Molten solder drop ejector

• US 5,876,615 A
• Filed: 01/02/1997
• Issued: 03/02/1999
• Est. Priority Date: 01/02/1997
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Predetechensky, Mikhail
• Primary Examiner(s): KASTLER, SCOTT R
• Application Number:
  US08/778,085
• Time in Patent Office: 789 Days
• Field of Search: 222/590, 222/591, 222/593, 222/594, 266/236, 266/45, 266/237
• US Class Current: 222/590
• CPC Class Codes: B05B 17/04 operating with special methods
• CPC Class Codes: B05B 5/001 incorporating means for heating or cooling, e.g. the material to be sprayed
• CPC Class Codes: B05B 5/025 Discharge apparatus, e.g. electrostatic spray guns
• CPC Class Codes: B05B 5/1608 the liquid or other fluent material being electrically conductive
• CPC Class Codes: B05B 5/1691 Apparatus to be carried on or by a person or with a container fixed to the discharge device
• CPC Class Codes: B23K 3/0607 Solder feeding devices
• CPC Class Codes: B41J 2202/04 Heads using conductive ink

Abstract

A simple yet highly reliable technique for ejecting a droplet of heated solder, or other liquid conductive material, is described. Small droplets of an electrically-conductive liquid are ejected on-demand from a drop generator operating on a magnetohydrodynamic principle. The drop generator consists of two substantially parallel conductive paths separated by a thin electrically-insulating material. A channel for the conductive liquid contains a drop ejecting orifice, and the conductive liquid in the channel forms a first of these two parallel conductive paths. The other path is either a solid conductor or a second channel filled with the conductive liquid. A current on the order of 10-1000 amperes is pulsed through the two parallel conductive paths, and the interaction of the magnetic fields generated by the electric currents through the parallel paths with these currents forces a droplet of the conductive liquid through the orifice in the first channel. By adjusting the duration and/or magnitude of the pulsed current, the droplet size may be carefully controlled. In the preferred embodiment, the drop generator is in the form of a self-contained replaceable cartridge.

Claims

1. A method for producing a stream or droplet of liquid conductive material comprising the steps of:

providing said liquid conductive material in a first channel in fluid communication with an orifice;

supplying an electric current through said liquid conductive material in said first channel;

supplying an electric current through a conductor proximate to said first channel such that the interaction of magnetic forces generated by said current through said conductor and said current through said liquid conductive material in said first channel forces an amount of said liquid conductive material through said orifices,

wherein said step of supplying an electric current through said conductor comprises supplying a current through said liquid conductive material in a second channel in fluid communication with said first channel.

2. The method of claim 1 wherein said second channel is substantially parallel to said first channel.

3. The method of claim 1 wherein said step of supplying an electric current through said conductor comprises supplying a current through a solid conductor.

4. The method of claim 3 wherein said solid conductor is substantially parallel to said first channel.

5. The method of claim 1 wherein said first channel is located between said orifice and said conductor.

6. The method of claim 1 wherein said orifice is located between said conductor and said first channel.

7. The method of claim 1 further comprising the step of providing a heater proximate to said first channel to maintain said liquid conductive material in a molten state.

8. The method of claim 1 further comprising the step of providing a receptacle for an amount of said liquid conductive material in fluid communication with said first channel, said receptacle having a capacity of between approximately 0.1-25 milliliters.

9. The method of claim 1 wherein said liquid conductive material is selected from the group consisting of metals and metal alloys.

11. The method of claim 9 further comprising the steps of:

providing a first electrode in said first channel and a second electrode in said second channel; and

applying a current between said first electrode and said second electrode to eject a droplet of said liquid conductive material through said orifice.

12. The method of claim 1 wherein said conductor is substantially parallel to said first channel and runs along a side of said first channel opposite to a side of said first channel containing said orifice, wherein said current through said conductor is in a direction opposite to said current through said liquid conductive material in said first channel.

13. The method of claim 1 wherein said conductor is substantially parallel to said first channel and runs along the same side of said first channel which contains said orifice, wherein said current through said conductor is in the same direction as the direction of said current through said liquid conductive material in said first channel.

14. The method of claim 1 wherein said step of providing said liquid conductive material in said first channel further comprises the step of providing a supply of said liquid conductive material in a first chamber in fluid communication with said first channel.

15. The method of claim 14 wherein said chamber has a capacity of less than approximately 25 milliliters.

16. The method of claim 1 wherein said orifice is between approximately 50-200 microns in diameter.

17. The method of claim 1 wherein said step of supplying a current through said conductor and through said liquid conductive material comprises the step of supplying one or more pulses of electric current to said conductor and to said liquid conductive material in said first channel between approximately 10-1000 amperes.

18. The method of claim 1 wherein said step of providing said liquid conductive material in said first channel comprises the step of inserting a replaceable cartridge, containing said liquid conductive material in said first channel, into a receptacle.

10. A method for producing a stream or droplet of liquid conductive material comprising the steps of:

providing said liquid conductive material in a first channel in fluid communication with an orifice;

supplying an electric current through said liquid conductive material in said first channel;

supplying an electric current through a conductor proximate to said first channel such that the interaction of magnetic forces generated by said current through said conductor and said current through said liquid conductive material in said first channel forces an amount of said liquid conductive material through said orifice,

wherein said conductor comprises said liquid conductive material in a second channel in fluid communication with said first channel.

19. A drop ejector comprising:

a supply of liquid conductive material in a first channel, said first channel having an orifice;

at least one first electrode contacting said liquid conductive material in said first channel to conduct an electric current flowing through said liquid conductive material in said first channel;

a conductor situated substantially parallel to said first channel and proximate to said first channel; and

at least one second electrode connected to said conductor to conduct an electric current flowing through said conductor, said conductor, said first channel, and said orifice being arranged such that a sufficient electric current through said conductor and said liquid conductive material in said first channel generates magnetic fields interacting with said electric current which force an amount of said liquid conductive material through said orifices,

wherein said conductor comprises said liquid conductive material in a second channel in fluid communication with said first channel.

20. The ejector of claim 19 wherein said conductor comprises a solid conductor.

21. The ejector of claim 19 wherein said first channel is located between said orifice and said conductor.

22. The ejector of claim 19 wherein said orifice is located between said conductor and said first channel.

23. The ejector of claim 19 further comprising a heater proximate to said first channel to maintain said liquid conductive material in a molten state.

24. The ejector of said claim 19 wherein said ejector is formed as a replaceable cartridge.

25. The ejector of claim 19 further comprising a receptacle for an amount of said liquid conductive material in fluid communication with said first channel, said receptacle having a capacity of between approximately 0.1-25 milliliters.