Cross-hatched Stripline Return Plane for Flexible PCB Bandwidth
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Solution Overview
Problem
Conventional circuit boards with continuous, solid return planes are too rigid to meet flexibility requirements in certain applications, while cross-hatched return planes enhance flexibility but degrade the electrical performance of microstrip and stripline transmission lines.
Innovation Solution
The use of cross-hatch patterned return planes, where the transmission lines are aligned between cross-hatch intersections without overlapping, and the cross-hatch pattern is adjusted in size and shape to restore the performance of microstrip and stripline transmission lines to levels comparable to those with continuous, solid return planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous, solid return planes are used, then electrical performance is maintained, but flexibility is reduced
Solution Approach 1:
The continuous return plane is segmented into a cross-hatched pattern of conductive traces forming grid structures. This segmentation provides flexibility by allowing the plane to bend and flex while maintaining electrical connectivity through the distributed trace network, resolving the contradiction between maintaining electrical performance and achieving flexibility.
Solution Approach 2:
The return plane is implemented as a thin, cross-hatched network of conductive traces that can flex and bend. This thin-film structure with cross-hatching pattern maintains electrical functionality while enabling the circuit board to achieve the required flexibility for conformal and flexible applications.
2Adaptability or versatility
If cross-hatched return planes are used, then flexibility is enhanced, but electrical performance degrades
Solution Approach 1:
The cross-hatched return plane uses varying trace widths, spacing, and patterns in different regions to optimize local electrical characteristics. By adjusting the local density and geometry of the cross-hatch pattern, the design maintains impedance control and signal integrity while providing overall flexibility, thus resolving the degradation of electrical performance.
Solution Approach 2:
The electrical performance of the cross-hatched return plane is optimized by changing parameters such as trace width, trace spacing, grid size, and copper weight. These parameter adjustments allow the cross-hatched structure to maintain controlled impedance and reduce signal loss, counteracting the performance degradation while preserving flexibility benefits.
3Adaptability or versatility
If cross-hatched pattern is introduced, then flexibility increases, but manufacturing complexity increases
Solution Approach 1:
The cross-hatched return plane pattern is designed to be universally applicable across different circuit board types and applications. The same basic cross-hatch geometry and fabrication process can be used for rigid, flexible, and conformal circuits, reducing manufacturing complexity by providing a universal solution rather than requiring different structures for different applications.
Data Source
AI summary
A circuit board transmission line structures has microstrip or stripline transmission line geometries and cross-hatch patterned return planes. The cross-hatch design structure of the return planes and the relative position of the cross-hatch pattern to the transmission lines are configured to increase the usable bandwidth of the transmission lines. By properly adjusting the size and shape of the cross-hatch pattern, the performance of the microstrip and stripline transmission lines can be largely restored to the performance where continuous, solid return planes are used.