Aqueous acidic tin-lead immersion plating bath containing weak acid and weak base
AssigneeMacDermid, Incorporated
InventorDonald R. Ferrier
Life of this patent
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Abstract
Immersion tin-lead baths are provided, preferably free of hypophosphite ion, comprising a strongly acidic aqueous solution comprised of thiourea, water-soluble sources of divalent tin and lead, a weak acid, and a weak base.
Claims10
An aqueous strongly acidic tin-lead immersion plating bath comprising thiourea, a water-soluble source of divalent tin ion, a water-soluble source of divalent lead ion, a weak acid selected from the group consisting of citric acid, acetic acid, tartaric acid and mixtures thereof, and aqueous ammonia.
An aqueous, strongly acidic, hypophosphite-free tin-lead immersion plating bath, comprising thiourea, a water-soluble source of divalent tin ion, a water-soluble source of divalent lead ion, a weak acid selected from the group consisting of citric acid, acetic acid, tartaric acid and mixtures thereof, and aqueous ammonia.
An aqueous, strongly acidic, hypophosphite-free tin-lead immersion bath, comprising thiourea;
- tin fluoborate;
- lead fluoborate;
- boric acid;
- a weak acid selected from the group consisting of citric acid, acetic acid, tartaric acid, and mixtures thereof;
- and aqueous ammonia.
An aqueous, strongly acidic tin-lead immersion plating bath comprising thiourea, boric acid, a water-soluble source of divalent tin ion, a water-soluble source of divalent lead ion, a weak acid and aqueous ammonia.
Dependencies are inferred from the claim text.