High-Frequency Module Substrate Segmentation for Signal Integrity
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Solution Overview
Problem
In high bandwidth circuits, thick cores in substrates distort high-frequency signals and limit the maximal frequency of signals that can be supported, requiring high power compensation circuits and limiting signal reach across line cards.
Innovation Solution
A high-frequency module design that includes multiple die pads, a substrate with a core that does not require conductors to pass through its majority depth, and a heat sink connected to the high-frequency die, with conductors passing through the substrate to couple die pads to line card pads without reaching the core, and a ball grid array between line card pads and conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductors pass through the entire substrate core to connect die pads to line card pads, then electrical connection is achieved, but high frequency signals are distorted and signal quality deteriorates
Solution Approach 1:
The substrate is divided into two separate substrates, each handling a portion of the conductor path. The first substrate contains conductors from die pads to intermediate connection points, while the second substrate contains conductors from intermediate points to line card pads. This segmentation eliminates the need for conductors to traverse the entire core thickness, reducing signal distortion and improving high-frequency signal quality.
2Strength
If the substrate core thickness is increased to one millimeter, then structural support is improved, but conductive via structures become wide and distort high frequency signals
Solution Approach 1:
The thick substrate structure is segmented into two separate substrates, each with its own conductive via structures. This allows each substrate to have optimized, narrower via structures that maintain manufacturing precision and minimize signal distortion, while the combined assembly provides the required structural support equivalent to a one-millimeter core thickness.
3Strength
If conductive paths have high capacitance to support thick substrates, then structural integrity is maintained, but maximal frequency of supported signals is limited
Solution Approach 1:
The conductive path is segmented across two substrates, reducing the capacitance of any single conductive path segment. This segmentation lowers the total capacitance effect on high-frequency signals, enabling support for higher signal frequencies while maintaining structural integrity through the combined substrate assembly.
Solution Approach 2:
Intermediate connection points and structures serve as mediators between the die pads and line card pads. These intermediaries break up the long capacitive path into shorter segments, reducing the overall capacitance effect and enabling higher frequency signal transmission while maintaining structural support.
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
This design efficiently conveys high-frequency signals above 100 gigabits per second without signal distortion, reduces the need for high power compensation, and effectively dissipates heat, enhancing signal reach and performance across line cards.
Implementation Method 1
a heat sink that may be connected to a top surface of the high frequency die and extends outside the aperture
Implementation Method 2
a heat sink that may be thermally coupled to the high frequency die
Data Source
AI summary
A method and a high-frequency module that includes a high frequency die that may include multiple die pads; a substrate that may include a first buildup layer, a second buildup layer and a core that is positioned between the first buildup layer and a second buildup layer; a line card that may include multiple line card pads; and multiple conductors that pass through the substrate without reaching a majority of a depth of the core, and couple the multiple die pads to the multiple line card pads.