Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/04—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the partial melting of at least one layer
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/241—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres
  • C08J5/242—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres using metal fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B15/00—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00
  • B29B15/08—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 of reinforcements or fillers
  • B29B15/10—Coating or impregnating independently of the moulding or shaping step
  • B29B15/12—Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
  • B32B15/082—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising vinyl resins; comprising acrylic resins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
  • B32B15/085—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/22—Layered products comprising a layer of synthetic resin characterised by the use of special additives using plasticisers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/26—Layered products comprising a layer of synthetic resin characterised by the use of special additives using curing agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
  • B32B27/322—Layered products comprising a layer of synthetic resin comprising polyolefins comprising halogenated polyolefins, e.g. PTFE
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
  • B32B37/24—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/241—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres
  • C08J5/244—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres using glass fibres
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/249—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs characterised by the additives used in the prepolymer mixture
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2250/00—Layers arrangement
  • B32B2250/02—2 layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0261—Polyamide fibres
  • B32B2262/0269—Aromatic polyamide fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/10—Inorganic fibres
  • B32B2262/101—Glass fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/10—Inorganic fibres
  • B32B2262/105—Ceramic fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/10—Inorganic fibres
  • B32B2262/106—Carbon fibres, e.g. graphite fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
  • B32B2307/202—Conductive
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
  • B32B2307/208—Magnetic, paramagnetic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/31—Heat sealable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
  • B32B2307/406—Bright, glossy, shiny surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2457/00—Electrical equipment
  • B32B2457/08—PCBs, i.e. printed circuit boards
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/0313—Organic insulating material
  • H05K1/0353—Organic insulating material consisting of two or more materials, e.g. two or more polymers, polymer + filler, + reinforcement
  • H05K1/0366—Organic insulating material consisting of two or more materials, e.g. two or more polymers, polymer + filler, + reinforcement reinforced, e.g. by fibres, fabrics
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
  • H05K3/022—Processes for manufacturing precursors of printed circuits, i.e. copper-clad substrates

Definitions

• the invention relates to a process for the preparation of a fibre-reinforced resin- coated sheet.
• layers having a different thickness plays an important role in the production of printed circuit boards.
• copper foils are coated with epoxy resin compositions dissolved in solvents and subsequently the solvent is evaporated.
• the sheets obtained thereby are then laminated under pressure on already structured so-called inner layers under vacuum (US 5,718,039, US 6,187,416, EP 1 108 532 A1).
• a further example is the application of a solder mask on the final printed circuit board.
• the corresponding compositions also con ⁇ tain solvents that need to be removed by heat (EP 0 323 563 A2).
• the preparation of prepregs is done by applying resin compositions to glass fabric in specific coating units called treaters.
• the fabric is transported on rolls and is dipped first in a solution of the resin to be applied in an organic solvent and subsequently passed through a long (vertically) arranged oven so that the sol ⁇ vent is uniformly evaporated from both sides.
• the thinnest commercially available prepreg has a thickness of 50 ⁇ m.
• the solvent-based processes are disadvantageous in that they require a large amount of energy to evaporate the solvent, they are harmful to the environment, they require sophisticated industrial hygiene, the solvents are combustible, waste disposal is complicated and entails additional considerable costs.
• the process should result in a uniform layer thickness.
• the process should allow the use of very thin fibre-reinforced materials without the oc ⁇ currence of a partial or complete destruction of the fabric.
• the component layers in the preparation of printed circuit boards comprising resin/glass fi- b re/copper-composites should become thinner and lighter.
• the process should provide a fibre-reinforced resin-coated copper sheet enabling a faster laser drilling in the preparation of printed circuit boards, thus resulting in an increased production efficiency, since more holes can be drilled per time unit with the same capacity of laser drillers.
• the invention relates to a process for the solvent-free preparation of a fibre-reinforced resin-coated sheet comprising the following steps:
• glass fibres or high-performance fibres are used as fibre-reinforced sub- strate material.
• Preferred high-performance fibres are aramide fibres, carbon fibres and ceramic fibres.
• very thin woven fabric or mats consisting of glass or high-performance fibres can be used.
• their thick ⁇ ness is 5-200 ⁇ m and preferably 15-80 ⁇ m.
• lay ⁇ ers having a thickness of 60 ⁇ m can be obtained by the process according to the present invention, the difference in thickness throughout the layer being ⁇ 15%, preferably ⁇ 10% and most preferably ⁇ 5%.
• the so-called electromagnetic brush is used and the process is based on a principle which is used, in similar form, with laser printers and copying machines.
• the invention is based on the surprising finding that the filler particles of the composition or formulation are distributed within the fabric in an entirely uni ⁇ form way, i.e., they do not "stick" to the surface.
• the powder to be applied is mixed with the carrier particles or so-called carriers in a container.
• These carriers consist of a magnetic core having a polymeric coating.
• the powder can be electrostatically charged by means of several rollers whereby it sticks to the carriers.
• the powder By means of mixing rolls the powder is continuously trans ⁇ ported together with the carriers to the so-called brush roll which is provided with magnets in its interior.
• the transport to the brush drum can be done by a fluidized bed.
• the magnetic carrier particles together with the powder adher ⁇ ing to them adhere now to the brush drum.
• the powder particles Upon application of a corresponding voltage between the brush drum and the substrate drum, the powder particles are transferred to the substrate (for example, a fabric/metal foil sandwich), whereas the carrier particles remain in the system. This way, uniform thick layers can be applied onto a substrate.
• Figure 1 schematically describes a coating unit having mixing drums.
• the carrier and power are mixed in the container (10). Thereby the powder is charged and adheres to the oppositely charged carriers.
• the transport to the brush drum (1) is made by the mixing rolls (4).
• the mixing rolls or mixing drums, respectively, may have magnets in their interior. Alternatively, they have wings or paddles on the outside. These serve to mix the carriers and the powder or coating powder, re ⁇ spectively.
• the mixing rolls transport the particles to the brush drum (1 ).
• the brush drum has magnets in its interior.
• the substrate for example, a copper sheet
• the substrate must be a discharging substrate.
• Figure 1 further shows a heating device (7) for melting the coating powder and for sintering the powder, respectively.
• Figure 2 shows a modification comprising a fluid ized bed:
• the mixing rolls (3) shown in Figure 1 are replaced with a fluidized bed (represented in Figure 2 by dots).
• the fluidized bed is generated by blowing air into the mixture of carriers and powder or coating powder, respectively, which fluidized bed mixes and thus causes an opposite electrostatic charge of the carriers and the powder.
• the transport to the brush drum is made.
• the particle size of the coating powder is in general ⁇ 150 ⁇ m and preferably ⁇ 100 ⁇ m and most preferably ⁇ 50 ⁇ m.
• the size of the carrier particles is in general 10-150 ⁇ m and preferably 20-100 ⁇ m.
• a curable coating powder is pref ⁇ erably used which comprises particles obtainab Ie by
• the coating powder has a glass transition temperature in the uncured state of at least 2O°C, preferably at least 25°C and more preferably at least 3O 0 C and has a glass transition tempera ⁇ ture in the cured state of at least 150 0 C 1 preferably at least 160 0 C and more pref ⁇ erably at least 170°C.
• curing is preferably made up to a degree of 1 to 70%, preferably 10 to 50% (as measured by DSC).
• the polymeric binder is preferably essentially an epoxy resin which is solid at room temperature.
• the glass transition temperature of the resin should preferably be at least 25°C.
• the coating powder used in the invention can preferably also comprise a mixture of epoxy resins.
• This mixture preferably has a glass transition temperature of > 25 0 C in the uncured state. Its molecular weight (number average molecular weight) is generally > 600.
• Suitable epoxy resins for the preparation of the coating powder used in the inven ⁇ tion are described, for example, in: Clayton A. May (Ed.) Epoxy Resins: Chemistry and Technology, 2nd ed., Marcel Dekker Inc., New York, 1988.
• Preferred mixtures of epoxy resins on the basis of bisphenol A and bisphenol A diglycidyl ether.
• the epoxy equivalent weight of these resins is > 300 g/equivalent.
• Such a resin is, for example, D.E.R. 6508 (available from Dow Chemicals).
• Epoxy resins on the basis of bisphenol F and bisphenol S can optionally also be added.
• the mixture can comprise multifunctional epoxy resins.
• the function ⁇ ality of these resins is > 3.
• Examples for such multifunctional epoxy resins are ere- sol-novolak epoxy, phenol-novolak epoxy and naphthol-containing multifu notional epoxy resins.
• Examples for the aforementioned epoxy resins are bisphenol A epoxy resin such as D.E.R. 667-20, D.E.R. 663UE, D.E.R. 692H, D.E.R. 692, D.E.R. 662E, D.E.R. 6508, D.E.R.
• cresol-novolak epoxy res ⁇ ins such as Araldite ECN 1299, Araldite ECN 1280 (Vantico), EOCN-103 S, EOCN-104, NC-3000, EPPN 201 , EPPN-502 H (Nippon Kayaku), naphthol epoxy resins such as NC 7000-L (Nippon Kayaku) and brominated Epoxy resins such as Araldite 8010 (Vantico), BREN-S (Nippon Kayaku), ESB-400 T (Sumitomo) and Epikote 5051 (Resolution).
• modified epoxy resins can also be used. Such modifications are, for example, the use of chain reaction terminating agents to control the molecular weight, so-called ,,high-flow" resins, and the use of multi ⁇ functional monomers to prepare branched resins.
• a particularly preferred coating powder used in the invention comprises, as com- ponent (a), about 50-90 wt.-% of epoxide and about 5-20 wt.-% of cyanate ester, as component (b), about 0.5-5 wt.-% of dicyandiamide and about 0.1-2 ⁇ vt.-% of 2- phenylimidazole, for example about 85 wt.-% of epoxide, 10 wt.-% of cyanate es ⁇ ter, about 2 wt.-% of dicyandiamide as hardener and about 1 wt.-% of 2- phenylimidazole as initiator.
• cyanate esters can also be used as polymeric binders. In the preparation of the coating powder used in the invention, these can be used both in monomeric form as well as in the fo rm of oli ⁇ gomers or prepolymers.
• Suitable cyanate esters are bifunctional cyanate esters, such as BADCy, Primaset Fluorocy, Primaset MethylCy, or multifunctional cyanate esters, such as Primaset BA-200, Primaset PT 60, Primaset CT 90, Primaset PT 30. All of the aforemen ⁇ tioned bifunctional and multifunctional cyanate esters are available from Lonza, Basel, Switzerland. Especially preferred cyanate esters are BADCy and its prepolymers (e.g. Primaset BA-200).
• the component (a) can also comprise 1-oxa-3-aza- tetralin-containing compounds (oxazine resins). In the preparation of the coating powder used in the invention, these are also initially employed in monomeric form.
• Preferred oxazine resins are those which are obtained either by reacting bisphenol A with aniline and formaldehyde or by reacting 4,4'-diaminodiphenyl methane with phenol and formaldehyde. Further examples may be found in WO 02/072655 and EP 0 493 310 A1 as well as in WO 02/055603 and the Japanese patent applica- tions JP 2001-48536, JP 2000-358678, JP 2000-255897, JP 2000-231515, JP 2000-123496, JP 1999-373382, JP 1999-310113 and JP 1999-307512.
• maleimides used in the preparation of the coating powder of the invention are also known per se to the skilled person and are described, for example, in Shiow- Ching Lin, EIi M. Pearce, High-Performance Thermosets, Carl Hanser Verlag, Mu ⁇ nich 1994, Chapter 2.
• the component (b) of the resin composition used in the invention comprises a hardener or initiator.
• hardeners and initiators are known per se to the skilled person and comprise latent hardeners with low activity at room temperature, such as phenolic hardeners, such as D.E.H. 90, D.E.H. 87, D.E.H. 85, D.E.H. 84, D.E.H.
• dicyandiamide or derivatives thereof such as Dyhard OTB, Dyhard UR 200, Dyhard UR 300, Dyhard UR 500, Dygard 100, Dyhard 100 S, Dyhard 100 SF and Dyhard 100 SH (available from Degussa, Germany), bisphenol A, acid anhydrides, such as phthalic acid anhy ⁇ dride, tetrahydrophthalic acid anhydride, trimellitic acid anhydride, pyromellitic acid anhydride, hexahydrophthalic acid anhydride, HET-acid anhydride, dodecenyl succinic acid anhydride, bicyclo[2.2.1]hept-5-en-2,3-dicarboxylic acid anhydride, aromatic and aliphatic amines, such as diaminodiphenylsuifone, diaminodiphenylether, diaminodiphenylmethane or ring-substituted dianilines,
• dicyandiamide or modified dicyandiamide is employed.
• the hardeners or initiators are used in an amount of below 10 wt.-%, preferably below 5 wt.-% (lower limit: about 0.1 wt.-%).
• Preferred initiators are imidazoles and derivatives thereof, such as 2- methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4- methylimidazole, bis(2-ethyl-4-methylimidazole), 2-undecylimidazole, 2,4-diamino- 6(2'-methyl-imidazole(1 '))ethyl-s-triazine and 1-cyanoethyl-2-undecylimidazole.
• salts formed from imidazoles and carboxylic acids can be used.
• Fur- ther initiators are 1 ,8-diaza-bicyclo(5.4.0)undecene (DBU) and boron-trihalide- amine complexes, such as BF3-amine. Further examples may be found in Clayton A. May (Ed.) Epoxy Resins: Chemistry and Technology, 2nd ed., Marcel Dekker Inc., New York, 1988.
• DBU 1 ,8-diaza-bicyclo(5.4.0)undecene
• boron-trihalide- amine complexes such as BF3-amine.
• the resin composition used in the invention further comprises coating additives as component (c).
• coating additives comprise flow-control agents, degassing agents and lubri ⁇ cants. These are known per se to the skilled person. Typical examples are butyl acrylate polymers as flow-control agents, benzoin as degassing agents and waxes as lubricants. Furthermore, for example stabilizers can be used as coating addi ⁇ tives.
• the resin composition used in the invention contains the coating additives in an amount of generally 0.1-10 wt.-%, preferably 0.2-5 wt.-%.
• Coating additives also comprise adhesion promoters. These are useful for provid ⁇ ing adhesion to the copper substrate.
• the coating powder used in the invention may further comprise organic and inor ⁇ ganic fillers (d).
• fillers are suitably employed in the coating powder used in the invention in an amount of 5 to 300 wt.-%, preferably 10 to 200 wt.-%, more preferably 10 to 100 wt-%.
• the stated amounts relate to the sum of components (a), (b) and (c) of the coating powder.
• organic fillers are fluorine containing polymers, such as polytetra- fluoroethylene (PTFE), tetrafiuoroethylene/hexafluoropropylene copolymer (FEP), tetrafluoroethylene/ethylene copolymer (E/TFE), tetrafluoroethylene/hexafluoro- propylene/vinylidene fluoride terpolymer (THV), poly(trifluorochloroethylene)
• PTFE polytetra- fluoroethylene
• FEP tetrafiuoroethylene/hexafluoropropylene copolymer
• E/TFE tetrafluoroethylene/ethylene copolymer
• TSV tetrafluoroethylene/hexafluoro- propylene/vinylidene fluoride terpolymer
• TSV tetrafluoroethylene/hexafluoro- propylene/vinylidene fluoride terpol
• PCTFE trifluorochloroethylene/ethylene copolymer
• E/CTFE trifluorochloroethylene/ethylene copolymer
• PVDF polyvinylidene fluoride
• PVDF poly(vinylidene fluoride)
• PFA perfluoroalkoxy copolymer
• MFA tetra- fluoroethylene/perfluoromethyfvinylether copolymer
• PVC vinyl chloride
• PPO polyphenyl ether
• PSU polysulfone
• PSU polyaryl ether sulfon
• PPS polyphenyl ether sulfon
• PPS polyphenylene sulfide
• PEK polyether ketone
• PEI polyether imide
• Especially preferred organic fillers are tetrafluoroethylene/hexafluoropropylene copolymer (FEP), ethylenetetrafluoroethylene copolymer (ETFE) and polyphenyl ether (PPO).
• FEP tetrafluoroethylene/hexafluoropropylene copolymer
• ETFE ethylenetetrafluoroethylene copolymer
• PPO polyphenyl ether
• the coating powder used in the invention there may preferably be used organic fillers which do not melt upon processing. Alternatively, there can be used fillers which melt and show phase separation upon cooling.
• inorganic fillers may also be used in the coating powder.
• Such fillers are, for example, fused silica, such as Silbond 800 EST, Silbond 800 AST, Silbond 800 TST, Silbond 800 VST 1 Silbond 600 EST, Silbond 600 AST, Sil ⁇ bond 600 TST, Silbond 600 VST (available from Quarzwerke Frechen, Germany), fumed silica, such as Aerosil 300 and Aerosil R 972, precipitated silica, such as Ultrasil 360, Sipemat D 10, Sipemat 320 (available from Degussa, Germany), cal ⁇ cined kaolin, such as PoleStar (Imerys, St Austell, UK), Santintone (Engelhard Corporation, Iselin, NJ, US), aluminium oxide, magnesium oxide, zirconium oxide, aluminium silicates, calcium carbonate and barium sulfate, silica glass and kaolin being preferred fillers. Furthermore, there may be mentioned ceramics, especially those with low or negative coefficients of expansion.
• the advantages of the coating powder used in the invention are that it is possible, in order to optimise the properties of the product, to select from a variety of fillers the one which best satisfies the relevant requirements. For example, a given ep- oxy resin mixture can, thus, be modified as needed. Even fillers which are difficult to process can be incorporated without problems.
• electric properties such as the dielectric constant (DR), the dielectric loss factor (tan ⁇ ), the breakdown resis ⁇ tance, the surface resistance, the volume resistance and mechanical properties such as bending strength, impact strength, tensile strength as well as further mate- rial properties such as the coefficient of thermal expansion (CTE), fiammability and others can be adapted as desired.
• the filler does not have to be solvable or stably dispersable in organic solvents. Consequently, it is possible to use materials as fillers which could previously not or only hardly be used in sequential build-up (SBU), such as the aforementioned organic fillers.
• SBU sequential build-up
• the electrical and mechanical properties of the coating powder and of the coating layer prepared therefrom can be influenced and controlled by the fillers.
• fillers with a low dielectric constant such as PTFE, FEP and kaolin may be employed in order to prepare coating layers with a correspondingly low dielectric constant.
• the mechanical properties which can be influenced by the fillers comprise, in par ⁇ ticular, properties such as the coefficient of thermal expansion, impact strength, and tensile strength.
• the following fillers are particularly suitable for controlling the coefficient of thermal expansion: silica glass, kaolin, calcium carbonate and ceramics with a negative coefficient of expansion.
• Bending strength can be influenced or controlled, for example, by PPO.
• the cured coating powder has a coefficient of thermal expansion (CTE) of ⁇ 70 ppm/°C and preferably ⁇ 60 ppm/°C in the x-, y- and z-direction.
• CTE coefficient of thermal expansion
• the dielectric constant of the coating in the cured state is ⁇ 3.8, preferably ⁇ 3.6.
• glass transition tempera- tures of the cured formulation of above 150 0 C, preferably above 16O 0 C, are pre ⁇ ferred.
• flame-retard ant materials may be used as fillers.
• inorganic materials which release water upon heating such as aluminium hy ⁇ droxide, which is available, for example, as Martinal OL-104, Martinal OL-111 (Martinstechnik GmbH, Bergheim, Germany) or Apyral 60 D (Nabaltec, Schwandorf, Germany), magnesium hydroxide, available, for example, as magnesium hydrox ⁇ ide 8814 (Martinswek GmbH, Bergheim, Germany) or Mg-hydroxide SIM 2.2 (Scheruhn Industrie-Mineralien, Hof, Germany), phosphorous-containing organic compounds, such as triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate (CDP), tertiary phosphin oxides, such as Cyagard ® and Re- oflam ® 410, red phosphorous in the form of a dispersion in an epoxy resin, such as Exolit
• the flammability of the coating powder of the invention can be influ- enced and controlled by component (c), i.e., the coating additives.
• component (c) i.e., the coating additives.
• component (c) i.e., the coating additives.
• phosphorous-containing and nitrogen-containing flame retar- dants may be mentioned.
• the coating powder of the invention can, optionally, further contain compatibilizing polymers.
• compatibilizing polymers are, for example, di- ortriblock copoly ⁇ mers such as styrene/butadiene/styrene or styrene/butadiene/methyl methacrylate blockcopolymers (Atofina, France).
• the coating powder used in the invention can contain conventional additives which are conventionally used in the processing of epoxy resins.
• the components (a), (b), (c) and, optionally, (d) and (e) are first dry-milled to give a powder.
• This procedure must be used, in particular, when certain components are difficult to incorporate. These are then incorporated into each other beforehand.
• Such master batches are also commercially available.
• the resins for example, it is possible to mix two resins beforehand. This course of ac- tion is used, in particular, when one of the resins has a low glass transition tem ⁇ perature.
• this procedure may be used when certain components are used only in small amounts.
• the aforementioned components or master batches are premixed and milled in the dry state. Before milling, the mixture may optionally be cooled.
• the material is milled in the dry state and the oversize material is separated, wherein a sieve size in the range of less than 10 to 500 ⁇ m and pref ⁇ erably less than 100 ⁇ m is suitably used, which guarantees a corresponding parti ⁇ cle size.
• Classifying mills such as Hosekawa MicroPul are particularly suitable for milling.
• the aforementioned melt extrusion is preferably carried out in such a way that the conversion of the reactive component is less than 20%, preferably less than 10%. This reaction is due to the fact that a melt is formed upon extrusion.
• the degree of conversion can be determined by the skilled person by thermal analysis.
• the cor- responding extrusion parameters (for obtaining such a degree of conversion) can be determined by the skilled person by simple experiments.
• the final coating powder mixtures preferably have an average particle size in the range of 1 to 500 ⁇ m, especially of 10 to 100 ⁇ m.
• the coating powder which are produced in this way are used in the process ac ⁇ cording to the present invention for the preparation of a fibre-reinforced resin coated copper sheet for use in the production of printed circuit boards.
• step (ii) of the process according to the pre ⁇ sent invention for melting
• NIR near infrared
• the melting is preferably be effected by NIR. This method is described in WO 99/47276, DE 10109847, in Kunststoffe (1999), 89 (6), 62-64 and in Journal fur Oberflach ⁇ ntechnik (1998), 38 (2), 26-29.
• the step of melting is particularly important. Upon heating, a change in viscosity occurs, i.e., the powder first melts. The viscosity of the melt decreases initially. Subsequently, curing and, thus, a rise in viscosity takes place. This operation must be conducted in the process of the invention in such a way that the viscosity of the melt is initially as low as possible and subsequently good flow is achieved without formation of bubbles, such that a non-porous film is obtained.
• the coating layer is first melted, remains flowable and can, hence, be used for the preparation of a multilayer structure by:
• step (iv) An essential feature of this process is that curing occurs mainly in step (iv), i.e., after the preparation of the multilayer structure. In this connection, it is important that the films are still flowable during the formation of the structure.
• the curing of the melted powder coated layers takes place during pressing or lamination.
• the pressing or lamination takes place under vacuum and pressure, the corresponding parameters being known to the skilled person.
• a Lauffer press or an Adara press can be used.
• the pressing cycles are to be adap ⁇ ted to the individual material used.
• step (i) the intimate contact between the substrate and the sheet is achieved by depositing the coating powder prior to step (i) on the sheet by methods known per se (powder spraying, powder cloud, electromagnetic brush) to obtain a powder-coated sheet, melting the obtained powder-coating by applying heat to the powder coated sheet, applying the substrate on this coated sheet to obtain a sandwich-like structure, optionally, coat this sandwich-like structure for a second time with coating powder followed by melting and laminating this sand- wich-like structure to form a substrate laminate comprising the substrate and the sheet.
• the coating powder is deposited on the sheet (such as a copper foil) with a thickness in the range of 3-30 ⁇ m, preferrably 10-15 ⁇ m.
• the coated sheet is heated in such a way that the coating powder is only partially cured.
• the degree of curing is less than 60 %, preferably less than 40%, and most preferably less than 30 %.
• the melting temperature is in the range of 80-250 0 C and preferably in the range of 100-170 0 C.
• the melting time is from 0.1 -20 seconds and preferably from 0.1-5 seconds.
• the coating powder is only partially cured, it is possible to laminate the coated sheet (such as a copper foil) and the substrate such as glass fabric.
• Lamination is preferably done by roll lamination or belt lamination.
• Belt lamination is preferred as it increases the intimate contact between the substrate and the sheet.
• lamination is done at a temperature in the range of 100-180 0 C and pref ⁇ erably in the range of 120-150 0 C.
• the lamination pressure ranges from 1-3O N/cm 2 and preferably 15-25 N/cm 2 .
• the process according to the present invention achieves a more homogeneous coating powder and thus more homogeneous layer thick ⁇ nesses and edge coating. Further, the process according to the present invention is advantageous in that it does not require any solvents so that costs for the raw materials may be reduced. Further, considerable amounts of energy may be saved. In addition, the costs for the disposal of the solvent (by burning) are not incurred.
• a further advantage is that the so-called “skin over effect" can be avoided which occurs upon evaporation of solvents and which makes it difficult to remove the solvent completely from the inner layers.
• the whole device for carrying out the process according to the present invention can be constructed in a compact manner and nevertheless be operated at high belt conveyer speed.
• the device Since the device is very short, it does not comprise much freely pending substrate material such as glass fabric.
• a further advantage of the process according to the present invention is the con ⁇ tact-free coating occurring therein. Further, it is possible, as described before, to incorporate various fillers into the coating powder.
• the stress exerted on the substrate material is low because most of the mechanical strain or stress on the metal sheet does not occur, which metal sheet forms part of the composite to be coated. In this way glass fabric can be used which is thinner than the one processed so far.
• the processing of the fibre-reinforced resin coated copper sheets comprising very thin substrate material obtained by the process according to the present invention in the production of printed circuit boards.
• the component layers will get thinner and lighter and the mi- crovia holes can be laser-drilled quicker resulting in an improved production effi ⁇ ciency because more holes can be drilled per time unit >/vith the same capacity of laser drills.
• Particularly structured surfaces can be obtained by the process according to the present invention.
• the corresponding parameter is the so-called gloss value which can be determined by a glossmeter.
• the surfaces obtained by the process accord ⁇ ing to the present invention have in general a gloss value ⁇ 60, preferably ⁇ 30 and most preferably ⁇ 20 (as measured with a glossmeter of Byk Gardner at 60°).
• a roll of glass fabric (Hexcel Fabrics, type 106, thickness 40 ⁇ m) was layed onto the treated side of a copper sheet having a thickness of 12 ⁇ m and the assembly was coated with coating powder (Example 1 ) by an EMB device continuously.
• the coating powder was melted in a NIR oven so that an optically uniform composite of coating powder/glass fabric/copper sheet was obtained. No inclusion of air could be detected under the microscope.
• the powder wetted the fabric and the copper foil well.
• This composite was pressed on a FR4 laminate (thickness 0.8 mm). A cross- section of this composite was examined by microscope. An analysis by means of SEM in combination with EDX showed a uniform distribution of the inorganic filler particles in the resin matrix, the glass fabric was uniformly embedded from all sides in the resin. The thickness of the dielectric layer along a sample having a width of 40 cm is listed in the table below. The sheet obtained in this way has a gloss value ⁇ 10 (as measured with a glossmeter from Byk Garnder at 60°).
• Step 1 Applying a thin layer of coating powder to a copper sheet
• a 12 ⁇ m copper sheet was coated continuously with a coating powder that was melted immediately after its application in a NIR oven.
• the EMB device was ad ⁇ justed in such a way that a 15 ⁇ m coating powder layer on the copper sheet was produced (belt speed 5 m/min, brush drum voltage 1200 V).
• the power of the NIR oven was selected such that the coating powder was not completely cured but had a relatively low degree of curing of 30%.
• Step 2 Lamination of glass fabric on the coated copper sheet obtained in step 1
• the coated sheet and glass fabric (Unitika, Type 106) were processed continuously in a roll laminator (Soni R 160). Typical process conditions were a temperature of 14O 0 C at a belt speed of 1-2 m/min. A lamination pressure of 2.5 bar was selected. Under these conditions the coating powder melts again and can intimately com ⁇ bine the copper sheet and the glass fabric without the occurrence of blisters.
• Step 3 Applying a second layer of coating powder to the laminate obtained in step 2
• a third step the composite of copper sheet, coating powder and glass fabric is coated with a further layer of coating powder. Its thickness can be varied by choosing the EMB device parameters accordingly depending on the intended use of the final composite. To achieve this, the roll obtained in step 2 is inserted into an EMB device and continuously coated with a coating powder which is melted again in a NIR oven without being completely cured.
• the composite obtained in this way layed up on a core and pressure is applied to to form a laminate.
• the total thickness of the dielectric layer generated in this manner was 45 ⁇ m.
• Steps 1 and 3 were carried out as described in Example 3. However, in step 2, the roll laminator was replaced with a belt laminator (KFK, from Meyer, Germany). A composite free of blisters could be obtained at a belt speed of 5 m/min, a lamina ⁇ tion temperature of 160 0 C and a lamination pressure of 20 N/cm 2 .
• KFK belt laminator

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