Abstract
Printed Circuit Boards (PCB) play an important role in the manufacturing of electronic devices. To ensure a correct function of the PCBs a certain amount of solder paste is needed during the placement of components. The aim of the current research is to develop an real-time, closed-loop solution for the analysis of the printing process where solder is printed onto PCBs. Close range photogrammetry allows for determination of the solder volume and a subsequent correction if necessary. Photogrammetry is an image based method for three dimensional reconstruction from two dimensional image data of an object. A precise camera calibration is indispensable for an accurate reconstruction. In our certain application it is not possible to use calibration methods with two dimensional calibration targets. Therefore a special calibration target was developed and manufactured, which allows for single image camera calibration.
Highlights
Printed Circuit Board (PCB) Jet Printing is a new method in Printed Circuit Boards (PCB) manufacturing
Because the image acquisition will be done during the printing process an appropriate measuring system has to be set up within the printer
The smallest solder joints have a diameter of 300μm and have to be imaged with a short working distance
Summary
A jet printer is used to deposit up to 500 tiny droplets of solder paste per second through an ejector mechanism onto the board. The aim of the current project is to develop a built-in, closed-loop analysis of the printing process and a correction of missing solder joints or variations of the solder joint volume This will lead to an increase of the systems efficiency. Using a wide-angle lens leads to large overlapping areas in the images, which can be used for photogrammetric reconstructions of the solder joints. This setup reduces the degrees of freedom of the camera to two and is called the “photogrammetric normal case”, as shown in figure 1. Due to the mentioned restrictions a specific calibration target was designed and manufactured
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