Semiconductor Package Assembly for Ultrasonic-Welded Busbar Substrates
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Solution Overview
Problem
Current power semiconductor modules face challenges in achieving robust busbar attachment due to mechanical weakness of soldered joints, particle generation during welding, limited process window, and accessibility issues with ultrasonic or laser welding, which affect long-term reliability and manufacturing efficiency.
Innovation Solution
A semiconductor device package architecture with distinct substrates for semiconductor die and busbars, where the busbar substrate is made of a tougher and thicker material, allowing for ultrasonic welding without damaging ceramic substrates, and is positioned between semiconductor die substrates to facilitate robust attachment and separate processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soldering is used to attach busbars to substrates, then electrical connection is achieved, but mechanical strength is insufficient and additional epoxy potting is required
Solution Approach 1:
The patent replaces the mechanical soldering process with ultrasonic welding, which uses ultrasonic vibration energy to create direct metal-to-metal bonds between busbars and substrates. This substitution eliminates the need for solder and epoxy potting, providing sufficient mechanical strength through the welding process alone.
Solution Approach 2:
The patent changes the attachment method from thermal soldering to ultrasonic welding, altering the fundamental process parameters. Ultrasonic welding uses high-frequency mechanical vibration (typically 20-40 kHz) with controlled pressure and duration, creating strong bonds without requiring additional mechanical fastening or potting materials.
2Strength
If ultrasonic welding or laser welding is used to attach busbars, then strong mechanical connection is achieved, but particle generation occurs and process window is limited
Solution Approach 1:
The patent replaces laser welding with ultrasonic welding, substituting optical energy with mechanical vibration energy. This substitution eliminates the high-temperature melting and vaporization processes that generate particles, while still achieving strong mechanical bonds through direct metal-to-metal contact and ultrasonic consolidation.
Solution Approach 2:
The patent converts the potentially harmful high-energy process into a lower-energy ultrasonic process that achieves the same bonding strength without the harmful side effects. The ultrasonic energy is confined to the immediate bond interface, preventing widespread particle generation while maintaining connection strength.
3Strength
If ultrasonic welding is used for busbar attachment, then strong connection is achieved, but accessibility for welding tools is limited
Solution Approach 1:
The patent segments the module assembly process into distinct stages: substrate preparation, busbar attachment via ultrasonic welding, and final module assembly. This segmentation allows ultrasonic welding to be performed on individual busbars at accessible locations before final assembly, bypassing accessibility limitations in the confined module interior.
Solution Approach 2:
The patent performs busbar attachment as a preliminary action before final module assembly. By attaching busbars to substrates separately when accessibility is not constrained, the process avoids the accessibility limitations that would exist if welding had to be performed after complete module assembly.
4Reliability
If ceramic substrates are used for high electrical isolation and thermal conductivity, then electrical performance is improved, but mechanical robustness during busbar attachment is reduced
Solution Approach 1:
The patent replaces high-force mechanical attachment methods with ultrasonic welding, which uses vibrational energy rather than pure mechanical pressure. This substitution reduces the risk of damaging ceramic substrates during the attachment process while still achieving strong bonds, preserving both electrical performance and mechanical integrity.
Solution Approach 2:
The patent changes the attachment process parameters to be more gentle and controlled, using ultrasonic welding with precisely controlled amplitude, frequency, and duration. This allows strong bonds to form without subjecting the ceramic substrate to excessive mechanical stress that could compromise its structural integrity.
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 approach enables robust busbar attachment with reduced risk of substrate damage, improved process yield, and enhanced reliability by separating busbar welding from semiconductor chip assembly, allowing for independent optimization of substrate materials for thermal and electrical performance.
Implementation Method 1
The more recently developed ultrasonic welding or laser welding may provide very strong connections that don't require subsequent epoxy potting
Data Source
AI summary
A semiconductor device substrate assembly may include a first substrate, comprising: a first insulator plate; and a first patterned metal layer, disposed on the first insulator plate, wherein the first insulator plate comprises a first material and a first thickness. The assembly may include a second substrate, comprising: a second insulator plate; and a second patterned metal layer, disposed on the second insulator plate, wherein the second insulator plate comprises the first material and the first thickness. The assembly may also include a third substrate, disposed between the first substrate and the second substrate, comprising: a third insulator plate; and a third patterned metal layer, disposed on the third insulator plate, wherein the third insulator plate comprises a second material and a second thickness, wherein at least one of the second material and the second thickness differs from the first material and the first thickness, respectively.