Solderable conductive compositions that are capable of being soldered by non silver-bearing solder and that can be bonded directly to substrates and which are flexible

• US 4,595,605 A
• Filed: 07/18/1984
• Issued: 06/17/1986
• Est. Priority Date: 07/18/1984
• Status: Expired due to Fees

• Current Assignee: National Starch and Chemical Investment Holding Corporation
• Original Assignee: Rohm and Haas Company (Dow, Inc.)
• Inventors: Shahbazi, Samson, Martin, Frank W.
• Primary Examiner(s): BARR, JOSEPHINE
• Application Number:
  US06/631,972
• Time in Patent Office: 699 Days
• Field of Search: 252/514, 524/439, 524/440, 428/901, 427/96, 427/282, 427/393.5, 427/393.6
• US Class Current: 427/98.4
• CPC Class Codes: C04B 2111/00844 for electronic applications
• CPC Class Codes: C04B 35/00 Shaped ceramic products characterised by their composition porous ceramic products C04B38/00; ceramic articles characterised by particular shape, see the relevant classes, e.g. linings for casting ladles, tundishes, cups or the like B22D41/02; ceramic substrates for microelectronic semi-conductors H01L23/15; Ceramics compositions containing free metal bonded to carbides, diamond, oxides, borides, nitrides, silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides or sulfides other than as macroscopic reinforcing agents C22C; shaping of ceramics B28B; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products chemical preparation of powders of inorganic compounds C01; infiltration of sintered ceramic preforms with molten metal C04B41/51
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/4838 Halogenated polymers
• CPC Class Codes: C04B 41/5116 Ag or Au
• CPC Class Codes: C04B 41/88 Metals
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H05K 1/095 for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: Y10S 428/901 Printed circuit

Abstract

This invention provides conductive compositions that are solderable and flexible and that can be bonded directly to substrates. These compositions are made up of a combination of silver exclusively in the form of flake and vinyl chloride/vinyl acetate copolymer. Also provided is a method of making these compositions. Another embodiment of this invention is a method of applying conductive compositions directly to substrates by bonding the conductive compositions directly to the substrate. Once cured the compositions demonstrate good adhesion directly to the substrate in addition to good conductivity, solderability and flexibility characteristics. Additionally, these compositions are capable of being soldered by non silver-bearing solder.

Claims

1. A directly solderable conductive composition comprising after cure:

(a) from about 88 to about 93% by weight silver, said silver beiing 100% in the form of flake having an average particle size of about 0.5 to about 50 microns; and

(b) from about 7 to about 12% by weight vinyl chloride/-vinyl acetate copolymer, said copolymer having a number average molecular weight from about 14,000 to about 35, 000 and containing no carboxylic acid groups.

2. The composition of claim 1 wherein the weight ratio of vinyl chloride to vinyl acetate is from about 80:

20 to about 90;

10.

3. A method of making a conductive composition that is directly solderable and flexible comprising dissolving from about 5% to about 9% by weight vinyl chloride/-vinyl acetate copolymer in about 20% to about 25% by weight ketone solvent and mixing the resultant solution with about 68% to about 75% by weight silver;

said vinyl chloride/vinyl acetate copolymer having a number average molecular weight from about 14,000 to about 35,000 and containing no carboxylic acid groups, and said silver being 100% in the form of flake having an average particle size of about 0.5 to about 50 microns.

4. The method of claim 3 additionally comprising applying the vinyl chloride/vinyl acetate copolymer, ketone solvent, silver flake mixture to a substrate and then drying and curing the mixture.

5. The method of claim 4 wherein the mixture is applied at a thickness of one mil.

6. The method of claim 4 wherein the mixture is applied to the substrate by silk screening.

7. The method of claim 3 wherein the ketone solvent selected from the group consisting of gamma butyrolactone, acetone, and cyclohexane.

8. The method of claim 4 wherein the substrate is flexible.

9. The method of claim 4 wherein the substrate is a printed circuit board.

10. The method of claim 4 wherein the mixture is dried and cured at a temperature of from about 100°

C. to about 170°

C. for about 15 to about 60 minutes.