Ans：

• The function tester cannot test the specifications of each component so even if the function test is ok, it still cannot ensure the product has no invisible problems. These invisible problems might cause a fatal problem to the quality of the product.
• The function tester is a dynamic test of the PCBA with input power. If there is a malfunction somewhere in the PCB, maybe it can easily cause a chain breakdown, make the unbroken component broken, waste the material and increase the cost of the material and the difficulty of controlling the input of the materials.
• The function tester can only test out which block of electrical circuit is broken down. It cannot tell us which component or exactly where it is broken down. In this opinion, it increases the technical reliability and difficulty when it comes to production trouble shooting.