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Control points for the temperature zones of the reflow welding machine

Time:2019-06-22   |   Source:   |   Compile :9

The reflow welding machine is divided into four stages of temperature zone: warm-up zone, insulation area, reflux welding area and cooling zone. If the four temperature zone stage control of the return welding machine is not good, it is easy to cause a large number of bad products appear.Below Guangyande reflow welding here for a big explanation under the reflux welding machine these four major temperature zone stage control points.

the reflow welding machine


Key points of control for the warm-up section temperature zone of the reflow welding machine


The purpose of this area is to heat the PCB at room temperature as soon as possible to achieve the second specific target, but the heating rate should be controlled within the appropriate range, if too fast, there will be a thermal impact, circuit boards and components may be damaged; Due to the fast heating speed, the temperature difference in the sMA in the later part of the temperature zone is large. In order to prevent damage to the component struck by thermal shock, the maximum speed is set at 4 degrees C/s. However, the rise rate is usually set to 1-3 degrees C/s. The typical heating rate is 2 degrees C/s.


Key points of control for the temperature zone of the heat insulation section of the reflow welding machine


The insulation section is the area where the temperature is melted from 120 degrees C-150 degrees C. The main purpose is to stabilize the temperature of the components within the SMA and minimize the temperature difference. Give enough time in this area to keep the temperature of the larger components up to the smaller components and ensure that the flux in the solder paste is fully evaporated. By the end of the insulation section, the oxides on the pads, solder balls, and component pins are removed and the temperature of the entire circuit board is balanced. It should be noted that all components on the SMA should have the same temperature at the end of this period, otherwise entering the return section will produce various undesirable welding phenomena due to uneven temperatures in each part.


Key points of control for the temperature zone of the reflux welder's reflux section


In this area, the heater temperature is set high, allowing the temperature of the component to rise rapidly to the peak temperature. The welding peak temperature in the return section varies depending on the solder paste used, so it is recommended that the solute temperature of the solder paste be added to 20-40 degrees C. For 63Sn/37Pb solder paste with melting point of 183 degrees C and Sn62/Pb36/Ag2 solder paste with melting point of 179 degrees C, the peak temperature is 210-230 degrees C, and the reflow time should not be too long to prevent adverse effects on SMA. The ideal temperature curve is a small area covered by the "end zone" that exceeds the solder melting point.


Key points of control for the temperature zone of the cooling section of the reflow welding machine


The lead tin powder in this solder paste has melted and fully wetted the connected surface and should be cooled as fast as possible, which will help to obtain a bright solder joint with a good shape and a low contact angle. Slow cooling causes more decomposition of the circuit board into the tin, resulting in gray and brown solder joints. In the case of the end, it can cause bad tin and reduce the force of welding point binding. The cooling segment cools at a rate of 3-10 degrees C/s and cools 75 degrees C.