Dispensing process requirements and characteristics Dispensing process requirements and characteristics. Dispensing process is mainly used for lead components through-hole insertion (THT) and surface mount (SMT) coexistence of paste insertion mixed assembly process. In the entire production process (see figure), we can see that the printed circuit board (PCB) one side of the components from the beginning of the dispensing curing, to the end to wave soldering welding, which is a long interval, and carry out other processes more, the curing of components is particularly important. PCB point B side --- SMD B side --- reflow curing --- screen printing A side --- SMD A side --- reflow soldering --- automatic insertion --- manual flow insertion --- wave soldering B side Process control in the dispensing process. Production is prone to the following process defects: the size of the glue dot is not qualified, drawing, glue dipping pads, curing strength is not good easy to fall out of the film, etc.. Therefore, the control of the technical parameters of the dispensing process is the solution to the problem.   The size of the dispensing volume according to work experience. The size of the diameter of the glue dot should be half of the pad spacing, the diameter of the glue dot after the patch should be 1.5 times the diameter of the glue dot. This will ensure that there is sufficient glue to bond the components and avoid too much glue soaked pads. How much glue is dispensed by the dispensing time and the amount of glue to decide, the actual production situation should be based on (room temperature, the viscosity of the glue, etc.) to choose the dispensing parameters. Dispensing pressure Currently. The dispensing machine uses a pressure to the dispensing needle barrel to ensure enough glue to squeeze out the dispensing nozzle. Too much pressure can easily cause too much glue; too little pressure can cause intermittent dispensing and leakage, thus causing defects. The pressure should be selected according to the quality of the glue and the temperature of the working environment. If the ambient temperature is high, the glue viscosity will become smaller and the liquidity will become better, then the pressure should be lowered to ensure the glue supply, and vice versa. Dispensing nozzle size in the actual work. The size of the inner diameter of the dispensing nozzle should be the diameter of the glue dot 1/2, dispensing process, the size of the pads on the PCB should be selected according to the size of the dispensing nozzle: such as 0805 and 1206 pads are not very different in size, you can choose the same needle, but for the difference between the pads should choose a different dispensing nozzle, so that you can ensure the quality of the glue, but also improve production efficiency. The distance between the dispensing nozzle and the PCB board is different. The dispensing machine using different needles, the dispensing nozzle has a certain degree of stopping. Each work should be started to ensure that the stop lever of the dispensing nozzle touches the PCB. Glue temperature. General epoxy resin glue should be kept in the refrigerator at 0 - 50C, and should be taken out 1/2 hour in advance when using to make the glue fully compatible with the working temperature. The use temperature of glue should be 230C--250C; the ambient temperature has a great influence on the viscosity of glue, the temperature is too low then the glue point will become smaller and the phenomenon of drawing will appear. A difference of 50C in ambient temperature will cause 50% change in the amount of glue dispensed. Therefore, the ambient temperature should be controlled. At the same time, the temperature of the environment should also be given to ensure that the humidity is small, the glue point is easy to become dry, affecting the bonding force. Viscosity of glue. The viscosity of glue directly affects the quality of dispensing. If the viscosity is large, the glue point will become small and even draw; if the viscosity is small, the glue point will become large and then may bleed pad. In the process of dispensing, a reasonable pressure and dispensing speed should be selected for different viscosity of glue. Curing temperature curve For the curing of the glue. The manufacturer has generally given the temperature curve. In practice, a higher temperature should be used as far as possible. In practice, the glue should be cured at a higher temperature as possible, so that the glue has sufficient strength after curing. Air bubbles The glue must not have air bubbles. A small bubble will cause many pads without glue; each time the glue should be filled with air in the bottle to prevent the phenomenon of empty play. For the adjustment of the above parameters, should be according to the point and the way, any change in any one parameter will affect other aspects, while the defects may be caused by multiple aspects, should be possible factors to chec

       Jiwei.com reported that in the first wave of fuel car electrification transition, domestic battery companies along with the market explosion successfully among the global first echelon, growing up such as Ningde Time, BYD and other leading global enterprises. 　　At the same time of the rapid development of Chinese battery enterprises, the demand for power batteries and energy storage in overseas markets is also intensifying, and there is a huge market gap. At the same time, with the withdrawal of "national subsidies", the domestic new energy market is tilted from policy-driven to market-led, and competition is becoming increasingly fierce, so "going out" has become a natural choice for battery companies. 　　Recently, Ningde Times officially announced that it will cooperate with Ford to produce batteries in the United States. As a battery brother, Ningde Times to enter the North American market, or further drive the speed of domestic battery companies to the sea. 　　After entering Europe, Ningde Times finally set foot on North America. 　　After more than three years, at the end of December last year, Ningde Time's first overseas factory in Thuringia, Germany, was put into operation as scheduled for lithium-ion battery cells. With a total investment of 1.8 billion euros and a planned production capacity of 14 GWh, this is Ningde Times' first battery factory in Europe and its first factory outside China.         After the successful construction of the first battery factory, Ningde Times started to plan its second factory in Europe. last August, Ningde Times announced that it would build its second battery factory in Europe in Hungary with an investment of 7.34 billion euros and a planned capacity of 100 GWh. the factory is expected to start construction in the second half of this year and aims to become the largest power battery factory in Europe.        The reason why Ningde Times is willing to make a big investment in Europe to build a plant is inseparable from its on-hand fixed-point projects and target customers at that time. As early as from 2018 to 2019, Ningde Times had intensively obtained fixed-point projects or intended orders from overseas first-class car companies, for example, Daimler, Peugeot Citroen, BMW and so on. After this new plant of Ningde Times in Germany is put into operation, it will be able to supply batteries from local to BMW, Bosch, Daimler and other European automakers, eliminating long-distance shipping from China to Europe.        Outside of Europe, North America, where the electric vehicle market is starting to climb rapidly, is of course an important market for Ningde Times to focus on, as rumors of a North American plant have reversed several times before this. on February 14, Ningde Times finally made an official announcement, confirming that it will cooperate with Ford to produce batteries in the United States. 　　According to the agreement, Ningde Times will provide construction and operation services for Ford's battery plant in Michigan and license the battery patent technology. The plant, which is wholly owned by Ford, is expected to be put into operation in 2026 with an annual capacity of about 35 GWh, providing power cells for about 400,000 Ford electric vehicles per year. 　　It is reported that Ford and Ningde Time cooperation of this plant will be the first lithium iron phosphate battery plant in the United States. Compared to ternary lithium batteries, lithium iron phosphate batteries are lower cost and more secure. Ford said that the new plant's battery will be one of the lowest cost of production batteries, will help reduce the pricing of electric vehicles. 　　Industry analysts pointed out that the introduction of the U.S. "Inflation Reduction Act", so that the domestic manufacture of batteries in the United States more cost advantage. The bill provides that EV companies that manufacture and assemble batteries in the U.S. can offset more than one-third of the total cost of the batteries with subsidies they receive. 　　For car companies, the whole vehicle cost accounted for nearly half of the battery price, if it can be reduced, will undoubtedly help to improve the gross profit level of car companies, enhance the competitiveness of enterprises. 　　2022 U.S. new energy vehicle sales show that after Tesla, Ford jumped to second place in electric vehicle sales, with a 7.6% share of the all-electric vehicle market in the United States. With Ningde Time's advanced battery technology, Ford is expected to meet the challenges of competitors such as Tesla by reducing production costs. 　　And Ford's upside in the field of electric vehicles will naturally help Ningde Times to expand the North American market. The North American market, which has previously been dominated by Japanese and Korean battery companies, has finally been taken by Ningde Time. Seize the overseas market gap, domestic battery companies to accelerate the sea 　　Compared with the fully competi

Printing process requirements and characteristics In reflow soldering of surface mount assemblies, solder paste is used for the connection between the pins or terminals and pads of surface mount components with many variables. Such as the solder paste, the screen printing machine, the method of application of the solder paste and the printing process. In the process of printing the solder paste, the substrate is placed on the table, mechanically or vacuum clamped into position, aligned with positioning pins or vision, and the solder paste is printed with a stencil (stencil). In the stencil solder paste printing process, the press is the key to achieving the desired print quality. During the printing process, the solder paste is dispensed automatically, and the printing squeegee is pressed downward on the stencil so that the bottom surface of the stencil touches the top surface of the board. As the squeegee travels the entire length of the eroded graphic area, the solder paste is printed onto the pads through the openings in the stencil/screen. After the solder paste has been deposited, the screen comes off (snapoff) immediately after the squeegee and returns to its original position. This spacing or snapoff distance is set by the equipment design and is approximately 0.020" to 0.040". The disengagement distance and squeegee pressure are two important equipment-related variables for achieving good print quality. If not disengaged, this process is called on-contact printing. Contact printing is used when all-metal stencils and squeegees are used. Off-contact printing is used for flexible wire screens. There are three key elements in solder paste screen printing, which we call 3S: Solder paste, Stencils, and Squeegees. The correct combination of these three elements is the key to consistent screen printing quality. Scraper (squeegee) Squeegee role  In the printing, so that the squeegee will be rolled in front of the paste, so that it flows into the stencil hole, and then scrape off the excess paste, leaving the PCB pad with the same thickness of the stencil solder paste. There are two common types of squeegee: rubber or polyurethane (polyurethane) squeegee and metal squeegee. Metal squeegee made of stainless steel or brass, with a flat blade shape, the use of the printing angle of 30 to 55 °. When using higher pressure, it does not dig out the solder paste from the open hole, but also because it is metal, they are not as easy to wear as rubber squeegees, so they do not need to be sharp. They are much more expensive than rubber squeegees and can cause stencil wear. Rubber squeegees, using 70-90 rubber durometer hardness (durometer) squeegees. When too much pressure is used, the solder paste that seeps into the bottom of the stencil may cause bridging, requiring frequent bottom wiping. It may even damage the squeegee and stencil or screen. Too high a pressure also tends to dig the solder paste out of wide openings, causing insufficient solder rounding. Low squeegee pressure causes omissions and rough edges. Squeegee wear, pressure and hardness determine print quality and should be carefully monitored. For acceptable print quality, squeegee edges should be sharp, straight and straight.   Stencil (stencil) types The main stencils used today are stainless steel stencils, which are made by three main processes: chemical etching, laser cutting and electroforming. Since metal stencils and metal squeegees produce a fuller paste, sometimes the thickness of the print is too thick, which can be corrected by reducing the thickness of the stencil. In addition, the area of solder paste on the pad can be reduced by reducing ("fine tuning") the length and width of the fillet by 10 %. This improves the sealing of the frame between the stencil and the pad caused by the misalignment of the pad, and reduces the "blow-out" of the solder paste between the stencil bottom and the PCB. The cleaning of the bottom surface of the printed stencil can be reduced from once every 5 or 10 prints to once every 50 prints. Solder paste (solder paste) Solder paste is a combination of tin powder and rosin. The function of rosin is to remove oxide from component pins, pads and beads during the first stage of reflowing, which lasts about three minutes at 150°C. Solder, an alloy of lead, tin and silver, is reflowed in the **stage of the reflowing oven, at approximately 220? Viscosity is an important characteristic of the solder paste, and we require that the lower its viscosity during the printing stroke, the better its flow, and the easier it is to flow into the stencil holes and print onto the pads of the PCB. After printing, the solder paste stays on the PCB pads, its high viscosity, it maintains its filled shape and does not collapse downward. The standard viscosity of solder paste is about 500kcps ~ 1200kcps range, more typical 800kcps for stencil screen printing is ideal. A practical and economical way to determine if a solde

Curing, reflow process analysis In the curing and reflow process, the main thing is to control the temperature profile of curing and reflow, that is, the curing and reflow conditions, the correct temperature profile will ensure high quality solder joints. In the reflow oven, its interior is a black box for us, we do not know what is happening inside, so it brings me a lot of difficulties to develop the process. To overcome this difficulty, it is common in the SMT industry to use a temperature tester to derive a temperature profile, which is then referred to in order to change the process. The temperature profile is the temperature applied to the circuit assembly as a function of time. When plotted in the Cartesian plane, the reflow process forms a curve representing the temperature at a specific point on the PCB at any given time. Several parameters affect the shape of the curve, of which the *critical ones are the conveyor belt speed and the temperature setting for each zone. The conveyor speed determines the duration that the board is exposed to the temperature set for each zone, and increasing the duration allows more time for the circuit assembly to approach the temperature setting for that zone. The sum of the durations spent in each zone determines the total processing time. The temperature setting for each zone affects the rate of temperature rise of the PCB, with high temperatures creating a large temperature differential between the PCB and the zone temperature. Increasing the set temperature of a zone allows the board to reach a given temperature faster. Therefore, a graph must be made to determine the temperature profile of the PCB. Next is the outline of this step to generate and optimize the graph. The following equipment and auxiliary tools are required: temperature profiler, thermocouple, tool to attach the thermocouple to the PCB and solder paste parameter table. There are generally two types of temperature measurement instruments: a real-time thermometer that instantly transmits temperature/time data and makes a graph, and another thermometer that samples and stores the data and then uploads it to a computer. The thermocouple will use high-temperature solder such as silver / tin alloy, solder joints as tiny as possible attached to the PCB, or a small amount of thermal compound (also called thermal paste or thermal grease) spots covered with thermocouples, and then sticky attached to the PCB with high-temperature tape (such as Kapton). The location of the attachment should also be chosen, usually good to attach the thermocouple tip between the PCB pads and the corresponding component pins or metal ends. As shown in the figure (Attach the thermocouple tip between the PCB pads and the corresponding component pins or metal ends) A table of paste characteristics is also necessary, which should contain the desired duration of the temperature profile, the paste activity temperature, the alloy melting point and the desired maximum reflow temperature. The ideal temperature profile The theoretically ideal profile consists of four sections or zones, with the first three zones heating and the last zone cooling. The more temperature zones the furnace has, the more accurate and closer to the setting the profile of the temperature curve can be achieved. (Theoretically the ideal reflow profile consists of four zones, with the first three zones heating and the last zone cooling) Pre-heating zone, used to raise the temperature of the PCB from the ambient temperature to the required active temperature. Its temperature rises continuously at a rate of no more than 2 to 5°C per second, the temperature rises too quickly can cause certain defects, such as fine cracks in ceramic capacitors, while the temperature rises too slowly, the solder paste will be over-sensitive to temperature, there is not enough time for the PCB to reach the active temperature. The preheating zone of the furnace generally accounts for the entire heating 25~33% of the length of the heating channel. Active zone, sometimes called dry or wetting zone, this zone generally accounts for 33 to 50% of the heating channel, has two functions, the first is, the PCB will be at a fairly stable temperature sensing temperature, so that different quality components have the same temperature, reducing their considerable temperature difference. The second function is to allow the flux to be active and volatile substances to evaporate from the solder paste. The general prevailing active temperature range is 120 to 150°C. If the temperature in the active zone is set too high, the flux does not have enough time to become active. Therefore the ideal curve requires a fairly smooth temperature so that the temperature of the PCB is equal at the beginning and end of the active zone. Reflow zone, whose role is to raise the temperature of the PCB assembly from the active temperature to the recommended peak temperature. Typical peak temperature range

SMT's basic requirements for bonding glue l No impurities and air bubbles in the package l Long storage period l Can be used in high speed / or super high speed dispensing machines l Consistent glue dot shape and volume High dot cross-section, no pulling Easy to identify the color, easy to check the quality of glue dots by manual and automatic machines l High initial adhesive force High speed curing, low curing temperature of glue, short curing time l No collapse of glue dots during heat curing High strength and elasticity to resist sudden temperature changes during wave soldering Excellent electrical properties after curing l Non-toxic Good rework characteristics Production quality problems caused by SMD adhesive l Missing parts (with and without SMD glue traces) l Component skew l contact problems (pulling, too much SMD adhesive) SMD adhesive use specifications. l storage Glue ** should be registered after the arrival time, expiration date, model, and for each bottle of glue number. Then keep the glue in a constant temperature and humidity refrigerator at (1-10)℃. l Access When glue is used, it should be done on the principle of first-in, first-out. It should be taken out from the refrigerator at least one hour in advance, write down the time, number, user, and product applied, and put it in the room temperature under the seal. When the glue reaches the room temperature, the glue should be injected into the dispensing bottles respectively with the glue injection gun according to the usage amount of **. When injecting glue, fill the dispensing bottle carefully and slowly to prevent air bubbles. l Use Put the glue bottle back into the refrigerator, and take it out from the refrigerator 0.5~2.0 hours before production, mark the time, date and bottle number, fill in the record sheet of glue (solder paste) thawing and using time, clean the used glue bottle with alcohol or acetone and put it away for the next use, and put the unused glue into the refrigerator for storage with the marked time.