Twelve Questions And Answers Explain What Is SMT Assembly?
Many people have questions about SMT assembly, such as "What is SMT assembly"? "What are the attributes of SMT assembly?" In the face of various questions from customers, the editor specially compiled a question and answer material to answer your doubts.
Q1: What is SMT assembly?
A1: SMT, short for surface mount technology, refers to an assembly technology used to paste components (SMC, surface mount components or SMD, surface mount devices) through a series of SMT assembly equipment to expose the PCB (printing Circuit board).
Q2: What equipment is used in SMT assembly?
A2: Generally speaking, the following equipment is suitable for SMT assembly: solder paste printer, placement machine, reflow oven, AOI (automatic optical inspection) instrument, magnifying glass or microscope, etc.
Q3: What are the attributes of SMT assembly?
A3: Compared with traditional assembly technology, namely THT (Through Hole Technology), SMT assembly leads to higher assembly density, smaller volume, lighter product weight, higher reliability, and higher impact resistance , Lower defect rate, higher frequency, lower EMI (Electromag netic interference) and RF (radio frequency) interference, higher throughput, more automated access, lower cost, etc.
Q4: What is the difference between SMT assembly and THT assembly?
A4: SMT components are different from THT components in the following aspects:
a. Components used for THT components have longer leads than SMT components;
b. THT components need to be drilled on the bare circuit board, while SMT assembly is not required, because the SMC or SMD is directly mounted on the PCB;
c. Wave soldering is mainly used in THT assembly, while reflow soldering is mainly used in SMT assembly;
d. SMT assembly can be automated, while THT assembly only depends on manual operations;
e. The components used for THT components are heavy, high, and bulky, while SMC helps to reduce more space.
Q5: Why are SMT components widely used in the electronics manufacturing industry?
A5: First of all, current electronic products have been working hard to achieve miniaturization and light weight, which is difficult to achieve in THT assembly;
Secondly, in order to enable electronic products to be functionally integrated, IC (integrated circuit) components are fully utilized to a large extent to meet large-scale and high-integrity requirements, which is exactly what SMT assembly can do.
Third, SMT assembly adapts to mass production, automation and cost reduction, all of which meet the needs of the electronics market;
Fourth, the application of SMT assembly to better promote the development of various applications of electronic technology, integrated circuits and semiconductor materials;
Fifth, SMT assembly complies with international electronic manufacturing standards.
Q6: In which product areas are SMT components used?
A6: At present, SMT components have been applied to advanced electronic products, especially computer and telecommunications products. In addition, SMT components have been applied to products in various fields, including medical, automotive, telecommunications, industrial control, military, aerospace, etc.
Q7: What is the common manufacturing process for SMT assembly?
A7: SMT assembly procedures usually include solder paste printing, chip mounting, reflow soldering, AOI, X-ray inspection and rework. Perform a visual inspection after each step of the procedure.
SMT in the flow welding process
Q8: What is solder paste printing and its role in SMT assembly?
A8: Solder paste printing refers to the process of printing solder paste on the pads on the PCB, so that the SMC or SMD can be stuck to the board through the left solder paste on the pads. Solder paste printing is achieved through the application of a template. There are many openings on the template, and the solder paste will remain on the pad.
Q9: What is chip mounting and its role in SMT assembly?
A9: Chip mounting contributes to the core meaning of SMT assembly. It refers to the process of quickly placing SMC or SMD on SMT components. The pad remains on the PCB pad. Therefore, based on the adhesive force of the solder paste, the components will temporarily stick to the surface of the circuit board.
Q10: Why is the welding type used in the SMT assembly process?
A10: Reflow soldering is used in SMT assembly to permanently fix the components on the PCB, and it is carried out in a reflow soldering furnace with a temperature zone. In the process of reflow soldering, the solder paste is first melted in the first and second stages at a high temperature. As the temperature decreases, the solder paste will harden, so the components will be fixed on the corresponding pads on the PCB.
Q11: Do I need to clean the PCB after SMT assembly?
A11: The PCB assembled by SMT must be cleaned before leaving the workshop, because the surface of the assembled PCB may be covered by dust, residues after reflow soldering, such as flux, all of which will reduce the reliability of the product to a certain extent. Therefore, the assembled PCB must be cleaned before leaving the workshop.
Q12: What type of inspection is used for SMT assembly?
A12: In order to ensure the quality and performance of the assembled PCB, it is necessary to check during the entire SMT assembly process. Many types of inspections must be used to reveal manufacturing defects, which will reduce the reliability of the final product. Visual inspection is the most commonly used in SMT assembly. As a direct inspection method, visual inspection can be used to indicate some obvious physical errors, such as component displacement, missing components or irregular components. Visual inspection is not suitable for visual inspection, and some tools such as magnifying glass or microscope can also be used. In order to further point out the defects of the solder balls, AOI and X-ray inspection can be used after the soldering is completed.
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