# US 9,039,942 B2 · Lead-free conductive paste composition and semiconductor devices made therewith

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- Number: US 9,039,942 B2
- Document ID: US9039942B2
- Status: Granted
- Kind: B2
- Application number: 13/332,629
- Filed: 2011-12-21
- Published: 2013-06-27
- Granted: 2015-05-26
- Earliest claimed: 2011-12-21
- Assignees: E. I. Du Pont de Nemours and Company
- Applicants: Carmine Torardi; Paul Douglas Vernooy
- Inventors: Carmine Torardi; Paul Douglas Vernooy
- Web page: https://patentgrep.com/patent/US9039942B2

## CPC

- H10F 77/211: {for photovoltaic cells}
- C09D 5/24: Electrically-conducting paints {(conductive materials H01B1/00)}
- H01B 1/16: the conductive material comprising metals or alloys
- H01B 1/22: the conductive material comprising metals or alloys
- H10F 71/121: {The active layers comprising only Group IV materials}
- H10F 77/122: comprising only Group IV materials
- Y02E 10/50: Photovoltaic [PV] energy
- Y02E 10/547: Monocrystalline silicon PV cells
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K})
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A lead-free conductive paste composition contains a source of an electrically conductive metal, a fusible material, an optional additive, and an organic vehicle. An article such as a high-efficiency photovoltaic cell is formed by a process of deposition of the lead-free paste composition on a semiconductor substrate (e.g., by screen printing) and firing the paste to remove the organic vehicle and sinter the metal and fusible material.

## Claims

### Claim 1

A paste composition comprising in admixture:
(a) a source of electrically conductive metal;
(b) a fusible material comprising:
50-90 wt. % Bi2O3,
8-15 wt. % Al2O3,
2-26 wt. % SiO2,
0-9 wt. % B2O3, and
wherein the weight percentages are based on the total fusible material, and wherein some or all of at least one of the oxides is optionally replaced by a fluoride of the same cation in an amount such that the fusible material comprises at most 5 wt. % of fluorine, based on the total fusible material; and
(c) an organic vehicle, and
wherein the paste composition is lead-free.

### Claim 2 (depends on 1)

The paste composition of claim 1, wherein the fusible material comprises:
60-90 wt. % Bi2O3,
8-12.5 wt. % Al2O3,
2-19 wt. % SiO2, and
0.5-7 wt. % B2O3.

### Claim 3 (depends on 1)

The paste composition of claim 1, wherein the fusible material comprises:
70-90 wt. % Bi2O3,
8-10 wt. % Al2O3,
2-12 wt. % SiO2, and
1-5 wt. % B2O3.

### Claim 4 (depends on 1, 2, 3)

The paste composition of any of claims 1 to 3, wherein the fusible material further comprises at least one of:
0-6 wt. % ZnO,
0-3 wt. % P2O5,
0-5 wt. % Li2O,
0-5 wt. % Na2O,
0-2 wt. % TiO2, or
0-2 wt. % ZrO2.

### Claim 5 (depends on 1)

The paste composition of claim 1, wherein the fusible material comprises 0-2 wt. % Li2O, 0-3 wt. % Na2O, and 0.5-4 wt. % F, with the proviso that the total amount of Li2O and Na2O present is at least 0.5 wt. %.

### Claim 6 (depends on 1)

The paste composition of claim 1, wherein the fusible material consists essentially of:
71-90 wt. % Bi2O3,
8-11 wt. % Al2O3,
2-13 wt. % SiO2, and
1-5 wt. % B2O3.

### Claim 7 (depends on 1)

The paste composition of claim 1, wherein the paste composition is zinc-free.

### Claim 8 (depends on 1)

The paste composition of claim 1, wherein the fusible material comprises 0.5 to 10 wt. % of the total paste composition.

### Claim 9 (depends on 1)

The paste composition of claim 1, wherein the source of the electrically conductive metal is an electrically conductive metal powder.

### Claim 10 (depends on 1)

The paste composition of claim 1, wherein the electrically conductive metal comprises Ag.

### Claim 11 (depends on 10)

The paste composition of claim 10, wherein the Ag comprises 75 to 99.5 wt. % of the solids in the composition.

### Claim 12

A paste composition comprising in admixture:
(a) a source of electrically conductive metal;
(b) a fusible material comprising:
50-90 wt. % Bi2O3,
6.5-15 wt. % Al2O3,
2-8 wt. % SiO2,
0.5-9 wt. % B2O3, and
wherein the weight percentages are based on the total fusible material, and wherein some or all of at least one of the oxides is optionally replaced by a fluoride of the same cation in an amount such that the fusible material comprises at most 5 wt. % of fluorine, based on the total fusible material; and
(c) an organic vehicle, and
wherein the paste composition is lead-free.

### Claim 13 (depends on 12)

The paste composition of claim 12, wherein the fusible material is substantially free of Ni.

### Claim 14 (depends on 12)

The paste composition of claim 12, wherein the fusible material is substantially free of Zn.