A method of forming a semiconductor package. Implementations include forming on a die backside an intermediate metal layer having multiple sublayers, each including a metal selected from the group consisting of titanium, nickel, copper, silver, and combinations thereof. A tin layer is deposited onto the intermediate metal layer and is then reflowed with a silver layer of a substrate to form an intermetallic layer having a melting temperature above 260 degrees Celsius and including an intermetallic consisting of silver and tin and/or an intermetallic consisting of copper and tin. Another method of forming a semiconductor package includes forming a bump on each of a plurality of exposed pads of a top side of a die, each exposed pad surrounded by a passivation layer, each bump including an intermediate metal layer as described above and a tin layer coupled to the intermediate metal layer is reflowed to form an intermetallic layer.

A method of forming a semiconductor package. Implementations include forming on a die backside an intermediate metal layer having multiple sublayers, each including a metal selected from the group consisting of titanium, nickel, copper, silver, and combinations thereof. A tin layer is deposited onto the intermediate metal layer and is then reflowed with a silver layer of a substrate to form an intermetallic layer having a melting temperature above 260 degrees Celsius and including an intermetallic consisting of silver and tin and/or an intermetallic consisting of copper and tin. Another method of forming a semiconductor package includes forming a bump on each of a plurality of exposed pads of a top side of a die, each exposed pad surrounded by a passivation layer, each bump including an intermediate metal layer as described above and a tin layer coupled to the intermediate metal layer is reflowed to form an intermetallic layer.

A method of forming a semiconductor package. Implementations include forming on a die backside an intermediate metal layer having multiple sublayers, each including a metal selected from the group consisting of titanium, nickel, copper, silver, and combinations thereof. A tin layer is deposited onto the intermediate metal layer and is then reflowed with a silver layer of a substrate to form an intermetallic layer having a melting temperature above 260 degrees Celsius and including an intermetallic consisting of silver and tin and/or an intermetallic consisting of copper and tin. Another method of forming a semiconductor package includes forming a bump on each of a plurality of exposed pads of a top side of a die, each exposed pad surrounded by a passivation layer, each bump including an intermediate metal layer as described above and a tin layer coupled to the intermediate metal layer is reflowed to form an intermetallic layer.

In a fabrication method for a package structure, a copper foil is provided, electroplating is performed on the copper foil to form a cavity sacrificial post, a dielectric material is laminated to form a dielectric layer, wherein an end face of the cavity sacrificial post is exposed to the dielectric layer, a wiring layer is formed on the dielectric layer, the cavity sacrificial post is removed by etching to form a through cavity, a bonding pad is formed on the wiring layer, a reverse side of a device is mounted on the copper foil in the through cavity, and a terminal of the device is wire-bonded with the bonding pad.

A method of forming a semiconductor package. Implementations include forming on a die backside an intermediate metal layer having multiple sublayers, each including a metal selected from the group consisting of titanium, nickel, copper, silver, and combinations thereof. A tin layer is deposited onto the intermediate metal layer and is then reflowed with a silver layer of a substrate to form an intermetallic layer having a melting temperature above 260 degrees Celsius and including an intermetallic consisting of silver and tin and/or an intermetallic consisting of copper and tin. Another method of forming a semiconductor package includes forming a bump on each of a plurality of exposed pads of a top side of a die, each exposed pad surrounded by a passivation layer, each bump including an intermediate metal layer as described above and a tin layer coupled to the intermediate metal layer is reflowed to form an intermetallic layer.

A method of forming a semiconductor package. Implementations include forming on a die backside an intermediate metal layer having multiple sublayers, each including a metal selected from the group consisting of titanium, nickel, copper, silver, and combinations thereof. A tin layer is deposited onto the intermediate metal layer and is then reflowed with a silver layer of a substrate to form an intermetallic layer having a melting temperature above 260 degrees Celsius and including an intermetallic consisting of silver and tin and/or an intermetallic consisting of copper and tin. Another method of forming a semiconductor package includes forming a bump on each of a plurality of exposed pads of a top side of a die, each exposed pad surrounded by a passivation layer, each bump including an intermediate metal layer as described above and a tin layer coupled to the intermediate metal layer is reflowed to form an intermetallic layer.

A package structure includes a substrate, a chip disposed on the substrate and having a backside surface away from the substrate, a heat sink disposed above the substrate and having a surface facing the back side surface, and a thermal interface material disposed between the chip and the heat sink. There is no organic adhesive between the chip and the heat sink. A method for forming the package structure is also provided.