Instrument for Measuring Residual Stress of Thin Films on Flexible Transparent Substrates

Abstract

The invention provides a measuring instrument for film residual stress of a flexible transparent substrate. The measuring instrument comprises an optical platform, a first supporting rod, a light path system, a laser source system, a sample supporting system and a light spot tracking three-dimensional moving system. The laser source system and the light path system are fixed on the first supporting rod. The first supporting rod is fixed on the optical platform. The light spot tracking three-dimensional moving system and the sample supporting system are respectively arranged on the edges at two sides of the optical platform. The measuring instrument is capable of measuring the film stress of a flexible and transparent substrate with a relatively small curvature radius, the curvature radius is accurately measured by a single light beam optical lever method, a laser source is firstly focused to improve the unit area power of light spots, a three-point positioning method is utilized to fix the sample so as to ensure the relative initial positions in front and at the back of a long film, the measurable range of light spot deviation is greatly increased by the light spot tracking system, and the film residual stress is finally obtained by a corrected Stoney formula.

Description

technical field [0001] The invention relates to a film residual stress measurement technology, in particular to a measuring instrument for a film residual stress on a flexible transparent substrate. Background technique [0002] As a next-generation display technology, flexible display has attracted widespread attention due to its advantages such as bendability, ultra-thin design, ultra-low power consumption, durability, and portability. PEN film, PET film, etc. are often used as flexible substrates, on which flexible organic electroluminescent devices are encapsulated by atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD), etc. The mature thin film packaging technology plays a vital role in the promotion of flexible display applications, and the packaging effect is closely related to the residual stress of the film. Therefore, it becomes meaningful to test the residual stress of thin films on flexible substrates. [0003] Stoney et al. used fo...

AI Technical Summary

Problems solved by technology

[0007] (1) Many flexible substrates are transparent and have low reflectivity (such as PET reflectivity is less than 10%). When using the optical lever method, the effective signal received by the spot displacement sensor is relatively weak, and the surrounding stray light and dark current will be relatively large, reducing the signal-to-noise ratio and increasing the measurement error

[0008] (2) The operation is not convenient enough to ensure that the relative initial position of the substrate before and after the long film is consistent. The aspect ratio and surface flatness of the sample are strictly limited, which greatly affects the range and ability of the film stress test.

[0009] (3) The flatness of the flexible substrate itself is large, so that the local radius of curvature is too small, or the deformation of the film under the action of residual stress is relatively large, so that the radius of curvature is too small, which greatly exceeds the measurement range of existing instruments

[0010] (4) The difference between the Young's modulus of the flexible substrate and the film is large, which does not satisfy the assumption that the Young's modulus of the Stoney formula is similar, which will cause a large error

Images