Folded Metal Contact Body for Low-Inductance SiC Module Assembly
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Solution Overview
Problem
Existing assembly methods for SiC-based power modules are inadequate for achieving low-inductance designs due to increased thermomechanical stresses and inductance contributions from wire bonding and conventional spacers, which can damage semiconductors during ultrasonic or laser welding processes.
Innovation Solution
A structured shaped metal body, preferably made of copper or aluminum, is used to protect the semiconductor chip during welding by providing elasticity and a sufficient contact surface, allowing for ultrasonic or laser welding of lead frames without damaging the chip, and enabling low-inductance connections through nanowire bonding or sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect the source potential to the substrate, then the connection is established, but the conductor tracks and wire length increase the inductance
Solution Approach 1:
The invention extracts and eliminates the wire bonding step from the assembly process. Instead of using wire bonds to connect the source potential, the lead frame is directly welded to the source contact on the chip, removing the additional inductance contributed by wire tracks and wire length while maintaining reliable electrical connection.
Solution Approach 2:
The invention merges the source potential connection function into the lead frame structure itself. The lead frame serves dual purposes: as the structural support element and as the electrical conductor for the source potential, eliminating the need for separate wire bonding and reducing overall inductance.
2Reliability
If ultrasonic welding or laser welding is used to fasten a lead frame to the chip, then direct connection is achieved, but the welding stresses and energy input destroy the semiconductor
Solution Approach 1:
The invention introduces an intermediary layer of solder between the lead frame and the chip's source contact. This solder layer acts as a buffer that absorbs the mechanical stresses and thermal energy from ultrasonic or laser welding, protecting the delicate semiconductor metallization from damage while still providing strong electrical and mechanical connection.
Solution Approach 2:
The solder layer is applied beforehand to the chip's source contact before the lead frame attachment. This pre-applied cushioning layer is specifically designed to withstand the subsequent welding process, protecting the semiconductor from the harmful effects of welding stresses and energy input.
3Strength
If a large adhesion surface is used for sintering or soldering the spacer to the chip, then strong bonding is achieved, but the tolerances transversely to the chip plane and tensions on the chip are problematic
Solution Approach 1:
The invention concentrates the bonding function to a localized area directly beneath the source contact on the chip, rather than using a large adhesion surface across the entire chip. This localized bonding approach maintains strong connection strength while minimizing the impact on transverse tolerances and reducing tensions distributed across the chip structure.
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 structured metal body reduces thermomechanical stresses and inductance, enabling reliable and durable connections for SiC-based power modules by absorbing mechanical and thermal stresses during welding processes.
Implementation Method 1
The shaped metal body (30) is elastic in the X- and Y- and in the Z-direction
Implementation Method 2
The shaped metal body (30) is connected to the semiconductor (10) by means of a sintered layer (50), in particular by means of silver sintering
Implementation Method 3
fastening an electrical conductor (40) to the shaped metal body (30) by means of ultrasonic welding
Implementation Method 4
fastening an electrical conductor (40) to the shaped metal body (30) by means of laser welding
Data Source
AI summary
Semiconductor module including a semiconductor and including a shaped metal body that is electrically contacted by the semiconductor, for forming a contact surface for an electrical conductor, wherein the shaped metal body is bent or folded. A method is also described for establishing electrical contacting of an electrical conductor on a semiconductor, said method including the steps of: fastening a bent or folded shaped metal body of a constant thickness to the semiconductor by means of a first fastening method and then fastening the electrical conductor to the shaped metal body by means of a second fastening method.