I am working a multinational company as a process engineer. I response for automatic x-ray inspection (AXI). Technology background of AXI is described in this document. The reason of introducing x-ray process is not visible solder connections. I have created detailed explanation of the equipment and x-ray radiation also.
During reforming of the process I have taken care the following aspects: different solder paste, HASL and immersion tin glazes and different product family design. X-ray inspection is not always necessary in case of hidden solder joint, it depends on optical detection rate and process capability. I have observed different aspects because of line installation. The image quality is influenced by heatsink material. Samples which are made with copper heatsink need more power because copper absorps much better the x-ray radiation than aluminium.
When I was optimizing I tried to increase the detection rate. I have reached really good result regarding false calls rate. Based on my experiences I had a lot of ideas how to design new algorithm. These algorithms which are created by another company helped to increase the detection rate of x-ray process. Of course I keep new rules and parameters under observing.
From my point of view AXI has been developed and now it is quite stable. As I already mentioned I have reached very good result with new inspection lists. The introduced ideas are working very well.