Effect of brazed joint quality on contact buring/welding

This is a W. A. G , so take it for what it is.

Is this DC or AC current? What voltage? It sounds like the contacts are arcing?

AC current.

Contacts are arcing. Thereare various reasons viz. non planarity of contacts, copper deposition on the Ag-CdO surface, etc.

But assuming that all these reasons are not present, the questions remains the same. Has braze bonding anything to do with this?

I would check the temperature of the contacts during test. If the contacts that burn are operating at higher temperature than the ones that don't, voids in the braze joints may be adding thermal resistance. Also check to make sure that all brazing flux is removed.

There is no flux on the surface.

If you carefully read my questions. I have clearly mentioned that the braze bonding has more than 80 % (some of then have upto 98%) bonding & also my logic (which may be wrong) how brazed joint should fail before the contacts fail.

Think of contact operation as a pulsed heat source to the contact. The majority of this heat is removed by conduction from the contact, through the braze joint, and into the structure. Porosity in the braze joint will act as a thermal insulator retarding the heat flow. Therefore, under the right test conditions, the contact attached with an 80% braze joint will run hotter than one with a 98% braze joint.