{"id":3642,"date":"2026-10-29T14:34:40","date_gmt":"2026-10-29T06:34:40","guid":{"rendered":"http:\/\/www.fnnbd24.com\/blog\/?p=3642"},"modified":"2026-10-29T14:34:40","modified_gmt":"2026-10-29T06:34:40","slug":"how-to-adjust-the-sensitivity-of-aoi-machines-4d21-016308","status":"publish","type":"post","link":"http:\/\/www.fnnbd24.com\/blog\/2026\/10\/29\/how-to-adjust-the-sensitivity-of-aoi-machines-4d21-016308\/","title":{"rendered":"How to adjust the sensitivity of AOI Machines?"},"content":{"rendered":"

If you work in electronics manufacturing, you know how critical automated optical inspection (AOI) machines are for catching defects before a circuit board leaves the factory. But I\u2019ve lost count of how many times customers call me, frustrated, because their AOI is either flagging every tiny scratch as a critical error (wasting labor time rechecking good boards) or missing a broken solder joint (leading to product recalls down the line). As someone who\u2019s been selling AOI systems for 12 years\u2014walking manufacturing teams through installation, calibration, and adjustment every week\u2014I can tell you this: adjusting sensitivity isn\u2019t a one-size-fits-all task. It\u2019s a balance, and getting it right makes or breaks your production efficiency. AOI Machines<\/a><\/p>\n

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Let\u2019s start with the basics. AOI sensitivity is essentially how \u201cperceptive\u201d the machine\u2019s cameras and software are to tiny differences in light, color, and shape on a printed circuit board (PCB). When you set it too high, you get \u201cfalse positives\u201d\u2014defects that don\u2019t actually exist. Too low, and you get \u201cfalse negatives\u201d \u2014real defects that slip through. But here\u2019s what most new operators don\u2019t realize: sensitivity settings aren\u2019t static. They change with your board type, component size, and even the lighting in your factory. A few years ago, a mid-sized automotive PCB manufacturer bought our mid-range AOI system and set the sensitivity to the default level. Within a week, their line was running 20% slower because inspectors spent 3 hours a day clearing false positives for minor copper scratches that never caused a problem in the field. They adjusted it, cut recheck time by 85%, and hit their production targets 3 days ahead of schedule. That\u2019s the power of getting this right.<\/p>\n

First, let\u2019s talk about pre-adjustment prep\u2014something I see skipped all the time, and it\u2019s the #1 reason sensitivity adjustments go wrong. You can\u2019t just dive into the machine\u2019s settings without checking three core things: your reference board, your lighting, and your camera calibration. Let\u2019s break each down. Your reference board is your gold standard\u2014this is a PCB you\u2019ve already inspected manually that has no defects, no scratches, and perfect solder joints. If your reference board has a tiny flaw, the machine will use that as its benchmark, leading to all kinds of off settings. I always tell customers to create a new reference board every 6 months, or whenever you switch to a new PCB thickness, solder mask type, or component vendor. The second thing is lighting. AOI machines use ring lights, side lights, and sometimes backlights, and their intensity has to match the environment and the board\u2019s surface. If a PCB has a glossy solder mask, bright lighting will create reflections that the machine mistakes for defects, while too dim lighting will make tiny cracks invisible. Last month, a medical device customer switched from leaded to lead-free solder and their AOI was missing cold solder joints. They didn\u2019t adjust the sensitivity\u2014they just cranked up the lighting on the side lights, which highlighted the rough surface of lead-free solder that the cameras had been missing. That\u2019s a common mistake: people blame sensitivity when it\u2019s actually a lighting issue. Third is camera calibration. Every few months, a camera can shift or get dusty, which warps the image. We include a calibration pad with every AOI machine, and I insist operators run it once a week. Skip that, and even a perfectly tuned sensitivity setting will be off because the camera isn\u2019t aligned properly.<\/p>\n

Once you\u2019ve done the prep, it\u2019s time to adjust sensitivity. There are two main ways to adjust it on our AOI systems: per-defect thresholding and overall sensitivity scaling. Let\u2019s explain both, because you\u2019ll use them together. Overall sensitivity scaling is a quick, high-level adjustment\u2014good for when you\u2019re first testing a new board type. It\u2019s like turning a volume knob: higher volume means the machine picks up smaller differences, lower volume means it ignores minor variations. Per-defect thresholding is more granular, and that\u2019s where you\u2019ll get real efficiency gains. For example, if your biggest issue is missing open solder joints, you can adjust the open joint threshold higher without changing the settings for scratches, which cuts down on false positives while catching more real defects.<\/p>\n

Here\u2019s the step-by-step process I walk every customer through when they\u2019re adjusting sensitivity for the first time, and I\u2019ve seen it work for everything from small startup PCB lines to large automotive manufacturing facilities. First, load your reference board and run a full scan without making any sensitivity changes. Log how many false positives and false negatives the machine reports. This is your baseline\u2014if you skip this, you won\u2019t know if your adjustments are working. Second, adjust overall sensitivity in small increments. Start at 70% (our default is usually 65%, but I like to start a bit higher for testing). Run another scan, compare the false positives and negatives to your baseline. If false negatives go down but false positives jump up, you know you\u2019re pushing it too high. If false positives go down but you\u2019re still missing defects, bump it up 5% at a time\u2014no bigger. Small adjustments prevent you from swinging too far one way. Third, use per-defect thresholding to fine-tune. Let\u2019s say your baseline shows 12 false positives from copper scratches and 3 false negatives from micro-vias. You can go into the \u201cscratches\u201d defect category and lower its threshold, while going into \u201cmicro-vias\u201d and raising its threshold. This is way more effective than adjusting the overall setting, because you\u2019re not messing with other defect types. A customer making wearable electronics recently told me that this granular setting cut their defect recheck time in half, because they only adjusted settings for the tiny, high-priority defects, not everything. Fourth, test with actual production boards, not just reference boards. Reference boards are perfect, but real boards have tiny, harmless variations like tiny flux residue spots. Run 50 to 100 production boards through the adjusted AOI and count how many defects are missed. If you\u2019re missing more than 0.1% of defects (the industry standard for most products), you need to adjust up a little. If you have more than 1% false positives, you need to adjust down.<\/p>\n

Now, there are common pitfalls to avoid when adjusting sensitivity, and these are the mistakes that make even experienced operators call me panicking. First, adjusting sensitivity in a hurry during a run. I see this all the time: a production line has a small defect rate, so an operator cranks sensitivity up to catch it, and by the end of the shift, false positives are clogging the line. Always adjust sensitivity during a non-production test run, not while the line is running. Second, ignoring component size. Tiny 0201 components (super small surface-mount parts) need higher sensitivity than large power connectors, because a tiny solder joint on an 0201 is a critical defect, while a small gap on a power connector might not be. Most modern AOI systems let you set sensitivity per component type, so use that feature. Third, forgetting to update settings when you change materials. Solder mask changes from matte to glossy, PCB material changes from FR-4 to a high-temperature substrate\u2014all of these change how light reflects, so your sensitivity settings need to change too. Last quarter, a customer making high-voltage PCBs switched to a new flame-retardant PCB material, and their old sensitivity settings missed solder bridging defects for a week. They didn\u2019t realize the new material\u2019s color was different, so they needed to adjust the brightness sensitivity threshold. We give all our customers a material guide to help with this, but it\u2019s easy to miss when you\u2019re swamped with production.<\/p>\n

Once you\u2019ve adjusted sensitivity, the work doesn\u2019t stop there. You need to document your settings and calibrate them regularly. I always tell customers to log every adjustment: when you changed it, what board type it was for, what defect rates you saw. This way, if you switch back to an old board type 6 months later, you don\u2019t have to start from scratch. We also recommend rechecking sensitivity settings every 2 weeks for high-volume lines, and every 4 weeks for lower-volume lines. For example, a laptop manufacturer runs their line 24\/7, so we suggest they do a quick sensitivity check every shift, just to make sure nothing shifted with lighting or camera alignment.<\/p>\n

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If you\u2019re still struggling, don\u2019t hesitate to reach out. Every AOI system is tailored to your production needs, and we don\u2019t believe in one-size-fits-all settings. Whether you\u2019re dealing with a high defect rate, too many false positives, or just not sure how to adjust for your specific board, our team of engineers has walked through this with hundreds of manufacturers. We can even schedule a remote walkthrough to look at your settings, or come on-site to calibrate and adjust your AOI in person, no matter where you\u2019re located. Getting your sensitivity right is one of the fastest ways to cut production costs, reduce waste, and ensure your products are defect-free. If you\u2019re ready to optimize your AOI performance, reach out to our team today to discuss your specific needs. We\u2019re here to help you make your line run smoother, faster, and more reliably.<\/p>\n

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Ceramic Substrate AOl Inspection<\/a> References:<\/p>\n

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  1. "Automated Optical Inspection (AOI) for PCB Manufacturing: A Practical Guide," International Institute of Printed Circuits, 2022.<\/li>\n
  2. "Sensitivity Tuning in Machine Vision Systems for Electronics Assembly," Journal of Electronics Manufacturing, Vol. 31, No. 2, 2021.<\/li>\n
  3. Best Practices for AOI Calibration and Adjustment, Surface Mount Technology Association, 2023.<\/li>\n<\/ol>\n
    \n

    Zhejiang Hanchine Al Technology Co., Ltd.<\/a>
    As one of the most professional aoi machines manufacturers and suppliers in China, we are mainly engaged in artificial intelligence and 3D machine vision. Please feel free to wholesale high quality aoi machines at competitive price from our factory. We also accept customized orders.
    Address: 3-806, Lvchuang Plaza, Yuhang District, Hangzhou
    E-mail: alisa.zhang@hanchine.com
    WebSite:     https:\/\/www.hanchine.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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