Fatigue resistant lead-tin eutectic solder
AssigneeHughes Aircraft Company
InventorBoon Wong
Life of this patent
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Abstract
The fatigue resistance of lead-tin eutectic solder is increased by doping the solder with about 0.1 to 0.8 weight % of a dopant selected from cadmium, indium antimony and mixtures thereof. The doped eutectic solder exhibits increased resistance to thermally or mechanically induced cyclic stress and strain. As a result, the fatigue resistance of the solder joint is increased. Combination of dopants, such as indium and cadmium, in combined amounts of less than 0.5 weight % are especially effective in increasing the fatigue resistance of the lead-tin eutectic solder.
Claims20
A lead-tin eutectic solder for use in soldering metal surfaces together consisting of:
- (a) a lead-tin eutectic solder which is free of silver gold and phosphorus;
- and
- (b) about 0.1 to 0.8 weight percent of a dopant consisting of a member selected from the group consisting of a mixture of cadmium and indium, and a mixture of cadmium, indium, and antimony, wherein said solder with said dopant has improved fatigue resistance.
In a method for soldering two metal surfaces together using lead-tin eutectic solder, wherein the improvement consists of:
- (a) providing a first lead-tin eutectic solder which is free of silver, gold and phosphorous;
- and
- (b) doping said first lead-tin eutectic solder which is free of silver, gold, and phosphorous with about 0.1 to 0.8 weight percent of a dopant consisting of a member selected from the group consisting of a mixture of cadmium and indium, and a mixture of cadmium, indium, and antimony, wherein said solder with said dopant provides improved fatigue resistance.
A method for improving the fatigue resistance of a lead-in solder joint comprising forming said solder joint from a composition consisting of:
- (a) lead-tin eutectic solder which is free of silver, gold and phosphorus;
- and
- (b) about 0.1 to 0.8 weight percent of a dopant consisting of a member selected from the group consisting of a mixture of cadmium and indium, and a mixture of cadmium, indium, and antimony.
A solder powder consisting of particles formed from a mixture consisting of:
- (a) a lead-tin eutectic solder which is free of silver, gold and phosphorus;
- and
- (b) about 0.1 to 0.8 weight percent of a dopant consisting of a member selected from the group consisting of mixture of cadmium and indium, and a mixture of cadmium, indium, and antimony, wherein said dopant improves the fatigue resistance of said solder.
A solder paste for use in soldering metal surfaces together, consisting of:
- (a) powder formed from a mixture consisting of:
- (1) a lead-in eutectic solder which is free of silver, gold and phosphorus;
- and
- (2) about 0.1 to 0.8 weight percent of a dopant consisting of a member selected from the group consisting of a mixture of cadmium and indium, and a mixture of cadmium, indium, and antimony;
- and
- (b) solder flux.
Dependencies are inferred from the claim text.