Stacked RF Package Interface Using Capacitive Signal Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF package assemblies face challenges with internal mechanical stresses and warpage due to accumulated thickness, which affects package assembly process and reliability, especially in high-frequency applications like 6G, and existing connections introduce extra losses and variation in RF-path and limit path isolation.
Innovation Solution
A stacked RF package assembly with a first substrate and a second substrate, where the interface region includes galvanic connection regions for ground pads and dielectric regions for capacitive coupling of RF signal pads, reducing mechanical stress and signal losses by using capacitive coupling instead of solder connections for RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder connections are used to connect ground pads between substrates, then galvanic connection is achieved, but mechanical stress and warpage increase due to accumulated thickness
Solution Approach 1:
The interface region is segmented into distinct galvanic connection regions and dielectric regions, allowing ground pads to be connected through solder joints while RF signal pads are separated by dielectric material. This segmentation enables selective connection methods for different pad types, reducing overall mechanical stress.
Solution Approach 2:
Dielectric material is introduced as an intermediary between RF signal pads of opposite polarity, replacing direct solder connections. This intermediary prevents galvanic interaction while maintaining electrical isolation, reducing mechanical stress and warpage in the package assembly.
2Reliability
If solder connections are used for RF signal pads, then electrical connection is achieved, but RF signal losses increase
Solution Approach 1:
Dielectric material is positioned between RF signal pads of opposite polarity, acting as an intermediary that enables capacitive coupling without direct metal-to-metal contact. This eliminates solder joint losses while maintaining RF signal transmission through the interface region.
Solution Approach 2:
The mechanical solder connection system is replaced with an electrostatic capacitive coupling system for RF signal transmission. Instead of using metal solder joints to connect RF pads, the patent uses dielectric-separated capacitive coupling, which reduces RF signal losses associated with solder joints.
3Volume of moving object
If substrates are stacked closely to reduce size, then package compactness is improved, but mechanical warpage increases
Solution Approach 1:
The interface region is divided into galvanic connection regions for ground pads and dielectric regions for RF signal pads. This segmentation allows ground connections to provide mechanical support through solder joints while RF regions maintain separation, reducing warpage even in compact stacked configurations.
Solution Approach 2:
Different connection methods are applied locally to different pad types: solder connections are used for ground pads where mechanical strength is needed, while dielectric separation is used for RF signal pads where minimal mechanical stress is required. This local differentiation optimizes both compactness and warpage control.
4Reliability
If dielectric regions are used between RF signal pads, then capacitive coupling is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The dielectric material serves multiple functions simultaneously: it provides electrical isolation between RF signal pads, enables capacitive coupling for RF transmission, and acts as a spacer that defines the interface region geometry. This multi-functionality simplifies manufacturing by consolidating multiple requirements into a single material layer.
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 configuration reduces RF signal losses and mechanical stress, allowing for greater manufacturing tolerance and improved reliability in high-frequency applications by using capacitive coupling between substrates, which also simplifies the assembly process.
Implementation Method 1
the RF package assembly may be configured to capacitively couple an RF signal transmitted between the first substrate and the second substrate via a respective one of the plurality of the first substrate RF signal pads and a respective one of the plurality of the second substrate RF signal pads
Implementation Method 2
a plurality of galvanic connection regions providing a galvanic connection between the plurality of first substrate ground pads and the plurality of second substrate ground pads
Data Source
AI summary
An RF package assembly includes a stacked package-on-package arrangement of a first substrate and a second substrate. Each of the first and second substrates include RF signal pads and ground pads. An interface region between the stacked substrates couples the RF signal pads and ground pads of the first substrate to corresponding pads of the second substrate. The interface region includes galvanic connection regions providing a galvanic connection between the each of the first substrate ground pads and each of the corresponding second substrate ground pads. The interface region includes dielectric regions between each of the first substrate RF signal pads and the corresponding second substrate RF signal pads so that RF signals transmitted between the two substrates are capacitively coupled.