Key points of water-based cleaning process for power devices

In order to obtain high-quality and high-reliability products, water-based cleaning processes are being used more and more widely in the production process of electronic devices and components today. Especially in 5G communications, aerospace, automotive electronics, military products, medical equipment, artificial intelligence and other industries and industrial products, the requirement of high reliability is to ensure the basis for the safe and reliable operation of the entire functional system. Water-based cleaning processes are outstandingly representative in the process of such devices and components, especially in large-scale production, which can effectively guarantee more reliable process indicators and stability. Usually, an online through-type cleaning process is used to realize the mass production process of devices and components. With the widespread application of online processes, the key points and proficiency of water-based cleaning processes are important factors in ensuring the quality of produced products. The following is an analysis of these key points.

1. For devices and components, such as POP, SIP, IGBT, and PCBA, cleaning is mainly to remove the residues and dirt of flux or solder paste produced during welding. First of all, the water-based cleaning agent should be selected and matched according to the cleanability of the solder paste and tin paste used for welding. The test should be carried out under conventional process conditions or specific process conditions. The water-based cleaning agent can completely remove the residues of flux and solder paste to meet the cleanliness requirements.
Matching is very important. It is necessary to consider not only the cleanability of the residues, but also the cleaning ability and strength of the water-based cleaning agent. Under the preset process conditions, the dirt can be completely removed to achieve the primary technical indicators.

2. The objects to be cleaned are often composed of a variety of materials, including metal materials, non-metallic materials, and chemical materials. For example, SIP usually includes gold-plated surface, silver surface, aluminum layer on chip surface, solder alloy surface, chemical coating layer on component surface, non-metallic materials of powder metallurgical devices, and chemical materials including solder mask, characters, etc., which need to be in the cleaning process and will not be affected or the impact is within the allowable range. Material compatibility is the most tedious and important consideration in water-based cleaning. The selection of water-based cleaning agents accounts for a large proportion of the consideration of material compatibility on the object to be cleaned, covers a wide range, and has complicated testing and verification procedures. A systematic and standardized verification method is needed to systematically verify and evaluate material compatibility. Only in this way can it be possible to ensure that the objects to be cleaned and other materials can maintain their original functional characteristics after the dirt is removed. Of course, the compatibility of the materials in contact with the operating equipment and the cleaning agent must also be considered. The pumps, valves, pipes, nozzles, conveying and sealing materials on the cleaning machine must be tested for material compatibility with water-based cleaning agents.

3. Evaluation and assessment of cleaning cleanliness. Two methods are often used.

First, observe the condition of the residue on the surface of the object to be cleaned with a naked eye at a magnification of 40 to 100 times, and the judgment is based on the absence of residue.

Second, use the surface ion contamination detection method to detect the surface of the object to be cleaned, and compare the detection data with the technical index requirements for evaluation. In actual production applications, special attention is paid to low support height and micro gap.

For example, the removal of residues at the bottom of the device, including Chip, QFN, chip or flip chip. Often when the residues at the bottom can be effectively removed, the residues at other parts should also be judged to be completely removed. The bottom of the QFM and the chip must be opened mechanically, and the condition of the residues at the bottom is observed to judge the cleanliness. In order to achieve the removal of residues at the bottom of the Micro gap, the physical and chemical properties of the cleaning agent (such as surface tension) and the angle, pressure, direction of the cleaning equipment spray, as well as the time and temperature of the spray have a great influence on the removal of dirt at the bottom.

4. The performance stability of the cleaning agent in the online through-type cleaning process requires corresponding technical means to monitor and control to ensure the performance of the cleaning performance or the stability of the material compatibility. Among these monitoring data, the most important is that the concentration of the cleaning agent is within the controllable range. It is recommended that users who use online spray through machines install online cleaning agent concentration monitoring devices to monitor the concentration changes of the cleaning agent during use. Due to the equipment characteristics of the online spray machine, the concentration of the cleaning agent changes greatly during use and operation. If the concentration of the cleaning agent cannot be effectively monitored, there will be risks in material compatibility. Generally speaking, as the cleaning agent runs in the machine, the concentration will increase over time. It is usually necessary to add DI water to ensure the stability of the cleaning agent concentration. Using an online concentration detector, the concentration can be controlled by adding water manually or automatically.

5. Consumption and life of cleaning agent. The consumption of water-based cleaning agents in online through-type sprayers consists of three components: aerosol loss, loss of the object to be cleaned and the mesh belt, and full liquid replacement when the cleaning agent reaches the end of its life. Among these three consumptions, the largest component is often aerosol loss, which is largely determined by the inherent mechanical properties of the sprayer. The degree of artificial adjustment is not high, and users need to pay attention to this technical indicator when selecting equipment. The life of the cleaning agent cannot be monitored by current technical means. Usually, in the production line, the end of the life of the cleaning agent is observed and detected based on the actual detection cleanliness standard of the production line, and then a part of the safety margin is retained and reserved as the basis for the full replacement of the cleaning agent.

Often users confuse the concentration and life of the cleaning agent. These two technical indicators belong to different technical contents. The factors affecting the life span are related to the selection of cleaning agents, the composition of dirt and the content of dirt on the object to be cleaned, the set cleaning temperature and the wear and tear of the equipment. Therefore, it is impossible to judge the life span of the cleaning agent in a simple and fixed way. It is necessary to accumulate data in actual production to define the life span of the cleaning agent.

6. Foam of cleaning agent and rinsing water. Because the cleaning agent and rinsing water are running under high temperature and high pressure in the spray machine, it is very easy to produce foam. Excessive foam affects the normal operation and status observation of the machine.

Therefore, the foam of the cleaning agent is allowed to be within a certain range to ensure the stability of the spray pressure of the cleaning machine. If there is too much foam or it is difficult to eliminate, the bubbles and air contained in the cleaning agent will reduce the cleaning spray pressure and affect the cleaning effect. The foam of the rinsing water is also worthy of attention. For the same reason, as long as the foam can be effectively eliminated, it will not affect the working state of the cleaning agent and the observation of the operation of the equipment.

7. About the odor generated during the operation of the online spray cleaning machine. When the spray cleaning machine is in operation, the machine is in a negative pressure state, and the air should flow from outside the machine to inside. Under this normal state, the smell of the cleaning agent should not spread outside the machine and affect the working environment and personnel experience. If the smell of the cleaning agent is found to escape and spread, the negative pressure state inside the machine should be adjusted to prevent the leakage of the cleaning agent and ensure the cleanliness of the working environment and air quality.

Welcome to call us for consultation on water-based cleaning process for device components and semiconductor chip packaging process cleaning. Lijing Chemical is a professional provider of water-based cleaning process and cleaning solutions for precision electronic components. We have extremely rich operating experience in the cleaning process of integrated circuit components, device modules, and chip packaging. Our water-based cleaning agent products are widely used in aerospace, military products, high-tech ships, rail transportation, new energy vehicles, autonomous driving supercomputers and data servers, power equipment, high-performance medical devices, and have received unanimous praise.