Why is the lead-free welding platform controversial?

According to the "2020 China welding table market research analysis and development prospects Research Report", the demand data of China's welding table industry is on the rise. In the future, lead-free constant temperature welding platform and robot welding will become the mainstream of the welding industry. The current market has the most controversy is lead-free constant temperature welding table, some people ridicule it is not only expensive, but also many domestic enterprises are similar to the object, can not be as expected. And in fact, not all of this is the case, the following lead-free welding platform manufacturers from several aspects to analyze why they are controversial.

First of all, we start from the origin of the lead-free welding table and why to implement the lead-free process.

(1) The characteristics of lead and the harm to the human body: lead (lead Pb), gray metal, melting point is 327.5 ° C, heating to 400-500 ° C, there is a large number of lead vapor escape, and in the air quickly oxidized into lead oxide and condensed into smoke and escape everywhere. The main industries in contact with lead in industry are lead mining, lead burning rope and refining, battery manufacturing, welding of electronic products and lead spraying of electronic components. In the above exposure, lead and its compounds invade the human body mainly through respiratory production and digestive tract, causing lead poisoning and posing harm to human health. The EPA study found that lead and its compounds are among 17 chemicals that seriously harm human life and the natural environment. Usually occupational lead poisoning is chronic poisoning, which will cause interference and harm to the human nervous system, digestive system and blood system, and its clinical symptoms are dizziness, headache, fatigue, memory loss, nausea, irritability, loss of appetite, abdominal pain, anemia, mental disorders.

(2) The trend of lead-free electronic products: With the improvement of human awareness of their own health and the enhancement of global environmental awareness, in order to reduce as much as possible the pollution of lead and other heavy metals on the environment and damage to human beings, European and American countries in July 1, 2006, the full implementation of lead-free electronic products, China also requires that electronic home products placed on the market from July 1, 2006 in the national key supervision catalog cannot contain lead ingredients. Therefore, the solder used in electronic welding (solder wire, solder paste, etc.) will gradually abandon the traditional tin lead alloy and use almost pure tin. Of course, tin does not contain any impurities does not exist, and there is no clear and unified definition of the international standard for lead-free, the International Standards Organization (ISO) proposal: The content of lead in electronic assembly solder should be less than 0.1WT%, but in lead-free solder, it is common to add some other metal substances such as copper and silver to the tin material according to different product requirements to enhance the electrical connection performance of the active solder joints of the tin wire.

Secondly, what is the difference between lead-free solder and traditional leaded solder?

Lead-free solder contains no lead and has a higher melting point than conventional (63% tin +37% lead) solder.

Commonly used lead-free solder:

Sn-Ag (Tin + Silver, 96-98% Tin)

Sn-Cu (Tin + Copper, 96% Tin)

Sn-Ag-Cu (Tin + Silver + copper, 93-96% Tin)

Sn-Ag-Bi (Tin + Silver + bismuth, 90.5-94% tin)

Sn-Ag-Bi-Cu (Tin + Silver + bismuth + Copper, 90-94% Tin)

The melting point of 63/37 lead solder is 183 ° C, and the freezing point is also 183 ° C. Note: This solder will not appear colloidal [cooling from liquid to solid (or vice versa) at the same temperature point].

60/40 lead solder has a melting point of 191 ° C and a freezing point of 183 ° C. Note: This solder has a range of 8 ° C to form a colloidal state [temperature range required for cooling from liquid to solid (or vice versa)].

Lead-free solder melting point range from 217℃ to 226℃.

However, the requirements for lead-free alternatives are more complex.

(1) Price: Many manufacturers require that the price cannot be higher than the traditional solder (63Sn/37Pb), but at present, the finished products of lead-free alternatives (solder wire, solder paste and tin bar) are 35% higher than the traditional solder (63Sn/37Pb).

(2) Melting point: most manufacturers require a minimum solid phase temperature of 150 ° C to meet the working requirements of electronic equipment. The liquid phase temperature depends on the application. Solder wire for manual welding: liquid phase temperature should be lower than the working temperature of the soldering iron 345℃. The current lead-free welding table set temperature is basically about 350℃. Moreover, the heating rate and return temperature are very high, and at present, there are QUIK, Jinsanyuanyuan, Gudhep GD90 lead-free constant temperature welding platform in China can meet this requirement.

(3) Good electrical and thermal conductivity.

(4) Small solid-liquid coexistence range: most experts recommend that this temperature range be controlled within 10 ° C in order to form a good solder joint, if the alloy solidification range is too wide, it is possible to crack the solder joint, causing premature damage to electronic products.

(5) Low toxicity: the alloy composition must be non-toxic.

(6) Good wettability.

(7) Good physical properties (strength, tensile, fatigue) : The alloy must be able to provide the strength and reliability that Sn63/Pb37 can achieve, and there will be no protruded fillet welds on the through hole device.

(8) Repeatability of production, consistency of solder joints: Because the electronic assembly process is a mass manufacturing process, its repeatability and consistency are required to maintain a high level, if some alloy components can not be repeated in mass conditions, or its melting point in mass production due to changes in composition and large changes, it can not be considered.

(9) Solder joint appearance: the solder joint appearance should be close to the appearance of tin/lead solder.

(10) Compatibility with lead: Because it will not immediately be fully transformed into a lead-free system in the short term, lead may still be used on the terminals of PCB pads and components, such as lead in the solder, may make the melting point of the solder alloy drop very low, greatly reduced strength.