PCB Functional Test for Lifeline Systems Telephone and Communicator
"NI technology, the Bloomy Controls test architecture based on NI TestStand, and the user interface have made the difference in accuracy and ease of controlling the test systems."
- Greg Burroughs,
Bloomy Controls Inc.
Replacing an outdated functional test system used to test printed circuit boards for telephones and communicators.
Implementing a functional test system based on LabVIEW and NI TestStand to increase test accuracy and throughput.
DAQ Hardware Updates New Test Systems
On both PCB test systems, the hardware must interface with a Lifeline personality card and device under test (DUT); share the data bus; and control a dual-well, bed-of-nails test fixture. With the dual-well test fixture, an operator can load or remove a DUT from one well without affecting or interrupting the testing of a DUT in the second well. Alternatively, operators can perform tests on only one side of the test fixture.
We chose NI data acquisition (DAQ) boards, cables, and connector blocks to replace the outdated discrete instrumentation used in the previous test systems. Operators use the same hardware in both test systems, with differences only in channel assignments and personality card. The NI PCI-6025E and PCI-6035E multifunction DAQ boards provide the necessary analog inputs, analog outputs, digital I/O, and counters/timers. The analog inputs measure AC and DC signals at various test points. The analog outputs generate DC levels along with telephone system tones and dual tones as varying low-frequency sine waves.
The digital I/O lines switch relays to isolate each test circuit and control the air solenoids in the test fixture. The counters and timers generate square waves of varying frequencies to provide clock pulses to various integrated circuit (IC) chips – a serial EEPROM, a timekeeping chip, and a voice chip – on the DUT and to measure the DUT microprocessor clock frequency. We chose the NI PCI-DIO-32HS digital I/O board because operators can configure it in combinations of inputs, outputs, and wired OR (high impedance) as required for a test. The lines from this board connect to the data bus lines on the DUT and are placed in the high impedance state for most of the tests to avoid bus contention. Some tests require programming and reading data from ICs on the DUT. The DUT clock is disabled, and the PCI-6035E provides the clock while the PCI-DIO-32HS reads from or writes to the IC using software timing during these tests.
NI LabVIEW and NI TestStand Make Data Display User Friendly
Lifeline required the software for both telephone and communicator PCB test systems to provide operator prompts, acquire data, check pass/fail criteria, and report results to a database. The company wanted a standardized, user-friendly user interface to make it easy for operators to learn the new software and operate multiple functional test systems.
We used NI LabVIEW to create the user interface as well as a separate VI for each of the 102 and 66 tests required for the telephone and communicator PCBs, respectively. The test VIs command relays via the digital I/O; generate stimulus through the analog outputs and counter/timers; and acquire data via the analog inputs, digital I/O, and counters/timers. Writing a separate LabVIEW VI for each test facilitates the ability to provide service, eases troubleshooting, and eases rearranging test sequence order in the test executive.
We used NI TestStand to manage the test sequences. To maximize system modularity, the operators grouped tests into individual sequences. Instrument-specific handles, such as DAQ task IDs, are passed as parameters from the main sequence, giving DAQ sessions the ability to remain open throughout the test sequence. Operators can service and debug test sequences individually, making the sequence run faster and more efficiently. Operators used NI TestStand debug features extensively during system qualification. They also used breakpoints and stepping-into-code features to debug, while forcing failures for each test to make sure the sequence properly handled failures.
To start a test, the operator loads a DUT onto the test fixture and selects the well to test. The NI TestStand run-time operator interface then begins to execute a test sequence. LabVIEW pop-ups prompt the operator to make required adjustments to various potentiometers and switches on the DUT when needed.
An image showing component location on the DUT appears in each index of a LabVIEW “Text and Pict Ring” function. One thread in NI TestStand spawns the operator interface and sets the text and pict ring index, while another thread runs the test. NI TestStand closes the text and pict ring operator interface when no longer needed. Most tests do not show a front panel, but a few provide feedback to the operator, such as the meter. We set up key navigation for each of the operator interfaces, so pressing <Enter> proceeds to the next test or pressing <Esc> terminates the sequence. Upon test completion, the operator unloads the DUT.
Using relational database schemas provided in NI TestStand, we built a database to which test results are recorded. We added minor modifications and fields custom to Lifeline’s internal record keeping with little effort. NI TestStand automatically captures pass/fail data and lot quantities so operators can easily calculate yields.
New Systems Improve Test Throughput
Before the new systems were in place, Lifeline and its contract manufacturer each used their own test systems to perform AQL testing and production testing, respectively. Discrepancies occurred between the test systems; in addition, correlating and calibrating were constant issues. Even though the two new systems developed by NI Platinum Alliance Partner Bloomy Controls are installed 3,000 miles apart, it is easy to correlate and qualify them.
“The NI devices and the Bloomy Controls test architecture and user interface have made the difference in accuracy and ease of controlling the test systems,” said Elaine Fasoli Bailey, Lifeline manager of quality assurance and process control. “This has resulted in consistency between tests at Lifeline and its contract manufacturer and great yields at AQL. This has also resulted in less rework for Lifeline Production, ease in updating the system with new tests at Lifeline, and remote updates at the contract manufacturer for engineering.”
The new test systems also have improved Lifeline’s test throughput. Testing time for the telephone PCBs decreased from 4 minutes to 2 minutes 37 seconds per board, a 35 percent throughput increase. Communicator PCB testing time decreased from 3 minutes to 2 minutes 12 seconds per board, a 27 percent throughput increase.
The new, standard operator interface on all of Lifeline’s PCB testers has saved time in training, too. “Once an operator is trained on one test system, retraining is not required to operate another,” Bailey said. “All of our test systems now look and act alike.”
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