Thermo-compression Bonding for Microelectrode Deposition
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Solution Overview
Problem
Conventional methods struggle to reliably deposit microelectrodes with minimum thickness required for microelectronic devices, often necessitating additional patterning and shaping steps, which increases complexity and cost.
Innovation Solution
The use of thermo-compression bonding to attach thicker electrodes of various sizes directly onto microelectronic devices, reducing the need for further patterning or shaping by depositing pre-shaped electrodes and encapsulating them with insulating polymer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods (PVD, CVD, electro-chemical) are used to deposit microelectrodes, then the electrode thickness can be controlled, but the minimum thickness required for reliable performance is difficult to achieve consistently
Solution Approach 1:
The electrode deposition process is segmented into two distinct stages: first depositing a thin adhesive layer (5-50 nm) to ensure proper adhesion, then separately depositing the bulk electrode material to the required thickness. This segmentation allows each layer to be optimized independently, ensuring both reliable adhesion and sufficient thickness for electrical performance.
Solution Approach 2:
The adhesive layer is deposited in advance before the main electrode material. This preliminary action ensures that the substrate surface is properly prepared with a layer that promotes strong adhesion, allowing the subsequent bulk electrode deposition to achieve reliable thickness without adhesion failures that would compromise overall reliability.
2Device complexity
If pre-shaped electrodes are deposited and attached using thermo-compression bonding, then the number of fabrication steps is reduced, but additional equipment and process control are required
Solution Approach 1:
Electrodes of the desired final shape and size are deposited and attached to the substrate before other fabrication steps. This preliminary action eliminates the need for subsequent patterning, photolithography, and etching steps that would otherwise be required to create the electrode geometry, significantly reducing overall fabrication complexity.
Solution Approach 2:
Traditional mechanical patterning methods (photolithography, etching) are replaced with a deposition-based approach where the electrode geometry is defined during the deposition process itself. This substitution eliminates complex mechanical fabrication steps while achieving the same geometric precision.
3Reliability
If thicker electrodes are deposited to ensure minimum thickness requirements, then electrical performance is improved, but the deposition process becomes less reliable
Solution Approach 1:
The deposition process is divided into two separate deposition events: first a thin adhesive layer at low thickness precision requirements, then the bulk electrode material where precise thickness control is critical. This segmentation allows the thick electrode to be deposited with controlled precision without compromising the overall reliability, as the adhesion-critical thin layer is handled separately with appropriate precision controls.
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 allows for reliable assembly of microelectrodes with favorable electrical and mechanical properties, reducing fabrication steps and costs while enabling the deposition of extremely thick electrode materials, suitable for medical and harsh environment applications.
Implementation Method 1
a first layer of green ceramic material is screen printed onto a substrate
Implementation Method 2
the first layer of green ceramic material is fired to a temperature sufficient to sinter the ceramic material
Implementation Method 3
a layer of silver paste is screen printed over the first layer of green ceramic material
Implementation Method 4
the layer of silver paste is fired to a temperature sufficient to sinter the silver paste and form electrically conductive electrode traces
Implementation Method 5
This system permits reliable assembly of electrodes of various sizes. Additionally, this method reduces the number of fabrication steps (and potentially, cost) because the electrodes of desired shape and size are deposited
Data Source
AI summary
Thicker electrodes are provided on microelectronic device using thermo-compression bonding. A thin-film electrical conducting layer forms electrical conduits and bulk depositing provides an electrode layer on the thin-film electrical conducting layer. An insulating polymer layer encapsulates the electrically thin-film electrical conducting layer and the electrode layer. Some of the insulating layer is removed to expose the electrode layer.