Abstract:
A system or apparatus for forming a conductive pattern on a substrate ( 208 ) includes a thermal imaging head ( 220 ) that forms an image pattern on the substrate. A functional material ( 240 ) spraying element ( 224 ) applies a functional material on the substrate which bonds with the image pattern. The spraying element is integrated in the thermal imaging head. An electro-less deposition element is applied using the electro-less deposition element on the substrate to enhance the functionality of the final product.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. 13/676,441, filed Nov. 14, 2012, entitled FUNCTIONAL PRINTING SYSTEM, by Schuster; U.S. patent application Ser. No. 13/676,464, filed Nov. 14, 2012, entitled METHOD FOR FUNCTIONAL PRINTING SYSTEM, by Schuster; and U.S. patent application Ser. No. ______ (Attorney Docket No. K001559USO1NAB), filed herewith, entitled METHOD FOR FORMING A CONDUCTIVE PATTERN, by Schuster; the disclosures of which are incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an apparatus for functional printing using computer-to-plate imaging technology. 
       BACKGROUND OF THE INVENTION 
       [0003]    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. 
         [0004]    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 
       [0005]    Briefly, according to one aspect of the present invention a system or apparatus for forming a conductive pattern on a substrate includes a thermal imaging head that forms an image pattern on the substrate. A functional material spraying element applies a functional material on the substrate which bonds with the image pattern. The spraying element is integrated in the thermal imaging head. An electro-less deposition element is applied using the electro-less deposition element on the substrate to enhance the functionality of the final product. 
         [0006]    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. 
         [0007]    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. 
         [0008]    The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  represents in diagrammatic form a prior art digital front end for driving an imaging device; 
           [0010]      FIG. 2A  represents in diagrammatic form the imaging system of  FIG. 1 ; 
           [0011]      FIG. 2B  represents in diagrammatic form an embodiment of the imaging system having the thermal imaging element embedded functional material spraying element; 
           [0012]      FIG. 2C  represents in diagrammatic form an embodiment of the imaging system having the thermal imaging element configured to image through a chamber carrying functional material; and 
           [0013]      FIG. 3  represents in a diagrammatic form an electro-less coating machinery applied on a patterned substrate according to this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    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. 
         [0015]    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. 
         [0016]      FIG. 1  shows a plate imaging device  108 . 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 DFE  104  and imaging device  108  over interface line  112 . 
         [0017]      FIG. 2A  shows an imaging system  200 . The imaging system  200  includes an imaging carriage  212  on which a material spray element  224  is mounted along with a thermal imaging head  220 . The sprayed material can be in a form of gas, liquid or fine powder. The thermal imaging head  220  can be based on thermal transfer means or laser imaging components. The thermal imaging head  220  is designed to operate of a wavelength matching the substrate  208  characteristics. The thermal imaging head  220  is configured to image on substrate  208  mounted on a rotating cylinder  204 . The carriage  212  is adapted to move substantially in parallel to cylinder  204  guided by screw  216 . Controller  228  controls patterning process of thermal imaging head  220  and material emission from material spray element  224 . 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. 
         [0018]    Imaging substrate  208 , comprised of glass, metal or various polymeric materials, is mounted on rotating cylinder  204 . Depending on the specific process, a material spray element  224  deploys a material in proximity of imaging substrate  208 . The material may be applied prior, during or after laser exposure. Thermal imaging head  220  will image a pattern according to data received from DFE  104  on imaging substrate  208 . The CTP imaging head  220  will elevate the temperature of imaging substrate  208 , or opto-chemically modify its surface in the imaged areas to enable an efficient diffusion/bonding process of the functional sprayed material  232  molecules into substrate  208 . Thus, the pattern created by thermal imaging head  220  induces a doping pattern on imaging substrate  208 . 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 substrate  208 . The liquid material may be Palladium Chloride (PdCl2) solution. 
         [0019]      FIG. 2B  shows another imaging system  250 , similar to imaging system  200 . The main difference between the systems is that system  250  contains an integrated imaging and spaying element  222 . 
         [0020]      FIG. 2C  shows yet another imaging system  280 . System  280  contains a chamber  236 . Chamber  236  carries functional material  240 . Chamber  236  is situated in proximity to rotating cylinder  204  is such a way that during rotation cylinder  204  and imaging substrate  208  immerses in functional material  240  in chamber  236 . Thermal imaging head  220  images through chamber  236 , causing temperature elevation on specific areas of imaging substrate  208 , and thus opto-chemically modify its surface in the imaged areas to enable an efficient diffusion/bonding process of the functional material  240 . 
         [0021]    All the imaging systems presented show an external drum system, showing imaging substrate  208  attached on the external surface of rotating cylinder  204 . A configuration which is not shown herein, may be constructed from a thermal imaging head  220  configured in an internal drum configuration wherein imaging substrate  208  is attached on the internal surface of rotating cylinder  204 . In addition imaging head  220  will emit light internally in rotating cylinder  204 . The functional material will be also supplied internally inside the drum. 
         [0022]    Following the completion of the required patterning on imaging substrate  208 , a standard electro-less coating process is performed to build material traces such as copper, silver or nickel traces on imaging substrate  208  by using electro-less coating machinery such as depicted in  FIG. 3 . These copper traces will form the pattern made by the CTP imaging head  220 . See Yinxiang Lu, Qian Liang, Longlong Xue, Applied Surface Science, Volume 258, Issue 10, 1 Mar. 2012, Pages 4782-4787. 
         [0023]    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 substrate 208 temperature 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. 
         [0024]    Patterning resolution is determined by the resolution of the CTP thermal imaging head  220  and by imaging substrate  208  characteristics such as thermal conductivity. 
         [0025]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
       PARTS LIST 
       [0026]      104  digital front end (DFE) 
         [0027]      108  imaging device 
         [0028]      112  interface line 
         [0029]      200  imaging system 
         [0030]      204  rotating cylinder 
         [0031]      208  imaging substrate 
         [0032]      212  carriage 
         [0033]      216  screw 
         [0034]      220  thermal imaging head 
         [0035]      222  thermal imaging head integrated with a spaying element 
         [0036]      224  material spray element 
         [0037]      228  controller 
         [0038]      232  sprayed material 
         [0039]      236  chamber containing functional material 
         [0040]      240  functional material 
         [0041]      250  imaging system 
         [0042]      280  imaging system