Sviluppo di un ambiente di collaudo per PCBs = A test system for PCBs

Testability is a fundamental concept to be introduced already in the first phase of a project development, trying to identify a series of guidelines for the layout of a (Printed Circuit Board (PCB). Testing of an electronic board is one of the fundamental points to guarantee quality certification. The migration towards more advanced technology nodes, hence the integration of active and passive components and increasingly miniaturized geometric processes have led to the development of electronic systems able to face the challenges of testing and reliability modeling. My thesis work, carried out in SPEA, leading company in the field of electronic device testing, aimed to analyze the testing of an electronic board to be integrated in a domotic environment. In particular, in a first phase of my project, I had the opportunity to interface directly with the customer to analyze the testing criticisms, and then provide a feasibility analysis concerning the In-circuit and functional test of the device. Even more important it is what dictated the choice of the automatic system to be used. In particular, to carry out the testing of the UUT, a Bed Of Nails system is used, a traditional electronic tester witch uses a mechanical interface between the system and the board to be tested. It is designed to adapt in a flexible way the most different test needs, thanks to the range of models available and to the modular and scalable architecture. A suitable test program has been generated, using a software tool, developed by SPEA, called Leonardo, to perform the test of the board. Circuit analysis enabled to identify circuit nodal impedance, highlighting low impedance connections, available contact points and all the configurations and components of the board with the aim to reduce the debug operations as much as possible. In this phase the In-Circuit Test and the On Board Programming are exploited. The In-Circuit Test (ICT) represents an important part of a production process in which passive and discrete components mounted on the PCB are tested without supplying the necessary power for the complete functioning of the board. Concurrently, due to the presence of EEPROM memory based micro controllers, the On Board Programming can be performed through the use of a proprietary interface (a bidirectional one-wire serial bus system able to update only a set of data where results of ICT Test are memorized). Finally, the complete functionality of the power module is tested during the final inspection. The Board Functional Test (FCT) measures and verifies the electrical characteristics of the board, according to what is specified by the customer and ensures the test of components which could not be tested by the ICT. In particular, I managed the functional test of a voltage-dependent resistor, Varistor, present in the power supply module, a critical component within the circuit under examination. The test was carried out designing the schematic of a conditioning circuit and in a second phase the development of a PCB, of a DC / DC converter capable of delivering 1000V and a maximum power of 6mW. The tests were developed using the C# language, which allowed me to access the machine settings to start the tests and analyze the nonlinear, non-ohmic current–voltage characteristic.