Semiconductor Wire Bond Structure for Thermal Stress Relief
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Solution Overview
Problem
The separation of wires from leads in semiconductor devices due to thermal stress and shear stress at the interface, which can lead to device failure, particularly in high-current applications.
Innovation Solution
The configuration of the first wire in the semiconductor device includes a main part and a bond part that extend in different directions, with a specific angle and cross-sectional ratio, to distribute thermal stress and reduce shear stress, using materials like copper and aluminum for the wires and terminals, and a sealing resin for insulation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cross sectional area of the second wire is made larger to allow larger current flow, then the current carrying capacity is improved, but the thermal stress in the second wire increases leading to wire separation
Solution Approach 1:
The wire is divided into multiple segments (first wire and second wire) with different cross-sectional areas. The first wire has a larger cross-sectional area for current carrying, while the second wire has a smaller cross-sectional area to reduce thermal stress. This segmentation allows the system to simultaneously achieve high current capacity and reduced thermal stress at the bonding interface.
Solution Approach 2:
Different parts of the wire structure have different properties. The first wire portion has a larger cross-sectional area optimized for current conduction, while the second wire portion has a smaller cross-sectional area optimized for reducing thermal stress at the bonding interface. This local differentiation of properties resolves the contradiction between current capacity and bonding strength.
2Reliability
If the cross sectional area of the wire is increased to reduce resistance, then the electrical conductivity is improved, but the thermal stress and shear stress at the interface increase causing separation
Solution Approach 1:
The wire structure is segmented into two portions with different cross-sectional areas. The first portion has larger area for low resistance, while the second portion has smaller area at the bonding interface to minimize thermal and shear stress. This segmentation resolves the contradiction between electrical conductivity and stress reduction.
Solution Approach 2:
The second wire acts as an intermediary between the first wire and the third lead. It has a smaller cross-sectional area that serves as a stress-reducing transition zone, mediating between the high-current first wire and the bonding interface to the third lead, thereby reducing transmitted thermal and shear stress.
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 configuration effectively suppresses wire separation from terminals, allows for larger current flow, and enhances thermal dissipation and dielectric strength, while preventing corrosion and breakage.
Implementation Method 1
a first wire (30) conductively bonded to the first electrode (11) and the first terminal (21)
Implementation Method 2
the heat conducted from the first semiconductor element to the second wire generates thermal stress in the second wire
Data Source
AI summary
A semiconductor device comprises a semiconductor element including a first electrode located on one side in a first direction, a first terminal electrically connected to the first electrode and a first wire conductively bonded to the first electrode and the first terminal. The first wire includes a main part, a first bond part connected to one end of the main part, and a second bond part connected to another end of the main part. The first bond part is conductively bonded to the first electrode. The second bond part is conductively bonded to the first terminal. As viewed in the first direction, a direction in which the second bond part extends differs from a direction in which the main part extends.