Test pitch refers to the center-to-center distance between adjacent test points or probes in a test fixture used for testing printed circuit boards (PCBs). It is a critical parameter in designing test fixtures and determining the feasibility of testing densely populated PCBs. Here are some key aspects of test pitch:

1. Definition:

• Test Pitch: The spacing between the centers of two adjacent test probes or test points on a PCB.  



                           2.54mm test pitch for example.

2. Importance:

• Density of PCB Components: As PCBs become more densely populated with smaller components and tighter layouts, the test pitch needs to be smaller to access all necessary test points.

• Fixture Design: A smaller test pitch requires more precise fixture design and manufacturing to ensure accurate probe alignment and reliable contact.

3. Challenges:

• Mechanical Precision: Achieving a small test pitch requires high precision in drilling and fixture manufacturing to avoid misalignment and ensure accurate contact.

• Probe Technology: Specialized probes may be needed to accommodate smaller pitches without compromising the reliability or durability of the testing process.

• Signal Integrity: Close proximity of test points can lead to crosstalk and signal integrity issues, requiring careful design and testing strategies.

4. Common Test Pitch Sizes:

• Standard Pitch: For traditional PCBs, the test pitch is often 2.54 mm (0.1 inches).

• Fine Pitch: For high-density PCBs or IC components, test pitches can be as small as 0.25 mm (0.01 inches) or even less, depending on the technology and precision available.

5. Optimization:

• Design for Testability (DFT): Incorporate DFT principles to ensure that test points are accessible and the test pitch is manageable for the test fixture.

• Advanced Manufacturing Techniques: Utilize advanced manufacturing techniques and high-precision equipment to achieve the necessary test pitch.

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Probe Selection: Choose appropriate probes that can reliably operate at the required pitch without causing damage to the PCB or compromising test accuracy.