The so-called "lead-free manufacturing" is actually "lead-free" production technology, then what is "lead-free" production technology?
The chip on the current card device is connected to the PCB board through the small solder joints under the chip package. These small solder joints are traditionally lead-free, while the "lead-free" technology uses a tin, silver, and copper composite instead of lead. However, the shift from leaded products to lead-free products is a complex process that affects all electronic device suppliers and brings many challenges in the supply chain, lead-free process, and availability. It requires lead-based Materials replace lead-rich solders used in the past and lead materials used in the assembly process.
It should be noted that the lead-free technology does not bring about a revolutionary change. This should be clear to the user. To a certain extent, it still belongs to a "development" technology. In other words, the lead-free technology is based on the existing lead-containing SMT technology. Since the beginning of the SMT technology era, the rapidly expanding consumer market has caused the industry to recognize the harm caused by "revolutionary" changes. Therefore, when it comes to researching and developing new technologies, it has done everything possible to retain a considerable degree of old methods.
Having more “developmental†is certainly a good thing. It means that we can make better use of past experience. However, for lead-free technology, this is not simple. In the course of the development of SMT, we have experienced several "development" experiences that have a greater impact, such as grid-array arrangement (BGA), Flip-Chip, and so on. Some users may still remember the challenges brought about by these technologies. However, the arrival of lead-free technology, compared with the previous few technologies, the difficulty and the challenge is absolutely beyond it.
In the lead-free process, the choice of soldering materials is the most challenging. Because for the lead-free soldering process, the selection of materials such as lead-free solder, solder paste, and flux is the most critical and the most difficult. At present, the industry mainly considers several major criteria for the use of materials, including: metal characteristics, melting point, solderability, patents, cost, porosity, and toxicity. Metal properties mainly consider thermal fatigue life, bond strength and compatibility of lead-containing components, and other metal properties. Solderability includes solderability (or wettability) when soldered to component parts and solder extensions on PCB pads. Sex.
Although there is no alloy solder that is as good as lead-containing solder, there are many alternatives that can be used for this application. Currently, there are mainly three types of alloy materials that replace tin-lead as lead-free solder—tin/silver/copper, tin/copper, and tin/silver/copper/niobium. U.S. and European manufacturers are bullish on tin/silver/copper, while Japanese manufacturers tend to use tin/silver/copper/bismuth alloys. Currently there is no unified lead-free process standard in the world.
Some organizations are actively formulating standards for the application of lead-free technologies. For example, the Japan Welding Association (JIS) is stepping up its exploration of standards and evaluation methods for lead-free solders, hoping to quickly develop JIS standards. This requirement has driven the industry's choice of new solder systems. The new solder system not only requires similar physical, mechanical, temperature, and electrical properties as Sn/Pb eutectic solder (SnPb63), but it also has to be.
In addition to alloys in the solder is a consideration and choice focus, flux Flux should not be ignored. Different alloys have different density weights, different melting surface tensions, different melting point temperatures, and different oxidation characteristics. This also tells us that the formulation of flux Flux will be different from the case of lead (Note: flux Flux is a collective name, Flux contains many different functional components, such as carriers, solvents, diluents, stabilizers, fluxes, etc. Etc. This combination of multiple ingredients, a variety of alternative materials, results in a variety of different Flux formulations. Since flux formulations have always been a trade secret for solder paste suppliers, it is not easy for users to know their actual characteristics. However, it can be foreseen that this change will have a greater impact on the welding process.
Manufacturer Lead-Free Plating Application
NEC Sn-Bi QFP, TQFP, LQFP, SOJ, SOP, TSOP
Ni-Au LGA
Fujitsu Sn-Bi QFP, SOP
HITACHI Sn-Bi QFP, SOP
Panosonic Ni-Pd-Au, Sn-Bi QFP, TQFP, LQFP, HQFP, QFJ, SOJ
Riyueguang Su-Cu, Sn-Bi QFP, TQFP, LQFP, HQFP, QFJ
Currently available lead-free solder alloys include the following: SnAg, SnCu, SnZn, SnAgCu
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