Lead Frame Hanging Lead Inclination for Wire Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor device manufacturing, the proximity of wires with different lengths connected to inner leads and bus bars increases the risk of wire shorts during resin encapsulation due to varying wire flow rates, particularly in high-pin-count lead frames where wires are densely located.
Innovation Solution
A lead frame design where the hanging lead is inclined with respect to the inner lead, displacing the wire connection face of the bus bar in the frame thickness direction, allowing for stable wire bonding and preventing short circuits by maintaining the bus bar and inner lead at the same level during bonding, and then returning to an inclined position after bonding to separate the wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the bus bar is positioned close to the inner lead to reduce device size, then the device compactness is improved, but the wire separation is insufficient causing increased risk of wire shorts
Solution Approach 1:
The bus bar is displaced in the frame thickness direction (vertical dimension) relative to the inner lead, creating spatial separation in the thickness direction while maintaining horizontal proximity. This dimensional transition allows wires to be adequately separated vertically without increasing horizontal device footprint, thus preventing wire shorts while maintaining compactness.
Solution Approach 2:
The hanging lead is designed with elastic deformation capability, allowing it to be temporarily deformed to the same level as the inner lead during wire bonding for stable connection, then return to its inclined position after bonding to separate the wires. This dynamic adjustment resolves the contradiction between needing close positioning for compactness and needing separation for reliability.
2Reliability
If the hanging lead is kept inclined to separate wires, then wire short prevention is improved, but stable wire bonding becomes difficult
Solution Approach 1:
The hanging lead transitions from an inclined static position to a temporarily deformed same-level position during wire bonding, then returns to inclined position afterward. This dynamic behavior allows the system to adapt to different process requirements: stable bonding during connection, and wire separation during encapsulation.
Solution Approach 2:
The hanging lead is pre-designed with elastic deformation capability and specific mechanical properties that allow it to be temporarily deformed to the same level as the inner lead before wire bonding occurs. This preliminary preparation enables stable wire bonding without requiring permanent structural changes.
3Ease of manufacture
If the bus bar wire connection face is at the same level as the inner lead, then wire bonding is simplified, but wire flow during encapsulation causes short circuits
Solution Approach 1:
The bus bar wire connection face is displaced from the same level to a different level in the frame thickness direction relative to the inner lead. This vertical displacement separates the wires in the thickness direction, preventing wire flow-induced short circuits during encapsulation while still allowing for simplified wire bonding through temporary elastic deformation.
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
This design prevents wire shorts during resin encapsulation by ensuring that wires connected to inner leads and bus bars are adequately separated, even when wire flow occurs, facilitating stable wire bonding and reducing the risk of short circuits in densely packed high-pin-count semiconductor devices.
Implementation Method 1
positioning the inner lead, the bus bar, and the hanging lead at the same level by pressing the inner lead and the hanging lead and elastically deforming the hanging lead
Data Source
AI summary
A lead frame includes a die stage; an inner lead provided near the die stage; and a bus bar provided between the die stage and the inner lead and supported by a hanging lead, wherein the hanging lead is inclined with respect to the inner lead, and a wire connection face of the bus bar is displaced with respect to a wire connection face of the inner lead in a direction of a frame thickness.