The wafer test is a needle test for each die on the wafer. A probe as thin as a hair is made of gold wire on the test head, which is in contact with the pad on the die to test its electrical properties. Characteristics, unqualified dies will be marked, and then when the wafer is cut into independent dies according to the unit of dies, the unqualified dies marked with the marks will be eliminated, and the next process will not be carried out to avoid increase manufacturing cost