Methods and apparatus to reduce growth formations on plated conductive leads
View Patent ↗A process includes annealing one or more plated conductive leads at a predetermined temperature. The one or more plated conductive leads are plated with one or more layers, where each layer comprises a material. The predetermined temperature is greater than or equal to approximately a melting point of one of the materials. The annealing can reduce growth formations, such as whiskers, on the one or more conductive leads. Lead frames and other devices having plated conductive leads may be subjected to the process, and the resultant plated conductive leads will have fewer growth formations than plated conductive leads not subjected to the process. The plated conductive leads may be trimmed and formed prior to or after the anneal.
1. A method for reducing growth formations on one or more plated conductive leads, the method comprising the step of annealing the one or more plated conductive leads at a predetermined temperature, the one or more plated conductive leads plated with one or more layers, each layer comprising a material, the predetermined temperature greater than or equal to approximately a melting point of one of the materials, wherein said annealing step reduces growth formations in comparison to a solder reflow process.
2. The method of claim 1 , further comprising one or more steps of plating one or more conductive leads comprising a core with each of the one or more materials to create the plated one or more conductive leads.
3. The method of claim 2 , further comprising the steps of trimming and forming the plated conductive leads, wherein the steps of trimming and forming occur before or after the one or more steps of plating and before or after the step of annealing.
4. The method of claim 1 , wherein the step of annealing comprises the step of reflowing the one or more plated conductive leads at at least at the predetermined temperature to attach the one or more plated conductive leads to a circuit board.
5. The method of claim 1 , further comprising the step of reflowing the one or more plated conductive leads to attach the one or more plated conductive leads to a circuit board.
6. Ihe method of claim 1 , wherein:
the one or more conductive leads comprise a core comprising copper;
the one or more layers comprise a finish comprising tin; and
the predetermined temperature is greater than or equal to approximately a melting point of the finish.
7. The method of claim 6 , wherein:
the one or more conductive leads comprise a core consisting essentially of copper; and
the one or more layers comprise a finish consisting essentially of tin.
8. The method of claim 6 , wherein the finish is between 3 to 25 micrometers in thickness.
9. The method of claim 7 , wherein the finish is between 10 to 25 micrometers in thickness.
10. The method of claim 6 , wherein the predetermined temperature is greater than or equal to approximately a melting point of tin.
11. The method of claim 10 , wherein the predetermined temperature is less than or equal to approximately 260 degrees centigrade.
12. The method of claim 6 , further comprising the step of plating the core with a material comprising tin to create the finish.
13. The method of claim 1 , wherein:
the one or more layers comprise an underplate and a finish, the underplate comprises nickel, and the finish comprises tin; and
the one or more plated conductive leads comprise a core comprising copper; and
the predetermined temperature is greater than or equal to approximately a melting point of the finish.
14. The method of claim 13 , wherein:
the one or more conductive leads comprise a core consisting essentially of copper; and
the one or more layers comprise an underplate consisting essentially of nickel and a finish consisting essentially of tin.
15. The method of claim 13 , wherein the underplate has a thickness between 0.3 and three micrometers.
16. The method of claim 13 , further comprising the steps of:
plating the core with a material comprising nickel to create the underplate; and
plating the underplate with a material comprising tin to create the finish.
17. The method of claim 13 , wherein the step of annealing is performed for a predetermined time, wherein the predetermined time is at least one second and is less than a time determined to ensure that all of the nickel is not consumed during the anneal step.
18. The method of claim 1 , wherein step of annealing is performed for at least one second.
19. The method of claim 1 , wherein:
the one or more conductive leads comprise a core comprising copper;
the one or more layers comprise an underplate comprising silver and a finish comprising tin; and
the predetermined temperature is greater than or equal to approximately a melting point of the finish.
20. The method of claim 1 , wherein:
the one or more layers comprise a finish comprising one or more of indium, cadmium, zinc, antimony, lead, iron, nickel, gold, silver, and palladium; and
the predetermined temperature is greater than or equal to approximately a melting point of the finish.
21. The method of claim 1 , wherein the one or more conductive leads comprise a core comprising one or more of copper, copper alloy and alloy 342 .
22. An apparatus comprising one or more plated conductive leads and made by a process comprising the step of annealing at least the one or more plated conductive leads at a predetermined temperature, the one or more plated conductive leads plated with one or more layers, each layer comprising a material, the predetermined temperature greater than or equal to approximately a melting point of one of the materials, wherein said annealing step reduces growth formations in comparison to a solder reflow process.
23. The apparatus of claim 22 , wherein:
the one or more plated conductive leads are a plurality of plated conductive leads;
the apparatus comprises a package; and
the plurality of plated conductive leads are part of the package.
24. The apparatus of claim 23 , wherein the apparatus further comprises a circuit board coupled to the plurality of plated conductive leads.
25. The apparatus of claim 22 , wherein the apparatus comprises an integrated circuit coupled to the one or more plated conductive leads.
26. An integrated circuit comprising one or more plated conductive leads plated with one or more layers, wherein the one or more conductive leads have been annealed at a predetermined temperature greater than or equal to a melting point of one of the one or more layers, wherein said annealing step reduces growth formations in comparison to a solder reflow process.