A question from a netizen, “In the past, many mobile phone PCB assemblies would use Underfill depositing under the BGA package to enhance the mechanical strength of the solder joints. However, it has been found that most mobile phone assemblies no longer use underfill today. Is Underfill still necessary for the BGA on PCB? What is the relationship between using or not using Underfill and product quality? How should it be defined?”
Questions from a newcomer about electronic manufacturing assembly process: Since there are already solder balls locate on the BGA substrate, why is it necessary to apply solder paste on the PCB pads during SMT reflow? Is it necessary to apply solder paste during BGA repair? And how should we apply solder paste to the corresponding pads on the BGA when there are other electronic components around the BGA?
Before the development of Surface Mount Technology (SMT), almost all printed circuit board assemblies (PCBAs) had to go through the process of wave soldering to achieve the purpose of soldering electronic components to the board.
The process of “wave soldering” gets its name from using a large pool of molten tin during the soldering process. This pool of tin is heated to a temperature where the solid tin bar can melt and form a solution. This molten solution can be thought of as a “lake”. When the lake is still, it is called a “laminar wave”. When the lake is agitated, it becomes a “turbulent wave”. The PCB is like a boat sailing on the surface of the lake, allowing the molten tin solution to adhere to the electronic components and the PCB. After the soldered parts pass through the molten tin, it rapidly cools and solder the electronic component to the PCB.
All materials actually have its shelf-life, some shorter and some longer than others. So what happens when expired materials are used? Think about what will happens when you eat expired food. What about using expired Printed Circuit Boards (PCBs)?
This is just a summary article about PCB surface finishes. Workingbear has only worked on the electronic system assembly factory and has not been involved in the production process of bare PCBs. Therefore, the following insights are based on personal opinions. If you have different opinions or notices any mistakes, please feel free to comment and engage in discussion.
The main purpose of PCB surface finishes or call treatment is to protect the copper layer on the surface of PCB from direct contact with air, and prevent oxidation.It also facilitates effective soldering, whether directly or indirectly, with the solder, ensuring electrical conductively attaching electronic components.
