The use of brittle materials like monocrystalline silicon, sapphire or lithium niobate has increased dramatically in the recent years. These materials possess superior mechanical, electrical, chemical and optical properties. Some examples, including silicon, have a moderate energy band gap leading to a small leakage current, whilst sapphire possesses high optical transmittance and heat resistance ability. Enabling their functionality would require shaping these materials. Conventionally, either lithography-based processes or grinding is used and although economical for high volume manufacturing, is limited to planar surfaces.
Mechanical micro-milling is a potential alternative. It is cheap to establish, capable to shape three dimensional freeform structures and compatible for manufacturing chemically inert materials (e.g sapphire and lithium niobate). However, machining-induced edge chipping, a type of surface edge defect, can be observed after mechanical micro-milling. The intensity of edge chipping increases with the machining depth and its presence may affect the device’s functionality.
The novel development presented here employs the concept of a hybrid manufacturing process and uses mechanical micro-machining as its primary shaping process. It involves depositing a layer of ductile material onto the surface of the brittle substrate. The choice of ductile material will depend on how easy it will be to coat the brittle substrate.
The mechanical micro-machining process begins from the deposited ductile material and advances into the brittle material substrate. Shaping of the intended profile is then processed according to the machining coordinates provided by the user. Upon completion, the deposited ductile material is removed to obtain the finished product.
Although the current solution presents each stage as an individual processing component, these stages could be implemented into a complete in-situ manufacturing process chain, whereby the deposition, machining and removal could be integrated. It is envisaged that the reduction of machining-induced chipping on brittle material machining could lead to other mechanical machining processes, such as drilling of VIA holes.
Potentially, this technology may be adopted in various specialised applications ranging from optics to medical and sensor technologies. For example, one may apply this invention to shape and singulate a silicon-based medical implant from a processed silicon wafer. Additionally, the invention may also be applied to shape microscale channels on lithium niobate for lightwave circuits in waveguiding applications for manufacturing of biosensors.
The mechanical micro-machining process is well established as a machining process for low volume rapid prototyping and manufacturing process, suitable for the fabrication of fracture free ductile materials. However, the machining quality of brittle materials such as silicon, could potentially be significantly enhanced with hybridization of the various processes presented in this invention.
The ability of this invention to significantly improve the machinability of brittle materials will enable developments in the capabilities of microscale mechanical micro-machining, especially in the area of creating three dimensional freeform functional structures on brittle materials.
The invention is available for license or co-development.
The technology is protected through a UK patent application which has been filed.
Title: Micro Machining Brittle Materials
UK patent application no: 1616955.9
Filing Date: 6 October 2016
Applicant: University of Newcastle upon Tyne
Sheena Shields, Science, Agriculture & Engineering Enterprise Team, Research and Enterprise Services, Devonshire Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK