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The significance and design difficulties of PCB copper coating The significance of copper coating is to reduce the impedance of the ground wire and improve its anti-interference ability; Reduce voltage drop and improve power efficiency; Connected to the ground wire, it can also reduce the loop area. For the purpose of minimizing deformation during PCB soldering, most PCB manufacturers also require PCB designers to fill open areas with copper sheets or grid like ground wires. If copper plating is not handled properly, it will not be worth the loss. Is copper plating "more beneficial than harmful" or "more harmful than beneficial"? Everyone knows that in high-frequency situations, the distributed capacitance of the wiring on the printed circuit board will play a role. When the length is greater than 1/20 of the corresponding wavelength of the noise frequency, an antenna effect will be generated, and noise will be emitted outward through the wiring. If there is a poorly grounded coppe
Complete Collection of PCB Failure Analysis Technologies 1. Appearance inspection Appearance inspection is the visual inspection or use of some simple instruments, such as stereomicroscope, metallographic microscope, or even magnifying glass, to examine the appearance of a PCB, find the location of failure and related physical evidence. Its main function is to locate the failure and preliminarily determine the failure mode of the PCB. The appearance inspection mainly checks the contamination, corrosion, location of bursting boards, circuit wiring, and regularity of failure of PCBs. If it is a batch or individual, whether it is always concentrated in a certain area, etc. In addition, many PCBs fail only after being assembled into PCBA, and it is necessary to carefully examine the characteristics of the failure area to determine whether it is caused by the influence of the assembly process and the materials used in the process. 2. X-ray fluoroscopy examination For certain areas tha
During the processing of PCB circuit boards, it is inevitable to encounter several defective products, which may be caused by machine errors or human factors. For example, sometimes there may be an abnormal situation called hole breakage, and the cause needs to be analyzed in detail. If the state of hole breakage is a point like distribution rather than a complete circuit breaking phenomenon, it is called point like hole breakage, and some people also call it "wedge shaped hole breakage". The common causes are due to poor processing of the adhesive residue removal process. During the PCB circuit board processing, the process of removing adhesive residue will first undergo a loosening agent treatment, followed by a strong oxidizing agent "permanganate" erosion operation. This process will remove adhesive residue and produce microporous structures. After the removal process, the remaining oxidant is removed by reducing agents, and a typical formula uses acidic liquid treatment. Due
Making a PCB board is not simply about following the process to complete the board. Just drill a hole and add the components. The production of PCBs is not difficult, but the difficulty lies in troubleshooting after completion. Whether it's a personal enthusiast or an industry engineer, encountering problems while debugging PCB circuit boards can be quite a headache, just like programmers encountering bugs. Some people have a strong interest in debugging PCB circuit boards, just like programmers solving bugs. There are many common PCB circuit board problems, including circuit board design, damage to electronic components, short circuits, component quality, and PCB circuit board wire breakage. The common PCB circuit board faults are mainly concentrated on components such as capacitors, resistors, inductors, diodes, transistors, field-effect transistors, etc. The obvious damage to integrated chips and crystal oscillators can be visually observed to determine the faults of these com
PCB sinking gold plate vs gold-plated plate In fact, there are two types of gold plating processes: electroplating gold and sinking gold. For the gold plating process, the effect of tin plating is greatly reduced, while the effect of tin plating on sinking gold is relatively better; Unless the manufacturer requires binding, most manufacturers now choose the sinking gold process! In general, the surface treatment of PCBs can be divided into the following types: gold plating (electroplating gold, sinking gold), silver plating, OSP, tin spraying (with and without lead). These are mainly aimed at FR-4 or CEM-3 boards, and paper substrates also have surface treatment methods coated with rosin; If we exclude the production and material process reasons of solder paste and other SMT manufacturers, we can discuss the issue of poor soldering (poor soldering). Here, we will only address the PCB issue, and there are several reasons for this: 1. During PCB printing, is there an oil leakage fi
Common problems and solutions for alkaline etching of circuit boards 1. Problem: Decreased etching rate in printed circuits Reason: Caused by improper control of process parameters Solution: Inspect and adjust process parameters such as temperature, spray pressure, solution density, pH value, and ammonium chloride content to the specified values according to process requirements. 2. Problem: Deposition of etching solution in printed circuits Reason: (1) The ammonia content is too low (2) Excessive water dilution (3) The specific gravity of the solution is too high Solution: (1) Adjust the pH value to reach the process specified value or appropriately reduce the exhaust volume. (2) Strictly follow the process requirements or reduce the exhaust volume appropriately during adjustment. (3) According to the process requirements, a portion of the solution with high specific gravity is discharged and analyzed, and then an aqueous solution of ammonium chloride and ammonia is ad
PCB causes some factors of poor surface quality 1. Substrate processing problems: Especially for some thinner substrates (generally below 0.8mm), because the substrate rigidity is poor, it is not appropriate to brush the board. This sample may not be able to effectively remove the protective layer specially treated to prevent the oxidation of copper foil on the surface of the substrate during the production and processing process, although the layer is thin and the brush board is easier to remove, but the chemical treatment is more difficult, so it is important to pay attention to control in the production and processing, so as to avoid the foaming problem caused by the poor bonding force between the copper foil on the substrate and the chemical copper; When this problem is blackened in the thin inner layer, there will also be poor blackening and Browning, uneven color, and poor local blackening and Browning. 2. Poor surface treatment caused by oil or other liquids contaminated w
Comparison of gold-plated and gold-plated circuit boards 1. The whole plate is gold-plated Generally refers to [electroplated] [electroplated nickel gold plate], [electrolytic gold], [electric gold], [electric nickel gold plate], there is a distinction between soft gold and hard gold (generally used as gold finger). The principle is to dissolve nickel and gold (commonly known as gold salt) in the chemical solution, the circuit board is immersed in the electroplating cylinder and the current is passed on the copper foil surface of the circuit board to generate nickel gold coating, electric nickel gold because of its coating hardness is high, wear resistance, not easy to oxidize the characteristics of electronic products have been widely used. Two, sinking gold 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 precipitation gold. Three, gold-
The reasons for the hole deviation are as follows: 1, there are pits on the cover plate, do not use aluminum plate with creases. 2, there are foreign bodies on the board, please pay attention to clean the board. 3, vacuum is not enough, please pay attention to vacuum negative pressure. 4. Drill The offset hole is irregular, so it is not a problem of positioning, film and material expansion and contraction, and it is a small offset hole, and the large hole in the middle is not offset. So there are basically a few things to check: 1. Whether the press foot of the rig is smooth. 2. The quality of the upper and lower backing plate, especially whether the upper backing plate is uneven. 3, whether the drill parameters are correct, 4. You are using a welding type of inferior drill. Generally, the above situation is basically the quality and parameters of the drill bit. Cheap drill bits of the Taiwanese type have more such problems. Germany, the United States, China, this kind of pr
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;
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