Low-Cost In Circuit Test Overview
The Analyst ems Low-Cost In Circuit Test (ICT) System provides the capability to quickly and easily test assemblies for common manufacturing defects such as incorrect, missing or misoriented components, and opens and shorts. These faults comprise the vast majority of problems encountered in the typical manufacturing flow. ICT systems can quickly and accurately measure continuity, capacitors, resistors, inductors, voltages, semiconductor junction voltages, and SMT connections for opens. With these basic tools, ICTs can find most faults in analog or digital assemblies before board power-up.
The CheckSum Analyst ems is designed for testing all types of circuit assemblies. The System combines manufacturing process testing with TestJet Technology to test a single assembly or a panel of multiple assemblies.
The Analyst ems tests the entire unit-under-test (UUT) and individual components without power applied. Using sophisticated measurement techniques such as DC or complex-impedance measurements in conjunction with multi-point guarding, it provides the capability to find the majority of faults such as shorts, opens and wrong or incorrectly installed components. By finding the majority of faults while the UUT is in the safe unpowered mode, and with very specific fault diagnostic messages, faulty UUTs can be repaired quickly.
The Analyst ems is designed to be used for most common through-hole and SMT circuit assemblies. It can perform effective power-down testing for most analog or digital assemblies being manufactured today. The optional power-up functional test capability is ideally suited for lower frequency analog assemblies with some digital content.
Operating the Test System
The standard Analyst ems is provided with a stand-alone long-travel pneumatic fixture press built into a rack-cabinet. This unit can be installed on the factory floor, and is ready for use once connected to standard compressed air and an AC outlet. The standard configuration is complete for most testing operations. It requires only one load/unload cycle per test, with no lids or doors for the operator to manipulate between tests.
CheckSum can ship the system to you complete with a ready-to-use test fixture and test program for one or more UUTs. CheckSum’s fixturing division can provide all of the fixturing and programming requirements; or you can modify or add UUTs yourself or with the use of third-parties.
To configure the system for testing, easily removable, cable-less fixture kits are installed without the need for tools. Fixture change-over takes only a few seconds.
To run a test, the operator places the UUT on the fixture’s guide pins, then presses the start test buttons. Once the test is completed, the system displays the results and the fixture top automatically rises so the UUT can be removed. The system can be configured to automatically produce a test report, or can be setup so that results are saved for statistical analysis (SPC) with included software.
Power-Down Test Capabilities
For component in circuit testing, the System provides effective tools to find most faults. These measurements are made with signal injection/measurement, but without the UUT powered on. Measurements are taken at high speeds using a solid-state multiplexing system. Most complete tests are under ten seconds.
The System can test from each point to each other point to detect faults. Open/short thresholds are typically in the 10W range, but can be programmed over the range of 2W to 50KW. Continuity tests can use either 10mA, 1mA or 100µA source current. Specified pairs of points can be designated as “no-cares” to allow the most effective diagnostics or to deal with points that are near threshold values.
The System provides the ability to measure from 0W up to 19MW using various techniques to optimize the measurement effectiveness. You can choose between using a constant-current source (0.1µA to 10mA), a DC constant-voltage source (.02V to 2V full range), or AC complex-impedance measurements over the range of 100Hz – 1KHz. Resistance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
The System provides the ability to measure from a few pF up to 20,000µF. You can choose between using a constant-current pulsed source (1mA to 10mA), or AC complex-impedance measurements over the range of 100Hz – 100KHz. Capacitance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
The System provides the ability to measure from a few µH up to 1000H. Measurements are made by using complex-impedance measurements with stimulus frequencies between 100Hz and 100KHz and full-range amplitudes of .02V to 2V. Inductance tests can be used with external sense (4-wire Kelvin measurements), and in conjunction with multi-point guarding to isolate individual components. Guard currents up to 100mA are available. Up to 16 distinct measurement and stimulus functions can be active during a single measurement.
For UUTs that have batteries, DC amplitudes up to 10 volts can be measured. Fully differential measurements can be made up to ±8V from chassis ground.
Transistors can be tested as two diode junctions, or tested for Beta while in circuit. The Beta test can help determine proper insertion polarity for transistors that can be installed backwards, but with the base still in the middle. This type of fault cannot typically be detected with diode testing of the junctions.
FETs can be tested for turn-on voltage. By sweeping a voltage into the gate while monitoring the Source/Drain impedance, the FET can be checked for proper orientation and operation.
Opto-isolators can be tested by sourcing into the input leads while measuring the output impedance. By testing each device in the on and off state, high confidence is obtained.
Up to 24V with up to 100mA can be used to actuate relay coils. This allows testing of contacts in each state to ensure that the contacts are not shorted, and that the coil is operational.
Diodes are tested by providing a constant current source (0.1µA to 100mA), then measuring the forward voltage drop, which is typically in the 0.6V to 0.8V range. This test ensures that the diode is installed, is in the proper orientation, and is not open or shorted.
Zeners are tested by providing a constant current source (0.1µA to 100mA), then measuring the forward voltage drop. Measurements up to 50V can be performed. This test ensures that the zener diode is installed, is in the proper orientation, and is not open or shorted. Zeners that cannot be brought to their full voltage due to current or voltage limiting can be tested as normal diodes or in some cases can be tested during the power-up stage.
LEDs are tested like signal diodes, but normally have higher forward voltage drop. Special light-sensing probes can be added to customized test fixtures to detect brightness and color of LEDs and incandescent lamps.
Transformers are typically tested for dc resistance of each coil to detect presence. Coils can also be tested for inductance, and a polarity test can be used to ensure that each coil is wired correctly. This can detect faults inherent to hand-loading of transformers with wire leads.
IC’s are tested by using the ICs test. This test measures each IC pin to specified pins such as VCC, VSS or VDD, checking for the presence of the IC’s internal protection diodes. This test detects most faults such as shorted pins, open pins or mis-clocked or wrong ICs. In some cases, faults may not be detected if the IC pins are bussed or devices of similar pin-topology are interchanged.
IC Pin Connections
With the use of TestJet Technology, the System can detect opens to IC pins, even though the pin is bussed to other ICs. This advanced technology (licensed to CheckSum by Agilent), uses a sophisticated software/hardware algorithm to measure the minute capacitance between the PCB and the IC for each pin. If a pin is open, the capacitance significantly decreases. This technology can be used for most non-power and ground lines on the ICs and on many connectors to ensure proper connection and/or connector presence.
Capacitor Polarity based on TestJet Technology
In some cases, constant-current and voltage measurements of a polarized capacitor can be used to detect incorrect polarity since the capacitor draws additional current as the voltage increases in the incorrect polarity. As a practical matter, this technique cannot be used in many cases during in circuit testing because of voltage or parallel impedance limitations. In this case, the SMT option can be used to detect the polarity of most axial/SMT aluminum and tantalum capacitors up to about 200µF.
Autoprogram and Test
To test UUTs without programming, CheckSum offers the `Autoprogram’ algorithm. This allows you to place a known-good UUT on the test fixture for the System to self-program itself. Other boards can then be tested to find differences that may be indicative of faults. Detected properties include open/shorts, resistance, capacitance and diode junction presence. While this algorithm does not provide the detailed diagnostic messages of a fully-programmed UUT, it can help get boards up on the System quickly for use while programming, or as a complete test on prototype or short runs.
The Analyst ems system includes a power module that can be used to provide higher current outputs from the system. These higher current outputs can be used to actuate UUT relays, power-up low power UUTs, provide additional guard current, or apply stimulus for power-up testing. The module has dual voltage-programmable high current outputs that can be set from +12V to -12V (up to 24V differential). For switching these outputs to the UUT, 16 relay test point outputs are provided. Voltage and current output can be monitored. Fixed switched supplies provide +12V, +5V and -12V at the back panel. These outputs can be switched on or off via on-board relays. The outputs are fused for protection of the system and UUT. Eight additional digital pins can be used for digital input/output or to energize external relays.
PS-UUT-L1 Power Supply
The Analyst ems system includes a programmable power supply that can be used to power-up the UUT for functional test or ISP:
Programmable supply, 0 to 60 Vdc, up to 12.5A, remote sense and output enable.
Voltage Output: 0.05% of Vout + 30mV
Current Output > 50mA to 12.5A: 0.10% of Iout + 25mA
Current Output < 50mA: 0.10% of Iout + 50mA
Additional optional power supplies can be added to the system.
Digital I/O Option
The Analyst ems can be configured with an optional 48 or 96 digital I/O pins. These pins can be relay-connected to the UUT in byte increments. Within each byte, each pin can be set to be an input (tri-state output) or an output. Since each pin has a 10KW pull-up (in conjunction with totem-pole outputs), it is compatible with most logic families. VCC for output can be selected to be +5V or +3.3V.
The Analyst ems can be configured with the optional Boundary-Scan Test. This allows the System to be used with UUTs that have been designed to accommodate boundary-scan, or have on-board devices that support boundary-scan. In addition, boundary scan can be used by some programmable devices to perform in-system programming and program verification.
MultiWriter ISP Device Programming
The Analyst ems can be equipped with the MultiWriter ISP programming and verification capability to simultaneously program up to 384 ISP devices in circuit.
Other System I/O
In addition to the power/stimulus/measurement capabilities already mentioned, the System has a number of other functions available. These include 8 bits of Digital I/O / Relay drivers (PWR-2) and 2 Switched grounds (PWR-2)
System Switching Topology
The Analyst ems offers a flexible switching topology to minimize custom circuitry and to allow assemblies to be easily programmed.
The system uses an N x 16 solid-state analog bus (where N = 200 up to 5,200) that allows each test point to be a measure source high, measure source low, measure sense high, measure sense low, guard source, guard sense, or DC/AC signal source. The solid-state matrix provides high-speed and reliability for power-down testing, or for functional testing of points that do not exceed ±12V referenced to the computer chassis.
A 16 x 2 relay matrix is also included for signals in excess of 10mA, or for voltages greater than ±12Vdc (e.g., Zener measurements).
Digital test points are available at the fixture interface blocks. They can be relay-disconnected during power-down test, then enabled (by byte) during power-up test.
Power outputs are available at the fixture interface blocks. They can be relay disconnected during power-down test. This includes the ground signals so that the UUT is fully floating.
The system comes complete with a comprehensive, yet easy-to-use software package. Running in the Windows environment, users find it to be intuitive and efficient. It is network-compatible and includes comprehensive on-line help. There are several major blocks in the software package:
The system can be setup to accommodate a variety of philosophies about how to present data to the operator.
In the simplest case, the operator places the UUT into the fixture, then uses the Start and Safety switches on the front panel to start the test. The fixture actuates, and the test begins. Once the test is completed, the screen shows a large red FAIL or green PASS indication, and the fixture is de-actuated. Testing status is shown on the CRT, along with red (fail), green (pass) and amber (busy) lights on the stack-light and front panel.
The operator can then choose to ReTest, or move to the next UUT. Most users configure the system to automatically print out a test report of component failures on the system printer if the UUT fails. The operator then attaches the failure report to the bad UUT, and sends it off for repair. The next UUT is then put into the fixture and the process starts over again. This simple operation cycle is easy to use by unskilled operators. Paperless repair is also possible including built-in serial number tracking.
The system can be set up to halt on each failure if you would like the system operators to be able to repeat steps, or repair the UUT as faults occur.
You can also view a real-time Pareto report of failures during each batch of UUTs. By observing this sorted table of specific failures, you can quickly detect repetitive process faults.
Test reports can be automatically generated in a variety of configurations, or can be manually selected by the operator.
Panelized UUTs are accommodated during testing operations. As the test is performed; you can observe a graphical status representation of the panel as each UUT in the panel is tested. At the end of the test, each UUT in the panel is shown as a pass/fail/skip, and result reports are separated by UUT.
While there is a wide variety of capabilities for the operator, you can use the system’s login capability to tailor the resources available to each user. Not only does this provide ease of use based on operator skill level; it can provide integrity to test programs and the system configuration so they cannot be modified by unauthorized personnel.
The system can log serial numbers of assemblies, either through manual entry, or via an optional bar-code reader.
Statistical Process Control
The system can be set up so that it logs statistical data. When this is enabled; you can obtain several types of reports. Reports can be limited by beginning date and time and ending date and time. You can also report on all UUTs, or choose particular ones to analyze.
The Production report lists which UUTs have been tested, the failure rate and how many defects have occurred. This is valuable to determine overall production, production by shift, production by UUT, and production failure rates.
The Pareto report lists the faults sorted by occurrence. For example, you might find that the greatest source of error on one assembly is R101. You might find that frequently the roll of parts used to feed R101 is incorrect, or perhaps the part is difficult to install, or a particular shift is having more trouble than others.
The X-Bar/Sigma reports are used to show, by individual analog measurement, the mean (average), standard deviation, 3-sigma limits, Cp and Cpk. This data is graphically displayed with a predicted distribution curve and high/low test limits.
While this information can be used to monitor process measurements, it is more often used to help fine-tune test program tolerances. By observing the data, even with a relatively small programming sample size, it is practical to set control limits that are applicable to a wider range of UUTs.
Raw statistics data is logged on the disk in ASCII format, comma-delimited, so that you can write custom analysis software if desired.
Test Program Generation
The system includes all the software necessary to write and modify test programs. Many users have CheckSum build test fixtures and write test programs; however, many users do these functions in-house or use local contractors to help in this effort.
Test programs are generated in an interactive spreadsheet-like environment, with each line specifying one test step. Typical test steps include RES (resistance test), CAP (capacitance test), CONTinuity(Shorts/Opens test), JMPx (jump based on some conditional), MEMx (memory math), RELAY (specify relay closure), DIGO (digital output). The line contains other information relevant to the step. For example, a RESistance test step would include two test point names and numbers, a measurement range, nominal (expected) value, and high and low test limits.
The test programming language is rich in features. In addition to normal measurement and stimulus test types, features include mathematics functions, file I/O, jump based on measurements, math, or operator input, display of messages, operator input, interactive adjustment routines, calling of external programs that you have written, and a host of other capabilities to make programming easy and flexible.
Each test program can have up to 30,000 test steps, and test programs can be transparently linked together to provide unlimited length programs, or to allow you to make libraries of program segments that you can reuse.
If you have CAD data for the assemblies, it can be used to generate the preliminary test program and a wiring report. The system accepts ASCII net list and component information from many popular CAD formats including OrCAD, P-Cad, Mentor, HP-BCF, Cadence, Racal-Redac, Viewlogic, Tango, ComputerVision, Pads2000, Scicards, Fabmaster and Accel. Even if you are using another CAD package, it may be able to generate output for one of the supported formats. The automatically generated program contains test steps for the components in the net list, and a wiring report. Once the fixture is built and wired, you can load the generated program, then fine-tune test steps as necessary. Typically, about 70% of the generated steps initially pass. Once the program is interactively optimized with appropriate ranges, polarities and guard points, you can self-learn CONTinuity and ICs data, and the power-down test is ready to use. Functional programming is hand-entered to meet the specific needs of the UUT.
Entry or generation of programs can be done off-line in your office. Optimizing the program is done on the test station and involves choosing the best methods of making measurements. While in the test program editor, you can execute tests. If you are not satisfied with the result, you can enter a menu that displays the measurement taken with a variety of techniques and ranges. You can quickly choose the best technique/range, add guard points, change polarity or add delays to obtain the best test results. Other tools include X-Bar/Sigma, measurement time, and time/voltage displays for each basic measurement type.
Panelization facilities include a step-and-repeat mode. This allows you to specify the panelized format and the initial wiring points for each PCB in the panel. Once you have written and debugged the first UUT in the panel, the system will then automatically generate the steps for the other PCBs. At run-time, the operator can elect to skip PCBs in the panel that are not populated or known-defective.
The station configuration software is used to set up the station’s software and hardware environment.
To manage the system hardware, the station configuration software provides for specification of the hardware configuration in the system and includes a comprehensive self-test facility for each module. The self-test software checks each module for proper operation. In many cases, the system also performs self-calibration of modules against internal standards. This data is then saved to the system disk for future use. If external traceability is necessary in your installation, the system can be checked against an external calibration module (included), and optional functional test electronics can be calibrated against typical external standards using included interactive software.
The login capability can be enabled to allow users to login to the system. This can be used so that reports and internal SPC logs contain the operator name. Optionally, passwords can be assigned for each user. Each user can be assigned privileges, to the level of each individual menu selection in the system.
Reporting capabilities can be configured to meet a wide variety of needs. Test reports can be output on demand, always, or on failure only. The reports can contain all results, or just results for failed steps. The header format, and amount and order of information for each step can be specified, as well as the destination device (e.g., which printer, or to the CRT). Test program reports can also be configured to include or exclude specific data. SPC data-logging can be disabled, or enabled for pass-only steps, pass and fail steps, or just test summary information.
The Analyst ems 12KN includes the 12KN dual-level, long-travel pneumatic fixture press built into a rack-cabinet. This unit can be installed on your factory floor, and is ready for use once connected to standard compressed air and a 220VAC outlet. The standard configuration is complete for most testing operations. It requires only one load/unload cycle per test, with no lids or doors for the operator to manipulate between tests. CheckSum can ship the system to you complete with a ready-to-use test fixture and test program for one or more of your UUTs. You can use CheckSum’s fixturing division to handle all of your fixturing and programming needs; or you can modify or add UUTs yourself or with the use of third-parties.
The optional CheckSum fixture kits; KIT28, KIT20², KIT2KN-QC², or KIT1000-QC² can minimize your recurring costs. The fixtures include handles to make storage and moving easy. Installing the fixture kit simply involves sliding the top and base into place. The bottom assembly includes a fiberglass (G-10 / FR4) probe plate with a fixture interface section and pan covering the wiring.
The top assembly is a clear polycarbonate plate that is used with pressure rods to press the UUT down onto the spring-probes. The top assembly can be machined and milled. The front of the UUT is accessible during test time for adjustment access.
To run a test, the operator places the UUT on the fixture guide pins, then presses the start test button. Once the test is completed, the system displays the results and the fixture top automatically rises so the UUT can be removed.
The Analyst ems 12KN in circuit test system is a complete, ready to use test system and typically includes:
1 System Electronics with Analyst ems software
10 200 Test Point MPX Modules
1 TestJet Technology Module and License
1 Power Module
1 Programmable Power Supply
1 Calibration/Verification Fixture
1 Industrial Chassis with USB system module
1 PC with USB control
1 12KN Dual Level Long-Travel Pneumatic Fixture System
The system includes a swing-arm to mount and position the PC LCD monitor at a comfortable height and angle for the test station operator.
If you need a different configuration feel free to call us and discuss your application.
† MultiWriter Technology is protected under U.S. Patent No. 7,802,021.
* TestJet Technology is protected under U.S. patent numbers 5,124,660 and 5,254,953.