Solid State Bonding Protective Coatings for Micro-Channel Devices
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Solution Overview
Problem
Conventional methods for preventing adherence of metal layers to platens during diffusion bonding, such as using release agents, can limit material choices, degrade surface finish, and are costly or impractical for high-temperature bonding, especially when maintaining a smooth surface finish is crucial for micro-channel devices.
Innovation Solution
Applying protective coatings to the surfaces of metal layers or platens that prevent adherence during diffusion bonding, using materials like TiN, TiCN, AlTiN, CrN/CrC, TiAlN/MoS2, and TiAlN, which are inert and stable at high temperatures and pressures, eliminating the need for release agents and ensuring a smooth surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If release agents are used to prevent adherence of metal layers to platens during diffusion bonding, then the metal layers can be successfully bonded, but the surface finish of the layers is degraded due to imprints from the separator sheet or powder
Solution Approach 1:
A separator sheet made of inert material (such as quartz, alumina, or ceramic) is introduced as an intermediary between the metal layers and the platens during diffusion bonding. This separator sheet prevents direct contact and adherence between the metal layers and platen surfaces, eliminating the need for release agents that would otherwise be required. The separator sheet maintains a smooth surface finish on the metal layers while still allowing effective heat and pressure transmission for successful bonding.
2Reliability
If separator sheets or release agents are used to prevent adherence, then bonding can proceed without material adhesion issues, but these methods are expensive or impractical for high-temperature bonding applications
Solution Approach 1:
The solution changes the material parameters of the separator sheet to withstand high-temperature diffusion bonding conditions. By selecting inert materials with high melting points and thermal stability (such as quartz, alumina, or ceramic), the separator sheet maintains its structural integrity and non-adhering properties throughout the high-temperature bonding process, making the method practical and cost-effective for high-temperature applications.
Solution Approach 2:
The separator sheet is made from chemically inert materials that do not react with or adhere to the metal layers being bonded, even at high temperatures. This creates an inert interface between the platen and metal layer, preventing adherence issues without requiring expensive release agents or complex process controls, thereby improving ease of manufacture for high-temperature bonding.
3Manufacturing precision
If conventional machining is used to create small flow channels in micro-fluidic devices, then the channels can be manufactured, but the channels are too small to be created by conventional machining methods
Solution Approach 1:
The device is segmented into multiple thin metal layers that are individually machined or formed with the desired channel patterns, then bonded together to create the complete micro-fluidic device. This segmentation allows conventional machining to be used on individual layers at manageable thicknesses, while the final assembled device achieves the required small channel dimensions that would be impossible to machine directly in a single piece.
Solution Approach 2:
The manufacturing approach transitions from creating all features in a single three-dimensional workpiece to a multi-layer stacked architecture. By distributing the channel formation across multiple two-dimensional layers and then bonding them together, the effective channel dimensions become sufficiently small for micro-fluidic applications while each individual layer remains manufacturable by conventional techniques.
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 protective coatings effectively prevent adherence to platens and separators, maintaining a smooth surface finish and allowing for the use of a wider range of materials, even at high temperatures and pressures, thus enhancing the manufacturing process for micro-channel devices.
Implementation Method 1
A pressure is applied to the first and second layers via the first and second platens while heating the first and second layers to a temperature at which the first and second layers undergo diffusion bonding between the bottom surface of the first layer and the top surface of the second layer
Data Source
AI summary
A method for solid state bonding of a plurality of metallic layers and devices made by that method are disclosed. First and second metallic layers are solid state bonded utilizing a protective coating on the non-bonded surfaces that engage the pressure applying appliance to prevent the surfaces from adhering to the pressure applying appliance and to protect the surfaces from imprinting during the bonding process. The invention can be used to fabricate micro-channel devices with smooth outer surfaces and eliminate mold release compounds utilized in conventional bonding procedures.