Silicon-Aluminum Wire Bonding Without Plating
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Solution Overview
Problem
The high cost and complexity of connecting silicon (Si) and aluminum (Al) members in Micro-Electro-Mechanics (MEMS) devices due to the need for metal plating in electrode portions, which increases device price and complicates the connection process.
Innovation Solution
A connection structure and method using a Si oxide layer and an Al oxide layer interposed between Si and Al members, with a penetrating portion extending through the interposed layer to establish contact without the need for gold or aluminum plating, utilizing ultrasonic bonding and voltage application to form an ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold or aluminum plating is applied to electrode portions to enable wire bonding, then reliable connection between Si and Al is achieved, but manufacturing cost increases significantly and device price becomes high
Solution Approach 1:
The invention extracts and removes the expensive plating process (gold or aluminum plating) from the manufacturing flow. Instead of applying metal layers to electrode portions, the patent directly bonds aluminum wires to silicon electrodes through ultrasonic welding, eliminating the plating step entirely while maintaining reliable electrical connection.
Solution Approach 2:
The invention replaces expensive plating materials (gold, aluminum) with a direct ultrasonic bonding approach that uses inexpensive aluminum wires. The bonding process creates reliable connections without requiring costly metal layers, effectively substituting expensive materials with a more economical bonding method.
2Reliability
If gold or aluminum plating is applied to electrode portions, then wire bonding can be performed, but the manufacturing process becomes complex and time-consuming
Solution Approach 1:
The invention extracts and removes the plating process from the manufacturing sequence. By eliminating the steps of applying and drying metal layers, the patent simplifies the manufacturing process while maintaining reliable connections through direct ultrasonic bonding of aluminum wires to silicon electrodes.
Solution Approach 2:
The invention enables continuous manufacturing by eliminating the discontinuous plating steps. The ultrasonic bonding process allows for direct, continuous connection of aluminum wires to silicon electrodes without interruption for metal layer application and drying, thereby reducing overall process time and complexity.
3Reliability
If plating is applied to electrode portions, then electrical connection can be established, but fabrication time increases due to additional processing steps
Solution Approach 1:
The invention extracts and eliminates the time-consuming plating steps from the fabrication process. By removing the metal layer application and drying steps, the patent reduces total fabrication time while maintaining reliable electrical connection through direct ultrasonic bonding.
Solution Approach 2:
The invention performs preliminary preparation of silicon electrode surfaces (such as oxide layer removal or surface treatment) before bonding, so that direct ultrasonic bonding can proceed immediately without requiring subsequent plating steps. This preliminary surface preparation enables time-efficient direct bonding while ensuring reliable electrical connection.
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 reliable and cost-effective connections between Si and Al members, reducing the need for expensive plating and simplifying the fabrication process while maintaining electrical integrity.
Implementation Method 1
a bonding step of pressing the Al member against the Si member by using a solderless vibrating member and applying an ultrasonic wave to the solderless vibrating member to bond the Al member to the Si member
Implementation Method 2
a voltage applying step of applying a voltage between the Si member and the Al member bonded thereto. The bonding step includes forming an interposed layer composed of an Al oxide layer and a Si oxide layer between the Al member and the Si member and the voltage applying step includes partially removing the interposed layer to bring the Al member and the Si member into contact with each other
Data Source
AI summary
There is provided a connection structure between a Si electrode (Si member) and an Al wire (Al member). Between the Si electrode and the Al wire, a first part and second parts are present in interposed relation. Each of the first and second parts is in contact with the Si electrode and with the Al wire. In the first part, a Si oxide layer and an Al oxide layer are present. The Si oxide layer is in contact with the Si electrode. The Al oxide layer is interposed between the Si oxide layer and the Al wire. In some of the second parts, Al is present. In the others of the second parts, a Si portion and an Al portion are present.