PCBA conformal coating-Shenzhen PCBA factory
PCBA conformal coating

Some electronic products must work in harsh environments such as salt spray, sand or dust, extreme temperatures and terrain. Therefore, maintaining the performance of electronic products is as important as the normal situation. As the core of electronic products, PCB (printed circuit board) and PCBA (printed circuit board assembly) are responsible for implementing and facilitating functional implementation. If they can't work in a harsh environment, the final product will be damaged or even fail.
 
In fact, there are some techniques that can prevent end-electronics from encountering problems in harsh environment from the start, that is in the process of PCB manufacturing or PCBA manufacturing. Shenzhen PCBA factory SysPCB will provide some tips to help boards and assembly boards work better in harsh environments, mainly in two ways: conformal coating and cleaning.
 
1. Conformal coating
 
Conformal coatings are necessary for PCBs and PCBAs that must work in harsh environments. It protects the board from erosion, moisture, dust, etc., and ultimately extends the shelf life of the electronic product to ensure its performance and reliability.
 
It is a very important problem for electronic components and devices in manufacturing and application to maintain long-term stable performance in harsh environment. Therefore, necessary protective measures must be taken to ensure that electronic products work properly in harsh environments.
 
For harsh environments, the conformal coating should be optimized to better comply with extreme environments. Technical optimization should be carried out for the following items as protective measures: conformal coating shielding, static elimination and film thickness measurement
 
• Conformal coating shielding
 
Now, some parts of the PCB that do not require a conformal coating should be covered so that the conformal coating is not sprayed onto unnecessary parts (such as board holders, potentiometers, switches, power resistors, connectors). During the implementation of the conformal coating, the masking tape is usually used for the conformal coating shielding. In order to conform to the different shapes of the different components in the shield, the masking tape is cut into different shapes and sizes. This method tends to cause quality problems due to its disadvantages including low efficiency, static electricity generation, and excessive gel residue that are difficult to eliminate.
 
 
Optimization measures
 
Traditional masking tape should be replaced with 3M shielding tape. The cutting method should be used from the cutting of the tool to the application of a special cutting tool, since the latter can determine and cut different shapes depending on the shape, volume and size of the shielding cover. As long as the shield is covered with unnecessary parts, the conformal coating will not be sprayed on it.
 
• Conformal coating thickness measurement
 
The PCB surface is coated with a conformal coating, which is a thin, lightweight film that is only a few microns thick. This film effectively isolates the board surface from the environment and prevents the circuit from being attacked by chemicals, moisture and other contaminants. As a result, board reliability will be significantly improved, security factors will be enhanced, and shelf life will be guaranteed over the long term. However, due to the uneven coating, the protective function of the conformal coating is hesitant. As a result, both the PCB and the final product will fail, which is especially bad in harsh environments.
 
Optimization measures
 
The thickness measuring plate shall be made of a metal material and a special instrument shall be used. In addition, before the formal conformal coating is sprayed, the test spray should be performed first and then the thickness measured. Once all the parameters have been determined, the conformal coating can be applied in volume to achieve a standard thickness.
 
2. Circuit Board cleaning
 
PCB cleaning is designed to remove contaminants from the surface of the board, including gel residue, dust, oil, tiny particles and sweat to prevent corrosion or other defects on components, printed wires and solder joints. The ultimate goal is to improve the performance and reliability of electronic devices. In addition, the elimination of contaminants also helps to improve the combination between the conformal coating and the surface of the board and protect the product from harsh environments during operation and storage. Cleaning optimization should be performed based on analysis of post-weld cleanliness, surface ion residue, and flux residue.
 
In the PCBA manufacturing process, various types of contamination can be used for physical, chemical and mechanical, leading to oxidation and corrosion on the board, which will affect the reliability, electrical specifications and shelf life of the final product. The main pollution source contains elemental lead pollutants, pollutants generated during assembly and manufacturing, and pollutants and pollutants caused by poor working environment.
 
Currently, the largest contaminant damage circuit boards are present in flux contaminants. Flux is an organic acid-bound active agent that contains organic acid salts and halides, chloride or hydroxide all may become corrosive pollutants.
 
Optimization measures
 
First, severe damage should be analyzed, including component lead breaks, printed wire breaks, plated through hole defects, reduced solderability, and dark solder joints caused by chemical, physical, and mechanical contaminants. Then, the specific reasons for abnormal signal transmission, local heating and oxidation or even short-circuit should also be analyzed in order to complete the standards in terms of flux, solder paste and detergent.