If you are a procurement engineer or technical manager working in industrial automation and electronic equipment manufacturing, you must have encountered tricky soldering problems during PCBA mass production. QFN component soldering defects, especially large ground pad voiding and poor side solder wetting, are among the most common issues that disrupt production schedules, increase rework costs, and reduce the long-term reliability of your industrial circuit boards. These hidden quality risks will directly affect the heat dissipation performance and service life of power modules, control circuits and embedded hardware, bringing huge troubles to your product testing and market delivery. At Fumax, our professional engineering team has accumulated rich experience in troubleshooting complex SMT soldering issues for industrial PCBA projects, and today we will share practical solutions to help you eliminate QFN soldering failures thoroughly.
QFN packages are widely adopted in industrial control boards, automation drive modules and high-power electronic devices due to their compact size and excellent thermal conductivity. However, the large central ground pad underneath QFN chips easily generates massive voids during the reflow soldering process. The formation mechanism is simple: flux inside the solder paste decomposes and evaporates under high temperature, producing a large amount of gas. If the gas cannot escape smoothly before the solder alloy solidifies, it will be trapped inside the solder joint and form permanent voids.
These voids are not just cosmetic flaws. For ordinary consumer electronics PCBA, minor voids may be ignored, but for industrial-grade hardware such as IGBT modules and high-current control circuits, excessive voiding severely blocks heat conduction paths. It weakens mechanical bonding strength, accelerates component aging under continuous high-load operation, and even causes unexpected equipment shutdown in harsh industrial working environments. Many small and medium-sized manufacturers face frequent rework and low yield rates simply because they fail to control QFN voiding at the design and process stages.
After years of testing and on-site verification, Fumax summarizes five core factors that cause severe QFN voiding. First is the flux performance: excessive gas release and insufficient activation will trap residues and bubbles on the large ground pad. Second relates to solder paste composition; finer powder particles and higher metal content increase viscosity and hinder gas discharge during reflow. Third comes PCB surface treatment issues. Oxidation on pads and improper plating thickness such as Im-Ag coating will worsen wetting and expand void areas greatly. Fourth is unreasonable PCB layout design. Undivided oversized ground pads lack effective exhaust channels, making it impossible for internal gas to flow out freely. The last key factor is the reflow process curve and production atmosphere. Improper preheating time, mismatched peak temperature, and insufficient nitrogen protection all raise the void ratio significantly.
Figure 1higher metal content
In addition to voiding problems, many clients also struggle with QFN side non-wetting issues. Bare copper on QFN side edges is prone to oxidation, making standard solder paste unable to form qualified solder fillets. Without smooth side soldering, AOI inspection becomes difficult, and component structural stability cannot meet industrial reliability standards. Traditional solutions such as pre-coating extra flux or modifying component plating are costly and hard to apply in mass production.
Figure 2Surface Treatment
Fumax adopts targeted optimization strategies to solve both problems perfectly. We optimize PCB pad partitioning and stencil opening designs to create dedicated exhaust paths for large ground pads. Our engineers adjust the reflow profile with extended preheating and optimized peak time, and introduce nitrogen or vacuum reflow technology to remove trapped gas efficiently. We also select high-performance specialized solder paste with strong activation formulas to improve wetting performance for QFN side edges. In practical industrial projects including IGBT DBC substrate assembly, our professional adjustments reduced the void rate from over 5% to below 1%, fully meeting strict industrial quality standards.
Figure 3reflow profile
As a trusted supplier focusing on industrial PCBA manufacturing, Fumax provides one-stop turnkey PCB assembly services covering SMT assembly, through-hole assembly, professional PCB testing and box build assembly. Whether you need prototype PCB assembly, low volume small batch production or high volume mass manufacturing, our technical team optimizes every soldering detail to ensure stable quality for your automation electronic products. We support custom PCBA, ODM PCBA and OEM electronics assembly for various industrial scenarios, helping you cut production costs and improve overall yield effortlessly.
