in an appropriate range, and the increase or decrease of the main salt concentration will have an impact on the electrodeposition process and the final coating structure when other conditions remain unchanged. For example, the main salt concentration increases, the current efficiency increases, the metal deposition speed is accelerated, the coating grain is coarser, and the solution dispersion ability is reduced. 02 In some cases, if the metal ions of the main salt in the plating solution are simple ions, the plating grains are coarse, so the plating solution of complex ions should be used. The method of obtaining complex ions is to add a complex agent, that is, a substance that can complex metal ions of the main salt to form a complex. A complex is a "molecular compound" forme
PCB proofing production in the actual trial process, 90% of the gold plate can be replaced by gold plate, gold plate poor weldability is his fatal lack, but also led to many companies to give up the direct cause of gold plate! In the process of use, because of the small electrical conductivity of gold, it is widely used in contact roads, such as keyplate, goldfinger plate, etc., the most fundamental difference between gold-plated plate and gold-plated plate is that gold-plated is hard gold, heavy Gold is soft gold. What is gold deposition: through the chemical REDOX reaction method to generate a layer of coating, generally thicker, is a kind of chemical nickel gold deposit method, can reach a thicker gold layer, usually called gold deposition. 1, the crystal structure formed by gold plating and gold plating is not the same, the thickness of gold plating is much thicker than gold plating, gold plating will be gold more yellow than gold plating, customers are more satisfied. 2, t
(Printedcircuitboard, referred to as PCB) is a substrate for assembling electronic parts, is a printed board that forms point-to-point connections and printed components on a general substrate according to a predetermined design. The main function of the product is to make a variety of electronic components form a predetermined circuit connection, play the role of relay transmission, is the key electronic interconnection of electronic products. The manufacturing quality of printed circuit boards not only directly affects the reliability of electronic products, but also affects the overall competitiveness of system products, so printed circuit boards are known as "the mother of electronic system products." The development level of the printed circuit board industry can reflect the development speed and technical level of the electronics industry in a country or region to a certain extent. Glass fiber yarn: glass fiber yarn is calcined into liquid state by silica sand and other raw
Failure of other components on the PCB and causes pcb proofing manufacturers first from the mechanical load: including physical impact, vibration, filled particles on the silicon chip stress and inertia force. It is often heard during the design process that a stress action has damaged the device. For example, the device is too close to the edge of the plate, for example, the device is too close to the mounting copper column, for example, the device is too close to the crimping device, and so on, we know that the process of dividing the plate, installing the copper column and the process of crimping the device will have a stress effect, which will bring certain damage to the device. The PCB layout should also properly consider the impact of stress, in addition, in fact, the stress on the horizontal and vertical placement of the device is also different. Secondly, from the thermal load: including the high temperature when the chip binder curing, pre-heating before the lead bonding,
A recent PCB project has been proofing many times, and there are always one or two small chips on the PCB board that fail. Don't know what caused it? The hardware mason showed Dr. Yang the PCB board and told him where the specific small chip had failed. Dr. Yang replied: The location of the small chip is also on another half-moon orifice plate, and this half-moon orifice plate is designed and processed before. Look at the current PCB board, the half moon hole plate is placed on the top layer of the PCB board, and the heavier patch device is placed at the bottom of the board. Seeing here, it will involve the problem that this small chip has passed the reflux furnace many times. Originally, this small chip has passed the reflux furnace once when it is on the half-moon orifice plate, because it is considered to avoid the occurrence of the failure of the heavy device in the second reflux of the plate. The SMT plant may prefer to reflow weld the top layer device first, and then paste t
The difference between positive and negative PCBs PCB positive and negative are manufacturing processes with opposite final effects. The effect of PCB positive: The copper on the printed board is retained in areas where lines are drawn, and the copper on areas where no lines are drawn is removed. The signal layer, such as the top and bottom layers, is the positive. The effect of PCB negative film: The copper coating on the printed board is removed in areas where lines are drawn, while the copper coating is retained in areas where no lines are drawn. The Internal Planes layer (referred to as the Internal Planes layer) is used to arrange power and ground wires. The wiring or other objects placed on these layers are copper free areas, meaning that this working layer is negative. Negative film is used to reduce file size and computational complexity. The areas with copper are not displayed, while the areas without copper are displayed. This can significantly reduce data volume and co
Penetration occurs during dry film electroplating The reason for infiltration plating is that the adhesion between the dry film and the copper-clad foil is not strong, causing the plating solution to penetrate deeply and causing the "negative phase" part of the coating to become thicker. Most PCB manufacturers experience infiltration plating due to the following reasons 1. Exposure energy is too high or too low Under UV irradiation, the photoinitiator that has absorbed light energy decomposes into free radicals to initiate monomer photopolymerization reactions, forming body shaped molecules that are insoluble in dilute alkali solutions. When the exposure is insufficient, due to incomplete polymerization, the adhesive film swells and becomes soft during the development process, resulting in unclear lines and even film layer detachment, resulting in poor adhesion between the film and copper; If the exposure is excessive, it will cause difficulties in development and also cause warpi
PCB layout design rules check? (1) Whether the distance between wire and wire, wire and component pad, wire and through hole, component pad and through hole, through hole and through hole is reasonable, and whether it meets the production requirements. (2) Whether the width of the power line and the ground line is appropriate, whether the power supply and the ground line are tightly coupled (low wave impedance), and whether there is a place in the PCB board where the ground line can be widened. (3) Whether the best measures are taken for the key signal lines, such as the shortest length, the protection line, the input line and the output line are clearly separated. (4) Whether the analog circuit and the digital circuit part have their own independent ground lines. (5) Whether the graphics (such as ICONS, marking) added to the PCB board will cause signal short circuit. Modify some undesirable lines.
1, filtering effect, in the power supply circuit, the rectifier circuit will turn the AC into a pulsating DC, and after the rectifier circuit is connected to a large-capacity electrolytic capacitor, using its charge and discharge characteristics (energy storage), so that the pulsating DC voltage after rectification becomes a relatively stable DC voltage. In practice, in order to prevent the power supply voltage of each part of the circuit from changing due to load changes, the output end of the power supply and the power input end of the load are generally connected with tens to hundreds of micromethods of electrolytic capacitors. Because the large-capacity electrolytic capacitor generally has a certain inductance, the high-frequency and pulse interference signals can not be effectively filtered out, so a capacitor with a capacity of 0.001-0.lPF is connected in parallel at both ends to filter out the high-frequency and pulse interference. 2, coupling: In the transmission and ampli
Several common problems in PCB design 1. Overlap of pad 1, the overlap of the pad (except the surface of the pad) means the overlap of the hole, and the drilling process will break the drill bit because of multiple drilling in one place, resulting in hole damage. 2, the two holes in the multi-layer plate overlap, such as a hole position for the isolation plate, the other hole position for the connection plate (welding plate), so that the film is drawn as the isolation plate, resulting in scrap. Second, the abuse of graphics layer 1, made some useless connections on some graphic layers, originally was a four-layer board but designed more than five layers of the line, causing misunderstanding. 2, the design diagram is easy, take Protel software as an example, all the lines are drawn with the Board layer, and the Board layer is used to mark the line, so in the light drawing data, because the Board layer is not selected, the connection is missed and the circuit is broken, or the Bo
1. Engineering design: interlayer semi-cured sheet arrangement response; Multi-layer core plate and semi-cured sheet should use the same supplier's product; The graphic area of the outer C/S plane is as close as possible, and an independent grid can be used; 2. Bake the board before cutting Generally 150 degrees 6-10 hours, remove water vapor in the plate, further cure the resin completely, eliminate the stress in the plate; Drying board before opening, both inner and double sides are needed! 3. Before laminating the multilayer plate, pay attention to the longitude and latitude direction of the curing plate: The proportion of warp and weft contraction is not the same, and pay attention to distinguish the warp and weft direction before laminating the semi-cured sheet; The core plate should also pay attention to the warp and weft direction when cutting; Generally, the direction of the plate curing sheet is meridional. The long direction of the copper-clad plate is meridional;
How is pyrolysis technology applied in circuit boards As an efficient means of waste treatment and recycling, pyrolysis technology can play an important role in the recycling of waste circuit boards. With the further research on the basic theory of pyrolysis technology and the development of pyrolysis equipment, it will become one of the most important methods for recycling circuit boards in waste electrical and electronic equipment in the future. Although the measurement of bromine-containing products in the pyrolysis of circuit boards is limited to qualitative analysis or based on the analysis of the total amount of bromine elements, precise quantitative analysis and detection of specific bromine-containing substances cannot be achieved, so it cannot provide enough complete information to determine the transformation and migration rules of bromine-containing flame retardants in the pyrolysis process. However, many researchers have carried out some attempts to remove brominated p
The method of rational layout of components in PCB design First, beauty should not only consider the orderly placement of components, but also consider the beautiful flow of the line. Because the general layman sometimes more emphasis on the former, in order to one-sided evaluation of the advantages and disadvantages of circuit design, in order to the image of the product, the former should be given priority when the performance requirements are not harsh. However, in high-performance occasions, if you have to use dual panels, but also packaged in the inside, usually can not see, you should prioritize the beauty of the line. Second, the force circuit board should be able to withstand various external forces and vibrations during installation and work. Therefore, the circuit board should have a reasonable shape, and the positions of various holes (screw holes, special-shaped holes) on the board should be reasonably arranged. Generally, the distance between the hole and the edge of
Electromagnetic compatibility design in PCB circuits Once electrostatic discharge occurs, it should be bypassed as soon as possible, and do not directly invade the internal circuit. For example, if the internal circuit is shielded by a metal chassis, the chassis should be well grounded, and the grounding resistance should be as small as possible, so that the discharge current can flow into the ground from the outer chassis, and the disturbance caused by the discharge of surrounding objects can also be imported into the ground, without affecting the internal circuit. For a metal chassis, the circuits in the chassis are grounded through I/O cables and power cables. When electrostatic discharge occurs on the chassis, the potential of the chassis increases, but the potential of the internal circuits is kept near the ground potential due to grounding. At this time, there is a large potential difference between the chassis and the circuit. This causes a secondary arc between the chassis a
PCB Cable design A properly designed cable protection system may be the key to improving the system's ESD non-susceptibility. As the largest "antenna" in most systems - I/O cables are particularly susceptible to ESD interference that induces large voltages or currents. On the other hand, the cable also provides a low impedance channel to ESD interference if the cable shield is connected to the housing. Through this channel, ESD interference energy can be released from the system grounding loop, thus avoiding conductive coupling indirectly. In order to reduce ESD interference radiation coupling to the cable, the line length and loop area should be reduced, common mode coupling should be suppressed and metal shielding should be used. For input/output cables, shielding cables, common mode chokes, overvoltage clamp circuits, and cable bypass filters can be used. At both ends of the cable, the cable shield must be connected to the housing shield. Installing a common mode choke on the int
PCB copper-platinum treatment Because the current IC working clock (digital IC) is getting higher and higher, its signal for the width of the line put forward certain requirements, the line width (copper platinum) is good for low frequency strong current, but for high frequency signal and data line signal, it is not the case, the data signal is more synchronization, high frequency signal is affected by skin effect. Therefore, the high-frequency signal should be thin and not wide, and should be short and not long, which involves the layout problem (the coupling of signals between devices), which can reduce the induced electromagnetic interference. The data signal, however, appears on the circuit in the form of pulse, and its higher harmonic content is the decisive factor to ensure the correctness of the signal. The same wide copper platinum will have a skin effect on high speed data signals (distributed capacitance/inductance increases), which will lead to signal deterioration, data
PCB layout/wiring, impact on electrical performance Digital ground cables should be separated from analog ground cables. This has a certain degree of difficulty in practice. To develop a better board, you first have to understand the electrical aspects of the IC you are using, which pins will produce high order harmonics (digital signals or the rise/fall edge of the switching square wave signal), which pins are susceptible to electromagnetic interference, the signal block diagram (signal processing unit block diagram) inside the IC helps us understand. The layout of the whole machine is the first condition to determine the electrical performance, and the layout of the board is more to consider the direction or process of the signal/data between the IC, the big principle is easy to produce electromagnetic radiation as close to the power part as possible; The weak signal processing part is mostly determined by the overall structure of the equipment (that is, the overall planning of t
Some feasible processes for PCB production First, the line 1. Minimum line width: 6mil (0.153mm). That is to say, if the line width is less than 6mil, it will not be produced, (the minimum line width distance of the inner layer of the multi-layer board is 8MIL) If the design conditions permit, the larger the design, the better the line width, the better the factory production, the higher the yield, the general design routine is about 10mil, this point is very important, the design must be considered. 2. Minimum line distance: 6mil (0.153mm).. The minimum line distance, that is, the line to the line, the distance from the line to the pad is not less than 6mil from the production point of view, the bigger the better, the general practice in 10mil, of course, the design conditions, the bigger the better this point is very important, the design must be considered. 3.Line to contour line spacing 0.508mm(20mil) Two, via holes (commonly known as conductive holes) 1. Minimum aperture :
The main factors to be considered in the mechanical design of printed circuit boards 1) The best panel size suitable for printed circuit board production; 2) Location of panel mounting holes, brackets, splints, clamps, shielding boxes and radiators; 3) Suitable fixed devices for heavier components; 4) Suitable aperture for component installation; 5) The assembled circuit board should have pressure resistance and shock resistance during transportation; 6) The assembly method of the circuit board (vertical installation/horizontal installation); 7) Cooling method; 8) Special placement requirements for components, similar to those operating on the front panel, such as buttons, rheostat, etc. Steps of PCB layout design Before the layout design begins, a complete and detailed description of the circuit is needed, mainly including the following aspects: 1) Schematic diagram, including details of components, connections and specifications of edge connectors. 2) Component list, in
The aperture of pad in circuit board manufacturing design is discussed Test pads must be provided for all nodes in accordance with ANSI/IPC 2221 requirements. A node is an electrical connection point between two or more components. A test pad requires a signal name (node signal name), an x-y axis related to the reference point of the printed circuit board, and the coordinate position of the test pad (indicating which side of the printed circuit board the test pad is located on). Mounting information is required for the SMT, and thermobonding technology for the PCB assembly layout is also required to promote testability in the circuit with the help of "in-circuit test fixtures" or what is commonly referred to as "nail bed fixtures". To achieve this, it is necessary to: 1) The diameter of the test pad specially used for detection should not be less than 0.9mm. 2) The space around the test pad should be greater than 0.6mm and less than 5mm. If the height of the component is greater t
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