Classification and application of solder wire

Soldering technology has been successfully used for decades in various industries of electronics, and more and more precise high-density technologies have been innovated. Solder material is formed by the fusion of tin and lead in a certain proportion, which is an indispensable medium for connecting components and circuit boards, and is widely used in the production and maintenance of the electronics industry. Let's take a look at the role and application of solder wire.

The solder wire used in the welding of electronic components is composed of two parts: tin alloy and additives, the solder wire is matched with the electric soldering iron to complete the welding operation, in which the electric soldering iron provides stable and continuous melting heat, the solder wire is added to the surface and gap of the electronic components as a filler metal, and the electronic components are fixed, which is the main component of soldering, and the composition of the solder wire is closely related to its quality, which will affect the chemical, mechanical and physical properties of the solder wire.

1. Classification of solder wire specifications According to different situations, there are the following classification methods for solder wire: According to the classification of metal alloy materials: it can be divided into tin-lead alloy solder wire, pure tin solder wire, tin-copper alloy solder wire, tin-silver-copper alloy solder wire, tin-bismuth alloy solder wire, tin-nickel alloy solder wire and special tin-containing alloy solder wire; According to the chemical composition of the solder wire additives, it can be divided into rosin core solder wire, no-clean solder wire, solid core solder wire, weight grease type solder wire, single core solder wire, three-core solder wire, water-soluble solder wire, aluminum solder wire, stainless steel solder wire; According to the melting temperature: it can be divided into low temperature solder wire, normal temperature solder wire, and high temperature solder wire.

Melting point of solder wire / Commonly used solder wire is divided into two categories: leaded solder wire andlead-free solder wire, and its specifications and melting points are different. Among them, the commonly used lead solder wire Sn63Pb37 has a melting point of 183 degrees, the melting point of tin-copper lead-free solder wire Sn99.3Cu0.7 is 227 °C, and the melting point of tin-silver-copper lead-free solder wire Sn96.5Ag3.0Cu0.5 is 217 °C.

Composition of solder wire / lead-free solder wire: In order to adapt to the ROHS standard proposed by the EU environmental protection requirements, the solder is made of tin-copper, tin-silver-copper and other alloys, which does not contain lead, which is more environmentally friendly and safe. Leaded solder wire: an alloy composed of tin (melting point 232 degrees) and lead (melting point 327 degrees). Among them, the solder composed of 63% tin and 37% lead is called eutectic solder, and the melting point is 183 degrees.

The use of solder wire

<!--[if !supportLists]-->1.<!--[endif]-->To select the right high-quality solder, you should choose a low melting point solder wire for soldering electronic components.

<!--[if !supportLists]-->2.<!--[endif]-->The right amount of flux, dissolving 25% rosin in 75% alcohol (weight ratio) as flux, the right amount of flux is essential, but not more is better.

<!--[if !supportLists]-->3.<!--[endif]-->The soldering iron should be placed on the soldering iron holder. The specific method is as follows: heat the electric soldering iron, and when the solder can just be melted, apply flux, and then evenly coat the soldering iron tip with solder, so that the soldering iron tip is evenly attached to a layer of tin.

<!--[if !supportLists]-->4.<!--[endif]-->Soldering method: Use fine sandpaper to polish the pads and the pins of the component and apply flux. Dip the soldering iron tip into an appropriate amount of solder, touch the solder joint, and after all the solder on the solder joint is melted and submerged in the component lead, gently lift the soldering iron tip along the pin of the component to leave the solder joint.

<!--[if !supportLists]-->5.<!--[endif]-->The soldering time should not be too long, otherwise it is easy to burn the components, and if necessary, you can use tweezers to clamp the pins to help dissipate heat.

<!--[if !supportLists]-->6.<!--[endif]-->The solder joints should be in the shape of a sine crest, and the surface should be bright and smooth, without burrs.

<!--[if !supportLists]-->7.<!--[endif]-->The amount of solder should be appropriate, as excess solder not only consumes more expensive tin unnecessarily, but also increases soldering time and reduces the speed of work accordingly. What's more, in high-density circuits, excess tin can easily cause imperceptible short circuits.

<!--[if !supportLists]-->8.<!--[endif]-->After the soldering is completed, the residual flux on the circuit board should be cleaned with alcohol to prevent the carbonized flux from affecting the normal operation of the circuit.

<!--[if !supportLists]-->9.<!--[endif]-->The integrated circuit should be soldered last, and the soldering iron should be reliably grounded, or the waste heat should be used for soldering after the power is off. Or use a special socket for integrated circuits, and then insert the integrated circuit after soldering the socket.

2. How to choose solder wire Look at the appearance: through visual inspection, high-quality tin wire should be smooth and shiny, without oxidation and blackening! The quality of solder wire is generally bright in color, and the lead content in dark solder wire is higher, and it is relatively not easy to melt. The color of high-quality solder wire is shiny (leaded) or silvery-white (lead-free), not white. Touch with your hands: high-quality solder wire is white and shiny, and it is not easy to get on your hands when you wipe it with your hands, while the tin wire with high lead content is black in color, and it is easy to wipe it with your hands! Tin has good ductility, and the higher the purity of the tin wire, the less likely it is to break. Of course, tin wire with high tin content is inherently soft and does not belong to the hard metal category. Wettability: Judging by the wettability ability. The lead-free solder wire should be judged according to whether it meets the ROHS standard, flux residue, halogen-free, and tin speed. Smoke, spatter, residue, and brightness are also criteria for judging the quality of solder wire. Packaging: Pay attention to the packaging appearance of the solder wire, although the packaging appearance can not represent the quality, but the solder wire produced by the regular manufacturer will have the corresponding detailed identification, if there is a quality problem, it can be better verified. In the product label, the basic information of the solder wire should be indicated, such as the tin content or power of the solder wire, the lead content, the flux dose, the melting point, and the packaging weight. Brand: Choosing a solder producer is the best way to guarantee quality. Therefore, when we buy, we try to buy directly from big brand manufacturers.

Shelf life of solder wire Due to the addition of flux in the middle, if you don't worry about the soldering effect, you can leave it for a long time, but its surface will be oxidized, and once oxidized, it will affect the soldering effect. The shelf life of solder paste is generally 6 months, and it needs to be used within 6 months.

3. Application examples of solder wire in different electronic products

In the manufacture of smartphones, the requirements for solder wires are extremely high due to the high degree of integration of their internal circuits. Lead-free solder wire is usually used, such as tin-silver-copper lead-free solder wire Sn96.5Ag3.0Cu0.5. With a melting point of 217 degrees, this solder wire can be soldered at a relatively low temperature to avoid thermal damage to other delicate electronic components. Moreover, its good chemical properties and mechanical properties can ensure the stability of the solder joint during the frequent use of the mobile phone. For example, when soldering tiny chips on a mobile phone motherboard, a precise soldering process and a suitable solder wire are the keys to ensure a stable connection between the chip and the circuit board.

In the production process of computer motherboards, lead solder wire has also been widely used. Leaded solder wire with a melting point of 183 degrees, such as Sn63Pb37, is used in the production of some computer motherboards that are not particularly strict in environmental protection because of its relatively low cost and good soldering performance. However, with the increasing awareness of environmental protection, there is now a gradual transition to lead-free solder wire. There are many electronic components on the computer motherboard, including capacitors, resistors, chips, etc., and the solder wire should not only ensure the stability of the electrical connection when connecting these components, but also be able to withstand the heat generated by the computer during operation and possible physical vibration.

Fourth, the future development trend of solder wire technology

With the continuous development of electronic technology, electronic products are developing in the direction of smaller, lighter and more powerful performance, which also poses new challenges to solder wire technology. On the one hand, the composition of the solder wire may be further optimized to meet higher soldering accuracy and reliability requirements. For example, a new alloy solder wire with a lower melting point and better mechanical properties may be developed. On the other hand, in terms of welding process, automated welding technology will continue to develop. Traditional manual welding may gradually be replaced by automated equipment that can more precisely control parameters such as welding temperature, welding time, and solder amount, thereby improving the quality of welding. In addition, the environmental requirements for solder wire will continue to increase, and in the future, solder wire may pay more attention to environmental friendliness while ensuring performance, such as reducing smoke and harmful substances generated during the soldering process.

Summary: The article first introduces the important position of solder wire in the electronics industry, which is an important medium for connecting components and circuit boards. Then, the composition of solder wire is elaborated, including solder alloy and auxiliary, and it is pointed out that its composition is closely related to quality. Then, the solder wire was comprehensively analyzed from the aspects of specification classification (according to metal alloy material, chemical composition of additives, melting temperature), melting point, composition (leaded and lead-free), use (including selection, flux use, electric soldering iron operation, soldering method, post-soldering treatment, etc.), how to choose (look at appearance, touch by hand, wettability, packaging, brand) and shelf life. Then, the application examples of solder wire in the manufacture of smartphones and computer motherboards are given, and finally the future trend of solder wire technology towards composition optimization, automatic soldering technology and more environmental protection is discussed. Through the elaboration of these contents, readers have a more comprehensive understanding of solder wire, from its basic properties to practical applications, and then to the future development direction have a clear understanding.