Q: how about the hardness of the 0.4m/m PCB test? What method can measure the activity of gold?

Answer: I wonder if your hardness is surface hardness or circuit board softness? Generally speaking, if it is surface hardness, it can be tested by pencil scratch test. If the board is not what about the hardness standard, especially the hard circuit board, the majority of people still focused on the circuit board flatness is the main consideration, I am afraid for hardness should be changed to strength is proper, because he relates to the assembling operation.
Your face refers to whether the activity of solder? If so, you can do Solderability testing directly, for example, dip balance test or wetting angle test to check the wettability of metal surface. Although circumstantial evidence is available, it can be used as a solderability indicator. Some manufacturers also use solder materials to test the distribution of solder. This test can directly predict the wetting process of welding.
If you are playing gold wire with metal surface, you can directly test the ability to wire, observe the tension is good or bad, you can know. There is no direct method of testing gold surface activity because the so-called activity must also be defined as what is the activity of the object. I hope you will have some answers to your questions above for your reference.