TO263 Package Up-Set Bonding Pad Mold Flow Aperture
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Solution Overview
Problem
Existing TO263 semiconductor packages are highly sensitive to moisture, leading to delamination failures during reflow processes and other high-temperature operations, which limits their usage conditions and reliability.
Innovation Solution
A lead frame configuration with a die attach pad, elongate ground leads, and up-set bonding pads with mold flow apertures is used, along with elongate I/O leads and a shaped integral ground lead to enhance encapsulant adhesion and prevent delamination, allowing for a more robust package design with improved moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional TO263 package configuration is used, then manufacturing cost is reduced, but moisture sensitivity increases leading to delamination failures
Solution Approach 1:
The package structure is segmented into distinct functional regions: a recessed cavity region that receives the semiconductor die, a raised barrier region surrounding the cavity, and a planar sealing region. This segmentation creates natural moisture barriers and stress distribution zones that prevent delamination while maintaining manufacturing feasibility.
Solution Approach 2:
The package design transitions from a traditional planar configuration to a three-dimensional structure with raised barriers and recessed cavities. This dimensional change creates physical barriers that block moisture migration paths and provide stress relief zones, significantly improving moisture resistance without substantially increasing manufacturing complexity.
2Reliability
If existing package design is used, then ease of manufacture is maintained, but delamination failures occur during reflow processes
Solution Approach 1:
The mold compound is configured to flow into and fill the recessed cavity region before final curing, creating a pre-formed barrier structure that prevents moisture ingress. This preliminary action of shaping the mold compound into the cavity creates inherent delamination resistance without requiring additional manufacturing steps.
Solution Approach 2:
The package design utilizes changes in the physical parameters of the mold compound, including its viscosity during flow and its expansion characteristics during curing. The compound is formulated to flow into the recessed cavity at specific temperature ranges and then expand to fill the barrier regions, creating a self-sequencing manufacturing process that improves reliability without complicating fabrication.
3Reliability
If conventional sealing structure is used, then device complexity is minimized, but moisture sensitivity level is limited to MSL3
Solution Approach 1:
The package employs a composite sealing structure combining the semiconductor die, lead frame, mold compound, and optional conformal coating in a multi-material assembly. Each material is selected for its specific moisture barrier properties and thermal characteristics, creating a synergistic structure that achieves MSL3 certification and beyond while managing the complexity through functional integration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The new package design significantly reduces delamination failures and increases moisture resistance, enabling operation beyond JEDEC Moisture Sensitivity Level 3, making it suitable for a wider range of process conditions and environments.
Implementation Method 1
the mold material of the mold envelope flows through the aperture encapsulating the package with the mold material
Implementation Method 2
the mold material of the mold envelope flows through the aperture encapsulating the package with the mold material
Data Source
AI summary
A lead frame and package construction configured to attain a thin profile and low moisture sensitivity. Lead frames of this invention may include a die attach pad having a die attachment site and an elongate ground lead that extends from the die attach pad. The lead frame includes a plurality of elongate I/O leads arranged about the die attach pad and extending in said first direction. An inventive lead frame features an “up-set” bonding pad electrically connected with the die attach pad and arranged with a bonding support for supporting a plurality of wire bonds. The lead frame also having a large mold flow aperture in the up-set bonding pad. A package incorporating the lead frame is further disclosed such that the package includes an encapsulant that surrounds the bonding support and flows through the large mold flow aperture to establish well supported wire bonds such that the package has low moisture sensitivity.