Micro laser welding, the picture is a crack?

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SUMMARY

Rogelio H. Aguirre, a graduate student at the University of Waterloo, is facing leak issues in a micro laser welded assembly of a TO Header Substrate made of KOVAR and a steel case, designed to withstand 600 psi. Despite his experience with welding, he is uncertain if the leaks are due to cracks in the welding line or elsewhere. Experts suggest using dye penetrant testing for crack detection, as traditional methods may not be suitable for the small scale of the device. The discussion emphasizes the importance of proper inspection techniques in micro laser welding applications.

PREREQUISITES
  • Understanding of micro laser welding techniques
  • Familiarity with KOVAR material properties
  • Knowledge of dye penetrant testing methods
  • Experience with microscopy, specifically using MPlan APO 20 lenses
NEXT STEPS
  • Research dye penetrant testing kits for crack detection
  • Explore advanced microscopy techniques for weld inspection
  • Investigate the properties and applications of KOVAR in sensor packaging
  • Learn about micro laser welding parameters and their impact on joint integrity
USEFUL FOR

This discussion is beneficial for graduate students, materials engineers, and professionals involved in micro welding, particularly those working with MEMS sensors and requiring expertise in weld integrity assessment.

RogelioAguirre
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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
 

Attachments

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

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