Quality Assurance in Electronics Manufacturing with LabVIEW and Data Mining Techniques
Especially in the electronics industry, special testing processes are required to constantly and holistically check the quality standards of the 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 procedures is mainly done with LabVIEW. This allows even small quantities to be tested according to the test requirements.
A test station initially consists of standard devices such as programmable power supplies, remote-controlled measuring devices and calibrators as well as switching matrices and standard IO devices. In addition, there are boundary scan devices. These enable the DUT to be tested using individual remote stations such as resistor loads and function simulators. If such a test hardware cannot be realized with standard devices, it is developed as well as manufactured by SYS TEC electronic from the circuit to the mechanics.
Furthermore, specific test software is required, which is also developed in-house by our engineers. Statistical evaluations and automated key figures can thus be determined precisely and in real time. Quality and efficiency indicators such as failure rate,first pass yield and target/actual time comparisons can be called up at any time. Early detection for the respective maintenance requirement (predictive maintenance) can also be realized at any time.
With these three essential components, SYS TEC electronic has been successfully developing test systems for electronics manufacturing for more than 27 years and also uses them in its own series production. Accordingly, modular test hardware with modular as well as framework-based software is available. Development times are short and the test systems are optimally adapted to the respective products. The modern graphical operator guidance reduces the effort for the personnel to a minimum and decreases the risk for operating errors.
Automated test systems using the example of our electronics production
To ensure continuously high quality, assemblies manufactured at SYS TEC electronic are subjected to a production test. The test of these assemblies (Device Under Test - DUT) is carried out by means of automated test systems, which SYS TEC electronic develops and integrates itself. These test systems are adapted to the respective requirements of the DUT on the basis of a large number of available measuring and testing devices.
The test sequences are controlled and operated by means of LabVIEW. This makes it possible to test even small quantities according to the test requirements. All test results are stored in databases. This enables a machine evaluation of the data, for example to create factory test certificates or to evaluate and specifically control the quality of the production. The DUT is identified by a series of unique serial numbers. The measured and evaluated results of the individual test steps, calibration data, program information and other product-specific information are stored for each DUT. Considering the complexity of modern control devices, a highly automated test sequence becomes indispensable for cost-optimized series production. In the following, the possibilities are shown by means of an example:
The functional test starts with switching on the supply voltage and measuring the current consumption. If the current is outside the permissible tolerance limit, the DUT is switched off immediately to prevent damage due to short circuits. The CPU with the associated memories (Flash, RAM, EEPROM etc.) is tested by means of boundary scan. The programming of the firmware of the DUT is also done via boundary scan.
The DUT has 42 inputs with 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 further be configured as analog inputs for different measurement quantities (0..5V, 0..36V, 0..20mA, resistance measurement 0..1kΩ and 0..2kΩ). These functions are verified in the production test by generating the different voltage sources controllable by a calibrator, A/B encoder simulator and frequency generator as well as connecting them to the input pins of the DUT via a matrix. The control software for the test station simulates the signal generators, switches the signal paths of the matrices and reads out the measured values from the DUT. A target/actual time comparison is used to evaluate the respective function. Analog inputs are tested for compliance with the accuracy requirements by simulation with several measured values from the entire measured value range. The analog inputs are calibrated by calculating the gain and offset parameters for each measurement range and each channel. Component tolerances are thus eliminated and the required high accuracy of the inputs is ensured.
The 28 short-circuit-proof digital outputs can be used either as high-side or low-side outputs and also support PWM (Pulse Width Modulation) and PTO (Periodic Timer Output). These are tested by automatically switching loads on and off. By using software-controlled matrices, it is possible to connect each input or output of the DUT to the associated measurement or test equipment, depending on its function.
The communication interfaces of the DUT (2x CAN, 1x RS422/RS484, 1x RS232) are connected to the PC via appropriate adapters and addressed via the LabVIEW software. Thus, for example, the different modes (RS422, RS485, RS232) can be tested.
The contacting of the DUT with the test station is ensured by a specially made needle bed adapter. At the end of a successful test, the type plate is printed automatically and the factory test certificate is generated.