There are many types of key switches, and different types of switches have different soldering methods. The commonly used soldering methods are wave soldering, reflow soldering, and manual soldering:
Wave soldering is used for the soldering of plug-in electronic components. The soldering equipment is a wave soldering machine. Commonly used are 3 temperature zones, 6 temperature zones, 8 temperature zones, 10 temperature zones and 12 temperature zones. The temperature of wave soldering should not exceed more than 240 degrees Celsius / 2 seconds or 235 degrees Celsius / 5 seconds, the advantages of soldering key switches in this way are low price, time-saving and labor-saving, but the possibility of bridging and short-circuiting between solder joints should be avoided.
Reflow soldering is mainly used for the soldering of SMD electronic components, so it is generally used in membrane key switches. The advantages of this method are that the temperature is easy to control, oxidation can be avoided during the soldering process, and the manufacturing cost is easier to control. The disadvantage is that Solder sagging will also occur during the soldering heating process. This situation occurs in both preheating and main heating. When the preheating temperature is in the range of tens to 100, the solvent, which is one of the components in the solder, will reduce the viscosity. outflow.
Manual soldering is also suitable for plug-in key switch soldering. The soldering equipment is an electric soldering iron. The temperature of the soldering iron for manual soldering should be controlled between 320-350 degrees Celsius, and the soldering time should not exceed 2 seconds. The advantage of manual soldering is that it can accurately grasp each The welding of a component is easy to weld, but the disadvantage is that it is too time-consuming and labor-intensive.
The above are the three commonly used welding methods for key switches. Different welding methods have their corresponding advantages and disadvantages. The selection of welding methods should be reasonably selected according to the situation of the key switch. The correct welding method can ensure that the quality of the key switch is not affected.
When the tact switch is mounted on the board, since the board powder that may be scattered during the operation and installation may enter the switch, be sure to add this point in the operation. And before the installation of the key switch, it must be ensured that the surrounding environment is clean and there is no excessive debris.
When the key switch is used for reflow soldering, be careful not to let the foaming flux contact the printed circuit board on the switch installation side. If there is foaming flux on the substrate, it will enter the switch and cause poor conduction of the touch switch, thereby reducing the conduction of the switch. performance.
Since the base of the tact switch is not completely sealed, be careful not to let some moisture, dust and sundries enter when installing the switch. For example, when installing in some places with too much dust, a layer of relevant protective film must be covered before the cover of the switch is installed to avoid the intrusion of dust and sundries.
The welding preheating temperature of the tact switch is generally recommended to be below 100 °C, and the temperature in the operation welding should be controlled at 260 °C, and the post-welding time should be completed within 3 seconds. If the welding time of the switch is too long If it is too long, it is easy to cause soldering through or damage to the end feet. Therefore, care should be taken in the aspects of soldering time and soldering temperature.
In the process of repeatedly welding the tact switch, it should be stopped for three minutes between the first operation and the second operation, and after the solder joints of the switch have been sufficiently dissipated, the second welding should be carried out after returning to normal temperature. Otherwise, continuous welding at high temperature will easily cause the welding feet of the tact switch to be deformed or damaged. Therefore, the temperature environment should be ensured during the welding process.