Reflow profile for lead free solder5/8/2024 ![]() ![]() ④ The solderability and bright solder joints can be improved by using solder flux activation temperature matching the paste of lead-free alloy. ③ Due to slow heating, the temperature difference of PCB board surface decreases, which is conducive to overcoming the adverse factors of lead-free solder causing the reduction of process window. ② As the temperature rises linearly, it is easy to control and the process has good repeatability. ① On the premise of not increasing the total time, prolong the heating time, so as to avoid the damage of components caused by excessive heating rate. Of course, the use of this temperature curve has a prerequisite what is that it must use the reflux furnace with a good heat transfer performance, in order to make the soldering parts in the peak temperature, thus, its surface temperature difference can meet the requirements. However, the total process time is not extended, but can be appropriately shortened the total process time. Its main feature is the elimination of the heat preservation stage, soldering parts from room temperature slowly rose to the peak temperature, thus extending the heating time, so that the heating rate can be reduced to 0.8~2 ℃ /s. This curve is called a "tent" or "triangle" shape. ② As the liquid time of lead-free solder is prolonged, it is beneficial to overcome the wettability of lead-free solder. ① Maintain sufficient time at high temperature to achieve thermal balance of components with large thermal capacity differences and reduce the cavitation of BGA solder joints. This curve is called trapezoidal temperature curve, and its main feature is to extend the peak time of reflow area, so that the time of soldering parts above the liquid phase line is extended from the traditional 40s ~ 60s to 60s ~ 90s, and the time of 30s ~ 60s should be maintained at the peak temperature of reflow soldering. ![]() Therefore, many studies recommend the following two types of temperature curves for lead-free solders. However, the melting point of lead-free solder increases obviously, which challenges the optimal process parameter value tested by long-term production practice. And the temperature of reflow process is above 183 ℃, with peaks rising 30 ℃ ~40 ℃. The temperature of “Heat Preservation” is around 140 ℃ ~160 ℃. That is, “Heating” – “Heat Preservation” – “Reflow” – “Cooling”. Typical reflow temperature curves using Sn/Pb eutectic solders are usually divided into four sections. Suitable Temperature Curve of Lead-free Solder: The eutectic solder with a 93% diffusibility range, and the lead-free solder with a 73%~77% diffusibility range. Therefore, we must raise the manufacturing temperature in the manufacturing process, otherwise it will cause a series of adverse consequences.Ģ) Wettability is slightly worse. It has a melting point of about 217 degrees Celsius and a complete melting temperature of 235 degrees Celsius. Compared with the traditional solder, it has two disadvantages in terms of manufacturability as following:ġ) The melting point is high. Alloy,, is the best solder in the reflowing process.
0 Comments
Leave a Reply. |