What is Automatic Test Equipment?

Engineers use these tests to verify that components are working as designed, and they use automation to ensure the tests are run quickly and consistently and that the results are evaluated uniformly. An ATE system, sometimes also called an automated test equipment system, can range from a computerized digital multimeter to a multi-instrument assembly that also diagnoses faults. What sets ATE systems apart from standard test systems is the high level of automation used to evaluate the functionality of electronic components.

Semiconductor test engineers refer to the component or components they are testing as the device under test (DUT), equipment under test (EUT), or unit under test (UUT). The electronic manufacturing industry uses ATE systems to evaluate wafers, chips, packages, modules, and boards during the manufacturing process and after fabrication. The goal is to identify problems as early in the process as possible, correct defects when possible, and remove components that do not properly perform the functional operation assigned to them. 

The specific devices used in any given ATE depend on the tested component and the type of test. For example, testing of integrated circuits (ICs) on a silicon wafer uses a probe card attached to electronic measurement equipment that touches down on each microchip before the wafer is cut into individual components. An in-circuit test system looks at the behavior of the components on a printed circuit board (PCB).

Regardless of the configuration, all ATE systems have the following components:

• Control hardware: The brain of an ATE is the control computer and related hardware, usually comprising an industrial computer, power supplies, and high-speed communications cards that connect to the signal sources and test instruments.
• Software: Computer programs automate the entire electronic testing process. Some systems may use proprietary test software languages like LabVIEW, while others use common programming languages like C++, Java, Visual Basic, or Python.
• Handler or prober: A robotic system used to move the DUT to a fixture for testing. For a wafer, the handler moves the wafer under the probe head so it can contact each chip on the wafer.
• Signal sources: A variety of analog and digital devices generate test patterns. The control computer manages waveform generation and signal routing to the test probes. The signal source is often part of the test instrument.
• Test instruments: Computer-controlled test devices, like a digital oscilloscope or digital multimeter, are used to measure the output signal generated by each test pattern.
• Test probes: Both the input and output signals are sent to and measured from probes, usually small pins, that make physical contact with conducting pads on the DUT. 

Automated testing of electronic systems is integral to both design and manufacturing. Design teams use design-for-test (DFT) principles in the product development process to determine which test programs are needed to validate the hardware they are designing. They then specify where the test equipment probes will connect and route circuits to the probe points. They also define the test patterns needed and deliver that information with the circuit layout.

The type of test that test engineers conduct with ATE systems depends on the component type and the assembly complexity, ranging from die-on-wafer to printed circuit board.

Some of the more common test types are:

• Wafer testing: A robotic handler removes a wafer from a cassette and then precisely moves it under a test head so that the probes contact and test each die on the wafer.
• Package testing: Once the integrated circuits are assembled and encased in their package, an ATE system tests the resulting package to ensure that all wire bonds, connectors, solder balls, and other components function properly and no damage occurred during assembly.
• In-circuit test (ICT) and flying probe testing: PCBs are tested after assembly to validate the circuits in the card and ensure that all connections are functioning properly.
• Functional testing (FCT): The most complex type of ATE testing involves powering the device and using the control software to have it execute tests that validate not just the circuits, but the specified behavior of the circuit.
• Burn-in testing: Often the last test before shipping the product, this stress test is usually conducted at maximum power and at an elevated temperature.
• System-level test (SLT): SLT can be performed on many devices in parallel in functional mockup environments, allowing the devices to perform a “normal” functional operation for some period.

ATE tests, regardless of the type of test, usually follow the process below.

• Place: Place the DUT into a test fixture or move the probe head to a die on a wafer.
• Connect: Create an electrical connection with the DUT at multiple locations or connect to the functional interface.
• Execute: Send an electrical signal, called a test pattern, into the DUT.
• Data acquisition: Perform measurements as needed.
• Evaluate: Use diagnostics to review the output for faults.
• Sort: Identify which integrated circuit chips have an issue or tell the handler to move the DUT to the next step, put it into a re-work bin, or fail the DUT.

Companies deploy ATE systems to ensure that the electronic systems they produce function and perform as intended throughout their life cycles. Manual testing is not a feasible approach for semiconductor devices due to their significant complexity and high production volumes.

The most common benefits of a testing regime utilizing ATE systems are:

• High throughput: Multiple ATE systems can be placed in parallel on the assembly line, testing hundreds or even thousands of components at the same time. Likewise, depending on the ATE resource requirements, multiple DUTs can be tested simultaneously. This is sometimes referred to as multi-site testing.
• Increased speed: Automation using robotics and software delivers high-speed testing capabilities at every step of the production process, reducing test time for each component.
• Avoiding human error and repeatability: The consistent, repeatable nature of ATE-based testing effectively removes human error and ensures repeatability of each test, meeting the stringent Six-Sigma quality standards used by the semiconductor industry.
• Logging and analytics: Instead of a simple pass or fail, ATE systems gather data in a way that enables traceability, statistical process control (SPC), and predictive analytics.
• Safety: Some tests require dangerously high voltages or extremely high and low temperatures. Automation removes the need for human exposure to these dangers.
• Cost-effectiveness: Companies make significant upfront investments in designing and deploying ATE systems because that cost is spread out over thousands, and sometimes millions of components. The modular and programmable nature of ATE systems also avoids the high cost of specialized testers. 

Since almost every industry now uses electronics, most industries use some form of ATE systems to validate components. ATE has become essential in industries that require reliability and performance across the product life cycle.

The following industries are the most significant users of ATE systems for their products:

• Semiconductor industry: At the chip level, the semiconductor industry uses ATE systems to reduce testing costs while keeping up throughput. Their primary goal is to sort dies while still in the wafer and to verify that packaged components are working as expected, while maximizing yield.
• Automotive industry: Vehicles continue to incorporate electronics into their systems through an increasing number of electronic devices. These include electronic control units (ECUs), self-driving systems, battery management systems, and a growing number of sensors. Each of these systems must meet stringent safety standards validated through ATE-based testing.
• Aerospace and defense: The electronic systems in aircraft, spacecraft, and weapons systems are mission-critical and must operate in extreme conditions. Electronic systems such as satellite flight hardware, avionics systems, fly-by-wire controls, and many sensors must be tested before they reach the flight stage to meet the industry's stringent safety and reliability standards.
• Telecommunications: The telecommunications industry relies heavily on electronic components to send and receive signals around the world or between a smart watch and a smartphone. Automatic testing in this industry must handle digital and analog circuits as well as broadcast signals.
• Consumer electronics: The massive volume and compressed time-to-market in the consumer electronics industry make ATE system testing a requirement to reduce production costs and lower warranty expenses. 

Engineers use a wide variety of software tools during the design phase to design electronic components, develop and verify test patterns, and design and optimize the test equipment. As the ATE usage has increased, test engineers have discovered that having a single EDA workflow to support testing isn’t just a benefit, it is a requirement for meeting cost, quality, and time-to-market goals.

A strong example of a comprehensive design-for-test solution is the Synopsys TestMAX™ family of products. TestMAX software provides a highly configurable test automation workflow that supports a wide variety of components and aligns tests with physical, timing, and power requirements. The Synopsys TestMAX family includes tools for analog fault simulation, hierarchical automatic test pattern generation (ATPG) compression, logic built-in self-test (BIST), memory self-test and repair, physically aware diagnosis, and testability analysis. Together these capabilities give engineers the power to address the most demanding test challenges in today's rapidly evolving industries.

Engineers also rely on other EDA tools to improve the efficiency and reliability of testing for their components. Design elements such as Synopsys SHS IP software and Synopsys SMS IP software integrate into the circuit design to build in the content needed to test processors and memory.

Many forms of testing require high-speed, high-bandwidth signals sent through PCIe and USB interfaces. Engineers use a package similar to Synopsys SLM High Speed Access & Test (HSAT) with Synopsys TestMAX ALE software to leverage standard interfaces like PCIe and USB to pull test, debug, and monitor data in and out of a chip package, especially system on a chip (SoC) packages, avoiding the need for a large number of interface and test pins. 

In addition, simulation tools like Synopsys PrimeSim software are used to perform virtual testing prior to production. Design teams further apply multiphysics simulation products like Ansys Icepak electronics cooling simulation software, Ansys Sherlock electronics reliability prediction software, and Ansys Mechanical structural finite element analysis software to model the testing environment and ensure that the DUTs are not damaged due to handling, probe-induced mechanical stress, or excessive heating when high-power signals are applied.

Another important factor in building a strong simulation toolset for ATE is integration with widely used ATE platforms, including those from vendors such as Teradyne and Advantest. This type of relationship helps ensure that test content developed during design aligns with tester architectures and can be applied consistently and effectively during manufacturing tests.