Micro laser welding, the picture is a crack?

[RogelioAguirre]

Hi guys,

My name is Rogelio H. Aguirre, a grad student from the University of Waterloo working on MEMS sensors. Currently, I am working with micro laser welding suppliers to fabricate the packaging of a pressure and a temperature sensor. I have some experience on weldings, but not in micro laser one. I am welding a TO Header Substrate made of KOVAR with a Steel case. The device should resist a high pressure of 600 psi; however ,I have some leak issues on the assembly at 300 psi approx. I am not sure if the leak is on the welding line, for me, looks like is in the center of the device. To check this, I check the sample using a microscope with a MPlan APO 20 lens, here is where I need your expertise guys. I am attaching a file with 4 pictures, two are from the microscope, do the images attached shows a fracture on the welding line? According to my knowledge is not a crack, but I want to check with you guys.

Thanks a lot

Rogelio

 

[Baluncore]

The identification of cracks and porous welds can be difficult by image alone.
I think your device is too small for electro-magnetic or ultrasonic crack detection methods.

One method used for small cracks is to apply a dye dissolved in a solvent to the weld. The liquid will travel by capillary action into cracks, then as the solvent evaporates the dye will be precipitated at the edge of the crack. You can then use your microscope to advantage. There are many different dye systems available as “Crack Detection” Kits.

 

[MarkJW]

Just for perspective, about what is the magnification in the images? If it is welded, there are most likely cracks.