Thick film silver paste and its use in the manufacture of semiconductor devices
View Patent ↗The present invention is directed to an electroconductive silver thick film paste composition comprising Ag particles and a Bi—Cu—B—Zn-based glass frit dispersed in an organic medium. The present invention is further directed to an electrode formed from the paste composition and a semiconductor device and, in particular, a solar cell comprising such an electrode. The paste is particularly useful for forming a tabbing electrode.
1. A thick film paste composition comprising:
(a) 35-45 wt % of a conductive phase consisting of spherical silver particles with d 50 <1 μm;
(b) 0.5-6 wt % Pb-free bismuth-copper-boron-zinc-based-oxide glass frit; and
(c) organic medium;
wherein said silver and said glass frit are dispersed in said organic medium and wherein the wt % are based on the total weight of said paste composition, said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit comprising 70-80 wt % Bi 2 O 3 , 5-11 wt % CuO, 3-8 wt % B 2 O 3 and 3-8 wt % ZnO, wherein the oxide wt % are based on the total weight of said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit.
2. The thick film paste composition of claim 1 , said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit further comprising 2-6 wt % SiO 2 and 0.1-1.5 wt % Al 2 O 3 , wherein the oxide wt % are based on the total weight of said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit.
3. A semiconductor device comprising an electrode formed from the paste composition of claim 2 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
4. A solar cell comprising an electrode formed from the paste composition of claim 2 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
5. The solar cell of claim 4 , wherein said electrode is a tabbing electrode on the back side of said solar cell.
6. The thick film paste composition of claim 1 , said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit comprising 72-78 wt % Bi 2 O 3 , 7-11 wt % CuO, 3-8 wt % B 2 O 3 and 3-8 wt % ZnO, wherein the oxide wt% are based on the total weight of said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit.
7. A semiconductor device comprising an electrode formed from the paste composition of claim 6 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
8. A solar cell comprising an electrode formed from the paste composition of claim 6 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
9. The solar cell of claim 8 , wherein said electrode is a tabbing electrode on the back side of said solar cell.
10. The thick film paste composition of claim 6 , said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit further comprising 3-5 wt % SiO 2 and 0.5-1.5 wt % Al 2 O 3 , wherein the oxide wt % are based on the total weight of said Pb-free bismuth-copper-boron-zinc-based-oxide glass frit.
11. A semiconductor device comprising an electrode formed from the paste composition of claim 10 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
12. A solar cell comprising an electrode formed from the paste composition of claim 10 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
13. The solar cell of claim 12 , wherein said electrode is a tabbing electrode on the back side of said solar cell.
14. A semiconductor device comprising an electrode formed from the paste composition of claim 1 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
15. A solar cell comprising an electrode formed from the paste composition of claim 1 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
16. The solar cell of claim 15 , wherein said electrode is a tabbing electrode on the back side of said solar cell.