Dec 07, 2010 
SB6N58-A730 contains six percent Indium while still achieving low structural transformation. Indium additions lower melting points when compared to SnAgCu alloys such as SAC305. This lower reflow temperature is desirable for printed circuit boards. Lower reflow temperatures also increase the number and range of components available to the assembler – specifically allowing for the use of cheaper components that will not tolerate the higher reflow temperatures of SAC305 solder pastes. In the past, Indium alloys exhibited problems with structural deformation. This is caused by the early growth of a compound inside the structure, resulting in fine cracks due and strain stress.
Koki conducted an extensive investigation with multiple Indium alloys. The study focused on controlling the degree of structural transformation and thermal shock characteristics while maintaining a low melting point. Koki learned that these transformations occur as a result of a precipitation effect in Sn-In alloys that occur at lower temperatures. This can be directly controlled with measured additions of Indium. Through managing the upper limit of the thermal cycling test and the lower limit of the precipitation transformation, the start temperature can be controlled and deformation limited to an acceptable level.
Koki’s new SB6N58-A730 Low Temperature Lead-Free Paste provides less transformation within the alloy composition and a lower melting point.
