Flip-Chip Power Switch Lead Assembly Parasitic Reduction
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Solution Overview
Problem
Switching regulators with wire bond packaging face issues due to large parasitic inductance and resistance, while flip-chip packaging improves this but requires an efficient lead assembly design to effectively connect flip-chip interconnects to printed circuit boards.
Innovation Solution
A power switch assembly featuring a flip-chip integrated circuit chip with a lead-frame comprising lead sections that extend in parallel, with contact and extended portions, allowing for efficient connection to printed circuit boards, reducing resistance and enhancing current capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wire bond packaging is used for power switch portion, then conventional integrated circuit techniques can be applied, but parasitic inductance and resistance become large
Solution Approach 1:
The patent extracts the power switch portion from conventional wire bond packaging and implements flip-chip packaging instead. The power switch chip is packaged separately with solder bumps directly connecting to the printed circuit board, removing the wire bonds that caused high parasitic inductance and resistance. This extraction allows the power switch to have low parasitic characteristics while the rest of the regulator can use conventional packaging.
Solution Approach 2:
The patent introduces a lead assembly as an intermediary component between the flip-chip power switch and the printed circuit board. The lead assembly includes lead sections with contact portions that receive solder bumps and extended portions that extend laterally to improve current capacity and reduce parasitic inductance. This intermediary structure enables efficient electrical connection while maintaining the benefits of flip-chip packaging.
2Reliability
If flip chip packaging is used for power switch portion, then parasitic inductance and resistance are reduced, but efficient lead assembly design is required to connect flip-chip interconnects to printed circuit board
Solution Approach 1:
The lead assembly is segmented into multiple lead sections, each with a contact portion and an extended portion. The contact portions are arranged to receive solder bumps from the flip-chip power switch, while the extended portions extend laterally to improve current capacity. This segmentation allows each lead section to be optimized for its specific function, simplifying the overall design while maintaining low parasitic characteristics.
Solution Approach 2:
The lead sections extend in the lateral dimension rather than only vertically. The extended portions protrude laterally from the contact portions, creating a three-dimensional structure that improves current capacity by providing additional conductive path area. This dimensional change allows the lead assembly to handle high currents while maintaining compact vertical profile.
Data Source
AI summary
A power switch assembly includes a flip-chip type integrated circuit chip and a lead-frame with a plurality of spaced apart parallel lead sections. The flip-chip type integrated circuit chip includes a distributed transistor, and first and second pluralities of flip-chip interconnects connected to source and drain regions, respectively. The first and second lead sections at least partially overlap along the first axis. Each of the plurality of lead sections includes a contact portion and an extended portion extending laterally from the contact portion. The extended portions of the first and second lead section extend from the contact portion in opposite directions. The first side of the first and second lead section contacts at least two of the first and plurality of flip-chip interconnects, respectively. The second side of the first and second lead are configured to contact a first and second contact area on a printed circuit board, respectively.