MXPA99005407A - Thermosetting encapsulants for electronics packaging - Google Patents

Abstract

An electronic package is provided wherein a semiconductor device on a substrate is encapsulated with a thermally reworkable encapsulant composition comprising:(a) a thermally reworkable cross-linked resin produced by reacting at least one dienophile having a functionality greater than one and at least one 2,5-dialkyl substituted furan-containing polymer, and (b) at least one filler present from 25 to 75 percent by weight based upon the amount of components (a) and (b). Such a process provides a readily reworkable electronic package.

Description

THERMOSTABLE ENCAPSULANTS FOR ELECTRONIC PACKAGING Field of the Invention This invention relates to thermoset encapsulates. In one aspect. The invention relates to thermoset encapsulates suitable for use in electronic packaging.

Background of the Invention Plate chip technology (COB) involves adhering a semiconductor device onto a substrate by means of an adhesive and encapsulating the entire device and part of the substrate with an encapsulant, commonly an epoxy-based system. The electrically conductive connections can be made from the device so that metallic circuits are traced on the substrate by means of gold, tinned copper or aluminum wires by the bonding of wires or by the automated bonding of the tape. The distribution of the top encapsulant drop was made in one of two ways: "(1) the encapsulant will be distributed over the device and part of the substrate to form a protective layer." Ref: 30392 (2) a thixotropic or low fluidity encapsulant will be distributed over the substrate to form a dam. A low viscosity encapsulant will then be distributed within the dike to protect the device. Historically, higher drop encapsulants were used in inexpensive applications such as digital clocks and video games where reprocessing was not widely used. Recently, they are beginning to see the increased use in higher density applications for more expensive chips and substrates where repair and reprocessing are important uses. For example, in some arrangement in the form of a spherical grid (BGA) and an array in the form of a needle grid (PGA), liquid encapsulants are used to protect the chip as a package of COB while holding or holding the balls being used for make the connection between the chip substrate and the printed circuit board. In addition, the package may consist of multiple chips arranged close together on a common substratum. Higher droplet encapsulants are also found for use in costly multicomponent printed circuit boards which can not be wasted if defective devices are found during testing and electrical inspection. A conventional encapsulant is a thermostable system that is irreversibly reticulated after being distributed on the board. An example of a conventional encapsulant formulation is a liquid epoxy resin such as a bisphenol-A epoxy, a curing agent such as an anhydride with an appropriate accelerator, and other additives. The reprocessing of the semiconductor device with an upper drop encapsulant is difficult and time consuming and is only possible by destructive methods such as grinding and cutting or die grinding. Thus it is desirable to provide a method which allows reprocessing to be more easily processable.

Brief description of the invention According to the invention, an electronic package that can be reused thermally is provided comprising: a substrate having a metallic circuit pattern placed on a first surface of the same; at least one semiconductor device attached to a substrate by means of a bonding adhesive die, preferably a die-binding composition that can be thermally reused; at least one electrically conductive connection; and a reusable encapsulant covering the semiconductor device and a portion of the substrate surface; said thermally reusable encapsulant comprising (a) a reticulated resin that can be re-used produced by reacting at least one dienophile having a functionality greater than one and at least one furan-containing polymer substituted with 2,5-dialkyl, and (b) at least one filler present in an amount from 25 to 75 percent by weight based on the amount of components (a) and (b) by means of this providing an electronic package. Such an electronic package can be easily reprocessed.

Detailed description of the invention There may be several ways by which polymer chains of the crosslinked resin that can be re-use thermally that can be produced. The crosslinked resin that can be reused thermally can be produced by reacting with at least one dienophile having a functionality greater than one and at least one polymer containing furanoo substituted with 2,5-dialkyl connected to one or the other by half of the Diels-Alder addition. In one embodiment the furan groups substituted with 2,5-dialkyl are attached to or form part of the polymer chains. The furan that is reversible to the dienophile reaction to form the Diels-Alder reaction can be represented by: Furano substituted Adduct of 2, 5-dialkyl dienophile DIELS-ALDER where Y is or C < or N- For a reticulated resin that can be reused thermally, all or a portion of the Diels-Alder adduct can revert to the furan and the dienophile on heating such that the resin becomes a liquid (flowable material). A crosslinking agent which contains in its molecular structure two or more dienophiles can also be used in this embodiment. These dienophiles are connected to each other by chemical bonds or groups that form bridges. Accordingly, the present invention also contemplates a reusable encapsulating composition containing a polymer which comprises portions or radicals of a furan substituted with 2,5-dialkyl and a crosslinking agent which comprise two or more dienophiles in its structure molecular. The dienophiles can also be attached to or form part of the polymer chains. The crosslinking agent which comprises in its molecular structure two or more furan groups substituted with 2,5-dialkyl which can also be used. In yet another embodiment, the dienophile is attached to the polymer chains to which the furan groups substituted with 2,5-dialkyl which are also attached or which contain the furan groups substituted with 2,5-dialkyl as a part of their chains of polymer. Accordingly, the furan-containing polymer substituted with 2,5-dialkyl can also contain radicals of a furan substituted with 2,5-dialkyl and radicals of a dienophile. Furans substituted with 2,5-dialkyl may or may not replace their 3- and 4-positions. Preferred substituents are inert substituents such as for example alkyl or akyloxy groups, typically have up to 10 carbon atoms, such as methyl, ethyl, 1-propyl, methoxy and 1-hexyloxy groups. Resins containing furans whose 2 and 5 positions are not substituted are susceptible to side reactions which can cause irreversible curing and interfere with their reversibility. The furan groups substituted with 2,5-dialkyl can be attached to the polymer chains of the polymer (s) on which the crosslinked resin is based. These can be linked to them directly by means of a chemical bond or by means of a group that forms a divalent organic bridge for which any of the substituents of the furans or the 3-or 4-positions of the furans can function as the point of union The alkyl substituents at 2- and 5-positions of the furans can be the same or different and will normally have up to 10 carbon atoms. carbon. Examples of suitable alkyl groups are methyl, ethyl, 2-propyl and 1-hexyl groups. Examples of suitable furyl groups that can be attached to a polymer chain are 2,5-dimethyl-3-yl, 2,5-diethyl-3-methyl-4-yl, 5-ethylfurfuryl or 5- (1-) groups. butyl) furfuryl. The type of polymer chains to which the 2, 5-dialkyl substitution furan groups can be attached is not critical. Suitably the polymer chains are chains of a polyolefin, such as polyethene, polypropene, polystyrene, poly (acrylic acid) or a copolymer of ethene and acrylic acid or ester, chains of random or alternating copolymers of carbon monoxide and olefinically unsaturated compounds (for further elaboration on such copolymers see below), or chains containing heteroatoms , such as polyamide or polyester chains. It is preferred that furans substituted with 2, 5-dialkyls form an element of the main structure of the polymer thereof. In such a case it is particularly preferred that each of the 2,5-dialkyl substituents of the furans are alkylene groups which also form part of the polymer chain and which may or may not be substituted.

Such a structure can be produced by furanized carbon monoxide copolymers and olefinically unsaturated compounds which contain 1,4-dicarbonyl entities in their polymer chains, ie to convert such 1,4-dicarbonyl entities to furan radicals. Alternatively, a furan-containing polymer substituted with 2,5-dialkyl which can be directly produced by reacting carbon monoxide and olefinically unsaturated compounds in the presence of a strong acid. The perfectly alternating copolymers of carbon monoxide and the olymphinically unsaturated compounds which contain 1,4-dicarbonyl entities in their polymer chains are known. These can be prepared by palladium catalyzed polymerization using the known methods of, for example, EP-A-121965, EP-A-181014 and EP-A-516238. The polymers are alternating copolymer preparations of carbon monoxide and the olefinically unsaturated compounds, ie copolymers of which the polymer chains contain the monomer units originating in carbon monoxide (ie carbonyl groups) and the monomer units that originate from the olefinically unsaturated compounds in an alternate arrangement so that every fourth carbon atom of the polymer chain belongs to a carbonyl group. Alternatively the carbon monoxide copolymers and the olefinically unsaturated compounds which contain 1,4-dicarbonyl entities can be random copolymers, ie copolymers of which the polymer chains contain monomer units in a random order. The subsequent copolymers can be prepared by initialized radical polymerization using the known methods of, for example, US Patent Nos. 2,495,286 and US-A-4024326. The furanization of the carbon monoxide copolymer and the olefinically unsaturated compounds can be effected by methods known in the art, for example, by the application of phosphorus pentoxide as a dehydrating agent, as described by A. Sen et al. (J. Polym.Science, Part A. Polym.Chem._3_ (1994) p.8441), or by heating in the presence of a strong acid, such as p-toluenesulfonic acid, as described in US Patent No. 3979373 . These methods allow the conversion of the 1,4-dicarbonyl radicals in the polymer chains to furan radicals at a level of variable conversion, depending on the selected reaction conditions. It is preferred to employ in the furanization an alternating copolymer of carbon monoxide and olefinically unsaturated compounds because they have a higher content of 1-dicarbonyl groups in the polymer backbone so that the furanization can be efficiently performed at a higher level of incorporation of the furan groups. If, however, a lesser degree of furanization is desired, the conversion of the carbonyl groups to furan groups can be saved at low pressure. The carbon monoxide copolymers and the olefinically unsaturated compounds can be. based on hydrocarbons such as olefinically unsaturated compounds. It is preferred that the copolymer is based on an olefinically unsaturated hydrocarbon, suitably an α-define, in particular an α-olefin having up to 10 carbon atoms. Very suitable are the aliphatic α-olefins, in particular those having from 3 to 6 carbon atoms and more particularly those having a straight carbon chain, such as propene, 1-butene, 1-pentene and 1-hexene. Propene is mostly preferred. The copolymer can be regioregular or irregular, stereoregular or atactic.

A furan-containing polymer substituted with 2,5-dialkyl wherein a propene-based polymer and carbon monoxide are furanized which can be represented by the formula: The precise nature of the dienophile from which the Diels-Alder adduct is obtained is not critical, since the Diels-Alder adduct has such thermal stability that the reticulated resin can be reused. Commonly the minimum temperature above which the reticulated resin that can be reprocessed depends on the maximum temperature requirements for the semiconductor device used. The reprocessing is appropriate to carry a temperature of 100 ° C, preferably from 130 ° C to 250 ° C, preferably at 200 ° C. The functionality of the appropriate dienophile can be represented by Y = Y where Y is C <; or N-, or -C = C-. Preferably the dienophiles are, for example, alkynes having groups that withdraw electrons attached to both sides of the ethyne radicals, such as ester and keto groups. Examples are mono- and diesters of butynedioic acid (ie acetylenodicarboxylic acid) and substituted but-2-n-l, 4-diones. Other suitable dienophiles are the compounds containing a but-2-ene-1, 4-dione radical included in a 5- or 6-membered ring, in particular the compounds of the general formula: where X means O, S, N, P, or R where R is alkylene, where at least one of the free valences is occupied by a group that forms a bridge which connects the dienophile with one of the chains of polymer or with another dienophile, and wherein the remaining valencies, if any, are occupied by lower alkyl or acyl substituents or, preferably, hydrogen. Suitable lower alkyl substituents containing up to 4 carbon atoms and are, for example, methyl or ethyl groups. The dienophiles of this general formula are preferably der cyclic maleic anhydrides and, in particular, maleimide (ie X means 0 or, in particular, N-). Examples of other suitable dienophiles include, bis (triazolinodiones), bis (phthalazinodiones), quinones, bis (tricyanoethylenes), bis (azodicarboxylates); diacrylates, maleate or fumarate polyesters, acetylene dicarboxylate polyesters. As indicated above, in one embodiment used, it is made up of a crosslinking agent which comprises in its molecular structure two or more dienophiles of which the Diels-Alder adducts are obtainable. The dienophiles can connect to each other by one or more groups that form a bridge. For example, three dienophiles can connect to each other by a group that form a trivalent bridge. However, it is sufficient that a crosslinking agent is used in which two dienophiles are connected to each other by a group forming a bivalent bridge. The dienophiles can also be connected to each other by chemical bonds. Both the molecular weight and the chemical nature of the group that forms a bridge of the crosslinking agent can vary greatly. It has been found that such variations of the crosslinking agent lead to the castable reticulated resins that cover a range of mechanical properties. The group forming a bridge that can only contain carbon atoms in the bridge but is also possible to contain heteroatoms in the bridge, such as oxygen, silicon or nitrogen atoms. The group that forms a bridge can be flexible or rigid. For example, groups that form a polymeric bridge having flexible polymer chains, such as poly (alkylene oxide) or polysiloxanes, have an average molecular weight number, said, more than 300, providing cross-linked resins that are reprocessed from rubber. When the polymeric flexible chain has an average molecular weight number in the order of 1500-5000 or more, the re-crosslinkable resins that can be obtained which can replace the thermoplastic rubbers can be obtained. Accordingly, suitable crosslinking agents of this type are bis-maleimido-terminated poly (alkylene oxide) s, such as poly (ethylene oxide) or poly (propylene oxide) s, and bismaleimido-terminated polysiloxanes, for example the bismaleimides of polysiloxanes of the general formula H2N-CH2 [-0-SiR2] nO-CH2-NH2, wherein n is an integer number, above the average, of more than 10 and in particular in the range of 20 - 70, and each R is independently an alkyl group, in particular having up to 5 carbon atoms, preferably a methyl group. The best results can be obtained with the poly (propene oxide) bisamino-thermyand bismaleimide, in particular it has an average molecular weight number of at least 300, more in particular in the range of 1500-5000. The groups forming a bridge of low molecular weight, that is, groups that form a bridge that normally have up to 20 carbon atoms in the bridge, can also be used. The groups that form a bridge of cycloaliphatics and aromatics yield the groups that form a rigid bridge. The groups that form a lower molecular weight cycloaliphatic and aromatic bridge tend to provide crosslinkable reshapable resins which are hard and brittle, and have a relatively high glass transition temperature. Examples of groups forming a lower molecular weight cycloaliphatic and aromatic bridge containing a main structure of norbornane in the bridge, the 1,3-phenylene groups and groups of the following formula: -f-CH2-f-, - fOfOf-, -f-0-f-S02-f-0-f- and -fC (CH3) 2-f-, where -f- means a 1,4-phenylene group. Other groups that form an appropriate bridge are alkylene and oxycarbonyl groups (ester) and combinations thereof. Appropriate low molecular weight crosslinking agents are, for example, the bismaleimides of hydrazine, 2,4-diaminotoluene, hexamethylene diaemia, dodecamethylenediamine, diamines of the general formula: and low molecular weight bisamino-terminated (poly) siloxanes, such as the polysiloxanes of the general formula H2N-CH2 [-O-SÍR2] n-0-CH2-NH2, wherein n ranges, on average, from 1 to 10, preferably from 1 to 5 and the R groups are preferably methyl groups.

An isomeric mixture of the diamines of the above formula is commercially available from HOECHST. The best results can be obtained with bis (4-maleimidophenyl) methane and bis [(N-maleimidomethyl) oxy) silane dimethyl. Other suitable crosslinking agents based on maleic anhydride are compounds of the general formula: where A means a group that forms a bridge as described therein, in particular the group that forms a bridge has up to 20 carbon atoms in the bridge. More particularly the group forming a bridge A is an alkylene group, such as a hexamethylene group, or group -DO-CO- or -CO-ODO-CO- where D means a bivalent hydrocarbyl group, for example an alkylene group , such as a hexamethylene group. On the other hand other suitable crosslinking agents are polyesters based on butynedioic acid and a diol, such as ethylene glycol, a poly (ethylene glycol), propylene glycol or a poly (propylene glycol). These polyesters can be low molecular weight crosslinking agents, such as those described above, or those which can have a number average molecular weight, for example, more than 400, such as in the range of 2000 - 6000. The present invention also relates to crosslinking agents such as a bis-maleimido-tertiary poly (alkylene oxide) s, in particular bismaleimido-terminated poly (propene oxide) s.

Such agents have a number average molecular weight of at least 300, preferably in the range of 1500-5000. The bismaleimides of polysiloxanes have the general formula H2N-CH2 [-0-SiR2] n-0-CH2-NH2, wherein n is an integer of at least 1 and each R is independently an alkyl group, in particular it has up to 5 carbon atoms, preferably a methyl group. The bismaleimido-terminated polysiloxanes can be prepared by N-hydroxymethylation of maleimide with formaldehyde and subsequent reaction with the appropriate dichlorodialkylosilane in the presence of base and water using generally known methods. As mentioned above, certain modalities related to a crosslinking agent which comprises in its molecular structure 2,5-dialkylururan radicals. In this crosslinking agent, the furan groups substituted with 2, 5-dialkyls can be connected to one another by means of a chemical bond or by means of a group forming a bridge. The nature of this group that forms a bridge is generally the same as the group that forms a bridge of the crosslinking agents which comprise two or more dienophiles, as described above. Examples of suitable crosslinking agents are bis (5-) adipate ethylfurfuryl) and the bis-amides of (5-ethylfurfuryl) acetic acid and the diamines mentioned in the preceding paragraphs. The furan radicals substituted with 2,5-dialkyl and / or the radicals of a dienophile can be connected to the polymer chains by means of a chemical bond or by means of a group forming a bridge. This group that form a bridge can be of the same type as the groups that form a bridge of the crosslinking agents. The examples can be provided as indicated below. When the polymer is a polystyrene, maleimide, such as dienophile, can be bound to it by catalyzed tin (IV) alkyl chloride of polystyrene with N-chloromethylmaleimide, and when the polymer is a copolymer (styrene anhydride / maleic) a 5-ethylfurfuryl group can be attached thereto by esterification of the copolymer (styrene / maleic anhydride) with 5-ethylfurfuryl alcohol in pyridine. When the polymer is a copolymer of carbon monoxide and olefinically unsaturated compounds which comprise 1,4-dicarbonyl entities in their polymer chains, 2,5-dialkyl furans and dienophiles can be attached thereto by reaction of the copolymer with a hydrocarbyl to suitable substituted primary, for example, using the known methods of the North American patent US-A-3979374. In this reaction the 1,4-dicarbonyl entities are converted into pyrrolo entities which are part of the polymer chain and which are N-substituted with the substituted hydrocarbyl group. For example, a copolymer of carbon monoxide and olefinically unsaturated compounds which comprise 1,4-dicarbonyl entities which can react with the mono-amide of maleic acid and hexamethylenediamine or with the mono-amide of maleic acid and bis (4-) aminophenyl) methane, followed by ring closure of amido acid radicals to maleimide radicals. This will produce a polymer that has N- (6-maleimidohexyl) pyrrolo or N- entities. { 4 - [(4'-maleimidophenyl) -methyl] phenyl} pyrrolo in the polymer chain. When it is desired to use a polymer which contains furan radicals substituted with 2,5-dialkyl and radicals of a dienophile a portion of the 1,4-dicarbonyl entities of a carbon monoxide copoiimer and the olefinically unsaturated compounds can be converted into Furan radicals and another portion of the 1-dicarbonyl entities can be converted to N-substituted pyrrolo entities, of which the N-substituted comprises a dienophile.

The molecular weight of the polymer (s) on which the crosslinked resin that can be reused is / are based allowing varying between wide limits. Conveniently the polymer can have an average number of molecular weight in the range from 500, preferably from 700 to 30,000, preferably to 20,000. The amount of Diels-Alder adducts present in the crosslinked resin that can be thermally reused depends of the amount of 2,5-dialkyl furan groups and the amount of the dienophyll present in the composition from which the Diels-Alders adducts are formed. One skilled in the art will appreciate that a certain minimum amount of Diels-Alder adducts needs to be present to the effect that the resin is a solid material later the temperature at which the Diels-Alder adducts revert to the furan substituted with 2, 5- dialkyl and dienophile. It will also be appreciated that this minimum amount depends on the molecular weight and type of the polymer on which the resin is based and, if any cross-linking agent is used, on the number of dienophiles or furan groups of 2,5-dialkyl per molecule ( that is, functionally) of the crosslinking agent. The lower molecular weights of the polymer will require a higher amount of adducts of Diels-Alder. The number of Diels-Alder adducts may be lower when a crosslinking agent is used which has higher functionality. Generally good results can be achieved by using the polymer containing 2,5-dialkyl furan containing groups of furans to ketone groups provided from 1:16 to 4: 1. The molar ratio of the furan groups substituted with 2,5-dialkyl to amounts of dienophiles is usually from 10: 1 to 1: 5, preferably from 5: 1 to 1: 3. The electronic package of the invention contains a substrate having a metallic circuit pattern disposed on a first surface thereof; a semiconductor device that has one •? > more electrically conductive adapters in a first surface thereof and a second surface joined to the substrate by means of a die-bonding adhesive, preferably a heat-sealable die-bonding composition, one or more electrically conductive connections between the adapters on the device and the metal circuit model of the substrate; and a thermally reusable encapsulant covering the semiconductor device and a portion of the first surface of the substrate. The encapsulant that can be returned to using thermally contains (a) a reticulated resin that can be reused using thermally produced by the reaction of at least one dienophile having a functionality greater than one and at least one polymer containing furan substituted with, 5-dialkyl, and (b) at least one filler present in an amount from 25 to 75 percent by weight based on the amount of components (a) and (b) thus providing an electronic package. One or more semiconductor devices may be attached to the substrate with an adhesive, and covered by a top drop encapsulant. The top droplet encapsulant also covers portions of the first surface of the substrate. Preferably, a thermally reusable die-bonding composition and thermally reusable epcapsulant containing resins that can be reused for thermally similar use are used as a die-bonding adhesive and a higher drop encapsulant respectively . A conventional die-bonding adhesive such as an epoxy-based adhesive can also be used. The die-binding composition that can be thermally reused preferably comprises (a) a crosslinked resin that can be re-used thermally produced by reacting at least one dienophile having a functionality greater than one and at least one polymer containing furan substituted with 2,5-dialkyl, and (b) at least one electrically and / or thermally conductive material present in an amount effective to provide a conductive medium, up to 90% by weight, preferably in an amount from 60% to 90% by weight, of the die-binding composition. The thermally preferred conductive material is such as, for example, beryllium, boron nitride, aluminum oxide (single crystal), copper-coated aluminum nitride (see US Patent No. 5,288,769) and the like. Electrical contact is provided by the incorporation of electrically conductive materials (fillers) such as silver, nickel, copper and aluminum particles as well as the alloying of such metals in the die-bonding adhesive formulation. The substrate can be an organic, metallic or ceramic substrate such as that used in a spherical grid array construction, or it can be a multi-component printed circuit board. For example, an organic printed circuit board containing an electrically insulating material, such as a fiber reinforced resin of glass, normally used in a laminated construction. At least one integrated circuit die or semiconductor device is electrically and mechanically connected to electrically conductive metal traces (metal circuit designs) on the substrate. The die or device is bonded to a region of the printed circuit board using a die bonding adhesive. The die is preferably bonded with a die-binding composition that can be reused thermally. The die or semiconductor device is electrically interconnected by means of gold, tinned copper, or aluminum wires to electrically conductive traces on the printed circuit board substrate. An encapsulant that can be reused thermally (top drop encapsulant that can be reused thermally) is deposited on the semiconductor die or device, electrically conductive connections, and a portion of the substrate. The encapsulant as described above is deposited while in a fluid and fluid state it covers the affected areas. The encapsulant that can be reused thermally can be distributed over the substrate by using standard equipment such as a syringe or a fixed mixer that mixes the components of the encapsulant that can be thermally used and precisely distribute the composition on the substrate. After the deposition of the encapsulant, it is cured to a solid form by low cooling to a temperature that is sufficient to solidify the encapsulant. The encapsulant which can be thermally reused normally contains a filling of 25%, preferably 40%, 75%, preferably 60% by weight of the binder based on the weight of the composition (resin and filled). The filling can be any suitable inorganic filler for semiconductor packing applications such as high fused purity or amorphous silica or commercial synthetic glass fillers. The stuffing may optionally be treated with a coupling agent such as a silane. Normally the filling and the resin should be at least substantially free of ionic impurities of chloride, sodium and potassium (less than 20 ppm each). The process of the invention provides a process which eliminates most of the ionic impurities found in the processes Traditional using epoxy resin based binders. In addition, the encapsulant that can be used thermally can be worked and / or reprocessed at a temperature where the encapsulant is melted and can be thermally used again (becoming liquid). Usually, the encapsulant that can be thermally reused can be worked and / or reprocessed at a temperature within the range of 100 ° C, preferably 130 ° C, 250 ° C, preferably 200 ° C. If the resin is heated for an extended period of time at high temperature, for example, for 12 hours at 200 ° C, the resin undergoes irreversible crosslinking and is merely thermally reversible. In order to reprocess the electronic package, the thermally reusable encapsulant is heated to a temperature which is high enough to convert the encapsulant that can be reused into a liquid thereby providing a liquid composition that can be cleaned of the substrate easily. If the semiconductor device is attached to the substrate by means of a die-binding composition that can be thermally reused, the device can also be removed from the substrate by applying heat to convert the die-binding composition that can be thermally reused in a liquid, thereby providing a device that removes the substrate. If the die-binding composition consists of a cross-linked resin system, a destructive method such as a die cut used to remove the device from the substrate. The electrically conductive connections break when the device is removed. Then another semiconductor device can be attached to the device removed from the board if desired by means of an adhesive, preferably a die-binding composition that can be thermally reused, then covering the other semiconductor device and a portion of the surface of the substrate with an encapsulant that can be used again just finished as described above and then cooling the encapsulant that can be used again just finished at a temperature which is low enough to solidify the resin whereby a reprocessed electronic package is produced. The encapsulant that can be used again can be boiled later to improve the thermal and mechanical properties (for example, the temperature of glass transition and mechanical force). In order to preserve the thermal reversibility of the crosslinked resin, the thermally usable composition can be subsequently heated to a temperature in the range of 50 ° C, preferably 80 ° C, 200 ° C, preferably 160 ° C. C for a period of time of up to 4 hours or more. If thermal reversibility is not required, the binder composition can be subsequently baked at a temperature within the range of 150 ° C, preferably from 180 ° C, to 300 ° C, preferably at 250 ° C for a period of time of up to 4 hours to improve the thermal properties.

Illustrative Modality The following illustrative embodiments describe the new electronic package that can be thermally reused from the invention and are provided for illustrative purposes and are not intended to limit the invention.

Example 1 An autoclave is changed with methanol and propene (approximately 1.7: 1 in weight proportion), heated to 90 ° C, and then the change with the monoxide of carbon at a pressure of 72 bar. A catalyst solution of palladium acetate, 1,3-bis- (diethylphosphino) propane, trifluoromethane sulphonic acid, in a weight ratio of 0.6: 0.62: 1 and 0.3 of pyridine, in a tetrahydrofuran, and a methanol solution ( weight ratio of 15: 1) were injected and the reactor pressure was kept constant at 72 bar during the reaction by means of a continuous supply of carbon monoxide. Removal of the solvent produced a propene / CO copolymer alternating with an average molecular weight number of 733.

Example 2 A CO propene copolymer alternating with an average molecular weight number of 733 made as described in Example 1 was dissolved in toluene and cyclized in the presence of a catalytic amount of p-toluene sulfonic acid by heating to reflux until no more water was collected in the distillate. The resulting polymer was analyzed by C-13 NMR which showed that 82% of the ketones in the starting polyketone were cyclized to furans (ratio of furan: ketone 2.28: 1) apparently by the signals of C-13 NMR centered around 107, 114, 147 and 153 ppm.

Example 3 A system was made by mixing the furanized polyketone made in Example 2 and a stoichiometric amount of methylene dianiline bismaleimide (Compimide Resin MDAB, Technochemie Gmbh) at 171 ° C (340 ° F). The mixture was removed from the gel plate and stored at room temperature. A masked 8-ply weld (epoxy-glass screen) of the printed circuit board with a chip attached to the die was placed on the gel plate at 171 ° C (340 ° F) and allowing to warm up to the temperature. A small amount of the mixture was distributed on the chip and leaving the "drop" on the chip. The board was then cooled to room temperature to allow the encapsulant to become a cross-linked solid. The board was placed on the back on the gel plate and allowed to warm up for one minute. The drop was understood to be a non-crosslinked liquid of low viscosity. The board was removed from the gel plate and the encapsulant was returned to its solid cross-linked state Example 4 A mixture was made by mixing the furanized polyketone made in example (2), a stoichiometric amount of MDAB at 171 ° C (340 ° F) and filled with silica (50.4% by weight of the total formulation). The mixture was removed from the gel plate and stored at room temperature. A masking of 8-ply welding (epoxy-glass screen) of the printed circuit board with a chip attached to the die was placed on the gel plate at 171 ° C (340 ° F) and allowed to warm to the temperature. A small amount of the mixture was distributed on the chip and the "drop" was left on the chip. The plate was then cooled to room temperature to allow the encapsulant to become a cross-linked solid. The board was placed on the back on the gel plate and allowed to warm up for one minute. The drop was understood to be a non-crosslinked liquid. The board was removed from the gel plate and the encapsulant returned to its solid cross-linked state.

Example 5 An alternating CO olefin copolymer (27% ethylene, 73% propylene) with an average molecular weight number 1472 was prepared in a similar manner to that of Example 1 of propene and ethylene. The copolymer was dissolved in toluene and cyclized in the presence of a catalytic amount of p-toluene sulfonic acid by heating under reflux. The resulting polymer was analyzed by C-13 NMR which showed that 56% of the ketones in the initial polyketone were cyclized to furans (ratio of furan: ketone 0.64: 1).

Example 6 A gel plate was set at 171 ° C (340 ° F) and the furanized polyketone made in Example 5 was distributed on the plate. A stoichiometric amount of toluene diamine bis (Comimide Resin TDAB, Technochemie Gmbh) was mixed with the furanized polyketone until a homogenous mixture is obtained. The mixture was removed from the plate and stored at room temperature.

Example 7 An ICI cone and a viscometer plate were set at a temperature of 175 ° C and allowed to equilibrate to the set point. A small amount of the mixture of Example 6 was placed on the plate and allowed to rise to temperature. The cone was lowered and stirred to get a good film between the cone and the plate. This was verified by raising the cone to check the good film formation. Consecutively the mixture was left to equilibrate for 90 seconds and two viscosity readings were taken while the cone is rotated at a fixed speed. The cone was lifted and the mixture recovered from the cone and the plate at the same time. The mixture was allowed to cool to room temperature for a cross-linked solid. The previous succession of events was repeated three times with the same mixture ie the load on an ICI cone and the plate, the viscosity is measured at 175 ° C, the mixture is removed, to cool to room temperature. The three consecutive readings for viscosity were 3-5 poises, 3-5 poises and 3-5 poises. This experiment shows that the mixture passed from a cross-linked state at room temperature to a non-crosslinked liquid of low viscosity at 175 ° C.

Example 8 The furanizada polyketone elaborated in the Example 5 was mixed with a stoichiometric amount of TDAB at 171 ° C (340 ° F) on a gel plate. The mixture was cooled to room temperature. This mixture was also mixed with silica filler (50% by weight of the total formulation) homogeneously at 171 ° C (340 ° F). The filling formulation was then removed from the gel plate and cooled to room temperature.

Example 9 An ICI cone and the viscometer plate was set at a temperature of 175 ° C and allowed to equilibrate to the placed point. A small amount of the mixture of Example 8 was placed on the plate and allowed to rise to temperature. The cone was lowered and stirred to obtain a good film between the cone and the plate. This was verified by raising the cone to check the good formation of the film. Consecutively the mixture was left to equilibrate for 90 seconds and two viscosity readings were taken while the cone was rotating at a fixed speed. The cone was lifted and the mixture recovered from the cone and the plate at the same time. The mixture was allowed to cool to room temperature for a cross-linked solid. The previous succession of events was repeated three times with the same mixture ie the charge on the cone of ICI and the plate, the viscosity at 175 ° C, the mixture is removed, cooled to room temperature. The three consecutive readings for viscosity were 20-25 poises, 20-25 poises and 25-30 poises. This experiment shows that the mixture went from a cross-linked state at an ambient temperature to a liquid crosslinked at 175 ° C.

Example 10 A CO propene copolymer alternating with an average molecular weight number 1616 prepared in a manner similar to Example 1, except that l, 3-bis (di-o-methoxyphenylphosphino) propane was used in the catalytic solution instead of 1, 3-bis (diethylphosphino) propane. The copolymer was dissolved in toluene and cyclized in the presence of a catalytic amount of p-toluene sulfonic acid by reflux heating until no more water was collected in the distillate. The resulting polymer was analyzed by C-13 NMR which showed that 57% of the ketones in the starting polyketone were cyclized to furans (ratio of furan: ketone 0.66: 1).

Example 11 The furanised polyketone made in the Example 10 and a stoichiometric amount of TDAB together with 6.5% by weight of phenothiazine were heated to 180 ° C, mixed and poured into a coarse metal mold of 3.2 mm (1/8 inch). The mold cooled rapidly and the resulting test was tested by properties. The flexional sampling module was found to be 43 bar (628 ksi), a value similar to that of a crosslinked epoxy made with an epoxy curing of bisphenol A with a hardening anhydride. The dielectric constant and the dissipation factor were 3.17 and 0.013 respectively.

Example 12 The furanized polyketone made in Example 10 was reacted with a stoichiometric ratio of 2: 1 of MDAB, 0.1 mol of phenothiazine / mol of MDAB and 0.015 g of 2-ethylhexanoic acid / gm of furanised polyketone. A differential examination of the examined calorimetry was performed on the sampling at a ramp rate of 20 ° C / min. The initiation of glass transition temperature occurred at 105 ° C.

Example 13 The furanised polyketone made in the Example 5 was reacted with a stoichiometric amount of TDAB and 0.1 moles of phenothiazine / mole of TDAB on a gel plate at 171 ° C (340 ° F). This sampling taught the elements and they were placed in a Parr pump with water in a ratio of 10: 1 (water sampling). The Parr pump was stored at 60 ° C for 20 hours and the water extract was analyzed by ion by ion chromatography. The extract contained 14 ppm acetate, < 3 ppm glycolate, formate, propionate, < 0.25 ppm chlorine, < 1 ppm of nitrate, 1.7 ppm of sulfate, 4.8 ppm of sodium, 0.8 ppm of magnesium, 2.5 ppm of calcium and 0.2 ppm of ammonium ion.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. An electronic package characterized in that it comprises: a substrate containing a metal circuit model placed on a first surface thereof; a semiconductor device having first and second surfaces wherein said first surface including at least one heating pad and wherein said second surface is joined to said first surface of said substrate by means of an adhesive bond matrix; at least one electrically conductive connection between said at least one electrical stuffing on said semiconductor device and said metal circuit pattern of said substrate; and an encapsulating cover that can be thermally reused said semiconductor device and a portion of said first surface of said substrate; said encapsulant that can be reprocessed thermally comprising (a) a crosslinked resin that can be thermally processed produced by reacting at least one dienophile having a greater functionality than one and at least one polymer containing furan substituted with 2,5-dialkyl, and (b) at least one filler present in an amount from 25 to 75 percent by weight based on the total amount of the components (a ) and (b).

2. The electronic package according to claim 1, wherein the die-bonding adhesive is a thermally reusable die-bonding composition characterized in that it comprises: (a) a reticulated resin that can be re-processed thermally produced by reacting at least one dienophile having a functionality greater than one and at least one polymer containing furan substituted with 2,5-dialkyl, and (b) at least one thermal and / or electrically conductive material present in an amount from 60% to 90% by weight of the die-binding composition.

3. The electronic package according to claim 2, characterized in that the reticulated resin that can be reprocessed thermally which can be reused at a temperature between the range of 100 ° C to 250 ° C.

. The electronic package according to claim 3, characterized in that the dienophile is an alkyne having electron separation groups attached on both sides of an ethyne radical, or a cyclic derivative of maieic anhydride.

5. The electronic package according to claim 4, characterized in that the dienophile is selected from the group consisting of the compounds containing but-2-ene-l, -dione radicals in 5-membered rings, and compounds containing but-2 radicals -eno-l, 4-dione in 6-membered rings.

6. The electronic package according to claim 4, characterized in that the resin that can be thermally reused additionally comprises a residue of a crosslinking agent selected from the group consisting of bismaleimido-terminated poly (alkylene oxide) s, polysiloxanes of bismaleimido-terminated, bismaleimides of hydrazine, 2,4-diaminotoluene, hexamethylenediamine, dodecamethylenediamine, and substituted and unsubstituted diamines of the general formula:

7. The electronic package according to claim 1, characterized in that the furan-containing copolymer substituted with 2,5-dialkyl is produced by reacting with carbon monoxide with at least one olefinically unsaturated compound.

8. A preparation process in an electronic package characterized in that it comprises the steps of: providing a substrate having a metallic circuit pattern placed on a first surface thereof; providing at least one semiconductor device, said at least one semiconductor device having a first surface and a second surface, said first surface includes at least one adapter; distributing a die attachment adhesive onto a portion of said first surface of said substrate; attaching said second surface of said at least one semiconductor device to said first surface of said substrate by means of said die attachment adhesive; joining at least one electrically conductive connection between said at least one adapter on said semiconductor device and said metallic circuit model of said substrate; and covering said semiconductor device, said electrically conductive connection, and a portion of said first surface of said substrate with an encapsulant that can be thermally reused thereof to provide an electronic package; said encapsulant which can be thermally reused comprises (a) a re-useable reticulated resin produced by reacting at least one dienophile having a functionality greater than one and at least one furan-containing polymer substituted with , 5-dialkyl, and (b) at least one filler present in an amount from 25 to 75 percent by weight based on the quantity of components (a) and (b) by means of this providing an electronic package.

9. The process according to claim 8, wherein the die-bonding adhesive is a thermally reusable die-bonding composition characterized in that it comprises: (a) a reticulated resin that can be reprocessed thermally produced by reacting at least one dienophile having a functionality greater than one and at least one polymer containing furan substituted with 2,5-dialkyl, and (b) at least one thermal and / or electrically conductive material present in an amount from 60% to 90% by weight of the die-binding composition.

10. The process according to claim 9, characterized in that it additionally comprises the steps of: heating said encapsulant that can be thermally re-used from said electronic package at a temperature which is high enough to convert said encapsulant which can be re-used. use thermally in a liquid in such a way that it provides a liquid encapsulant; withdrawing said liquid encapsulant; heating said thermally reusable die-bonding composition to a temperature which is high enough to convert said bound composition to the thermally reusable die in a liquid in such a way as to provide a composition bound to the liquid die; removing said semiconductor device from said composition attached to the liquid die on said substrate; and removing at least a portion of said composition attached to the liquid die of said substrate in such a way as to provide a new surface.