Aluminum to steel braze resistance spot welding

A method of braze resistance spot welding of an aluminum component of an automobile to a galvanized steel component of the automobile, the method comprising:

• providing an aluminum-side electrode having a first tip defining a contact surface with a rounded shape;
• providing a galvanized steel-side electrode having a second tip defining a contact surface with a flat shape;
• and
• providing a control system for:
• depositing a braze filler material between the aluminum and galvanized steel components at a desired location for a spot weld;
• performing a pre-heat including providing a first current across the electrodes for a first period such that the braze filler melts and removes a portion of a zinc coating from the galvanized steel component;
• and
• after performing the pre-heat, performing the spot weld between the aluminum and galvanized steel components by providing a second current across the electrodes for a second period such that the aluminum melts and the galvanized steel does not melt,
• wherein the second current is greater than the first current, and
• wherein the rounded and flat shapes defined by the first and second tips are configured to focus the current density in the aluminum component to facilitate preventing the galvanized steel component from melting.