KR20120128726A - Adhesion promotion of metal to a dielectric - Google Patents

Abstract

PURPOSE: A method for promoting adhesion between a dielectric and metal is provided to improve adhesion by processing the dielectric with solutions including amine compounds greater than curable epoxy compounds. CONSTITUTION: A surface of a dielectric substrate is processed by applying solutions including curable amine compounds and curable epoxy compounds. The solutions are dried near the processed surface of the dielectric substrate. Metal is electroless plated on the processed surface of the dielectric substrate. Amine compounds and epoxy compounds are cured by heating the dielectric substrate plated with the metal. [Reference numerals] (AA) Before; (BB) After

Description

Adhesion promotion of metal to a dielectric

The present invention relates to a method for promoting the adhesion of metal to a dielectric. More specifically, the present invention relates to a method of promoting adhesion of metal to a dielectric by treating the dielectric with a solution containing more curable amine compounds than the curable epoxy compound.

Electroless metal plating of dielectrics has been done for a long time. Usually such a dielectric is a component of a composite composed of a polymer resin sheet, which has a continuous or discontinuous metal foil bonded to both sides of the sheet. An example of such a composite is a printed circuit board (PCB).

Several printed circuit boards may be combined with each other to form a multilayer substrate. In a multilayer substrate, the circuit of one substrate is connected to the circuits of one or more remaining substrates. This is accomplished by forming pads or circular portions of the metal at points on the conductive lines of the substrate. The pad can also be separated from the conductive line. The remaining substrate to be connected is provided with the pads and the pads of the other boards are aligned with each other in the bonding process.

After that, the multilayer substrate is pressed and cured, and then perforated to form through-holes. Since the through-holes in the cross section present the alternating layer surface of the individual circuit board pads separated by the non-conductive polymer resin, an electrically conductive element is formed to form an electrical connection between the pads. It should be used in through-holes. This is done by a process known in the art as through-hole plating (PTH).

The demand for enhanced performance and functionality of integrated circuit components has steadily increased the design and manufacturing complexity of PCBs. Substrates manufactured for these components need to be made of multiple copper layers in dielectric materials. The width of the copper traces continues to shrink, making copper adhesion to the dielectric more difficult. One method commonly used to promote the adhesion of copper to dielectric build-up materials is desmear. Typically, desmear treats the dielectric substrate surface with a solvent swell to penetrate into the polymer free space and produce a surface for oxidation; the dielectric surface and surface by treating with a oxidant such as permanganate or chromate. Promoting micro-roughness by oxidizing polar species in the vicinity, treating the neutralizing agent to remove reactions by the by-product or solvent from the previous step and de-swelling the matrix. swell). The metal catalyst is then applied to the micro-concave dielectric surface and an electroless metal plating bath is applied to deposit the thin metal layer. The micro-concave surface allows for the formation of a mechanical bond between the dielectric surface and the thin film metal layer. However, more average unevenness alone is not sufficient for metals to adhere better to the dielectric surface. In addition, the smaller the substrate and features of the substrate, the lower the electrical performance of the micro-concave surface. Current lines and other essential substrate features pass through irregular contours on the surface, resulting in poor electrical performance. In addition, the PCB being manufactured has a smoother surface and many conventional mechanically attached and etched surface methods are not readily available as in the past. Thus, there is a need to remove or reduce irregular surfaces of dielectrics while providing good adhesion between thin film metal layers and dielectrics.

In one aspect of the invention, there is provided a method comprising: providing a dielectric substrate; Treating the surface of the dielectric substrate by applying a solution comprising at least one curable amine compound and at least one curable epoxy compound adjacent to the surface of the dielectric substrate, wherein the solution comprises an excess of at least one curable amine in excess of the at least one curable epoxy compound. step; Drying the solution adjacent the treated surface of the dielectric substrate; Electroless plating a metal on the treated surface of the dielectric substrate to form a composite; And heating the metal plated dielectric substrate to cure one or more amine compounds and one or more epoxy compounds.

In another aspect, the solution comprises at least one curable amine compound and at least one curable epoxy compound, wherein at least one curable amine compound in the solution is included in excess of at least one curable epoxy compound.

The method of the present invention enables the formation of chemical bonds between the dielectric substrate and the metal layer, as opposed to the mechanical bonds in conventional bonding methods for bonding metal to the dielectric. In addition, amines present in excess relative to the amount of epoxy in the adhesive formulation allow any open functionality on the dielectric surface to cure with the amines and the epoxy. The micro-concave of the dielectric surface is largely avoided, and the fairly smooth surface allows current lines and other essential features of the electronic device to provide uniform current and improve electrical performance. In addition, a smoother surface allows for finer line circuits and hence smaller products. In addition, the adhesive component is sufficiently similar to the dielectric material of the dielectric substrate in the properties of the dielectric to provide the desired chemical adhesion.

As used throughout this specification, the following abbreviations have the following meanings unless the context clearly indicates otherwise; g = grams; kg = kilograms; L = liter; eq = equivalent; cm = centimeters; mm = millimeters; Μm = micrometer; C = degrees Celsius; ASD = amps / dm ² ; UV = ultraviolet; wt% = weight percent; T _g = glass transition temperature; And SEM = scanning electron micrograph.

The terms "printed circuit board" and "printed wiring board" are used interchangeably throughout this specification. The terms "plating" and "deposition" are used interchangeably throughout this specification. The term "desmear" means the removal of accretion or unwanted residue from the dielectric material. Unless stated otherwise, percent by weight: all numerical ranges are inclusive and can be combined in any order except where it is logical to limit these numerical ranges to 100%.

The solution comprises at least one curable amine compound and at least one curable epoxy compound, wherein at least one curable amine compound in the solution is included in excess of the weight and moles of the at least one epoxy compound. Typically, the at least one curable amine compound in solution has a weight ratio of at least 2: 1, such as 2: 1 to 4: 1 or 3: 1 to 4: 1 or 3.5: 1 to 4: 1, relative to the one or more curable epoxy compounds Included in molar ratios.

Amine compounds that can be used include, for example, amine compounds that can be cured using conventional curing methods such as UV and thermal curing methods. Typically such amine compounds are polyamines and have at least two reactive amine hydrogen atoms, such as at least three reactive amine hydrogen atoms. Such compounds are well known to those of ordinary skill in the art. Typically, the polyamine compound comprises at least one primary amino group, more typically at least two primary amino groups and most typically at least three primary amino groups. They are attached to terminal secondary or tertiary carbons. In addition, the amino group is bonded to two carbon atoms and subsequently forms a polyamino polyalkylene compound or a cyclic compound.

The polyamine compound may be selected from one or more aliphatic, cycloaliphatic, aromatic cycloaliphatic and aromatic polyamines. Such polyamines are well known in the art.

Typically aliphatic amines are polyethers containing linear or branched hydrocarbon polyamines and polyamines, for example polyamines comprise a poly (oxyalkylene) backbone. Typically, linear or branched hydrocarbon polyamines comprise at least three active amine hydrogens, more typically 3 to 20 active amine hydrogens. These include at least two amine groups, typically 2 to 10 amine groups. Typically, they contain 2 to 30, more typically 4 to 16 carbon atoms. Carbon atoms may be present in one single straight or branched hydrocarbon chain. They may also exist in the form of a plurality of straight or branched hydrocarbon chains connected by one or more amine groups. Examples of linear and branched hydrocarbon polyamines are ethylenediamine, diethylenetriamine, triethylenetetraamine, tetramethyldipropylenetriamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetraethylenepentamine, penta Ethylenehexamine, polyethyleneamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, 1,3-diaminopentane, hexamethylenediamine, 2-methyl-pentamethylenediamine, neopentane Diamine, (2,2,4)-and (2,4,4) -trimethylhexamethylenediamine (TMD), aminoethylpiperazine, 1,6-hexamethylenediamine, N, N-dimethylaminodipropanetriamine And 1,13-diaminotridecane. Examples of commercially available polyamines are JEFFAMINE ^® Trimaines (T series) and JEFFAMINE ^® Secondary Amines (SD series and ST series).

Polyethers containing polyamines include at least two active amine hydrogens, typically 3 to 20 active amine hydrogen groups, at least two amine groups, typically 2 to 10 amine groups, and 6 to 150, typically Comprises from 2 to 50 and more typically from 2 to 30 carbon atoms and from 2 to 6, typically from 2 to 3 carbon atoms in the ether group. Polyether polyamines include poly (oxyalkylene) backbones. This backbone may be a homopolymer or a copolymer of two or more oxyalkylene monomer units. Typically, polyoxyalkylene polyamines are derived from poly (propylene oxide) or poly (ethylene oxide) or copolymers thereof. Typically, the average molecular weight of the polyether polyamines is 150-2000, more typically 150-500. The above definitions of polyether polyamines include all polyamines containing in their backbone polyols, glycidyl and monomers other than oxyalkylenes such as bisphenol A and bisphenol B.

More typically, the polyether polyamines included in the solution are selected from polyoxypropylene polyamines such as polyoxypropylene diamine and polyoxypropylene triamine. Such polyether polyamines may have an average molecular weight of 150 to 2000, such as 150 to 500. Most typically, such polyoxypropylene diamines and triamines comprise at least one amine group attached to a secondary carbon element.

Many polyether polyamines are commercially available. Examples of commercially available polyether ^{polyamines, JEFFAMINE ® D230, D400, D2000} , T403, XTJ-502, a polyoxypropylene sold by Huntsman Corporation as JEFFAMINE ^® brand as XTJ-504, XTJ-506 and T-5000 Diamines and triamines.

Additional amines that can be included in a solution is a piperazine, such as aminoethyl piperazine and N- dimethylpiperazine sold under the trademark JEFFCAT ^®. In addition, substituted polyamines such as dimethaminopropylamine, methoxypropylamine and aminopropylmorpholine can be included in the solution. Another additional amine that may be included is an amine branded EPIKURE ™.

The solution may also include polyether aliphatic polyamines such as cyanoalkylated and hydrogenated polyalkylenes such as cyanoethylated. More specifically, they are obtained by a cyano -C _{2 -10} alkylation and hydrogenation of polyether such as a polyoxyalkylene. In the case of cyanoethylation, diaminopropyl ether such as poly (oxyalkylene) diaminopropyl ether is obtained. Polyethers are as defined above. An example of a commercially available polyether aliphatic polyamine is a product under the trademark ANCAMINE ^® 1922A from Air products & Chemical.

The cycloaliphatic polyamine has 1 to 4 nonaromatic rings, at least 3, typically 3 to 20 active amine hydrogens, at least 2, typically 2 to 10 amine groups, and the amine groups from the ring or ring It may include, but is not limited to, 4 to 30, more typically 6 to 20 carbon atoms, or combinations and mixtures thereof, directly bonded to or extended within the extended alkyl chain. Isophoronediamine (IPDA), bis- (p-aminocyclohexyl) methane (PACM), cyclohexanediamine (DCH), polycycloaliphatic polyamine (MPCA) linked with methylene, [5,2,1,0] -tree Cyclodecane-2,6-bis-hexamethylenediamine and norbornane diamine (NBDA) are examples.

Aromatic polyamines include 1 to 4 aromatic rings, at least 3 to 20 active amine hydrogens, at least 2, typically 2 to 10 amine groups, and 8 to 30, typically 8 to 20 carbons. Polyamines comprising an atom include, but are not limited to, wherein at least two amine groups are attached to an alkyl chain extending from an aromatic ring. Examples of such polyamines are m-xylylenediamine and p-xylylenediamine.

Aromatic polyamines include 1 to 4 aromatic rings, at least 3, typically 3 to 20 active amine hydrogens, at least 2, typically 2 to 10 amine groups, and 6 to 30, typically 6 to Polyamines containing 20 carbon atoms include, but are not limited to, at least two amine groups directly attached to the aromatic ring. Examples of such polyamines are methylenediamine (MDA), 1,3- and 1,4-toluenediamine and m-phenylene-diamine (mPD).

The solution has an epoxy solid of 150 g / eq, typically 150 g / eq to 2000 g / eq or more. The term "epoxy solid equivalent" is the gram weight of an epoxy compound containing 1 mole of epoxide functionality, excluding solvent and water. This can be determined by titration with perchloric acid in the presence of tetraalkylammonium bromide compounds, as is well known in the art. The functional groups of a compound refer to the average number of functional groups per molecule, here an epoxy group.

The epoxy compound included in the solution contains at least one epoxide or oxirane group, and typically the epoxide compound generally comprises one or more epoxide groups. Such epoxide compounds are, for example, glycidyl ethers of polyhydric phenols such as glycerol, hydrogenated diphenylolpropane or polyhydric alcohols, resorcinol, diphenylolpropane or phenols and aldehyde condensation. Including but not limited to water. In addition, glycidyl esters or dimerized fatty acids of polybasic carboxylic acids, such as hexahydrophthalic acid, may be included in the solution. Other suitable epoxy compounds are, for example, monofunctional aliphatic and monofunctional aliphatic such as butylglycidyl ether or phenylglycidyl ether or epoxide such as glycidyl ester or styrene oxide such as glycidyl acrylate. Side, or polyfunctional di- or triglycidyl ethers. Typically, polyfunctional di- and triglycidyl ethers are used, more typically diglycidyl ethers of polyalkylene glycols or cycloalkylene glycols. Typically, the diglycidyl ether of polyalkylene glycol is a polyalkylene glycol initiated with water or a C _{1 -6} alkane polyol is terminated with glycidyl ether moieties. The polyalkylene glycol chain may be a butane diol, 1,2 propane diol or 1 such as ethylene oxide, propylene oxide, butylene oxide, ethylene glycol, propylene glycol, butylene glycol, 1,3 butane diol or 1,4 butane diol And, but are not limited to, those derived from propane diols, such as propane diol. Such epoxy compounds are well known to those of ordinary skill in the art. Commercially available ethylene diglycidyl ether is QUETOL ™ 651 from Polyscience and commercially available 1,4-butanediol diglycidyl ether is ERISYS ™ GE-21 from Emerald Performance Materials.

Diglycidyl ether of cycloalkylene glycol, including cycloalkylene compounds containing C _{5 -20} alkylene chain containing at least one 5-membered ring, but are not limited thereto. Typically, the alkylene chain is a cycloalkylene chain C _{6 -10} containing 6-membered ring. An example of glycidyl ether of cycloalkylene glycol is diglycidyl ether of cyclohexane diol.

Additional epoxy compounds include bisphenol-based epoxy and novolac epoxy compounds. Examples of bisphenol-based epoxy compounds are bisphenol A glycidyl ether, bisphenol F glycidyl ether, modified bisphenol A glycidyl ether, modified bisphenol F glycidyl ether. Such epoxy compounds are well known in the art. Examples of the bisphenol-based epoxy compound is commercially available is sold under the trademark ^{BECKOPOX ® EP384w / 53WAMP, ® EPI} -REZ ® 3521WY53, ARALDITE ® PZ3961 and WATERPOXY 1422.

Novolak epoxy compounds are also commercially available. Examples of commercially available novolac epoxy compounds are EPI-REZ ^® 5003W55, EPI-REZ ^® 6006W70, ARALDITE ^® PZ323 and HUNTMANS ™ 3601 epoxy.

The solution may be aqueous, solvent type or mixtures thereof. In aqueous solutions, when one or more curable amines or one or more curable epoxy compounds are not sufficiently dissolved, one or more water soluble or water miscible organic solvents may be added to dissolve the components. The solution is not a dispersion or suspension of the particles. Sufficient amount of water or solvent is added to dissolve the amine and epoxy solute compound. The amount of solvent can vary depending on the solids content of the desired dielectric and the thickness of the coating. Typically, water or organic solvent is present in 30 to 70 parts by weight of the solution and the remainder is solute.

Conventional organic solvents can be used. Such organic solvents include, but are not limited to, alcohols such as mono- and polyhydroxy alcohols, ketones such as methyl ethyl ketone, glycols, glycol ethers, glycol ether acetates, esters and aldehydes.

In addition to the curable amine and the curable epoxy compound, the solution also includes one or more conventional surfactants. Surfactants are contained in conventional amounts such as 0.05 to 5 parts by weight, or 0.25 to 1 part by weight of the solution. Typically, surfactants are non-ionic surfactants and include aliphatic alcohols such as, for example, alcohol alkoxylates. Such aliphatic alcohols are polyoxyethylene or polyoxypropylene chains in the molecule, ie chains composed of repeating groups (-O-CH ₂ -CH _2- ), or repeating groups (-O-CH ₂ -CH _2). Ethylene oxide, propylene oxide, or a combination thereof to produce a chain consisting of -CH ₃ ), or a combination thereof. Typically, such alcohol alkoxylates are linear or branched carbon chains of 7 to 15 carbons, and 4 to 20 moles of ethoxylate, typically 5 to 40 moles of ethoxylate and more typically 5 Alcohol ethoxylates having from 15 moles of ethoxylate. Many such alcohol alkoxylates are commercially available. Examples of commercially available alcohol alkoxylates include, for example, NEODOL ™ 91-6, NEODOL ™ 91-8 and NEODOL ™ 91-9 (average 6-9 moles of ethylene oxide per mole of linear alcohol ethoxylate). Linear primary alcohols such as C ₉ -C ₁₁ alcohols) and NEODOL ™ 1-73B (C ₁₁ alcohols having an average blend of 7 moles of ethylene oxide per one mole of linear primary alcohol ethoxylate). Both are from Shell Oil Company (Houston, Texas).

The solution also includes one or more cure accelerators. Conventional curing accelerators can be used in conventional amounts such as 0.05 to 5 parts by weight. Examples of such accelerators are amine complexes of imidazole derivatives such as 2MZ, 2E4MZ, C11Z, C17Z and 2PZ, guanamines such as acetoguanamine and benzoguanamine, organic acid salts and boron trifluoride, manufactured by Shikoku Chemicals Corporation , Triazine derivatives such as ethyldiamino-S-triazine, 2,4-diamino-S-triazine and 2,4-diamino-6-xylyl-S-triazine, polyphenols, tertiary ammonium salts , Organic phosphines and cationic photopolymerization catalysts such as IRGACIRE ™ 261 manufactured by Ciba Geigy Co., Ltd.

The components of the solution may be combined in any order. If necessary to facilitate dissolution of the components, the solution may be heated. Typically, the components are combined with each other at room temperature. Mixing can be performed using a conventional stirring device.

The substrate is cleaned before applying the solution to the dielectric substrate. Washing can be carried out using conventional methods such as conventional surfactants and chemical washes.

The solution may then be applied to at least one surface of the dielectric substrate. The solution can be applied to the dielectric surface using conventional devices to form a very smooth and uniform layer. Such conventional devices include double-sided screen printers such as those manufactured by Built-In Precision Machine Co., Ltd., gravure coating, reverse roll coating, knife over roll coating. Or gap coating, metering rod coating, slot coating, immersion dip coating, curtain coating, air knife coating coatings and spray coatings, but are not limited thereto. The thickness of the solution coating can vary. Typically, the thickness of the coating is 0.5 μm to 5 mm, such as 1 μm to 1 mm. Variables such as viscosity of the solution, solids content such as 1% to 50%, retraction rate from the coating apparatus and temperature at which room temperature is typical may determine coating thickness and uniformity. Additional experiments can be performed to determine the optimum viscosity, retraction rate, solids content and temperature to achieve the desired thickness.

Typically, the dielectric material is a polymeric resin material used in the manufacture of PCBs. Such polymer resins include epoxy resins such as epoxy / glass, bi- and polyfunctional epoxy resins, bimaleimide / triazines and epoxy resins (BT epoxy), epoxy / polyphenylene oxide resins, acrylonitrile Butadienestyrene, polycarbonate (PC), polyphenylene oxide (PPO), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polysulfone (PS), polyamide, polyethylene terephthalate (PET) and poly Polytetra, such as polyester with butylene terephthalate (PBT), polyetheretherketone (PEEK), liquid crystalline polymers, polyurethanes, polyetherimides, polyphenylene oxides and cyanate esters and composites thereof Fluoroethylene (PTFE) and polytetrafluoroethylene blends, including but not limited to. Such polymeric resin materials can have high or low T _g . High T _g polymer resin is a resin having a T _g above 160 ℃ as 160 ℃ to 280 ℃ or 170 ℃ to 240 ℃.

After the solution is coated on the dielectric substrate, it is dried to form a very smooth surface. Drying is done by placing the dielectric in a conventional convection oven or by infrared drying, such as a custom designed conformal coating infrared oven from Glenro with an overhead conveyor. It can be performed using a system. Drying is carried out in a temperature range of 70 ° C to 110 ° C. Drying times range from 30 minutes to 60 minutes. The coating thickness of the dried adhesive composition may vary. Typically, the thickness of the dried adhesive composition coating ranges from 0.2 μm to 100 μm, such as 10 μm to 50 μm.

After the dielectric is dried, it is treated with a promoter. Desmear with solvent swell used in many conventional processes is excluded. Conventional promoters can be used. Such promoters include sulfuric acid, chromic acid, alkaline permanganate or plasma etching. Typically alkaline permanganate is used as a promoter. An example of a commercially available promoter is CIRCUPOSIT PROMOTER ™ 4130 from Rohm and Haas Electronic Materials (Marlborough, Mass.). Typically the promoter is applied at 50 ° C to 100 ° C. Optionally, the dielectric substrate is rinsed with water.

The neutralizer is then applied to the genome to neutralize any acidic or basic residues left by the promoter. Conventional neutralizing agents can be used. Typically, the neutralizer is an alkaline aqueous solution containing at least one amine or 3 wt% peroxide and 3 wt% sulfuric acid solution. Typically, the neutralizing agent is applied at 30 ° C to 80 ° C. Optionally rinse the substrate with water.

An acidic or alkaline conditioner is applied to the dielectric substrate. Conventional conditioners may be used. Such conditioners include one or more cationic surfactants, non-ionic surfactants, complexing agents and pH adjusters or buffers. Commercially available acid conditioners include, but are not limited to, CIRCUPOSIT CONDITIONER ™ 3320 and CIRCOPOSIT CONDITIONER ™ 3327 from Rohm and Haas Electric Materials (Marlbourough, MA). Suitable alkaline conditioners include, but are not limited to, alkaline aqueous surfactant solutions containing one or more quaternary amines and polymers. Commercially available alkaline surfactants include, but are not limited to, CIRCUPOSIT CONDITIONER ™ 231, 3325, 813 and 860 from Rohm and Haas Electric Materials. The dielectric is conditioned at 30 ° C. to 70 ° C. for 5 to 10 minutes. Optionally, the dielectric is rinsed with water.

If a metal pad, such as a copper pad, is included in the dielectric substrate, then it is conditioned by microetching, otherwise this step is not performed. Conventional microetching compositions can be used. Microetching includes, but is not limited to, 60 g / L to 120 g / L sodium persulfate or sodium or potassium oxymonopersulfate and sulfuric acid (2%) mixture, or generic sulfuric acid / hydrogen peroxide. An example of a commercially available microetching composition is CIRCUPOSIT MICROETCH ™ 3330 from Rohm and Haas Electric Materials.

Thereafter, pre-dip is applied to the dielectric. Examples of pre-immersion include acidic solutions of 2% to 5% hydrochloric acid or 25g / L to 75g / L sodium chloride. Optionally, the dielectric is rinsed with cold water.

The catalyst is then applied to the treated surface of the dielectric. Any conventional catalyst can be used. The choice of catalyst depends on the type of metal to be deposited on the surface of the dielectric. Typically, the catalyst is a colloid of noble and non-noble metals. Such catalysts are well known in the art and many catalysts are commercially available or can be prepared with reference to the literature. Examples of non-noble metal catalysts include copper, aluminum, cobalt, nickel, tin and iron. Typically precious metal catalysts are used. Suitable precious metal colloidal catalysts include, for example, gold, silver, platinum, palladium, iridium, rhodium, ruthenium and osmium. More typically, silver, platinum, gold and palladium catalysts are used. Most typically silver and palladium are used.

Commercially available catalysts include, for example, CIRCUPOSIT CATALYST ™ 334 and CATAPOSIT ™ 44 from Rohm and Haas Electric Materials. The catalyst is applied to the dielectric for 5-10 minutes at 30 ° C to 90 ° C. Optionally rinse the substrate with water.

The dielectric is then plated using a conventional electroless metal bath. Conventional electroless baths can be used including immersion baths and conventional plating parameters. Typically, the dielectric is placed in an electroless or metal bath containing metal ions of the metal to be deposited. Metals that can be deposited include, but are not limited to, copper, nickel, gold, silver and copper / nickel alloys. Typically, copper is plated on the dielectric surface. A commercial electroless copper plating bath is the CIRCUPOSIT ™ 880 Electroless Copper Plating bath from Rohm and Haas Electric Materials, LLC. Typically, electroless plating is performed in a temperature range of 25 ° C. to 60 ° C. Typically, electroless plating is performed until the thin film metal layer is 0.5 to 5 mm thick. Optionally, gold or silver plating may be used to deposit a gold or silver finish layer over copper, copper / nickel or nickel deposition.

After the metal is deposited, the optionally metal plated dielectric or composite is rinsed with water. Optionally, anti-tarnish agents may be applied to the metal. Conventional discoloration agents can be used. Examples of anti-tarnish agents are ANTITARNISH ™ 7130 and CUPRATEC ™ 3 (from Rohm and Haas Electric Materials).

In one embodiment, a metal plated dielectric or composite is placed between the plates of a hot platen and annealed to fully cure the amine and epoxy compounds, forming a generally smooth adhesive layer at the interface of the metal and dielectric. Annealing is carried out for 30 minutes to 60 minutes at 150 ℃ to 200 ℃, such as 160 ℃ to 190 ℃. While not theoretically supported, the annealing process causes the epoxy, amine, and all hydroxyl or other reactive functional groups of the dielectric material to cure, forming chemical bonds between the metal thin film and the dielectric material, increasing adhesion between the metal and the dielectric. . Thereafter, the entire metal plating process was performed as described below.

In another embodiment, the dielectric with the metal thin film is left at room temperature for at least one day prior to the annealing and the entire metal plating process, or the composite is heated between 30 and 60 minutes between plates of the hot plate to partially cure the amine and epoxy compounds of the solution. You can. Heating is carried out at a temperature of 70 ° C to 100 ° C.

In another embodiment, the entire metal plating process can be performed prior to annealing. This overall plating process may include conventional lithography processes such as photoimaging using photoresist to form circuit patterns in the thin film metal layer. Thereafter, selective metal deposition is performed on the circuit pattern of the composite metal surface. Typically, metal deposition is performed, for example, by electrolytic metal plating of copper, copper alloys, tin and tin alloys. Such methods are conventional and are well known in the art. Typically, copper is metal plated to the circuit pattern.

In the electrolytic plating process, the composite is used as a cathode. Conventional soluble or insoluble anodes may be used as the secondary electrode. Conventional rectifiers are used as current sources. Pulse plating or direct current (DC) plating or a process combining DC and pulse plating can be used. Such plating is known in the art. Current density and electrode surface potential can vary depending on the particular substrate to be deposited. In general, the current density is between 0.1 ASD and 20 ASD. The electroplating bath is maintained in the temperature range 20 ° C. to 110 ° C. The temperature range depends on the specific metal. The copper bath is maintained at 20 ° C. to 80 ° C., and the acid copper bath is maintained at a temperature range of 20 ° C. to 50 ° C. Electrolytic plating is performed for a time sufficient to form a deposition of the desired thickness. After electrolytic plating, the composite substrate is rinsed with water. The annealing is then performed on the composite substrate to improve metal deposition and adhesion between the dielectrics.

Thereafter, the composite may be cut to the desired size and conventional processes such as the formation of through holes or vias may be performed. They may be formed by drilling or punching or by any other method known in the art. Thereafter, through-holes or vias are desmeared using conventional processes and then plated. Additional processes may be performed to form completed printed circuit boards or other electrical components and devices.

The method of the present invention enables the formation of chemical bonds between the dielectric substrate and the metal layer, in contrast to the typical mechanical bonds in conventional bonding methods for bonding metal to the dielectric. Most of the micro-concave-convexities of the dielectric surface are removed, and the very smooth surface evens out the current flow of current lines and other essential features of the electrical device and improves its electrical performance. In addition, finer line networks are made possible by smoother surfaces, which allows for smaller devices.

1 is a FR4 epoxy / glass panel surface before adhesive solution application and 1050X SEM after adhesive solution application.
2 is a graph of peel strength for six adhesive solutions with different amine to epoxy mass ratios.
FIG. 3 is a 10,000 × SEM of FR4 epoxy / glass panel cross-section showing the interface between the plated copper and epoxy / glass panels of the untreated and treated solutions.

The following examples are intended to illustrate the invention in detail and do not limit the scope of the invention.

Examples 1-8

Eight adhesion promoting solutions were prepared as shown in Table 1 below.

Eight FR4 epoxy / glass substrates were obtained from Isola Laminate Systems Corp., LaCrosse Wisconsin. Each substrate was treated according to the following method.

1. Each substrate was first washed in advance using a conventional acetone cleaner.

2. Each substrate was then dip coated with a bench top dip lab coater at room temperature for 1 minute with one of the adhesion promoting solutions of Table 1.

3. Each substrate was then dried at 100 ° C. for 60 minutes in a custom designed conformal coating infrared oven from Glenro with an overhead conveyor. The thickness of the dried contact promotion composition is 4 μm to 5 μm. 1 shows the surface of the FR4 epoxy / glass substrate after drying, before application of the contact promotion solution and after application of the contact promotion solution. The surface of the substrate after application of the contact facilitating solution has a smooth surface in contrast to the same substrate before the contact facilitating solution only.

4. Each contact-coated substrate was then treated with a surface at 80 ° C. for 7 minutes with an alkaline promoter solution of aqueous alkaline permanganate at pH 12.

5. The substrate was rinsed with cold water.

6. The through-holes of the substrate were then treated with 180 liters of 180 liters of an aqueous neutralizer consisting of 3 wt% hydrogen peroxide and 3 wt% sulfuric acid.

7. The substrate was then rinsed with cold water.

8. Each substrate was then treated with CIRCUPOSIT CONDITIONER ™ 3320 acidic aqueous conditioner at 40 ° C. for 5 minutes.

9. Each substrate was rinsed with cold water.

10. Then, pre-immersion was applied to the surface of each substrate at room temperature for 40 seconds. Pre-immersion contained 5% concentrated hydrochloric acid.

11. The substrate was then primed for 5 minutes at 40 ° C. with an aqueous catalyst solution for electroless copper metallization.

12. The board was then rinsed with cold water.

13. The surface of the substrate was then plated with electroless copper by immersing each board in 1000 liters of electroless copper bath for 8 minutes at 36 ° C. The electroless copper bath has the following composition:

14. After electroless copper deposition, the substrate was rinsed with cold water.

15. Subsequently, each substrate was annealed back in a conventional oven at 160 ° C. for 60 minutes.

16. Each substrate was then cooled to room temperature and the peel strength of each copper substrate was tested using a Tensile Tester A tensile strength tester. Peel strength is reported in Table 4 below.

As shown in FIG. 2, the results are plotted in a graph of peel strength vs. amine parts for one part epoxy. Peel strength increased from 0.41 kg / cm to 0.47 kg / cm when the amine to epoxy was 1: 1 to 4: 1 parts by weight. When the amount of amine to epoxy exceeded the 4: 1 weight ratio, the peel strength dropped to 0.4 kg / cm, an unacceptable level.

Example 9

The following adhesion promoting solution was prepared.

Two FR4 epoxy / glass substrates were obtained from Isola Laminate Systems Corp., LaCrosse Wisconsin. The first substrate was treated with the adhesion promoting solution of Table 5 as described in Example 1. The second substrate was not treated with any adhesion promoting solution. Thereafter, each substrate was prepared and plated as described in Example 1.

Each substrate was then cut in the middle to obtain a cross section showing the interface of copper deposition and epoxy / glass. 3 is a 10,000 × SEM of each substrate cross section showing the interface of copper deposition and epoxy / glass as indicated by the arrows. The substrate treated with the adhesion promoting solution of Table 5 had a much smoother surface than the surface of the substrate not treated with the solution.

Example 10

The following adhesion promoting solution was prepared.

FR4 epoxy / glass substrates were obtained from Isola Laminate Systems Corp., LaCrosse Wisconsin. The substrate was treated with the adhesion promoting solution of Table 6 as described in Example 1. Thereafter, it was prepared as described in Example 1 and plated with electroless copper.

The substrate was then cut in the middle to obtain a cross section showing the interface of copper deposition and epoxy / glass. The interface of copper and epoxy / glass is expected to have a cross section substantially the same as that of the substrate having the coated interface of FIG. 3.

Example 11

The following adhesion promoting solution was prepared.

FR4 epoxy / glass substrates were obtained from Isola Laminate Systems Corp., LaCrosse Wisconsin. The substrate was treated with the adhesion promoting solution of Table 7 as described in Example 1. The substrate was then prepared as described in Example 1 and plated with electroless copper.

The substrate was then cut in the middle to obtain a cross section showing the interface of copper deposition and epoxy / glass. The interface of copper and epoxy / glass is expected to have a cross section substantially the same as that of the substrate having the coated interface of FIG. 3.

Claims (10)

a) providing a dielectric substrate;
b) applying a solution comprising at least one curable amine compound and at least one curable epoxy compound adjacent to the surface of the dielectric substrate, wherein the solution comprises an excess of at least one curable amine in excess of the at least one curable epoxy compound. Processing;
c) drying the solution adjacent the treated surface of the dielectric substrate;
d) electroless plating a metal on the treated surface of the dielectric substrate; And
e) heating the metal plated dielectric substrate to cure one or more amine compounds and one or more epoxy compounds. The method of claim 1, further comprising selectively electroplating a metal layer onto the electroless plated metal prior to step e). The method of claim 1, further comprising: applying a promoter to the treated dielectric surface after step c) and before step d); Applying a neutralizer to the treated dielectric surface; Conditioning the treated dielectric surface; Applying a pre-dip to the treated dielectric surface; And applying a catalyst to the treated dielectric surface. The method of claim 1 wherein the weight ratio of the at least one curable amine compound to the at least one epoxy compound is at least 2: 1. The method of claim 4 wherein the weight ratio of the at least one curable amine compound to the at least one epoxy compound is from 2: 1 to 4: 1. The method of claim 1 wherein the solution further comprises one or more surfactants. The method of claim 1 wherein the solution comprises one or more curing accelerators. The method of claim 1, wherein the at least one curable amine compound is a polyamine compound selected from aliphatic, cycloaliphatic, aromatic cycloaliphatic and aromatic polyamines. The method of claim 1, wherein the at least one curable epoxy compound is selected from glycidyl ethers, glycidyl esters, polyfunctional di- and triglycidyl ethers, bisphenolic epoxy and novolac epoxy compounds. The dielectric substrate of claim 1, wherein the dielectric substrate is an epoxy resin, acrylonitrile butadiene styrene, polycarbonate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, polysulfone, polyamide, polyester, polybutylene terephthalate , Polyetheretherketone, liquid crystal polymer, polyurethane, polyetherimide, polytetrafluoroethylene, polytetrafluoroethylene blend, cyanate esters and composites thereof.

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