Automated Test Systems

Electronics production: quality assurance with LabVIEW and data mining techniques

In the electronics industry there is a particularly strong need for special test processes that continuously and holistically review the quality standards of products. To ensure the high quality of the products at SYS TEC electronic, various automated functional tests are carried out throughout the entire production process. The control and operation of the test sequences is primarily done with LabVIEW. This can also be used to check small quantities based on the test requirements.

A test station initially consists broadly of standard devices such as programmable power supplies, remote-controllable measuring instruments and calibrators, switching matrices, and standard IO devices. Boundary scan devices are also used. These enable the device under test (DUT) to be checked using individual counterpoints, such as resistance loads and function simulators. If the test hardware can’t be put together with standard devices, it is instead developed and manufactured by SYS TEC electronic itself, from the circuit to the mechanics.

Furthermore, a specific test software is required, which is also developed in-house by our engineers. Statistical evaluations and automated key figures can thus be determined accurately and in real time. Quality and efficiency indicators such as failure rate, first pass yield and variance comparisons can be accessed at any time. The early detection of maintenance requirements (predictive maintenance) is also possible at any time.

With these three essential components, SYS TEC electronic has been successfully developing test systems for electronics production for more than 27 years, also using them in its own series production. As a result, modular test hardware with modular and framework-based software is available. The development times are short and the test systems are optimally adapted to each product. The modern graphical user interface reduces staff workload to a minimum and lowers the risk of operating errors.

Automated test systems explained using our electronics production as a model case

To ensure consistently high quality, assemblies manufactured by SYS TEC electronic undergo production testing. These assemblies (devices under test – DUT) are tested using automatic test systems, developed and integrated by SYS TEC electronic. These test systems are adapted to the requirements of each DUT using large quantities of available measuring and test equipment.

The control and operation of the test sequences is done with LabVIEW. This also makes it possible to test small quantities based on the test requirements. All test results are saved in databases. This enables machine evaluation of the data, which can be used to create factory test certificates or to evaluate and control the quality of production in a targeted manner, for example. The identification of the DUT is done via a series of unique serial numbers. The measured and evaluated results of the individual test stages, calibration data, programme information and further product-specific information are stored for each DUT. In considering the complexity of modern control devices, a highly automated test procedure for cost-optimised mass production becomes indispensable. In the following, the possibilities are described based on an example:

The functional test is started by switching on the supply voltage and measuring power consumption. If the power current is outside the permissible tolerance limit, the DUT is immediately switched off to prevent damages caused by short circuits. The CPU and its memory (flash, RAM, EEPROM...) is tested using boundary scan. The firmware of the DUT is also programmed via boundary scan.

The DUT has 42 inputs with various different functions. The inputs can be used via software as digital inputs (DI) in sink or source mode, as counter inputs, for pulse width measurement, frequency measurement or as A/B encoder inputs. 16 inputs can then be configured as analogue inputs for various measurement sizes (0..5V, 0..36V, 0..20mA, resistance measurement 0..1kΩ and 0..2kΩ). These functions are verified in the production test by generating the various calibrator-controllable voltage sources, an A/B encoder simulator, and a frequency generator, as well as by connecting them to the input pins of the DUT. The control software for the test station simulates the signal transmitters, switches the signal paths of the matrices and reads the measured values from the DUT. A variance time comparison is used to evaluate the respective function. Analogue inputs are tested via simulation and with several measurement values from the entire measured value range, so as to meet accuracy requirements. The analogue inputs are calibrated by calculating the gain and offset parameters for each measuring range and each channel. Component tolerances are thereby eliminated and the required high accuracy of the inputs ensured.

The 28 short-circuit-proof digital outputs can be used as high-side or low-side outputs and also support PWM (pulse width modulation) and PTO (periodic timer output). These are checked by automated switching on and off of loads. By using software-controlled matrices, it is possible to connect each input or output of the DUT – depending on its function – with the associated measuring or test equipment.

The communication ports of the DUT (2x CAN, 1x RS422/RS484, 1x RS232) are connected to the PC via appropriate adapters and communicated via the LabVIEW software. This means, for example, that the various modes (RS422, RS485, RS232) can be checked.

The DUT is bonded with the test station via a specially made needle-bed adapter. Once a test has been successfully completed, a type plate is automatically printed and an inspection certificate is created.

Further test steps, such as climate tests (burn-in) or In-Circuit-Tests (ICT) are also possible.

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