With increasing device complexity, chip functionality and sophistication of circuit board architectures in the electronics industry, testing today’s high density application specific PCBs is extremely challenging. Any application requires several kinds of circuit boards, and each PCB requires testing at various stages, compelling test vendors to develop highly sophisticated automatic test equipment (ATE). The electronics manufacturing industry is witnessing surging demand for ATE to identify defects in electronic assemblies and improve product quality. New testing technologies and this rising demand for complete testing solutions will, therefore, contribute to the growth of the PCB ATE market.
By EB Bureau
Wednesday, May 09, 2012: ATE comprise various apparatus that perform tests on a device, and automatically measure and evaluate the test results. An ATE could be a simple computer controlled digital multimeter, or a complicated system containing dozens of complex test instruments, which can automatically test and diagnose faults in sophisticated electronic packaged parts or silicon wafers, apart from system-on-chips and integrated circuits (ICs).
Earlier, an array of instruments (oscilloscopes, source meters, multimeters, etc) were connected to test devices, parameter by parameter, across temperatures to formulate the results. However, with new technology and evolving design architecture, this is not possible. Hence, this brings ATE into the picture, where the test equipment and its inbuilt system software communicates with the device and testing is automated, ensuring that the parameters in the device datasheet are tested in just few seconds.
Segments that use ATE the most
ATE is widely used in the electronics manufacturing industry to test electronics components and systems after they have been fabricated. ATE is also used for testing avionics and the electronic modules in automobiles. It is also used for testing components in military applications like radar and wireless communication.
ATE can test a wide range of electronic devices and systems—from simple components (resistors, capacitors, and inductors) to ICs, PCBs, and complex assembled electronic systems. ATE systems are designed to reduce the amount of test time needed to verify that a device works properly or to find the faults before the part is used in a finished consumer product. To reduce manufacturing costs and improve yield, semiconductor devices should be tested after being fabricated to prevent defective devices going to the market.
Not a single component can be incorporated into the device without being tested. A lot of parameters have to be taken into account while analysing the performance of the product. Thus, the use of ATE is inevitable in the electronics industry. For instance, ATE in electronic R&D organisations are used for indepth product characterisation and reliability checks. IC or PCBA manufacturing sectors require ATE to check the specifications listed out in the product datasheet, and so on. As there counterfeit ICs available in the market today, quality checks on components using ATE are imperative in any electronic design quality control and screening labs.
Need for ATE
As silicon process improve, more complex products in much smaller package with very high count lead to multilayer PCBs. A PCB might consist of 10-24 layers or even more, making it all the more difficult to test. While earlier chips used to have leads/pins, today, ball grid array (BGA) pins are replacing them on PCBs. In such a scenario, the challenge lies in how to test the chip while it is still on the PCB where there is no access to the test points and also the parameters to be tested are becoming more complex. Also, with the chip soldered onto the PCB, how can one test the board efficiently for better fault coverage? Added to that, modern ICs are more of digital with high pin count and high frequency of operation, making tests difficult. While testing these PCBs, the first challenge is to check whether the components are soldered properly and if there are any faults. Some systems use optical inspection units to scan each board for solder problems including bridges, shorts and poor quality joints. These systems utilise high resolution mobile cameras to detect incorrectly placed and missing components. Some test systems also use 3D X-ray inspection to discover problems that are not visible with standard optical inspection. However, ATE is inevitable when it comes to validating the design and checking the functionality.
Hardware design houses are constantly working on new designs, which need to be validated and tested. For example, today’s cellphones will be outdated in the next two years, as soon as a new design evolves. To test the design and validate this design, ATE systems are required. Similarly, during mass production in a manufacturing unit, there can be manufacturing defects in components. Basic equipment like oscilloscopes and multimeters help in testing the prototype designs. But when it comes to categorising the quality of products flowing out through bulk production, ATE is required.
Boundary scan ATE systems and their benefits
There are a variety of ATE systems available in the market, but currently, functional and boundary scan (BS) ATE systems are fuelling the growth of the PCB ATE markets worldwide. BS ATE, also called BS controllers, are highly versatile and flexible solutions, which have evolved a great deal over the years. One of their outstanding features is the ability to combine with other test methods and technologies to develop synergistic test processes that offer wider test coverage.
As high reliability is crucial for mission critical applications in the defence and medical arenas, BS ATE is being increasingly deployed in these sectors. Emerging trends indicate a preference for combinational testers. The coupling of various techniques, such as functional testing, in-circuit and boundary scan testing offers test coverage that cannot be achieved by individual testing equipment.
Through BS controllers, one can scan every BS compatible IC and every single pin of the IC. Though developing a comprehensive testing programme takes some time, but once developed, multiple ICs can be tested, without removing them from the PCB.
Several important tests can be performed by a BS controller. For example, in hands free operation, it can ‘scan the chain’, which is an infrastructure check of the board followed by a check on the interconnect (between ICs) chain. This helps in figuring out if ICs are soldered properly, if there is any invalid interconnects, verify the netlist. Non BS device functional testing via a BS device is possible. The core logic test helps in checking if the microprocessor is working properly. The memory interconnect test checks whether the memory has been soldered properly on the IC; it also checks the full functionality of the memories, and ensures that the databank is working properly but a slow phase. Finally, cluster testing is done, which involves testing in-circuit variations among various components (the cluster of components is also tested as a functional unit).
Qmax Test Equipment Pvt Ltd, a leading player manufacturing ATE systems for the PCBA and semiconductor industry, offers Qscan QT 900 BS and QT PXI 95 BS test system.Q514416FC a component parametric tester, which is a complete solution developed for IC manufacturers and PCB assembly industries to test analogue, digital and mixed signal ICs and boards.
On February 18, 2012, the EFY Group organised a seminar on ‘Test and Measurement Equipment for Academia: What’s New?’ The event was held on the sidelines of the EFY Expo 2012, and was an initiative aimed at apprising the electronics industry about the latest T&M solutions and technologies. This article is based on the presentation given by Rajiv VK, DGM, technology development, Qmax Test Equipment Pvt Ltd, at this seminar.
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