Epoxy Bond Failures to Matte Tin Plate

[edine]

We are having matte tin plated over brass. There parts are subsequently bonded using an epoxy adhesive. This process has been working successfully for years. We are starting production at another location which means a change in plating suppliers. The last lot did not bond at all. Cleaning with isopropyl alcohol did not help, acetone did better, but not good enough. What should I be looking at in the plating process to identify the source of this type of problem? Are there any contaminants that will plate out with the tin that will cause adhesion problems? Thanks.

 

[tomwalz]

Solvents are material specific in what they will dissolve. My first thought would be oils, greases, etc. Use a water break test. Try a caustic cleaner with rinsing agent. Straight caustic is very hard to rinse.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

 

[Compositepro]

One other possibility to consider is that tin and other metals can catalyze many different polymerization reactions. There may be tin salts that may need to be removed or the tin surface may need to be passivated in some way to allow proper bonding.

 

[edine]

This is a new supplier and I am unsure how different the process may be than the incumbant. Prior to this we have always been able to bond well with an alcohol wipe. Wiping with acetone did not help much. Caustic cleaning is out of the question for this plant, but I will check on what the plater is doing. Passivation is a good idea, but since it has worked for years, I'd like to figure out what is different.

Thanks for the help.