Multirow Gull-Wing Package for Microelectronic Devices
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Solution Overview
Problem
Conventional gull wing packages are limited to a single row of leads, restricting connectivity and incurring high costs due to stringent lead frame requirements for reliability, which are not compatible with multirow configurations.
Innovation Solution
A microelectronic device with a multirow gull-wing chip scale package is developed, featuring intermediate pads without photolithographically-defined structures, connected by wire bonds and encapsulated with a material that extends to these pads, allowing inner and outer gull-wing leads to be attached outside the encapsulation material, reducing costs and enhancing connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gull wing packages use a single row of leads, then the lead frame can meet reliability criteria with suitable surface for wire bonding and adhesion to encapsulation material, but the number of connections is limited for a given package size
Solution Approach 1:
The lead frame is segmented into a carrier portion and multiple separate gull-wing lead portions that are attached to intermediate pads. This segmentation allows multiple rows of leads to be implemented independently, increasing the number of connections while each individual lead portion can be optimized for reliability without requiring complex photolithographically-defined structures on the entire lead frame
Solution Approach 2:
Intermediate pads are introduced as intermediary elements between the die and the gull-wing leads. These pads serve as connection points that allow wire bonds to connect the die to multiple rows of leads without requiring the lead frame itself to have complex photolithographically-defined structures, thus enabling multirow configuration while maintaining reliability
2Reliability
If conventional methods are used to make gull wing packages, then the lead frame can provide reliable connections, but the methods are not compatible with more than one row of leads on each side of the package
Solution Approach 1:
The lead frame structure is divided into a simple carrier portion and multiple separate gull-wing lead portions. This segmentation allows conventional reliable connection methods to be applied to each individual lead portion while enabling multirow configuration that would be incompatible with conventional single-row lead frame methods
Solution Approach 2:
The invention transitions from a single-row configuration to a multirow configuration by utilizing multiple intermediate pads arranged in rows. This dimensional expansion allows multiple rows of leads on each side of the package while maintaining connection reliability through the intermediary pad structure
3Reliability
If photolithographically-defined structures are used on lead frames, then the surface can be made suitable for wire bonding and adhesion, but the fabrication complexity and costs increase
Solution Approach 1:
Intermediate pads serve as intermediary connection points that require photolithographically-defined structures for wire bonding, while the gull-wing lead portions attached to them do not require such complex structures. This intermediary approach concentrates the fabrication complexity only where necessary (at the intermediate pads) rather than across the entire lead frame
Solution Approach 2:
The gull-wing lead portions are designed as simpler, less expensive components that are attached to the intermediate pads. These lead portions do not require expensive photolithographically-defined structures, reducing overall fabrication complexity and costs while maintaining the necessary functionality for reliable connections
Data Source
AI summary
A microelectronic device, in a multirow gull-wing chip scale package, has a die connected to intermediate pads by wire bonds. The intermediate pads are free of photolithographically-defined structures. An encapsulation material at least partially surrounds the die and the wire bonds, and contacts the intermediate pads. Inner gull-wing leads and outer gull-wing leads, located outside of the encapsulation material, are attached to the intermediate pads. The gull-wing leads have external attachment surfaces opposite from the intermediate pads. The external attachment surfaces of the outer gull-wing leads are located outside of the external attachment surfaces of the inner gull-wing leads. The microelectronic device is formed by mounting the die on a carrier, forming the intermediate pads without using a photolithographic process, and forming the wire bonds. The encapsulation material is formed, and the carrier is subsequently removed, exposing the intermediate pads. The gull-wing leads are formed on the intermediate pads.