Circuit Check performs fixture validation to ensure a high level of quality is achieved. This allows our customer to feel confident the fixtures received from us will meet or exceed the requirements. To achieve this, we have developed several methods to verify the fixture is performing as designed and to the customers specifications.

What does fixture validation consist of?

In-circuit fixture validation ideally consists of the following elements:

• 3070 or TestStation tester checkout (TCO)
  • Tester Checkout is performed on a test base using a sub-set of the test program and the shorts/opens plates to help ensure the wiring was performed correctly and we are seeing the expected results. It does not verify the tester files are correct and will work with manufactured products to detect errors. This is part of the test program debug process either performed by the customer or by a third party.
• Probe target verification (Hits)
  • Probe Target verification or Hits is the process of verifying the probes contact the target within 70% of the target area.
• Clearance verification (Paint Checks)
  • Clearance Verification is the process of verifying there are no fixture components causing damage to the customer supplied manufactured printed circuit assembly.
• Probe compression verification
  • Compression Checks are done to ensure we are seeing the correct compression for the design to prevent damage if too low or intermittent or no contact due to compression being too high.
• Fixture actuation (mechanical verification)
  • Fixture actuation allows us to ensure the fixture is engaging as designed.
• Wire verification
• Finite element analysis (FEA)
  • The theoretical predication of how the device under test will behave.
• Strain gage testing (SGT)
  • The validation of the theoretical predication.

FEA and SGT are a way to determine and verify the forces applied to the product to ensure PCBA damage is prevented.

What is needed for best results?

• Current revision customer supplied device under test.
• Current revision bare board
• Customer supplied CAD or tester check out files for the current revision of the unit to be tested.
• Mechanical sample of the DUT for strain gage testing

What are the potential risks of performing without the above?

If the current revision unit is not provided, it is possible clearance issues, target issues, etc. may occur. One reason may be component differences which do not show up on the CAD provided. An example may be a heatsink attached to an integrated circuit (IC) on the current revision unit but is not on the down revision unit provided. Additionally, the targets for the current revision may not be the same or in the same location as the down revision unit resulting in the inability to verify the probes are hitting the target within 70%.

A bare current revision printed circuit board allows Circuit Check to automate the photograph validation process and the ability to use a target ring if needed to verify the probe is contacting the PCB properly. When no bare board is provided, we are limited to checking a smaller number of targets, usually only taking a small sample from each quadrant.

Customer supplied files are crucial to developing the documentation needed to perform wiring verifications using Circuit Check’s own verifier equipment which includes 100% hits and tester checkout.

In the end the quality of the items provided affects the thoroughness of the fixture validation process. Better quality inputs mean better quality outputs.