At the end of the 1990-year-1990s, a large number of PCB schemes were presented, the additional printed circuit boards were formally applied to the present. For large, high-density PCB assemblies (PCBA, printed circuit board assembly) to develop a robust test strategy is important to ensure compliance with design and functionality. In addition to the establishment and testing of these complex assemblies, the amount of money invested solely in electronic parts may be high — when a unit reaches the final test, it may reach $25,000 billion. Because of this high cost, finding and repairing the assembly problem is now more important than it was in the past or even. Today more complex assembly about 18 square inches, 18 floors; there are more than 2,900 components in the top and bottom surfaces, with 6,000 circuit nodes; there are more than 20,000 weld points to be tested.