SMT Quality Terminology 1、The ideal solder joint   Good surface wettability, that is, the molten solder should be spread on the surface of the metal being soldered and form a complete, uniform and continuous solder coverage layer, the contact angle of which should be no greater than 90.    The correct amount of solder, the amount of solder is sufficient but not too much or too little    Good soldering surface, the surface of the solder joint should be complete, continuous and rounded, but does not require a very shiny appearance.    Good solder joint position component's solder end or pin on the pad position deviation within the specified range. 2、No wetting    The solder on the solder joint and the soldered metal surface to form a contact angle greater than 90 degrees. 3、Open soldering    After soldering, the pads are separated from the PCB surface. 4、Drawbridge (drawbridging)    One end of the component leaves the surface of the solder pad to the upper diagonal or upright, also known as the tombstone (Tomb stone). 5, bridging    Two or more should not be connected between the solder joints connected to the solder, or solder joints of the solder and adjacent wires connected. 6、False soldering    After soldering, the solder end and the pad between or between the pins and pads sometimes appear electrical isolation phenomenon 7、Pull tip    Solder joints appear in the solder has a prominent outward burr, but no contact with other conductors or solder joints 8、Solder ball (solder ball)    Soldering adhered to the printed board, negative solder film or conductors on the solder ball, also known as tin beads. 9、Holes    Solder holes of varying apertures 10、Position shift (skewing )    Solder joints in the plane lateral, longitudinal or rotational direction deviation from the intended position. 11、Visual inspection method (visual inspection)    With the aid of a 2-5 times magnifying glass illuminated, the quality of PCBA solder joints is inspected by visual observation. 12, after welding inspection (inspection after aoldering)    PCB quality inspection after completion of welding. 13、Reworking (reworking)    To remove local defects in the surface assembly components of the repair process. 14、Placement inspection ( placement inspection )    Surface mount component placement or after completion, for whether to miss paste, misalignment, paste wrong, damage and so on the situation of quality inspection.

Electric plug PCB need to follow which design specifications 1. Scope This standard specifies the use of automatic plug-in machine for electronic assembly of electronic products in the design of printed circuit boards (hereinafter referred to as printed circuit boards) should follow the technical specifications. This standard applies to the use of automatic plug-in machine design of printed circuit boards. 2. Reference standards The provisions contained in the following standards become the provisions of this standard by referencing them in this standard, and the versions shown are valid when this standard is published. All standards are subject to revision, and parties using this standard should explore the possibility of using the * new version of the following standard: FSX40036-1995 Single-sided printed circuit board design guidance specifications. 3. Requirements Other design requirements of the printed circuit board shall be in accordance with FSX40036-1995. The shape of the printed board: the shape of the printed board should be rectangular, with the radius of the four corner arcs between 2 and 4mm; * the large size is: 400mmX300mm, * the small size is: 150mmX100mm. The warpage of the printed board: * the big upward warpage 0.5mm, * the big downward warpage 1.2mm  When the printed board needs to be partially cut off the edges or corners, the method of process punching should be used so that the part to be cut off can be retained until the automatic insertion process is completed and then removed. If the edge is to be opened, the width of the opening should not exceed 3mm and the depth should not exceed 30mm; the distance between the opening and the nearby corner should be more than 35mm; there should not be more than 5 openings on the same edge; avoid opening on the long edge as much as possible. Translated with www.DeepL.com/Translator (free version)

SMT Basics I. Introduction to the traditional process     The traditional perforated electronic assembly process is to insert the pins of the component into the PCB guide holes after fixing, using the wave soldering (WaveSoldering) process, as shown in Figure 1, after flux coating, preheating, solder coating, inspection and cleaning steps to complete the entire welding process. Introduction to Surface Bonding Technology    As products in the electronics industry continue to be designed to be shorter and lighter with time and trends, the size and weight of various components are becoming smaller and smaller, and their functional density is also relatively higher in order to meet the trend of the times and customer needs. The main feature is that it can be used as a space-saving alternative to the traditional dip-solder assembly (DualIn Line Package; DIP). The surface mount assembly process consists of the following main steps: solder paste printing, component placement and reflow soldering. The steps are outlined below.     StencilPrinting: Solder paste is the material used to connect the surface bonded components to the PCB. After the steel plate is etched or laser cut, the squeegee of the printing machine prints the paste onto the PCB pad through the holes in the steel plate in order to proceed to the next step.     ComponentPlacement: Component placement is the key technology and focus of the entire SMT process, which uses highly sophisticated automated placement equipment, programmed by computer, to accurately place surface-adhesive components onto the solder pads of the printed PCB. As the design of surface mount assemblies becomes more sophisticated, the pitch of the pins becomes smaller and the technical level of the placement process becomes more and more difficult.     ReflowSoldering: Reflow soldering is the process of placing the PCB with surface adhered components, preheating it in a reflow oven to activate the flux, then raising the temperature to 183°C to melt the solder paste and connect the component pins to the PCB pad, then cooling it down to cure the solder, which completes the bonding of the surface adhered components to the PCB. III. Explanation of SMT common names     SMT : surface mounted technology: an assembly technology in which surface-mounted components are directly mounted and soldered to the surface of a printed circuit board at specified locations.     SMD : surface mounted devices: rectangular shaped, cylindrical or heterogeneous electronic components with solder ends or pins made in the same plane and suitable for surface adhesion. Reflow soldering: The mechanical and electrical connection between the terminals or pins of a surface-adhesive component and a printed circuit board solder pad by remelting a paste that has been pre-assigned to the pad.     Chip : rectangular chip component (rectangular chip component): a surface-adhesive component with no leads at both ends, with solder ends, and a thin rectangular shape.     SOP : small outline package (small outline package): a small moulded plastic package with short wing or J-shaped pins on both sides, a surface assembly component.     QFP : quad flat pack: a plastic package with short wing-shaped pins on all four sides, with a pin pitch of 1.00, 0.80, 0.65, 0.50, 0.40, 0.30mm, etc. for thin surface assembled collective circuits.     BGA: Ball grid array: a form of packaging for integrated circuits in which the input and output points are tin balls arranged in a grid pattern on the bottom surface of the assembly. IV. Assembly packaging methods.     Magazine/stick (shipping tube) - the main component container: the magazine/stick consists of a transparent or translucent polyethylene (PVC) material extruded into a standard form that meets current industry standards for application. The dimensions of the strips provide the appropriate positioning and orientation of the components for industry standard automatic assembly equipment. The strips are packaged and shipped in individual strip quantity combinations.     Trays (trays) - the main component container: trays are made of toner or fibre materials, which are selected based on the *high* temperature rate of the special trays. Trays designed for components that require exposure to high temperatures (moisture sensitive components) have a temperature resistance of typically 150°C or higher. The trays are moulded into a rectangular standard profile and contain a uniform matrix of interlocking cavities. The cavities hold the components and provide protection for the components during transport and handling. The spacing provides accurate component positioning for standard industrial automated assembly equipment used for placement in the circuit board assembly process. The pallets are packed and transported as a combination of individual pallets which are then stacked and bundled together with some rigidity. An empty-covered pallet is placed on top of the assembled compone

SMT Basics knowledage Features of SMT 1. High assembly density, small size and light weight of electronic products, the volume and weight of SMD components is only about 1/10 of traditional cartridge components, generally after the use of SMT, electronic products volume reduction of 40% to 60%, weight reduction of 60% to 80%. 2. High reliability, strong resistance to vibration. Low defect rate of solder joints. 3. 3. Good high frequency characteristics. Reduced electromagnetic and radio frequency interference. Easy to automate and improve production efficiency. Reduces costs by up to 30% to 50%. Saves material, energy, equipment, manpower, time, etc. Why use surface mount technology (SMT) 1. Electronic products pursue miniaturisation, the previously used perforated insert components can no longer be reduced in size 2. electronic products more complete function, the integrated circuit (IC) used has no perforated components, especially large-scale, highly integrated IC, had to use surface mount components 3. product batching, production automation, the factory must be low cost and high yield, production of superior products to meet customer demand and strengthen market competitiveness 4. development of electronic components, integrated circuits (ICs) and diversified applications of semiconductor materials

X-Ray Inspection AXI AXI is a new test technology that has emerged in recent years. When the assembled circuit board (PCBA) enters the inside of the machine along the rail, there is an X-Ray transmitter tube located above the board, and the X-rays emitted through the board are accepted by the detector (usually a camcorder) placed below. X-rays are absorbed in large quantities, and a good image is produced as a black spot (as shown in Figure 2), making the analysis of the solder joint quite intuitive, so a simple image analysis algorithm can automatically and reliably check for defects in the solder joint.   Advantages and disadvantages of AXI testing Advantages. (1) Up to 97% coverage of process defects. Defects that can be inspected include: dummy solder, bridging, standing stones, insufficient solder, air holes, device leakage, etc. Especially, X-RAY can also inspect solder joint hidden devices such as BGA and CSP. (2) Higher test coverage. It can check the places that cannot be checked by naked eye and in-line test. For example, if the PCBA is judged to be faulty and the PCB inner alignment is suspected to be broken, X-RAY can check it quickly. (3) The preparation time of the test is greatly reduced. (4) Defects that cannot be reliably detected by other testing means can be observed, such as: false soldering, air holes and molding, etc. (5) Only one inspection is required for double-sided and multilayer boards (with delamination function). (6) Provides relevant measurement information that can be used to evaluate the production process. Such as solder paste thickness, amount of solder under the solder joint, etc. Disadvantages: AXI technology cannot test for defects and faults in the electrical performance of the circuit. Now the application of BGA is more and more, the market requirements for the detection of BGA is also increasing, and even require 100% detection, hoping that in the automatic online detection of PCB board defects, detection speed is faster. But in the PCB assembly plant, the use of off-line X-ray inspection. Rarely used online X-ray detection. There are several reasons, * the biggest problem is the higher price of online X-ray inspection equipment; ** is the automatic online detection of defects in this machine is poor, a lot of misjudgment; third is its detection speed is relatively slow. X-ray inspection is usually used in the AOI detection of components that can not be detected, a board of many components can be detected with AOI, while the bubble can only be seen with X-ray. A large board, there are usually thousands of resistors, capacitors. bga may only be about one to three, these bga can be detected with x-ray. aoi detection speed is very fast, two-dimensional x-ray detection speed is also very fast, if you do three-dimensional processing, the speed will be a little slower. Now BGA less, so do BGA detection, you can use more AXI detection, that is, when doing the slicing process, you can do more layering process. In summary, axi and aoi combined use is the trend of industry development.