In PCB manufacturing, the correct application and curing of ink play an indispensable role in protecting circuits, identifying component positions, and enhancing product aesthetics. However, during actual production, various factors may lead to uncured ink, which not only affects the appearance quality of the PCB but may also pose serious electrical hazards for subsequent assembly and use.
1. Analysis of Causes for Uncured Ink in PCB (Peeling Off When Scratched)
1. Human Oversight
The operators may not have followed the prescribed procedures, forgetting to set the correct curing parameters or failing to check whether the ink was cured, resulting in uncured ink.
2. Insufficient Baking Time or Temperature
If the temperature setting of the baking equipment is too low or the baking time is too short, the solvents in the ink cannot completely evaporate, leading to uncured ink.
3. Poor Ventilation Circulation in the Oven
If there is a problem with the ventilation circulation system in the oven, the solvents may not be expelled in time after evaporation, leading to increased humidity in the oven and affecting the curing effect of the ink.
4. Excessive PCB Boards or Thick Ink on the Baking Tray
When too many PCBs are placed on the baking tray, the heat distribution may be uneven, potentially causing some boards’ ink to not cure adequately. Additionally, if the ink is applied too thickly, the solvent evaporation requires longer time and higher temperature, which can also lead to uncured ink.
2. Potential Issues (Impact on PCBA)
1. Reduced Aesthetic Quality
Uncured ink can be easily scraped off, making the PCB surface uneven and affecting the product’s aesthetic quality.
2. Short Circuits
Uncured ink may flow during subsequent processing, coming into contact with circuits, leading to short circuits and affecting the electrical performance of the PCB.
3. Solutions
1. Solutions for Human Oversight
● Strengthen training for operators, establish detailed operating specifications and inspection processes, and require operators to check and record relevant parameters after completing the baking operation.
● Establish a responsibility system to hold accountable for quality issues caused by negligence, enhancing operators’ sense of responsibility.
2. Solutions for Insufficient Baking Time or Temperature
● Determine reasonable baking time and temperature parameters based on the characteristics of the ink and specifications of the PCB, and set corresponding parameters on the baking equipment.
● Install temperature and time monitoring devices to monitor the baking process in real-time, ensuring that baking conditions meet requirements.
3. Solutions for Poor Ventilation Circulation in the Oven
● Regularly check and maintain the oven’s ventilation circulation system to ensure that vents are unobstructed and fans are operating normally.
● Optimize the ventilation design of the oven to improve ventilation efficiency, allowing solvents to be expelled from the oven in a timely manner.
4. Solutions for Excessive PCB Boards or Thick Ink on the Baking Tray
● Control the number of PCBs baked at one time based on the oven’s capacity and heating capability to avoid overloading.
● Optimize the ink application process to control the ink thickness within an appropriate range, ensuring that the ink can fully cure under specified baking conditions.
By implementing the above measures, not only can various issues caused by uncured ink be effectively avoided, but the yield and overall quality of PCBs can also be further improved.
At the same time, continuously focusing on every detail of the production process and seeking opportunities for improvement is key to advancing the electronics manufacturing industry to a higher level. It is hoped that the analysis and suggestions provided in this article can help industry colleagues better address this challenge and jointly promote the healthy development of the industry.
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