Power Semiconductor Bonding Protrusion Prevents Conductor Breakage
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Solution Overview
Problem
Conventional ultrasonic bonding methods for power semiconductor devices face issues such as conductor pattern breakage and reduced bonding strength due to stress concentration and the presence of a soft member or copper projections, which can lead to unreliable connections and potential insulation failures.
Innovation Solution
A manufacturing method involving an electrode terminal laid on a protrusion with a hardness lower than the terminal, allowing the protrusion to deform under pressure and ultrasonic vibration, thereby preventing conductor pattern breakage and enhancing bonding strength without using a resin layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ultrasonic bonding is used to bond the electrode terminal over a large area, then the bonding strength is improved, but the conductor pattern is broken due to stress concentration
Solution Approach 1:
A resin layer is formed in advance at the bonding position on the conductor pattern before ultrasonic bonding. This preliminary action protects the conductor pattern from stress concentration during the bonding process, preventing breakage while allowing strong bonding between the electrode terminal and the conductor pattern.
Solution Approach 2:
The resin layer acts as an intermediary substance between the electrode terminal and the conductor pattern. It distributes the bonding stress and prevents direct stress concentration on the conductor pattern, thereby preventing breakage while maintaining bonding strength.
2Reliability
If a resin layer is provided between the electrode terminal and conductor pattern to prevent breakage, then the conductor pattern integrity is improved, but the bonding strength is reduced
Solution Approach 1:
The hardness of the resin layer is controlled to be lower than the conductor pattern (specifically, the resin layer has a Shore D hardness of 20-80, while the conductor pattern has a hardness of 70-100 HV). This parameter change allows the resin layer to deform and absorb stress during bonding, preventing conductor pattern breakage while maintaining sufficient bonding strength through proper material selection and processing.
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 method prevents conductor pattern and insulating layer breakage, achieves a stronger bonding area, and ensures reliable connections capable of handling larger currents with improved thermal and tensile stress resistance.
Implementation Method 1
the electrode terminal and the electrode layer are bonded together in such a manner that the protrusion deforms preferentially due to a pressure and ultrasonic vibration applied thereto by an ultrasonic horn
Implementation Method 2
a part of a surface to be bonded that is placed on a back-surface side of the electrode terminal makes contact with a head portion of the protrusion; and a step in which the electrode terminal and the electrode layer are bonded together in such a manner that the protrusion deforms preferentially due to a pressure and ultrasonic vibration applied thereto
Data Source
AI summary
An object of the invention is to provide: a manufacturing method for a highly reliable power semiconductor device which prevents breakage of an conductor pattern and an insulating layer, and has bonding strength higher than that by the conventional bonding between the electrode terminal and the conductor pattern; and that power semiconductor device. Breakage of the conductor pattern and the insulating layer is prevented due to inclusion of: a step of laying an electrode terminal on a protrusion provided on a conductor pattern placed on a circuit-face side of a ceramic board so that a center portion of a surface to be bonded of the electrode terminal makes contact with a head portion of the protrusion; a step of pressurizing and ultrasonically vibrating a surface opposite to the surface to be bonded, of the electrode terminal, using an ultrasonic horn, to thereby bond the electrode terminal to the conductor pattern.