Printed Circuit Board Edge Test Structures for Shielding
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Solution Overview
Problem
Existing test structures for electrical components on printed circuit boards often add bulk and are incompatible with electromagnetic interference shielding, making it difficult to minimize board size while ensuring effective testing and shielding.
Innovation Solution
The implementation of removable test pads and flexible printed circuit configurations, such as embedded flex printed circuits with a rigid portion and a detachable flexible tail, allows for testing without excessive space consumption, followed by dielectric filling to isolate contacts and form a shielding structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional test structures are implemented on printed circuit boards, then testing capability is provided, but board size increases and electromagnetic interference shielding is compromised
Solution Approach 1:
The test structure is divided into separate modular components: test pads, access openings, and removable test plates. This segmentation allows the test functionality to be provided only when needed, enabling the board to maintain a compact size while still offering comprehensive testing capability through the assembly of these modular elements.
Solution Approach 2:
The test plates are designed as removable external structures that can be taken out after testing is complete. This extraction principle allows the board to maintain its minimal size for electromagnetic interference shielding during operation, while providing full test access when required by attaching the external test plates to the access openings.
2Area of stationary object
If test pads are machined away after testing to minimize board size, then board size is reduced, but electromagnetic interference shielding compatibility is lost
Solution Approach 1:
The access openings are pre-formed in the board during manufacturing, and the test pads are pre-positioned on the board. However, the test plates themselves are not permanently attached but are provided as removable components that can be installed when testing is needed. This preliminary preparation allows the board to maintain its compact, shield-compatible design while ensuring test functionality is available when required.
3Area of stationary object
If removable test structures are implemented, then board size is minimized, but testing accessibility is reduced
Solution Approach 1:
The removable test plates serve as intermediary structures that bridge the gap between the compact board design and the need for test accessibility. These plates are attached to the access openings on the board surface, providing extended test interfaces that make electrical components accessible for testing while maintaining the board's minimal size. The intermediary test plates can be easily attached and removed, preserving both compactness and testing ease.
Data Source
AI summary
Electrical components may be soldered to a printed circuit. The printed circuit may have an edge with an opening. Printed circuit contacts in the opening may be configured to form electrical connections with mating contacts on a flexible printed circuit or other external structure. A tester may test the electrical components by conveying signals through the contacts. Following testing, the external structure may be removed from the opening. The opening may then be filled with dielectric to isolate the printed circuit contacts. A printed circuit may have traces that extend under a ground on a surface of the printed circuit, may have edge test points formed from contacts that are cut in half when removing portions of the printed circuit, or may have through-mold vias that are formed through encapsulant over the electrical components.