Sinterable silver flake adhesive for use in electronics
A conductive composition comprises (i) micro- or submicro-sized silver flake having a tap density of 4.6 g/cc or higher and (ii) a solvent that dissolves any fatty acid lubricant or surfactant present on the surface of the silver. In one embodiment, (iii) a small amount of peroxide is present. No organic resin is present in the composition.
1. A conductive composition consisting essentially of:
(i) micro- or submicro-sized silver flake having a tap density of 4.6 g/cc or higher and
(ii) a solvent that dissolves any fatty acid lubricant or surfactant present on the surface of the silver.
2. The conductive composition according to claim 1 in which the silver flake has a tap density of 4.9 g/cc or higher.
3. The conductive composition according to claim 1 in which the silver flake has a tap density of 5.2 g/cc or higher.
4. The conductive composition according to claim 1 in which the solvent is present in an amount less than 15% by weight of the total composition.
5. The conductive composition according to claim 1 in which the solvent is selected from the group consisting of 2-(2-ethoxy-ethoxy)-ethyl acetate, propylene glycol monoethyl ether, butylethoxy ethyl acetate, propylene carbonate, cyclooctanone, cycloheptanone, cyclohexanone, and linear or branched alkanes.
6. A conductive composition comprising
(i) micro- or submicro-sized silver flake having a tap density of 4.6 g/cc or higher,
(ii) a solvent that dissolves any fatty acid lubricant or surfactant present on the surface of the silver, and
(iii) a liquid peroxide.
7. The conductive composition according to claim 6 in which the liquid peroxide is selected from the group consisting of tertiary-butyl peroxy-2-ethylhexanoate, tertiary-butyl peroxyneodecanoate, dilauroyl peroxide, tertiary-butyl peroctoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethyl hexanoate, di-tertiary-butyl peroxide, 2,5-bis-(tertiary-butylperoxy)-2,5-dimethyl hexane, and di-tertiary-amyl peroxide.
8. The conductive composition according to claim 6 in which the liquid peroxide is present in an amount of 0.2 to 0.5% by weight of the total composition.
9. The conductive composition according to claim 6 in which the liquid peroxide is present in an amount of 0.1 to 1.0% by weight of the total composition.
10. The conductive composition according to claim 6 in which the silver flake has a tap density of 4.9 g/cc or higher.
11. The conductive composition according to claim 6 in which the silver flake has a tap density of 5.2 g/cc or higher.
12. The conductive composition according to claim 6 in which the solvent is present in an amount less than 15% by weight of the total composition.
13. The conductive composition according to claim 6 in which the solvent is selected from the group consisting of 2-(2-ethoxy-ethoxy)-ethyl acetate, propylene glycol monoethyl ether, butylethoxy ethyl acetate, propylene carbonate, cyclooctanone, cycloheptanone, cyclohexanone, and linear or branched alkanes.