Asymmetric PCB Groove Layout for Edge Warping Control
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Solution Overview
Problem
Asymmetric PCBs experience significant warping, particularly at the edges, due to differences in thermal expansion coefficients of materials used, leading to issues during assembly and affecting product performance.
Innovation Solution
An asymmetric board design with depth control grooves on the second master board, where the grooves increase in depth from the center to the edge, accommodating the greater thermal expansion of the second insulating layer, reducing stress and warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mixed pressing asymmetric laminating structure with PTFE material is used to ensure high signal transmission efficiency, then signal transmission quality is improved, but thermal expansion causes severe warping during soldering process
Solution Approach 1:
The patent applies local quality by creating depth control grooves with varying depths at different locations on the PCB board. The grooves are deeper at edges and lighter at the center, matching the local thermal expansion characteristics of the PTFE material. This localized structural adjustment allows the board to accommodate thermal stress differently across its surface, reducing overall warping while maintaining the high-frequency signal transmission properties of the PTFE layers.
Solution Approach 2:
The patent changes the geometric parameter of the grooves (depth, width, spacing) to control thermal expansion. By adjusting the groove depth from center to edge and modifying their dimensions, the patent creates a structure that compensates for the large thermal expansion coefficient of PTFE. This parameter adjustment allows the board to maintain dimensional stability during the soldering process while preserving the electrical performance of the high-frequency layers.
2Ease of manufacture
If uniform depth grooves are provided in connection area, then manufacturing simplicity is maintained, but edge warping is not sufficiently controlled
Solution Approach 1:
The patent applies asymmetry by designing grooves with non-uniform depths across the PCB board surface. The grooves are intentionally made deeper at the edges and progressively lighter toward the center, creating an asymmetric depth profile. This asymmetric design directly addresses the edge warping problem by providing greater stress relief where it is most needed, while still using standard groove formation techniques that maintain reasonable manufacturing simplicity.
3Shape
If deeper grooves are provided at edges to control warping, then edge flatness is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-designing the asymmetric groove depth pattern before the actual manufacturing process. The groove depth specifications (deeper at edges, lighter at center) are predetermined in the design stage, allowing the manufacturing system to follow a clear guideline. This preliminary planning simplifies the manufacturing process by providing explicit depth control parameters, reducing the need for complex real-time adjustments or multiple processing steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively reduces warping of the edges by providing space for expansion, ensuring flatness and rigidity, thereby improving assembly quality and product performance.
Implementation Method 1
the coefficient of thermal expansion of the PTFE is large... the high-frequency core board itself is prone to warping after thermal compression bonding, further, during assembly, a more serious warping will be caused by thermal stress
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to the technical field of circuit boards, and provides an asymmetric board (4), the asymmetric board (4) includes the first master board (1), the second master board (2), and the insulating dielectric layer sandwiched between the first master board (1) and the second master board (2), and the depth control grooves (50) are disposed in the connection position (31) between the units (41) on the asymmetric board (4), and located on the surface of the second master board (2) and extending a toward the side of the first master board (1), the depth control grooves (50) provide space for the expansion of the second master board (2), reduce the stress of the units (41), and reduce the warping of the second master board (2). When the number of the depth control grooves (50) in the first direction and/or the second direction is greater than 0, the depths of the depth control grooves (50) increase by X from a center to an edge of the asymmetric board (4), and the X is greater than or equal to 0, for example, when the number of depth control grooves (50) in the first direction/second direction of the asymmetric board (4) is less than 3, the depth control grooves (50) are equal, that is the X is equal to 0; when the number of depth control grooves (50) is greater than or equal to 3, the depths of the depth control grooves (50) in each connection position (31) increases sequentially from the center to the edge of the asymmetric board (4), and the depths of the depth control grooves (50) at the edge of the asymmetric board (4) are larger, therefore, the improvement effect on warping is more obvious, and the warping of the edge of the asymmetric board (4) is lower.