NL8002514A - LAMINATED SHEETS WITH POLYSULPHONE SURFACE AND MANUFACTURE THEREOF. - Google Patents

Description

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Laminated plates with polysulfone surface and the manufacture thereof.

The invention relates to a blank plate or a substrate suitable for use in the manufacture of printed circuit boards. More particularly, the invention relates to a raw sheet consisting of an insulating substrate on which is superimposed a thin, high temperature resistant thermoplastic polymer film (or sheet or layer) adhered to at least one surface thereof as well as a method of manufacture thereof.

Printed circuit boards generally comprise an electrically insulating substrate connected to one or more electrically conductive circuit patterns. The insulating substrate usually comprises a synthetic resin composition reinforced with non-conductive fibrous materials, e.g., fibrous glass sheets, papers, fleeces or mats of glass fibers in woven or non-woven form or cellulose paper sheets; the electrically conductive chain pattern can be a metal, such as copper, nickel, cobalt, gold, silver, and the like.

The use of insulating substrates for the production of printed chains by means of electroless deposition techniques is known and it is also known to provide such substrates with a thermosetting rubber resin film before electroless deposition, in order to improve the adhesion. . The insulating resinous film layer adhered to the base uniformly distributes particles of a rubber which is oxidizable and / or degradable by suitable oxidizing chemicals. This technique has been successfully used in the printed circuit industry for a number of years. The surface resistance of printed circuits, using these techniques, is as low as 5000 megohms when conditioned according to the ASTM D-618-61 procedure C and measured on an insulation resistance pattern as shown in the IPC Test Method No. 5 * 8.1 . (April 1973) (Institute for Interconnecting and Packaging Electronics 800 2 5 14 - 2 - Μ

Circuitry). As the chains have become more complex and the conductors are placed close together, a relatively low surface resistance has become problematic.

The known techniques for promoting adhesion can be better understood from the types of substrates used. Organic coatings and materials, the surfaces of which may be provided with electroless metal deposits with a commercially acceptable adhesion, ie, peel strengths of at least 1.2 Newton / mm 10 width, have hitherto depended on the method of manufacture thereof, as well as the chemical treatment required to ensure a sufficiently adherent electroless metal coating thereon classified into different categories.

Materials of a first type, used to form an adhesive coating on a suitable substrate, typically comprise a dispersed phase of synthetic rubber, such as butadiene or acrylonitrile butadiene copolymers in a matrix of materials, such as epoxy / phenolic blends. The dispersed phase material of such substrates is readily decomposed by oxidizing agents such as chromic acid or permanganate etching solutions, while the matrix phase is less reactive with respect to such agents. After the oxidation treatment, the substrate surface is microporous and hydrophilic and suitable for further processing according to known electroless metal coating procedures, optionally in combination with electrocoating steps.

Another general type of resinous substrates, such as certain epoxy and polysulfone materials, sometimes referred to as single phase materials, require a step prior to the etching step to form a microporous surface; polar and deformed sites or domains, which are selectively attacked in the oxidation steps, are usually created by contacting the surface with an organic solvent, thereby causing preferential attack of these sites upon contact with the etchant. This 800 2 5 14 - 3 -.

The method has become known as the "swelling and etching" technique.

In the swelling and etching technique, the surface of a glass-reinforced, epoxy-impregnated laminate is first treated with a solvent and then with a strong oxidizing agent, e.g. chromic acid, to etch away part of the surface and produce a microporous, hydrophilic surface suitable for adherent electroless metal deposition. This technique in itself did not provide acceptable surface resistance because the oxidation process could penetrate deep enough of the glass cloth laminate core. To avoid this problem, special qualities of laminates have been proposed with thick, epoxy resin "butter" layers on the glass fibers. Using such quality laminates, it has proven possible to make printed circuits with an insulation resistance of 100,000 M.Ohm. Curing variation of the epoxy "butter" layer depending on the producer and also from batch to batch of the same product requires the method to be redefined for each batch. For these reasons and because of the difficulty of obtaining a reliable uniform "butter layer", commercial production has not got off the ground. A further disadvantage of this method is the frequent failure of bonding in large areas of exposed metal during brazing.

It is also known that certain plastic materials for decorative applications can be coated with metals by first conditioning them in strongly oxidizing acids. Plastic materials which have been successfully coated include acrylonitrile butadiene styrene copolymers, polyphenylene oxides, polysulfones, polycarbonates and nylon, Acrylonitrile butadiene styrene has been proposed for use as a film in the manufacture of printed circuit boards but has proved unsuitable: its bond strength was only mm and the respective printed circuit boards were not resistant to the soldering temperature.

800 2 5 14 - 4 - *

Pressed polysulfones have been used as printed circuit material in very limited quantities, and then only in high-frequency applications where the low dielectric constant and dissipation factor of the polysulfone were beneficial. Chain base materials consisting of polysulfone have not yet come into vogue due to the extreme processing difficulties and the high price of the said material. In the processing of pressed polysulfone material for use as printed chain substrates, it is necessary to anneal or release the voltage for at least 2-4 hours, with 6-8 hours being preferred. These laborious steps are required two or more times during a typical chain plate production cycle. Too much annealing of the polysulfone materials should also be prevented to avoid embrittlement and other harmful effects.

It is a primary object of the invention to provide an improved method of forming substrates for adherent metallization and improved substrates for electroless deposition of metals thereon. It is an object of the invention to provide a new and improved insulating plate with a surface that can be activated to receive or receive electroless formed metal deposits.

It is another object of the invention to provide sturdy and durable metallized objects of such an insulating base plate.

It is a further object of the invention to make printed circuit boards from such blank plates, including 1-layer, 2-layer and multilayer plates, which are provided with conductive passages.

It is another object of the invention to provide printed circuits using such output plates, which circuits have high surface resistance, excellent bond strength between the surface of the circuit and the electroless coating adhered thereto. 800 25 14 - 5 - 5% metal, and have excellent soldering temperature stability, as well as reproducible methods of fabrication and on-site repairability.

It is another object of the invention to provide a multilayer circuit board with a set impedance for high speed logic and other set impedance applications.

To achieve the aforementioned objects, the invention provides an improved starting plate and method for its manufacture, an improved metal-coated insulating substrate and a method of manufacturing the same, an improved method of making printed circuits under use of the improved output plates, as well as the improved circuit plates formed therefrom. As will become apparent from the following description, the base material or blank of the invention suitable for the manufacture of printed circuit boards comprises a substrate, on at least one surface thereof being a preformed film or foil of a thermoplastic organic high temperature polymer attached, which poly more has an aromatic backbone that does not liquefy or decompose at the temperature of the mass soldering and during such a soldering process.

According to the invention, printed circuit board fabrication plates are produced by a method comprising the following steps; at least one of the surfaces of a substrate, selected from raw metal sheets and insulating materials, is provided with a superimposed layer of a preformed film or foil of a thermoplastic polymer with an aromatic backbone that does not liquefy or decompose when exposed to the mass soldering procedures $ after which the combination thus produced is consolidated by heating under pressure.

It is a further object of the invention to provide 800 2 5 14 - 6 - a combination comprising a metallic or insulating substrate, wherein on at least one of the surfaces of the substrate by heat-pressing a pre-formed foil of said thermoplastic polymer is attached.

It has been found that such combinations do not become brittle during processing and application and provide printed circuit boards with excellent surface resistance value,

In another embodiment of the invention, printed circuit boards are produced by treating a surface or surfaces of the polymer film after consolidation, which treatment comprises the steps of pretreating the polymer surface or surfaces with a polar solvent, whereby the outer layer of the polymer swells and then contacts the thus pretreated surface or surfaces with a strong oxidant. solution; as well as the electroless deposition of metal, whether or not followed by electrolytic deposition on at least parts of the surface or surfaces, whereby printed circuit patterns are formed according to methods known per se.

A further embodiment of the invention is directed to printed circuit boards having more than one circuit pattern on one side of the substrate and to the manufacture of such boards by a method comprising the steps, which are applied on at least one surface of a suitable base material is applied to a first printed circuit, after which at least the surface area with said applied circuit pattern is provided with a layer consisting of a preformed foil of a thermoplastic polymer, after which the surface of said foil is treated with a solvent and subsequently with an oxidizing agent; and the thus prepared surface of the film is provided with a second printed circuit pattern; after which this sequence of applying the pre-formed polymer foil and forming a conductor pattern is repeated as many times as desired.

In order to connect selected conductors of different levels, openings which cut the conductors and have metallic bands can be used. In another embodiment, the surfaces of one-level conductors to be connected to conductors of a contiguously arranged level are kept free from the polymer film or are freed after the film is applied, with the respective second-level conductors at such formed so that the formed metal deposit covers the now exposed conductor regions of the respective first level conductors.

Other embodiments of the invention will become apparent from the following description.

By "B-stage" as used in the description is meant the state of a composition in which some, but not all, active molecules are cross-linked and the composition is still soaked by heating.

By "C-stage" as used in the description is meant that state, in which a composition has almost completely reached the final stage of the polymerization, where the cross-linking becomes general and the composition, assuming that it is a thermosetting composition, is virtually insoluble 25 and is infusible.

The laminated base plates of the invention, as well as the methods of their manufacture, represent an improvement over the substrates used hitherto. The methods of the invention use thermoplastic, organic, high temperature polymers as the surface layer or layers of a starting plate. The surface layer preferably has a thickness not less than 10 micrometers, e.g. above 25 microns and most preferably above 50 microns; generally, the thickness of the polymer surface is below 500 µm, preferably about 150 µm, most preferably below 75 µm. One or more folds or layers of the thermoplastic polymer is superimposed and laminated onto one or more of the folds or layers of a "B-stage" resin-impregnated reinforcement, such as a glass film, cloth or paper, using heating and pressure to form a rigid printed wiring board substrate,

The invention provides a simple and economical method of manufacturing exit plates with substantially 10 planar surfaces, which surfaces can be attacked to receive a layer or pattern of conductive metal using an electroless deposition technique. In one aspect, the invention relates to an insulating substrate suitable for use in printed circuits, as well as a method of manufacturing the same, which method comprises: - providing thermoplastic films or sheets of substantially uniform thickness between about 10 and 500 micrometers, the thermoplastic material having an aromatic chain that does not liquify or decompose at a temperature of eg 245 ° C after 5 seconds of contact with this temperature; - providing a fibrous sheet or web impregnated with a thermosetting resin or layers or folds of the impregnated fibrous sheets or webs; - superimposing at least one of said films or sheets on at least one of said folds or layers of the thermosetting resin impregnated fibrous sheets or webs; and - preferably consolidating the thus obtained combination between planar pressing plates and curing the thermosetting resin by heating under pressure.

In another aspect, the invention relates to a blank, suitable for use in printed circuits, comprising: 35 - an insulating substrate, on which 800 2 5 14 * - * - 9 - g thereof or opposite each other lying surfaces thereof a thermoplastic organic high temperature polymer is bonded with a thickness between about 10 and 500 micrometers, which polymer has an aromatic backbone that does not liquify or decompose at a temperature of 245 ° C after 5 seconds of contact at the temperature.

In yet another embodiment, the invention relates to a laminate and a method of manufacturing the same as will be described hereinafter, which laminate comprises the blank as described above and further superimposes or adheres an electroconductive metal layer to the polymer surface layer or - layers. The polymer film surface layer serves as an adhesive between said metal layer and the reinforced thermoset substrate. Accordingly, for laminating a metal to a reinforced polyester substrate, e.g. a metal film and a thin thermoplastic film are pressed together with a reinforced polyester substrate whereby the three layers are bonded together or the thermoplastic film surface of the starting plate can be treated with an oxidizing medium or a plasma to form a hydrophilic surface, which is receptive to subsequent metallization and is coated with an electroless formed metal deposit.

In another aspect, the invention relates to a multilayer printed circuit board, as well as a method of manufacturing the same comprising the following steps - an insulating substrate is provided with a circuit pattern adhered to at least one surface 50 thereof; - a layer of e.g. a polysulfone foil applied over the circuit patterns or the pattern; the polysulfone surface or surfaces are treated with a solvent and an oxidizing agent to make the surface or surfaces microporous and hydrophilic; 80 0 2 5 14 - 10 - $ and - a metal is electrolessly deposited on the treated surface or surfaces.

Any thermosetting resin known for the manufacture of insulating substrates for printed circuits can be used in the process and the master plate of the invention provided that they, together with the other materials used, impart desirable properties to the final substrates. Examples include allyl phthalate, furan, allyl resins, glyceryl phthalates, silicones, polyacrylic acid esters, phenol formaldehyde and phenol surfural copolymer, alone or formulated with butadiene acrylonitrile copolymer or acrylonitrile butadiene epoxydehyde methyldehyde, melamine. Phenol formaldehydes can be used when the usage requirements are not stringent. Epoxy resins are preferred when stringent properties are required. For impregnating the fibrous webs or sheets used in the process of the invention, the thermosetting resins in any suitable form and manner may be used, but preferably a varnish is used in which the resin is dissolved or dispersed in a suitable medium. The weight of the solid resin in the varnish is not particularly critical, but it is selected to achieve epoxy glass cloth combinations or compositions comprising about 35-70%, preferably about 35-55% by weight solid resin . The insulating base of the invention need not be organic. Thus, it can be made of inorganic insulating materials, e.g. inorganic clays and minerals, such as ceramics, refractories, ferrite, carborundum, glass, glass-bound mica, steatite, and the like. Furthermore, sheet or layer material can be used as the substrate to be coated with the preferred thermoplastic film with or without an intermediate layer of a thermosetting resin or of a material impregnated with such a resin, 800 2 5 14 i - 11 -

Suitable thermoplastic film materials are high temperature thermoplastic polymers with an aromatic backbone that do not liquify or decompose the temperatures of the mass soldering, e.g. 245 ° C, after 5 seconds it contacts such a temperature. Examples include polycarbonates, polysulfones with the repeating unit of formula 1 of the formula sheet, polyether sulfones with the repeating unit of formula 2 of the formula sheet and polysulfones. As can be seen from the structural formulas of Formula Sheet 10, each aromatic unit (Formula 5) is the polysulfone via a -SO2 substituent coupled to its neighboring unit called a sulfone linkage or bond. Similarly, each aromatic unit in the polyether sulfon is combined or linked to its neighbor by a -SO-15 substituent at one end and an -O substituent at the other end, called an ether bond or coupling.

It can also be further observed that each substituent having 4 carbon atoms is separated from the aromatic unit, e.g. a para substitution.

Certain grades of these thermoplastics in the form of pressed sheets, rods and / or films can be treated to make the surface of these materials sensitive to adhering metal cladding. These materials are widely used as decorative, automotive and electronic components, medical adjuvants, as well as in food and milk processing machines. For illustrative purposes, the following discussion will focus on certain grades of polysulfone. Different grades of polysulfone are known to be characterized by their toughness, low creep and long-term thermal and hydrolytic stability; they can be used continuously for years in contact with boiling water or steam and in air above 150 ° C without significantly altering their properties. Polysulfones meet the Underwriters' Laboratries thermal 55 index ratings of 150 ° C; they retain these properties in 800 2 5 14 - 12 - t the temperature range from -100 to above 150 ° C. They have a heat distortion temperature of about 174 ° C at 1.8 MPa and about 181 ° C at 41 MPa. Prolonged thermal aging at 150-200 ° C has little influence on the physical or electrical properties of polysulfones.

Polysulfones can be prepared by the nucleophilic substitution reaction between the sodium salt of 2,2-bis- (4-hydroxyphenyl) propane and 4'-4'-dichloro diphenyl sulfone. The sodium phenoxide and groups are reacted with methyl chloride before finishing the polymerization. This sets the molecular weight of the polymer and contributes to its thermal stability.

The chemical structure of the polysulfone is characterized by the diarylsulfone grouping. This is a highly resonant structure in which the sulfone group tends to extract electrons from the phenyl rings. The resonance is enhanced because the oxygen atoms are para to the sulfone groups. Electrons bonded by resonance impart excellent oxidation resistance to the poly-20 sulfones. The sulfur atom is also in its highest oxidation state: this increases the strength of the bonds involved and fixes this group spatially to a planar configuration. This gives rigidity to the polymer chain which is maintained at high temperatures.

The ether bond provides some flexibility to the polymer chain, thereby imparting inherent toughness to the material. The sulfone ether bonds connecting the benzene rings are hydrolytically stable. As previously mentioned, therefore, the polysulfones are resistant to hydrolysis and to aqueous acidic and basic environments.

Suitable grades of polysulfone of the invention include, e.g. an unmixed grade, such as the P-1700 series, which is used for injection molding or extrusion, a high molecular series for extrusion applications, such as the 35 P-3500 series; and a mineral-mixed polysulfone, which is suitable for coating purposes, such as the P-6050 series (the P-1700, P-3500 and P-6050 series are manufactured by Union Carbide Corporation in marketed).

Polycarbonates are linear, low crystalline, high molecular (molecular weight about 18,000) polymers, in which the coupling elements are carbonate groups. Polycarbonates have a combination of very suitable properties comprising: (1) a very high notch impact strength (2.2 m / kg) combined with good ductility; (2) excellent dimensional stability, combined with low water absorption (0.35 $ immersed in water at room temperature; immersion in boiling water does not change dimensions more than 0.01 cm / om); (3) a high heat distortion temperature of about 135 ° C; (4) excellent heat resistance with excellent resistance to thermal oxidative decomposition; and (5) good electrical resistance.

Polyphenylene oxide can be prepared via oxidative coupling of phenols. Oxidative coupling refers to the reaction of oxygen with active hydrogen atoms from various monomers to form water and a dimerized molecule. If the monomer has two active hydrogen atoms, the oxidative coupling continues and leads to polymerization. The polymer structure of polyphenylene oxide is characterized by a high degree of symmetry, no strongly polar groups, a rigid phenylene oxide main chain, a high glass transition temperature (21 ° C) and no other observable over-30 passes in the range from -273 to -210 ° C.

Polyphenylene oxide has a combination of beneficial properties including: (1) a temperature range between about -180 and + 180 ° C; (2) excellent hydrolytic stability; 35 (3) dimensional stability with very low water absorption, 800 25 14 - een - $ low creep and high modulus; and (4) excellent dielectric properties over a wide range of temperatures (-180 - + 180 ° C).

The laminated thermoplastic polymer films of the invention provide an adhesive of high effectiveness suitable for printed circuit applications with reliable properties and an effectiveness superior to that available with the known resin-rich and rubber-thermo-adhesive adhesives. The thermoplastic film surfaces 10 'of the base plate of the invention have a substantially uniform thickness and can be chemically treated by known techniques to achieve excellent adhesion of electroless metal subsequent deposits during the manufacture of printed circuit boards.

It is well known that these high temperature polymers, especially polysulfones, when used on their own, require a prolonged, secondary annealing treatment to prevent stress cracking. Normal recommendations for this calcination are 2-4 hours and up to 20 hours at 170 ° C prior to processing. An extra long annealing cycle is required after machining the material before etching the surface for the subsequent metal deposits. As will be described below, the annealing and formation of the blank sheet and / or the laminate of the invention take place simultaneously and thus in one step. It has been found that when the thermoplastic polymer films of the invention, such as polysulfon, were laminated to an insulating substrate according to the invention, the thermoplastic polymer films could be stress relieved during the lamination cycle.

This eliminates the need for the aforementioned cumbersome and time consuming secondary annealing stages.

According to a method of the invention, the starting plate is formed by arranging impregnated folds or sheets of the insulating substrate and preformed thermoplastic fo-800 2 5 14 - 15 - 4 groin or sheets in the form of a laminate and this under heating and laminate pressure, e.g. at 160 ° C and 1.4 MPa for up to 60 minutes. The lamination step can be carried out in a conventional press using known conditions for producing laminates impregnated with thermosetting resins with substantially planar surfaces. Suitable curing cycles are e.g. 10-60 minutes at 120-180 ° C and 1.5-10 MPa.

Other methods of manufacturing the blank 10 of the invention are possible. For example, one can dipping a laminated insulating substrate in a polysulfone, which is adherent to the preformed thermoplastic film.

It is known that a 2-5% solution of polysulfone in methylene chloride can be used to achieve a strong bond at room temperature. A polysulfone foil can e.g. are coated on e.g. an insulating substrate by immersing the foil and the substrate in the polysulfone-methylene chloride solution, allowing them to air dry for 15 seconds and then combining them in a press and 20 minutes under a pressure of about 35 kg / cm. After removal from the press plates used in the above-described lamination step and the like, the thus formed starting plate can be used for the manufacture of printed circuit boards.

In another preferred embodiment, a thin metal foil can be superimposed on one or more surfaces of the blank and adhered thereto to form a laminate.

Output plates of the type described above can be used to produce 1-layer, 2-layer and multi-layer printed circuit boards with or without lined openings in the manner as will be described in detail below.

In a certain method for the production of printed circuit boards, the so-called "semi-additive" 800 2 5 14-16 * technique is used. The insulating blank of the invention is cut to size and holes are made therein by drilling, striking, and the like. The surface of the starting plate is contacted with a pre-etching solvent or treated with an abrasive. It is believed that the surface of the starting plate can be mechanically roughened prior to the oxidation treatment to replace the solvent pretreatment. When the term "solvent pre-treatment" is used, it also means the use of a mechanical roughening step instead of the treatment with a solvent. A typical mechanical roughening treatment is the irradiation of the surface of the starting plate with crushed stone, namely with a suspension of a finely divided abrasive material, such as sand, aluminum oxide, quartz, carborundum and the like with a size finer than 100 USA sieve series (<0.15 mm). The solvent-treated plate is then mechanically and chemically treated with an oxidizing solution to activate the surface of the plate.

A conventional electroless plating method is used to deposit a thin conductive layer of copper on the activated surface of the plate and, if and when desired, on the entire walls. A temporary protective coating or backup layer is used for a screen print of a chain pattern with 0.36 mm lines; the temporary spare layer is cured by heating. The chain pattern is constructed by electrically coating a metal on the exposed areas of the substrate. The temporary spare layer is removed and the thin layer of electrolessly deposited metal covered by the mask is etched away with acid. Her choice may be the temporary protective coating a photoresist layer.

In another method for forming printed chain plates, known as the fully additive technique, a suitable insulating base plate according to the invention is manufactured with a polysulfone, polyethylsulfone or polycarbonate surface layer and laminated to a suitable substrate, such as an epoxy resin base, reinforced with fiber glass. Holes are formed in pre-selected places in the plate. The 5 surfaces of the plate and the walls of the holes are pretreated as described above. A photo-imaging technique is used. The plates and holes are completely coated with an aqueous ultraviolet-reducible copper compound and dried. An ultraviolet photo image is formed by projection or contact printing on the sensitized substrate, electrolessly depositing a metal, such as copper, on the exposed pattern and in the holes until a circuit is built up to the desired thickness.

Generally, it is desirable to treat the surface with an agent, e.g., dimethylformamide or dimethyl sulfoxide, before or during the ethers method in an oxidizing agent. Suitable solvents and mixtures thereof for swelling polysulfone include, in particular, dimethylformamide, acetophenone, chloroform, cyclohexanone, chlorobenzene, dioxane, methylene chloride and tetrahydrofuran.

Depending on the particular surface area of the plates, other ion exchange materials can be used to effect the aforementioned transient polarization reaction, e.g. acidified sodium fluoride, hydrogen chloride and hydrofluoric acids, chromic acids, borates, fluoroborates and caustic, as well as mixtures thereof, can be used effectively to polarize the various synthetic thermoplastic insulating materials as described herein. Acid oxidizing agents typically used for etching acrylonitrile butadiene styrene substrates have been found to be satisfactory for polysulfone substrates. A typical composition includes by weight: 6 <$ HoS0, 2 4 1 0 # CrO ^ 35 30 # H20 800 25 14 - 18 - t

During etching, the chromium in contact with the pretreated polysulfone surface is reduced from Cr "1 ^ to Cr + ^. When most of the chromium is reduced, the acid is no longer as effective in improving adhesion of For this reason, it is desirable to have as much chromium as possible in the acidic conditioner, however, with dimethylformamide as the preconditioning bath, chromic acid contents above about $ 3 lead to macro cracking and poor adhesion. or the areas are therefore by weight: 55 9 $ H2S04 (9696) 10,4 $ Η? Ρ04 (85 to 87 $) 50,7 $ h2o 15 3,0 $ Cr05

In an alternative "full additive" technique after exposing the surface to make this polar and micropo-giant, the plate and the walls of the holes are activated with known grafting and sensitizing agents, such as e.g.

20 stannous chloride-palladium chloride, activators. A permanent protective coating or reserve is selected to produce a permanent background backup layer that leaves the desired circuit pattern unprotected. The reserve is cured and the copper is electroplated on the unprotected cartridge and in the holes.

The plate of the invention may optionally be catalytic, e.g. catalytic materials may be distributed therein. In the aforementioned techniques for the manufacture of printed circuit boards, this eliminates the need for a separate grafting or sensitizing step.

For printed circuits, among the materials that are preferably used as the insulating substrates for the plates, there may be mentioned insulating thermosetting resins, thermoplastic resins and mixtures thereof, including fibers, e.g. Fiber glass impregnated embodiments of the foregoing.

There may be an adhesive layer on the plate. The plates can include metal substrates, such as aluminum or steel, which are coated with insulating layers of preformed films of thermoplastic polymers. When the conductive pattern is to be coated through the holes, it is preferable to first hole the metal sheet and coat the sheet by powder melting techniques, such as with a fluidized bed with an appropriate insulating layer.

The invention includes, as embodiments, metalized plates in which the electroless metal, e.g. copper, nickel, gold, etc. is further built up by connecting an electrode to the electroless metal surface and depositing thereon electrolytically more of the same or different metal, e.g. copper, nickel, silver, gold, rhodium, tin, alloys thereof and the like. Slip coating procedures are known.

The invention will now be further elucidated with reference to the annexed drawings, which illustrate certain embodiments of the invention in connection with the description, with which the principles of the invention are elucidated.

Figures 1-3 illustrate procedures that can be used to form printed circuit boards from insulating plates obtained according to the rules of the invention? FIG. 4 illustrates a method and apparatus for making a blank using a roller according to the instructions of the invention? Fig. 5 illustrates a method and apparatus for making a plate by roller applying polysulfone to a rigid substrate.

Fig. 1A shows an insulating blank 10 according to the invention. The plate 10 includes an inner core 35 of thermoset resin and outer surface layers of pre-800 2 5 14-20 t-formed polysulfone foil 14. The core is catalytic with respect to the electroless metal deposition. The polysulfone foil 14 is also catalytic with respect to the electroless deposition of metal.

In Fig. 1B, holes 16 and 18 have been heard through the plate 10. Plate 10 is then immersed in a pretreatment solvent followed by chemical treatment with an acid etching solution, such as 20 g / l Cr05 10 350 mg / l H2S04

50 g / l NaF

at a temperature between 45 and 65 ° C, exposing the catalyst and activating the surface of the plate 10 as shown in Fig. 1C. A photo reserve 24 is provided (shown in Figure 1D) on a surface of the plate to mask areas not subsequently coated with copper. Copper is then electrolessly deposited on the walls of the holes 16 and 18 and on the exposed surface areas of the plate 10 by methods known per se to form a copper conductive pattern 22 of about 35 microns thickness, as shown in FIG. 1E. The photo reserve 24 is then stripped as shown in Fig. 1F. A registered solder mask 30 can then be placed over the circuit pattern and both holes 16 and 18 remain unprotected (Fig. 1G).

In Figure 2, an additive method for manufacturing a multilayer printed circuit board is shown. In Fig. 2A, a printed circuit pattern 102 is adhered to an insulating plate 100. A preformed polysulfone foil 104 is superimposed and bonded over the printed circuit pattern 102 (Fig. 2B). Then a hole 106 is drilled through the polysulfone foil 104, the printed circuit pattern 102 and the insulating plate 100 (Fig. 2C). The surface adhesion of the polysulfone foil 104 is enhanced for coating using the techniques described previously.

800 2 5 14 - 21 - *

The polysulfone foil 104 surface is activated by dipping in a palladium tin solution. In Fig. 2D, a photoresist image 110 is applied to the outer surface of the polysulfone foil 104. The exposed foil surface 104 and hole 106 are electrocoated with copper 112 to form a thickness of about 35 micrometers (Fig. 2E).

In Fig. 2F, the photoresist image 110 is stripped to provide a multilayer printed circuit board.

In Fig. 3, a semi-additive method for manufacturing a multilayer printed circuit or circuit board is shown.

In Fig. 3A, output plate 200 on opposite surfaces is coated with copper 201. A first or internal circuit pattern 202 is formed with a conventional etching technology and coated with a layer of a preformed polysulfone foil 204 (Fig. 3B). A hole 216 is drilled through the plate 200. The adhesion of plate 200 is improved and the plate is catalyzed to receive the electrolessly formed metal layers, with an electrolessly deposited copper film 211 on the polysulfone surface 204 and in the hole 216 to a thickness of e.g. 2 micrometers (fig. 3C) is applied. A photoresist image 210 is applied and additional copper 212 is electrically coated to provide a copper layer approximately 35 micrometers thick (Fig. 3®). In Fig. 3E, the photoresist image 210 is removed and the copper film 211 under the photoresist 210 etched away with a suitable etchant.

Fig. 4 shows a method for making an insulating plate according to the invention. Feed rollers 100, 102 and 104 are shown. Wound on roll 100 is a bendable support 106 with a thickness of about 1.6 mm, which support consists of woven glass, non-woven glass, dacron, rayon, cellulose paper, and the like impregnated with resins, preferably thermoset resins, such as epoxy resins But also high temperature thermoplastics such as poly-800 2 5 14 i-22 imides and polycarbonates can be used. Wound on the feed roller 102 is a thermoplastic film 108 of 1-5 mm thickness. A thermoplastic film with a thickness of about 1-5 mm is also wound on feed roller 104.

The thermoplastic film can e.g. a polysulfone, polyether sulfone or polycarbonate film.

Also shown are combined take-up rollers 110, which apply heat and pressure to the continuous laminate therebetween. A temperature of about 160-200 ° G and a pressure of about 50-400 N / mm is conveniently applied between the rollers 110. The flexible laminated base material 10 according to the invention exits from the rollers.

In Fig. 5, on a rigid substrate 12, with a roll, e.g. 8 mm thick epoxy glass cloth-reinforced laminate applied.

Feed rollers 100, 102, 104 are shown. Wrapped on the rolls 100, 102 and 104 are respective thermoplastic films 108 with a thickness of 1-5 mm. Also shown are combined take-up rollers 110 which heat and pressurize the laminate passing therebetween. A temperature of about 160-200 ° C and a pressure of 30-400 N / mm is suitably applied between the rollers 110. The insulating substrate 12 passes between the rollers 110 and the thermoplastic films 108 are laminated to the opposite surfaces of 12 under heating and pressure to form plate 10 which is separated from the web after emerging from the rollers 110. Optionally, the iso-. Learning base 12 is coated with a polysulfone adhesive consisting of a solvent dissolved polysulfone before applying the thermoplastic film.

The following examples illustrate preferred embodiments of the insulating plates, printed circuit boards and methods of the invention.

Example I

Eight layers of glass cloth impregnated with 55-55 wt., $ 35 epoxy resin were placed in a laminating press with a sheet of 800 2 5 14 i-23 - of preformed polysulfone film, 50 microns thick, both on top ala "at the bottom. The poly sulphon oil was made from IdLL P-170Q polysulphone resin A lamination temperature of 175 ° C, a pressure of 4.1 MPa and a residence time in a hot 15 minute press were used After 15 minutes, the press was cooled to room temperature and removed the plate.

The board was processed into a printed circuit board with the following stages (1) through holes were drilled in the board? 10 (2) the plate was brushed to remove drill impact (note that after drilling no annealing or oven baking was necessary)? (3) the plate was immersed in a dimethylformamide water solution (s.g. of 0.955-0 * 965) for 3-6 minutes? (4) the plate was rinsed in hot water for 45 seconds? (5) the adhesion of the surface of the plate was improved at a temperature of 55 ° C for a period of 7 minutes with the following solution? 20 CrO ^ 20 g / l H5PO4 100 ml / l H2S04 600 ml / l FC-98 * 0.5 g / l * FC-98 is an anionic perfluoroalkyl sulfonate.

25 (6) the plate was rinsed in water? (7) Cr (Y1) was neutralized with a solution containing 10fo H 2 O and 15 # H 2 SO 4? (8) - (11) the plate was rinsed in water, successively immersed in 2.5 M CH1, a seed solution and an accelerator (5 $ HPF4)? (12) copper was deposited electroless on the plate to a thickness of 2.5 micrometers? (13) - (14) the copper-coated plate was rinsed in water and dried at 125 ° C for 10 minutes.

A printed circuit board was manufactured using 800 2 5 14 - 24 - using the said copper clad plate and techniques known per se, e.g. a background spare image was printed, a copper circuit pattern was formed by electrolytic plating, the spare layer was removed and the exposed copper etched away.

A peel strength of 1.7 H / mm was measured for the printed circuit board. A soldering flux test was also used. A 2.5 cm square copper pattern (printed circuit board) made according to this example was floated for 10 seconds at 260 ° C melted solder. The sample was removed from the plate for examination of potential vesicles and / or delamination of the copper pattern. No blistering or delamination was detected.

Example II

Example I was repeated with the exception of a lamination pressure of 2.8 M.Pa and a residence time in the laminating press of 1 hour. A final peel strength of 2.4 µf / mm was measured and a 2.5 cm square copper pattern sample was floated in 260 g molten solder for more than 10 seconds, without blistering or delamination occurring.

Example III

Example I was repeated with the exception that a lamination pressure of 1.4 M.Pa and a residence time in the laminating press of 5 minutes were used. After lamination, the plate was stabilized at 160 ° C for 1 hour in a circulating hot air oven to avoid shrinkage and warping during processing. An end peel strength of 1.9 N / fim was measured.

Example IV

An epoxy glass laminate, G-10ER, was coated with 35 ml crometer thick copper foil on the top and bottom. A copper circuit was produced by conventional etching techniques. A polysulfone adhesive was prepared by dissolving pellets of Idle-P-1700 Ut polysulfone resin in methylene chloride. The etched panel was dipped in the polysulfone solution and air dried for 800 2 14 - 25 s. A 75 micron thick preformed polysulfone foil was laminated to the adhesive coated side of the panel in a press at 175 ° C for 10 minutes at 1.4 M.Pa.

5 through holes were drilled in the panel and the waste was removed by brushing. The panel was converted into a multilayer printed circuit board according to the procedure of Example I.

Example V

A single layer of a glass cloth impregnated with epoxy resin was placed between two sheets of 25 micron polysulfone film and laminated in a press under 2.8 M.Pa at 175 ° C for 10 minutes. This produced a flexible output plate useful for the manufacture of printed circuit boards.

t 80025 14

Claims (20)

Basic material or plate, suitable for the manufacture of printed circuit boards, comprising a substrate, on at least one surface of which a preformed foil or film of a thermoplastic organic high-temperature polymer is adhered, characterized in that the polymer is an aromatic main chain which does not liquify or decompose at the temperature of the mass soldering and during such a soldering method. 2. Plate according to claim 1, characterized in that the polymer does not flow or decompose at a temperature of 245 ° C after 3 x 5 seconds treatment time. Plate according to claim 1, characterized in that the preformed foil or film has a thickness of 10-500 micrometers. Plate according to claims 1-3, characterized in that the polymer of the preformed film or film is selected from polysulfone, polycarbonate, polyether sulfone. Plate according to claim 1, characterized in that the substrate is an insulating substrate. Plate according to claim 1, characterized in that the substrate is a metal. Plate according to claims 1-5, characterized in that the substrate is a laminate consisting of fiber-impregnated thermosetting resins. Plate according to claims 1-5 and 7, characterized in that it further comprises a layer of superimposed metal adhered to at least a part of the surface of the polymer film or foil. 9. Plate according to claim 8, characterized in that the metal layer is formed by electroless deposition in combination with electrolytic coating. 10. Method of manufacturing printed circuit boards, characterized in that on at least one of the surfaces of a substrate selected from metal plates and iso-800 2 5 14-27-learning material, a superimposed layer of a preformed film or foil of a thermoplastic polymer with an aromatic backbone, which does not flow or decompose on mass soldering, is applied and the combination formed is consolidated by heating under pressure. Method according to claim 10, characterized in that the preformed superimposed polymer foil has a thickness of 10-500 micrometers, preferably less than 125 micrometers. A method according to claims 10-11, characterized in that the substrate is composed of fibrous sheets or membranes impregnated with thermosetting resins. 15. A method according to claim 12, characterized in that the curing of the thermosetting resin is carried out simultaneously with the consolidation of the combination comprising the preformed film of the thermoplastic polymers. Method according to claims 10 or 13, characterized in that the consolidation step takes place at a temperature of 120-180 ° C and a pressure of 1.5-10 M.Pa, Method according to claims 10-14, characterized in that it further comprises treating the consolidated combination, which treatment consists of pretreating a polymer surface with a polymer solvent, which is suitable for swelling the outer layer of the polymer foil, a surface thus pretreated is contacted with a strong oxidizing solution; after which at least parts of the thus prepared surface are catalyzed to make it susceptible to electrolessly formed metal deposits; after which electroless metal is deposited on the said areas. Process according to claim 15, characterized in that the polar solvent is dimethylformamide solution and the oxidizing agent is chromic acid. Method according to claim 10, characterized in that a substrate is provided on at least one surface thereof with a first circuit pattern using known methods and a layer of a pre-formed foil of a thermoplastic copolymer is applied over the surface or surfaces provided with a circuit pattern, then the surface or surfaces of the copolymer film are treated with a solvent and an oxidizing agent and the surface or surfaces thus pretreated are provided of an additional circuit pattern or patterns and, if desired, the steps of supplying the formed circuit patterns are repeated with layers of preformed films of the thermoplastic polymer; wherein the surface or surfaces of the polymer film are provided with an additional circuit pattern or patterns and this procedure is repeated until all of the circuit pattern layers are formed. 18. Method according to claim 17, characterized in that the conductors of the circuit patterns of different layers are connected by providing holes in selected areas and forming a metal deposit on the bands of the holes, thus making electrical connections between the respective conductors are formed. A method according to claim 17, characterized in that the preformed film is removed from the areas of the conductors to be connected to conductors to be formed on the surface of the film and a connection is formed between the conductors by metal deposition which extends from the respective conductor on the film surface but the unprotected region of the respective conductor of the underlying layer, thus covering metal deposition at least a portion of the unprotected regions of the conductors. 20. A method according to claim 17, characterized in that the circuit pattern is formed by catalyzing the surface of the polymer foil to render it catalytic to receive electrolessly deposited or deposited metal. 800 2 5 14 - 29 - g 21 * Process according to claim 18, characterized in that the circuit pattern or patterns is or are formed by catalyzing the surface of the polymer film to make it catalytically formed for electroless incorporation. 5 the metal deposits} after which the pattern areas are provided with a metal deposit formed by electroless metal deposits alone or in combination with electrolytic coating. 22. Method according to claim 21, characterized in that the total surface of the polymer foil is catalyzed and metallized and the conductor pattern is formed using known masking and etching methods. 23. A method according to claims 20 and 21, characterized in that the polymer foil comprises an agent which is catalytic for receiving electrolessly formed metal deposits. 24. A method according to claims 12-17, characterized in that the substrate is provided with an agent which makes it catalytic to receive electrolessly formed metal deposits. 800 2 5 14