2.5D Interposer RF Packaging Wireless Signal Coupling
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Solution Overview
Problem
Conventional RF device package structures experience high RF loss and electro-static discharge (ESD) due to long bond wires, and thermal stress from mismatched coefficients of thermal expansion (CTE) between device die and package substrates.
Innovation Solution
A 2.5D package structure is introduced, where interposers with passive devices on both sides eliminate the need for bond wires by wirelessly transmitting RF signals through capacitors and transformers, reducing thermal stress by matching CTE with the device die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond wires are used to transmit RF signals between device die and package substrate, then electrical connection is established, but RF loss increases due to long wire length
Solution Approach 1:
The patent extracts and eliminates the bond wire component from the RF signal transmission path. Instead of using bond wires to connect the device die to the package substrate, the invention uses direct flip-chip bonding with solder bumps that provide both mechanical support and electrical connection, thereby removing the source of RF loss while maintaining signal transmission functionality.
Solution Approach 2:
The patent replaces the mechanical bond wire system with an integrated flip-chip bonding system. The solder bumps serve dual purposes as both mechanical anchors and electrical conductors, substituting the separate mechanical (bond wire) and electrical (trace) paths with a unified structure that eliminates RF loss associated with long bond wires.
2Reliability
If bond wires are used to provide DC power and transmit RF signals, then electrical connection is established, but electro-static discharge (ESD) damages occur to RF devices
Solution Approach 1:
The patent extracts the bond wire component that causes ESD damage and replaces it with a flip-chip bonding structure. The solder bumps used in flip-chip bonding have lower inductance and provide better ESD protection compared to bond wires, thereby eliminating the harmful ESD effect while maintaining electrical connection functionality.
3Device complexity
If device die is directly bonded to package substrate, then packaging structure is simplified, but high thermal stress is generated due to CTE mismatch
Solution Approach 1:
The patent introduces an interposer as an intermediary layer between the device die and the package substrate. This interposer has a coefficient of thermal expansion (CTE) that matches the device die, thereby acting as a thermal stress buffer. The interposer absorbs the CTE mismatch stress, preventing it from transferring to the device die while still enabling the simplified flip-chip bonding architecture.
4Ease of operation
If through-package vias are formed in package substrate for RF signal transmission, then signal routing is enabled, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the through-package via structure from the design. Instead of forming complex through-holes and fills in the package substrate, the invention uses the top surface of the package substrate as the RF signal output, allowing direct connection to external antennas or circuitry without requiring through-substrate vias, thereby simplifying manufacturing.
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 solution significantly reduces RF loss, eliminates ESD damage, and lowers production costs by eliminating the need for bond wires and through-interposer vias, while maintaining efficient signal coupling between device die and PCB.
Implementation Method 1
passive devices on opposite sides of the interposer to enable wireless transmission of RF signals
Implementation Method 2
transmitting RF signals wirelessly between the device die and the package substrate through capacitors and transformers
Implementation Method 3
transmitting RF signals wirelessly between the device die and the package substrate through capacitors and transformers
Implementation Method 4
The interposer is made of a silicon-based material having a similar coefficient of thermal expansion to that of the device die
Data Source
AI summary
A device includes an interposer and a radio-frequency (RF) device bonded to a first side of the interposer. The interposer includes a first side and a second side opposite to the first side. The interposer does not have through-interposer vias formed therein. First passive devices are formed on the first side of the interposer and electrically coupled to the RF device. Second passive devices are formed on the second side of the interposer. The first and the second passive devices are configured to transmit signals wirelessly between the first passive devices and the second passive devices.