Inward Bent Lead IC Package for High Density
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Solution Overview
Problem
Conventional Small Outline Gull Wing IC packages are limited in functional density due to standardized PCB land pattern spacing requirements, necessitating an increase in pin count without increasing board area or manufacturing complexity.
Innovation Solution
A leadframe design featuring gull wing leads alternating with inward bent leads, where the distal end portions are bent towards the package housing, allowing for increased lead density while maintaining the same lead width and pitch, and optionally extending under the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional gull wing leads are used with standardized PCB land pattern spacing, then the package can be manufactured with standard processes, but the lead density is limited and pin count cannot be increased without increasing board area
Solution Approach 1:
The patent applies dimensionality change by transitioning from a conventional gull wing lead configuration to an inward bent lead configuration. The distal end portions of the leads are bent inward toward the package housing, utilizing the vertical and horizontal space more efficiently. This dimensional reconfiguration allows leads to be positioned closer together without increasing the board footprint, thereby increasing lead density while maintaining the same board area.
2Quantity of substance
If the lead pitch is reduced to increase pin count, then more pins can fit in the same area, but PCB manufacturing complexity increases
Solution Approach 1:
The patent changes the geometric parameters of the lead configuration by bending the distal end portions inward. This parameter change allows for increased pin count while maintaining a reasonable lead pitch that does not excessively complicate PCB manufacturing. The inward bend optimizes the spatial arrangement, enabling higher pin density without proportionally reducing the pitch to levels that would significantly increase manufacturing complexity.
3Reliability
If all leads are extended outward as gull wing leads, then self-alignment during soldering is improved, but the lead density is limited
Solution Approach 1:
The patent applies local quality by differentiating the configuration of lead portions. The proximal portions of the leads maintain the gull wing shape that provides self-alignment during soldering, while the distal end portions are bent inward to increase density. This local differentiation allows the lead to simultaneously achieve self-alignment performance where needed and high density where space is constrained.
Data Source
AI summary
A packaged semiconductor device includes a semiconductor die mounted on a leadframe, a housing for the semiconductor die defining a horizontal plane and a horizontal direction. The leadframe includes leads each having an inner lead portion inside the housing and an outer lead portion that includes a first portion that extends out in the horizontal direction from one of the sidewalls of the housing, a transition portion that includes a vertical direction component, and a distal end portion, wherein the distal end portion of the leads are all on the horizontal plane. The outer lead portions alternate between a gull wing lead shape having the distal end portions extending in the horizontal direction outward from the housing and inward extending leads that have their distal end portions extending in the horizontal direction inward toward the housing. The leadframe consists of a single leadframe.