Claims
- 1. A ternary solder alloy which is lead free, of high strength and particularly well suited for microelectronic applications consisting essentially of tin, silver and bismuth with tin in a major proportion, bismuth in excess of 5 wt % and up to 25 wt % and silver in a range from about 2 wt % to less than 5% silver.
- 2. A ternary solder alloy as defined in claim 1 consisting essentially of tin in a range from about 70 wt % to less than 91 wt %, bismuth in a range from about 5 wt % to 25 wt % and silver in a range from 2 wt % to 5 wt %.
- 3. A ternary solder alloy as defined in claim 2 consisting essentially of about 6.1 wt % bismuth, 3.1 wt % silver balance tin.
- 4. A ternary solder alloy as defined in claim 2 consisting essentially of about 10-1 5 wt % bismuth, 3.3-3.5 wt % silver, balance tin and having a controlled liquidus temperature of between about 191° C. -201° C.
- 5. A microelectronic structure comprising at least two microelectronic components joined by means of a solder alloy with the solder alloy consisting essentially of tin, silver and bimuth with tin in a major proportion, bismuth in excess of 5 wt % and up to 25 wt % and silver in a range from about 2 wt % to less than 5 wt %.
- 6. A microelectronic structure as defined in claim 5 wherein said solder alloy consists essentially of from about 70 to less than 91 weight percent tin, from about 5 wt % to 25 wt % bismuth and from 2 wt % to 5 wt % silver.
- 7. A microelectronic structure as defined in claim 5 wherein said microelectronic components are selected from the group consisting of: chip carriers, IC chips and circuit boards.
- 8. A method of joining at least two microelectronic components to one another comprising the steps of connecting the components to be joined with a ternary solder alloy consisting essentially of a major proportion of tin, between about 5 to 25 wt % bismuth and 2 to 5 wt % silver.
- 9. A method as defined in claim 8 wherein said solder alloy consists essentially of from about 70 to less than 91 weight percent tin, from about 5 to 25 wt % bismuth and from 2 to.5 wt % silver.
- 10. A method as defined in claim 8 wherein said solder alloy consists essentially of about 10-1 5 wt % bismuth, 3.3-3.5 wt % silver, balance tin.
- 11. A solder paste comprising a flux, an organic vehicle and particles of metal having a composition consisting essentially of a major proportion by weight of tin, between about 5 to 25 wt % bismuth and from 2 to 5 wt % silver.
- 12. A solder paste as defined in claim 11 wherein said composition consists essentially of from about 70 to less than 91 weight percent tin, from about 5 to 25 wt % bismuth and from 2 to 5 wt % silver.
- 13. A process for producing circuit boards, comprising the steps of:
producing plated through holes in a circuit board; inserting the pins of pin-in-hole components into the plated through holes; producing a stationary wave of liquid solder consisting essentially of a major proportion of tin, between about 5 to 25 wt % bismuth and from 2 to 5 wt % silver; moving the circuit board across the wave with the bottom of the circuit board in contact with the wave, thereby substantially filling the plated through holes with solder; and cooling the circuit board to form solid solder joints.
- 14. A process for producing circuit boards comprising the steps of:
producing a substrate with multiple wiring layers including exposed metal pads on a surface; forming a solder paste comprising a flux, an organic vehicle and particles of metal consisting essentially of a major proportion of tin, bismuth in excess of 5 wt % and up to 25 wt % and from 2 to 5 wt % silver; depositing the solder paste upon said substrate; placing terminals of a surface mount component onto corresponding pads of the substrate; heating said solder paste to a temperature sufficient to reflow the solder paste to conned the component with the substrate; and cooling to solidify the connections.
FIELD OF THE INVENTION
[0001] The present invention is a continuation-in-part of U.S. patent application Ser. No. 08/768,878 filed Dec. 17, 1996 and relates to a high strength, lead-free, low toxicity, ternary solder alloy that is particularly useful in microelectronic applications.
Provisional Applications (1)
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Number |
Date |
Country |
|
60019591 |
Jun 1996 |
US |
Divisions (1)
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Number |
Date |
Country |
Parent |
09216042 |
Dec 1998 |
US |
Child |
09771240 |
Jan 2001 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
08768878 |
Dec 1996 |
US |
Child |
09216042 |
Dec 1998 |
US |