POL Test Fixtures: Examples from Customer Projects
User Interface
The additively manufactured housing can be customized as desired. In this case, two buttons and a display were to be integrated into the test fixture. This eliminates the need for an additional PC or monitor. If a controller is also installed in the test fixture, it becomes a mobile standalone system, which is particularly convenient if you want to provide the fixture to your manufacturer.
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Exchangeable Insert
The POL test fixture features a fully exchangeable test insert consisting of the carrier plate (moving plate), probe plate (pin plate), connector panel, and base plate. This allows the PCB test fixture to be quickly and flexibly adapted to different PCBs, DUTs, and product variants.
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The Centerpiece
When possible, components on the bottom side of the unit under test are merely recessed in the spring-loaded carrier plate. Tall components may need to be fully recessed. Occasionally, recesses in the CNC-milled probe plate are also required. The probe plate typically contains the locator pins. This ensures a short tolerance chain for positioning the PCB. Any inaccuracies in the 3D-printed components do not affect the positioning accuracy of the PCB relative to the pogo pins, ensuring that even the smallest test points can be contacted reliably.
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Integrated Electronics
It is not only possible to contact both sides, but PCBs can also be placed directly on the opposite side of the probe plate, eliminating the need for wiring and ensuring the shortest possible signal paths. This also allows for pitches well below one millimeter.
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Double-sided contact
An example of double-sided contacting. The upper needle bed is aligned by the same locating pins as the sinker to achieve the highest possible precision. Since the pilot pins are in the CNC-milled needle bed, the tolerance chain is kept low and tolerances of the additively manufactured components have no influence on the accuracy of the test contact pins. The signals are routed downward through a drag chain to the connector panel.
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When rigidity is required
Even 3D printing has its limitations. For very large circuit boards, we therefore reinforce our designs with aluminum strut profiles and increasingly rely on CNC-milled components.
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Test Heights
In many cases different levels are contacted. This is particularly the case when test points on the circuit board and assembled connectors have to be contacted at the same time. Spring contact pins with different lengths can be used for this. In the case of large height differences, however, indentations or elevations can also be provided in the needle bed.
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Any Interfaces
The connector interface is located on the back. You specify which connectors should be installed and their pin assignments. If necessary, you can, of course, handle the wiring yourself.
