What is the tin-lead ratio of hard solder?

The tin-lead ratio of hard solder is commonly set at 60% tin and 40% lead. This specific ratio is well-known in the field of soldering and metallurgy because it provides a balance of properties that are advantageous for many applications. The 60/40 ratio offers good flow characteristics and is suitable for various soldering tasks, particularly in electrical connections where reliability and durability are crucial.

Additionally, the melting point of this alloy is effectively balanced, allowing for ease of use while ensuring a strong joint that can withstand mechanical stress. This balance is what makes this ratio the standard for many types of hard soldering tasks. The other ratios mentioned, while potentially useful in other contexts, do not align with the traditional specification for hard solder, which is why they are not the correct answer.