Semiconductor device having improved contacts
First Claim
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1. A device comprising:
- a semiconductor chip;
a substrate, on which the chip is assembled, having contacts for external connections;
each contact including;
a contact area with copper;
an alloy layer covering the contact area, the alloy layer including copper/tin alloys and copper/nickel/tin alloys, metallurgically attached to the copper area and substantially free of regions of unalloyed nickel;
the copper/nickel/tin alloys including (Cu, Ni, Au)6Sn5 intermetallic compound;
a reflow element comprising tin metallurgically attached to the alloy layer; and
the substrate further having a second contact area with copper and a region over the copper including nickel and gold;
the semiconductor chip mechanically assembled on the substrate.
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Abstract
A device with a solder joint made of a copper contact pad (210) of certain area (202) and an alloy layer (301) metallurgically attached to the copper pad across the pad area. The alloy layer contains copper/tin alloys, which include Cu6Sn5 intermetallic compound, and nickel/copper/tin alloys, which include (Ni,Cu)6Sn5 intermetallic compound. A solder element (308) including tin is metallurgically attached to the alloy layer across the pad area. No fraction of the original thin nickel layer is left after the reflow process. Copper/tin alloys help to improve the drop test performance, nickel/copper/tin alloys help to improve the life test performance.
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Citations
16 Claims
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1. A device comprising:
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a semiconductor chip; a substrate, on which the chip is assembled, having contacts for external connections; each contact including; a contact area with copper; an alloy layer covering the contact area, the alloy layer including copper/tin alloys and copper/nickel/tin alloys, metallurgically attached to the copper area and substantially free of regions of unalloyed nickel; the copper/nickel/tin alloys including (Cu, Ni, Au)6Sn5 intermetallic compound; a reflow element comprising tin metallurgically attached to the alloy layer; and the substrate further having a second contact area with copper and a region over the copper including nickel and gold; the semiconductor chip mechanically assembled on the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device comprising:
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a substrate having contacts on a first surface; each contact having a contact area with a copper surface, substantially free of regions of unalloyed nickel, metallurgically attached to an alloy layer including copper/nickel/tin alloys and copper/tin alloys; the alloy layer further including a (Ni, Cu)6Sn5 intermetallic compound and a Cu6Sn5 intermetallic compound; a solder element including tin metallurgically attached to the alloy layer; and a semiconductor chip attached to the substrate on a second surface opposite the first surface. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification