Molding compound supported RDL for IC package

A molding compound supported redistribution layer (RDL) structure for an integrated circuit (IC) package, the molding compound supported RDL structure comprising:

• a molding compound;
• a central cavity surrounded by the molding compound;
• a plurality of metal pillars partially embedded in the molding compound, each metal pillar among the plurality of metal pillars having a bottom end protruded below the molding compound;
• a plurality of solder balls, each directly configured on top of a corresponding metal pillar among the plurality of metal pillars;
• a redistribution layer having a plurality of bottom metal pads and a plurality of top metal pads;
• and
• a chip mounted on bottom of the plurality of bottom metal pads,
• wherein
• a density of the plurality of bottom metal pads is higher than the density of the plurality of top metal pads;
• the bottom end of each metal pillar among the plurality of metal pillars is electrically coupled to a corresponding top metal pad among the plurality of top metal pads;
• at least one of the plurality of top metal pads is located in the central cavity and is configured for mounting at least one passive element;
• and
• in a thickness direction of the RDL structure, the redistribution layer is arranged between the chip and the plurality of metal pillars.

A fabricating process for a molding compound supported redistribution layer (RDL) structure for an integrated circuit (IC) package, the fabricating process comprising:

• applying a release layer on top of a temporary carrier;
• applying a bottom seed layer on top of the releasing layer;
• forming a redistribution layer on top of the bottom seed layer, the redistribution layer having a plurality of bottom metal pads and a plurality of top metal pads;
• applying a top seed layer on top of the redistribution layer;
• forming a patterned photo resist on top of the top seed layer;
• forming a plurality of metal pillars, each on top of a corresponding top metal pad among the plurality of top metal pads;
• stripping the patterned photo resist;
• stripping the top seed layer between the plurality of metal pillars;
• applying a molding compound to encapsulate the plurality of metal pillars and to form a central cavity in a center of the molding compound;
• thinning the molding compound from top to expose top surfaces of the plurality of metal pillars;
• and
• mounting a chip on bottom of the plurality of bottom metal pads to obtain the molding compound supported RDL structure comprising:
• the molding compound;
• the central cavity surrounded by the molding compound;
• the plurality of metal pillars partially embedded in the molding compound, each metal pillar among the plurality of metal pillars having a bottom end protruded below the molding compound;
• the redistribution layer having the plurality of bottom metal pads and the plurality of top metal pads;
• and
• the chip mounted on bottom of the plurality of bottom metal pads,
• wherein
• a density of the plurality of bottom metal pads is higher than the density of the plurality of top metal pads;
• the bottom end of each metal pillar among the plurality of metal pillars is electrically coupled to a corresponding top metal pad among the plurality of top metal pads;
• at least one of the plurality of top metal pads is located in the central cavity and is configured for mounting at least one passive element;
• in a thickness direction of the RDL structure, the redistribution layer is arranged between the chip and the plurality of metal pillars;
• the redistribution layer further comprises a topmost dielectric layer;
• and
• the plurality of top metal pads and the bottom end of each metal pillar among the plurality of metal pillars are embedded in the topmost dielectric layer.