JP2004512698A - Use of metallization on copper foil for fine line formation instead of oxidation process in printed circuit board manufacturing - Google Patents

Abstract

The present invention provides a technique for manufacturing a printed circuit board with improved etching uniformity and resolution.
The method eliminates the need for a blackening process to improve adhesion and improves the ability to optically inspect printed circuit boards. The method includes: a) depositing a first surface of a conductive layer having a roughened second surface opposite the first surface on a substrate; b) providing a different etch resistance than the conductive layer. Depositing a thin metal layer comprising a material having on the roughened second surface of the conductive layer by performing steps (a) and (b) in any order. Thereafter, a photoresist is deposited over the metal layer and the photoresist is imagewise exposed and developed, thereby exposing the underlying metal layer portions. The exposed underlying metal layer portion is removed, thereby exposing the underlying conductive layer portion, and the exposed underlying conductive layer portion is removed, thereby producing a printed circuit layer.

Description

【００４４】
本発明を、その好ましい実施形態に関して具体的に示し、記述したが、本発明の精神および範囲を逸脱することなく、様々な変更および修正を加えることができることを、当業者なら容易に理解するであろう。特許請求の範囲は、開示した実施形態、上記で考察したその代替物、およびそのすべての均等物を包含すると解釈されるものである。[0001]
BACKGROUND OF THE INVENTION
Field of the invention
The present invention relates to the manufacture of printed circuit boards with improved etch uniformity and resolution. The method of the present invention eliminates the need for blackening to improve adhesion and improves the ability to optically inspect printed circuit boards.
[0002]
[Description of Related Technology]
Printed circuit boards are widely used in the electronics field. Printed circuit boards are useful for large-scale applications such as missiles, industrial controllers, and small-scale devices such as telephones, radios, and personal computers. In particular, when utilizing printed circuits, it is important to achieve high precision and high resolution to minimize line and space widths (less than about 100 microns) to ensure good circuit performance.
[0003]
The ability to produce precise features of very small dimensions, on the order of 100 microns or less, is crucial for manufacturing small and large devices. The accuracy of the etching process becomes increasingly important as circuit patterns become smaller. It is well known in the art to produce small-shaped printed circuit boards with high accuracy using known photolithographic techniques. Generally, a conductive foil is deposited on a substrate, and then a photoresist is deposited on the conductive foil. Next, the photoresist is exposed and developed according to an image, and is later etched into a conductive foil to form a fine line and space pattern.
[0004]
Conventionally, the rough surface of the foil is rougher than the glossy surface of the foil, and the rough surface of the foil is bonded to the substrate for the main reason that it adheres well to the substrate. However, when the foil is attached to the substrate with the glossy surface down, the copper particles near the rough surface are oriented vertically in an extended state, and the occurrence of side etching, that is, horizontal etching, is reduced. It has been found that much more accurate etching can be performed. In addition, the need for over-etching to remove tooth structures and processes from the substrate is reduced, resulting in improved etch uniformity.
[0005]
When attaching the glossy surface of the foil to the substrate, it is necessary to roughen the surface in order to impart sufficient adhesiveness. One way to do this is to form the nodules by plating on the shiny side of the copper foil. One example of this type of copper product is described in Hoosick Falls, N.W. Y. Oak-Mitsui Inc. Commercially available as MLS. Another method that has been used is to apply roughening layers, such as nodules, to both sides of the foil to form a "double treated" foil. With this method, excellent resist adhesion is obtained, and an oxidation process is not required. This method is not preferred by the industry because the exposed surface of the foil can damage the roughened layer during handling.
[0006]
A known alternative to roughening the glossy surface when the rough surface contacts the laminate is a chemical microetching of the copper foil (commercially available from MacDermid, Waterbury, Connecticut, USA or Shipley Ronel, Marborough, Mass., USA). Pre-roughened (using commercially available sodium persulfate or sulfuric acid / hydrogen peroxide) or by scrubbing with pumice (machines are commercially available from IS, Italy and Isioki, Japan) Is the way. The surface is later chemically treated to deposit a layer of black copper oxide (also commercially available from MacDermid and Shipley Ronel) so that another insulating substrate can be laminated onto the circuit. This series of chemical treatments is not desirable because it is complicated and causes a problem of waste treatment of the used chemicals. Therefore, there is no problem of processing the conductive foil twice during the processing of the multilayer circuit board, does not require a blackening process, and a process for etching circuit lines and circuit spaces with high resolution and high accuracy is known in the art. Needed in the field.
[0007]
Therefore, there is a continuing effort in the art to improve circuit board manufacturing techniques and improve shape accuracy. For example, US Pat. No. 5,240,807 teaches a photoresist article having a portable, conformable, built-on etch mask that is useful for enhancing image contrast and replicating microscopic parts. Please refer to. A portion of the conductor foil under the photoresist is selectively etched to form a circuit line pattern. U.S. Pat. No. 6,042,711 discloses another approach, in which a metal foil having a powdered dendritic deposit metal layer and a metal flash layer and having improved peel strength is disclosed. Provided. Furthermore, WO 00/03568 discloses a method for forming circuit lines on a substrate by applying a roughened conductive metal layer using a copper foil carrier.
[0008]
As yet another approach, U.S. Pat. No. 5,679,230 provides copper foil used in the manufacture of printed circuit boards. This copper foil can be used to make multilayer circuit boards without the need for conventional blackening treatments to improve adhesion.
[0009]
The present invention provides a solution to the problems of the prior art of depositing a thin metal layer on a conductive layer on a substrate. This metal layer acts as an etching mask during etching of the conductive layer, improving the accuracy and resolution of the etching. After etching, the thin metal layer remains on the conductive layer, obviating the need for an oxide layer.
[0010]
Moreover, the metal layer used in the method is extremely uniform and has a high reflectivity, so that the printed circuit formed is more compatible with automated optical inspection equipment than conventional printed circuits. Further, the metal layer used in the present invention has high mechanical strength and high resistance to mechanical damage such as surface scratches and scratches.
[0011]
Summary of the Invention
The invention relates to a) depositing a first surface of a conductive layer having a roughened second surface on the opposite side of the first surface onto a substrate; b) providing a different etching resistance than the conductive layer. Depositing a thin metal layer comprising a material having a roughened second surface of the conductive layer on the roughened second surface, performing steps (a) and (b) in any order; Depositing a photoresist on the layer; d) exposing and developing the photoresist image-wise, thereby exposing the underlying metal layer portions; e) removing the exposed underlying metal layer portions; Exposing the underlying conductive layer portion, and f) removing the exposed underlying conductive layer portion, thereby producing a printed circuit layer, thereby providing a method for manufacturing a printed circuit layer. I do.
[0012]
The invention relates to a) depositing a first surface of a conductive layer having a roughened second surface on the opposite side of the first surface onto a substrate; b) providing a different etching resistance than the conductive layer. Depositing a thin metal layer comprising the material having on the roughened second surface of the conductive layer, performing steps a) and b) in any order, and then c) on the metal layer D) exposing and developing the photoresist image-wise, thereby exposing the underlying metal layer portion; e) removing the exposed underlying metal layer portion, thereby removing the underlying metal layer portion; There is also provided a printed circuit layer manufactured by the method of exposing a portion of the conductive layer located at the bottom of the substrate and f) removing the exposed underlying portion of the conductive layer.
[0013]
[Detailed description of preferred embodiments]
The present invention generally provides a method for manufacturing printed circuit layers and printed circuit boards.
[0014]
The first step in practicing the method of the present invention is to deposit a layer of conductive material on a suitable substrate. Typical substrates are those suitable for processing into printed circuits or other microelectronic devices. Substrates suitable for the present invention are polymers reinforced with materials such as, but not limited to, glass fiber, aramid (Kevlar), aramid paper (Thermount), polybenzoxolate paper, or combinations thereof. Not done. Of these, glass fiber reinforced epoxy is the most preferred substrate. Gallium arsenide (GaAs), silicon, and crystalline silicon, polysilicon, amorphous silicon, epitaxial silicon, silicon dioxide (SiO ₂ Also suitable are semiconductor materials, such as silicon-containing compositions such as, for example, and mixtures thereof. The preferred thickness of the substrate is about 10 to about 200 microns, more preferably about 10 to about 50 microns.
[0015]
Preferably, the conductive layer comprises a material such as copper, zinc, brass, chromium, nickel, aluminum, stainless steel, iron, gold, silver, titanium, and combinations and alloys thereof. The most preferred conductive layer is a copper foil. The copper foil is preferably produced by electrodepositing copper from a solution onto a rotating metal drum. The copper foil surface adjacent to the drum is usually smooth, ie, a glossy surface, while the other surface is relatively rough, also known as a rough surface. The drum is usually made of stainless steel or titanium, which acts as a cathode, and receives copper as it precipitates from solution. The anode is generally composed of a lead alloy. A cell voltage of about 5 to 10 volts is applied between the anode and the cathode to deposit copper, but oxygen is simultaneously generated at the anode. Next, the copper foil is taken out of the drum, cut into a required size, and bonded on a substrate. The bonding is preferably performed by pressing at least about 175 ° C. for about 30 minutes. The press is preferably maintained at a pressure of about 150 psi (1.0 MPa) under a vacuum of at least 28 inches of mercury (71 cm).
[0016]
Preferably, but not necessarily, prior to lamination, the conductive foil is electrolytically treated on the glossy surface to form a roughened copper deposit, and the roughened surface is electrolytically treated to deposit metal or alloy micronodules. Preferably, this is not necessary. The nodules are preferably copper or a copper alloy, which enhances adhesion to the substrate rather than roughening the surface. The surface microstructure of the copper foil is measured with a profilometer such as a Perthometer model M4P or S5P available from Mahr Feinpruef Corporation of Cincinnati, Ohio. Topographic measurements of the surface grain structure consisting of peaks and valleys are performed according to the industry standard IPC-TM-650 section 2.2.17 of the Institute for Interconnecting and Packaging Circuits at 2115 Sanders Road, Northbrook, Illinois 60062. In the measurement procedure, the evaluation length Im of the sample surface is set. Rz is defined as the average maximum height from the top to the bottom of five consecutive sampling lengths within the evaluation length Im (where Io is Im / 5). Rt is the maximum roughness depth, which is the maximum vertical distance between the highest peak and the lowest valley in the evaluation length Im. Rp is the maximum leveling depth, which is the height of the highest peak within the evaluation length Im. Ra or average roughness is defined as the arithmetic average of the total absolute distance from the average line of the roughness curve within the evaluation length Im.
[0017]
The important parameters for the present invention are Rz and Ra. The applied surface treatment forms a surface structure having peaks and valleys, with roughness parameters ranging from about 1 to about 10 microns for Ra and about 2 to about 10 microns for Rz. The applied surface treatment forms a surface structure having peaks and valleys on the glossy surface, with a roughness parameter of Ra of about 1 to about 4 microns, preferably about 2 to about 4 microns, most preferably about 3 microns. ~ 4 microns. Rz values range from about 2 to about 4.5 microns, preferably from about 2.5 to about 4.5 microns, more preferably from about 3 to about 4.5 microns.
[0018]
The applied surface treatment forms a surface structure having peaks and valleys on the rough surface, wherein the roughness parameter is Ra of about 4 to about 10 microns, preferably about 4.5 to about 8 microns, most preferably It will be in the range of about 5 to about 7.5 microns. Rz values range from about 4 to about 10 microns, preferably from about 4 to about 9 microns, more preferably from about 4 to about 7.5 microns.
[0019]
It is preferable that the glossy surface has copper deposits of about 2 to 4.5 μm thick and has an average roughness (Rz) of 2 μm or more. Preferably, the rough surface has a roughness Rz of about 4-7.5 μm. Micronodules of metals or alloys should be about 0.5 μm in size. If desired, other metals, such as zinc, indium, tin, cobalt, brass, bronze, etc., can be deposited as micronodules. This method is described in more detail in US Pat. No. 5,679,230, which is incorporated herein by reference. The glossy surface has a peel strength ranging from about 0.7 kg / linear cm to about 1.6 kg / linear, preferably from about 0.9 kg / linear cm to about 1.6 kg / linear. The rough surface has a peel strength in the range of about 0.9 kg / linear cm to about 2 kg / linear, preferably about 1.1 kg / linear cm to about 2 kg / linear. Peel strength is measured according to industry standard IPC-TM-650 section 2.4.8 Rev. C.
[0020]
The conductive layer is preferably between about 0.5 and about 200 microns, more preferably between about 9 and about 70 microns. The conductive layer can be formed on the substrate by using any other known metal deposition method such as electroless deposition, coating, sputtering, or vapor deposition, or by bonding.
[0021]
It is also preferred, but not necessary, that the foil be electrolytically treated on either side using a thin metal layer prior to lamination, but this is not required.
[0022]
This metal layer is preferably electrodeposited on the conductive layer. The metal layer can also be deposited on the conductive layer (after bonding to the substrate) by coating, sputtering, or vapor deposition on the conductive layer, or by laminating. The metal layer is a thin film, and preferably includes a material selected from nickel, tin, palladium, platinum, chromium, titanium, molybdenum, or an alloy thereof. Most preferably, the metal layer comprises nickel or tin. The metal layer is preferably about 0.01 to about 10 microns, more preferably about 0.2 to about 3 microns thick. This metal layer acts as an etching mask and will define the pattern of circuit lines and circuit spaces to be etched into the conductive layer.
[0023]
Once the metal layer has been deposited on the conductive layer, the next step is to selectively etch away the metal layer portions to form an etched pattern in the metal layer. This etching pattern is formed by a known photolithography technique using a photoresist composition. First, a photoresist is deposited directly on the thin metal layer. Photoresist compositions may be positive or negative, and are generally commercially available.
[0024]
Photoresists can be very thin (5-20 microns) because their primary function is only to define patterns in thin metal films and does not need to withstand harsh etching conditions. Thereby, the resolution is significantly improved. Suitable positive photoresists are well known in the art and can include an o-quinonediazide radiosensitizer. Examples of the o-quinonediazide radiosensitizer include U.S. Pat. Nos. 2,797,213, 3,106,465, 3,148,983, 3,130,047, and 3,201,329. And o-quinone-4- or -5-sulfonyl-diazide disclosed in U.S. Pat. Nos. 3,785,825 and 3,802,885.
[0025]
When o-quinonediazide is used, preferred binding resins include those insoluble in water and soluble or swellable in aqueous alkali, preferably novolak. Suitable positive photodielectric resins are commercially available, for example, under the trade name AZ-P4620 from Clariant Corporation of Somerville, NJ, USA, as well as Shipley I-line photoresist. Negative photoresists are also widely marketed.
[0026]
The photoresist is then image-wise exposed through a mask to actinic radiation, such as light in the visible, ultraviolet, or infrared spectral region, or image-wise scanned with electron, ion or neutron, or x-ray radiation. I do. Actinic radiation can be in the form of incoherent or coherent light, for example, light from a laser. The photoresist is then developed image-wise with a suitable solvent, such as an aqueous alkaline solution, thereby exposing the underlying metal layer portion.
[0027]
Subsequently, the exposed underlying metal layer portion is removed by well-known etching techniques, leaving the portion under the residual photoresist. Suitable etchants include, but are not limited to, acidic solutions such as cupric chloride (preferably for etching nickel) or nitric acid (preferably for etching tin). Also preferred are ferric chloride or sulfuric peroxide (hydrogen peroxide with sulfuric acid). During this step, portions of the conductive layer underlying portions etched away from the metal layer are exposed. This patterned metal layer provides a high-accuracy, high-precision, high-quality etching mask for etching the conductive layer.
[0028]
Next, the exposed lower conductive layer portion is removed by etching while leaving the conductive layer portion under the remaining portion of the metal layer. Suitable etchants for removing the conductive layer include, but are not limited to, alkaline solutions such as ammonium chloride / ammonium hydroxide. The circuit board can then be washed and dried. As a result, a high-performance printed circuit board having excellent resolution and uniformity can be obtained.
[0029]
In another preferred embodiment in which the metal layer comprises nickel, a one-step etching process can be performed. In this embodiment, after the photoresist is imaged and developed, each of the exposed portions of the metal layer and the underlying conductive layer can be etched in a cupric chloride etchant. When etching other metal layers, including tin, even the appropriate etchant cannot accurately etch the underlying conductor foil, necessitating a second stage of etching. This one-step etch is preferred for etching lines and spaces greater than about 3 mils (0.08 mm). When using one-step etching, the residence time in the etchant may need to be extended by 10-25%, depending on the etching system. Higher spray pressures and temperatures can achieve the same result. After the circuit lines and spaces have been etched through the metal and conductive layers, the residual photoresist may be stripped with a suitable solvent or optionally removed from the metal layer surface by ashing using known ashing techniques. it can. The photoresist can also be removed after etching the metal layer and before etching the conductor foil.
[0030]
In a preferred ashing process, the plasma is generated in a microwave plasma generator located upstream of the stripping chamber, and the stripping gas passes through the generator, causing reactive species generated from the gas in the plasma to strike. You will enter the ripping chamber. Plasma ions are removed from plasma radicals by filtering or the like. As used herein, the term "radical" shall mean uncharged particles such as atoms and molecular fragments generated in an upstream plasma generator. The plasma generator can be any plasma generator known in the art. Plasma generators that can provide a radical source substantially free of ions and electrons are described, for example, in US Pat. Nos. 5,174,856 and 5,200,031, the disclosures of which are incorporated by reference. Is incorporated herein by reference. Although any type of plasma generated by conventional methods can be generally used in the practice of the present invention, the plasma used may be a micro-plasma such as a Model AURA plasma generator commercially available from GaSonics of San Jose, California, USA. It is preferably generated by a wave plasma generator. Another upstream plasma generator that can provide a radical source substantially free of electrons and / or ions is Applied Materials, Inc. as an Advanced Strip Passivation (ASP) chamber. It is commercially available from. Plasma asher is also commercially available from Mattson Technology of Fremont, California, USA. Ashing is performed by Tokyo Electron Ltd. It can also be performed by an anisotropic method using in-situ ashing in an etching chamber such as TEL DRM 85, commercially available from E.C.
[0031]
At this point, another insulating substrate may be laminated onto the circuit without an additional roughening step and without blackening the rough surface of the foil. The thin metal layer does not need to be removed after etching and acts as a replacement for the oxide and provides sufficient adhesion to form a multilayer structure. Further, the metal layer is more uniform and has a higher reflectance than the conductor foil alone, and is easily inspected using a well-known automatic optical inspection (AOI) apparatus.
[0032]
The following non-limiting examples serve to illustrate the invention.
[0033]
Example 1 : Treat the glossy surface of the copper foil to form copper nodules and apply a Zn-Cr barrier layer. The roughened surface is also treated to form nodules, but then treated with nickel. The foil is attached to glass fibers impregnated with epoxy (with the glossy surface in contact with this material) to produce a substrate. Liquid photoresist is applied to the substrate to a thickness of 12 microns and exposed to UV light through a mask to form an image. The photoresist is developed using potassium carbonate to expose the nickel surface. The nickel is removed using a cupric chloride etch to expose the underlying copper. This copper is etched using a system containing ammonia as a main component to determine the trace. The photoresist is removed using a sodium hydroxide solution. Drill holes around the substrate based on the image pattern. These holes are used for alignment. Inspect the traces using an automated optical inspection device and repair as needed (and if acceptable). The finished substrate (core) with the etched traces is glued together with other cores (if necessary) between epoxy glass fibers, with the copper foil outside. A hole is made in this "semi-finished product" of the printed circuit board, an external circuit is set, a solder mask is placed, and solder is attached to complete. The finished board is tested and then assembled.
[0034]
Example 2 Example 1 is repeated except that the rough surface of the laminate is brought into contact with the substrate and treated with Zn—Cr. The shiny surface has nodules plated as in Example 1, but treated with nickel.
[0035]
Example 3 : Example 2 was repeated except that the glossy surface was roughened by microetching before the nickel treatment.
[0036]
Example 4 : Example 2 was repeated except that the glossy surface was roughened by scrubbing with pumice before nickel treatment.
[0037]
Example 5 Example 1 is repeated except that the photoresist is of a permanent nature and is not removed after etching.
[0038]
Example 6 Example 1 is repeated except that etching is performed in one step using cupric chloride.
[0039]
Example 7 Example 1 is repeated except that the photoresist is exposed using a direct laser imaging system.
[0040]
Example 8 : Example 1 is repeated except that tin is plated instead of nickel and etched using nitric acid.
[0041]
Example 9 A copper foil is produced by electrodepositing copper from a solution onto a rotating metal drum according to Example 1 of US Pat. No. 3,293,109. The copper is dissolved in sulfuric acid and then electrodeposited as a copper sulfate in a solution of 70-105 g / L copper and 80-160 g / L free sulfuric acid at 40-60 ° C. This solution is brought into contact with a rotating metal drum, usually made of titanium. The rotating metal drum acts as a cathode and receives copper as it precipitates from solution. The anode is made of a lead alloy. An electrolytic cell voltage of about 5-10 V is applied between the anode and cathode to deposit copper. On the other hand, oxygen is generated at the anode. The copper is deposited on the drum as a continuous copper film approximately 18-70 m thick, which is removed, cut to the required width, and finally rolled. The copper foil surface in contact with the drum is smooth ("glossy surface") and the other surface is relatively rough ("rough surface").
[0042]
According to US Pat. No. 5,679,230, either the glossy or the rough side of the copper foil sample is treated to produce nodules on the surface. Either the glossy or rough side of another copper foil sample is microetched with cupric chloride. The surface roughness and peel strength of the copper foil sample are measured. Surface roughness is measured according to IPC-TM-650 section 2.2.17 and peel strength according to IPC-TM-650 section 2.4.8 Rev. C. The results are shown below.
[0043]
[Table 1]

[0044]
Although the present invention has been particularly shown and described with respect to preferred embodiments thereof, those skilled in the art will readily appreciate that various changes and modifications can be made without departing from the spirit and scope of the invention. There will be. It is intended that the following claims be interpreted to cover the disclosed embodiment, its alternatives discussed above, and all equivalents thereof.

Claims (43)

A method for manufacturing a printed circuit layer, comprising:
a) depositing a first surface of a conductive layer having a roughened second surface opposite the first surface on a substrate;
b) depositing a thin metal layer comprising a material having a different etching resistance than the conductive layer on the roughened second surface of the conductive layer;
Performing steps (a) and (b) in any order, and then c) depositing a photoresist on the metal layer;
d) exposing and developing the photoresist image-wise, thereby exposing the underlying metal layer portions;
e) removing the exposed underlying metal layer portion, thereby exposing the underlying conductive layer portion; and f) removing the exposed underlying conductive layer portion, thereby producing a printed circuit layer. Including methods. The method according to claim 1, wherein step a) is performed and then step b) is performed. The method according to claim 1, wherein step b) is performed, and then step a) is performed. 2. The step a) is performed by first roughening a second surface of the conductive layer, then treating with a second metal, and then depositing the first surface of the conductive layer on a substrate. The method described in. 2. The method according to claim 1, wherein step a) is performed by first roughening the second surface of the conductive layer and then depositing the first surface of the conductive layer on the substrate. 2. The method according to claim 1, wherein step a) is performed by first depositing a first surface of the conductive layer on the substrate and then roughening the second surface of the conductive layer. The method of claim 1, wherein the roughened second surface of the conductive layer has an average roughness (Ra) value ranging from about 1 to about 10 microns. The method of claim 1, wherein the roughened second surface of the conductive layer comprises a metal or metal alloy micronodule on or in the roughened second surface. The method of claim 1, wherein the roughened second surface of the conductive layer is microetched. 2. The steps a) to f) of claim 1 are repeated at least once, thereby producing a plurality of printed circuit layers, and then subsequently attaching the printed circuit layers to each other via at least one intermediate layer, whereby the printed circuit board Forming a composite material. The method of claim 1, further comprising, after step (e), removing the residual photoresist. The method of claim 1, further comprising, after step (f), removing residual photoresist. The method of claim 1, wherein the conductive layer comprises a conductive foil. The method of claim 1, wherein the metal layer comprises a metal foil. The method of claim 1, wherein the conductive layer comprises a material selected from the group consisting of copper, brass, stainless steel, aluminum, nickel, and alloys and combinations thereof. The method according to claim 1, wherein the conductive layer is a copper foil. The method according to claim 1, wherein the conductive layer is laminated on the substrate. The method according to claim 1, wherein the conductive layer is deposited on the substrate by electrolytic deposition or electroless deposition. The method according to claim 1, wherein the conductive layer is deposited on the substrate by coating, sputtering, or vapor deposition. The method of claim 1, wherein the metal layer comprises a material selected from the group consisting of nickel, tin, palladium, platinum, chromium, molybdenum, titanium, and alloys and combinations thereof. The method of claim 1, wherein the metal layer comprises nickel. The method of claim 1, wherein the metal layer comprises tin. The method according to claim 1, wherein the metal layer is laminated on the conductive layer. The method of claim 1, wherein the metal layer is deposited on the conductive layer by either an electrolytic deposition technique or an electroless deposition technique. The method of claim 1, wherein the metal layer is applied to the conductive layer by coating, sputtering, or vapor deposition. 2. The method of claim 1, wherein the exposed portions of the metal layer are removed by acid etching. The method according to claim 1, wherein the exposed portion of the conductive layer is removed by alkali etching. The method of claim 1, wherein the exposed portion of the metal layer and the underlying conductive layer portion are simultaneously removed by acid etching. The method of claim 1, wherein the substrate comprises a polymer film. The method of claim 1, wherein the substrate comprises a polyimide, polyester, or liquid crystal polymer film. The method of claim 1, wherein the substrate comprises a reinforced polymer. The method of claim 1, wherein the substrate comprises a reinforced polymer comprising epoxy, polyimide, cyanate, BT-epoxy, or a combination thereof. The method of claim 1, wherein the substrate comprises a reinforced polymer including fiberglass or organic paper. a) depositing a first surface of a conductive layer having a roughened second surface opposite the first surface on a substrate;
b) depositing a thin metal layer comprising a material having a different etching resistance than the conductive layer on the roughened second surface of the conductive layer;
Performing steps a) and b) in any order, and then c) depositing a photoresist on the metal layer;
d) exposing and developing the photoresist image-wise, thereby exposing the underlying metal layer portions;
e) removing the exposed underlying metal layer portion, thereby exposing the underlying conductive layer portion; and f) removing the exposed underlying conductive layer portion;
Printed circuit layer produced by the method of performing the above. 35. The printed circuit layer according to claim 34, wherein the conductive layer comprises a conductive foil. 35. The printed circuit layer according to claim 34, wherein the metal layer comprises a metal foil. 35. The printed circuit layer of claim 34, wherein the conductive layer comprises a material selected from the group consisting of copper, brass, stainless steel, aluminum, nickel, and alloys and combinations thereof. 35. The printed circuit layer according to claim 34, wherein the conductive layer comprises a copper foil. 35. The printed circuit layer of claim 34, wherein the metal layer comprises a material selected from the group consisting of nickel, tin, palladium, platinum, chromium, molybdenum, titanium, and alloys and combinations thereof. 35. The printed circuit layer according to claim 34, wherein the metal layer comprises nickel. 35. The printed circuit layer according to claim 34, wherein the metal layer comprises tin. 35. The printed circuit layer according to claim 34, wherein the substrate comprises a semiconductor. 35. The printed circuit layer of claim 34, wherein the substrate comprises gallium arsenide, silicon, a silicon-containing composition, and combinations thereof.