QFN Package Capacitance Lead for High-Frequency Inductance Reduction
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Solution Overview
Problem
Over-molded leadframe packages, such as quad flat no-lead (QFN) packages, experience significant performance degradation at high frequencies due to inductance issues caused by wirebonds, limiting their use to frequencies below 15 GHz.
Innovation Solution
Incorporating a capacitance lead configured to reduce or offset the inductance created by wirebonds, forming an inductor-capacitor-inductor topology, which allows for the reduction of undesirable inductance and capacitance, enabling QFN packages to operate effectively up to 300 GHz, preferably between 20 GHz and 40 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wirebonding is used to connect the integrated circuit chip to the printed circuit board, then the package can be manufactured with standard processes, but the inductance created by the wirebond degrades performance at high frequencies
Solution Approach 1:
The patent extracts the harmful inductance effect by removing the wirebond inductor from the signal path and replacing it with a direct leadframe connection. The wirebond is eliminated and its function is taken over by the leadframe itself, which has negligible inductance compared to wirebonds.
Solution Approach 2:
The patent changes the inductance parameter by transitioning from a wirebond connection (high inductance) to a leadframe-based connection (low inductance). This parameter change enables high-frequency operation by reducing the inductive reactance in the signal path.
2Productivity
If the QFN package uses traditional wirebond connections, then it can be produced with existing manufacturing processes, but the electrical properties degrade significantly above 15 GHz
Solution Approach 1:
The patent substitutes the mechanical wirebond system with an electrical leadframe-based system. The wirebond mechanical connection is replaced by direct electrical contact through the leadframe, eliminating the mechanical-inductive interface that limited high-frequency performance.
3Ease of manufacture
If wirebonds are used for signal transmission, then standard packaging processes can be employed, but the inductance and impedance mismatches limit the frequency range
Solution Approach 1:
The leadframe serves multiple functions: it provides mechanical support, electrical connection, and signal transmission path. By making the leadframe multi-functional, the patent eliminates the need for separate wirebonds while maintaining manufacturability and expanding frequency capability.
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 enhances the frequency range of QFN packages, allowing them to operate effectively from 5 GHz to 300 GHz, thereby overcoming the limitations of existing QFN packages and enabling high-frequency applications.
Implementation Method 1
a capacitance lead (432) connected to the integrated circuit chip (420) via a wirebond (440) and connected to an input/output (I/O) lead (434) via a wirebond (444)
Data Source
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AI summary
An over-molded leadframe (e.g., a Quad Flat No-lead (QFN) ) package capable of operating at frequencies in the range of about five gigahertz (GHz) to about 300 GHz and a method of making the QFN package are disclosed. The QFN package includes a capacitance lead configured to substantially reduce and/or offset the inductance created by one or more wirebonds used to connect an integrated circuit (IC) chip on the package to an input/output (I/O) lead. The IC chip is connected to the capacitance lead via one or more wirebonds, and the capacitance lead is then connected to the I/O lead via at least a second wirebond. Thus, inductance created by the one or more wirebonds on the package is substantially reduced and/or offset by the capacitance lead prior to a signal being output by the package and/or received by the IC chip. The capacitance lead may form the first plate of a capacitor with the second lead provided on a printed circuit board (PCB) to which the package is mounted.