# US 7,608,916 B2 · Aluminum leadframes for semiconductor QFN/SON devices

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- Number: US 7,608,916 B2
- Document ID: US7608916B2
- Status: Granted
- Kind: B2
- Application number: 11/345,754
- Filed: 2006-02-02
- Published: 2007-08-02
- Granted: 2009-10-27
- Earliest claimed: 2006-02-02
- Assignees: Texas Instruments Incorporated
- Inventors: Donald C. Abbott
- Web page: https://patentgrep.com/patent/US7608916B2

## CPC

- H10W 70/457: {of metallic layers on leadframes}
- H10W 74/014: {using batch processing}
- H10W 72/0198: {batch processes}
- H10W 72/534: {being rectangular}
- H10W 72/536: {the connected ends being ball-shaped}
- H10W 72/5363: {the connected ends being wedge-shaped}
- H10W 72/5522: {comprising gold [Au]}
- H10W 72/5524: {comprising aluminium [Al]}
- H10W 72/5525: {comprising copper [Cu]}
- H10W 72/884: {Die-attach connectors and bond wires}
- H10W 74/00: Encapsulations, e.g. protective coatings
- H10W 90/736: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10W 90/756: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A post-mold plated semiconductor device has an aluminum leadframe (105) with a structure including a chip mount pad and a plurality of lead segments without cantilevered lead portions. A semiconductor chip (210) is attached to the chip mount pad, and conductive connections (212) span from the chip to the aluminum of the lead segments. Polymeric encapsulation material (220), such as a molding compound, covers the chip, the connections, and portions of the aluminum lead segments without leaving cantilevered segment portions. Preferably by electroless plating, a zinc layer (301) and a nickel layer (302) are on those portions of the lead segments, which are not covered by the encapsulation material including the aluminum segment surfaces (at 203b) formed by the device singulation step, and a layer (303) of noble metal, preferably palladium, is on the nickel layer.

## Claims

### Claim 1

A semiconductor device without cantilevered leads, comprising:
a leadframe made of aluminum alloy and having a structure including a chip mount pad and a plurality of lead segments;
a semiconductor chip attached to the chip mount pad;
conductive connections spanning from the chip to the aluminum surface of the lead segments;
polymeric encapsulation material covering the chip, the connections, and portions of the aluminum lead surface;
a zinc layer only on the aluminum lead surface that is not covered by the encapsulation material;
a nickel layer on the zinc layer; and
a layer of noble metal on the nickel layer.

### Claim 2 (depends on 1)

The device according to claim 1 further comprising reflow metals on the segment portions having the nickel layer.

### Claim 3 (depends on 1)

The device according to claim 1 wherein the noble metal is palladium.

### Claim 4 (depends on 3)

The device according to claim 3 further including a layer of gold over the layer of palladium.

### Claim 5 (depends on 1)

The device according to claim 1 wherein the conductive connections are bonding wires made of gold.

### Claim 6 (depends on 1)

The device according to claim 1 wherein the polymeric encapsulation is a molding compound.

### Claim 7

A semiconductor device; comprising:
an polymeric material encapsulating an aluminum leadframe except a portion of lead segments;
the un-encapsulated portion of the leadframe covered by a zinc film;
the encapsulated portion of the leadframe free of zinc; and
a conductive joint attached to the zinc covered portion of the leadframe, including a noble metal and nickel.

### Claim 8 (depends on 7)

The semiconductor device of claim 7, further comprising a semiconductor chip affixed to the leadframe.

### Claim 9 (depends on 8)

The semiconductor device of claim 8, in which the chip is encapsulated by the polymeric material.

### Claim 10 (depends on 7)

The semiconductor device of claim 7, further comprising a conductive wire connecting the chip to an aluminum surface of the leadframe.

### Claim 11 (depends on 10)

The semiconductor device of claim 10, in which the conductive wire includes copper.