Adhesive and encapsulating material with fluxing properties
View Patent ↗The attachment of an electrical component to an electrical termination on a component-carrying substrate by a solder bump technique of a thermally curable adhesive composition for encapsulating purposes is described which comprises a thermosetting polymer and a chemical cross-linking agent which has fluxing properties but which is unreactive or of severely restricted reactivity with the polymer without the action of heat and/or catalyst. The composition is to be thermally curable when heated to soldering temperatures in a reaction which is catalyzable merely by metal oxide fluxed from metal surfaces by cross-linking agent then dissolved in the thermosetting polymer.
1. A thermally curable adhesive composition, comprising:
(A) a compound selected from the group consisting of (i) a thermosetting polymer and (ii) a monomer which is polymerizable to yield a thermosetting polymer, wherein the thermosetting polymer (i) and the thermosetting polymer yielded by polymerization of the monomer (ii) are crosslinkable when subject to a chemical crosslinking agent; and
(B) a chemical crosslinking agent selected from the group consisting of (i) polyacids, (ii) polyanhydrides, and (iii) hydrazides, wherein the crosslinking agent has fluxing properties, is a solid at ambient temperature and is insoluble in the thermally curable adhesive composition until heated to a soldering temperature; and wherein the composition is thermally curable when heated to the soldering temperatures.
2. The composition according to claim 1 , wherein the polyacid is selected from the group consisting of polymers containing two or more carboxyl groups and di- and polycarboxylic acids.
3. The composition according to claim 2 , wherein the polycarboxylic acid is a C 8 or greater dicarboxylic acid.
4. The composition according to claim 1 , wherein the hydrazide is a monohydrazide or a dihydrazide or a polyfunctional hydrazide.
5. The composition according to claim 1 , wherein the crosslinking agent contains a dihydrazide or a dicarboxylic acid or a mixture of a dihydrazide and a dicarboxylic acid.
6. The composition according to claim 5 , wherein the crosslinking agent contains adipic dihydrazide or dodecanedioic acid or a mixture of adipic dihydrazide and dodecanedioic acid.
7. The composition according to claim 1 , wherein the polyanhydride is either polyazelaic anhydride or polyadipic anhydride.
8. The composition according to claim 1 , further comprising an acid flux which is liquid at temperatures below 100° C. and which fluxes metals so as to create metallic salt.
9. The composition according to claim 8 , wherein the acid flux is liquid at temperatures from 20° C. to 25° C.
10. The composition according to claim 8 , wherein the acid flux is a monocarboxylic acid.
11. The composition according to claim 10 , wherein the acid flux is selected from the group consisting of a versatic acid, capric acid, caprylic acid, lauric acid, stearic acid and palmitic acid.
12. A method of producing an electronic device, the method comprising:
opposing an electrical component having a plurality of electrical terminations, each termination including a solder bump, and a component-carrying substrate having a plurality of electrical terminations corresponding to the terminations of the electrical component;
applying a thermally curable adhesive composition to a metal surface on at least one of the electrical component and the substrate;
bringing the electrical component and the substrate into contact at elevated temperature so as to solder the electrical component to the substrate while simultaneously achieving encapsulation of the electrical component and the substrate in the adhesive composition, wherein the thermally curable adhesive composition comprises
(A) a compound selected from the group consisting of (i) a thermosetting polymer, and (ii) a monomer which is polymerizable to yield a thermosetting polymer, wherein the thermosetting polymer (i) and the thermosetting polymer yielded by polymerization of the monomer (ii) are crosslinkable when subject to the action of a chemical crosslinking agent; and
(B) a chemical crosslinking agent selected from the group consisting of (i) polyacids, (ii) polyanhydrides, and (iii) hydrazides, wherein the crosslinking agent has fluxing properties, is a solid at ambient temperature, and is insoluble in the thermally curable adhesive composition until heated to a soldering temperature; and wherein the composition is thermally curable when heated to the soldering temperatures.