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Transitioning the routing layer from Layer 1 (Top) to Layer 6 (Bottom), or from Layer 3 to Layer 6 (Bottom), requires careful consideration. This amplifies both the current loop area and electromagnetic field, potentially heightening electromagnetic interference levels. As depicted illustrated in the figure below, the net initially follows a path on Layer 3 1 before transitioning to Layer 6. The combined current loop area (A3 + A4) is significantly larger than surpasses the area A shown in the preceding figure, although an opposite electromagnetic field direction. Consequently, the electromagnetic field strength and the potential for electromagnetic interference are notably increased.
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Adding notably increase.
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The simplest way to mitigate this issue is to relocate the via closer to either the source or the sink. As depicted in the figure below, the via is repositioned near the sink. This adjustment significantly reduces the combined current loop area (A5 + A6), thereby ensuring that the electromagnetic field remains at a lower level.
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If relocating the via is not feasible, mitigating this issue can be achieved by adding a ground via around the signal via can mitigate this issue by providing . This provides a return path for current, thereby maintaining electromagnetic field levels. As depicted in the figure below, the current loop area (A5 A7 + A6) is nearly identical to A8) closely resembles area A in the above previous figure. Additionally, thus ensuring that the electromagnetic field remains at a consistent level.
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the electromagnetic fields of current loops A7 and A8 exhibit opposing directions, leading to partial cancellation of these fields. This cancellation helps mitigate electromagnetic interference.
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1.2.7 Routing on a 4-Layer PCB
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