Conductive paste

• US 4,398,975 A
• Filed: 12/16/1981
• Issued: 08/16/1983
• Est. Priority Date: 12/25/1980
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ohsawa, Masayuki, Ito, Takao, Ohsawa, Kenji, Kurata, Keiji, Tanno, Koichiro
• Primary Examiner(s): Lewis, Michael L.
• Application Number:
  US06/331,229
• Time in Patent Office: 608 Days
• Field of Search: 75/134 T, 148/3, 148/400, 420/555
• US Class Current: 148/400
• CPC Class Codes: C22C 28/00 Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
• CPC Class Codes: H01B 1/02 mainly consisting of metals or alloys
• CPC Class Codes: H01R 4/58 characterised by the form or material of the contacting members H01R4/01 takes precedence
• CPC Class Codes: H05K 2201/0215 Metallic fillers
• CPC Class Codes: H05K 2201/0305 Solder used for other purposes than connections between PCB or components, e.g. for filling vias or for programmable patterns
• CPC Class Codes: H05K 2201/09845 Stepped hole, via, edge, bump or conductor
• CPC Class Codes: H05K 3/3463 Solder compositions in relation to features of the printed circuit board or the mounting process
• CPC Class Codes: H05K 3/3485 Applying solder paste, slurry or powder thick film methods for applying conductive paste or ink patterns H05K3/12
• CPC Class Codes: H05K 3/4038 Through-connections; Vertical interconnect access [VIA] connections H05K3/403, H05K3/42 take precedence
• CPC Class Codes: H05K 3/4644 by building the multilayer layer by layer, i.e. build-up multilayer circuits making via holes in the insulating layers H05K3/0011; special circuit boards as base or core whereon the multilayer is built H05K3/4602

Abstract

A novel conductive paste and a method of making the same in which metallic gallium is combined with a metal or alloy which forms a eutectic with gallium in an amount in excess of its limit of solubility in gallium at a specific temperature. This melt is then treated with a metal powder of a second metal or alloy which alloys with gallium to produce a higher melting alloy, the second metal powder being coated on its surface with the eutectic-forming metal.

Claims

1. A conductive paste comprising:

a continuous phase of metallic gallium in combination with a first metal which forms a eutectic with gallium, said metal being present in excess of its solubility limit in gallium at a predetermined temperature,

in combination with a second metal powder capable of alloying with gallium, said powder being pre-coated with said first metal and being dispersed through said continuous phase.

2. A conductive paste according to claim 1 in which:

said first metal includes indium, tin, zinc, or bismuth, or an alloy thereof.

3. A conductive paste according to claim 1 in which said second metal is copper, nickel, cobalt, gold, or an alloy of such metal.

4. A conductive paste according to claim 2 which contains about 10% by weight tin.

5. A conductive paste according to claim 2 which contains about 6% by weight zinc.

6. A conductive paste according to claim 2 which contains about 20% by weight indium.

7. A conductive paste according to claim 1 in which:

said metal powder has a size of from 0.5 to 500 microns.

8. A conductive paste according to claim 1 in which:

said metal powder has a size of about l0 to l00 microns.

9. A method for making a conductive composition which comprises:

providing a molten mixture of gallium and a first metal which forms a eutectic with gallium at a temperature in excess of the melting point of said metal,

cooling the resulting melt to a lower temperature,

adding to the cooled melt a powder having a central core of a second metal or alloy capable of alloying with gallium to form a gallium alloy of a higher melting point than the gallium itself, said core being pre-coated with said first metal, and

agitating the resulting mixture to disperse said powder within said melt.

10. A method according to claim 9 in which said first metal includes indium, tin, zinc or bismuth.