Products like general lighting, display panels and signboards also rely on light emitting diodes (LEDs). Those that use multiple units of LEDs in an array require uniformity in the LED’s performance to ensure a smooth and vibrant display. Take a LED array in a display panel for example, each of the LED in the array needs to have the same performance in brightness and intensity as the neighboring ones so that they blend in within the array to deliver a smooth image without any uneven colored spots.
One of the common methods of testing substantial number of LED’s color and intensity uses a camera to capture an image of the lighted LED array and then process the image with software algorithms to evaluate each LED’s measurements. This method uses expensive high-performance cameras to capture high resolution images that allows the software to detect small variations in the intensity or color of LEDs. This is highly effective for testing large display panels that consist of thousands of tiny LEDs like an Organic light emitting diode (OLED) television. However, products like those of an automotive dashboard PCBA with significantly less LEDs may find it a costly choice to adopt.
LED analyzer modules are the alternative for products that use fewer LEDs. LED analyzers use light sensitive modules such as charge-coupled device (CCD) to sense the light source. An analyzer can have multiple of test channels, each consisting of a CCD, to measure every LEDs on the PCBA. Optical fiber channels the light from each LED to their test channels directly. Typically, we install the analyzer modules in the test fixture and connect the optical fibers directly between the test channels and the LED light probe. This means a test fixture’s cost will need to include the cost of a set of LED analyzers, which directly adds to the product’s overall manufacturing cost. To reduce costs, it is possible to install the LED analyzers on the tester instead so that you can use the same set of LED analyzers to support all the test fixtures in production. But moving the analyzers away from the test fixture does mean that we need to have a method to connect the optical fibers between the fixture and the test system.
With the Keysight i7090 automated inline in-circuit test (ICT) system, integrating customize interface connectors is straightforward and does not require modification to the system hardware. Thanks to the multi-functional test interface panel of the i7090, you can design your own connection interfaces and fit the relevant connectors according to your needs.
Figure 1: Keysight i7090 functional test interface supports various interface requirements.
Designed for functional test customization, the standard interface panel on the Keysight i7090 accepts up to 5 functional test fillets with each of them having up to 4 pogo pin blocks of 128 pins each. A fully populated functional test interface with 5 fillets supports up to 2560 pins to connect external devices into the test fixture. Figure 1 shows the functional test interface panel with 1 test fillet installed. Depending on your test requirements, you may add more test fillets and pogo blocks accordingly.
A recent Keysight i7090 benchmarking evaluation in Mexico requires the integration of optical couplers to channel light from 36 LEDs from the test fixture to the Feasa LED analyzers on the system. Designing a custom test fillet let us install two pairs of optical couplers at the functional test interface easily without modifications to the i7090 system. Using optical couplers is more cost effective than having to install LED analyzers on each of the test fixtures. This significantly lowers the cost of our solution to give us an edge at the evaluation.
EQUIP-TEST offers a wide selection optical couplers model to support different channel counts and light probe head styles. It is easy to find one that suits your needs. Figure 2 below shows a model of a 20 channel optical coupler pair from EQUIP-TEST. The Fixture unit has a floating plate design which self-algins to the System unit when both parts come together during fixture lock down. This ensures a perfect connection for every test fixture that performs LED test using the Keysight i7090 system.
Figure2: EQUIP-TEST optical couplers provide connectivity between test fixture and system.
Figure 3 shows the installation of the couplers on the test fillet. Each optic coupler supports up to 20 channels and our custom test fillet can support up to 6 of them. The optical fibers go under the test interface panel and connect to the analyzers at the back of the system. This minimizes the exposure of the fibers and reduces the risk of damaging them during fixture change over or debug.
Figure3: Optical couplers on the i7090 functional test fillet ensure clean and tidy connections.
The integration optical couplers allow us to keep the fixture change over time below 5 secs without needing manual connection and reduce the cost of the test fixture by as much as three thousand dollars. With LED becoming the mainstream lighting device on all lighting products, the demand for fast and cost-effective test solutions is growing. A flexible test system like the Keysight i7090 enables manufacturers to respond swiftly to changing demands and delivers a cost-effective and competitive solution.
Check out the series of posts on test automation with Keysight i7090 using PTEM where you will find many more useful tips on the software and test system.
You are welcome to contact me if you have any questions or comments.
Stay safe and happy.