Investigating structural properties of solder joints by image processing method

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Dr. Krammer Olivér
Department of Electronics Technology

My task was to design an image processing technology in Matlab which is capable of performing quantitative measurements of Ag3Sn compounds in the intermetallic layer.

In the first part of my thesis, I describe the key steps of reflow soldering technology followed by a description of parameters and characteristics of intermetallic layer and compounds determining the soldering. Then I processed the steps and methods of designing algorithm. Finally I reviewed the different steps and methods of image processing.

In the second part I designed and implemented an algorithm calculating the characteristic parameters of particle structure. These values were calculated for test images first and after the optimization I calculated these for images taken by a scanning electron microscope. I also studied some characteristic parameters of the particles. During designing the algorithm, I was trying to achieve optimum operation by continuously monitoring the running time of the algorithm.

I studied the parameters of the particles (average particle circumference, area, number of particles) and particle structure on test images of three 305 SAC and one 405 SAC solders. It can be seen that each Ag3Sn particle could be quantified. No significant difference was found between the 305 SAC and 405 SAC solders. Their shape is rather elliptic than circular in each case and it is also confirmed by the CI and eccentricity graphs calculated from the different images. The values of characteristic parameters of the particle structure are roughly the same irrespective of the content of the solder.


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