1. Why should we use lead-free technology?
Lead is a toxic heavy metal. Excessive absorption of lead by the human body can cause poisoning. Intake of low amounts of lead may affect human intelligence, nervous system and reproductive system. The global electronic assembly industry consumes about 60,000 tons of solder every year, and it is still increasing year by year. The industrial slag containing lead salts formed by this seriously pollutes the environment. Therefore, reducing the use of lead has become the focus of attention around the world. Many large companies in Europe and Japan are vigorously accelerating the development of lead-free alternative alloys and have planned to gradually reduce the use of lead in electronic product assembly starting in 2002. Completely eliminate it by 2004. (The traditional solder composition is 63Sn/37Pb. In the current electronic assembly industry, lead is widely used).
2. Requirements for lead-free substitutes:
1). Price: Many manufacturers require that the price cannot be higher than 63Sn/37Pn, but at present, the finished products of lead-free substitutes are 35% higher than 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 specific application.
Wave soldering solder rod: To successfully achieve wave soldering, the liquid phase temperature should be lower than 265°C.
Manual soldering solder wire: The liquid phase temperature should be lower than the working temperature of the soldering iron 345°C.
Solder paste: The liquid phase temperature should be lower than 250°C.
3). Electrical conductivity.
4). Good thermal conductivity.
5). Small solid-liquid coexistence range: Most experts recommend that this temperature range be controlled within 10°C to form a good solder joint. If the alloy solidification range is too wide, solder joint cracking may occur, causing premature damage to electronic products.
6). Low toxicity: The alloy composition must be non-toxic.
7). Good wettability.
8). 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 protruding fillet welds on the through device.
9). Repeatability of production, consistency of solder joints: Since the electronic assembly process is a mass production process, its repeatability and consistency must be maintained at a high level. If some alloy components cannot be repeatedly manufactured under mass production conditions, or their melting points change significantly due to changes in components during mass production, they cannot be considered.
10). Appearance of solder joints: The appearance of solder joints should be close to that of tin/lead solder.
11). Supply capacity.
12). Compatibility with lead: Since there will not be a full transition to a lead-free system in the short term, lead may still be used on PCB pads and component terminals. If diamond is added to the solder, the melting point of the solder alloy may be very low and the strength will be greatly reduced.
3. Several commonly used lead-free substitutes:
1). Alloys used in solder paste: 96, 5Sn/3, 5Ag melting point is 221℃ 95, 5Sn/4, 0Ag/0, 5Cu melting point is 217℃
2). Alloy solders used in wave soldering and manual soldering: 99, 3Sa/0, 7Cu Melting point is 227℃
(In terms of materials, several new solder pastes have been put on the market, but they cannot replace the existing lead-tin solder. They all need to make corresponding process adjustments. The main difference between new solder pastes and traditional solder pastes is that the melting point is relatively high. The melting point of commonly used lead-free solder pastes is usually 217℃-225℃)
4. Environmentally friendly lead-free process
Since 2002, Chuxin has been exploring and researching lead-free process equipment. On the basis of learning from foreign advanced technology, after years of unremitting efforts, it has successfully developed PCB board assembly equipment suitable for lead-free process. Chuxin has always paid attention to the development of lead-free process, and continues to improve and improve itself with the changes in lead-free process technology, while doing its best to minimize the cost of use for customers.
Today, the development of technology, the improvement of quality, and the perfect service have pushed Chuxin to the next new level. We will continue to challenge in advanced fields and meet the growing needs of customers with high-quality products and services. In Chuxin, there is no compromise and stop, only what customers expect from Chuxin.