Software Test Applications for Curve Tracers
The MTForms Software Suite provides full hardware access to RTI’s automated curve tracers and is designed for operators of all skill levels. A simplified forms-based interface requires minimal user experience and provides rapid test setup while advanced users can modify or build their own test configurations from the ground up.
There are 4 test methods a user can configure and run. When properly configured, these methods can accomplish any DC measurement that requires 8 or fewer power supplies in the +/15V, 1A range. The curve tracing methods available to you are dependent on the hardware configuration of the curve tracer.
Standard and custom test setups can be saved in various file formats allowing you to create libraries of pre-configured test settings for later use. Both test sequences and test results can be exported directly from MTForms and DataTrace programs.
Test setup files are paired with test fixture configuration files that visually match each test point to the DUT footprint. The means the test results you see look like the DUT and have friendly names rather than a string of abstract numbers. RTI provides test fixture configuration files with the purchase of an RTI Curve Tracing DUT board.
In most cases, the best way to evaluate the results is to compare it to a result of a known good device. Our software offers numerous ways to save results, recall results and compare results among files. Both MTForms and the new DataTrace programs support comparing 2 or more sets of test results. DataTrace can display nearly unlimited number of files simultaneously to show an average of results where a failure may stand out clearly.
The Four Test Applications
Unpowered Curve Tracing
What it does
The unpowered curve trace method probes the electrical connection behind the physical pins of a device. It can reveal Opens, Shorts and current leakage (OSL) caused by various failure triggers such as EOS, ESD damage, Latch-Up, manufacturing defect and handling induced damage. Pins are curve traced at low voltage and current to prevent additional collateral damage to failed IC structures. Higher power levels are also available when appropriate.
Hardware Configuration Requirement
The unpowered curve trace method minimum requirements are a 2-bus configuration with the MultiTrace. All MultiTrace and Megatrace systems have unpowered curve tracing capability.
When it’s used
The setup forms allow the user to configure the pins grounded, pins curve traced, voltage range, series resistor, number of samples and several other options like autosave, auto-compare, make cosmetic adjustments, and more.
The unpowered curve trace method allows you to independently select pins that will be curve traced and the pins that will be grounded. While any pin can be included, several standard methods make sense:
All pins grounded is the closest to a universal test and does not require detailed knowledge of the device function. All pins are initially grounded and then each pin is curve traced one by one. The method immediately shows any open pins and provides a list of all shorted or leakage pins that can be broken down into subsets in subsequent curve trace tests.
VDD or VSS only grounded allows you to isolate the VDD clamp diode or ground clamp diode during the test and is like what one might see if a hand test method were used. This method requires at a minimum, a list of pin names from the datasheet so that power pins can be identified.
Grounding one shorted pin and curve tracing all others is a quick and easy way to determine which other pins it is shorted to.
Powered Curve Tracing
What it does
Powered curve trace is a powerful method that can be used on any device that can be powered under 15V and 1A. The power pins (up to 4 domains) are initially powered to their nominal operating voltage and then all the Input, Output and I/O pins are curve traced with respect to these supplies. This method requires minimal information about the pin types from the datasheet, but most functional details are not required.
The test yields a curve from each pin in the powered state. The IV curve shows details about the pin protection diode operation, Output pin drive current and Input leakage, VOL/VOH, analog function, and more. The user can determine supply current for any power domain and how that supply current varies as a function of the voltage on the pin being curve traced. This can show switching transients that indicate VIL/VIH. Observe IDDQ and show devices with high or low supply current related defects.
Comparison remains a powerful technique for evaluating failure, but several specs found on the DC specifications table of the datasheet can also be measured and verified. The powered curve trace often shows defects not observable in the unpowered curve trace. Particularly those related to supply current IDDQ, I/O pin direction, Input switching levels, Lower levels of leakage, Output drive transistor damage, internal functional switching (as caused by a pin state).
Powered curve tracing requires a MultiTrace or Megatrace with a 4 or 6-bus configuration. Additional flexibility can be gained from semi-custom setups using jumper wires connected in the fixture.
The 4-bus configuration supports 1 isolated supply or 2 supplies if one is shared with VIH or VIL.
The 6-bus configuration supports 2 isolated or 4 VDD domains if shared with VIL or VIH. When isolated, VIL, VIH, VDD1, VDD2 are completely independent, when shared, the VDD source is also used for VIH.
When it’s used
Test setup requires the user to identify and create groups of pin numbers representing VDD1, VDD2 (if applicable) and ground. Additionally, any input pins that affect the operational state of the device should be attached to VIL or VIH or a bias voltage in order to stabilize the device function and determine the testable state. A simplified test condition just sets all input pins to Logic Low (VIL). Basic information from the datasheet is required but most functional details are not required. The powered curve trace is not a functional test. It is used to evaluate the static DC levels used to bias the device but not necessarily operate.
Supply Current (IDDQ)
What it does
The Supply current method is a simplified version of the powered curve trace and works well for digital or analog devices with bipolar supplies. In general, knowledge of device function and datasheet information is required. In powered curve trace, the user gets a curve describing how IDD changes for every pin tested. In the IDDQ test, the user obtains a single value measurement or a single curve trace relationship by a choice between Single Point and Ramp VDD methods. In the single-point method, all configured VDD domains power up and all inputs are biased to logic low or high (VIL/VIH). In the Ramp VDD test, One VDD is swept along a range while all others are held constant at the configured voltage.
Supply current testing a MultiTrace or Megatrace with a 4 or 6-bus configuration. The 4-bus configuration supports 2 isolated supply or 3 supplies if one is shared with VIH or VIL. The 6-bus configuration supports 3 isolated or 5 VDD domains if shared with VIL or VIH. When isolated, VIL, VIH, VDD1, VDD2, VDD3 are completely independent, when shared, the VDD source is also used for VIH.
When it’s used
The test settings for supply current measurements allows the user to focus directly on a simple supply current parameter. This method is an excellent starting point for Hotspot or Photon Emission mapping techniques used for fault localization when a more static bias is required. While any method can be used with fault localization tools, the supply current test is good for finding damage to components deeper in the core of the device that may only cause high IDD in specific operating states.
Input pins may be biased in any way needed to place the device in a desired operational state. Methods for toggling input pins such as clock or control pins are possible. A user can see in real-time, how the supply current changes when an input pin state is changed
What it does
Latch-up is a specialized test used by reliability engineers to verify if a device can pass the latch-up test and qualify for shipment. It may also be used by Failure Analysis (FA) engineers to verify if a failure mode can happen.
Latch-up supports 2 types of tests: the I-Test and the VDD overvoltage test. The I-Test applies a series of increasing current pulses on the input, output, and I/O pins, each time sensing the supply current at various phases along the way. If the current exceeds the normal current significantly after a pulse is applied, this indicates a failed test. The VDD overvoltage test overpowers the power pins and is returned to normal where IDD is rechecked. In both cases a graphical result is obtained which is converted to a table of values using the included Latch-up report generator.
Latch-up is an extra cost option and not included in the basic version of our software packages. The upgrade unlocks the setup form and enables the report generator. If you have a 4 or 6-bus configuration, no additional hardware is needed.
When it’s used
In a way, latch-up is a high-powered version of the powered curve trace method. More attention is paid to current limits to prevent excessive damage to the device if it does fail. Not all latch-up failures are destructive and the proper setting of current limits, compliance voltage and short pulse time often allow the MultiTrace to not induce Electrical Overstress (EOS) if latch-up is triggered. Additional timing-related settings allow you to fine-tune the pulse duration and control the time periods described in the JESD78 Latch-up specification.
Custom setup is any test configuration not already supported by our software. This includes modifications and additions to MTForms configured test setups and completely from scratch test configurations. Custom setups are possible on all MultiTrace models, but the extent of the test complexity is limited by the number of busses in the configuration.
Some examples of custom tests include Bipolar and FET Transistor characterizations like Family of Curves and Input-Output transfer function with IDD. Custom tests are especially useful in characterizing Analog and Mixed-signal devices where in some cases, functional tests can be derived.
When custom setups are used
Connections, Stimulus, Measurement, Display: users who follow this 4-step recipe can systematically design tests that use up to 100% of the tester capability. The MultiTrace has 8 SMUs, 25 measurement sources, 6 switch matrix channels, and an additional switchable voltage sensing network called the Measure bus. All these resources have options and can be integrated into an automated test capable of making a wide range of measurements. A user can configure a test to make use of the 6-busses to Connect to the device, SMUs then Stimulate those channels with voltage or current sources as required. Measurements of V or I are collected and then Displayed on an X, Y, X graph in a myriad of possible configurations. Additionally, some file handling is required at the beginning and end of the setup process.