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What Is the Use of Test Points in a PCB Circuit?

As a design for test (DFT) approach, test points streamline the PCB testing process. These design elements will enable you to verify your PCB’s function during development. By creating a PCB with test points, you can improve processes that happen in later stages of production.

What Are Test Points on a PCB?

A PCB test point is a small wire loop used for test probes on a PCB that contains surface-mount parts. During production, they enable the user to inject test signals or monitor the board’s circuitry. Test points come in a variety of materials, sizes and colors.

With a test point, you can create an access area for your test probe. Many of these probes have J-hooks designed for older PCB styles that included leads. A PCB test point provides a place for the J-hook or has a sharp pointed end that touches a conductor on the board. Most surface-mount test points feature a phosphor bronze alloy, but they can also have more affordable silver plate coatings.

Advantages of Adding Test Points to Your PCB

Implementing test points in your PCB design will provide the following benefits during development:

  • Low profile: Compared to other test probe connection types, test points offer a much lower profile. Alternatives such as posts and turrets may not fit in a thin enclosure. Test points have a profile similar to that of surface-mounted components, making them a more versatile choice.
  • Time and cost savings: By detecting connectivity issues through test points in early design phases, you can save time and money in later stages. Without early testing, a PCB can demonstrate issues in later design phases that involve more expensive assemblies. Repeated testing of these advanced models results in wasted time and money.
  • Easier error detection: Test points simplify the probe testing process, making it easier to detect potential issues. With test points, you can get the measurements you need without compromising your PCB design.

How to Design a PCB With Test Points in Mind

Proper test point placement includes the consideration of these factors:

  • Board side: In most cases, placing all test points on the same side of the PCB saves time and money by streamlining the testing process.
  • Minimum test point distance: A PCB’s test points should have a minimum of 0.100 inches between them to improve testing effectiveness.
  • Test point distribution: By distributing test points uniformly throughout the PCB, you can more easily test with multiple probes.
  • Zone for tall components: Designating an area of your PCB for tall components can also simplify the testing process. Keeping these parts in one zone will ensure that they do not block access to test points.
  • Manufacturing tolerances: Remember to consider manufacturing tolerances as you create your PCB’s initial layout. The PCB will need room to accommodate test points and probes during the testing phase.

Millennium Circuits Limited — Your PCB Supplier

At MCL, we offer small-scale production and prototype services that can help with the testing process. Learn more about our capabilities by completing a quote request.

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