Electromagnetic field assisted self-assembly with formation of electrical contacts

• US 9,137,935 B2
• Filed: 09/26/2014
• Issued: 09/15/2015
• Est. Priority Date: 02/06/2012
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Morris, Christopher James
• Primary Examiner(s): STONER, KILEY SHAWN
• Application Number:
  US14/497,377
• Publication Number:
  US 20150048148A1
• Time in Patent Office: 354 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 1/20 Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating preparation of surfaces in particular ways, see the relevant classes for the treatments or the materials treated, e.g. C04B, C23C
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05647 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/81002 being a removable or sacrificial coating
• CPC Class Codes: H01L 2224/81085 being a liquid, e.g. for fluidic self-assembly
• CPC Class Codes: H01L 2224/81143 Passive alignment, i.e. self alignment, e.g. using surface energy, chemical reactions, thermal equilibrium
• CPC Class Codes: H01L 2224/81444 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/81447 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/81455 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/95001 involving a temporary auxiliary member not forming part of the bonding apparatus, e.g. removable or sacrificial coating, film or substrate
• CPC Class Codes: H01L 2224/95085 being a liquid, e.g. for fluidic self-assembly
• CPC Class Codes: H01L 2224/95133 by applying an electromagnetic field
• CPC Class Codes: H01L 2224/95146 by surface tension
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/13 of an individual bump connector
• CPC Class Codes: H01L 24/81 : using a bump connector
• CPC Class Codes: H01L 24/95 : at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01083 : Bismuth [Bi]
• CPC Class Codes: H01L 2924/0132 : Binary Alloys
• CPC Class Codes: H01L 2924/10156 : at the periphery
• CPC Class Codes: H01L 2924/15788 : Glasses, e.g. amorphous oxides, nitrides or fluorides
• CPC Class Codes: H05K 13/0015 : Orientation; Alignment; Positioning
• CPC Class Codes: H05K 13/027 : Fluid transport of components
• CPC Class Codes: H05K 13/04 : Mounting of components , e.g. of leadless components
• CPC Class Codes: H05K 2201/083 : Magnetic materials
• CPC Class Codes: H05K 2203/04 : Soldering or other types of metallurgic bonding using molten metal H05K2203/128
• CPC Class Codes: H05K 2203/048 : Self-alignment during soldering; Terminals, pads or shape of solder adapted therefor
• CPC Class Codes: H05K 2203/0776 : Uses of liquids not otherwise provided for in H05K2203/0759 - H05K2203/0773
• CPC Class Codes: H05K 2203/104 : Using magnetic force, e.g. to align particles or for a temporary connection during processing
• CPC Class Codes: H05K 3/303 : Surface mounted components, e.g. affixing before soldering, aligning means, spacing means H05K3/32 takes precedence
• CPC Class Codes: H05K 3/3436 : having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

A method and apparatus for self-assembling a part on a substrate are disclosed herein. In some embodiments, a method includes placing a substrate having a first binding site capable of generating a first magnetic field and having a first shaped surface with a first droplet conformably disposed thereon into a first fluid; placing a part having a second binding site capable of generating a second magnetic field and having a second shaped surface with a second droplet conformably disposed on the second shaped surface into the first fluid; and attracting the part towards the first binding site such that an equilibrium is formed between an attractive force and a repulsive force such that the part is free to rotate about the first binding site to minimize the repulsive force when the first and second shaped surfaces rotate into an alignment causing the part to aligned with the first binding site.

Claims

1. A method of self-assembling a part on a substrate, comprising:

placing a substrate into a first fluid, the substrate including a first binding site capable of generating a first electromagnetic field and having a first shaped surface with a first droplet conformably disposed on the first shaped surface, wherein the first droplet is immiscible in the first fluid;

placing a part into the first fluid, the part having a second binding site capable of generating a second electromagnetic field and having a second shaped surface with a second droplet conformably disposed on the second shaped surface, wherein the second droplet is immiscible in the first fluid; and

attracting the part towards the first binding site using the first and second electromagnetic fields such that the first and second droplets solubilize with each other forming an equilibrium between an attractive force between the first and second electromagnetic fields and a repulsive force between the solubilized first and second droplets and the first fluid such that the part is free to rotate about the first binding site to minimize the repulsive force by minimizing an exposed surface area of the solubilized first and second droplets with respect to the first fluid when the first and second shaped surfaces rotate into an alignment causing the part to align with the first binding site.

2. The method of claim 1, further comprising:

placing the substrate into a second fluid prior to placing the substrate into the first fluid, wherein the second fluid is immiscible in the first fluid and wherein the second fluid wets the first shaped surface to form the first droplet on the first shaped surface.

3. The method of claim 2, wherein the second fluid is disposed above the first fluid and wherein the substrate is passed through the second fluid to enter the first fluid.

4. The method of claim 2, wherein the first shaped surface includes a self-assembled monolayer that causes the second fluid to wet the first shaped surface.

5. The method of claim 4, wherein the self-assembled monolayer comprises a plurality of molecules, each molecule including a hydrophobic group that contacts the second fluid.

6. The method of claim 1, further comprising:

placing the part into a second fluid prior to placing the part into the first fluid, wherein the second fluid is immiscible in the first fluid and wherein the second fluid wets the second shaped surface to form the second droplet on the second shaped surface.

7. The method of claim 6, wherein the second fluid is disposed above the first fluid and wherein the part is passed through the second fluid to enter the first fluid.

8. The method of claim 6, wherein the second shaped surface include a self-assembled monolayer that causes the second fluid to wet the second shaped surface.

9. The method of claim 8, wherein the self-assembled monolayer comprises a plurality of molecules, each molecule including a hydrophobic group that contacts the second fluid.

10. The method of claim 1, wherein the first and second droplets comprise a second fluid, and further comprising:

dissolving the solubilized first and second droplets in a third fluid added to the first fluid after the part is aligned, wherein the third fluid is soluble in both the first and second fluids.

11. The method of claim 10, further comprises:

contacting a plurality of solder layers disposed about the first binding site with corresponding plurality of second metal layers disposed about the second binding site by dissolving the solubilized first and second droplets.

12. The method of claim 11, wherein the plurality of solder layers are disposed on a plurality of first metal layers disposed about the first binding site.

13. The method of claim 11, further comprising:

removing the substrate including the aligned part from the first fluid; and

heating the substrate to melt the solder layers such that an electrical connection is formed between the plurality of second metal layers and a corresponding plurality of first metal layers disposed about the first binding site on the substrate.

14. The method of claim 11, further comprising:

exchanging the first fluid with a fourth fluid having a higher boiling point than the first fluid; and

heating the substrate in the fourth fluid to melt the solder layers such that an electrical connection is formed between the plurality of second metal layers and a corresponding plurality of first metal layers disposed about the first binding site on the substrate.

16. The method of claim 1, further comprising:

generating the second electromagnetic field using one or more of a polarized permanent magnet, a hard magnet, a polarized permanent electrostatic material, or a material which is highly permeable to the electromagnetic field lines emanating from the first electromagnetic field generator.

15. The method of 1, further comprising:

generating the first electromagnetic field using one or more of a polarized permanent magnet, a hard magnet, a polarized permanent electrostatic material, an electrode providing an electro static field, or an electromagnet.