Die soldering phenomena has been a problem encounter in die casting industry. Several methods already developed to mitigate and reduce their detrimental effect. Manganese was known for their capability to suppress the harmful effect of iron rich intermetallic phase. In this work, the effect of Manganese to the intermetallic layer morphology was investigated. The experiment was carried out by immersion of H13 into molten Al-Si alloys. The alloy was added 0.1-0.7% Mn with immersion time carried out for 10 to 60 minutes. The immersion held at various holding temperature of 680-740°C. The intermetallic layer was then characterized using micro hardness, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The result showed that compact and broken intermetallic layer was formed during immersion process. Observation also showed that Manganese reduced intermetallic layer thickness without reacted with the layer. Furthermore, mechanical properties by hardness method showed no significant changes of intermetallic layer hardness value in relation to the manganese addition.