Terminal structure and wiring substrate
A terminal structure of a wiring substrate includes a wiring layer, a protective insulation layer including an opening that partially exposes an upper surface of the wiring layer, and a connection terminal formed on the wiring layer. The connection terminal includes a base portion formed in the opening and a connection portion formed on the base portion. The connection portion projects from an upper surface of the protective insulation layer. A gap is formed between a side surface of the base portion and a wall surface of the opening.
1. A terminal structure comprising:
a wiring layer;
a protective insulation layer including an opening that partially exposes an upper surface of the wiring layer;
a metal layer formed on the upper surface of the wiring layer in the opening;
an alloy layer formed on the metal layer; and
a connection terminal formed on the alloy layer, wherein:
the connection terminal includes
a base portion formed in the opening and connected to the wiring layer by the alloy layer and the metal layer, and
a connection portion formed on the base portion and projecting from an upper surface of the protective insulation layer,
wherein a gap is formed between a side surface of the base portion and a wall surface of the opening, and
wherein the side surface of the base portion is free from the alloy layer;
the upper surface of the wiring layer includes a recess;
the protective insulation layer includes a projection located above a peripheral portion of the recess; and
the metal layer is formed in the recess to fill a gap between a lower surface of the projection and the wiring layer.
2. The terminal structure according to claim 1 , wherein
the alloy layer contains a tin-copper alloy.
3. The terminal structure according to claim 1 , wherein the entire side surface of the base portion is spaced apart from the wall surface of the opening.
4. The terminal structure according to claim 1 , wherein the side surface of the base portion is spaced apart from at least an upper end of the wall surface of the opening.
5. A wiring substrate comprising:
a wiring layer;
an insulation layer formed on the wiring layer; and
the terminal structure of claim 1 , wherein the terminal structure is formed on the insulation layer.
6. The terminal structure according to claim 1 , wherein
the connection terminal contains tin.
7. The terminal structure according to claim 1 , wherein
the wiring layer is formed from copper or a copper alloy.
8. The terminal structure according to claim 1 , wherein
the metal layer contains nickel, palladium, or gold.
9. The terminal structure according to claim 1 , wherein
the opening is tapered in a cross-sectional view to have a diameter that is gradually decreased from the upper surface of the protective insulation layer toward the upper surface of the wiring layer,
the base portion is tapered in a cross-sectional view to have a diameter that is gradually decreased from an upper end of the base portion toward a lower end of the base portion.
10. The terminal structure according to claim 1 , wherein
the metal layer covers an upper surface of the projection.