SZFitech

  What is lead-free solder? Lead-free solder (PB-free solder) means that the chemical composition of the solder does not contain lead (Pb), and the Rohs directive requires that the Pb content does not exceed 1000PPM or 0.1%. The main representative of lead-free solder is tin base solder, and the most used lead-free solder is tin silver copper lead-free solder, which is considered by the industry as the best choice to replace tin lead solder. The following is a summary of the practical and physical properties of lead-free solder alloys: Industrial practical requirements The application of lead-free solder alloys in the electronics industry needs to meet the following requirements to ensure their widespread use and reliability in actual production 1. Melting point: The melting point should be as close as possible to the SnPb eutectic filler metal (about 183 ° C), which can avoid substantial modifications to the existing equipment, process parameters and substrate, and ...

 The choice of solder paste, there is a comparison between lead solder paste and lead-free solder paste, mainly depends on the specific application scenario, environmental requirements, cost considerations and welding effect and other factors. The following is a detailed analysis of the advantages and disadvantages of both and the process: There's lead tin paste Advantages: Low cost: The cost of lead solder paste is relatively low, mainly due to the price advantage of its raw materials. Good welding effect: the solder joint with lead solder paste has high gloss, stable welding quality, and the requirements for reflow welding equipment are not high. High electrical conductivity and mechanical strength: Lead tin welding has high electrical conductivity and mechanical strength, which can meet the needs of most electronic products. Cons: Environmental problems: the lead solder paste contains lead, which is harmful to the environment and human health and does not meet the mo...

 1. What is tin-spraying/hot air smoothing Tin spray/hot Air finishing (HASL) is a PCB surface treatment process. By preparing a tin lead layer on the copper surface of the PCB, it can protect the pad from oxidation and maintain the solderability. The liquid solder used in HASL is usually composed of 63% tin and 37% lead, and the HASL layer is dissolved with the solder paste during SMT welding. HASL boards dominated the electronics manufacturing industry before the birth of lead-free processes. At present, although the use has declined, it is still widely used in medical, military, aerospace and other fields. Figure 1. HASL surface treatment layer. 2. HASL process steps The PCB needs to be cleaned before the HASL surface treatment, and the copper surface is cleaned by micro-etching. After cleaning, the PCB board is preheated and coated with flux. The flux can reduce the surface tension between the PCB and the solder, so that the solder is better covered on the PCB. Af...

 In the reflow welding process described in Figures 1 and 2, the role of flux and its relationship to the quality of the weld are critical. As a common connection technology in electronic manufacturing, reflow welding directly affects the reliability and stability of electronic products. The following is a detailed analysis of this process and the importance of nitrogen atmosphere welding. The role of flux The microstructure of the solder joint directly affects the mechanical and electrical properties of the solder joint, which mainly depends on the composition of the solder, melting and solidification process, interface reaction and aging conditions. FIG. 2 shows SEM photos of solder joints aged at 85°C. The Cu6Sn5 IMC layer is formed after reflow welding. In SnBi57.6Ag4 solder, there are Ag3Sn particles less than 1μm, and when 1%Ag is added to SnBi solder, large Ag3Sn IMC is formed on Cu6Sn5 layer. Figure 1. The role of flux in reflow welding process The importance of...

 In electronics manufacturing, (Open Circuit) is a common problem, which can cause the current in the circuit to fail to flow, thus affecting the function of the entire electronic product. We can further refine and expand these contents for the reasons of open circuit and its improvement suggestions. Cause and detailed analysis 1.1 Open circuit caused by pin coplanarity Coplanarity problems: There may be small differences in the height of the pins of the components (e.g. QFP pin ±25μm), which may cause some pins to fail to make adequate contact with the solder during welding. Solder paste thickness: The thickness of the solder paste printing also affects the solder joint quality. A paste that is too thin may not cover all pins, while a paste that is too thick may cause other problems (such as bridging). Solution: In addition to reducing the non-coplanarity of the pins and adjusting the thickness of the solder paste, you can also consider using components with better co...

  The wetting reaction of lead-free eutectic solder on the metallized layer under thick Cu bumps involves many aspects, the following is a detailed analysis of this process:   We compare the reactions of four different eutectic solders (SnPb, SnAg, SnAgCu and SnCu) on a thick Cu (15 μ m) UBM layer prepared by electroplating.       SEM photo of interconnect interface of 4 kinds of eutectic solders on Cu UBM layer after 2 reflow (c)   (a)SnPb; (b)SnAg; (e)SnAgCu; (d)SnCu     Optical microscope photos at the interface between Cu and 4 kinds of solders after solid aging at 170 ℃ for 1500h (a)SnPb; (b)SnAg; (c)SnAgCu; (d)SnCu     Formation of scalloped Cu6Sn5   Scalloped Cu6Sn5, a typical intermetallic compound (IMC) formed by Cu reacting with Sn-based solder, was observed in all samples.   The spiky Cu6Sn5 at the interface between lead-free solder and Cu is larger than that at the interface of SnPb solder, which may be related to t...

 As miniaturization continues and usage requirements become higher, the number of pads on the chip is also increasing. In order to meet the massive solder joint packaging, manufacturers prefer to use the printing process. The solder paste printing process is efficient and can complete large-area printing in a short time, which can be used for large-scale chip packaging. Solder paste is uniformly placed on the stencil, and a squeegee is used to fill the solder paste in the stencil openings. After the solder joints are printed, it needs to melt and solidify into solder joints through a reflow soldering process. Transfer efficiency is related to the stencil opening and squeegee's speed. Due to the shear force, the speed of the squeegee affects the viscosity change and the transfer efficiency of solder paste through the apertures. In addition, the size of the opening affects the amount of solder paste that deposits on the pads. The relationship between aperture size and ...

 A soft error is a temporary failure of a device caused by the effects of radiation on a silicon integrated circuit (Si ICs). Soft errors can affect the performance and reliability of equipment, especially in high-radiation environments such as space, defense, medical, and power systems. As electronic devices continue to miniaturize and denser, the sensitivity of soft errors increases, because low-energy alpha particles can now flip a memory bit or change the timing of a logic circuit. One of the main sources of alpha particle radiation is the solder paste used to connect components in the package, which contains alpha radioactive elements. Thanks to the use of flip-chip and the move to 3D packaging, solder bumps have moved so close to the moving silicon device that even low-energy alpha rays can cause soft errors. Therefore, it is necessary to develop Low Alpha activity Pb-free solders to reduce the occurrence of soft errors. Alpha particle source of solder Lead-base...