Lead Frame Package Structure for Stress-Resistant Solder Bonding
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Solution Overview
Problem
Conventional semiconductor packages face reliability issues due to poor bonding between the package and solder materials, as well as stress-induced failures, particularly in high-density chip-scale packages.
Innovation Solution
The proposed electronic package structure includes a substrate with a lead frame configured to have protrusions and conductive bumps, which improve board-level reliability by laterally engaging conductive connective structures and providing stable points of contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional package structures are used, then manufacturing is simpler, but reliability is poor due to poor bonding and stress-induced failures
Solution Approach 1:
The patent applies preliminary action by forming protrusions on the lead frame before attaching the semiconductor die. These protrusions are pre-configured to engage with solder balls, ensuring reliable bonding is established in advance rather than relying on conventional flat lead surfaces that bond poorly under stress.
Solution Approach 2:
The lead frame is segmented into multiple protrusions distributed across its surface, each providing an independent bonding point. This segmentation allows stress to be distributed across multiple engagement points rather than concentrated at single bonding locations, improving overall bonding reliability.
2Productivity
If high density interconnects are used in small footprint packages, then productivity increases, but reliability deteriorates due to stress-induced failures
Solution Approach 1:
The patent transitions from conventional two-dimensional planar bonding to three-dimensional engagement by forming protrusions that extend vertically from the lead frame surface. This dimensional change allows solder balls to engage with the protrusions, creating a mechanically interlocked connection that resists stress better than flat surface bonding while maintaining high interconnect density.
Solution Approach 2:
The protrusions create localized regions of enhanced mechanical engagement at specific bonding points. Each protrusion provides concentrated structural support and stress distribution at its location, allowing the package to maintain high interconnect density while each local bonding point independently resists stress.
3Reliability
If conventional lead frame configuration is used, then device complexity is lower, but stress distribution is poor leading to reliability issues
Solution Approach 1:
The lead frame configuration is segmented into multiple protrusions that distribute stress across numerous discrete engagement points. Each protrusion acts as an independent stress distribution element, preventing stress concentration that would occur with conventional flat lead surfaces or single bonding points.
Data Source
AI summary
A method for providing an electronic package structure includes providing a substrate having a die pad having a die pad top surface and an opposing die pad bottom surface, leads laterally spaced apart from the die pad, and a substrate encapsulant interposed between the die pad and the leads and includes a substrate top surface and an opposing substrate bottom surface. The substrate encapsulant is provided such that the die pad and the leads protrude outward from the substrate bottom surface. The method includes providing an electronic device having opposing major surfaces and a pair of opposing outer edges. The method includes connecting the electronic device to the substrate such that one major surface of the electronic device is spaced apart from the die pad top surface and upper surfaces of the leads, and the outer edges overlap an opposing pair of the leads.