Method of improving electrical connections in circuitized substrates
View Patent ↗A method of improving conductive paste connections in a circuitized substrate in which at least one and preferably a series of high voltage pulses are applied across the paste and at least one and preferably a series of high current pulses are applied, both series of pulses applied separately. The result is an increase in the number of conductive paths through the paste connections from those present prior to the pulse applications and a corresponding resistance reduction in said connections.
1. A method of improving an electrical connection within a circuitized substrate wherein said electrical connection includes conductive paste as a conductive medium, said method comprising:
applying at least one high voltage pulse, of from about one hundred volts to about one thousand volts given a resistance exceeding fifty ohms, across said conductive paste of said electrical connection; and
applying at least one high current pulse, of from about one amp to about ten amps, across said conductive paste of said electrical connection, said high voltage and high current pulses being applied separately.
2. The method of claim 1 , wherein said at least one high voltage pulse is applied prior to said applying said at least one high current pulse.
3. The method of claim 1 , wherein said at least one high voltage pulse is applied for a time period less than the time period said at least one high current pulse is applied.
4. The method of claim 3 , wherein said time period for applying said at least one high voltage pulse is from about ten milliseconds to about one-thousand milliseconds and said time period for applying said at least one high current pulse is from about five-hundred milliseconds to about one-thousand milliseconds.
5. The method of claim 1 , wherein the amperage of said at least one high voltage pulse is less than the amperage of said at least one high current pulse.
6. The method of claim 5 , wherein said amperage of said at least one high voltage pulse is from about 0.001 amps to about 0.02 amps.
7. The method of claim 1 , wherein the voltage of said at least one high current pulse is lower than the voltage of said at least one high voltage pulse.
8. The method of claim 7 , wherein said voltage of said at least one high current pulse is from about one volt to about thirty volts.
9. The method of claim 1 , wherein said at least one high voltage pulse causes arcs to form between at least some of said conductive paste particles sufficiently to form more conductive paths through said conductive paste than were present prior to said applying of said at least one high voltage pulse.
10. The method of claim 9 , wherein said at least one high current pulse heats said conductive paste sufficiently to form more conductive paths through said conductive paste than were formed following said application of said at least one high voltage pulse.
11. The method of claim 1 , wherein said applying of said at least one high current pulse across said conductive paste of said electrical connection occurs following said applying of said at least one high voltage pulse across said conductive paste and is sufficient to heat said conductive paste so as to cause said conductive paste to form a liquidus ball.
12. The method of claim 1 , wherein the number of said high voltage pulses is from one to about one hundred.
13. The method of claim 1 , wherein the number of said high current pulses is from about one-hundred to about five-hundred.
14. The method of claim 1 , wherein said conductive paste includes metallic particles as part thereof.
15. The method of claim 14 , wherein said applying of said at least one high voltage pulse does not result in the sintering of said metallic particles of said conductive paste and said applying of said high current pulse does result in the sintering of at least some of said particles.
16. The method of claim 15 , wherein said at least some of said metallic particles which are sintered from said applying of said high current pulse are silver particles.