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Soldering a Brass Ferrule and Stainless Steel Wire

2004

Thanks for your anticipated help. I am part of a business that repairs diagnostic medical instrumentation. One of the products that we repair incorporates the use of small stainless steel wires that get bonded to a brass ferrule. This is accomplished by soldering. The current products we use to do this are Indalloy 121 solder consisting of 96.5 Sn /3.5 Ag; Indalloy Flux #2. The two different wires used, depending on the application, are 0.008 and 0.025 in diameter. The procedure in use is to clean the SS wire with acetone [on eBay or Amazon], abrade the wire with sandpaper, dip wire in Flux #2, heat with clean dry soldering iron for 1-3 seconds, rinse wire with water, then reapply flux and tin the wire. The brass ferrule is not prepped in any way. The ferrule measures just about 2mm. The question, does this process look appropriate? Are the right products being used? We do experience some failures of the bonding. The bonded area is subject to significant stress. We want to achieve zero failures of this bonded area. Gold soldered has been suggested due to the potentially stronger bond than silver. Any thoughts?

Thank you,

Chris Nowak
Medical - Philadelphia, Pennsylvania, USA