RFIC Wire-Bond Pad Plating and Signal Path Redesign
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Solution Overview
Problem
The increasing cost of gold in nickel/gold (Ni/Au) surface plating for Radio Frequency (RF) integrated circuits (ICs) has led to higher packaging costs, and existing technologies face challenges in reducing signal losses associated with high RF sheet resistance materials like Ni/Pd/Au used in wire-bond areas.
Innovation Solution
The configuration of an electronic circuit module with an on-die passive component, where the passive device is placed in the RF upper signal path to avoid passing the RF current through high RF loss bonding pads, and the use of Ni/Pd/Au or similar high RF loss plating materials is minimized by re-routing the signal path to reduce signal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni/Au surface plating is used for wire-bond pads, then electrical connection quality is improved, but packaging cost increases due to rising gold prices
Solution Approach 1:
The patent replaces expensive Ni/Au plating with alternative materials such as Ni/Pd/Au or other cost-effective plating options that provide sufficient electrical connection quality without the high cost of traditional Ni/Au plating, thereby reducing packaging costs while maintaining acceptable connection reliability
Solution Approach 2:
The patent modifies the plating material composition and thickness parameters to optimize the balance between electrical connection quality and cost, using alternative material compositions that achieve adequate performance at lower cost
2Reliability
If Ni/Pd/Au plating material is used in wire-bond areas, then electrical connection is achieved, but RF signal losses increase due to high RF sheet resistance
Solution Approach 1:
The patent extracts the high RF loss plating materials from the RF signal path by implementing separate bonding pads specifically for RF signals that bypass the Ni/Pd/Au plating layers, thereby eliminating the source of RF signal losses while maintaining electrical connection functionality
Solution Approach 2:
The patent segments the bonding pad structure into distinct RF signal paths and power/ground paths, with RF signal paths using low-loss materials or direct substrate connections while other paths can use the Ni/Pd/Au plating for electrical connection, thus isolating the RF signal from high-loss materials
3Reliability
If bonding pads are placed in the RF signal path, then electrical connection is established, but RF signal losses occur due to high RF sheet resistance of plating materials
Solution Approach 1:
The patent introduces an intermediary low-loss transmission path for RF signals that mediates between the RF signal source and destination, using materials or structures with lower RF sheet resistance to carry the signal while allowing bonding pads to exist in non-critical areas for electrical connection purposes
Data Source
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AI summary
To reduce the radio frequency (RF) losses associated with high RF loss plating, such as, for example, Nickel/Palladium/Gold (Ni/Pd/Au) plating, the solder mask can be reconfigured to prevent the edges and sidewalls of the wire-bond areas from being plated in some embodiments. Leaving the edges and sidewalls of the wire-bond areas free from high RF loss plating, such as Ni/Pd/Au plating, provides a path for the RF current to flow around the high resistivity material, which reduces the RF signal loss associated with the high resistivity plating material. Also, to reduce the RF losses associated with high RF loss plating, such as, for example, Ni/Pd/Au plating, an on-die passive device, such as a capacitor, resistor, or inductor, associated with a radio frequency integrated circuit (RFIC) can be placed in an RF upper signal path with respect to the RF signal output of the RFIC. By placing the on-die passive device in the RF upper signal path, the RF current does not directly pass through the high RF loss plating material of the passive device bonding pad.