Embedded DC Blocking Capacitor in Substrate
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Solution Overview
Problem
High-speed serial links face challenges in minimizing board space usage and reducing discontinuities and cross-talk due to the need for additional components like DC blocking capacitors, which can increase the size and cost of PCBs and introduce signal reflections.
Innovation Solution
The method involves positioning DC blocking capacitors within existing openings in the substrate, such as through holes, and surrounding them with non-conductive material to fix their orientation, thereby reducing the need for additional space and components, and minimizing signal path length to enhance high-speed serial link performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC blocking capacitors are placed on the PCB surface, then the electrical connection between semiconductor devices is achieved, but the board space increases and discontinuities are introduced
Solution Approach 1:
The patent merges the DC blocking capacitor with the PCB substrate by embedding the capacitor within the substrate itself, rather than placing it as a separate surface-mounted component. This integration eliminates the need for additional board space while maintaining the electrical connection function, directly resolving the contradiction between connection reliability and board space utilization.
Solution Approach 2:
The capacitor is nested within the PCB substrate structure, with the capacitor positioned inside a cavity formed in the substrate. This nesting approach allows the capacitor to be housed within the existing substrate volume, reducing the overall footprint on the PCB surface while preserving the DC blocking functionality required for reliable electrical connections.
2Reliability
If additional components are added to block DC signals, then voltage imbalance problems are avoided, but the number of vias and bond pads increases
Solution Approach 1:
The patent combines the DC blocking capacitor with the substrate's existing via structure, integrating the capacitor into the via fill material or positioning it within the via cavity. This merging reduces the need for separate bond pads and additional vias, thereby decreasing device complexity while maintaining voltage balance through the capacitor's DC blocking function.
Solution Approach 2:
The substrate structure serves multiple functions: it provides mechanical support, establishes electrical connections through vias, and houses the DC blocking capacitor. By making the substrate multi-functional, the patent eliminates the need for separate dedicated structures for each function, reducing the overall number of vias and bond pads required while maintaining voltage balance.
3Reliability
If DC blocking capacitors are used to isolate DC bias voltages, then signal integrity is improved, but signal reflections and cross-talk increase
Solution Approach 1:
The capacitor is integrated directly into the signal path within the substrate, merging the DC blocking function with the signal transmission path. This integration minimizes the length of signal traces and reduces the number of discrete connection points, thereby maintaining signal integrity through effective DC blocking while minimizing signal reflections and cross-talk that would occur with separate surface-mounted components.
Solution Approach 2:
The patent transitions from a two-dimensional surface-mounted capacitor arrangement to a three-dimensional embedded structure within the substrate. By positioning the capacitor vertically within the substrate thickness rather than on the surface, the signal path length is reduced and the capacitor is closer to the signal traces, improving signal integrity while minimizing the radiative effects that cause cross-talk and reflections.
Data Source
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AI summary
A cavity is formed in a support structure, the support structure being operable to support a semiconductor device, and at least a portion of a circuit element is disposed within the cavity in the support structure. The cavity in the support structure is filled with an electrically non- conductive filling material so as to at least partially surround the circuit element with the non- conductive filling material, and the semiconductor device is electrically connected to the circuit element. In an example embodiment, the circuit element is operable to substantially block direct current that is output by the semiconductor device or another semiconductor device.