sales@ipcb.com
What is SMT technology?It is a process that involves the precise placement of Surface Mounted Devices (SMDs) on a Printed Circuit Board (PCB) at a specified location and ensuring that a solid electrical and mechanical connection is established between these components and the PCB through processes such as reflow soldering.Compared to the traditional through-hole insertion method,SMT SMD technology demonstrates multiple advantages.
Firstly, the compact size and light weight of SMD provides the possibility of achieving higher assembly density, enabling PCBs to integrate more functional modules. This feature is essential to promote the miniaturisation and multifunctionality of products, for example, those compactly arranged chips and components on the motherboard of a smartphone, it is with the help of SMT SMD technology, in order to achieve a powerful function in a limited space.
Secondly, SMT technology has a very high production efficiency and advanced automation level, which can quickly and accurately complete a large number of components placement work. This not only significantly shortens the product production cycle, but also effectively reduces production costs.
SMT SMD process:
1.Raw material inspection: first of all, conduct a comprehensive inspection of the PCB board to ensure that it is free of deformation, scratches, short circuits or open circuits and other issues,and verify that its soldermask, silkscreen layer and so on are in line with the established standards. At the same time, the appearance of the components, size and pin coplanarity of the inspection, and take some samples for electrical performance testing to ensure that they meet the design requirements.
2.Solder Paste Coating: According to the design of the PCB board and the specifications of the components,a suitable solder paste stencil is selected and installed on the solder paste printing machine. Through this machine, the solder paste is evenly coated on the pads of the PCB board.In this process,the thickness, shape and coating position of the solder paste need to be strictly controlled to ensure that the solder paste accurately covers the pads to avoid defects such as less tin, more tin, pulling the tip or offset.
3.Paste quality inspection:use SPI solder paste thickness gauge and other equipment to detect the quality of solder paste coating.Check whether the thickness of the paste is between 0.1 and 0.15 mm, to confirm whether the coating position is accurate, no offset or skewed phenomenon,and verify that the surface of the paste is smooth, no pulling the tip or collapse and other undesirable conditions.
4.Component placement: mounter according to the preset procedures,from the material belt or tray to pick up the corresponding surface mount components,and accurately mounted to the PCB board in the specified location. When mounting, special attention should be paid to the polarity and direction of the components to ensure the correctness. For tiny components, such as 0201, 01005 and other packages,the mounter needs to have higher precision and stability to ensure the quality of placement.
5.Reflow soldering: PCB boards into the reflow oven, under a specific temperature profile for welding.The temperature profile of the reflow oven, including preheating, warming,constant temperature, reflow and cooling and other stages, the need to accurately control the temperature, time and atmosphere and other parameters to ensure the quality of soldering. Preheating stage helps to volatilise the solvent in the solder paste to avoid air bubbles during reflow; reflow stage needs to ensure that the solder paste is completely melted to form a reliable soldering connection; cooling stage enables the solder joints to cool and solidify quickly to improve the strength of the soldering.
6.Quality Inspection: Visual inspection, automatic optical inspection (AOI), X-ray inspection, online tester (ICT), flying pin tester and function tester and other means to comprehensively test the quality of PCBA welding and assembly quality. Visual inspection is mainly through manual observation of PCBA surface defects; AOI uses optical imaging principle to quickly scan and detect welding defects; X-ray inspection is used to detect welding defects hidden inside the components, such as BGA.
7.Rework processing: for the defective products detected, the use of soldering iron, rework workstation and other tools for rework processing, to remove the bad welding points and re-welding, until the product quality meets the requirements. Rework need to be tested again to ensure that the product quality is qualified.
How to choose a good SMT service provider
1.Production equipment and technical strength: a high-quality SMT placement service provider should be equipped with advanced production equipment, such as high-precision placement machines, reflow soldering ovens and solder paste printers.The accuracy, speed and stability of these equipments have a direct impact on the quality and productivity of SMT placement. At the same time, the supplier also needs to have a wealth of technical strength, can master a variety of SMT placement technology, including high-precision component placement, multilayer board SMT placement and mixed assembly (i.e., including both SMD and through-hole components), in order to meet the diverse needs of different customers.
2.Quality management system:When choosing a SMT placement service provider, a perfect quality management system is an indispensable consideration.The supplier should establish a set of raw material inspection, production process monitoring to the finished product testing of the whole chain of quality management system, to ensure that each production link is in line with the established quality standards.For example,in the raw material inspection stage,the PCB board, components and solder paste and other raw materials should be strictly quality inspection;in the production process, the solder paste printing,component placement and reflow soldering and other key processes to real-time quality monitoring, in order to timely detection and correction of the problem; in the finished product testing stage,a variety of testing methods need to be used to ensure that product quality is flawless.
3.Supply chain management effectiveness:SMT chip production requires a large number of raw materials, including PCB boards,various SMD components and solder paste. Therefore, an excellent service provider should have excellent supply chain management performance to ensure the timely supply of raw materials and stable quality.This includes establishing long-term and stable relationships with many high-quality suppliers, and carrying out scientific planning and management of raw material inventory, so as to avoid production delays or product quality degradation triggered by raw material shortages or quality problems.
4.Technical support and after-sales service quality:in the SMT SMD production process, may encounter such technical difficulties as PCB design optimisation,component selection recommendations and production process adjustment.Therefore,a high-quality service provider should have a professional technical support team,able to provide customers with a full range of technical support and solutions.At the same time, after the delivery of the product,the supplier should also provide high-quality after-sales service,timely response and deal with customer feedback to ensure that customer satisfaction reaches the highest level.
SMT,as the core process in the PCBA manufacturing process,the entire process contains a number of key steps from raw material inspection, solder paste coating, component assembly, curing treatment, reflow soldering, cleaning operations, quality testing until rework and repair,etc., and each step is required to implement stringent control measures to protect the quality of the final product.