WO2001003856A1

WO2001003856A1 - Method of forming a thin metal layer on an insulating substrate

Info

Publication number: WO2001003856A1
Application number: PCT/US2000/018605
Authority: WO
Inventors: Richard W. Carpenter; Edward J. Reardon, Jr.
Original assignee: Shipley Company, L.L.C.
Priority date: 1999-07-09
Filing date: 2000-07-07
Publication date: 2001-01-18
Also published as: KR20020048369A; AU6207100A; WO2001003856A8; CN1368904A; EP1222034A1

Abstract

The invention is directed to the formation of a very thin, uniform metal layer (306) on a resin substrate (307) such as a copper layer on an epoxy-based substrate. Such copper/resin laminates (306, 307) are useful, for example, as blanks for forming printed circuitry.

Description

METHOD OF FORMING A THIN METAL LAYER ON AN INSULATING SUBSTRATE

The invention is directed to formation of a very thin, uniform metal layer on a resin substrate, such as a copper layer on an epoxy-based substrate. Such copper/resin laminates are useful, for example, as blanks for forming printed circuitry.

Background of the Invention:

Two common methods of foπriing printed circuit boards are "Print and Etch" and "Pattern Plating".

In the "print and etch" process, copper foil is laminated to both sides of fiberglass/epoxy prepreg (uncured) under heat and pressure to form a circuit board blank having copper layers on both sides of a relatively rigid dielectric layer. The copper most typically is 1 oz copper having a thickness of 1.2 mils (30 microns). Through and blind vial holes re drilled into the blank. The vias are seeded with palladium. The entire circuit board is then electroplated with copper to provide electrical connection through the via holes. This copper plating is typically to a thickness of 1.2 mils, bringing the total thickness of the copper on both sides of the boards to 2.4 mils (60 microns). Photoresist layers are applied, exposed, and developed on both sides of the board. The copper is etched, e.g., with cupric chloride, and the resist is stripped.

In the "pattern plate" process, a circuit board is formed in the manner of the "print and etch" process. Blind and via holes are drilled. Photoresist is applied, exposed and developed. The via holes are platinum-seeded. Copper is electrodeposited on the exposed circuitry traces and through the via holes. The exposed copper circuitry traces and via holes are then plated with a metal which acts as a resist, such as tin, tin/lead or gold. The resist is stripped. The board is then etched, removing copper from those regions not protected by the plated resist metal. Again, the total thickness of the circuitry traces (exclusive of the plated metal resist) is typically about 1.2 mils (30 microns).

Both print and etch and pattern plating processes are used to make fine line printed circuit boards having line widths down to 2 mils (50 micron) wide. The advantage of the print and etch method is that it produces better line height control. The pattern plating method makes it somewhat easier to produce small line width circuits. Both methods will benefit from circuit board blanks produced by the method of the present invention.

As printed circuitry becomes more complex and with the ever increasing desire for miniturization, there is always a desire for finer resolution of printed circuitry. One of the limitations of printed circuitry resolution is the thickness of the copper layer(s) of the printed circuit board blank which are etched; the thinner the metal layer that is etched, the higher the resolution that may be achieved. During copper etching, the copper is dissolved not only downward toward the fiberglass/epoxy dielectric base material, but laterally as well, the lateral etching diminishing the resolution of the etched traces. Assuming the dimensions given above, etching in the print and etch method is through

2.4 micron (60 micron) copper layers; etching in the pattern plate method is through a 1.2 mil (30 micron) copper layer. The present invention intends to substantially reduce these thicknesses, thereby providing finer printed circuitry resolution.

The present invention is directed to providing circuit board blanks having very thin layers of continuous, non-porous copper on fiberglass/epoxy panels, i.e., between about 0.5 and about 3 microns thick. The copper layers on a circuit board blank need only be thick enough to carry current sufficient for effective electroplating subsequent to via hole formation. For this purpose, it is found that copper as thin as 0.5 microns is sufficient to carry the current necessary to support an efficient plating process. Copper layers in the 0.5 to 3 micron range have negligible thicknesses compared to the conventional 1.2 mil thick foil layer or the 1.2 mil thick electrodeposited additional thickness of copper.

In the print and etch method, starting with a negligible thickness copper layer of the blank and plating 1.2 mil of additional copper, the copper that is etched is 1.2-1.3 mils thick instead of 2.4 mils.

Assuming the dimensions discussed above, in the pattern plate method, only the foil originally part of the circuit board blank is etched. A foil layer between 0.5 and 3 microns is rapidly etched, thereby minimizing undercutting of the circuitry traces which are primarily comprised of the electrodeposited copper.

Accordingly either the print and etch method or the pattern plating method benefits when the initial copper layer of the circuit board blank is very thin.

Chemical vapor deposition (CVD) is a well known technique for depositing coatings by providing a gaseous reactant material which reacts adjacent to, or on, a substrate surface to produce a solid deposit or coating on that surface. A recent development of the CVD process, referred to as Combustion Chemical Vapor Deposition, or CCVD, is described in United States Patent No. 5,652,021, and is incorporated by reference herein. The reactants in that process are fed dissolved or suspended in a liquid, which can be a fuel, and which is sprayed into a reaction zone from a nozzle using an oxidizing gas as the propellant. The sprayed mixture is either ignited producing a flame, or is introduced into a flame, while a substrate is maintained near the flame's end. The reactants, which vaporize either prior to or in the flame, produce a deposited film on the substrate. The patent describes a number of prior CVD processes, including some which feed gaseous or vaporized reactants, some which use a sprayed or atomized solution, and some which feed reactive solid powders. The patent also describes a number of alternative coating techniques including spray pyrolysis wherein solutions are sprayed onto a heated substrate where they pyrolyze to form a coating, and techniques wherein a solid coating material is either melted or vaporized in a flame, plasma or other heating device and splattered or condensed on a substrate to form a coating. The techniques taught in U.S. Patent No. 5,652,021 can be used to produce thin layers of zero valence metals, particularly if the metal is resistive to oxidation, platinum being an example of a metal which can be easily deposited by CCVD. More reactive metals, such as copper, can be deposited by the method of this patent in the reducing part of the flame. However, control is difficult due to the oxidative nature of the flame.

A further improvement of the CCVD process is described in U.S. Patent Application Serial No. 08/691,853, filed 2 August 1996, and which is hereby incorporated by reference. This application describes a CCVD process wherein the coating precursor reactant is provided in admixture or solution in a liquid feed stream which is pressurized to near its critical pressure and heated to near its supercritical temperature before being directed through a nozzle or other restriction. The near-critical conditions of the liquid result in the feed stream being very finely atomized or vaporized as it is leaves the nozzle to enter a zone where the coating precursor reacts and either deposits a coating on a substrate or is recovered as a finely divided powder.

A refinement of the CCVD process which facilitates the deposition of a variety of zero valence, relatively reactive metals is described in U.S. Patent Application No. 09/067,975, the teachings of which are incorporated herein by reference. The apparatus and techniques taught in U.S. Patent Application No. 09/067,975 are directed to what is termed therein "Controlled Atmosphere Combustion Chemical Vapor Deposition" or CACCVD. This process facilitates the deposition of reactive metals, such as copper or nickel, in the zero valence state.

Examples of dielectric and resistive materials which are produced by CCVD and/or CACCVD are found in U.S. Patent Applications nos. 09/069,427, 09/069,679, and 09/198,285 the teachings of each of which are incorporated herein by reference. CCVD and/or CACCVD techniques can be used to deposit very thin, uniform, continuous metal layers on a substrate. Continuous metal films as thin as 0.1 microns have been produced. 0.1 micron metal films may be used in the present invention; however, if electrodeposition for circuitization procedures is to proceed at a reasonable rate, it is generally necessary that the deposited metal layer be at least about 0.5 microns thick. If CCVD and/or CACCVD techniques could be used to form the metal layer(s) of circuit board blanks, higher resolution could be obtained.

Thin metal layers could conceivably be deposited by CCVD and/or CACCVD directly onto cured dielectric materials, such as fiberglass-filled epoxy resin panels. However, CCVD and CACCVD apparatus is not currently available to circuit board manufacturers in the field to apply such layers to panels. Also, CCVD and CACCVD processes require very precise control, and quality and uniformity of deposition in the field cannot currently be guaranteed. Thus, it is preferred that these processes be carried out by a coater experienced in these techniques. The present invention is directed to materials and methods for providing transfer of very thin metal layers to dielectric material for formation of circuit board blanks.

It is a general advantage of the present invention to produce blanks for printed circuit boards having very thin metal layers, i.e., between about 0.1 and about 3 microns thick, preferably between about 0.5 and about 2 microns thick.

Summary of the Invention:

In accordance with the invention an electrically conductive metal is deposited on a fiat, smooth transfer substrate to a thickness of between about 0.1 and about 3 microns, preferably between about 0.5 and about 2 microns. The metal is typically copper, but may be other electrically conductive metals, such as nickel, platinum, silver, gold, tin, zinc, etc. The metal may be an alloy of two or more deposited zero valence metals or a metal layer doped with another element(s). The adhesion of the deposited zero valence metal to the transfer substrate must be sufficient for the deposited metal layer to remain bonded to the transfer substrate during shipping and handling, including, generally, reeling of the metal/substrate laminate. However, adhesion between the deposited metal layer and the transfer substrate must be sufficiently low that when the metal is laminated to a material to which the metal has greater adhesion, such as prepreg, the transfer substrate can be peeled away without damage to the film. In this regard, aluminum foil is a particularly preferred substrate, it being theorized that the alumina which forms at the surface bonds poorly to deposited metal layers. Polymeric films, such as polyimide, are also suitable transfer substrates, provided the film can withstand the deposition conditions, particularly temperature, and provided that the adhesion between the transfer film and the deposited metal layer is sufficiently low so as to permit subsequent release of the deposited metal layer from the film. After the metal layer is deposited on the substrate, the metal layer side is laminated to an un-cured or partially cured dielectric resin, such as a fiber glass-filled epoxy resin. (Two such structures can be pressed into opposite sides of an un-cured or partially cured resin layers to form a two-sided blank.) The resin layer is heated until it cures and hardens, securely bonding to the deposited metal layer(s). At this point, the deposition substrate is peeled away, leaving the thin, continuous, uniform metal layer(s) bonded to the cured resin and forming a blank for the production of high-resolution printed circuit boards.

The transfer method of the present invention is also useful for forming thin layer passives, particularly capacitors and resistors.

Brief Description of the Drawings:

Figure 1 is a schematic view, partially in section, of an apparatus for applying coatings by controlled atmosphere combustion chemical vapor deposition (CACCVD). Figure 2 is a close-up perspective view, partially in section, of a portion of the coating head used in the apparatus of Figure 1.

Figure 3 is a cross-sectional view of a deposition substrate having a metal layer deposited thereon.

Figure 4 is a cross-sectional view of two of the structures of Figure 3 laminated to a non-electrically conducting resin.

Figure 5 is a cross-sectional view showing the removal of the deposition substrates. Figures 6 A-E illustrate a process of forming thin film resistors by a transfer method in accordance with the invention.

Figures 7 A-E illustrate a process of forming thin film capacitors by a transfer method in accordance with the invention.

Detailed Description of Certain Preferred embodiments: For certain specialized applications the circuit board may be formed of precious metals, such as silver, gold, or platinum. For forming such metal layers, conventional CCVD techniques such as taught in above-referenced U.S. Patent Application No. 5,652,021 and above-referenced U.S. Patent Application No. 08/691,853 are conveniently utilized. However, most commonly, copper, and less commonly nickel, tin or other oxidizable metals are the choice for forming printed circuit boards. These are best deposited by CACCVD as described in above-referenced U.S. Patent application No. 09/067,975.

U.S. Patent application 09/067,975 provides an apparatus and method for chemical vapor deposition wherein the atmosphere in a controlled atmosphere zone is established by carefully controlling and shielding the materials fed to form the coating and by causing the gases removed from the controlled atmosphere zone to pass through a barrier zone wherein they flow away from said controlled atmosphere zone at an average velocity greater than 50 feet per minute, and preferably greater than 100 feet per minute. The controlled atmosphere zone is inclusive of the reaction zone, wherein the coating precursor is reacted, and the deposition zone, wherein the reaction product of the coating precursor deposits a coating on a substrate. The rapid gas flow through the barrier zone essentially precludes the migration of gases from the ambient atmosphere to the deposition zone where they could react with the coating, the materials from which the coating is derived, or the substrate.

Careful control of the materials used to form the coating can be provided by feeding the coating precursors in a fixed proportion in a liquid media. The liquid media is atomized as it is fed to a reaction zone wherein the liquid media is vaporized and the coating precursors react to form reacted coating precursors. Alternatively, the coating precursor(s) can be fed as a gas, either as the pure coating precursor or as a mixture in a carrier gas. The reacted coating precursors can be composed of partially, fully and/or fractionally reacted components, which flow to the substrate. The reacted coating precursors contact and deposit the coating on the surface of the substrate in the deposition zone. A curtain of flowing inert gases may be provided around the reaction zone to shield the reactive coating materials/plasma in that zone from contamination with the materials used in the surrounding apparatus or with the components of the ambient atmosphere.

The vaporization of the liquid media and reaction of the coating precursors in the reaction zone requires an input of energy. Depending on the reactivity of the coating material and the substrate, the required energy can be provided from various sources, such as combustion, electrical resistance heating, induction heating, microwave heating, RF heating, hot surface heating, laser heating and/or mixing with a remotely heated gas.

The (CACCVD) technique provides a relatively high rate of energy input, enabling high rates of coating deposition. In some preferred cases, the fluid media and/or a secondary gas used to atomize the fluid media can be a combustible fuel which also serves as an energy source.

Particularly important is the capability of CACCVD to form high quality adherent thin film deposits at or about atmospheric pressure, thereby avoiding the need for elaborate vacuum or similar isolation housings. For these reasons, in many cases, CACCVD thin film coatings can be applied in situ, or "in the field", where the substrate is located. Combustion chemical vapor deposition (CCVD) is not suitable for those coating applications wherein the coating, and/or the substrate, require an oxygen free environment. For such applications, embodiments of the CACCVD process employing non-combustion energy sources such as hot gases, heated tubes, radiant energy, microwave and energized photons, as with infrared or laser sources, are suitable. In these applications it is important that all of the liquids and gases provided to the reaction and deposition zones be oxygen-free. The coating precursors can be fed in solution or suspension in liquids. Liquid ammonia and propane are suitable for the deposit of nitrides or carbides, respectively. The use of these non-combustion energy sources in a controlled atmosphere chemical vapor deposition system which forms deposits at or above atmospheric pressure is a particularly advantageous feature of CACCVD. The use of the non-combustion energy sources in a CVD system which provides enhanced atomization by the rapid release through a nozzle, or similar restriction, of the liquid coating precursor from near critical temperature and pressure conditions is a further uniquely advantageous feature of CACCVD.

Because the CACCVD process and apparatus provide a controlled atmosphere zone which is capable of movement relative to the substrate, it enables the production of coatings on substrates which may be larger than the controlled atmosphere zone and, therefore, larger than could otherwise be processed by conventional vacuum chamber deposition techniques.

A further advantage of the CACCVD system is its ability to coat substrates without needing additional energy supplied to the substrate. Accordingly, this system allows substrates to be coated which previously could not withstand the temperatures to which substrates were subjected by most previous systems. For instance, nickel coatings can be provided on polyimide sheet substrates without causing deformation of the substrate. Previously, atmospheric pressure deposition techniques were unable to provide chemical vapor deposition of metallic nickel because of its strong affinity to oxygen, while vacuum processing of polymeric sheet substrates, such as polyimide sheets, was problematical due to its causing of outgassing of water and organic materials, and such substrates tendency toward dimensional instability when subjected to heat and vacuum.

A Controlled Atmosphere Combustion Chemical Vapor Deposition (CACCVD) apparatus as described in above-referenced U.S. Patent Application No. 09/067,975 is illustrated in Figures 1 and 2. A coating precursor 10 is mixed with a liquid media 12 in a forming zone 14, comprising a mixing or holding tank 16. The precursor 10 and liquid media 12 are formed into a flowing stream which is pressurized by pump 18, filtered by filter 20 and fed through conduit 22 to an atomization zone 24, from which it flows successively through reaction zone 26, deposition zone 28 and barrier zone 30. The reaction zone 26 and deposition zone 28 are both included in a controlled atmosphere zone.

The flowing stream is atomized as it passes into the atomization zone 24. Atomization can be accomplished by recognized techniques for atomizing a flowing liquid stream. In the illustrated apparatus, atomization is effected by discharging a high velocity atomizing gas stream surrounding and directly adjacent the flowing stream as it discharges from conduit 22. The atomizing gas stream is provided from a gas cylinder or other source of high pressure gas. In the illustrated embodiment, high pressure hydrogen (H₂) is used both as an atomizing gas and as a fuel. The atomizing gas is fed from hydrogen gas cylinder 32, through regulating valve 34 and fiowmeter 36 into conduit 38. Conduit 38 extends concentrically with conduit 22 to the atomization zone where both conduits end allowing the high- velocity hydrogen atomizing gas to contact the flowing liquid stream, thereby causing it to atomize into a stream of fine particles suspended in the surrounding gas/vapors. This stream flows into the reaction zone 26 wherein the liquid media vaporizes and the coating precursor reacts to form a reacted coating precursor, which can involve dissociation of the coating precursor into ions of its components resulting in a flowing stream of ionic particles, or plasma. The flowing stream is then directed to contact the substrate 40 thereby depositing the coating thereon in the deposition zone 28.

The flowing stream may be atomized by injecting the atomizing gas stream directly at the stream of liquid media/coating precursor as it exits conduit 22. Alternatively, atomization can be accomplished by directing ultrasonic or similar energy at the liquid stream as it exits conduit 22. A further preferred atomization technique which involves feeding the liquid media/coating precursor at a temperature within 50 °C of its critical temperature and a pressure above its liquidus or critical pressure to a restriction, such as through a hollow needle with a restricted outlet or a nozzle, from which it discharges into a lower pressure zone is described in the above- referenced patent application, Serial No. 08/691,853. The rapid pressure release of the highly energetic liquid media/coating precursor results in its fine atomization and vaporization.

The vaporization of the liquid media and reaction of the coating precursor require substantial energy input to the flowing stream before it leaves the reaction zone. This energy input can occur as it passes through the conduit 22, and/ or in the atomization and reaction zones. The energy input can be accomplished by a variety of known heating techniques, such as fuel combustion, electrical resistance heating, microwave or RF heating, induction heating, radiant heating, mixing the flowing stream with a remotely heated liquid or gas, photonic heating such as with a laser, heat exchange through a hot surface, etc. In the illustrated preferred embodiment, the energy input is accomplished by the combustion of a fuel and an oxidizer in direct contact with the flowing stream as it passes through the reaction zone. This relatively new technique, referred to as Combustion Chemical Vapor Deposition (CCVD), is more fully described in above-referenced U.S. Patent No. 5,652,021. In the illustrated embodiment, the fuel, hydrogen, is fed from hydrogen gas cylinder 32, through a regulating valve, fiowmeter 42 and into conduit

44. The oxidizer, oxygen, is fed from oxygen gas cylinder 46, through regulating valve 48 and fiowmeter 50 to conduit 52. Conduit 52 extends about and concentric with conduit 44, which extends with and concentrically about conduits 22 and 38. Upon exiting their respective conduits, the hydrogen and oxygen combust creating combustion products which mix with the atomized liquid media and coating precursor in the reaction zone 26, thereby heating and causing vaporization of the liquid media and reaction of the coating precursor.

A curtain of a flowing inert gas provided around at least the initial portion of the reaction zone isolates the reactive gases from the materials present in the apparatus located in proximity to the reaction zone. An inert gas, such as argon, is fed from inert gas cylinder 54, through regulating valve 56 and fiowmeter 58 to conduit 60. Conduit 60 extends about and concentric with conduit 52. Conduit 60 extends beyond the end of the other conduits 22, 38, 44 and 52, extending close to the substrate whereby it functions with the substrate 40 to define a deposition zone 28 where coating 62 is deposited on the substrate generally in the shape of the cross-section of conduit 60. As the inert gas flows past the end of oxygen conduit 52, it initially forms a flowing curtain which extends about the reaction zone, shielding the reactive components therein from conduit 60. As it progresses down the conduit 60, the inert gas mixes with the gases/plasma from the reaction zone and becomes part of the flowing stream directed to the deposition zone 28.

An ignition source is needed to initially ignite the hydrogen and oxygen. A separate manually manipulated lighting or ignition device is sufficient for many appUcations, however the use of such may require a temporary reduction in the flow of inert gas until a stable flame front is established. In some applications, the total flow of gas may be too great to establish an unassisted stable flame front. It then is necessary to provide an ignition device capable of continuously or semi-continuously igniting the combustible gases as they enter the reaction zone. A pilot flame or a spark producing device are exemplary igmtion sources which may be employed. In the deposition zone 28, the reacted coating precursor deposits coating 62 on the substrate 40. The remainder of the flowing stream flows from the deposition zone through a barrier zone 30 to discharge into the surrounding, or ambient, atmosphere. The barrier zone 30 functions to prevent contamination of a controlled atmosphere zone by components of the ambient atmosphere. The controlled atmosphere zone includes the reaction zone, the deposition zone and any additional space through which the flowing stream may have access after passing from the deposition zone 28 and prior to passing through the barrier zone 30. The high velocity of the flowing stream as it passes through the barrier zone 30 is a characteristic feature of this zone. By requiring that the flowing stream achieve a velocity of at least fifty feet per minute as it passes through the barrier zone, the possibility of contamination of the controlled atmosphere zone by components of the ambient atmosphere is substantially eliminated in most coating applications. By requiring that the flowing stream achieve a velocity of at least one hundred feet per minute the possibility of ambient atmosphere contamination of the controlled atmosphere zone is essentially eliminated in those coating operations which are more highly contamination sensitive, such as in the production of nitride or carbide coatings. In the apparatus of Figure 1, a collar 64 is attached to and extends perpendicularly outward from the end of conduit 60 adjacent deposition zone 28. The barrier zone 30 is defined by the clearance provided between the collar 64 and the substrate 40. The collar is shaped to provide a conforming surface 66 capable of being deployed close to the surface of the substrate whereby a relatively small clearance is provided for the exhaust of gases passing from the deposition zone to the ambient atmosphere. The clearance established between the conforming surface 64 of the collar and the substrate is sufficiently small that the exhaust gases achieve the velocity required in the barrier zone for at least a portion of their passage between the collar and the substrate. To this end, the conforming surface 64 of the collar 62 is shaped to lie essentially parallel to the surface of the substrate 40. When the surface of the substrate 40 is essentially planar, as it is in the illustrated embodiment, the conforming surface of the substrate is also substantially planar. Edge effects, such as elevated temperatures and residual reactive components, which occur adjacent the end of the conduit 60 can extend the deposition zone beyond the area of the substrate located directly in front of the end of conduit 60. The collar 64 should extend outward from its joinder to the conduit 60 a sufficient distance to preclude the back-mixing of ambient gases into the deposition zone due to a possible Venturi effect, and to assure that the entire area of the deposition zone, as it is extended by the previously noted edge effects, is protected from the backflow of ambient gases by the "wind" of high velocity exhaust gases sweeping through the area between the collar and the substrate. The extended collar assures that contamination is prevented throughout the controlled atmosphere zone including the entire extended deposition zone. The diameter of the collar should be at least twice the internal diameter of conduit 60, and preferably, should be at least five times the internal diameter of conduit 60. The internal diameter of conduit 60 typically is in the range of 10 to 30 millimeters, and preferably is between 12 and 20 millimeters.

In operation, the collar 64 is located substantially parallel to the surface of the substrate 40 and at a distance therefrom of 1 centimeter or less. Preferably, the facing surfaces of the collar and the substrate are between 2 and 5 millimeters apart. Spacing devices, such as three fixed or adjustable pins (not shown), may be provided on the collar to assist in maintaining the proper distance between the collar and the substrate.

The apparatus illustrated in Figure 1 is particularly advantageous for applying coatings to substrates which are too large, or for which it is not convenient, to be treated in a specially controlled environment such as a vacuum chamber or a clean room. The illustrated coating technique is advantageous because (a) it can be applied to substrates which are larger than its controlled atmosphere zone, and (b) because it can be accomplished under atmospheric pressure conditions and at more convenient "in the field" locations. The series of concentric conduits 22, 38, 44, 52 and 60 form a coating head 68 which can be supplied by relatively small flexible tubes and can be sufficiently small to be portable. Adding energy to the coating precursor by combustion of a fuel or by providing heat generated by electrical resistance are compatible with a relatively small, portable coating head. Large substrates can be coated either by having the coating head traverse the substrate repeatedly in a raster or similar predetermined pattern, or by traversing the substrate with an array of coating heads arranged to cumulatively provide a uniform coating, or by rastering an array of coating heads. In addition to permitting the thin film coating of articles which previously were too large to be coated, this technique permits the coating of larger units of those substrates which previously were coated under vacuum conditions. Manufacturing economies can be achieved by coating larger units of these substrates, especially when mass production of the substrates is involved.

The apparatus illustrated in Figures 1 and 2 is also particularly suitable for the production of coatings which are oxidation sensitive, such as most metal coatings. To provide such coatings the fuel is fed through conduit 44 in proximity to the atomized liquid media and coating precursor, while the oxidizer is fed through conduit 52. The atomizing gas fed through conduit 38 and/or the liquid media fed through conduit 22 can be materials having fuel value, they can be materials which react with the coating precursor or they can be inert materials. When the produced coatings or coating precursor materials are oxygen sensitive, a reducing atmosphere is maintained in the reaction and deposition zones by assuring that the total amount of oxidizer fed is restricted to an amount less than that required to fully combust the fuel provided to the reaction zone, i.e. less than a stoichiometric amount of oxidizer is provided. Generally, the fuel excess is limited so as to limit any flame zone which develops when the residual hot gases eventually mix with atmospheric oxygen. When the produced coatings and the precursor materials are oxygen tolerant or enhanced by the presence of oxygen, such as in the production of most of the oxide coatings, an oxidizing or neutral atmosphere may be provided in the reaction and deposition zones by feeding a stoichiometric or excess amount of oxidizer. Further, with oxygen tolerant reagents and products, the oxidizer can be fed through the inner conduit 44 while fuel is fed through outer conduit 52.

The inert gas supplied through conduit 60 must be sufficient to shield the inside surface of the conduit from the reactive gases produced in the reaction zone, and it must be sufficient, when added with the other gases exiting the deposition zone, to provide the gas velocity required in the barrier zone.

The energy input can be accomplished by mechanisms other than the combustion method illustrated in Figures 1 and 2. For instance, it could be accomplished by mixing the liquid media coating precursor with a preheated fluid, such as an inert gas preheated to a temperature in excess of 200°C. It should be apparent that not all of the conduits 22, 38, 44, 52 and 60 are required when the energy input is accomplished by methods other than combustion. Usually one or both of conduits 44 and 52 are omitted when the energy input is provided by one of the non- combustion techniques.

The porosity or density of the deposited coating can be modified by varying the distance between the flame and the deposition zone at the substrate's surface. Shortening of this distance provides an increased coating density, while increasing the distance provides a more porous coating. In the illustrated CACCVD technique the reaction zone is generally coextensive with the flame produced by the burning fuel. Of course, the flame zone and the substrate must be maintained sufficiently far apart that the substrate is not damaged by the higher temperatures which would result when the flame zone more closely approaches the substrate surface. While substrate temperature sensitivity varies from one substrate material to the next, the temperature in the deposition zone at the substrate surface, typically, is at least 600 °C cooler than the maximum flame temperature.

When some of the non-combustion methods are used to supply the energy input, the maximum temperatures present in the reaction zone are substantially lower than those present when a fuel is combusted in the reaction zone. In such cases, such as when the principal energy input is a preheated fluid which is mixed with the flowing stream in, or before it reaches, the reaction zone, the coating properties can be adjusted by varying the distance between the reaction zone and the substrate surface with less concern for overheating the substrate. In some cases the denser coating resulting from minimizing the distance between the reaction zone and the substrate makes it desirable to provide the reaction zone directly adjacent the substrate. Accordingly, the terms reaction zone and deposition zone are useful in defining functional regions of the apparatus, but are not intended to define mutually exclusive regions, i.e. in some applications reaction of the coating precursor may occur in the deposition zone at the substrate surface.

The energy input to the flowing stream prior to its leaving the reaction zone generally negates the need to provide energy to the deposition zone by heating the substrate, as is often required in other coating techniques. In the present deposition system, the substrate generally acts as a heat sink cooling the gases present in the deposition zone, rather than heating them. Accordingly, the temperatures to which the substrates are subjected are substantially less than are encountered in systems which require that energy be transmitted to the deposition zone through the substrate. Therefore, the CACCVD coating process can be applied to many temperature sensitive substrate materials which previously could not be coated by those techniques which involved transferring heat to the deposition zone through the substrate. Moreover, the controlled atmosphere zone extending over that portion of the substrate which is at an elevated temperature protects the substrate to the same extent it protects the coating material, thereby enabling the coating of contamination sensitive substrates, such as oxidation sensitive substrates.

The fluid media can be a combustible liquid organic solvent or gas such as an alkane, an alkene or an alcohol, or it can be an oxidant or exothermic material, such as nitrous oxide (N₂O), or it can comprise noncombustible or difficultly combustible materials such as water, carbon dioxide or ammonia. The precursor material for depositing the metal layer is an organic or a non-organic compound which is capable of reacting, including dissociation and ionizing reactions, to form a reaction product which is capable of depositing a coating on the substrate. Precursor materials which exothermically dissociate or otherwise exothermically react are particularly suitable since the exothermic energy evolved in the reaction zone decreases the energy input otherwise required. The coating precursor may be fed to the reaction zone as a liquid, a gas or, partially, as a finely divided solid. When fed as a gas, it may be entrained in a carrier gas. The carrier gas can be inert or it can also function as a fuel.

When the precursor for the metal layer is provided in a hquid media, as is preferred, up to 50% of the coating precursor material may be present as fine particles in the liquid media. However, it is preferred that the coating precursor material be fully dissolved in the liquid media. The concentration of coating precursor in the liquid media typically is less than 0.1 M, and preferably is between 0.0005 M and 0.05 M, which is relatively dilute compared to concentrations of coating precursor materials required in those coating techniques which feed the coating precursor to the coating operation in a gaseous or vapor state. Moreover, the metal layer precursor material does not need to have a relatively high vapor pressure as do precursor materials of other coating techniques which are required to be fed in a gaseous or vapor state. Precursors having vapor pressures of less than 10 torr at 300°C can be used. Accordingly, a relatively wide range of precursor materials may be used in this technique, many of which are substantially cheaper than the relatively volatile materials required by other coating techniques.

A wide range of precursors can be used as gas, vapor or solutions. It is preferred to use the lowest cost precursor which yields the desired morphology. Suitable chemical precursors, not meant to be limiting, for depositing various metals or metalloids are as follows:

Pt platinum-acetylacetonate [Pt(CH₃COCHCOCH₃)₂] (in toluene/methanol), platinum-(HFAC₂), diphenyl-(l,5-cyclooctadiene) Platinum (LI) [Pt(COD) in toluene- propane] platinum nitrate (in aqueous ammonium hydroxide solution)

Mg Magnesium naphthenate, magnesium 2-ethylhexanoate [Ma(OOCCH(C₂H₅)C₄H₉)₂], magnesium naphthenate, Mg-TMHD, Mg-acac, Mg-nitrate, Mg-2,4-pentadionate Si tetraethoxysilane [Si(OC₂H₅)₄], tetramethylsilane, disilicic acid, metasilicic acid P triethyl phosphate [C₂H₅O)₃PO₄], triethyllphosphite, triphenyl phosphite La lanthanum 2-ethylhexanoate [La(OOCCH(C₂H₅)C₄H₉)₃] lanthanum nitrate [La(NO₃)₃], La-acac, La-isopropoxide, tris (2,2,6,6-tetramethyl-3,5-heptanedionato), lanthanum [La(C_πH,₉O₂)₃] Cr chromium nifrate [Cr(NO₃)₃], chromium 2-ethylhexanoate

[Cr(OOCCH(C₂H₅)C₄H₉)₃], Cr-sulfate, chromium carbonyl, chromium(JJI) acetylacetonate

Ni nickel nitrate [Ni(NO₃)₂] (in aqueous ammonium hydroxide), Ni-acetylacetonate, Ni-2- ethylhexanoate, Ni-napthenol, Ni-dicarbonyl Al aluminum nitrate [Al(NO₃)₃], aluminum acetylacetonate [Al(CH₃COCHCOCH₃)₃], triethyl aluminum, Al-s-butoxide, Al-I-propoxide, Al-2-ethylhexanoate Pb Lead 2-ethylhexanoate [Pb(OOCCH(C₂H₅)C₄H₉)₂], lead naphthenate, Pb-TMHD,

Pb-nifrate Zr zirconium 2-ethylhexanoate [Zr(OOCCH(C₂H_s)C₄H₉)₄], zirconium n-butoxide, zirconium (HFAC₂), Zr-acetylacetonate, Zr-n-propanol, Zr-nitrate Ba barium 2-ethylhexanoate [Ba(OOCCH(C₂H₅)C₄H₉)₂], Ba-nifrate, Ba-acetylacetonate, Ba-TMHD

Nb niobium ethoxide, tefrakis(2,2,6,6-teframethyl-3,5-heptanedionato) niobium Ti titanium (IV) I-propoxide [Ti(OCH(CH₃)₂)₄], titanium (IV) acetylacetonate, titanium-di-I-propoxide-bis-acetylacetonate, Ti-n-butoxide,

Ti-2-ethylhexanoate, Ti-oxide bis(acetylacetonate) Y yttrium 2-ethylhexanoate [Y(OOCCH(C₂H₅)C₄H₉)₃], Y-nitrate, Y-I-propoxide,

Y-napthenoate Sr strontium nitrate [Sr(NO₃)₂], strontium 2-ethylhexanoate, Sr(TMHD) Co cobalt naphthenate, Co-carbonyl, Co-nitrate, Au chlorotriethylphosphine gold (I), chlorotriphenylphosphine gold(I) B trimethylborate, B-trimethoxyboroxine

K potassium ethoxide, potassium t-butoxide, potassium 2,2,6,6-tetramethylheptane-3 ,5-dionate Na sodium 2,2,6,6-tetramethylheptane-3,5-dionate, sodium ethoxide, sodium t-butoxide Li lithium 2,2,6,6-tetramethylheptane-3,5-dionate, lithium ethoxide lithium-t-butoxide Cu Cu(2-ethylhexonate)₂, Cu-nitrate, Cu-acetylacetonate Pd paladium nitrate (in aqueous ammonium hydroxide solution) (NH₄)₂Pd(NO₂)₂,

Pd-acetylacetonate, ammonium hexochloropalladium Ir H₂IrCl₆ (in 50% ethanol in water solution), Ir-acetylacetonate, Ir-carbonyl

Ag silver nitrate (in water), silver nitrate, silver fluoroacetic acid, silver acetate

Ag-cy clohexanebutyrate , Ag-2-ethylhexanoate Cd cadmium nitrate (in water), Cd-2-ethylhexanoate Nb niobium (2-ethylhexanoate) Mo (NH₄)₆Mo₇O₂₄, Mo(CO)₆, Mo-dioxide bis (acetylacetonate) Fe Fe(NO₃)₃9H₂O, Fe-acetylacetonate

Sn SnCl₂2H₂O, Sn-2-ethylhexanoate, Sn-tetra-n-butyltin, Sn-tetramethyl

In In(NO₃)₃ xH₂O, In-acetylacetonate

Bi Bismuth nitrate, Bismuth 2-ethyl hexonate Ru Ru-acetylacetonate

Zn Zn-2-ethyl hexonate, Zn nitrate, Zn acetate

W W-hexacarbonyl, W-hexafluoride, tungstic acid

Ce Ce-2-ethyl hexonate

Although many of the metals and metalloids listed above would not be suitable for forming electrically conductive layers, certain elements might conceivably be co-deposited in minor proportions with the primary metal to affect electrical, mechanical or adhesion properties. Precursors of two or more metals may be admixed to deposit alloys.

In accordance with the present invention, as shown in Figure 3, a thin, electrically conductive, non-porous, continuous, and uniform metal layer 110 is deposited on a fransfer substrate 112 to form a fransfer laminate 114. A primary requirement of the transfer substrate 112 is that its adhesion to the metal layer 110 is sufficiently low that when the metal layer is bound to a resin having greater adhesion to the metal than the transfer substrate 112, the substrate 112 can be pealed away. The adhesion of the substrate 112 to the metal layer is preferably between about Vi lb / in² and about 2 lbs/in². The preferred substrate 112 for deposition of a copper layer 110 in accordance with the invention is aluminum foil. Adhesion of a copper layer 110 to an aluminum foil subsfrate 112 is measured at 1 to 1.2 lbs/in². In addition, the subsfrate must have sufficient temperature stability to withstand the coating conditions, particularly temperature. The fransfer subsfrate 112 is generally a film or foil which, along with the deposited metal layer, may be reeled for shipping and storage, but the transfer subsfrate 112 must have sufficient rigidity to support the metal layer thereon prior to adherence to the resin. A typical aluminum foil used as a transfer substrate 112 is about 50 microns thick.

A metal layer 110 can be deposited on the transfer subsfrate 112 by CCVD or CACCVD to any desired thickness, however, the metal layers in accordance with the invention are deposited to between about 0.1 and about 3 microns, preferably between about 0.5 and about 2 microns. The metal layers are typically applied at rates between 0.1 and 500 milligrams/minute per coating head, preferably at rates between 0.5 and 2.0 milhgrams/minute per coating head.

In CACCVD the substrate temperature is generally maintained below 600 °C, preferably, it is maintained below 400 °C and, when required to avoid deleterious effects on the subsfrate or other components, the subsfrate can be maintained below 200°C. When coating the more temperature sensitive substrates, those embodiments of the invention which employ non-combustion energy input sources, such as heated fluids, radiant or microwave energy, are preferred. The substrate may be cooled by directing a flow of an inert cooling fluid, preferably a gas, at a surface which is remote from the deposition zone, such as the surface of the substrate which is opposite the surface exposed to the deposition zone. The inventive process is also particularly suited for coating substrates which, when heated, are capable of unwanted reactions with components in the atmosphere, such as substrates susceptible to oxidation. The lower temperatures to which the substrates are subjected and the controlled atmosphere surrounding the deposition zone both contribute to minimizing unwanted reactions of the substrate with atmospheric components.

While it is generally preferred to conduct a CACCVD coating procedure at essentially ambient, or atmospheric, pressure; it may at times be useful to control combustion flame temperatures or other parameters by controlling the combustion pressure. The combustion flame can be maintained at pressures as low as 10 torr. Generally, especially when energy sources other than a combustion flame are utilized, the greatest cost and production benefit is achieved by operating at ambient and higher pressures.

Illustrated in Figure 4 are two transfer laminates 114 being adhered to an un-cured or partially cured dielectric resin material 116 for forming a two-sided circuit board blank structure. The dielectric material may be selected from a variety of materials such as free standing epoxies, FR epoxies, prepregs, polyimides, cyanate esters, or liquid crystal polymers, via traditional lamination processes. In a typical lamination process, the transfer laminates 114 are held in contact with the dielectric material under heat and pressure until the dielectric resin material fully cures, a firm bond thereby being formed between the metal layer 110 and the dielectric resin material 116. It is necessary that adhesion between the dielectric resin material 116 and the metal layer 110 be established greater than the adhesion between the metal layer 110 and the deposition subsfrate 112. The adhesion between the transfer substrate 112 and the metal layer is typically between about Vi lbs/in² and about 2 lbs/in²-, generally less than about 1.5 lbs/in²

Preferably the adhesion between the metal layer 110 and the resin material 116 is greater than about 5 lbs/in², preferably greater than about 9 lbs/in². In relative terms, the adhesion between the resin material 116 and the metal layer 110 should be at least about 3 lbs/in², preferably at least about 6 lbs/in² above that of the adhesion between the metal layer 110 and the fransfer subsfrate 112. This allows the transfer substrates 112 to be peeled from the metal layers 110 as seen in Figure 5.

The adhesion between the metal layer 110 and resin material 116 depends not only on the composition of the two materials but on the surface smoothness or roughness of the metal layer (on the surface opposite the fransfer subsfrate 112). In depositions by CCVD or CACCVD, metal layers can be deposited to have surfaces ranging from smooth to quite rough; thus, a desired surface roughness for good adhesion to the resin material 116 can be easily achieved by varying deposition parameters. Such deposition parameters which may be varied include temperature, carrier hquid, precursor compounds, precursor concentrations, flow rate, etc. Because a wide variety of materials may be deposited by CCVD or CACCVD, specific conditions for achieving a desired surface roughness must be empirically determined; however, this is easily within the skill of one with ordinary skill in the art to vary deposition parameters and determine when desired surface roughness is achieved. The ability to produce a transfer laminate of controlled surface roughness is an advantage of the present invention relative to other methods of forming transfer laminates, such as those described in U.S. Patents Nos. 3,969,199, 4,431,710, 4,357,395, 5,322,975, and 5,418,002.

Processing of the metal layers to form a printed circuit board is in a conventional manner, such as by "pattern plating" or "print and etch" as described above. Illustrated in Figures 6 A-E is a method of forming a thin film resistor by the transfer method of the present invention. On a support 201, e.g., aluminum, is deposited by CCVD or CACCVD a conductive material layer 202, e.g., copper, and deposited by CCVD a resistive material layer 203, e.g., silica-doped platinum, as described in above-referenced U.S. Patent Application No. 09/198,954 to provide the structure of Figure 6A. The resistive material layer is generally between about 0.1 and about 0.75 micron thick, preferably between about 0.1 and about 0.2 micron thick.

As described in referenced Patent Application 09/198,954, silica-doped platinum is porous and can be patterned by an ablative etching technique. The silica-doped platinum is covered with a photoresist which is exposed to patterned radiation and developed. Then the silica-doped platinum is exposed to an etchant for copper. The etchant seeps through the silica-doped platinum layer and degrades the interface between the copper layer 202 and the silica-doped platinum layer 203. Etching is stopped before the copper layer 203 is significantly degraded. This produces resistive material patch 204, Figure 6B. Although only one such patch is illustrated, a plurality of resistive material patches will be produced.

As seen in Figure 6C, the resistive material patch 204 is embedded in uncured dielectric material, such as fiberglass/epoxy "prepreg" 205, and the prepreg is cured. The hardened prepreg provides support for the laminate during subsequent processing. The aluminum foil support 201 is seen in Figure 6C being peeled away from the copper layer 202. Next, the copper layer 202 is covered with a photoresist pattern 206 (Figure 6D) and copper electrical connects 207 are electroplated thereon. The resist is stripped (Figure 6E). Next, the copper layer 202 is removed by rapid etching, e.g., with ferric chloride, leaving the electrical connects 207 at opposite ends of resistive material patch 204. Typically, this structure would be embedded in an additional layer of prepreg (not shown). A similar method is used for forming capacitors as illustrated in Figures 7 A-E. Shown in

Figure 7 A is an aluminum support 301 on which are successively deposited a copper layer 302, a sihca layer, and another copper layer 304. The dielectric (silica) layer is typically between about 0.1 and about 0.75 micron thick, preferably between about 0.1 and about 0.25 micron thick. On copper layer 304 is formed a patterned photoresist pattern 305 Figure 7B, and copper capacitor plates 306 (two illustrated) are electrodeposited on the copper layer 304 in portions not covered with the photoresist pattern 305. The photoresist 305 is stripped producing the structure of Figure 7C, and the copper layer 304 is removed by rapid etch, leaving discrete capacitor plates

306 in contact with dielectric layer 303 as seen in Figure 7D. The capacitor plates 306 are embedded in prepreg 307, and when the prepreg cures, the copper foil 301 is peeled away. The circuitization process of copper layer 304 is repeated with copper layer 302, producing capacitor plates 306 on the other side of the dielectric layer 303. This side is also embedded in prepreg 307.

The invention will now be described in greater detail by way of specific examples.

Example 1 - Nickel coating on a polyimide subsfrate

Nickel films have been deposited on polyimide substrates in the apparatus illustrated in Figure 1. A solution of 0.0688 M Ni(NO₃)₂ in 1.20 M NH₄OH was fed through a 75 μ ID fused silica capillary (22) at a 0.25 seem (standard cubic centimeter/minute) flow rate. Hydrogen was fed through atomizing conduit (38) at 1.20 1pm (standard liters/minute) and through conduit (44) at 756 seem. Oxygen as fed through conduit (52) at 1.40 1pm. Argon was fed at 28.1 1pm through conduit (68), which had an interior diameter of 5/8 inch. The argon flow was reduced to permit manual ignition of the flame, following which it was returned to its initial setting. Once lit, no pilot or other ignition source was required to maintain ignition. The gas temperature approximately 1 mm above the deposition point was 600 °C. The subsfrate was rastered 2mm from the nozzle collar (64) at 20 inch/minute with 0.0625 inch steppings traversing an area of 4" by 4" twice, once with horizontal sweeps followed by once with vertical sweeps. The total time required for the rastering motion was 16 minutes. Nickel was deposited at an average thickness of approximately 0.1 micron. Example 2- Copper coating on aluminum foil

Copper was deposited from a 0.0350 M solution of copper(π)bz^'s(2-ethylhexanoate) in anhydrous ethyl ether. The solution was sprayed, at 1.00 seem, into a tube which was also fed with 40 1pm of a preheated 500°C 10% H₂/Ar gas mixture. The injection was approximately 5 cm from the tube exit. The substrate was located normal to the gas flow approximately 2 mm from the tube exit. A 1.5 micron metallic copper coatings were deposited on a 50 micron aluminum foil by this method.

Example 3- Platinum coating on polyimide substrate A platinum film has been deposited on polyimide in the apparatus shown in Figure 1. A

5.3 mM (NH₃)₂Pt(NO₂)₂ solution in 1.20 M NH₄OH was fed through capillary (22) at 0.25 seem.

Argon was fed through conduit (18) at 1.60 1pm. Hydrogen was fed through conduit (44) at 1.6 lpm. Oxygen was fed through conduit (52) at 800 seem. Argon was fed through conduit (68) at

28.1 lpm. The gas temperature approximately 1 mm above the deposition point was 400 °C. The substrate was rastered 2mm from the nozzle collar (64) over an area of 6" by 6" three times, twice with horizontal sweeps followed by once with vertical sweeps. A 3 micron platinum coating was produced

Example 4- Nickel coating on polyimide substrates Nickel films have been deposited on polyimide substrates in the Figure 1 apparatus. A solution of 2.00 g. Ni(NO₃)₂»6H₂O in 25.0 g. H₂O and 180 g. NH_3(L) was fed from a 300 cc pressurized container through a 22 ga. stainless steel needle with a 20 μm ID fused silica capillary insert at the tip, at 0.25 seem. Hydrogen was passed through conduits (38) and (44) at flow rates of 1.20 lpm and 756 seem respectively. Oxygen was fed through conduit (52) at 1.20 lpm. Argon was fed through conduit (68) at 28.1 lpm. The gas temperature approximately 1 mm above the deposition point was 600 °C. The subsfrate was rastered over an area of 4" by 4" twice at a distance of approximately 2 mm from the nozzle collar (64) for 16 minutes. A nickel coating having an average thickness of 0.1 micron was deposited.

Claims

What is Claimed is:

1. A method for producing a blank for a printed circuit board having a dielectric material substrate and a metal layer between about 0.1 and about 3 microns thick on at least one side of said subsfrate, the method comprising providing a transfer subsfrate which exhibits relatively low adhesion to a metal layer to be deposited thereon, depositing by combustion chemical vapor deposition or controlled atmosphere combustion chemical vapor deposition a metal layer to a thickness of between about 0.1 and about 3 microns on said transfer substrate, providing a dielectric material subsfrate and adhering said deposited metal layer to said dielectric material subsfrate to establish adhesion that is high relative to the adhesion between said deposition subsfrate and said metal layer, and removing said fransfer substrate from said metal layer.

2. The method according to Claim 1 wherein deposited metal layers are adhered to both sides of said dielectric material subsfrate.

3. The method according to Claim 1 wherein said metal layer is deposited so as to have an as/deposited surface roughness on the side opposite said subsfrate, which roughness is sufficient to enhance adhesion to said dielectric material subsfrate.

4 The method according to Claim 1 wherein the adhesion established between rough surface of said deposited metal layer and said dielectric material subsfrate is at least about 5 lbs/in².

5. The method according to Claim 1 wherein said deposited metal is copper.

6. The method according to Claim 1 wherein said deposited metal is nickel.

7. The method according to Claim 1 wherein said deposited metal is platinum.

8. The method according to Claim 1 wherein said deposited metal is selected from the group consisting of silver, gold, tin, and zinc.

9. The method according to Claim 1 wherein said transfer substrate is aluminum foil.

10. The method according to Claim 1 wherein said deposition substrate is a polyimide film.

11. The method according to Claim 1 wherein the adhesion between said deposited metal layer and said transfer substrate is about 1.5 lbs/in² or less.

12. The method according to Claim 1 wherein the adhesion established between said deposited metal layer and said dielectric material substrate is at least about 5 lbs/in².

13. The method according to Claim 1 wherein the adhesion established between said deposited metal layer and said dielectric material substrate is at least about 3 lbs/in² greater than the adhesion between said fransfer substrate and said deposited metal layer.

14. A transfer laminate for providing a thin metal layer to a dielectric subsfrate, said fransfer laminate comprising a flexible transfer subsfrate and a metal layer between about 0.1 and about 3 microns thick releasably adhered to said flexible transfer subsfrate 1 layer between about 0.1 and about 3 microns thick releasably adhered to said flexible fransfer subsfrate, said metal layer having an as-deposited surface roughness on the side opposite said dielectric substrate sufficient to promote subsequent adhesion to a dielectric substrate..

15. The transfer laminate of Claim 14 wherein said metal layer is copper.

16. The fransfer laminate of Claim 14 wherein said transfer substrate is aluminum foil.

17. The transfer laminate of Claim 14 wherein the adhesion between said transfer subsfrate and said metal layer is between about ^lA and about 2 lb/in².

18. A fransfer laminate for providing a thin metal layer to a dielectric substrate, said transfer laminate comprising a flexible transfer subsfrate, a metal layer between about 0.1 and about 3 microns thick releasably adhered to said flexible transfer subsfrate 1 layer between about 0.1 and about 3 microns thick releasably adhered to said flexible fransfer substrate, and a layer of dielectric material between about 0.1 and about 0.75 micron thick adhered to said metal layer.

19. A fransfer laminate for providing a thin metal layer to a dielectric subsfrate, said transfer laminate comprising a flexible fransfer substrate, a metal layer between about 0.1 and about 3 microns thick releasably adhered to said flexible fransfer substrate 1 layer between about 0.1 and about 3 microns thick releasably adhered to said flexible fransfer substrate, and a layer of resistive material between about 0.1 and about 0.75 micron thick adhered to said metal layer.

20. A method for forming a thin film resistor, the method comprising: depositing on a support substrate an electrically conductive layer in a manner such that said conductive layer has sufficiently weak adherence to said subsfrate that said support subsfrate may be peeled from said conductive layer, depositing on said conductive layer an electrically resistive material layer, patterning said resistive material layer to provide at least one resistive material layer patch, embedding said resistive material patch in laminate-supporting dielectric material, peeling said support subsfrate from said conductive layer, and from said conductive layer, forming electrical contacts at opposed locations on said resistive material patch and removing portions of said conductive layer over said resistive material patch so as to define an electrically conductive patch between said electrical contacts through said resistive material patch.

21. A method for forming a thin film capacitor, the method comprising: depositing on a support substrate a first electrically conductive layer in a manner such that said first conductive layer has sufficiently weak adherence to said substrate that said support subsfrate may be peeled from said first conductive layer, depositing on said conductive layer a dielectric material layer, depositing on said dielectric material layer a second electrically conductive layer, from said second electrically conductive layer, forming at least one capacitor plate, embedding said capacitor plate(s) formed from said second conductive layer in laminate-supporting dielectric material, peeling said support subsfrate from said first conductive layer, and from said first electrically conductive layer, forming at least one capacitor plate.