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Reflow process and its development


The pilot, causing test errors. (4) used in lithium batteries with rechargeable nickel-cadmium battery two. In the circumstances a reasonable test time charge, in order to ensure the accuracy of test data. 3 reflow uneven heating effect a major factor in the T reflow process to cause uneven heating of the components of the main reasons are: components, reflow heat or absorb heat capacity differences affect the belt or the edge of the heater, reflow the three aspects of the product load. (1) usually PLCC, QFP chip components with a discrete heat capacity compared to larger, welding large components than the smaller components is more difficult. (2) in the reflow oven conveyor belt in the transmission cycle of the product reflow, but also as a cooling system. In addition, in some of the edge and center of heated cooling conditions are different, the edge is generally low temperature, the furnace in addition to the zone temperature requirements are different, the same set surface temperature differences. (3) the impact of different product loading. Reflow temperature profile of the adjustment should be considered in no-load, load and load factor Sui different case to get a good repeatability. Load factor is defined as: LF = L / (L + s); which, L is the length of the substrate assembly, S is the substrate asked every assembly. Reflow process to obtain reproducible results, the greater the load factor the more difficult. Reflow furnace is usually the largest load factor in the range of 0.5 to 0.9. This situation, according to the product (component welding density, different substrates) and reflow furnace to determine the different models. To get good results and repeatability of the welding,herve leger skirts, practical experience is very important. 4 associated with the reflow soldering of the defect analysis of 4.1 bridged solder solder heating process will produce the collapse of edge, this happens in warm-up and the main heating two occasions, when the preheating temperature in the tens to a Baidu within the solder as a component of the solvent that will reduce the viscosity and flow, if its out of trend is very strong,Beats By Dre Headphones, will also be out of welding solder particles outside the gold particles, if they can not return in the melting to the welding area, will remain the solder ball formation. In addition to the above factors D component side electrode is formed good, circuit board layout design and welding specifications for the Secretary is away, the choice of solder resist coating method and its precision coating will result in bridging the reason. 4.2 gravestone (Manhattan effect) chip components subjected to rapid heating in case I happen to Alice Green legislation, because rapid heating to the temperature difference across components, power extreme side of the solder completely melting obtain good wetting, and The other side of the molten solder is not completely caused by poor wetting,tods shoes outlet, such legislation to promote the components of Alice. Therefore, the heating elements from the point of view when asked, so that the horizontal distribution of heat to form a balanced temperature to avoid the emergency heat generation. Alice legislation to prevent components of the main factors the following: (1) Select the strong adhesion of the solder, solder printing accuracy and precision component placement also need to improve. (2) components of the external electrodes need to have good wetting and wetting stability of SUI. Recommended: temperature below 40 ℃, humidity 70% RH or less, into the plant components using a period of not more than 6 months. (3) The width of the small size of the weld area in order to reduce solder melting end of the components produced by surface tension. In addition the printing may be appropriate to reduce the thickness of solder, such as the choice of 100 ~ tm thickness. (4) Welding temperature management conditions set up for Alice is also a factor components. The goal is usually to be evenly heated, especially in the two connector components before the formation of fillet weld, uniform heating can not fluctuate. 4.3 poor wetting wetting is poor welding process solder and the solder circuit board area (copper) or D external electrodes, each generated by the infiltration does not ask after the reaction layer, which leads to less weld weld failure . One of the reasons most of the surface of the weld area is contaminated or stained with solder or by bonding the surface layer of metal compounds generated caused. For example, the surface of silver sulfide, tin oxide and other surface will have poor wetting. Another residual solder aluminum, zinc,herve leger toronto, cadmium or more than 0.005%, due to the moisture flux to reduce the role of the activation, poor wetting can also occur, so the welding surface of the substrate surface and the components to make anti-pollution measures . Choose the right solder,Salvatore Ferragamo outlet, and set a reasonable soldering profile. T reflow soldering process is complex and critical process, involving automation, materials, fluid mechanics and metallurgy and other sciences. To obtain good welding quality, must examine all aspects of welding technology. This paper only a few aspects of the welding process were discussed and many ideas far in terms of existing equipment and process conditions, as this article only with peers. Author Xian Fei, (1975), male, bachelor, engineer, work in electronic assembly processes, a number of professional papers published.
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