Applications

1. Cleanliness inspection of automotive pistons before painting;

2. Cleanliness detection of metal parts after cleaning and before spraying;

3. Controlling the cleanliness of parts before laser welding;

4. Evaluating the cleanliness of medical implants;

5. Cleanliness detection of residual solder slag on circuit board pads before bonding;

6. Monitoring the thickness of oil film layers;

7. Inspecting the cleanliness of die-cast housings before bonding/sealing;

8. Inspecting the cleanliness of stripped wires and terminals before friction welding.

The SITA CleanoSpector surface cleanliness measuring instrument developed by German SITA can detect even very small amounts of organic pollutants such as grease, lubricating oil, coolant, and wax on the surface of metal (glass, ceramic) through fluorescence measurement technology, ensuring that the cleanliness of metal parts for deep processing such as surface painting and treatment meets the requirements. This prevents the adhesion and firmness of the coating and adhesive bonding layer from being severely reduced due to residual pollutants on the surface during production processes such as painting, bonding, and welding.

Based on the test results, the surface cleanliness measuring instrument can provide reliable data for parameters such as cleaning time, chemical process, and soaking temperature in the entire cleaning process. It ensures that products meet high-quality requirements by monitoring the quality of metal parts. At the same time, staff can review production steps and optimize the cleaning process to improve work efficiency and reduce rework rates, meeting customer quality requirements. It can be seen that the German SITA surface cleanliness measuring instrument assists in stabilizing the cleaning quality during parts processing and achieving quantitative control!

The SITA CleanoSpector surface cleanliness measuring instrument is a portable testing device for part surface cleanliness with simple operation. It provides two ways to display measurement results for users to choose from:

• The first is to display the cleanliness value as a percentage. A cleanliness value of 100% indicates an absolutely clean and non-fluorescent surface;

• The second is to use RFU (Relative Fluorescence Units) to indicate the level of cleanliness. The RFU value represents the relative fluorescence intensity. The higher the RFU value, the higher the content of residual pollutants on the part surface. If the test piece itself has a fluorescent reaction, the RFU value will also increase accordingly.

Measurement Principle

Fluorescence Mechanism

Fluorescence is a form of luminescence that refers to the emission of light after atoms or molecules are excited, known as photoluminescence when photons are emitted. The fluorescence mechanism is shown in Figure 1. To excite fluorescence, an ultraviolet light source is used to irradiate the surface of the test piece. Pollutants on the surface of the test piece absorb high-energy radiation (1). Excited by photons, the electrons of the pollutants reach a higher energy level (2) - the excited state. The excited molecules collide with their environment and release a small part of the absorbed energy (3). The remaining energy is released as emission (4), and the electrons return from the excited state to their original state. The emitted photons have lower energy, thus releasing longer wavelengths (5).

In simple terms, ultraviolet light excites fluorescence. When pollutant electrons absorb photons, their energy increases, causing an electron cloud transition from a low energy level to a high energy level. However, the high-energy state is unstable, so the electrons return to their original energy level and release energy. Since part of the energy is consumed as heat, the emitted photons have lower energy and longer wavelengths.

The test parameters of the SITA surface cleanliness instrument are appropriately designed for common cleaning process pollutants. Because organic matter has a strong autofluorescence characteristic when excited by UV light, the instrument can detect organic pollutants such as grease, residual surfactants, and lubricating oil. It can also monitor the thickness of oil film layers such as preservatives or adhesives.

Fluorescence Spectrum

The above figure shows the fluorescence spectra of cooling lubricating oil and three different oils excited at a wavelength of 365 nm. Since they all have the strongest fluorescence intensity at a wavelength of 460 nm and can be detected for fluorescence values, the SITA surface cleanliness measuring instrument uses this wavelength to detect pollutant content.

Principle Demonstration

The SITA CleanoSpector surface cleanliness instrument uses a confocal method. It emits UV light of the optimal wavelength through a light source to detect pollutants on the metal surface, while a sensor on the other side detects the fluorescence intensity, which depends on the organic residue at the test point. Therefore, the probe can be flexibly positioned, and online measurement is easy to achieve.

With the combined effect of the UV light source and the sensor, the surface cleanliness instrument can quickly quantify test results to directly determine whether the cleanliness of the part surface meets the qualified range. The quantification of surface cleanliness helps stabilize the cleaning quality during parts processing, effectively avoiding phenomena such as reduced adhesion caused by oil stains on the product surface and virtual soldering or desoldering during welding, ensuring that the final product quality meets the requirements.

Advantages of the Surface Cleanliness Measuring Instrument

1. Quantitative and non-destructive testing of surface cleanliness for metal (glass, ceramic);

2. One-button operation, simple and easy to use;

3. High reproducibility;

4. Measurement results are not affected by ambient temperature;

5. Compared with dyne pens, it is less affected by product surface roughness;

6. Automatic calibration function, which can be completed on a clean metal surface;

7. Simple sensor design and stable testing;

8. Compact and portable, suitable for laboratories or factory workshops;

9. Provides online continuous detection solutions that can be highly integrated into existing production lines;

10. Optional scanning test solutions for continuous, non-destructive measurement of product surface cleanliness as required by customers;

11. Determines qualified/unqualified values based on specific pollutants and subsequent processes, guiding parameter setting or optimizing old and new cleaning processes, and quickly and intuitively evaluating processes.

Technical Parameters