Anode Lead Wire Pre-Treatments for Improving Lead Wire Bonding in Tantalum Capacitor Anodes Processed by De- Oxidation/Sintering.

摘要

De-oxidation processes, in which a highly reactive metal such as magnesium is used to scavenge oxygen, are routinely used in the preparation of tantalum powders for capacitor applications. Reduced oxygen content in the metal powder improves many performance aspects in the finished capacitor. It is also recognized that combining the final anode sintering process with de-oxidation, so called de-oxidation/sintering, is highly advantageous from several performance standpoints. One associated complication is that bonding of the embedded anode lead wire to the anode body is often poor in parts processed by de-oxidation/sintering, leading to several mechanical and electrical issues in the resulting anodes. Several methods for pre-treating the lead wire intended to improve lead wire to anode body bonding have been developed; these methods enable good lead wire bonding during the de-oxidation sintering process. Additional processing steps after sintering, such as laser welding or resistance welding of the lead wire to the anode are rendered unnecessary. Several lead wire pre-treatment processes will be described. The scientific aspects of the process, e.g., the reaction of magnesium with oxygen and the resulting oxygen and magnesium distributions in the tantalum surface layer will be discussed. Potential mechanisms consistent with the observed process improvements will be proposed.