A New Technology for Void-Free Reflow Soldering

Enclosed voids can cause a displacement of electrical and thermal paths as well as a local concentration of power and heat. Additionally, gas voids are quick to form spheres in the solder gap, which could cause the tilting of chip components and a wedge-shaped solder gap.

The amount of voids can be influenced by different measures such as a good wettability of metallization, solder pastes with special adopted solvents and an adequate preheating profile. However, to achieve virtually void-free solder joints, a special vacuum process step during soldering was demanded. This vacuum process is associated with some essential disadvantages. Apart from the technical expenses for vacuum pumps and additional locks, the vacuum process excludes the use of gas convection for heating, resulting in an uneven heat distribution on the assemblies.

SEHO’s MaxiReflow HP offers innovative technology that ideally combines convection heat and a special hyper-pneumatic module, thus ensuring virtually void-free solder connections. Instead of using a complicated vacuum process, MaxiReflow HP is equipped with an effective excess pressure chamber, allowing shorter cycle times and enabling gas convection to be used for heating assemblies.

Each heating zone of the MaxiReflow HP – as well as the zones integrated in the hyper-pneumatic chamber – has a tangential fan that ensures an absolutely homogeneous heat distribution with the large volume of ventilated process gas. This enables the most effective and component-sensitive heating of the products with set temperatures on a low level. When processing uncritical assemblies, the MaxiReflow HP, of course, also can be operated without activating the hyper-pneumatic chamber. In this case, the printed circuit boards go through a conventional reflow soldering process.