EP1274880A2 - Procede d'activation selective a base metallique de surfaces de substrats pour le depot metallique par voie chimique humide sans courant exterieur et moyen correspondant - Google Patents

Procede d'activation selective a base metallique de surfaces de substrats pour le depot metallique par voie chimique humide sans courant exterieur et moyen correspondant

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Publication number
EP1274880A2
EP1274880A2 EP01929548A EP01929548A EP1274880A2 EP 1274880 A2 EP1274880 A2 EP 1274880A2 EP 01929548 A EP01929548 A EP 01929548A EP 01929548 A EP01929548 A EP 01929548A EP 1274880 A2 EP1274880 A2 EP 1274880A2
Authority
EP
European Patent Office
Prior art keywords
metal
vesicles
activator
precursor
activator metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01929548A
Other languages
German (de)
English (en)
Inventor
Stephan Lange
Veniamin Galius
Stephan Fiedler
Monika Hannemann
Wolfgang Scheell
Herbert Reichl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE2000117887 external-priority patent/DE10017887C1/de
Priority claimed from DE2001113857 external-priority patent/DE10113857A1/de
Application filed by Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Publication of EP1274880A2 publication Critical patent/EP1274880A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02—Making microcapsules or microballoons
    • B01J13/04—Making microcapsules or microballoons by physical processes, e.g. drying, spraying
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1603—Process or apparatus coating on selected surface areas
    • C23C18/1607—Process or apparatus coating on selected surface areas by direct patterning
    • C23C18/1608—Process or apparatus coating on selected surface areas by direct patterning from pretreatment step, i.e. selective pre-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
    • C23C18/28—Sensitising or activating
    • C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
    • 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
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/18—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material
    • H05K3/181—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material by electroless plating
    • H05K3/182—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material by electroless plating characterised by the patterning method

Definitions

  • the present invention relates to a wet chemical, external currentless method for the continuous or discontinuous generation of thin metallic layers (in particular finely structured layers in the ⁇ m-nm range) on organic and inorganic, preferably inert, dielectric substrate support materials such as polymers, ceramics and semiconductor materials, and in particular a method for selective, metal-based activation of these materials as preparation for the subsequent metallization.
  • Substrates of the type available with thin metallic structures and layers are widely used in microelectronics. They are suitable as function carriers of essential components of rewiring, 5 printed circuit boards or integrated circuits.
  • the metallized substrates of the present invention can also be used in optics and microtechnology in general, as well as for decorative purposes or as printed matter.
  • Electromagnetic radiation of a certain wavelength and energy density is projected through a partially transparent structure that acts as a positive or negative template onto the substrate coated with sensitive components (photoresist) over the entire surface. In subsequent etching and rinsing steps, the 5 projected structure is exposed (developed).
  • Electroplating metal depositions avoiding chemically reactive steps are also known, for example deposition of Pd / Sn colloids from an acidic, colloidal Pd-Sn colloid system on pre-etched plastic, conversion by ion exchange into Pd / Cu and deposition of the desired (noble ) Metal from a suitable electrolyte solution (Paatsch W., metallizing plastics metal surface 1998 5230-34).
  • electrolyte solution Paatsch W., metallizing plastics metal surface 1998 5230-34.
  • additive and semi-additive techniques for the metallization of conductive or non-conductive substrates in particular the surfaces of organic polymers, ceramics or semiconductor materials, chemical (electroless) metallization processes are also used, which are generally referred to as chemical or chemically reductive processes.
  • the usually inert surfaces of the substrates to be metallized have to be activated if it is a matter of non-active materials such as polymers or ceramics.
  • the activation consists in the application of catalytically active substances or the formation of such substances on wetted layers of the surface in contact with corresponding solutions and suspensions (see, for example, Fundamentals of Microfabrication,
  • the substrate surfaces can be chemically or physically roughened beforehand and thus their surface energy (wettability) can also be changed. Then the surfaces are brought into contact with a solution of suitable metal ions, which are then reduced and deposited as metal nuclei (atomic clusters) and bring about the activation. For this, e.g. Tin and very often used palladium.
  • metal layers for example nickel layers, are built up thereon, which are additionally provided with surface protection, e.g. Gold, can be provided. See e.g. Fundamentals of Microfabrication, op. Cit., B. Endres, Galvanotechnik D-88348 Saulgau, 88/1997) No. 5 or ZEV-PCB 7-8 / 97, The new surfaces of the PCB (anonymus).
  • the activator solution is usually applied to the substrate to be activated by dipping into a solution or suspension containing the activator or one of its precursors. Subsequent dipping steps with further solutions ultimately lead to the generation of the metal nuclei (metal clusters) mentioned on the areas provided for the metallization. Surface activation by incubation directly in precious metal colloids and their destabilization on the surface of the treated substrate is also possible. However, these must be stabilized, because otherwise the individual metal atoms or clusters would aggregate and precipitate out in lumps, grains or layers. (Stabilization of metal colloids or clusters generated in situ is also from other fields of technology such as Synthetic chemistry or exhaust gas treatment known).
  • Dispersant produced which gives the particles a charge and thereby stabilizes them. Between the individual dipping steps, excess components must be removed by intermediate dives (washing steps). This is the only way to prevent the spread of metal germs in the immersion solutions, to avoid coagulation of the colloid and to keep the baths' service life long enough.
  • DE 197 47 377 A1 proposes a method for preparing the production of very finely structured metallic layers. According to this method, it is provided that metal ions are spatially separated from a further compartment on a substrate, the layer causing the spatial separation containing proteins which can induce a vector-induced light-induced gradient, for example a concentration gradient, which reduce or reduce the metal ions can make a reduction accessible.
  • the gradient is built up and the metal is reduced by selective exposure at those locations where the activation is to take place. If the compartment consists of metal ions packed in vesicles and the vesicle environment, the vesicles must be opened so that the metal can act on the surface of the substrate.
  • This method requires a selective exposure of a part of the layer applied to the substrate in order to enable the required structuring.
  • Classic printing processes can also be used to apply metals directly to surfaces.
  • stencil printing technology can be used to apply solder deposits (solder bumps, wafer bumping) and form them by remelting. Grid dimensions achieved here are in the range of 200-250 ⁇ m (Kloeser, J. et al., Pan Pacific Microelectronics Symposium and Tabletop Exhibition, Mauna Lani (USA), Feb. 10-13, 1998).
  • (screen) printable solders microparticles are introduced into a polymer matrix and thus achieve the consistency required for printing. When the microparticles fuse, such a matrix can serve as a flow aid. The ones usually used here
  • metal particles (5-75 ⁇ m size scale) are not suitable as activators for (wet) chemical metal deposition.
  • an ink set which comprises a microemulsion-based, black ink with water-insoluble pigment and an aqueous, colored ink, the ionic strength of which is higher and which causes the pigment to precipitate on contact with the black ink, thereby causing a Bleeding is prevented.
  • EP 395096 B1 deals with exposure to a laser beam.
  • Printing and other dispensing methods have the advantage over a flat treatment of surfaces that a subsequent step for the selective activation of a part of the flat materials can be omitted.
  • the object of the present invention is to provide a method for the selective, metal-based activation of substrate surfaces, with which, after wet chemical, electroless metallization, very fine-structured metallic layers can later be obtained on a substrate.
  • the method should be carried out using conventional printing or dispensing techniques and at room temperature and should be independent of the material of the substrate to be metallized.
  • the use of environmentally harmful components should be avoided or minimized where possible, also by reducing the number of process steps and Process chemicals.
  • the realizable structure width should preferably be less than the raster width of about 3 ⁇ m that can be achieved in offset printing.
  • the metal deposition by which the surface to be metallized is activated does not have to be a blanket deposition. It is sufficient to deposit traces of a suitable activator metal on the substrate surface. High precision of the deposition limits should be achievable.
  • the deposited metal nuclei have catalytic activity in the subsequent steps of wet chemical deposition of further materials.
  • the object of the invention is also to provide a method for metallizing surfaces using this activation method.
  • the object is achieved by the provision of a method for the selective, metal-based activation of substrate surfaces for wet chemical, electroless metal deposition, characterized in that the substrate surface is activated at the desired locations with activator metal, which as such or in the form of a precursor using vesicles was selectively transported to these places on the surface.
  • the present invention proposes to encapsulate the activator metal as defined below in the interior of liposomes or other vesicles.
  • the activator metal stabilized in this way is applied to the surface to be metallized by a printing process or in another way (dispensing process, stamping techniques). In contrast to surface treatments with later selection of the surfaces to be activated, this material is applied from the outset exclusively to these surfaces. Since the activator metal is encapsulated, the membrane of the vesicles is then opened so that the activator metal reaches the substrate surface. There, it can then be overlaid with metal using conventional, currentless metal deposition processes, for example the additive and semi-additive techniques mentioned in the introduction. Figure 1 illustrates this method using an example.
  • a precursor of the activator metal is used, this is also encapsulated in the interior of the vesicles. They can be converted into the activator metal before or with or after opening the vesicle membrane. At least in the latter case, the vesicles must already have been deposited on the substrate surface at the time of the conversion.
  • vesicles the outer side of which is coated with activator metal, which is present in chemical elemental form (as a "metal cluster", see next paragraph), either vesicles that are also in their interior Activator metal or a precursor of
  • Activator metal as described for the above embodiments, or preferably contain those vesicles which are free of activator metal or precursors of activator metal in their interior.
  • the vesicles serve as transport material for the metal nuclei which have already been formed, and if the transport takes place exclusively via the outer surface, the vesicles on the substrate surface need not be opened.
  • Activator metal is to be understood here as meaning metals and metal compounds which have such a chemical and / or physical structure or environment that after application to a surface they have catalytic activity in chemical, electroless metallization baths and thus - catalytically - the deposition of metals can effect from these baths.
  • An important group includes the solid surface modifiers, which are already known in chemically bound form as ions or complex compounds and are known and known as ionogenic activators.
  • Particularly suitable as ionogenic activators are transition metals that can be easily reduced (e.g. from Pd (II) to Pd (0)) and are complexed with redox-sensitive ligands such as nitrite or other oxo, ambident or multidentate ligands. Examples of multidentate ligands are ring-forming diamines or diketonates.
  • multidentate ligands are ring-forming diamines or diketonates.
  • a further, at least partially different activator group comprises the metals, which are present in chemical elemental form and act as atomic clusters on surfaces, which - also - in the first and - exclusively - can be used in the third embodiment of the invention.
  • metal clusters are intended to mean that a collection of several (preferably at least 10, more preferably at least 25, particularly preferably about 50 to 600) atoms are organized in a composite with a metal character. These can preferably be atoms with a formal valence of zero, but clusters with charge components on the metal can also be used.
  • LH Gade coordination chemistry (Verlag Wiley-VCH, Weinheim 1998).
  • metal clusters are described as molecules that contain a finite number of metal atoms, which are linked to a significant extent by metal-metal bonds. From the explanations for this it also appears that the metal clusters described there, which are clusters stabilized with ligands, can also be regarded as “metal crystallites” in a ligand shell or as ligand-stabilized colloids at higher metal atom numbers.
  • metal clusters from the series are shown which, due to the packing structure of the metals, have certain preferred metal atom numbers, the so-called "magic numbers".
  • the metal clusters suitable for the present invention as activator metal only include those which have the catalytic activity mentioned above in electroless chemical metallization baths. The reference should therefore only refer to the number and structure of the metal atoms.
  • the metals or metal compounds which can be used in the clusters or ionogenic compounds mentioned are selected with regard to the material to be deposited; they are known to the person skilled in the art. Examples are tin, noble metals or transition metals (e.g. the VIII. Group such as Co, Ni Ru, Rh, Pd, Os, Ir, Pt, the V. group such as Nb and the I. group with Cu, Ag, Au).
  • Suitable ionogenic compounds are, for example, chloro or nitro complexes such as tetranitropalladate with potassium, sodium, lithium or ammonium ions as counterions and palladium chloride.
  • precursors of the activator metal are to be understood as meaning those substances which can be converted into activator metal by reaction with a suitable reaction partner at the intended site of action on the substrate surface or beforehand within the vesicles. These are, for example, chelated metals that are dechelated by the reaction partner, complexed metals which are reduced by the reactant (for example those which are described as starting materials for stabilized cluster suspensions in the literature), or metal ions which are reduced by ion exchange, pH change or the like.
  • the reaction partner can accordingly be a reducing agent, for example a reducing agent customary in color or black and white photography, for example 1,4-benzenediamine, 1, 2,3-benzenetriol, m-hydroquinone, p-hydroquinone or p-hydroxyphenylglycine. It is particularly preferred to select a reaction partner which, depending on another chemical property such as the presence of certain ions (in particular the pH value), brings about a reduction in the precursor of the activator metal.
  • This system represents a redox system in which the potentials of the reactants depend on the chemical property mentioned, in particular on the pH value.
  • An example of such a redox system is the combination of palladium (II) amine complex / formate.
  • the reactant which can convert the precursor into the activator metal
  • the reactant can also be packed in vesicles mixed with the vesicles containing the precursor and applied to the substrate surface.
  • the vesicles are opened, both the precursor and its reaction partner are released; the conversion to the activator metal takes place. This is in
  • FIG. 3 shows schematically: vesicles A with a precursor of the activator metal are in a mixture with vesicles B which contain a reaction partner. Separated by the membrane shells of the vesicles, the conversion to the activator metal C is not possible; this takes place only after opening the vesicles on the substrate surface. Alternatively, after application to the substrate surface and opening of the vesicle membrane, the vesicles containing the precursor can be washed with a solution which contains the reactant, which causes the conversion to the activator metal, or the reactant is in the dispersant for the vesicles. This variant is illustrated in FIG.
  • vesicle A is shown with a precursor of the activator metal as a dispersion in reaction partner B.
  • the conversion to the activator metal C takes place only after opening the vesicle membrane on the substrate surface.
  • the vesicles can be brought into contact with a reaction-triggering factor, for example with electromagnetic radiation (for example UV radiation).
  • electromagnetic radiation for example UV radiation.
  • the concentration gradient of a membrane-permeable ion species, for example of protons can be used for this purpose, these ions being enriched or depleted in the vesicles, as a result of which the conversion takes place.
  • the deposition of metal atoms with cluster formation on the vesicle surface for the production of the vesicles according to the third embodiment of the invention can be carried out from preferably aqueous solutions of corresponding metals by reduction according to known methods.
  • the ionic strength of the preferably aqueous dispersion medium used also contributes to the variation of the properties of a vesicle preparation with metal clusters adhering to the outside of the membrane (e.g. with regard to the prevailing charge and therefore presumably also correlates with the binding capacity).
  • the higher the ionic strength the slower the metal deposition on the surface of the vesicles. If you choose slow deposition, the loading state of the vesicles can be selected very precisely.
  • the vesicles which are intended for the transport of the activator metal to the site of deposition can be made from any suitable amphiphilic molecules such as lipids or anionic, cationic or in particular nonionic surfactants of natural or synthetic origin in aqueous or non-aqueous liquids be formed.
  • suitable amphiphilic molecules such as lipids or anionic, cationic or in particular nonionic surfactants of natural or synthetic origin in aqueous or non-aqueous liquids be formed.
  • the membrane-forming properties of fatty acids, longer-chain alcohols and lecithin or of phospholipids are known.
  • Preferred is the use of conventional lipid vesicles (liposomes) made of, for example, phospholipid bilayers; however, the choice of suitable substances is not critical and is therefore not restricted to this.
  • Many phospholipids occur in nature in smaller or larger amounts. For example, phosphatidylcholines are found in egg yolk.
  • phospholipids fall into two main groups, one comprising a derivatized glycerol molecule and the other having a sphingosine backbone.
  • Natural, but also synthetic phospholipids can be used for the present invention.
  • phosphatidylcholines there are, for example, phosphatidylethanolamine, phosphatidylserine or phosphatidylglycerol, but also the synthetic surfactant Cetylpyridinium chloride suitable.
  • egg lecithin or plant-derived phospholipids such as soybean lecithin, but also cholesterol or glycolipids are suitable.
  • the liposomes can also contain further constituents.
  • lipid membranes substances such as cholesterol or other substances which have hydrophobic or hydrophobic regions and which, for example, influence the permeability and flowability of the membrane can be embedded in a lipid membrane.
  • liposomes When the term “liposomes” is used in the present application, this is not meant to be limited to lipid vesicles; rather, all vesicles, including those made of other materials, for example the “niosomes” 1 formed from nonionic surfactants, are to be included.
  • Tetraalkylammonium compounds may be mentioned as an example of synthetic amphiphiles; Representatives of these compounds are the dialkyldimethylammonium halides (chlorides, bromides), from which vesicles suitable for the invention can be produced.
  • the membrane-forming substances can also contain charged or uncharged head groups-carrying synthetic compounds and substances of natural origin with one or more long-chain (C 6 -C 20 preferably C 12 -C 18 ) saturated or also simply or include polyunsaturated side chains.
  • the head group can be, for example, an amine coupled via a phosphoric acid ester bond (choline, ethanolamine, etc.).
  • the crystallinity (liquid crystal - gel phase transition) and the charge of the membrane are the decisive variables which are responsible for the adsorption of metal clusters at least on the outer surface of the vesicle and also for their further growth.
  • the nucleation (the locally occurring growth process) of metal clusters on surfaces by coalescence of individual atoms takes place here on a liquid-crystalline surface.
  • the typical characteristics of the membrane former (used as a liposome base) influence the characteristics of the clusters growing on the vesicle surface.
  • niosomes is derived from a combination of the terms “nonionic” and “(lipo-) somes”
  • a factor for the targeted influencing of the degree of order / mobility of membrane formers as typical as phospholipids is the temperature, but also the presence of factors forming membrane domains (eg proteins or cholesterol).
  • the liposomes usually have diameters in the range from about 10 nm to about 1 ⁇ m, more preferably from about 50 to 500 nm and typically about 100-200 nm. In an essential embodiment, they are with a solution of the ionogenic compound (or a mixture of several such Compounds) or a suspension of metal clusters or a precursor of the activator metal. In a further embodiment, the activator metal adheres to the outwardly facing side of the lipid bilayer of the liposomes. The activator metal can be attached to the outside of the liposomes in addition or as an alternative to filling the vesicles.
  • a solution of ionogenic activator metal, a metal suspension or an activator metal precursor can be encapsulated by known methods.
  • the lipid intended for the liposomes and the corresponding metal salt of the ionogenic activator optionally with the addition of further salts / components, such as potassium or sodium salts, to adjust the ionic strength required for the stability of the vesicles or charged surfactants for the purpose of a defined charge of the vesicles , placed in water, and a liposome suspension is produced using a common method.
  • Polymeric stabilizers can also be added.
  • liposome suspension also known as dispersion or emulsion, since such systems do not fit into the traditional solid / liquid or liquid / liquid system
  • extrusion processes high-pressure filtration techniques, high-speed filtration techniques, homogenization techniques, ultrasonic processes or high-speed stirring.
  • the non-encapsulated ionogenic activator can, if desired, be removed from the suspension by washing or filtering the suspension or by column chromatography or by a dialysis method.
  • An encapsulated metal cluster suspension with activator metal properties is not known in the prior art.
  • the metal cluster suspension obtained can be cleaned of constituents of the starting components, as already described above for the encapsulated ionogenic activator.
  • a liquid, possibly also pasty product is obtained, which may already as such, i.e. without further formulation, can be used as a printable paste.
  • the vesicles In order to load the outer surface of the vesicles with metal clusters, the vesicles are brought into contact with a solution of a corresponding metal compound, whereupon the metal atoms are brought into a state either by reduction or by release of the metal atoms from metal atom complexes already in the formal oxidation state "0" from which they aggregate into clustem.
  • suitable metal compounds for this are those which have been described in detail above under "precursors of the activator metal", that is to say all those substances which can also be converted into activator metal by reaction with a suitable reaction partner at the intended site of action on the substrate surface or within the vesicles. These are also suitable for use in solutions in which the outside of the vesicles can be loaded with metal clusters, regardless of whether the vesicles also contain metal in some form or not.
  • the quantitative ratios of the liposome reaction batch also determine the characteristics of the metal clusters growing on the vesicle surface.
  • concentrations the ionic strength
  • type e.g. value
  • pH of the aqueous dispersion medium influence the effective surface charge (zeta potential) of dispersed microparticles, including liposomes and other vesicles. These parameters can therefore be used specifically to control the growth of the metal clusters on the vesicle surfaces.
  • the reaction can be “switched on” at any time and usually by reversing the chemical conditions can also be “switched off” again.
  • This allows the desired amounts of metal to be deposited and thus also the cluster size or amount to be controlled very well, especially since, as mentioned above, the rate of the reaction can be regulated via the ionic strength of the suspension. This can be clearly seen from the example of a reduction of Pd by formate: the reaction can be controlled via the pH value.
  • Vesicles in the palladium complex solution cause the reduction to start, the addition of bases stops them. The addition of salts slows them down.
  • the liposomes have been separated from their suspension by one of the abovementioned steps, they can then be resuspended.
  • the viscosity of the suspension is easily adjustable at room temperature. This can be done, for example, by adjusting the ratio of liposomes to suspending agents.
  • the suspension can thus be concentrated by customary methods in order to bring its viscosity to a value which it can use as a printing paste or for other application makes suitable.
  • a thickener such as polyvinylpyrrolidone can be added to the suspension.
  • the liposome concentration is chosen in a suitable manner by the person skilled in the art and is usually in the range between 0.1 and 50% by weight.
  • the substrates that can be prepared for the metallization using the method according to the invention are not restricted.
  • examples are polymers such as cyanate esters, phenolic or epoxy resins, polyimides, phenolic resins or benzocyclobutensiloxanes, ceramics or semiconductor materials. Such substances are used in microelectronics.
  • the coating of surfaces made of polymer materials is increasingly gaining economic importance; both organic and inorganic-organic polymers can serve as a substrate.
  • the present method is particularly suitable for the production of wiring structures on printed circuit boards or foils for multilayer printed circuit boards.
  • the technique with which the liposomes loaded with activator metal are selectively applied to the surface of the substrate to be activated is also not critical. So all common printing techniques, but also stamping techniques or the like can be used.
  • the stamp used can be profiled and homogeneously wettable or consist of an almost planar surface that has selectively wetting areas due to chemical modification (modern offset principles).
  • a technique well suited to the present invention is offset printing.
  • the expected resolution of the structures that can be applied depends on the printing technology and the printing press used as well as the consistency of the liposome paste. Structures with widths and distances down to a few 10 to 100 nm are available.
  • the minimal edge blur is in the range of the liposome diameter.
  • surface unevenness such as depressions and openings (eg bores) that go beyond material roughness can be wetted and filled.
  • the liposome paste After the liposome paste has been applied, it is dried for fixation, the choice of drying parameters (temperature, time) being suitably based on the properties of the liposomes.
  • the drying step can be designed so that the liposome content is released. This is possible, for example, by incubating the substrate provided with the liposome paste at approximately 60-80 ° C. Such an incubation is commercially available
  • Metallization baths e.g. nickel-phosphorus, nickel-boron or copper bath
  • the lipids used for the preparation of the liposomes have a phase transition temperature below the temperature range required for the metallization and the incubation in the metallization bath is preceded by the usual conditioning rinsing baths which bring about an opening of the liposomes.
  • the printed liposome paste can be rinsed with a membrane-lytic medium.
  • Numerous surface-active substances surfactants
  • Saponins Saponins
  • the membrane lysis need not be complete; it suffices to create perforations or "holes" through which the contents of the liposomes come into contact with the environment.
  • the applied liposome paste can, if necessary, be cured, in which case it must contain appropriate constituents, for example thermally or radiation-induced curable mono- or polymers.
  • the substrate is preferably pretreated. Layers obtained after pretreatment are generally more stable because the adhesion is improved. The pretreatment steps depend on the chemical composition of the substrate. For example, the roughening of the polymer surface by dissolving / swelling - etching - cleaning is effective (Schröer, D. et al., Electrochimica Acta 1995 40, 1487-1494; or Schmidt, R. et al., Galvanotechnik 1996 87, 2015-2022) ,
  • the surface activation of printing technology described according to the invention is easily divided into known and industrially practiced process sequences, so that its detailed description can be dispensed with here. (See Suchentrunk, R. Metallizing of Plastics- A handbook of Theory and Practice Finishing Publications Ltd 1993; DE 196 39 898 A1).
  • the substrate which is preconditioned according to common processes, is directly suitable for building up metal layers in corresponding commercial autocatalytic baths (e.g. Schmidt-Nickel 604 from Herbert Schmidt GmbH, Solingen, Federal Republic of Germany).
  • the method according to the invention differs as a purely additive method from conventional stamping techniques on copper-clad material in that the etching steps necessary in these subtractive techniques are completely eliminated here.
  • L- ⁇ -phosphatidylcholine type II-S from soybeans, Sigma catalog No. P5638 is at a concentration of about 5% in an aqueous solution of 10 mM K 2 [Pd (NO 2 ) 4 ] and 0.2M K 2 SO 4 pre-swollen
  • the mixture is subjected to an ultrasound treatment or homogenization, whereby lipid vesicles are formed, in the interior of which the metal activator is enclosed.
  • the lipid vesicles are chromatographed using a NAP-25 pre-filled gel cartridge (Amersham Pharmacia Biotech). The solution is freed from potassium nitropalladate.
  • Thin panes or foils of glass fiber reinforced epoxy resin polymer are incubated at room temperature for 5 minutes in a 20% aqueous solution of the adhesion promoter LUPASOL SK (BASF AG) in order to improve the adhesion.
  • the liposome paste prepared as above is applied to the dry substrate using a stamp. A 1-2 minute drying at 80 ° C. then takes place for fixation, the liposome membrane opening.
  • the subsequent deposition of an electrically conductive metal layer is carried out without current in a commercially available autocatalytic metallization bath (e.g. chemical nickel 604, Herbert Schmidt GmbH & Co. Germany).
  • a uniformly adhering nickel layer is formed at the areas printed with the liposome paste, which, depending on the intended area of application, is available for subsequent treatment (e.g. deposition of a copper or gold layer).
  • FIG. 5 shows a stamp impression of a liposome paste on printed circuit board base material FR4 produced in accordance with Example 1, which was reinforced in the nickel bath.
  • Example 2
  • a solution containing 2 mM tetramminopalladium dichloride and 200 mM potassium formate and having a pH of 8 is mixed with lipid in an amount of 0.2 to 40% by weight, based on the total weight of the solution.
  • the mixture is treated with ultrasound, resulting in lipid vesicles filled with solution.
  • an osmotically equivalent solution that is free of the redox system osmotic compensation by means of potassium sulfate or glucose
  • the chemical equilibrium of the redox system is increased by adding a suitable acid (slow dropwise addition of 0.5 M sulfuric acid until the pH Value has dropped to 5) moved to the palladium reduction side. Finely dispersed palladium particles form within the lipid vesicles.
  • the liposome suspension thus obtained is stable.
  • Their consistency depends on the amount of lipid used. It ranges from thin, watery (0.2 to 5% by weight lipid) to filthy-viscous (approx. 40% by weight lipid) and can be conditioned directly for stamp application. After the stamp imprint has dried on, the substrate can be used for the selective deposition of metal layers as described above.
  • a liposome dispersion was made from soybean lecithin (II-S "Asolectin” from SIGMA-Aldrich, catalog number P-5638) and aqueous using the conventional methods (ultrasonic generator of the type "Bransson Sonifier 450, output stage 3, duty cycle 30%) Salt solutions of different concentrations: A1: 0 mol / IK 2 SO 4 in distilled water A2: 100 mmol / l K 2 SO 4 in distilled water A3: 500 mmol / l K 2 SO 4 in distilled water. For this purpose, 500 mg of lipid in 20 ml of the aqueous salt solution were pre-swollen with stirring for about 1 hour and then sonicated in a test tube for 10 minutes. Furthermore, stock solutions from
  • the pH of the homogeneous dispersion (according to pH 7.85) was then adjusted to pH 4.8 using (about 3 ml) 0.1 mol / IH 2 SO 4 .
  • the mixture was then continuously stirred in a water bath at 35 ° C. (magnetic stirrer). With the onset of metal cluster formation on the outer surface of the lipid, recognizable, for example, from a gradual browning of the mixture, aliquots were removed at intervals of 5 minutes and a pH of 8.0 was adjusted therein by adding 0.1 mol / l aqueous KOH in each case , Depending on the chosen point in time of stopping the reaction by resetting the pH in the reaction mixture to pH> 8.0, metal clusters of different sizes can be obtained in this way.

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Abstract

L'invention concerne un procédé d'activation sélective à base métallique de surfaces de substrats pour le dépôt métallique par voie chimique humide sans courant extérieur. Le procédé selon l'invention est caractérisé en ce que la surface du substrat est activée avec un métal activateur transporté sélectivement en tant que tel ou sous la forme d'un précurseur vers la zone de la surface à activer au moyen de vésicules. L'invention concerne également un mélange de vésicules contenant une vésicule remplie d'un précurseur de métal activateur ainsi qu'une vésicule remplie d'un réactif destiné au précurseur de métal activateur, ce réactif pouvant transformer le précurseur de métal activateur en métal activateur dès que les membranes de vésicules sont ouvertes. Le mélange de vésicules selon l'invention peut se présenter en tant que tel ou dans un agent de suspension et peut être mis en oeuvre dans le procédé selon l'invention.
EP01929548A 2000-04-11 2001-04-11 Procede d'activation selective a base metallique de surfaces de substrats pour le depot metallique par voie chimique humide sans courant exterieur et moyen correspondant Withdrawn EP1274880A2 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE10017887 2000-04-11
DE2000117887 DE10017887C1 (de) 2000-04-11 2000-04-11 Verfahren zur selektiven metallbasierten Aktivierung von Substratoberflächen für die nasschemische, aussenstromlose Metallabscheidung und Mittel hierfür
DE10113857 2001-03-21
DE2001113857 DE10113857A1 (de) 2001-03-21 2001-03-21 Metallcluster-beladene Vesikel, Verfahren zu ihrer Herstellung und Verwendung von Vesikeln als Hilfsmittel für die Flockung von Metallsuspensionen
PCT/EP2001/004195 WO2001077409A2 (fr) 2000-04-11 2001-04-11 Procede d'activation selective a base metallique de surfaces de substrats pour le depot metallique par voie chimique humide sans courant exterieur et moyen correspondant

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EP1274880A2 true EP1274880A2 (fr) 2003-01-15

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WO (1) WO2001077409A2 (fr)

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Publication number Priority date Publication date Assignee Title
GB2382798A (en) * 2001-12-04 2003-06-11 Qinetiq Ltd Inkjet printer which deposits at least two fluids on a substrate such that the fluids react chemically to form a product thereon

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US3958048A (en) * 1974-04-22 1976-05-18 Crown City Plating Company Aqueous suspensions for surface activation of nonconductors for electroless plating
US5332646A (en) * 1992-10-21 1994-07-26 Minnesota Mining And Manufacturing Company Method of making a colloidal palladium and/or platinum metal dispersion
US5560960A (en) * 1994-11-04 1996-10-01 The United States Of America As Represented By The Secretary Of The Navy Polymerized phospholipid membrane mediated synthesis of metal nanoparticles
WO1998019217A1 (fr) * 1996-10-25 1998-05-07 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Procede permettant de preparer la production de couches metalliques structurees a l'aide de proteines
DE19740431C1 (de) * 1997-09-11 1998-11-12 Atotech Deutschland Gmbh Verfahren zum Metallisieren eines elektrisch nichtleitende Oberflächenbereiche aufweisenden Substrats

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Title
See references of WO0177409A3 *

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WO2001077409A2 (fr) 2001-10-18

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