Technology

How do we achieve our goal of providing the best value in Solder Paste Inspection (SPI) systems? Superior technology. We provide 3D, white light Moiré interferometry quality and repeatability at laser prices. For starters, we have vertically integrated all our component production. From the software, to the image sensor, control electronics and mechanics, everything is designed by VisionMaster to work together seamlessly. We also make our algorithms smarter to compensate for any opto-mechanical and even thermal variations. The end result is a high-performance system at a low price.

Structured Light Scanning

How does structured light scanning work? A known pattern is projected on a surface and observed with a camera. On a flat surface, the projected patten appears undistorted to the camera. On a contoured surface, however, the pattern will follow the height variations on the surface and appear distorted to the camera. The distorted image is compared with the undistorted image and the difference is directly related to the height of the contoured object at every pixel.

Why is structured light scanning superior? Most offline systems use laser-triangulation to obtain 3D board data that only gives a cross-section of the 3D data for each image acquired. In those systems, to acquire a reasonable 3D profile, 30 or more images are acquired by laser scanning, which results in a coarse height profile. However, the height profile generated by structured light scanning has a real height value at every pixel, and typically is constructed with only 3-5 images.

Lasers sound technologically advanced but in reality they are not. The speckle (the dotted structure you seen in any laser source) renders the data noisy, especially on solder balls. Also, red lasers get mostly absorbed by the usually green color of the board FR4 material. The inherent noise and monochromatic color in laser-based Solder Paste Inspection systems makes them less repeatable and less accurate. On the other hand, white light does not suffer from speckle noise and, since it carries the whole spectrum of colors, it is insensitive to board color.

Structured light scanning is an order of magnitude more computationally intensive than a laser triangulation-based system. It not only needs a very accurate pattern projection system, but also advanced software algorithms to compute height at every pixel at high speeds.

Software

Our software uses sophisticated processing techniques and optimizations hidden behind a clean, easy-to-use interface.

The software fully utilizes modern multi-core processors and the massively parallel GPUs that are part of modern PC video cards. Each pixel is pipelined from the source to the last computation in a parallel processing setup. Several images are used to reconstruct height at every pixel. The pre-processing works in real-time as image bitstreams are being received over our Gigabit Ethernet or USB connection.

We use the latest compiler technologies. Additionally, the latest 3D rendering and database technologies are used to enable a fast, smooth and robust user experience.

Imaging

For years we have developed our own cameras and control electronics in order to ensure optimum components. What's new now? They are faster and better. The last generation of our cameras, used in the VM400™ and VM450™ product lines, was USB 2.0-based with a theoretical maximum throughput of 480 Mbps. In reality, USB achieves approximately half that data rate. Our current sensors are Gigabit Ethernet-based and achieve a full data rate of 1000 Mbps. This means higher resolution uncompressed images can be transferred to the PC and 3D height maps are acquired, generated, and displayed faster. The image sensors use CMOS technology for better immunity to the noise and blooming seen in CCD sensor images.