Circuit board welding method
Welding is one of the important links in the manufacture of electronic products. If there is no corresponding process quality assurance, it is difficult for any well-designed electronic product to meet the design requirements. It is impossible and unnecessary to use automatic equipment to make one or two circuit boards in the process of scientific research and development, design trial production, and technological innovation. Manual assembly and welding are often required. In mass production, from the screening and testing of components to the assembly and welding of circuit boards, they are all completed by automated machinery, such as automatic testing machines, component cleaning machines, tin enamelling machines, shaping machines, inserting machines, and wave soldering machines. , Leg shears, printed circuit board washing machines, etc. These computer-controlled production equipment have played an important role in the production of modern large-scale electronic products, which is conducive to ensuring the consistency of process conditions and assembly and welding operations, and improving product quality.
5.2.1 Soldering classification and soldering conditions
5.2.1.1 Classification of welding
Soldering technology is widely used in the electronics industry. In the manufacturing process of electronic products, almost all kinds of soldering methods are used, but the most common and representative method is soldering. Tin soldering is a kind of soldering. It heats the solder and the solder with a lower melting point than the solder to the soldering temperature. When the solder does not melt, the solder melts and infiltrates the soldering surface, relying on the diffusion of atoms between the two Form the connection of the weldment. Its main characteristics are as follows:
⑴ The melting point of the solder is lower than that of the weldment;
⑵ When soldering, heat the solder and the weldment together to the soldering temperature, the solder will melt but the weldment will not melt;
⑶ The formation of soldering relies on the molten solder to infiltrate the soldering surface, and the capillary action makes the solder enter the gap of the soldering piece to form an alloy layer, thereby realizing the bonding of the soldering piece.
Except for some alloy materials containing a large amount of chromium, aluminum and other elements, which are not suitable for soldering, most other metal materials can be soldered by soldering. The soldering method is simple, and only a simple tool (such as an electric soldering iron) can be used to complete the welding, solder joint repair, component replacement, and re-soldering process. In addition, soldering also has the advantages of low cost and easy automation. In electronic engineering technology, it is the earliest, most widely used and largest welding method.
5.2.1.2 Requirements for soldering
The physical basis of welding is “wetting”, which is also called “wetting”. To explain infiltration, let’s start with the water droplets on the lotus leaf: there is a layer of impermeable waxy substance on the surface of the lotus leaf. The surface tension of the water keeps it in a bead shape and rolls on the lotus leaf without spreading. It is called non-wetting; conversely, if the liquid is spread out on the contact surface with the solid, it is called wetting. The process of soldering is to make the lead-tin solder melt, flow, and infiltrate on the soldering surface by heating, so that the lead-tin atoms can penetrate into the surface of the copper base material (wire, pad) and on the contact surface between the two A brittle alloy layer of Cu6-Sn5 is formed.
During the soldering process, the angle formed by the contact between the solder and the base metal is called the infiltration angle, as shown in Figure 5.13. (a) In the figure, when the solder and the base metal are not infiltrated, a good solder joint cannot be formed; (b) In the figure, at that time, the solder and the base metal are infiltrated and a good solder joint can be formed. By carefully observing the infiltration angle of the solder joints, the quality of the solder joints can be judged.
Circuit board welding method
Welding is one of the important links in the manufacture of electronic products. If there is no corresponding process quality assurance, it is difficult for any well-designed electronic product to meet the design requirements. It is impossible and unnecessary to use automatic equipment to make one or two circuit boards in the process of scientific research and development, design trial production, and technological innovation. Manual assembly and welding are often required. In mass production, from the screening and testing of components to the assembly and welding of circuit boards, they are all completed by automated machinery, such as automatic testing machines, component cleaning machines, tin enamelling machines, shaping machines, inserting machines, and wave soldering machines. , Leg shears, printed circuit board washing machines, etc. These computer-controlled production equipment have played an important role in the production of modern large-scale electronic products, which is conducive to ensuring the consistency of process conditions and assembly and welding operations, and improving product quality.
5.2.1 Soldering classification and soldering conditions
5.2.1.1 Classification of welding
Soldering technology is widely used in the electronics industry. In the manufacturing process of electronic products, almost all kinds of soldering methods are used, but the most common and representative method is soldering. Tin soldering is a kind of soldering. It heats the solder and the solder with a lower melting point than the solder to the soldering temperature. When the solder does not melt, the solder melts and infiltrates the soldering surface, relying on the diffusion of atoms between the two Form the connection of the weldment. Its main characteristics are as follows:
⑴ The melting point of the solder is lower than that of the weldment;
⑵ When soldering, heat the solder and the weldment together to the soldering temperature, the solder will melt but the weldment will not melt;
⑶ The formation of soldering relies on the molten solder to infiltrate the soldering surface, and the capillary action makes the solder enter the gap of the soldering piece to form an alloy layer, thereby realizing the bonding of the soldering piece.
Except for some alloy materials containing a large amount of chromium, aluminum and other elements, which are not suitable for soldering, most other metal materials can be soldered by soldering. The soldering method is simple, and only a simple tool (such as an electric soldering iron) can be used to complete the welding, solder joint repair, component replacement, and re-soldering process. In addition, soldering also has the advantages of low cost and easy automation. In electronic engineering technology, it is the earliest, most widely used and largest welding method.
5.2.1.2 Requirements for soldering
The physical basis of welding is “wetting”, which is also called “wetting”. To explain infiltration, let’s start with the water droplets on the lotus leaf: there is a layer of impermeable waxy substance on the surface of the lotus leaf. The surface tension of the water keeps it in a bead shape and rolls on the lotus leaf without spreading. It is called non-wetting; conversely, if the liquid is spread out on the contact surface with the solid, it is called wetting. The process of soldering is to make the lead-tin solder melt, flow, and infiltrate on the soldering surface by heating, so that the lead-tin atoms can penetrate into the surface of the copper base material (wire, pad) and on the contact surface between the two A brittle alloy layer of Cu6-Sn5 is formed.
During the soldering process, the angle formed by the contact between the solder and the base metal is called the infiltration angle, as shown in Figure 5.13. (a) In the figure, when the solder and the base metal are not infiltrated, a good solder joint cannot be formed; (b) In the figure, at that time, the solder and the base metal are infiltrated and a good solder joint can be formed. By carefully observing the infiltration angle of the solder joints, the quality of the solder joints can be judged.