Automatic test equipment

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Automatic Test Equipment (ATE) is a general term for measuring equipment that is used by the chip and electronics industry for testing during production. For example, they are tested

ATEs perform the following tests:

  • Marginal testing, for example whether the component reacts in any way when electrical signals are applied, contact test
  • Parameter test: Measurement of parameters such as resistance , capacitance , forward voltage , leakage current , minimum supply voltage, speed versus supply voltage, maximum achievable speed
  • Function test: measuring the complete function of the component (logical operations, writing and reading of memory chips)

construction

The ATE must have a contacting device adapted to the test object ( Device Under Test , DUT ), for example needle cards for wafer tests, sockets for chip and module tests, spring-loaded contact pin adapters or rigid needle adapters for circuit board tests .

The electrical test signals are generated by the test electronics (test pattern generator, pin electronics, signal formatter), fed to the DUT and its response signals are compared in a comparator with the expected signals from a fault-free assembly. If the response signal deviates from the expected signal, the DUT is marked as faulty and rejected.

conditions

Since the performance of the ATE must be superior to the products to be tested, the devices are usually very expensive and make up a relatively high proportion of production costs , up to 30% for very complex components. The trend is therefore towards ever higher parallelism (simultaneous testing of a large number of components) and higher speeds with clock frequencies in the GHz range.

In the case of digital circuits that contain flip-flops and / or RAM memories , the problem arises for the ATE that the internal states cannot be read out or changed directly. Current components of higher complexity ( microcontrollers , PLDs ) etc. have therefore built in separate test circuits, with the help of which the internal states can be monitored and changed via a separate diagnostic interface, the JTAG bus. (See also Boundary Scan Test )

The testing of complex systems such as B. System on a Chip and mixed signal components ( MSIC ) with very different signals (analog, digital) at very high frequencies, is currently the greatest challenge for ATE manufacturers.

In addition, the functions of the ATEs are relocated to the components to be tested as so-called built-in self-test units (BIST). This reduces the costs for ATEs and reduces interference from lines / contacting devices between the ATE and the component to be tested.

See also