A high power LED package based on a LTCC, a Multi Layer Ceramic-Metal Package, MLCMP, has been proposed. The MLCMP utilizes a large scale via slug for a heat sink slug whose cross sectional area is greater than an ordinary LED die size, which reaches up to 3 mm(2). The via slug along with ceramic body could be built simultaneously by one shot sintering with standard manufacturing process of a LTCC and no additional flattening process or post process was needed. On the other hand a large scale via slug of a MLCMP may result in undesirable defects such as de-lamination, cracking or cambering. However, those defects could be avoided by deliberately managing the fabrication process and sintering process. In particular, an inner surface coating with a low viscosity Ag paste was very effective for preventing the defects. As a result, we have succeeded in establishing a robust manufacturing process of a MLCMP that endures various reliability tests including a repetitive thermal shock test. Transient thermal analysis has revealed that the thermal resistance contributed to the MLCMP is less than 1.0 K/W. Considering the affordability and design flexibility, we anticipate the proposed MLCMP is not only suitable for high power LED packages but also a promising solution for illumination modules.