Reasons and solution for the wave solder excessive tin slag
There are many reasons for the wave solder excessive tin slag. The main reason for the generation of tin slag by wave soldering is that too much impurity in the solder paste and improper operation result in the formation of tin slag (tofu slag).Below the FASTPCBA electronic wave soldering technicians to tell you specifically what are the reasons for these two phenomenon.
First, the wave solder impurity amount exceeds the standard, causing excessive tin slag.
1.The copper amount and microelement of the tin furnace tin exceed the standard. The copper amount and iron amount exceeding the standard are the main reasons for the formation of slag. The circuit are made of copper. Most of the electronic pin are made of iron.More or less elements of copper and iron fall into the tin furnace during operation process and lead to excessive copper and iron over time. When copper is over 0.8% and iron is over 0.05%, a large amount of tin slag is generated, which affects the tin defect on the circuit board. Therefore, the periodic copper amount of the furnace and the detection of other microelement should also be managed according to the equipment maintenance stage.
2. The operating temperature of the furnace is too high. Too high temperature is also a cause of excessive slag. Excessive temperature will make copper and iron elements more likely to exceed the standard. Therefore, accurate control of the furnace temperature during our production process is an important part of the entire welding process.
3.the usual cleaning furnace is also very critical, no clear furnace for a long time, the impurities in the furnace is high, which is also the cause of excessive tin slag. Therefore, in the management of this production, daily machine and equipment maintenance must be carried out according to the production requirements and standards, and the equipment should be cared and maintained regularly. The standard operation of equipment should be strictly followedby
Second, solutions to the wave solder excessive slag.
1. Regularly test the tin in the furnace. When the copper content isover8% and the iron is over 0.05%, the tin in the furnace should be replaced. Usually, the tin is used for about a month. It is still necessary to maintain regular continuity on the testing of the furnace and the maintenance of the equipment.
2. Control the operating temperature of the furnace (about 260-275 degrees Celsius), check whether the temperature gauge of the furnace is accurate, and repair it immediately. The flux should usegood quality. If the flux is not good, it will not be work around 260-275 degrees Celsius. Therefore, the temperature inside the furnace must strictly comply with the production management specifications in accordance with the instructions of the operating temperature.
3. Spot check of welding materials, test and analysis of liquid tin samples in tin furnace, test the composition and impurities have obvious changes, the current welding material factory is mixed, many manufacturers in order to save costs, using secondary recovery of tin slag, poor welding quality effect is also an important cause of excessivetin slag.
Third, the cause of wave soldering to produce tin oxide (tofu slag)
1. At present, some of the wave furnaces on the market are not ideally designed. The wave is too high, the table is too wide, the double wave furnace is too close, and the selection of rotary pump to form. When the wave is too high, the temperature drop is relatively large when the solder falls. The solder is mixed with air and rushed into the tin furnace to cause oxidation and semi-dissolution phenomenon, resulting in the generation of tin slag. The rotary pump did not take precautions, and the tin slag was continuously pressed into the furnace, and the chain reaction of the loop aggravate the slag generation. Therefore, in the production process, we must not only control the furnace temperature, but also pay attention to some details in the production, the rotary pump to take precautionary measures, to prevent or reduce the tin slag from falling into the furnace from the production process.
2. The temperature of the wave soldering is controlled to be relatively low, generally 280 ° C ± 5 ° C (for the tin strip of lead SN-CU0.7), and this temperature is the basic temperature required in the solder process . The low temperature of tin can not achieve a good dissolution, indirectly causing too much tin slag.
3. The contact area of molten tin with air is larger, the more tin slag,, if the molten tin that flows out directly falls into the tin furnace, and it is easy to bring in air into the molten tin,the two combining cause tin oxide.
4. Cleaningthe tin slagregularly so that the dropped solder can enter the furnace as soon as possible, instead of remaining on the tin slag, the uneven heat will cause too much tin slag.
1. Check the tin slag to check whether there is a certain amount of tin slag before the tin furnace is opened. It is necessary to clean the tin slag left before the last work, especially the wave motor area and the wave channel. This is related to the normative nature of our production management. The general production line order line is relatively compact, and may neglect some details. The last orderboards are finished, and the next order boards are Therefore, “details determine success or failure should not be an empty talk.”
2.Tin furnace tin amountinspection, the amount of tin in the furnace should be guaranteed to be close to the 0.5-1cm range of the furnace surface when stopping the wave. If the amount of tin is small, the contact area with air is large, the probability of oxidation is also large, the wave falls drop will be large, the impact of liquid tin will also increase, the torrent will roll, and more tin slag will form!So It is recommended to add tin bars to the tin furnace immediately in the update of the device.
3. Tin furnace temperature check, when the working temperature is low, hot tin will easily form temporary non-melt accumulation when flowing back from the nozzle. It is recommended that the customer adjust the working temperature of the tin furnace to a higher extent within the tolerance range of the product.
4. It is recommended that the operator regularly smash slag, and the slag must be smashed before getting off work every day. Do not move board when smashing slag, the board temperature should be increased by 10 °C (actual temperature) and thensmash slag,a small amount of reducing powder is used to accelerate separation of tin from slag and significantly reduce the amount of slag.
If the wave soldering value is normal, there are many reasons for the tin slag suddenly: 1) The tin furnace heating tube burns out, resulting in insufficient heating and uneven heating, resulting in more tin slag. 2) Checking the tin bar and tin furnace tin composition whether the impurities exceed the standard, there are many reasons for the occurrence of tin slag. 3) Check the differences between the various control items and the previous ones. Most of the time, your tin furnace has been partially oxidized. The tin furnace part is thoroughly tested under a large maintenance.
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