Abstract:
A method of producing a conductive path on a substrate including depositing on the substrate a layer of material having a thickness in the range of 0.1 to 5 microns, including metal particles having a diameter in the range of 10 to 100 nanometers, employing a patterning laser beam to selectably sinter regions of the layer of material, thereby causing the metal particles to together define a conductor at sintered regions and employing an ablating laser beam, below a threshold at which the sintered regions would be ablated, to ablate portions of the layer of material other than at the sintered regions.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to electrical circuit manufacturing and repair generally. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are many known techniques for producing and repairing conductive paths on substrates. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention seeks to provide an improved method of producing a conductive path on a substrate. 
         [0004]    There is thus provided in accordance with a preferred embodiment of the present invention a method of producing a conductive path on a substrate including depositing on the substrate a layer of material having a thickness in the range of 0.1 to 5 microns, including metal particles having a diameter in the range of 10 to 100 nanometers, employing a patterning laser beam to selectably sinter regions of the layer of material, thereby causing the metal particles to together define a conductor at sintered regions and employing an ablating laser beam, below a threshold at which the sintered regions would be ablated, to ablate portions of the layer of material other than at the sintered regions. 
         [0005]    Preferably, the depositing includes depositing using the ablating laser beam. 
         [0006]    In accordance with a preferred embodiment of the present invention the layer of material includes conductive ink. Additionally, the method of producing a conductive path on a substrate also includes drying the conductive ink prior to the employing a patterning laser beam and the employing an ablating laser beam. 
         [0007]    In accordance with a preferred embodiment of the present invention the patterning laser beam is a continuous laser beam and has a power level between 40-100 mW. Preferably, the ablating laser beam is a pulsed laser beam and has a fluence level between 1 and 500 miliJoule/cm 2 . More preferably, the ablating laser beam is a pulsed laser beam and has a fluence level between 30 and 100 miliJoule/cm 2 . 
         [0008]    In accordance with a preferred embodiment of the present invention the ablating laser beam is operative to ablate portions of the layer of material other than at the sintered regions without damaging other components on the substrate. 
         [0009]    Preferably, the employing a patterning laser beam is performed prior to the employing an ablating laser beam. Alternatively, the employing an ablating laser beam is performed prior to the employing a patterning laser beam. 
         [0010]    In accordance with a preferred embodiment of the present invention the method of producing a conductive path on a substrate also includes, prior to the depositing, defining at least two areas on the substrate forming part of the conductive path and employing an ablating laser beam to ablate portions of a non-conductive layer formed over the substrate in the at least two areas. 
         [0011]    There is also provided in accordance with another preferred embodiment of the present invention a method of producing a conductive path on a substrate including depositing on the substrate a layer of material having a thickness in the range of 0.1 to 5 microns, including metal particles having a diameter in the range of 10 to 100 nanometers, employing a patterning laser beam to selectably sinter regions of the layer of material, thereby causing the metal particles to together define a conductor at sintered regions and removing portions of the layer of material other than at the sintered regions. 
         [0012]    Preferably, the depositing includes depositing employing a second laser beam. 
         [0013]    In accordance with a preferred embodiment of the present invention the layer of material includes conductive ink. Additionally, the method of producing a conductive path on a substrate also includes drying the conductive ink prior to the employing a patterning laser beam. 
         [0014]    Preferably, the patterning laser beam is a continuous laser beam and has a power level between 40-100 mW: 
         [0015]    In accordance with a preferred embodiment of the present invention the removing includes removing portions of the layer of material other than at the sintered regions without damaging other components on the substrate. 
         [0016]    Preferably, the method of producing a conductive path on a substrate also includes, prior to the depositing, defining at least two areas on the substrate forming part of the conductive path and employing an ablating laser beam, to ablate portions of a non-conductive layer formed over the substrate in the at least two areas. 
         [0017]    There is further provided in accordance with yet another preferred embodiment of the present invention a system for producing a conductive path on a substrate including an optical assembly including a patterning laser, operative to generate a patterning laser beam and an ablating laser, operative to generate an ablating laser beam and a substrate positioning assembly, movable relative to the optical assembly, operative to position the optical assembly relative to a substrate, the patterning laser beam being operative to selectably sinter regions of a layer of material having a thickness in the range of 0.1 to 5 microns, including metal particles having a diameter in the range of 10 to 100 nanometers, deposited on the substrate, thereby causing the metal particles to together define a conductor at sintered regions and the ablating laser beam, being operative, below a threshold at which the sintered regions would be ablated, to ablate portions of the layer of material other than at the sintered regions. 
         [0018]    Preferably, the substrate positioning assembly is moveable in both x and y directions relative to the optical assembly. 
         [0019]    In accordance with a preferred embodiment of the present invention the patterning laser is a continuous wave laser. Additionally or alternatively, the ablating laser is a pulsed laser. 
         [0020]    Preferably, the system for producing a conductive path on a substrate also includes a blower. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The present invention will be understood and appreciated from the following detailed description taken together with the drawings in which: 
           [0022]      FIG. 1A  is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with a preferred embodiment of the present invention; 
           [0023]      FIG. 1B  is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with a preferred embodiment of the present invention, illustrating one particular feature of the embodiment; 
           [0024]      FIG. 2  is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with another preferred embodiment of the present invention; 
           [0025]      FIG. 3A  is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with yet another preferred embodiment of the present invention; 
           [0026]      FIG. 3B  is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with still another preferred embodiment of the present invention; and 
           [0027]      FIG. 4  is a simplified illustration of a system for carrying out the methodologies of  FIGS. 1A-3B . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    Reference is now made to  FIG. 1A , which is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with a preferred embodiment of the present invention. As seen in  FIG. 1A , a visual inspection is carried out by an operator using a workstation  100 , coupled to a conductive path generator  102 , which will be described hereinbelow with respect to  FIG. 4 . 
         [0029]    The operator typically sees a portion of a conductive path  104  having a cut  106  therein and indicates a designated repair region  108 , as seen in enlargement A, which may be drawn automatically by the workstation  100  or manually by the operator using the workstation  100 . Designated repair region  108  preferably not only includes the cut  106  but also adjacent regions  110  and  112  of the conductive path  104 . 
         [0030]    As seen in enlargement B, a conductive ink, such as a nanoparticle silver ink, a nanoparticle copper ink, or a non-metal conductive ink, for example, a carbon nanotube ink, is deposited over a region  114 , extending beyond the designated repair region  108  and also covering adjacent regions  116  and  118  of the conductive path  104  and regions  120  alongside the conductive path being repaired. The deposition of the conductive ink is preferably carried out by using a laser beam which impinges on a donor substrate, typically a transparent donor substrate, coated with the conductive ink. The laser beam is typically produced by a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France. Alternatively, the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate. The conductive ink is then dried, preferably by use of a suitable blower or by laser heating thereof. 
         [0031]    Nanoparticle silver inks are commercially available from Sun Chemical Corp., Parsippany, N.J., USA, E.I. Du Pont De Nemours and Co., Wilmington, Del., USA, Amepox Microelectronics Ltd. of Lodz, Poland, Kunshan Hisense Electronics Co, Ltd of Jiangsu Province, China, and PV Nano Cell, Ltd. of Migdal Ha&#39;Emek, Israel. Nanoparticle copper ink is commercially available from Intrinsiq Materials Inc. of Rochester, N.Y., USA. Carbon nanotube inks are commercially available from Brewer Science of Rolla, Mo., USA. 
         [0032]    Preferably, the deposited layer has a thickness in the range of 0.1 to 5 microns and includes conductive particles having a diameter in the range of 10-100 nanometers. 
         [0033]    As seen in enlargement C, laser sintering is preferably carried out in the designated repair region  108  and as seen in enlargement D, laser trimming is preferably carried out along the periphery thereof, thus removing unsintered conductive ink from regions  116 ,  118  and  120 . Preferably, but not necessarily, laser trimming may be carried out using the same laser employed for deposit of the conductive ink. 
         [0034]    It is a particular feature of the present invention that laser trimming and removal of unsintered conductive ink from regions  116  and  118  overlying the conductive path  104  is achieved without damaging the conductive path by the use of a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec and a pulse energy fluence of between 1 to 500 miliJoule/cm 2 , and more particularly between 30 to 100 miliJoule/cm 2 . 
         [0035]    Reference is now made to  FIG. 1B , which is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with a preferred embodiment of the present invention, illustrating one particular feature of this embodiment. 
         [0036]    As seen in  FIG. 1B , a visual inspection is carried out by an operator using a workstation  100 , coupled to a conductive path generator  102 , which will be described hereinbelow with respect to  FIG. 4 . 
         [0037]    The operator typically sees a portion of a conductive path  104  having a cut  106  therein and indicates a designated repair region  108 , as seen in enlargement A, which may be drawn automatically by the workstation  100  or manually by the operator using the workstation  100 . Designated repair region  108  preferably not only includes cut  106  but also adjacent regions  110  and  112  of the conductive path  104 . 
         [0038]    As seen in enlargement B, a conductive ink, such as a nanoparticle silver ink, a nanoparticle copper ink, or a non-metal conductive ink, for example, a carbon nanotube ink, is deposited over a region  114 , extending beyond the designated repair region  108  and also covering adjacent regions  116  and  118  of the conductive path  104  and regions  120  alongside the conductive path being repaired as well as a region  130 , which covers part of an adjacent conductive path  132 . The deposition of the conductive ink is preferably carried out by using a laser beam which impinges on a donor substrate, typically a transparent donor substrate, coated with the conductive ink. The laser beam is typically produced by a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France. Alternatively, the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate. The conductive ink is then dried, preferably by use of a suitable blower or by laser heating thereof. 
         [0039]    Nanoparticle silver inks are commercially available from Sun Chemical Corp., Parsippany, N.J., USA, E.I. Du Pont De Nemours and Co., Wilmington, Del., USA, Amepox Microelectronics Ltd. of Lodz, Poland, Kunshan Hisense Electronics Co, Ltd of Jiangsu Province, China, and PV Nano Cell, Ltd. of Migdal Ha&#39;Emek, Israel. Nanoparticle copper ink is commercially available from Intrinsiq Materials Inc. of Rochester, N.Y., USA. Carbon nanotube inks are commercially available from Brewer Science of Rolla, Mo., USA. 
         [0040]    Preferably, the deposited layer has a thickness in the range of 0.1 to 5 microns and includes conductive particles having a diameter in the range of 10-100 nanometers. 
         [0041]    As seen in enlargement C, laser sintering is preferably carried out in the designated repair region  108  and as seen in enlargement D, laser trimming is preferably carried out along the periphery thereof, thus removing unsintered conductive ink from regions  116 ,  118 ,  120  and  130 . Preferably, but not necessarily, laser trimming may be carried out using the same laser employed for deposit of the conductive ink. 
         [0042]    It is a particular feature of the present invention that laser trimming and removal of unsintered conductive ink from regions  116  and  118  overlying the conductive path  104  and from region  130  overlying part of adjacent conductive path  132  is achieved without damaging the conductive paths or other circuit elements, such as silicon-based transistors, capacitors and resistors and transparent conductors, by the use of a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec and a pulse energy fluence of between 1 to 500 miliJoule/cm 2 , and more particularly between 30 to 100 miliJoule/cm 2 . This is particularly important in cases where adjacent conductive paths and circuit elements are particularly close together in the micron range. 
         [0043]    Reference is now made to  FIG. 2 , which is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with another preferred embodiment of the present invention, As seen in  FIG. 2 , a visual inspection is carried out by an operator using a workstation  100 , coupled to a conductive path generator  102 , which will be described hereinbelow with respect to  FIG. 4 . 
         [0044]    The operator typically sees a portion of a conductive path  104  having a cut  106  therein and indicates a designated repair region  108 , as seen in enlargement A, which may be drawn automatically by the workstation  100  or manually by the operator using the workstation  100 . The designated repair region  108  preferably not only includes the cut  106  but also adjacent regions  110  and  112  of the conductive path  104 . 
         [0045]    As seen in enlargement B, a conductive ink, such as a nanoparticle silver ink, a nanoparticle copper ink, or a non-metal conductive ink, for example, a carbon nanotube ink, is deposited over a region  114 , extending beyond the designated repair region  108  and also covering adjacent regions  116  and  118  of the conductive path  104  and regions  120  alongside the conductive path being repaired. The deposition of the conductive ink is preferably carried out by using a laser beam which impinges on a donor substrate, typically a transparent donor substrate, coated with the conductive ink. The laser beam is typically produced by a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France. Alternatively, the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate. The conductive ink is then dried, preferably by use of a suitable blower or by laser heating thereof. 
         [0046]    Nanoparticle silver inks are commercially available from Sun Chemical Corp., Parsippany, N.J., USA, E.I. Du Pont De Nemours and Co., Wilmington, Del., USA, Amepox Microelectronics Ltd. of Lodz, Poland, Kunshan Hisense Electronics Co, Ltd of Jiangsu Province, China, and PV Nano Cell, Ltd. of Migdal Ha&#39;Emek, Israel. Nanoparticle copper ink is commercially available from Intrinsiq Materials Inc. of Rochester, N.Y., USA. Carbon nanotube inks are commercially available from Brewer Science of Rolla, Mo., USA. 
         [0047]    Preferably, the deposited layer has a thickness in the range of 0.1 to 5 microns and includes conductive particles having a diameter in the range of 10-100 nanometers. 
         [0048]    As seen in enlargement C, as distinguished from the embodiments of  FIGS. 1A-1B , laser trimming is preferably carried out to remove conductive ink from regions  120  alongside the conductive path being repaired. This provides relatively high resolution repaired conductive path edge definition, preferably providing edge definition accuracy and uniformity below one micron. 
         [0049]    As seen in enlargement D, laser sintering is preferably carried out in the remaining part of designated repair region  108  and as seen in enlargement E, further laser trimming is preferably carried out along the periphery thereof, thus removing unsintered conductive ink from regions  116  and  118 . Preferably, but not necessarily, laser trimming may be carried out using the same laser employed for deposit of the conductive ink. 
         [0050]    It is a particular feature of the present invention that laser trimming and removal of unsintered conductive ink from regions  116  and  118  overlying the conductive path  104  is achieved without damaging the conductive path by the use of a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec and a pulse energy fluence of between 1 to 500 miliJoule/cm 2 , and more particularly between 30 to 100 miliJoule/cm 2 . 
         [0051]    In an alternative preferred embodiment of the present invention, unsintered conductive ink may be removed from regions  116  and  118  overlying the conductive path  104  without damaging the conductive path by washing the substrate with a suitable solvent. Suitable solvents include water, ethanol, iso-propanol, cyclohexanol or other aliphatic alcohols, acetone, methyl ethyl ketone, cyclohaxanone or other ketones, glycol ethers and glycols ether acetates. Additionally, additives such as surfactants and chelating agents may be added to enhance the process. Such surfactants and chelating agents are commercially available from suppliers, such as Sigma-Aldrich Corporation of St Louis, Mo., USA and Tokyo Chemical Industry Co Ltd of Tokyo, Japan, or manufacturers, such as Dow Chemical Company of Midland, Mich., USA. This alternative embodiment is particularly useful when the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate, which may result in a large area of unsintered ink. 
         [0052]    Reference is now made to  FIG. 3A , which is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with yet another preferred embodiment of the present invention. Here, as distinguished from the embodiments of  FIGS. 1A-2 , a bypass conductive path is generated. This is particularly useful when there exist circuit elements, such as a conductor in a cross direction underneath the conductor to be repaired, in the vicinity of a cut  106  in a conductive path  104 . 
         [0053]    It is appreciated that the functionality of  FIG. 3A  may be employed both inside and outside of the repair context for writing with ink from a donor substrate onto a substrate in a desired pattern. This may be used, for example, for depositing highly conductive materials in relatively large regions, as for making large repairs on a substrate. 
         [0054]    As seen in  FIG. 3A , a visual inspection is carried out by an operator using a workstation  100 , coupled to a conductive path generator  102 , which will be described hereinbelow with respect to  FIG. 4 . 
         [0055]    The operator typically sees a portion of a conductive path  104  having a cut  106  therein and indicates a designated bypass region  134 , as seen in enlargement A, which may be drawn automatically by the workstation  100  or manually by the operator using the workstation  100 . The designated bypass region  134  includes regions  135  and  136  which overlap portions of the conductive path  104 . 
         [0056]    As seen in enlargement B, a conductive ink, such as a nanoparticle silver ink, a nanoparticle copper ink, or a non-metal conductive ink, for example, a carbon nanotube ink, is deposited over a region  137 , extending beyond the designated bypass region  134  and also covering adjacent regions  138  along and outside the peripheral edges of designated bypass region  134 . The deposition of the conductive ink is preferably carried out by using a laser beam which impinges on a donor substrate, typically a transparent donor substrate, coated with the conductive ink. The laser beam is typically produced by a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France. Alternatively, the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate. The conductive ink is then dried, preferably by use of a suitable blower or by laser heating thereof. 
         [0057]    Nanoparticle silver inks are commercially available from Sun Chemical Corp., Parsippany, N.J., USA, E.I. Du Pont De Nemours and Co., Wilmington, Del., USA, Amepox Microelectronics Ltd. of Lodz, Poland, Kunshan Hisense Electronics Co, Ltd of Jiangsu Province, China, and PV Nano Cell, Ltd. of Migdal Ha′Emek, Israel. Nanoparticle copper ink is commercially available from Intrinsiq Materials Inc. of Rochester, N.Y., USA. Carbon nanotube inks are commercially available from Brewer Science of Rolla, Mo., USA. 
         [0058]    Preferably, the deposited layer has a thickness in the range of 0.1 to 5 microns and includes conductive particles having a diameter in the range of 10-100 nanometers. 
         [0059]    As seen in enlargement C, laser sintering is preferably carried out in the designated bypass region  134  and as seen in enlargement D, laser trimming is preferably carried out along the periphery thereof, thus removing unsintered conductive ink from regions  138 . Preferably, but not necessarily, laser trimming may be carried out using the same laser employed for deposit of the conductive ink. 
         [0060]    It is a particular feature of the present invention that laser trimming and removal of unsintered conductive ink from regions  138  overlying the conductive path  104  is achieved without damaging the conductive path by the use of a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec, and a pulse energy fluence of between 1 to 500 miliJoule/cm 2 , and more particularly between 30 to 100 miliJoule/cm 2 . 
         [0061]    In an alternative preferred embodiment of the present invention, unsintered conductive ink may be removed from regions  138  overlying the conductive path  104  without damaging the conductive path by washing the substrate with a suitable solvent. Suitable solvents include water, ethanol, iso-propanol, cyclohexanol or other aliphatic alcohols, acetone, methyl ethyl ketone, cyclohaxanone or other ketones, glycol ethers and glycols ether acetates. Additionally, additives such as surfactants and chelating agents may be added to enhance the process. Such surfactants and chelating agents are commercially available from suppliers, such as Sigma-Aldrich Corporation of St Louis, Mo., USA and Tokyo Chemical Industry Co Ltd of Tokyo, Japan, or manufacturers, such as Dow Chemical Company of Midland, Mich., USA. This alternative embodiment is particularly useful when the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate, which may result in a large area of unsintered ink. 
         [0062]    Reference is now made to  FIG. 3B , which is a simplified illustration of the operation of a system and method for producing a conductive path on a substrate in accordance with yet another preferred embodiment of the present invention. Here, as distinguished from the embodiment of  FIG. 3A , conductor  104  and some or all of the substrate have been covered by an additional non-conductive layer and a bypass conductive path is generated above the additional non-conductive layer. 
         [0063]    As seen in  FIG. 3B , a visual inspection is carried out by an operator using a workstation  100 , coupled to a conductive path generator  102 , which will be described hereinbelow with respect to  FIG. 4 . 
         [0064]    The operator typically sees a portion of a conductive path  104  having a cut  106  therein and indicates a designated bypass region  140 , as seen in enlargement A, which may be drawn automatically by the workstation  100  or manually by the operator using the workstation  100 . The designated bypass region  140  includes regions  141  and  142  which overlap portions of the conductive path  104 . As seen particularly in enlargement B, conductive path  104  is covered by a non-conductive layer  143 , which typically also covers some or all of the rest of the substrate. 
         [0065]    As seen further in enlargement B, laser ablation of areas of non-conductive layer  143  from a portion of regions  141  and  142 , here designated by reference numbers  144  and  145 , overlying conductive path  104  is performed, typically using a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec, and a pulse energy fluence of between 100 to 1500 miliJoule/cm 2 , and more particularly between 300 to 1000 miliJoule/cm 2 . 
         [0066]    As seen in enlargement C, a conductive ink, such as a nanoparticle silver ink, a nanoparticle copper ink, or a non-metal conductive ink, for example, a carbon nanotube ink, is deposited over a region  146 , extending beyond the designated bypass region  140  and also covering adjacent regions  148  along and outside the peripheral edges of designated bypass region  140 . The conductive ink is also deposited into areas  144  and  145 , thereby forming a conductive connection from conductive path  104  to bypass region  140 . 
         [0067]    The deposition of the conductive ink is preferably carried out by using a laser beam which impinges on a donor substrate, typically a transparent donor substrate, coated with the conductive ink. The laser beam is typically produced by a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France. Alternatively, the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate. The conductive ink is then dried, preferably by use of a suitable blower or by laser heating thereof. 
         [0068]    Nanoparticle silver inks are commercially available from Sun Chemical Corp., Parsippany, N.J., USA, E.I. Du Pont De Nemours and Co., Wilmington, Del., USA, Amepox Microelectronics Ltd. of Lodz, Poland, Kunshan Hisense Electronics Co, Ltd of Jiangsu Province, China, and PV Nano Cell, Ltd. of Migdal Ha′Emek, Israel. Nanoparticle copper ink is commercially available from Intrinsiq Materials Inc. of Rochester, N.Y., USA. Carbon nanotube inks are commercially available from Brewer Science of Rolla, Mo., USA. 
         [0069]    Preferably, the deposited layer has a thickness in the range of 0.1 to 5 microns and includes conductive particles having a diameter in the range of 10-100 nanometers. 
         [0070]    As seen in enlargement D, laser sintering is preferably carried out in the designated bypass region  140  and as seen in enlargement E, laser trimming is preferably carried out along the periphery thereof, thus removing unsintered conductive ink from regions  148 . Preferably, but not necessarily, laser trimming may be carried out using the same laser employed for deposit of the conductive ink. 
         [0071]    It is a particular feature of the present invention that laser trimming and removal of unsintered conductive ink from regions  148  overlying the conductive path  104  is achieved without damaging the conductive path by the use of a pulsed laser at a pulse length of between 10 psec to 100 nsec and more particularly between 100 psec and 10 nsec, and a pulse energy fluence of between 1 to 500 miliJoule/cm 2 , and more particularly between 30 to 100 miliJoule/cm 2 . 
         [0072]    In an alternative preferred embodiment of the present invention, unsintered conductive ink may be removed from regions  148  overlying the conductive path  104  without damaging the conductive path by washing the substrate with a suitable solvent. Suitable solvents include water, ethanol, iso-propanol, cyclohexanol or other aliphatic alcohols, acetone, methyl ethyl ketone, cyclohaxanone or other ketones, glycol ethers and glycols ether acetates. Additionally, additives such as surfactants and chelating agents may be added to enhance the process. Such surfactants and chelating agents are commercially available from suppliers, such as Sigma-Aldrich Corporation of St Louis, Mo., USA and Tokyo Chemical Industry Co Ltd of Tokyo, Japan, or manufacturers, such as Dow Chemical Company of Midland, Mich., USA. This alternative embodiment is particularly useful when the conductive ink is deposited onto the repair location using an inkjet printer head or a dispensing tool for deposition of such ink locally on a substrate, which may result in a large area of unsintered ink. 
         [0073]    Reference is now made to  FIG. 4 , which is a simplified illustration of a system for carrying out the methodologies of  FIGS. 1A-3B . 
         [0074]    As seen in  FIG. 4 , the system preferably includes workstation  100  and conductive path generator  102 . Workstation  100  preferably includes a computer  150 , including a user input interface  152  and a display  154 . 
         [0075]    Conductive path generator  102  preferably comprises a substrate positioning assembly  156  including a chassis  160 , which is preferably mounted on a conventional optical table  162 . The chassis  160  defines a substrate inspection location  164  onto which a substrate  166 , typically an electrical circuit, such as a printed circuit board (PCB) or flat panel display (FPD), to be inspected and/or repaired, may be placed. Substrate  166  typically has one or more of various types of defects, such as missing conductor defects, for example cut  106 . 
         [0076]    Substrate positioning assembly  156  also preferably includes a bridge  170  arranged for linear motion relative to inspection location  164  along a first inspection axis  174  defined with respect to chassis  160 . 
         [0077]    Preferably, conductive path generator  102  also comprises an optical assembly  176 , preferably arranged for linear motion relative to bridge  170  along a second inspection axis  178 , perpendicular to first inspection axis  174 . Alternatively, the optical assembly  176  may be a stationary optical assembly and chassis  160  may be a moveable chassis operative to provide X and Y movement of substrate  166  relative to optical assembly  176 . 
         [0078]    Workstation  100  preferably also includes software modules operative to operate optical assembly  176  and substrate positioning assembly  156 . Workstation  100  preferably receives a defect location input from an automatic optical inspection system, not shown, such as a Discovery™ 8000 system or a Supervision™ system, both commercially available from Orbotech Ltd. of Yavne, Israel. 
         [0079]    As seen in enlargement A, which is a schematic block diagram of optical assembly  176 , optical assembly  176  preferably includes a camera  200 , which views the substrate  166 , preferably via a lens assembly  202 , a beam combiner  204  and an objective lens assembly  206 , and provides an operator sensible image of conductive paths  104  on display  154 . 
         [0080]    Optical assembly  176  also preferably includes a pulsed laser  210 , typically a short pulse, nanosecond pulsed laser with emission in the UV, Visible or NIR range, such as a microchip laser commercially available from Teem Photonics, Meylan, France, which emits a laser beam  212  which passes through a lens assembly  214 , a beam combiner  216  and a further lens assembly  218  and impinges on a fast scanning mirror  220 , which directs it via a relay optical assembly  222  and is reflected by beam combiner  204  via objective lens assembly  206 . Laser beam  212  then impinges on a selectably positionable conductive ink donor substrate  230  to deposit conductive ink onto substrate  166 . It is appreciated that pulsed laser  210  is preferably operative during the conductive ink deposition and laser trimming stages described hereinabove. 
         [0081]    Optical assembly  176  also preferably includes a continuous wave laser  240 , typically a high power, single mode, diode laser emitting in near UV, visible or Near IR, such as a GaN 405 nm DL, commercially available from Nichia Corporation of Tokushima, Japan, a Red/Near IR emitting LD, commercially available from Blue Sky Research, Milpitas, Calif., USA, a Cobolt 05-01 series CW DPSS laser from Cobolt AB Stockholm, Sweden, Spectra-Physics Excelsior series CW DPSS lasers, commercially available from Newport Corporation of Irvine Ca, USA, or any other suitable high power continuous wave laser, which emits a laser beam  242  which passes through a lens assembly  244 , beam combiner  216  and further lens assembly  218  and impinges on fast scanning mirror  220 , which directs it via relay optical assembly  222  and is reflected by beam combiner via objective lens assembly  206  onto substrate  166 . It is appreciated that continuous wave laser  240  is preferably operative during the laser sintering stage described hereinabove. 
         [0082]    Preferably, continuous wave laser  240  operates at a power level between 40-100 mW, a scan speed between 0.5-10 mm/sec, more preferably between 1-3 mm/sec and a spot size of 2-10 microns. 
         [0083]    It is appreciated that selectably positionable conductive ink donor substrate is selectably positionable for positioning in the optical path of laser beam  212 , for deposition of conductive ink on substrate  166  during the conductive ink deposition stage described hereinabove, and outside of the optical path of objective lens assembly  206 , during the imaging, laser trimming and laser sintering stages described hereinabove. 
         [0084]    Preferably, a blower  250  is provided adjacent an impingement location on substrate  166  of conductive ink from donor substrate  230 , for quick drying of the conductive ink. 
         [0085]    It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the claims which follow and include variations and modifications which would occur to persons skilled in the art upon reading the foregoing and which are not in the prior art.