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X-Ray, inspection voltage, voltage blooming

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#71661

X-Ray, inspection voltage, voltage blooming | 31 January, 2014

Hello,

I am trying to estimate hole filling after PiH process using phoenix x|aminer X-Ray Machine. The question is how to select correct inspection voltage?

Inspecting at 60kV 40uA all PiH holes appear to be completely black, that means completely filled. I have tried increasing inspection voltage by 10kV steps. Starting from 90kV PiH holes turn grayish instead of black and small white dots appear. Increasing up to 110kV makes holes even bigger and all other components disappear from the image. White dots become larger.

I cannot really understand what it is. Incorrect inspection voltage (blooming) or real void? Any input would be valuable. Thanks.

Regards, Pavel

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#71662

X-Ray, inspection voltage, voltage blooming | 31 January, 2014

Hi,

to get better image you will probably need higher voltage(depending on how close you want to look). The closer you get the higher the voltage should be. Here are some tips for machine calibration:

1. Make sure your board is on focus. I don't know the what your machine can do, but you should be able to set this parameter based on board thickness(I have some 20mm thick boards and 0.2mm thick boards) 2. Get a scrap board(I would choose a thick one) and solder one barrel half way - then inspect on the x-ray. You should be able to distinguish the difference between the full and the empty half as clear as possible.

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#71670

X-Ray, inspection voltage, voltage blooming | 5 February, 2014

Mr. Evtimov,

Could you please tell me what X-Ray focus is? Machines runs auto-focus routine each time when swithched on showing green/grey/black dots and trying to find centre. What is it for? What is machine searching and how? Thank you.

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#71671

X-Ray, inspection voltage, voltage blooming | 5 February, 2014

What I think it does is to calibrate the camera. You have your tube on the bottom and your camera on the top. For my machine(Dage) I have to put the board I am going to examine inside and select a point on the board surface. THen I just click on this point several times on different angles for the camera(my X-ray is 3D so the camera is moving on different angles). This will allow the machine to figure out the board thickness and follow it on all different angles I turn the camera. It is very important setting as some of the boards are 0.2mm and some are 20mm thick. If your machine is two dimensional you probably will not have exactly the same setting procedure, but I assume difference in thickness will affect the quality of you picture too. So there have to be similar setting(I assume that at least your table is moving in Z axis). You run experiment with very thin and very thick board and see the difference of the quality of your results. About the tube, I prefer to work with high voltage(I never go less than 90 KV, usually 130kV for BGA) and lower wattage. That gives you a very good penetration and clear image.

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