Wafer-Level Back-to-Front Electrical Connections for Power MOSFETs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor packaging methods for vertical power MOSFET devices are expensive, time-consuming, and inefficient due to the need for preformed U-shaped clips and solder bumps, which limit heat dissipation and increase production costs, especially in high current applications.
Innovation Solution
A wafer-level chip scale packaging process that enables back-to-front electrical connections using conductive materials like carbon or carbon nanotubes, eliminating the need for preformed clips and solder bumps, and allowing for batch handling with reduced equipment and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional epoxy or solder die attach with aluminum or gold wire bonding is used, then packaging reliability is maintained, but manufacturing cost and complexity increase
Solution Approach 1:
The patent merges multiple discrete packaging steps (die attach, wire bonding, encapsulation) into a single wafer-level process where conductive material is applied directly to the wafer surface before singulation, eliminating the need for separate assembly operations on individual devices
Solution Approach 2:
The conductive material is applied to the wafer surface in advance before the wafer is cut into individual devices, so that electrical connections are already in place when devices are separated, eliminating the need for post-singulation assembly operations
2Temperature
If preformed U-shaped clips and solder bumps are used for electrical connections, then electrical connectivity is ensured, but heat dissipation capability deteriorates
Solution Approach 1:
The patent removes the intermediate U-shaped clip structure entirely, allowing the drain electrode to contact the mounting substrate directly through applied conductive material, creating a shorter and more efficient thermal path while maintaining electrical connectivity
Solution Approach 2:
The patent transitions from point-contact electrical connections (solder bumps) to a planar surface contact approach where conductive material is applied across the entire drain surface, increasing the contact area for both electrical and thermal transfer
3Adaptability or versatility
If different U-shaped clips are used for different die sizes, then electrical connection adaptability is improved, but manufacturing complexity and space requirements increase
Solution Approach 1:
The patent creates a universal packaging process where the same conductive material application technique works for all die sizes, eliminating the need for different clip designs and reducing tooling complexity while maintaining adaptability to various device dimensions
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 process reduces production costs and complexity, enhances heat dissipation, and is flexible across different die sizes without requiring tooling changes, while minimizing thermal stress and mechanical damage to semiconductor chips.
Implementation Method 1
conductive material 110, which will be added later in the process... provide electrical connection from the drain electrode 107
Implementation Method 2
mounting the semiconductor wafer 100 to a package substrate 101
Data Source
AI summary
A method for making back-to-front electrical connections in a wafer level chip scale packaging process is disclosed. A wafer containing a plurality of semiconductor chips is mounted on a package substrate. Each semiconductor chip in the plurality includes one or more electrodes on an exposed back side. Scribe lines between two or more adjacent chips on the wafer are removed to form relatively wide gaps. A conductive material is applied to the back side of the semiconductor chips and in the gaps. The conductive material in the gaps between two or more of the chips is then cut through leaving conductive material on the back side and on side walls of the two or more chips. As a result, the conductive material provides an electrical connection from the electrode on the back side of the chip to the front side of the chip.