Before the test environment policy formulation , preparation and understanding is crucial. Parameters that affect the testing strategy include : accessibility. Full access and large manufacturing test pads are always the target for the design of the circuit board . Usually do not provide full access for four reasons :
Board size . Design smaller ; question is " extra" board space test pad. Unfortunately , most of the design engineers believe accessibility welding test printed circuit board (PCB) less important things . Because when you can not use online tester (ICT, in-circuit tester) simple diagnostic product must by design engineers to debug , the situation would be another matter. If you can not provide full access , testing options are limited .
Function. Lost in some high-speed design performance impact plate , but you can gradually reduce the impact on the product testability .
Board size / number of nodes . This is when the physical size of the board have any existing equipment can not be tested . Fortunately, this problem can increase the budget or use external test equipment on the new test facility to be resolved. When the number of nodes is greater than the existing ICT, problem harder to solve . DFT team must understand the test methods that will allow the manufacturing sector with a minimum of time and money to output a good product. Embedded self-test , boundary scan (BS, boundary scan) and function blocks tests can be done . The diagnosis must support unit under test (UUT, unit under test); This test method can only be used by the existing test equipment and capabilities , and fault spectrum manufacturing environment can only be done in-depth understanding .
DFT rule does not comply with or understand. Historically , DFT rules understood by the manufacturing environment , a process engineer or team of engineers and functional test requirements and component technologies enforcement. In a real environment , the process is lengthy , requiring mutual communication design , computer-aided design (CAD) and between tests . The pan- flavored repetitive tasks prone to human error , often due to reach the market in time (time-to-market) pressure while passing by . Now the industry has started using automatic " produce Analyzer ", using DFT rules to evaluate CAD files. When a contract manufacturer (CM, contract manufacturer) to use, can be classified several sets of rules. Continuity and product evaluation error rule is an advantage of this method.