Monolithic Voltage Regulator Flip-Chip Package with Interleaved Lead Frame
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Solution Overview
Problem
Conventional packaging solutions for monolithic switching regulators are inefficient due to high resistance and inductance, increased assembly complexity, and thickness, which hinder their performance in low power devices like laptops and cellular phones.
Innovation Solution
A flip-chip package with a single layer lead frame having interleaving lead fingers and different surface patterns for efficient connections, encapsulating a monolithic voltage regulator with bumps, and providing external connectors on the second surface of the lead frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional packaging solutions are used for monolithic switching regulators, then assembly is simpler with traditional structures, but connection resistance and inductance increase, reducing efficiency
Solution Approach 1:
The lead frame is segmented into multiple interleaved layers with distinct functions - some layers provide electrical connections while others provide mechanical support and heat dissipation. This segmentation allows optimization of each layer's purpose, reducing overall connection resistance and inductance while maintaining manufacturability
Solution Approach 2:
The patent transitions from conventional two-dimensional planar packaging to a three-dimensional stacked lead frame structure. Multiple lead frame layers are stacked vertically with interleaved fingers, creating additional connection paths and reducing current density in any single layer, thereby reducing resistance and inductance
2Reliability
If thicker packaging structures are used to reduce connection resistance, then current carrying capacity improves, but package thickness increases, hindering use in low power devices
Solution Approach 1:
The current path is segmented across multiple thin lead frame layers rather than requiring a single thick layer. Each layer carries a portion of the current, and the cumulative effect of multiple parallel paths achieves high current carrying capacity while maintaining thin overall package thickness
Solution Approach 2:
The patent uses composite construction with multiple lead frame materials and configurations stacked together. Different layers may use different metal compositions or thicknesses optimized for specific functions (current carrying, mechanical support, heat dissipation), achieving superior performance in all attributes compared to a single homogeneous structure
3Loss of energy
If multiple wire connections are used between controller, driver, and power devices, then discrete solutions are easier to manufacture, but resistance and inductance between components increase
Solution Approach 1:
The controller, driver, and power device components are merged into a single monolithic integrated circuit. The interleaved lead frame structure provides integrated connection paths for all components within the same package, eliminating the need for multiple separate wire connections and reducing both resistance/inductance and assembly complexity
Solution Approach 2:
The interleaved lead frame acts as an intermediary structure that provides optimized electrical connections between all components. The specific finger interleaving pattern creates low-inductance current paths and reduces resistance, serving as a mediator that enables high-performance connections without requiring complex wire bonding or discrete assembly
Data Source
AI summary
Methods and apparatuses related to packaging a monolithic voltage regulator are disclosed. In one embodiment, an apparatus includes: (i) a monolithic voltage regulator with a transistor arranged as parallel transistor devices; (ii) bumps on the monolithic voltage regulator to form connections to source and drain terminals of the transistor; (iii) a single layer lead frame with a plurality of interleaving lead fingers coupled to the monolithic voltage regulator via the bumps, where the single layer lead frame includes first and second surfaces, where the first surface includes a first pattern to form connections to the bumps, and where the second surface includes a second pattern that is different from the first pattern; and (iv) a flip-chip package encapsulating the monolithic voltage regulator, the bumps, and the single layer lead frame, where the flip-chip package has external connectors of the monolithic voltage regulator at the second surface of the single layer lead frame.