Semiconductor Package Lead Layout for Stable Wire Bonding
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Solution Overview
Problem
The instability of leads during wire bonding in leadless semiconductor packages can result in a weaker bond due to the bouncing effect caused by ultrasonic energy, which affects the reliability of the electrical connection.
Innovation Solution
The semiconductor package design includes both active and inactive leads, where the inactive leads provide additional stabilization during assembly by being half etched and not exposed at the lower surface of the package, while the active leads are exposed and electrically coupled to the semiconductor die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If leadless packages are used to achieve small sized packages, then package size is reduced, but lead stability during wire bonding deteriorates
Solution Approach 1:
The leadframe is segmented into multiple individual leads that are strategically positioned and configured. Each lead is separated and independently structured to provide stability during wire bonding while maintaining the overall compact package design. The segmentation allows leads to be optimized for both size reduction and stability.
Solution Approach 2:
Different regions of the leadframe are given different properties - leads are designed with specific thicknesses, lengths, and configurations tailored to their functional requirements. Active leads have different characteristics than inactive leads, with local variations in geometry to optimize both compactness and stability during assembly.
2Strength
If ultrasonic energy is applied during wire bonding to achieve strong bonds, then bonding strength improves, but bouncing effect increases causing weaker bonds
Solution Approach 1:
The leadframe structure is pre-configured with inactive leads and specific geometric features that counteract the bouncing effect before wire bonding begins. The inactive leads are positioned to provide mechanical support and dampen vibrations during the ultrasonic bonding process, preventing the bouncing that would otherwise weaken bonds.
Solution Approach 2:
Inactive leads serve as intermediary elements between the active leads and the package body. These intermediate structures absorb and dissipate ultrasonic vibrations, acting as a buffer that protects the active leads from excessive bouncing while still allowing effective energy transfer for bonding.
3Reliability
If all leads are exposed at the lower surface to provide electrical connection, then electrical connectivity is improved, but manufacturing complexity increases
Solution Approach 1:
The leadframe structure incorporates inactive leads that serve multiple functions: they provide mechanical stability during assembly, act as structural support, and still contribute to the overall electrical connectivity through their integration with the package. This multi-functionality reduces the need for separate stabilization components.
Solution Approach 2:
Inactive leads are extracted from the active electrical connection pathway - they are positioned and configured to provide structural support without requiring exposure at the lower surface for electrical connection. This separation allows the active leads to be optimized for electrical connectivity while inactive leads handle mechanical stabilization.
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 inclusion of inactive leads enhances the stability during die attach and wire bond processing, reducing the bouncing effect and resulting in a stronger bond between the leads and conductive wires, thereby improving the reliability of the semiconductor package.
Implementation Method 1
The process of wire bonding the conductive wires may involve heat and ultrasonic energy
Data Source
AI summary
Generally described, one or more embodiments are directed to semiconductor packages comprising a plurality of leads and methods of forming same. The plurality of leads include active leads that are electrically coupled to bond pads of a semiconductor die and thereby coupled to active components of the semiconductor die, and inactive leads that are not electrically coupled to bond pads of the semiconductor die. The active leads have surfaces that are exposed at a lower surface of the semiconductor package and forms lands, while the inactive leads are not exposed at the lower surface of the package.