 Using mobile telephones as a typical example, whilst downsizing of the electronic devices continues, more and more space saving components, such as BGAs and CSPs, are being widely used. It has become a critical issue that solder merging between the bumps and solder does not occur, and is referred to as ÅÉidden pillow defect¡¦under certain conditions.
The solder paste S3X48-M406-3 has been developed to solve this difficult technical problem, not only for bumped components, such as BGA, but also for chip and leaded components.
Due to various reasons, such as warpage of the package, inconsistent bump size, insufficient solder deposit, distortion of package during reflow etc., results in the solder bump being separated from the solder paste before the solder melts and wets to it. In the case of the solder bump being separated from the solder paste and heated in the reflow oven, the adverse effect occurs in two areas. Firstly, the area of the bump surface where it is in contact with the molten solder gets badly oxidized, and secondly, the flux activation of the solder paste will be quickly consumed as the solder melts, thus forming a layer of oxidized flux and solder on the surface.
When the bump descends onto the molten solder due to the weight of the package and wetting forces from the other joints, the oxide film formed on the surface of the molten solder paste and the molten solder bump with almost no flux activation, prohibits them from merging together.
Mechanism of occurrence of Pillow Defect
How to cope with it?
It seems difficult to completely prevent the separation of the bumps from the solder paste, so it is important to develop the solder paste featuring high heat resistance characteristics to protect the solder powder and bump from oxidation and sustain the activation strength of the flux for a long time at high temperatures, and furthermore to facilitate quick wetting reaction speeds to reduce the exposure time of the solder bump and secure sufficient time for the bump to collapse and merge with the molten solder paste.
- Design concept -
A new generation lead free solder paste; S3X48-M406-3 series has been developed based on such concept and helps reducing the pillow defect drastically.
For more details, click: Å¢nti-Pillow Defect Lead Free Solder Paste¡¦/a>.
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