Surface mount board-to-board connector is an electrical connector designed to establish connections between two printed circuit boards through surface mount technology. 

Key characteristics of surface mount board-to-board connectors include:

1. Surface Mount Design: These connectors are specifically designed for surface mounting, where they are attached to the surface of the PCB using solder paste and reflow soldering during the assembly process.

2. Compact and Low Profile: SMT board-to-board connectors are known for their compact and low-profile designs, making them suitable for applications where space is limited.

3. Versatility: They are available in various configurations, including right-angle, vertical, and mezzanine connectors, to suit different design and space constraints.

4. Automated Assembly: Surface mount connectors are compatible with automated assembly processes, which is a common practice in modern electronics manufacturing.

5. Secure Electrical and Mechanical Connection: These connectors provide a secure electrical connection between PCBs while maintaining mechanical stability. They are ideal for applications with potential vibration or mechanical stress.

6. Suitable for High-Density Designs: SMT connectors are well-suited for high-density PCB designs, where many connections are required in a limited space.