Design of an automatic test adapter for digital communications testing in automotive applications

Design of an automatic test adapter for digital communications testing in automotive applications. The growing complexity of electronic boards poses major challenges to the industry, which the test engineer faces. Relying on the correct behavior of an electronic board in critical fields, such as automotive, requires a continuous innovation process, through the development of new strategies, special devices and the refinement or adaptation of testing techniques ranging from the simplest to the most sophisticated ones. This thesis has been carried out through a collaboration between Politecnico di Torino and SPEA, global leader in Testing for electronic boards, semiconductors, batteries and MEMS. The project focuses on the design of a test adapter for SPEA 3030-IL Bed of Nails machine, to be deployed in a double configuration system designed specifically for a massive production line. The devices under test are PCBAs for automotive use, which are stepper motor drivers, specifically for the control of the HVAC system. SPEA 3030-IL is a bed-of-nails, multi-core, dual-stage electronic board tester capable of performing both In-Circuit Test (ICT), On-Board Programming (OBP) and Functional Test (FCT) on multiple boards simultaneously. The test adapter acts as an interface between the boards to be tested and the system, achieving a high degree of complexity and containing devices and circuits designed specifically for the application. The project started by studying the customer specifications to determine the kinds of tests needed and the number of boards to be tested at the same time, then choosing which measuring instruments and system resources to use, and designing the wiring diagram of the adapter, focusing on the quality of the applicable measurements. Using the test points on the PCBA, as well as through holes and connectors, the accessibility of the nets for the test was 100%, so each net of the board was used for the tests. This board is characterized by the presence of a microcontroller on it to be programmed and functionally tested, requiring the use of the LIN communication protocol, which is among the most common ones in the automotive field. The communication was handled with special attention to the quality and integrity of the signals, through a process of analysis of the byte sequences transmitted to the board, as well as a careful check of the board's responses for the Functional Test. Writing code for the Functional Test program was part of the project, and it has been implemented using Visual Basic .NET language, with hierarchical object-oriented structure. The debug of the test adapter on a real machine, among the most important parts of the work performed, was a key step for tuning the test parameters and evaluate the reliability of the TPGM. Analyzing the results of the test system made it possible to certify the quality of the work done, achieving a test coverage of 100% of the PCBA components. Several optimizations were carried out to reduce the test time, leading to a final result around 50 seconds, which on the 48 sites results in a time around 1 second per board. By conducting tests on a large number of boards to verify the performance, a First Pass Yield slightly larger than 99% was obtained on the customer line, therefore the installation was completed successfully.