Laser Particle Size Analysis Method

The laser particle size analyzer is based on the laser scattering on the surface of the particle to be measured. The angle of the scattered light and the intensity of the light will vary depending on the particle size. According to the Mie scattering and Freund's diffraction theory, the particle size analysis can be performed.

The test method of the laser particle size analyzer can be divided into two types: dry method and wet method. The dry method uses air as a dispersion medium, and the turbulent dispersion principle enables the sample particles to be sufficiently dispersed, and the dispersed sample is introduced into the optical path system for testing. The wet method is to directly add the sample to a dispersion medium such as water or ethanol for dispersion, and then pass through the optical path system to calculate the particle size distribution. The dry and wet test methods differ depending on the dispersion medium. At present, most of the particle size analyzers are tested by the wet method, but the dry test has its advantages: the test speed is fast, the operation is simple, and the sample dissolved in water can be tested.

Nowadays, smart phones are becoming thinner and lighter, and mobile phone camera modules are getting smaller and smaller. How to process and handle such micro-components has become an important part of the development. Laser processing technology is an important tool in the field of micro-precision machining. It has high processing precision and can process various types of components, especially in the field of cameras. The PCB circuit board in the mobile phone camera module is composed of a soft and hard combination board of FR4 and FPC, and some of them are pure hard or soft boards. The application of laser technology to this sector is mainly for FR4 laser cutting and FPC laser cutting technology, and another astronomy laser pointer processing technology is to carry out two-dimensional code laser marking technology on FR4 or on FPC.

The laser standardization technology is mainly applied to the surface marking of the camera chip. It is usually marked with the logo of the enterprise and the related information of the product, and plays the role of brand promotion and downstream link management and operation. With the advancement of products, the introduction of the application of internal traceability systems, laser marking technology for chip surface QR is becoming more and more popular. There is a link conductive module on the bracket, and the conductive metal module inside is small and very thin. The laser welding technology can effectively strengthen the welding firmness, improve the conductivity and prevent damage. The glass in the camera module belongs to ultra-thin glass. It is not only unable to break it during processing, but also to ensure its strength and chipping rate. The advantage of using laser processing technology is that the processing speed is fast, the chipping is small, and the yield rate is good. high. The laser marking technology in the lens and motor is mainly a two-dimensional code of less than 0.5*0.5mm on the surface or edge mark, which plays the role of anti-counterfeiting and traceback. A small camera module has so many laser process technologies applied to it, and the importance of laser technology as an advanced process technology can be seen.

Repeatability comparison between dry and wet tests:

The repeatability index is an important indicator to measure the quality of the particle size distribution test. It refers to the deviation between multiple measurements of the same sample, usually expressed by the deviation between X50. The repeatability test of the particle size distribution has a great relationship with the degree of dispersion of the sample. When the sample is dispersed well, the repeatability of the test is also high.

The main factor affecting the repeatability test is the degree of dispersion of the sample, so the sample should be sampled before the test to ensure the uniformity of the sample. For the sample that is easy to agglomerate, the repeatability is poor, so whether it is dry test or wet test, it must be done. Good pre-treatment of the sample. Dry powder samples, pay attention to water drying. For some dry powder samples that are not well dispersed in water, it is necessary to add a dispersing agent to the dispersion medium, and set the ultrasonic dispersion time, stirring rate and other auxiliary dispersion conditions of the instrument. For wet testing, use a liquid sample that requires a uniform sample.

The emulsion and aqueous dispersion samples have good repeatability of the test results because the measured particles have been dispersed in the sample to form a stable system. The wet-tested dispersion medium has a great influence on the sample, and it is easy to react with the dispersion medium (water), or the sample having a small difference in refractive index with water should not be tested by wet method. For dense samples such as iron oxide, the dry test is poorly dispersible and can be tested using the wet method. By adding a dispersing agent, the ultrasonic time is prolonged, the stirring rate is increased, and the sample can be sufficiently dispersed, thereby improving the test repeatability of the sample.

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