The described embodiments of mechanisms of forming a package on package (PoP) structure involve bonding with connectors with non-solder metal balls to a packaging substrate. The non-solder metal balls may include a solder coating layer. The connectors with non-solder metal balls can maintain substantially the shape of the connectors and control the height of the bonding structures between upper and lower packages. The connectors with non-solder metal balls are also less likely to result in bridging between connectors or disconnection (or cold joint) of bonded connectors. As a result, the pitch of the connectors with non-solder metal balls can be kept small.

A manufacturing method of an inductor structure includes the following steps. A protection layer is formed on a substrate, such that bond pads of the substrate are respectively exposed form protection layer openings of the protection layer. A conductive layer is formed on the bond pads and the protection layer. A patterned first photoresist layer is formed on the conductive layer. Copper bumps are respectively formed on the conductive layer located in the first photoresist layer openings. A patterned second photoresist layer is formed on the first photoresist layer, such that at least one of the copper bumps is exposed through second photoresist layer opening and the corresponding first photoresist layer opening. A diffusion barrier layer and an oxidation barrier layer are formed on the copper bump. The first and second photoresist layers, and the conductive layer not covered by the copper bumps are removed.

A pillar structure is disposed on a substrate. The pillar structure includes a pad, a metal wire bump, a metal wire, and a metal plating layer. The pad is disposed on the substrate. The metal wire bump is disposed on the pad. The metal wire is connected to the metal wire bump. The metal wire extends in a first extension direction, the substrate extends in a second extension direction, and the first extension direction is perpendicular to the second extension direction. The metal plating layer covers the pad and completely encapsulates the metal wire bump and the metal wire.

A pillar structure is disposed on a substrate. The pillar structure includes a pad, a metal wire bump, a metal wire, and a metal plating layer. The pad is disposed on the substrate. The metal wire bump is disposed on the pad. The metal wire is connected to the metal wire bump. The metal wire extends in a first extension direction, the substrate extends in a second extension direction, and the first extension direction is perpendicular to the second extension direction. The metal plating layer covers the pad and completely encapsulates the metal wire bump and the metal wire.

A semiconductor package includes a conductive pillar and a solder. The conductive pillar has a first sidewall and a second sidewall opposite to the first sidewall, wherein a height of the first sidewall is greater than a height of the second sidewall. The solder is disposed on and in direct contact with the conductive pillar, wherein the solder is hanging over the first sidewall and the second sidewall of conductive pillar.

A semiconductor package includes a conductive pillar and a solder. The conductive pillar has a first sidewall and a second sidewall opposite to the first sidewall, wherein a height and a total length of the first sidewall are respectively greater than a height and a total length of the second sidewall. The solder is disposed on the conductive pillar, wherein the solder is hanging over the first sidewall and the second sidewall of conductive pillar.

Liquid metal (LM) interconnects have angled features to reduce reflection loss and/or insertion loss of signals sent across the interconnects. The LM interconnects may be used to couple two electronic components, e.g., to physically and electrically couple an IC device and a circuit board together. One component has an array of LM wells, and the second component has a corresponding array of pins. The LM wells have tapered shapes, e.g., tapered sidewalls with LM within the sidewalls. A cap layer along seals the wells to hold the LM inside the wells. The pins on the second component have a flared portion that widens in the direction of the second component and tapers in the direction of the tip. When a pin is inserted into a corresponding LM well, the tip and straight (e.g., cylindrical) sections may be within the LM well, while the flared portion remains within the cap layer.