Design for Inspection

Time to play

Though Microsoft's Kinect for the Xbox is the first consumer product which uses the fringe detection principle, it was and still is a method commonly used to measure and analyze 3D objects and surfaces. Typical applications include the classification of grinding tools, quality control for engine parts (automotive, aerospace, defense), planarity measurements,  reverse engineering, and - of course - solder paste inspection in the PCB manufacturing process.

Most solder defects on printed circuit boards are caused either by placement errors (wrong part or position) or by errors during the screen printing. For example, too much solder can lead to shorts, too little paste can result in open connections on SMT parts. Having an inspection step right after solder paste printing is a safe and cost-effective way to avoid solder defects, which could still easily be repaired by cleaning and re-printing.

How does Fringe Detection work?

The fringe detection method, or "3D Line scanner" as the industry typically calls it, projects light patterns on the object of interest (solder paste), one or more cameras record the reflections, and software creates a 3D model of the object. The third dimension (height information) is crucial for this application: an AOI system with a regular 2D camera could measure two dimensions (x and y) of the solder paste spot, but without the height (z), no volume calculation would be possible. With a 3D Line Scanner all three values are available and shape, volume, and dimensions can be measured.


In a fully automated assembly line, speed and flexibility is everything, and just like with its AOI and AXI equipment, GOEPEL has designed a highly modular SPI system which is able to achieve an inspection speed of up to 90 sqcm/s.

GOEPEL has introduced "OptiCon SPI-Line 3D", an in-line 3D solder paste inspection system that enables precise three-dimensional solder paste measurement in terms of height, volume, offset, and smearing. The core element is a specifically developed 3D camera head, functionally based on the fringe projection principle and operating without moving parts.  Three system configurations are available, differing in their lateral resolutions of 10 μm, 15 μm, and 20 μm. In high-speed mode, the system achieves an inspection speed of up to 90 cm²/s with extraordinary precision.



Improved Efficiency of in-line THT PCB Inspection

GOEPEL introduces the new OptiCon THT-Line - a dedicated in-line inspection system for the test of large through-hole technology (THT) components.

The system can be utilized in the production process either for manual loading or for inline integration into an accumulation roller conveyor system. During the inspection process PCBs can remain in the production specific carrier. Depending on production organisation, carriers with or without assemblies can be returned in the lower part of the AOI system.


The software package OptiCon PILOT controls test program generation as well as assembly inspection. For efficient use of the system, repair station software, statistical fault evaluation andoffline programming software modules are available. Flexible data interfaces provide the opportunity to communicate with external MES and quality management systems. The OptiCon THT-Line features the latest system software version OptiCon PILOT 5.2. It supports the inspection of THT assemblies by particularly convenient opportunities for test program generation by means of “easyELKO” and “easyOCR”. These functions allow for polarity check of electrolytic capacitors as well as label reading without prior pre-learning process. Compared to already known character recognition methods, this means a revolutionary step in OCR utilization for quality control of electronic assemblies.

Learn more about OptiCon THT-Line and other GOEPEL AOI systems at

Excerpt from the datasheet:


fiat lux

…or “Let there be light” for those who prefer English (or missed the Latin class in school). The heart of an Optical Inspection System is obviously the camera, but without the proper lighting and the resulting reflections even the best camera won’t allow a dependable fault detection. Especially with today’s challenges, like the use of 01005 packages or the switch to lead-free soldering, the good old days of a simple top illumination with white light in combination with a 1 Megapixel camera are definitely over.

GOEPEL electronics with its 15+ years experience in Automated Optical Inspection (AOI) offers “Flexible Spectral Illumination” in all Opticon systems - from bench-top to in-line machines.

The illumination modules in Opticon AOI systems are now able to emit light at any frequency – from infra-red to ultra-violet, freely controllable by the user. But not only the wave length, also the intensity and the direction of the light can be adjusted, allowing the reliable detection of low-contrast components, varying polarity marks, fluctuating material reflections, and impurities. The result is a higher detection reliability of real failures and a lower false-call rate. In order to help the end-user to find the right wave-length and angle, all illumination variants are predefined as presets in Opticon systems, implemented in the standard library and ready to use.

Practical examples:

One very common problem is the detection of low-contrast components, such as SOTs, which reflect light very similar to the PCB background. The image below shows how infra-red light can help to increase the contrast and guarantee a dependable detection of faults.




Fiducial-marks are usually very easy to detect by any AOI system. Sometimes they get tinned , for example when they need to be used by X-ray systems,  and the reflection of the solder can vary dramatically. Ultra-violet light would be the solution and the example below shows the difference.


Visit our website or contact us to learn more about GOEPEL Eletronics AOI solutions.