As the PCB used by various electronic equipment becomes more and more sophisticated, detecting the fault of PCB backplane manually is not only complicated but also has low reliability. The AUTOMATIC tester for PCB backplane based on PLD introduced in this paper can improve the working efficiency and ensure the detection reliability.

With the rapid development of electronic technology, is widely used in various types of electronic equipment production of printed circuit board (PCB) increased dramatically, technical personnel need to quickly determine the back on the short circuit, open circuit fault or fixing the excessive amounts of resistance, if rely on artificial detection is very complicated, and the reliability is low, so the circuit board back significantly increased demand of automatic test. In this paper, a method of automatic test system for PCB backplane based on EPM7128 control multiway selector switch ADG732 is proposed, and its implementation is given. It is proved that the test method is fast and effective after applied to PCB backplane test.

System hardware composition

The system structure of automatic tester is shown in Figure 1, which consists of microcomputer, USB bus DIO interface card, PLD control block, multi-way selection switch, test fixture and so on.The system can quickly test open and short circuit faults of single, double and multilayer PCB backboards.

Microcomputers have no special requirements, and can generally use ordinary computers. The system interface adopts cheap USB-7802ADIO industrial control template produced by Hongtop Measurement and Control Technology Co., LTD. The input and output voltage is 0~5V, in line with USB bus +5V standard. Usb-7802a is a 32-channel universal digital TTL level input/output board, with 4 8-bit digital input ports and 4 8-bit digital output latch ports, a total of 32 inputs and 32 outputs; Provides win95/98/2000 /NT under the test program and dynamic link program (DLL).Since it is a USB bus, the USB protocol automatically assigns the base address of the board.