In the electronics assembly manufacturing industry, what we commonly refer to as a “Mirrored Panel Board” or “Flipped Panel Board” actually comes in two types. The first type is a different-side mirrored panel board, where one board’s top side and another board’s bottom side appear on the same panel. The second type is a same-side mirrored panel board, where all boards are oriented on the same side but are mirrored left to right, such as in a “pdpd” layout pattern.
We all know that when producing PCBs and PCBAs, multiple individual PCBs are usually combined into one larger panel, a process called panelization, to improve production efficiency. Typically, these individual boards are arranged in a neat and consistent manner with the same orientation. However, when the PCB has an irregular shape or special requirements, a mirrored panel or flipped panel design might be used. While this design can improve efficiency in the SMT production line and reduce material costs, it may also come with certain design and production challenges. In this article, we will explore these issues and consider potential solutions.
A reader recently asked: “In surface mount assembly, PCBs often warp or bend after going through the reflow process, which can cause issues like open solder joints or tombstoning. How can we overcome this?”
To be honest, the reasons behind PCB warping or bending may vary, but they can generally be traced back to the stress applied to the PCB exceeding what the material can handle. When stress is uneven across the PCB or when different areas of the PCB resist stress unevenly, warping or bending occurs.
The primary purpose of adding Nitrogen (N2) to the SMT reflow oven is to reduce oxidation on the soldering surface and improve the wettability of the solder joints. Nitrogen is a colorless, odorless, and chemically inactive gas. It belongs to the category of inert gases, meaning it doesn’t easily react with most metals to form compounds. By using nitrogen to replace the oxygen in the environment, we can prevent metals from reacting with oxygen, thus avoiding oxidation.
(This is a summary article, and the views expressed may not be entirely accurate. If you find any issues, feel free to share your opinions or feedback.)
These soldering wrinkles appeared quite a while ago, but Workingbear recently came across a similar situation on an online forum. Thinking others might encounter the same issue, I decided to document it for both personal reference and to share with everyone.
Workingbear had previously noticed that some data transmission cable samples from a supplier had solder joints on the internal PCBA with wave-like wrinkles and what looked like cracks. At first, it was assumed that these were caused by cracked flux residue. However, even after cleaning the flux with alcohol, the same wave-like wrinkles were still visible, indicating that the issue was actually with the solder itself.
