Electronic components of the wave welding technology- pcb assembly china-2
At present, the most commonly used welding wave solder-pcba china is eutectic tin lead alloy: tin 63%; Lead 37%, should always keep soldering pot of solder temperature, the temperature should be higher than 183 ℃ temperature of the liquid alloy, and make temperature even. In the past, 250 ℃ temperature is regarded as the soldering pot "standard". Along with the flux of technological innovation, the whole soldering pot of solder temperature uniformity of controlled, and set up the preheater, development trend is to use the lower temperature soldering pot. In 230-240 ℃ within the scope of the solder pot set temperature is very common. Usually, no uniform thermal quality components, to ensure that all of the solder joints to a high enough temperature to form qualified solder joints are necessary. T
he important question is to provide enough quantity of heat, improve all leads and the temperature of solder, so as to ensure that the liquidity of solder, wet on both sides of the solder joints. The low temperature solders will reduce the components of the substrate and thermal shock, helps to reduce the formation of scum, in low intensity, flux coated operation and flux compounds under the common function of, can make the wave export have enough of flux, which can reduce the burr and solder ball production. Soldering pot of solder composition and time have close relations, namely with time and change, this leads to the formation of the scum, this is from the welding components to removing the overspray and other metal impurity in the reason and welding technology in the cause of the loss of zion. These factors can reduce the solder liquidity. In purchasing, the provisions of the metal to trace scum and the highest content of solder tin limit, in all standard (such as IPC/J-STD-006 has a clear regulations). In the welding process, the requirements of the purity of solder in ANSI/J-STD-001-B standard also has a regulation. In addition to the scum on the limit of 63% tin; Lead alloys 37% specified in the lowest tin content shall not be lower than 61.5%. pcb assembly china
Wave components of the gold and welding on organic swimming layer copper concentration faster than the past together. pcba manufacturer This kind of gathered together, and obvious tin loss, can make the loss of solder liquidity, and produce welding problem. Rough outside, a granular solder joints is frequently because of solder caused by scum. Because the scum of the pot of agglomeration solder or components of the remains of the inherent dim, coarse granular solder joints can also be tin content low signs, not local special solder joints, tin tin pot is the loss of the results. This kind of appearance also may be on the solidification process, because vibration or caused by the impact. The appearance of the solder joints can directly reflect the process problems or materials. To maintain the solder "full pot" state and according to the process control scheme to check the soldering pot analysis is very important. Due to the pot and solder is scum "away" pot of solder flux, it is often is unnecessary, because in the application of conventional requirement in tin pot to add solders, make tin pot of solder is always full. In the loss of zion, add pure tin helps to keep the required concentration. In order to monitor tin pot of compounds, should be the routine analysis. If added tin, should the sampling and analysis, to ensure the correct solder composition proportion. Too much scum is a difficult problem. No doubt, soldering pot there is always the scum exist, in the atmosphere, especially that when the welding.