Electrically conductive compositions and methods for the preparation and use thereof

• US 5,376,403 A
• Filed: 10/01/1991
• Issued: 12/27/1994
• Est. Priority Date: 02/09/1990
• Status: Expired due to Term

• Current Assignee: Ormet Circuits, Inc. (Merck & Co., Inc.), Sun Western Investment Fund III
• Original Assignee: Toranaga Technologies, Inc.
• Inventors: Manesis, Nicholas J., Todd, Michael G., Craig, Hugh P., Capote, Miguel A.
• Primary Examiner(s): LUSIGNAN, MICHAEL R
• Application Number:
  US07/769,892
• Time in Patent Office: 1,183 Days
• Field of Search: 427/96, 252/512-514, 252/518, 148/24, 148/25
• US Class Current: 427/98.4
• CPC Class Codes: B22F 3/1035 Liquid phase sintering
• CPC Class Codes: B23K 35/0222 for use in soldering, brazing B23K35/0205 takes precedence
• CPC Class Codes: B23K 35/36 Selection of non-metallic compositions, e.g. coatings, fluxes B23K35/34 takes precedence; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest selection of soldering or welding materials proper B23K35/24
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01L 2224/293 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 23/49827 Via connections through the substrates, e.g. pins going through the substrate, coaxial cables H01L23/49822, H01L23/49833, H01L23/4985, H01L23/49861 take precedence
• CPC Class Codes: H01L 23/49883 the conductive materials containing organic materials or pastes, e.g. for thick films for printed circuits H05K1/092
• CPC Class Codes: H01L 23/5384 Conductive vias through the substrate with or without pins, e.g. buried coaxial conductors H01L23/5383, H01L23/5385 take precedence; pins attached to insulating substrates H01L23/49811
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01068 Erbium [Er]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01087 Francium [Fr]
• CPC Class Codes: H05K 1/095 for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: H05K 1/181 associated with surface mounted components
• CPC Class Codes: H05K 2201/0272 Mixed conductive particles, i.e. using different conductive particles, e.g. differing in shape
• CPC Class Codes: H05K 2201/10378 Interposers
• CPC Class Codes: H05K 2203/0425 Solder powder or solder coated metal powder
• CPC Class Codes: H05K 2203/1105 Heating or thermal processing not related to soldering, firing, curing or laminating, e.g. for shaping the substrate or during finish plating
• CPC Class Codes: H05K 3/1216 by screen printing or stencil printing
• CPC Class Codes: H05K 3/321 by conductive adhesives
• CPC Class Codes: H05K 3/3489 : Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces
• CPC Class Codes: H05K 3/4069 : for via connections in organic insulating substrates
• CPC Class Codes: H05K 3/4623 : the circuit boards having internal via connections between two or more circuit layers before lamination, e.g. double-sided circuit boards H05K3/462 takes precedence
• CPC Class Codes: H05K 3/4664 : Adding a circuit layer by thick film methods, e.g. printing techniques or by other techniques for making conductive patterns by using pastes, inks or powders H05K3/4647 takes precedence

Abstract

Electrically conductive adhesive compositions and methods for the preparation and use thereof, in which a solder powder, a chemically protected cross-linking agent with fluxing properties and a reactive monomer or polymer are the principal components. Depending upon the intended end use, the compositions comprise three or more of the following: a relatively high melting metal powder; solder powder; the active cross-linking agent which also serves as a fluxing agent; a resin; and a reactive monomer or polymer. The compositions are useful as improved conductive adhesives, such as for attaching electrical components to electrical circuits: the compositions comprising metal powder are ideally suited for creating the conductive paths on printed circuits. The compositions for forming conductive paths may first be applied to a substrate in the desired pattern of an electrical circuit, and then heated to cure it. During heating, the action of the cross-linking agent and optional reactive monomer or polymer within the mixture fluxes the metals, enabling sintering to occur between the metal powder and the solder powder.

Claims

1. A method for preparing a printed circuit, comprising:

applying a conductive ink composition comprising a solder powder, a high melting metal powder, and a cross-linking agent mixture comprising a chemically protected cross-linking agent with fluxing properties onto a substrate in a desired pattern to provide a patterned substrate;

rapidly heating the patterned substrate to a temperature at or near the melting point of the solder powder for a period of time sufficient to activate the chemically protected cross-linking agent, whereby the chemically-protected cross-linking agent reacts with the high melting metal powder; and

heating the patterned substrate to a temperature and for a period of time sufficient to cure the composition, wherein the high melting metal powder is selected from the group consisting of copper, silver, aluminum, gold, platinum, palladium, beryllium, rhodium, nickel, cobalt, iron, molybdenum and alloys thereof, the solder powder is selected from the group consisting of Sn, Bi, Pb, Cd, Zn, Ca, In, Te, Hg, TI, Sb, Se, Po, alloys thereof and other metals having a melting point lower than that of the high melting metal powder, and the composition comprises 6-29% by volume of the solder powder, 13-38% by volume of the high melting metal powder, 0-15% by volume of the resin, 30-52% by volume of the cross-linking agent mixture and 0-32% by volume of the reactive monomer or polymer.

2. A method according to claim 1, wherein the pattern is screen-printed onto the substrate.

3. A method according to claim 1, wherein said chemically protected cross-linking agent with fluxing properties is an acid or a strong base which is protected so as to become reactive only at or near a time at which the solder powder is melted.

4. A method according to claim 3, wherein said acid or strong base is selected from the group consisting of anhydrides, carboxylic acids, amides, imides, amines, alcohols, phenols, aldehydes, ketones, nitro compounds, nitriles, carbamates, isocyanates, amino acids, peptides, thiols, sulfonamides, semicarbazones, oximes, hydrazones, cyanohydrins, ureas, phosphoric acids, phosphoric esters, thiophosphoric acids, thiophosphoric esters, phosphonic acids, phosphoric esters, phosphites, phosphonamides, sulfonic acids and sulfonic esters.

5. A method according to claim 3, wherein said acid or strong base is protected by a protecting group selected from the group consisting of carboxylic acids, amides, alcohols, alkyl halides, acid halides, thiols, ureas, alkyl silanes, diazoalkanes, azomethanes, acetals, ketals and transition metal complexes.

6. A method according to claim 3, wherein said acid or strong base is protected by encapsulating the cross-linking agent in a shell of non-reactive material which releases the cross-linking agent only at or near the time the solder powder is melted.