IPD Assemblies for RF Amplifier Inductance Reduction
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Solution Overview
Problem
High power, radio frequency (RF) semiconductor devices face challenges in achieving wideband operation due to low frequency resonance limitations caused by bondwire inductances, which restrict instantaneous signal bandwidth (ISBW) and require larger capacitors, leading to increased package size incompatible with industry trends of reducing size and cost.
Innovation Solution
The implementation of integrated passive device (IPD) assemblies in RF amplifiers reduces envelope frequency termination circuit inductance by using photolithographically formed connections, increasing low frequency resonance and ISBW without enlarging the package size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bondwires are used to connect input/output leads to transistors, then electrical connections are established, but inductances increase causing low frequency resonance limitations
Solution Approach 1:
The patent extracts the harmful inductance by removing bondwires from the envelope frequency termination circuit connections. Instead of using bondwires to connect the transistor drain to the termination circuit, the invention uses direct PCB trace connections, thereby taking out the source of excessive inductance while maintaining necessary electrical connections.
Solution Approach 2:
The patent introduces PCB traces as an intermediary connection method between the transistor and the envelope frequency termination circuit. These traces serve as mediators that provide electrical connection with significantly lower inductance compared to bondwires, thus resolving the contradiction between connection reliability and inductance reduction.
2Reliability
If larger capacitors are used in output circuits to compensate for bondwire inductances, then low frequency resonance is improved, but package size increases
Solution Approach 1:
The patent removes the need for oversized capacitors by extracting the harmful inductance source (bondwires) from the circuit. By using direct PCB trace connections instead of bondwires for the envelope frequency termination circuit, the inductance is reduced to acceptable levels, eliminating the requirement for large compensating capacitors and thus maintaining compact package size.
3Ease of manufacture
If conventional packaging methods are used with bondwires, then device assembly is straightforward, but instantaneous signal bandwidth is restricted
Solution Approach 1:
The patent merges the envelope frequency termination circuit directly with the PCB substrate by etching traces directly onto the board. This integration combines the termination circuit with the existing PCB structure, eliminating the need for separate bondwire connections while maintaining manufacturing simplicity and significantly improving instantaneous signal bandwidth through reduced inductance.
Data Source
AI summary
An embodiment of an integrated passive device (IPD) assembly includes a first capacitor formed over a semiconductor substrate, where the first capacitor includes a first capacitor electrode, a second capacitor electrode, and dielectric material that electrically insulates the first capacitor electrode from the second capacitor electrode. The IPD assembly also includes a first contact pad exposed at a top surface of the IPD assembly and electrically coupled to the second capacitor electrode, and a second contact pad exposed at the top surface of the IPD. A second capacitor is coupled to the top surface of the IPD, and includes a first terminal electrically coupled to the first contact pad, and a second terminal electrically coupled to the second contact pad. The IPD assembly may be included in a packaged RF device, forming portions of an output impedance matching circuit and an envelope frequency termination circuit.