Application of AOI inspection equipment in SMT AOI inspection equipment is mainly used to detect defects in solder paste and devices: 1,Solder paste inspection is not very difficult, there are mainly two types of technology: color 3-color light source and multi-view. Solder paste detection is usually carried out after the solder paste printing, to carry out effective solder paste detection, the detection system must not only provide information on the area of the printed solder paste, but also should be able to provide volume and height information, if only consider the area information without regard to height information, the amount of solder paste on the pad is not enough will also lead to unreliable detection through. After the printed solder paste curing, the use of multi-level camera process technology, multiple lighting angles and 2-D system, it can quickly and sensitively capture the PCB, solder mask and solder paste appearance of the color change, the use of 3-D system, it can provide information about the solder paste area, as well as the height and volume of the solder paste ** information, but also according to the surface of the metal traces, PCB or solder mask, to determine the thickness of the solder paste 2,For device inspection, AOI inspection systems are usually installed before and after reflow soldering in SMT lines. The use of qualified sample-based learning and SMT-based CAD data detection, the specific technology is mainly based on the pattern recognition of pre-processed images, the former mainly uses statistical pattern recognition, through learning to establish qualified image patterns, and then through the comparison of the image of the detection object and sample image processing and arithmetic to obtain detection and identification results (1) Before reflow: The inspection is done after the components are placed inside the solder paste on the board and before the PCB is sent to the reflow oven. This is a typical location to place the inspection machine, as most defects from solder paste printing as well as machine placement can be found here. The quantitative process control information generated at this location provides information on the calibration of high speed chip machines and close pitch component placement equipment. This information can be used to modify component placement or to indicate that the placement machine needs to be calibrated. Inspection at this location satisfies the process tracking objective. (2) Post-Reflow:Inspection is performed at the *last* step of the SMT process, which is a popular choice for current AOI inspection equipment, as this location can find all assembly errors. Post reflow inspection provides a high degree of accuracy as it identifies errors caused by the solder paste printing, component placement and reflow process. Concluding remarks: A good process monitoring strategy should include a number of overlapping tools such as in-circuit testing (ICT), optical inspection, functional testing and cosmetic inspection. These processes overlap and complement each other in order to be *very* efficient.

What to learn in the SMT industry Many smt industry friends think, in SMT this industry, is to learn SMD machine, think only engage in SMD machine is considered to do SMT, in fact SMT (surface assembly technology) should also include many aspects:. Surface assembly components, surface assembly circuit board and graphic design, surface assembly special auxiliary materials - solder paste, SMD adhesive, surface mount equipment, surface assembly material soldering technology (including wave soldering, reflow soldering, etc.), surface testing technology, cleaning technology and quality management, surface assembly production management and other aspects of the content. The above content can be summarized into three aspects. 1, equipment, which means the SMT hardware aspects. 2, process, and SMT process technology, that is, the software side. 3, electronic components and packaging technology, which is the basis of SMT, but also the driving force of SMT development, which drives the SMT special equipment and process The continuous development of technology. For example, the component packaging to 0201, equipment and technology must also keep up accordingly. Surface assembly technology is a group of technology-intensive, know intensive technology group, involving components packaging, PCB technology, printing technology, automatic control technology, welding technology, physics, chemical, new materials and other professional and discipline. For example, the placement machine involves computers, image recognition systems, sensors, servo systems, etc., professional involving machine, electricity, light and other disciplines. Therefore, do not just think that only engaged in the chip machine is considered to engage in SMT, process, materials are as important, production management can also be involved in the future of the road will be wider and wider.

Evaluation of a placement machine vision system for SMD placement alignment I. Support for multiple types of cameras    Previously the time to process images has always been longer than the time to acquire them, but new developments in CPU technology have accelerated image processing, and image acquisition speed may instead become a limiting factor. In order to improve system processing efficiency, to reduce the time to acquire images to a * low degree, the vision system should be able to support a variety of advanced line scan, high resolution (1024 × 1024 pixels), high-speed digital cameras.   Second, identify non-standard device capability    Machine vision systems should be able to reliably identify the shape of various non-standard devices, regardless of how rare they are. The existing patch alignment software, with built-in geometric pattern finding tools, these tools can "learn" the geometric properties of the device, even if it is oddly shaped, the system can identify the device.   Three, the ability to reliably avoid the nozzle    SMD component placement generally uses either front lighting or backlighting, or both. Backlighting is used to produce a back image of the device, revealing an image similar to a binary image, making it easier for the vision system to identify the device, and this type of lighting is often used when identifying simple devices such as chip resistive capacitors. However, backlighting can also pose a problem for the vision system: the back image of the pickup device's nozzle often protrudes from the back of the device or partially obscures the chip (e.g., Figure 10). While frontal illumination techniques can prevent this phenomenon, the pixel grayscale values of the nozzle itself may prevent the vision system from reliably distinguishing between the nozzle and the device. Choosing a vision system that can recognize the difference in shape between the device and the pick-up device's nozzle, such a system can tolerate partial masking of the nozzle and therefore will improve device alignment accuracy and prevent devices from being misplaced due to visual errors.   IV. Ability to identify closely spaced devices and white ceramic surface devices    In order to **identify various devices such as BGAs, flip-chips or CSPs, and to check for pin deviations, the vision system should reliably identify white ceramic surface devices, whose low-contrast reflective nature would render conventional vision techniques useless. The vision system must also be able to accurately locate each component. These functions should be verified, and the test software should be able to distinguish between individual objects.   V. Ability to automate programming   For very special components, new vision software tools should have the ability to automatically "learn", the user does not have to manually input parameters into the system to create a device description from scratch, they just need to take a picture of the device to the vision camera can be, the system will automatically produce a comprehensive description similar to CAD. This technology can improve the accuracy of device descriptions and reduce many operator errors, speed up the creation of component libraries, especially in the case of frequent introduction of new devices or the use of uniquely shaped devices, thereby improving production efficiency.   Six, the ability to reliably determine the location of the PCB reference mark    Since reliable positioning of PCB reference marks is the **step** to any SMD placement alignment, the vision system must be able to identify different references, even in conditions where the appearance of the reference is not ideal. For example, variations in oxidation, tinning, and wave solder from the manufacturing process can cause specular reflections and surface inconsistencies that can dramatically change the appearance of the marker. Other factors that may affect the appearance of the reference include board distortion, excessive solder buildup, board color changes, and more. A vision system that tolerates these conditions can help users improve alignment success and reduce operator intervention.     Taking these factors into account ensures that you can easily handle new component types and different devices from different manufacturers, and that the system you choose is highly flexible, making the user's job easier.

Common structure of SMD machine The structure of SMD machine can be divided into 4 types of structure: compound type, arch type, turret type and large parallel system. 1、Compound type. Composite machine is developed from the arch type machine, it combines the features of turret type and arch type, there are turntables installed on the movable arm, like Siemens' Siplace 80S25 bonder, there are two rotary heads with 12 nozzles. Since the compound machine can increase the speed by increasing the number of movable arms, it has more flexibility, so its development prospect is favored, such as Siemens introduced the HS60 machine is installed with four rotary head, placement speed of up to 60,000 pieces per hour. universal also introduced the rotary head with 30 nozzles, called " Lightning Head", two such rotary heads mounted on the Genesis placement platform, can achieve a placement speed of 60,000 pieces per hour. In a strict sense, the composite machine still belongs to the moving arm structure.   2、Arch type. Arch-frame (also known as moving arm) machines are *traditional* bonder machines with better flexibility and accuracy for most components, high precision machines are generally of this type, but their speed cannot be compared with compound, turret and mega parallel systems. The arch type machine is divided into single arm type and multi-arm type. The single arm type is the *early developed multifunctional bonder still in use today. The dobby mounter developed on the basis of the single-arm type can increase the work efficiency exponentially, such as the GSM2 mounter of Universal Corporation in the United States has two movable arm mounting heads, which can alternately mount two PCBs (PrintCircuitBoard) at the same time. The majority of bonder manufacturers have introduced high-precision bonder and medium-speed bonder with this structure, such as AC72 from Universal, AQ-1 from Assembleon, TIM-X from Hitachi, QP-341E and XP series from Fuji, BM221 from Panasonic, and BM221 from Samsung. BM221, CP60 series from Samsung of Korea, YV series from Yamaha of Japan, and KE series from Juki of Japan. However, the component arrangement is increasingly concentrated on active parts, such as leaded QFP (Quadflat package, Quadrilateral flat package device) and BGA (Ball gridarray, Ball grid array device), where mounting accuracy plays a vital role in high yield. Composite, turret and large parallel systems are generally not suitable for this type of component mounting.   3. Turret type. Turret type machines are mainly used in the production of large-scale computer boards, cell phones, home appliances and other products, this is because in these products, resistive components are particularly large, high assembly density, very suitable for ** with this model for production. A considerable number of Taiwan-invested, Hong Kong-invested electronic assembly enterprises and domestic electrical manufacturers are using this model to meet the requirements of high-speed assembly. The concept of the turret is to use a set of moving feeders from which the turret picks up components and then places them on top of the circuit board located on a moving table. The turret type machine makes the placement speed increase significantly due to the simultaneous picking up of components and placement action. This kind of structure high speed mount machine in our country's application is also very common, not only the speed is fast, and after more than ten years of development technology has been very mature, such as Fuji company's CP842E machine mount speed can reach 0.068 seconds / piece. But this kind of machine because the mechanical structure is limited, its pasting speed has reached a limit value, not possible to improve greatly again. The shortcoming of this model is only can deal with the strip material.   4、Massive parallel system. Large-scale parallel system (also called module machine) uses a series of small individual placement unit (also called module). Each unit has its own filament position system, mounted with a camera and a mounting head. For example, Assembleon's AX-5 machine can* have up to 20 placement heads, achieving a placement speed of 150,000 pieces per hour, which is considered to be the industry**, but for each placement head, the placement speed is around 7,500 pieces per hour, and there is still a possibility of substantial improvement. This type of machine is also mainly suitable for large-scale production, such as cell phones. The manufacturer who produces the mass parallel system type machine mainly has Assembleon, Fuji also launched the NXT type super high speed mounter which adopts the similar structure, by carrying the mount work head which can be changed, the same machine can be both the high speed machine and the universal machine, almost can carry out the mount of all mount components, thus the initial investment of the equipment and the increase equipment investment is reduced to * Low degree. Each place

Instructions for buying reflow soldering At present, electronic product PCB boards continue to miniaturize, chip components appear, the traditional welding method can not adapt to industry requirements. With SMT the whole technical development is becoming more and more perfect, a variety of chip components (SMC) and mount devices (SMD) appear, as part of the placement technology reflow soldering process technology and equipment has also been developed accordingly Then buy reflow soldering to understand which parameters? Affect the quality of reflow soldering have the following main parameters. 1. temperature control accuracy should be in the soil 0.1 ~ 0.2 ℃; (temperature sensor sensitivity to meet the requirements). 2. The width of the conveyor belt to meet the * large PCB size requirements. 3. The lateral temperature difference of the conveyor belt should be less than 5℃, otherwise it is difficult to ensure the quality of welding. 4. should have a temperature curve test function, if the equipment does not have this configuration, should be purchased outside the temperature curve collector. 5. The longer the length of the heating zone, the more the number of heating zones, the easier it is to adjust and control the temperature curve. General small and medium-sized production selection of 4-5 temperature zones, heating zone length of about 1.8m reflow furnace that can meet the requirements. In addition, the upper and lower heaters should be independent temperature control, in order to adjust and control the temperature curve. 6. Conveyor operation should be smooth, conveyor vibration will cause displacement, suspension bridge, cold welding and other welding defects. 7.* The high heating temperature is generally 300~350℃, if lead-free solder or metal substrate is considered, more than 350℃ should be selected.