Circuit board welding 2020-07-20 16:23:00 Although the SMT patch automation equipment is now very advanced, replacing most of the manual work, but due to the particularity of some components and the components that cannot be recognized by the machine, it is still necessary Manual welding is used to complete the work, and the beautiful and accurate welding process is an important indicator to test the welding hands. Today, I will take a look at the steps and precautions of manual circuit board welding with you. The specific operating steps of soldering iron welding can be divided into five steps, called the five-step engineering method, which must be strictly operated to obtain good welding quality. Prepare for soldering: prepare solder wire and soldering iron. At this time, it is particularly emphasized that the head of the soldering iron should be kept clean, that is, it can be stained with solder (commonly known as eating tin). Heat the soldering parts: Touch the soldering iron to the soldering point. First, keep the soldering iron to heat all parts of the soldering parts, such as the leads and pads on the printed circuit board to heat them, and then pay attention to the flat part (larger part) of the soldering iron tip. For weldments with larger heat capacity, the side or edge of the soldering iron tip contacts the weldments with lower heat capacity to keep the weldments evenly heated. Melting solder: When the solder is heated to a temperature that can melt the solder, the solder wire is placed on the solder joint, and the solder begins to melt and wet the solder joint. Remove solder: When a certain amount of solder is melted, remove the solder wire. Remove the soldering iron: When the solder completely wets the solder joints, remove the soldering iron. Note that the direction of removing the soldering iron should be approximately 45°. Soldering according to the above steps is one of the keys to obtain good solder joints. In actual production, one of the most prone ways to violate the operation steps is that the soldering iron tip does not first contact the welded part, but first contacts the solder wire. The molten solder drips on the welded part that has not yet been preheated. In this way, it is easy to produce virtual solder joints, so the tip of the soldering iron must be in contact with the welded parts. Preheating the welded parts is an important means to prevent virtual welding. Note: 1. Before welding, observe whether each solder joint (copper skin) is smooth and oxidized. 2. When soldering items, be sure to spot the solder joints to avoid short circuits caused by poor wire soldering. When soldering integrated circuits, we should pay attention to some things. When soldering integrated circuits, if the pins of the integrated circuits are gold-plated, do not scrape them with a knife, just use a clean eraser to clean them. For CMOS integrated circuits, if the pins have been short-circuited first, do not remove the short-circuit wire before soldering. It is advisable to use low melting point flux, and the temperature should not be higher than 150 degrees Celsius. If the workbench is covered with rubber, plastic and other materials that are easy to accumulate static electricity, integrated circuits and printed boards should not be placed on the workbench. Since the integrated circuit is a heat-sensitive device, it is necessary to strictly control its welding temperature and welding time, which can easily damage the integrated circuit. And we should also pay attention to this matter when soldering printed circuit boards. Generally, internal heating 20-35W or temperature-regulating electric soldering iron should be used. The shape of the soldering iron tip should be conical according to the size of the printed circuit board pad, and the temperature of the soldering iron tip should not exceed 300 degrees Celsius during heating. When heating, we should try to avoid leaving the soldering iron tip in one place for a long time, so as not to cause local overheating and damage the copper foil or components. Do not use the soldering iron tip to rub the pad to increase the wettability of the solder during soldering, but use surface cleaning and pre-tinning methods. When soldering metallized holes, you should make the solder wet and fill the entire hole, not just soldering to the pad on the surface. The above is about the knowledge related to circuit board soldering. Have you learned a lot? There is still a lot of knowledge about PCB. The editor is waiting for you to open a sea of u200bu200bknowledge. ——Part of the content is taken from 'Electronics'