Method for forming a conductive pattern

A method for forming a conductive pattern on a substrate (208) includes providing an image pattern for imaging on the substrate; imaging the image pattern on the substrate creating imaged areas; spraying functional material (240) on the substrate that diffuse molecules of the functional material into the imaged areas and wherein the functional material is in a form of liquid; and applying electro-less copper coating that builds conductive material traces on the imaged areas on the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

FIELD OF THE INVENTION

The present invention relates to an apparatus for functional printing using computer-to-plate imaging technology.

BACKGROUND OF THE INVENTION

Functional printing is a category of printing that uses commercial printing equipment to print circuits or electronic devices which have a function other than, or in addition to, visual display of information. An example of printed circuits is printing radio frequency identification (RFID) on a package or a product. Another example may be printing an electronic circuit on a package which is capable of producing music when the package is opened.

There are several approaches for printing functional patterns on substrates including direct printing of functional inks Other techniques use photolithography to mask and remove a pre-deposited functional layer. There is a need however for accurate deposition for functional material.

SUMMARY OF THE INVENTION

Briefly, according to one aspect of the present invention a method for forming a conductive pattern on a substrate includes providing an image pattern for imaging on the substrate; imaging the image pattern on the substrate creating imaged areas; spraying functional material on the substrate that diffuse molecules of the functional material into the imaged areas and wherein the functional material is in a form of liquid; and applying electro-less copper coating that builds conductive material traces on the imaged areas on the substrate.

One embodiment of the invention uses thermal writing devices, e.g. laser writing heads, or thermal transfer writing heads, to form a thermal pattern on the substrate which, combined with the chemical environment, forms a pattern of functional chemical traces on the substrate. This pattern can be used as is for various applications such as forming hydrophilic/hydrophobic regions for printing processes. Another use is to form a pattern of a catalyst material that can be used for electro-less deposition of metal such as copper, thereby forming copper traces on the substrate.

The use of laser imaging or thermal transfer to a substrate with a combination of sprayed material such as gas applied on the imaged areas is one technology for accurate deposition. The gas molecules are diffused towards the laser heated substrate to create a chemical compound between the gas and the material deposited on the surface of the substrate. The gas is referred to as functional gas and creates a compound of traces on the substrate that is used to form conductive lines for example.

The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.

While the present invention is described in connection with one of the embodiments, it will be understood that it is not intended to limit the invention to this embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents as covered by the appended claims.

FIG. 1shows a plate imaging device108. The imaging device is driven by a digital front end (DFE)104. The DFE receives imaging data in a digital form from desktop publishing (DTP) systems (not shown), and renders the digital information for imaging. The rendered information and imaging device control data are communicated between DFE104and imaging device108over interface line112.

FIG. 2Ashows an imaging system200. The imaging system200includes an imaging carriage212on which a material spray element224is mounted along with a thermal imaging head220. The sprayed material can be in a form of gas, liquid or fine powder. The thermal imaging head220can be based on thermal transfer means or laser imaging components. The thermal imaging head220is designed to operate of a wavelength matching the substrate208characteristics. The thermal imaging head220is configured to image on substrate208mounted on a rotating cylinder204. The carriage212is adapted to move substantially in parallel to cylinder204guided by screw216. Controller228controls patterning process of thermal imaging head220and material emission from material spray element224. A computer-to-plate (CTP) device capable to image on flat surfaces, known as capstan devices, can be used as well for the same purpose (not shown). An internal drum CTP (not shown) configuration can be used in conjunction with this invention as well.

Imaging substrate208, comprised of glass, metal or various polymeric materials, is mounted on rotating cylinder204. Depending on the specific process, a material spray element224deploys a material in proximity of imaging substrate208. The material may be applied prior, during or after laser exposure. Thermal imaging head220will image a pattern according to data received from DFE104on imaging substrate208. The CTP imaging head220will elevate the temperature of imaging substrate208, or opto-chemically modify its surface in the imaged areas to enable an efficient diffusion/bonding process of the functional sprayed material232molecules into substrate208. Thus, the pattern created by thermal imaging head220induces a doping pattern on imaging substrate208. For example, near IR (NIR) imaging head can be used for imaging on a specialized NIR absorbing polyethylene terephthalate (PET) substrate, while applying catalyst material in a form of gas or liquid, such as 3-mercaptopropyltrimethoxysilane (MPTS) or palladium fine powder, to create traces of catalyst doping on imaging substrate208. The liquid material may be Palladium Chloride (PdCl2) solution.

FIG. 2Bshows another imaging system250, similar to imaging system200. The main difference between the systems is that system250contains an integrated imaging and spaying element222.

FIG. 2Cshows yet another imaging system280. System280contains a chamber236. Chamber236carries functional material240. Chamber236is situated in proximity to rotating cylinder204is such a way that during rotation cylinder204and imaging substrate208immerses in functional material240in chamber236. Thermal imaging head220images through chamber236, causing temperature elevation on specific areas of imaging substrate208, and thus opto-chemically modify its surface in the imaged areas to enable an efficient diffusion/bonding process of the functional material240.

All the imaging systems presented show an external drum system, showing imaging substrate208attached on the external surface of rotating cylinder204. A configuration which is not shown herein, may be constructed from a thermal imaging head220configured in an internal drum configuration wherein imaging substrate208is attached on the internal surface of rotating cylinder204. In addition imaging head220will emit light internally in rotating cylinder204. The functional material will be also supplied internally inside the drum.

Following the completion of the required patterning on imaging substrate208, a standard electro-less coating process is performed to build material traces such as copper, silver or nickel traces on imaging substrate208by using electro-less coating machinery such as depicted inFIG. 3. These copper traces will form the pattern made by the CTP imaging head220. See Yinxiang Lu, Qian Liang, Longlong Xue, Applied Surface Science, Volume 258, Issue 10, 1 Mar. 2012, Pages 4782-4787.

Assuming the substrate heat capacity and density are ˜1.2 Jg-1K-1 and 1.37 gcm-3 respectively and assuming a penetration depth of 10 μm is required, energy in the vicinity of 1.644 mJ/cm2 will be needed for increasing substrate208temperature by 1K. Thus, to achieve 100K temperature an increase of 164 mJ/cm2 will be required, which within the working range of current CTP devices.

Patterning resolution is determined by the resolution of the CTP thermal imaging head220and by imaging substrate208characteristics such as thermal conductivity.

PARTS LIST