Test Fixture Maintenance
Explore our detailed fixture maintenance procedure to keep your test fixtures running smoothly.
Introduction to Fixture Maintenance for Forwessun Test Fixtures
Regular fixture maintenance of test fixtures is essential to ensure accurate and efficient testing of PCBs. Proper upkeep extends the life of your fixtures and ensures that all components, from test probes to mechanical parts, function optimally. This page outlines detailed procedures for maintaining Forwessun test fixtures, including cleaning test probes, inspecting mechanical parts, and handling and storing fixtures to prevent damage. By following these guidelines, you can maximise the performance and longevity of your test fixtures, ensuring reliable results. Click below to view relevant sections.
Test Probe Maintenance
Test probes play a vital role in ensuring accurate circuit testing. Test probes are devices used to connect test equipment to the circuit under test, ensuring accurate measurements. They typically have a lifespan of around 50,000 operations, so it’s crucial to monitor the operation counter. This should be checked daily for high-volume testing, while lower-volume testing may require less frequent checks. To learn more about probe maintenance, you can view our dedicated guide on Essential Test Fixture Probe Maintenance.
- Reprobing: Once the probe operation exceeds 50,000 cycles, reprobing is recommended.
- Probe Label Information: All relevant probe sizes and styles are detailed on a label located on the test fixture, and these can be reordered from Forwessun.
- Probe Plotter: A printed probe plotter can be used to help ensure replacement probes are in the correct position and the correct probe types are installed.
- Probe Alignment: Using a smart alignment sheet, check that all test probes are correctly aligned and hitting the centre of the test pads.
Cleaning Probes
Test probes often collect dirt and flux, which can affect their performance. Regular fixture maintenance & cleaning ensures they maintain good electrical contact with the circuit boards. Following these tips will help you keep the probes clean, expand the lift, and keep accuracy high.
- Method: Use a short-bristle, stiff, plastic or nylon brush to lightly brush the probe heads. Be careful not to brush the probes so vigorously that you bend them. Replace any probes that do not clean up with just a light brushing.
- Compressed Air: Non-oiled compressed air cans can also be used to help clear away any loose debris from around the probe field.
- Avoid Solvents: Do not use solvents to clean probes
- The probe mechanism contains lubricant which can be diluted or washed away by solvent. Without this lubricant, probe life will be significantly reduced.
Mechanical Parts Inspection
Mechanical components such as gas stays, handles, and seals need regular inspection to ensure proper functioning. Re-greasing should be done each month using Castrol LM grease or equivalent for lubrication. If the fixture has top probing make sure the bearing pins are greased regularly. Regularly inspecting mechanical parts ensures their longevity and optimal performance.
Please also Take into consideration the following:
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Gas stays should be checked weekly that they are secure and not leaking oil.
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Fixture handles should be periodically checked to ensure they are secure.
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Fixture seals should be checked weekly for any damage or wear.
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Check all tooling pins are fitted and are secure every time a batch of boards is tested.
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TestJet / VTEP plates and amp boards should be checked before each batch of boards is tested.
Pushers / Support Spacers
Pushers and support spacers are components used to hold a PCB in place during testing, ensuring accurate test results.
- Spacers – Make sure that all spacers are firmly attached to the support plate; replace any that are not, or have fallen off.
- A weekly check on all pushers should be done. Check all are the same height and are not bent or worn.
- A Perspex pusher location plate should be used to ensure all pushers are present in the fixture.
- A Perspex top plate spacer location plate should be used ensure all UUT support spacers are present and the correct height.
Fixture Handling and Storage Tips
Improper storage can damage the fixture or contaminate sensitive areas. Following best practices for storage will help prevent unnecessary wear and tear. We suggest to never do the following:
- Don’t store fixtures on painted shelves. The bottom of the fixture will scrape small particles of paint off the shelf which will fall into and contaminate the Testhead’s interface pins.
- Don’t store fixtures on paper, cardboard, or carpet-covered surfaces. These materials could contain corrosive substances that would react with the gold-plated personality or pin-block pins.
- Don’t store fixtures on wooden shelves. Wood splinters can be carried on the bottom of the fixture to the Testhead, which can contaminate Testhead interface pins
Based on our experience, chrome-plated or plastic-coated wire shelves work very well for fixture storage.
FAQs
How often should test probes be reprobbed?
Reprobing is recommended once a probe has exceeded 50,000 cycles, as wear at this stage can affect test accuracy and repeatability.
Where can I find information about the probe sizes and styles used in my fixture?
Each Forwessun fixture includes a probe label listing all relevant probe sizes and styles. These probes can be reordered directly from Forwessun using the information on that label.
How do I ensure replacement probes are installed in the correct positions?
A printed probe plotter can be used to verify probe locations and confirm that the correct probe types are installed during maintenance or replacement.
How can I check that probes are correctly aligned with the test pads?
Use a smart alignment sheet to confirm that all probes are centred on their corresponding test pads. Misalignment can lead to false failures or inconsistent readings.
Can compressed air be used during fixture maintenance?
Yes, non‑oiled compressed air cans are suitable for clearing loose debris from the probe field. Avoid oiled air sources, as they can contaminate probes and reduce conductivity.
