1. What is a compound fixture? How does it differ from dedicated and universal fixtures? Can it effectively reduce testing costs for circuit board manufacturers? Will it impact the reliability of test results? How is a fixture created? What are its prospects for future development?

2. Traditional circuit board design relies on the assembly of through-hole components, which dictates the pin spacing based on this component type. Historically, the standard lead spacing was segmented into ten parts per inch, equating to approximately one contact per 100 mils. When marking the coordinates on the circuit board, with each grid set at 100 mils, the intersection points on the board’s surface can be identified, referred to as Grid points.

3. If all electronic component contacts are aligned with these grid points, the design is considered On Grid. The fixture used for testing this type of circuit board is known as a Universal fixture. Since the probe holes in the jig are all positioned at fixed grid points, the test fixture can be reused simply by reconfiguring the probes. This characteristic is what gives it the designation of “Universal.” Utilizing this type of fixture can indeed lead to significant cost reductions.


1. However, electronic components are increasingly shifting towards surface mount (SMD) designs.

2. Currently, the contact density in electronic products has significantly improved, particularly with the adoption of array designs for most contact configurations.

3. As a result, the traditionally utilized Universal test fixtures can no longer accommodate this high density of test requirements.

4. This has led to the emergence of double-density and four-density dial tests, with these fixtures still referred to as Universal fixtures.

5. When high-density PCB circuit configurations cannot be tested with Universal fixtures, specialized fixtures must be created to meet specific needs.

6. These specialized fixtures are known as Dedicated Fixtures. While using this type of jig can enhance test density and capabilities, it comes at a considerable production cost, and the design complexity of the test jigs increases.

7. The term composite jig refers to the combination of two different jigs. This approach is the current testing method for most circuit boards, balancing both cost and testing capability.

8. Essentially, these testing methods are still based on contact testing, so reliability should not be an issue.

9. Dedicated fixtures are challenging to manufacture due to the high probe density, and since probes are costly, these fixtures cannot be reused, resulting in significant production costs associated with probes and specialized fixtures.

10. At present, there is considerable research focused on developing non-contact testing methods.

11. However, due to limited adoption and the risk of missed tests, contact testing remains the industry standard for electrical testing.

12. For a small number of diverse products, some companies are also utilizing flying probe testers.

13. High-speed flying probes and non-contact electrical testing methods represent the future direction the industry aims to pursue.