JP2020061553A - Printed circuit wiring repair - Google Patents

Abstract

To improve a laser-induced forward transfer method for repairing a metal wiring of a printed circuit board.SOLUTION: In a repairing device 20, a method includes a step of providing a transparent donor substrate 56 having opposing first and second surfaces and a donor film 58 formed on the second surface. The donor film has a thickness δ and a thermal diffusivity α and is characterized by a thermal diffusion time τ=(δ/4α). The donor substrate is close to an acceptor substrate and is positioned with the second surface facing the acceptor substrate. Multiple pulses of laser radiation having a pulse time less than or equal to twice the thermal diffusion time of the donor film pass through the first surface of the donor substrate and impinge on the donor film, and a plurality of droplets of a melting material are emitted from the donor film onto the acceptor substrate 41.SELECTED DRAWING: Figure 2

Description

  The present invention relates generally to laser organic mass transfer, and more particularly to methods and apparatus for repairing open metal defects in circuit wiring.

[Cross-reference of related applications]
This application claims the benefit of US provisional patent application 61 / 916,233, filed December 15, 2013. This application is a national continuation of PCT patent application PCT / IL2010 / 000106, filed February 7, 2010, and a partial continuation of US patent application 13 / 146,200 filed July 26, 2011. is there. All of these related applications are incorporated herein by reference.
In the laser direct writing (LDW) technique, a laser beam is used to produce a patterned surface with spatially resolved three-dimensional structures by controlled removal or deposition of material. Laser induced forward transfer (LIFT) is an LDW technique that can be applied to deposit micropatterns on surfaces.

  In LIFT, the laser photons provide the driving force to eject a small volume of material from the donor film towards the acceptor substrate. The laser beam typically interacts with the inside of a donor film that is coated on a non-absorbing carrier substrate. In other words, the incident laser beam propagates through the transparent carrier before the photons are absorbed by the inner surface of the film. Above a certain energy threshold, the substance is released from the donor film towards the surface of the substrate. Here, the substrate is generally placed in proximity to or in contact with the donor film in a LIFT system known in the art. The applied laser energy can be varied to control the forward propulsion thrust produced within the volume of the illuminated film. Nagel and Lippert are published in Nanomaterials: Processing and Characterization with Lasers, Singh et al., Eds. (Wiley-VCH Verlag GmbH & Co. KGaA, 2012), pages 255-316, `` Laser-Induced Forward Transfer for the "Fabrication of Devices" provides a useful survey of LIFT principles and applications in microfabrication.

  The use of LIFT in the repair of electrical circuits is known in the art. For example, WO 2010/100635, the disclosure of which is incorporated herein by reference, is a system and method for repairing electrical circuits in which a laser is used to pretreat a repaired area of a conductor formed on a circuit board. Enter. A laser beam is applied to the donor substrate to move a portion of the donor substrate away from it and move it to a predetermined conductor location.

  The embodiments of the invention described below provide improved methods and systems for LIFT that are particularly (but not exclusively) useful for repairing metal lines on substrates such as printed circuit boards.

According to an embodiment of the invention, the method comprises providing a transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface, the donor film having a thickness δ and a thermal resistance. A method of material deposition is provided that has a diffusivity α and is characterized by a thermal diffusion time τ = (δ ² / 4α). The donor substrate is close to the acceptor substrate and is positioned with the second surface facing the acceptor substrate. A pulse of laser radiation having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film is directed through the first side of the donor substrate, impinging on the donor film and from the donor film onto the acceptor substrate. Induces the ejection of droplets of molten material.

  In some embodiments, the donor film comprises a metal. In an exemplary embodiment, δ ≦ 1 μm and the pulse time of the laser pulse is less than 5 nanoseconds, and in some cases less than 2 nanoseconds.

  Additionally or alternatively, the step of directing a pulse directs a first pulse of laser radiation at a first pulse energy selected to promote deposition of droplets on the acceptor substrate, thereby causing a first pulse of laser radiation to be emitted. Following the step of directing two pulses, a step of forming an initial metal layer on the acceptor substrate with a second pulse energy greater than the first pulse energy and the droplet depositing metal on the initial metal layer.

  In the disclosed embodiment, the acceptor substrate is a printed circuit board, and the step of directing the pulse includes inducing metal deposition to repair defects in conductive traces on the printed circuit board.

  Usually the pulse time is less than or equal to the thermal diffusion time of the donor film.

  In the disclosed embodiment, the step of directing the pulse includes focusing the laser radiation to impinge on the donor film with a beam spot size that is at least 10 times the thickness δ of the donor film.

  According to an embodiment of the present invention, providing a transparent donor substrate having opposing first and second sides and a donor film formed on the second side, the donor film comprising a metal, A method of material deposition is provided that includes providing. The donor substrate is positioned close to the acceptor substrate with the second surface facing the acceptor substrate and a gap of at least 0.1 mm between the donor film and the acceptor substrate. A pulse of laser radiation is directed through the first side of the donor substrate, impinging on the donor film and inducing the ejection of metal droplets from the donor film through the gap onto the acceptor substrate.

  In some embodiments, the gap between the donor film and the acceptor substrate is at least 0.2 mm, or 0.5 mm, and the pulse of laser radiation impinges on the donor film.

  Further, according to embodiments of the present invention, a method of circuit repair is provided that includes identifying defects in conductive traces on a printed circuit board. The laser beam is directed to pre-treat defective sites on the printed circuit board. After pretreatment of the sites, a transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface is disposed adjacent to the site of the defect and the second Is positioned with the surface of the printed circuit board facing the printed circuit board. A pulse of laser radiation passes through the first side of the donor substrate and impinges on the donor film, inducing droplet ejection from the donor film at defect sites on the printed circuit board, thereby repairing the defect. Like,

  In some embodiments, directing the laser beam comprises laser ablating metal from the site. In the disclosed embodiment, if the defect includes a crevice in the conductive trace, the step of removing the metal includes preforming the edge of the conductive trace adjacent the crevice. In one embodiment, pre-shaping the edges includes ablating the conductive traces, optionally by forming a step slope in the conductive traces to tilt the edges of the conductive traces toward the crevice. Including.

  Additionally or alternatively, pre-shaping the edges may include ablating trenches in the conductive traces to promote droplet deposition on the conductive traces.

  In some embodiments, directing the pulse of laser radiation comprises depositing a droplet on the conductive trace so as to extend above the pre-shaped edge. Additionally or alternatively, the step of directing a pulse of laser radiation includes depositing a droplet on the conductive trace to form a patch in the defect site that matches the profile of the conductive trace.

  In another embodiment, directing the laser beam comprises scanning the laser beam over the substrate of the printed circuit board to roughen the substrate near the site, thereby facilitating droplet deposition on the substrate. including. In one embodiment, scanning the laser beam includes forming a pattern of holes in the substrate, which pattern may be non-linear.

  In the disclosed embodiments, directing the laser beam includes ablating the oxide layer from the conductive trace in the vicinity of the site using the laser beam to facilitate deposition of droplets on the conductive trace.

  Additionally or alternatively, repairing the defect comprises forming a patch in the conductive trace and the method comprises, after repairing the defect, directing a laser beam to post-process the patch. .

  Further, according to embodiments of the present invention, there is provided a method of circuit repair including identifying defective sites within a conductive trace on a printed circuit board. A transparent donor substrate having opposing first and second surfaces and a donor film including a metal formed on the second surface is in proximity to the printed circuit board and the second surface is a printed circuit board. Positioned towards. The first pulse of laser radiation passes through the first surface of the donor substrate and impinges on the donor film to induce the ejection of a first droplet from the donor film onto the site of the defect on the printed circuit board. Is directed. The first pulse has a first pulse energy selected to promote deposition of droplets on the substrate of the printed circuit board, thereby forming an initial metal layer on the substrate at the site. A second pulse of laser radiation, with a second pulse energy greater than the first pulse energy, passes through the first surface of the donor substrate and impinges on the donor film to produce a second pulse from the donor film to the initial metal layer. It is directed to induce the ejection of droplets, thereby repairing defects.

  In one embodiment, the method includes, after the step of directing the second pulse, directing a laser beam to remelt the droplet so as to anneal the metal repairing the defect. Additionally or alternatively, the method includes directing a laser beam to heat a second droplet that flies between the donor film and the printed circuit board.

  Further, according to embodiments of the present invention, there is provided a method of circuit repair including identifying a site of a defect in a conductive wiring having a first metallic material on a printed circuit board. A transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface and having a higher galvanic potential than the first metal material and having a second metal material. , Proximate to the site of the defect, with the second side facing the printed circuit board. A pulse of laser radiation passes through the first surface of the donor substrate and impinges on the donor film to induce the ejection of droplets of the second metallic material from the donor film onto the site of the defect on the printed circuit board. And is thereby directed to repair defects and prevent galvanic corrosion.

  In one embodiment, the first metallic material comprises copper and the second metallic material comprises a copper alloy.

  Additionally or alternatively, the method includes depositing a sacrificial metal layer on the second metallic material at the site of the defect, the sacrificial metallic layer having a lower galvanic potential than the second metallic material.

  Further, according to embodiments of the present invention, a method of circuit repair is provided that includes identifying defects in conductive traces on a printed circuit board. A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is provided on a printed circuit board having a second surface adjacent to a defect site. Positioned towards. A pulse of laser radiation passes through the first surface of the donor substrate and impinges on the donor film, inducing the ejection of droplets from the donor film onto the defect sites on the printed circuit board, thereby causing the metal patch to rupture. Oriented to form and repair defects. After the step of forming the metal patch, a laser beam is directed to post-treat the site of defects.

  Typically, the conductive traces have a predetermined three-dimensional (3D) profile, and directing the laser beam includes ablating material from the site to match the patch with the 3D profile of the conductive traces. In one embodiment, the ablating material comprises a first laser pulse at a first energy level selected to oxidize the surface of the patch and a first energy level selected to remove the oxidized surface. A second laser pulse having a second energy level greater than, and alternatingly and sequentially to remove material from the patch. Additionally or alternatively, directing the laser beam includes forming a 3D image of the patch to monitor the shape of the patch before and after ablating the material.

  In the disclosed embodiment, the step of directing a pulse of laser radiation comprises forming the patch to have a second lateral dimension that is greater than a corresponding first lateral dimension of the conductive trace, the material comprising: The step of ablating includes reducing the second lateral dimension of the patch. The second lateral dimension includes at least one of a height dimension and a width dimension.

  Additionally or alternatively, directing the laser beam includes applying a laser pulse to anneal the metal patch.

  According to embodiments of the present invention, a method of circuit repair is provided that includes identifying defects in conductive traces on a printed circuit board. A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is proximate the target area and the second surface is a printed circuit board. Positioned towards. A pulse of laser radiation passes through the first surface of the donor substrate and impinges on the donor film to induce the emission of a two dimensional array of droplets from the donor film onto the printed circuit board, thereby exposing the target area. Oriented to cover.

  Usually, the step of directing a pulse of laser radiation comprises controlling the thickness of the area of the target area by setting the spatial density of the droplets in the array.

  In the disclosed embodiment, directing the pulse of laser radiation comprises printing a droplet on a target area in a hexagonal pattern.

Further, according to embodiments of the present invention, there is provided an apparatus for material deposition that includes a transparent donor substrate having opposing first and second sides and a donor film formed on the second side. The donor film has a thickness δ and a thermal diffusivity α and is characterized by a thermal diffusion time τ = (δ ² / 4α). The positioning assembly is configured to position the donor substrate proximate the acceptor substrate with the second side facing the acceptor substrate. The optical assembly directs a pulse of laser radiation having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film, through the first surface of the donor substrate, impinges on the donor film, and deposits the donor film on the acceptor substrate. Configured to induce ejection of a droplet of molten material from the.

  Further, according to embodiments of the present invention, there is provided an apparatus for material deposition that includes a transparent donor substrate having opposing first and second sides and a donor film formed on the second side. The donor film contains a metal. The positioning assembly is configured to position the donor substrate proximate the acceptor substrate with the second side facing the acceptor substrate and providing a gap of at least 0.1 mm between the donor film and the acceptor substrate. The optical assembly directs a pulse of laser radiation through the first side of the donor substrate and impinges on the donor film to induce the ejection of a metal droplet from the donor film through the gap on the acceptor substrate. Configured to do.

  Further, according to embodiments of the present invention, there is provided an apparatus for circuit repair including a transparent donor substrate having opposing first and second surfaces and a donor film including a metal formed on the second surface. It The positioning assembly is configured to position the donor substrate proximate the site of the defect in the conductive traces on the printed circuit board with the second side facing the printed circuit board. The optics assembly directs a laser beam to impinge on a site of a defect on a printed circuit board to pre-treat the site and then directs a pulse of laser radiation through a first side of the donor substrate, It is configured to impinge on the donor film to induce the ejection of droplets from the donor film onto the defect sites on the printed circuit board, thereby repairing the defect.

  Further, according to embodiments of the present invention, there is provided an apparatus for circuit repair including a transparent donor substrate having opposing first and second surfaces and a donor film including a metal formed on the second surface. It The positioning assembly is configured to position the donor substrate proximate the printed circuit board with the second side facing the printed circuit board. The optical assembly passes a first pulse of laser radiation through a first side of the donor substrate and impinges on the donor film to deposit a first droplet of the donor film on the site of the defect on the printed circuit board. A first pulse configured to direct the emission is selected to promote deposition of a droplet of the printed circuit board onto the substrate, thereby forming an initial metal layer on the substrate at the site. It has a first pulse energy. The optical assembly impinges a second pulse of laser radiation with a second pulse energy greater than the first pulse energy through the first surface of the donor substrate and onto the donor film, from the donor film to the initial metal layer. Is configured to induce the release of a second droplet of, and thereby direct the repair of the defect.

  Also, according to an embodiment of the present invention, there is provided an apparatus for repairing a defect in a conductive wiring including a first metal material on a printed circuit board. The device is transparent, having first and second opposing surfaces and a donor film having a higher galvanic potential than the first metallic material and having a second metallic material formed on the second surface. Including a donor substrate. The positioning assembly is configured to position the donor substrate proximate the site of the defect with the second side facing the printed circuit board. The optical assembly directs a pulse of laser radiation through the first side of the donor substrate and impinges on the donor film to deposit a second metallic material from the donor film on the site of the defect on the printed circuit board. It is configured to induce droplet ejection, thereby repairing defects and preventing galvanic corrosion.

  Further, according to embodiments of the present invention, there is provided an apparatus for circuit repair including a transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface. To be done. The positioning assembly is configured to position the donor substrate proximate the site of the defect in the conductive traces on the printed circuit board with the second side facing the printed circuit board. The optical assembly directs a pulse of laser radiation through the first side of the donor substrate and impinges on the donor film to induce the ejection of droplets from the donor film onto the defect sites on the printed circuit board. , Thereby forming a metal patch to repair the defect, and further, after forming the metal patch, is configured to direct a laser beam to post-process the site of the defect.

  Further, according to embodiments of the present invention, there is provided an apparatus for repairing defects in conductive wiring on a printed circuit board. The device includes a transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface. The positioning assembly is configured to position the donor substrate proximate the target area with the second side facing the printed circuit board. The optical assembly directs a pulse of laser radiation through a first side of the donor substrate and impinges on the donor film to induce emission of a two dimensional array of droplets from the donor film onto the printed circuit board. , Thereby configured to cover the target area.

  The invention will be more fully understood from the following detailed description of the embodiments in conjunction with the drawings.

1 is a schematic diagram of a system for repairing an electric circuit according to an embodiment of the present invention. 2 is a schematic side view showing details of the system of FIG. 1 according to an embodiment of the invention. FIG. 4 is a flow chart that schematically illustrates a process of electrical circuit repair, according to an embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a defect site in a printed circuit prepared for repair according to an embodiment of the present invention. FIG. 6 is a schematic view of a defect site in a printed circuit prepared for repair, according to another embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a defect site in a printed circuit prepared for repair, according to yet another embodiment of the invention. FIG. 6 is a schematic top view of a defect site in a printed circuit prepared for repair, according to a further embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a defect site in a printed circuit after preparation and repair according to an embodiment of the present invention. FIG. 6 is a schematic top view of a laser beam scanning pattern used in preparing defect sites for repair, according to an embodiment of the invention. FIG. 6 is a schematic top view of a pattern of holes created in a region of a defect site that prepares a site for repair, according to an embodiment of the invention. FIG. 6 is a schematic top view of a pattern of holes created in a region of a defect site that prepares a site for repair, according to an embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a defective site in a printed circuit showing LIFT driven ejection of metal droplets toward the site according to an embodiment of the invention. FIG. 6 is a schematic diagram of a donor film after LIFT driven release of metal droplets, according to an embodiment of the invention. FIG. 6 is a schematic cross-sectional view showing a stage in deposition of metal droplets on a substrate according to the embodiment of the present invention. FIG. 6 is a schematic diagram of sites on a substrate showing successive stages in the deposition of a pattern of metal droplets on the substrate according to an embodiment of the invention. FIG. 6 is a schematic diagram of sites on a substrate showing successive stages in the deposition of a pattern of metal droplets on the substrate according to an embodiment of the invention. FIG. 6 is a schematic diagram of sites on a substrate showing successive stages in the deposition of a pattern of metal droplets on the substrate according to an embodiment of the invention.

  [Overview]

  As printed circuit boards become denser with thinner, more dense conductive wiring, it becomes increasingly difficult to repair defects in the wiring. LIFT holds promise, at least in theory, as a method that can be used to efficiently repair in these difficult situations. However, no actual LIFT system has been developed and deployed yet with the appropriate functionality for printed circuit repair on the factory floor.

  The embodiments of the invention described below provide methods and apparatus that enhance the power and utility of LIFT. The enhanced functionality provided by these embodiments is particularly useful for repairing defects in conductive traces on printed circuit boards due to the ejection of metal droplets from the LIFT donor film. While the invention is not limited to this particular application context, aspects of the embodiments described herein include, mutatis mutandis, the printing of both metallic and non-metallic materials, It may be applied to LIFT-based printing on other types of acceptor substrates.

  In metal-printed LIFT-based systems known in the art, a high energy laser pulse impinging on a donor film causes a spray of tiny metal droplets to emerge from the film. To use such a system to print very fine features (such as repairing defects in printed circuit wiring), hold the donor substrate in close proximity to the acceptor substrate, typically less than 50 μm. There is a need to. This very small donor-acceptor distance creates some practical difficulties in aligning and controlling the system to perform the actual repair.

  Some embodiments of the present invention overcome this difficulty by operating in a new domain of different laser pulse energy and duration. In particular, the disclosed embodiments use short laser pulses of less than 5 nanoseconds, typically less than 2 nanoseconds and often less than 1 nanosecond. The thickness of the donor film, the pulse energy, and the laser spot size on the donor film are selected with a short pulse time, and each laser pulse generally directs a single drop of donor material directly in front of the surface of the donor substrate. It is emitted only with a small angle deviation (normally about 5 mrad or less) with respect to the normal line to. As a result, reliable and accurate operation can be achieved with a donor substrate relatively distant from the acceptor substrate, with a gap between the donor and acceptor substrate of at least 100 μm, typically at least 200 μm or even 300 μm or more.

The principle of these embodiments is that the pulse width of the laser beam is roughly comparable to the diffusion time of heat through the donor film. As a result, droplets are produced and ejected at a controlled temperature that is believed to be below the droplet temperature in most LIFT systems known in the art. In particular, for a donor film having a thickness δ and a thermal diffusivity α, the unique thermal diffusion time is given by τ = (δ ² / 4α). The donor substrate is arranged close to the acceptor substrate with the surface on which the donor film is formed facing the acceptor substrate. A pulse of laser radiation having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film, and perhaps equal to or less than the thermal diffusion time, is directed through the outer surface of the donor substrate to impinge on the donor film. These short pulses induce a controlled release of molten material droplets from the donor film onto the acceptor substrate.

  We find that focusing the laser beam loosely on the donor film with a beam spot size that is at least 10 times the donor film thickness δ induces the desired well-controlled emission of a single droplet. It was also found to be useful for In some cases, the spot size may be 20 times or more, and even 40 times or more, the thickness of the donor film.

  The inventors have found that LIFT-based repair using the techniques described herein works well even under normal atmospheric conditions and does not require the repair to be performed under inert conditions or in vacuum. It was Such repair results in good conductivity through the patch without substantially oxidizing the repair material.

  In some embodiments of the present invention, after identifying a defect in a conductive trace on a printed circuit board, and before a LIFT process is applied to repair the defect, the laser beam emits a site of defects on the printed circuit board. Is directed to pretreat. The beams used in the pre-processing may be generated by the same laser (though having different beam parameters) or different lasers used in the LIFT process.

  Many pretreatment techniques are disclosed in the description that follows. These pre-processing techniques may be optimally applied in connection with the new LIFT technique described above. However, they may alternatively be used in connection with other LIFT-based methods known in the art. In certain embodiments, a laser beam is typically used to preform the edges of the conductive traces adjacent the crevices by ablating the conductive traces, thereby tilting the edges of the conductive traces toward the crevices. You may be taken. The term "slope" in this context refers not only to continuous slopes, but also to step slopes such as stair structures.

  Additionally or alternatively, the trench may be removed in the conductive trace adjacent to the defect to promote the attachment of droplets to the conductive trace. Since such penetration tends to result in corrosion that weakens the patch, the trench suppresses the etchant used in the processing steps that follow penetration between the original metal and the repair patch of the added metal, You may lay out conveniently.

  Additionally or alternatively, the laser beam may scan over the substrate of the printed circuit board to roughen the substrate in the vicinity of the repair site, thereby facilitating droplet deposition on the substrate. . Generally, the laser beam produces a well-defined pattern of either trenches or holes in the surface having a depth and size selected to capture and immobilize metal droplets that strike the surface. The density of the pattern is usually selected based on the material properties of the substrate and donor film to provide sufficient adhesion to meet manufacturing test standards and application requirements. In some embodiments, the holes are created in a non-linear pattern selected to inhibit the penetration of corrosive etchants.

  As a separate pretreatment step, a laser beam may be used to remove the oxide layer that normally forms on the conductive traces to promote the deposition of droplets on the conductive traces.

  When repairing an open circuit defect on a printed circuit board, the initial metal droplets ejected from the donor film always adhere to the dielectric substrate. While roughening the substrate as described above can promote adhesion, we find that droplets with high thermal energy (ie, high temperature) tend to bounce and scatter when they hit the substrate. I found that. Therefore, in some embodiments of the invention, in order to reduce scattering and overcome this problem, the initial pulse of laser radiation in the LIFT process is such that the initial droplet reaches the substrate with a minimal amount of excess thermal energy. To a relatively low pulse energy selected to. These droplets tend to set immediately. Here, they rest on the substrate at the site and form the initial metal layer.

  Subsequent laser pulses may desirably have high pulse energies, as the droplets they form readily adhere to the initial metal layer and build up the layer to repair defects. The hotter droplets formed at higher energies are, in fact, advantageous for forming an integrated solid mass that tends to be more mechanically and chemically more stable than the set of hardened droplets. Integration of the droplets into the solid mass can be facilitated after the deposition of the droplets by directing a laser beam to remelt the droplet and anneal the metal.

  Additionally or alternatively, additional laser heating may be used during the deposition step (after the initial metal layer is deposited on the substrate) to heat the droplets flying between the donor film and the printed circuit board. This heating can be performed with an additional laser or with the same laser used to generate the droplets. In the latter case, when the beam is shaped to provide at least two pulses in time, the first induces a drop ejection and the second heats the ejected droplet (tens to hundreds). With typical delays between pulses on the order of nanoseconds).

  A further problem that the inventors have noticed in LIFT-based repair of metal lines is galvanic corrosion of the metal in the repair patch. To avoid this problem, in embodiments of the present invention, the donor film used for repair comprises a metal composition that is different from the material of the interconnect being repaired. In particular, the metallic material in the donor film is selected to have a higher galvanic potential than the wiring. For example, copper alloys with small amounts of another metal, usually a noble metal such as gold, silver, or platinum, added to repair copper wiring can be used as a LIFT donor.

  The additional embodiments of the invention described below typically provide post-processing steps that are applied after the LIFT-based repair steps are complete. These steps are directed, for example, to improve the stability and corrosion resistance of the metal patch, as well as to remove unwanted excess material outside the volume of the patch.

  The techniques outlined above and further described below may be optimally used in combination to accurately, conveniently, and reliably repair defects in printed circuit wiring. Alternatively, each of these techniques may be used individually or in selected sub-combinations to facilitate LIFT-based repair performed using other systems and methods. Moreover, at least some of these techniques may be used in other applications, such as LIFT-based printing of two- or three-dimensional structures on various other types of acceptor substrates.

  [System description]

  FIG. 1 is a schematic diagram of a system for repairing an electric circuit according to an embodiment of the present invention. This system is similar in design to the system described in the above-referenced US patent application Ser. No. 13 / 146,200, but with various improvements as described herein. This system and its components are presented here merely to illustrate the type of environment in which the techniques described herein may be implemented. These techniques may similarly be implemented with other types of suitable equipment and in other configurations.

  The system of FIG. 1 is built around a repair device 20 operating on an electrical circuit, such as a printed circuit board (PCB) 22 held on a mounting surface 24. The terms "printed circuit board" and "PCB" are used herein to generally refer to any type of dielectric substrate on which conductive wiring is deposited, regardless of the type of dielectric and the process used to deposit it. Used. Although the apparatus 20 can be used to repair various types of defects in the PCB 22, the embodiments described below are particularly conductive that are repaired by adding conductive material to the PCB at the appropriate locations. It is directed to repairing defects in missing conductors, such as crevices 42 in wiring 40.

  The apparatus 20 comprises an optics assembly 26 including lasers and optics suitable for associated processing on the LIFT and PCB 22, as shown in more detail in FIG. (Alternatively, the laser may be included in a separation unit, not shown, with suitable optical connections to assembly 26.) Typically, the optical assembly will be on PCB 22 before, during, and after repair. It also has an inspection optical system (not shown) for forming a magnified image of the defect site. A positioning assembly in the form of a bridge 28 positions the optical assembly 26 above the defect site on the PCB 22 by linear movement along the axis of the device 20. The control unit 30 controls the operation of the optics and positioning assembly to perform the necessary inspection and repair operations as described below.

  The control unit 30 typically communicates with an operator terminal 32 which comprises a general purpose computer including a processor 34 and a display 36 along with a suitable user interface and software. Defects found on the PCB 22, such as crevices 42 in the wiring 40, as shown in the inset 38, may be displayed on the display 36. Each site 44 of such defects is identified by the processor 34. Processor 34 develops a repair plan that includes pre-processing, LIFT, and post-processing steps to be applied at each such site 44, typically performed by device 20 as described herein. The steps of defect identification and repair planning may be performed automatically by the processor 34, manually under operator control, or most typically by a combination of automatic and manual steps. As the device 20 executes the plan, the resulting defects 44 are filled with metal repair patches 46 produced by LIFT.

  FIG. 2 is a schematic side view showing details of the device 20, in particular the optical assembly 26, according to an embodiment of the invention. The laser 50 emits pulsed light focused by a suitable optical system 52. The laser may comprise, for example, a pulsed Nd: YAG laser with a doubled frequency output allowing a pulse amplitude and duration conveniently controlled by the control unit 30. The optics 52 is similarly controllable to adjust the position and size of the focal spot formed by the laser beam. Therefore, with proper adjustment of the laser and optical parameters, the same laser 50 can be used for some or all of the pre-treatment, LIFT, post-treatment steps.

  Alternatively, additional lasers (not shown) with different beam characteristics may be used for some of these steps. Such additional lasers, if used, preferably operate at the same wavelength as laser 50 to simplify the optical setup.

  Optical assembly 26 is shown in FIG. 2 in a LIFT configuration. The optics 52 focuses the beam from the laser 50 onto a donor sheet 54 that comprises a donor substrate 56 having a donor film 58. Substrate 56 typically comprises a transparent optical material such as a glass or plastic sheet, and for repair of wiring 42, film 58 is a suitable metal such as copper or a copper alloy having a film thickness of about 1 μm. With material. The beam from the laser 50 is aligned (by the motion assembly 28) to the site of the defect 42, and the donor sheet 54 is positioned above the site with the desired gap width D from the substrate 41 of the PCB 22. Typically, as mentioned above, this gap width is at least 0.1 mm, and the inventors, subject to proper selection of laser beam parameters as described below, have a width of 0.2 mm or even 0. It has been found that a gap width of 0.5 mm or larger can be used. Optics 52 focuses the laser beam through the outer surface of substrate 56 onto film 58, causing droplets of molten metal to exit the film and across the gap onto PCB 22. This LIFT process is described in more detail below with reference to FIGS. 9A, 9B and 10.

  [process flow]

  FIG. 3 is a flow chart that schematically illustrates a process of repairing an electric circuit according to an embodiment of the present invention. Although the process is described with reference to the components of the device 20 and the PCB 22 for clarity, the steps of the process may be performed similarly in other application environments, mutatis mutandis, as described above. Can be done.

  In the process of FIG. 3, the defect sites 44 are first pretreated in a pretreatment stage 60 to increase the efficiency of the subsequent metal printing stage 62. Pre-processing stage 60 may include several processes, including one or more of the following.

  Conductor preforming step 66 in which the conductive material is removed from the area to be repaired. Typically, the edges of the interconnect 40 near the defect 42 will facilitate the attachment of the metal patch to existing conductors (particularly the added patch from etching away by the corrosive chemistries used in subsequent processing steps). (From a protection point of view), and to match the patch to the original profile of the repaired wire. Additionally or alternatively, excess metal associated with defects, such as deformation of wiring 40, may be removed at this stage. Step 66 is described in more detail below with reference to FIGS. 4A, 4B, 5 and 6.

  Substrate preparation step 68 in which the substrate 41 in the vicinity of the defect site 44 is processed to promote deposition of metal droplets onto the substrate. It is beneficial to roughen the laminar substrate in this step, ie to create holes and / or trenches in the substrate that increase the surface area to which the droplets adhere. Step 68 is described in more detail below with reference to FIGS. 8A-8C.

Typically, the oxide layer (such as copper oxide) that forms over the surface of the interconnect 40 over time is removed to promote adhesion of metal droplets to the existing interconnect, an oxide removal step 70. The inventors can quickly and efficiently remove the copper oxide layer by controlling the laser 50 to emit a pulse having a fluence (F) on the order of 1 J / cm ² on the wiring 40. Found. (In the present description and claims, the spot diameter is specified using a 4σ width, assuming a Gaussian laser beam, and the calculated fluence value indicates the pulse energy divided by the spot diameter.)

  Once the defect sites have been prepared, the device 20 is operated in the configuration shown in FIG. 2 to perform the actual repair in the printing stage 62. This stage is specifically shown in FIGS. 9A, 9B, and 10.

  After the crevice 42 has been filled with the patch 46 in stage 62, many additional steps may be performed in post-treatment stage 64 to increase the robustness of the repair. Typically, the repair site need not be as strong as the original metal wiring 40, and thus is more susceptible to damage during subsequent PCB 22 assembly steps and use of the PCB. To reduce such susceptibility to damage, stage 64 may include several processes including one or more of the following steps.

  A cleaning step 72 in which the laser 50 removes excess material from the substrate 41, trims the repair patch 46, and removes debris accumulated on the surrounding surface.

  A patch leveling step 73 where the laser 50 removes material from the patch 46 to bring the patch into line with the original PCB design rules.

  A local annealing step 74 in which the laser 50 remelts the metal droplets within the patch 46 to smooth and homogenize the patch, and in particular its outer surface.

  A layer printing step 76 in which an additional sacrificial layer is deposited on the patch 46.

  The rationale for these steps and details of their implementation are given below, especially in the section "Post-processing of repair sites".

  [Pre-processing of repair site]

  FIG. 4A is a schematic cross-sectional view of a defect site in a printed circuit prepared for repair, according to an embodiment of the invention. This embodiment describes the problem discovered by the inventors. Applying LIFT to repair the crevice 42 in the wire 40 tends to form microvoids in the printed metal inside the sharp corners of the cut wire. These microvoids impair the quality of repair, introduce parasitic capacitance, and weaken the metal integrity as the etchant penetrates the voids during the next etching step. Therefore, in step 66, the laser 50 is applied to remove the wire 40 and tilt the edge of the wire toward the crevice.

  As a practical matter, it is difficult to ablate a continuous slope, but the inventors have found that an equal effect can be achieved by ablating a step slope 80 as shown in FIG. 4A. Generally, prominent microvoids can occur at step heights of 10 μm or higher. Therefore, it is desirable that the steps in the slope 80 have a height lower than 10 μm. The inventors have found that the 7 μm step gives good results. To produce the desired step, the optics 52 is typically adjusted to provide a spot diameter on the wire 40 of about 5 μm.

  FIG. 4B is a schematic illustration of defect sites in a printed circuit prepared for repair, according to another embodiment of the invention. This embodiment is similar to FIG. 4A, except that in this example, the crevice 42 is between the wire 40 and the wide pad 82. In this case, the pad 82 is removed in step 66, creating a stair slope 84 that opens in two dimensions. Alternative slope configurations for the purpose of step 66 will be apparent to those skilled in the art and are considered to be within the scope of the present invention.

  Usually, the wiring in the PCB is formed in a plurality of continuous layers alternately with the stack of dielectric substrates. The repair described herein can be performed on any layer of the conductor before the next layer of dielectric is overlaid. However, a "soft etch" process is commonly applied to clean the surface of the PCB prior to overlaying the dielectric. The inventors have found that this soft etch tends to undercut metal patches just formed at the interface between the patch and existing wiring, thereby weakening the adhesion between the patch and wiring. Many possible solutions to this problem are described below.

  FIG. 5 is a schematic cross-sectional view of a defect site in a printed circuit prepared for repair, according to an embodiment of the invention. In this case, the stair slope 80 has been expanded by adding a wider upper step 86. As a result, even if some undercuts occur as a result of soft etching, the contact area between the patch 46 and the wiring 40 is still sufficient to ensure good adhesion.

  FIG. 6 is a schematic top view of defect sites in a printed circuit prepared for repair, according to yet another embodiment of the invention. In this case, the laser 50 is operated to remove the trenches 88, 90 in the top surface of the wiring 40. These trenches increase the contact area between the printed metal of the patch and the underlying wiring, thereby promoting adhesion. The trenches may be located along the length of the wire, across the wire, or both as shown in FIG. (The combination of the two wiring directions shown in the figure is particularly useful for preventing penetration of the etchant directly under the sides of the patch.) The inventors have set the laser 50 at 3-4 μJ per pulse. By working and focusing the laser beam on the surface of the wiring 40 to a spot diameter of 5-9 μm, good results have been obtained for producing such trenches. Alternatively, the pattern of holes can be used for similar purposes, as shown, for example, in FIGS. 8B and 8C.

  FIG. 7 is a schematic cross-sectional view of a defect site in a printed circuit after preparation and repair according to an embodiment of the present invention. This figure is not really relevant to step 68 as it shows defects after deposition of patch 46 in printing stage 62. Nevertheless, it is shown here because it provides a further solution to the problem of weakened patch adhesion following soft etching. In this case, a molten metal droplet is deposited on the wire 40 in step 62, thereby causing the patch 46 to extend over the preformed edge of the wire. As a result, the patch edge 92 projects above the top of the trace 40, thereby protecting the interface between the patch and trace from undercutting. This solution can be used by itself or in combination with the pretreatment solution described above.

  Alternatively, patch 46 may be printed to exactly match the dimensional profile of trace 40 without the addition of edge 92. If necessary, any excess metal may be removed at step 73, as described further below.

  FIG. 8A is a schematic top view of laser beam scanning patterns 100, 102 used in preparing defect sites for repair at step 68, according to an embodiment of the invention. The need for step 68 depends on the type of substrate used in the PCB under repair. The roughness of the substrate is useful in enhancing the adhesion of metal droplets to the substrate, and the metal droplets ejected onto the PCB substrate in step 62 may not adhere well if the substrate is too smooth. To alleviate this problem, the beam of laser 50 may be scanned over the substrate to roughen the substrate in the vicinity of the repair site, thereby promoting droplet attachment to the substrate.

  Any suitable scanning pattern can be used for this purpose. For example, the orthogonal raster patterns 100 and 102 shown in FIG. 8A can be used to form an array of microcavities in a substrate. Proper results are obtained by setting the laser 50 to emit pulses of about 2 μJ with a spot diameter of about 13 μm on the substrate and a pitch of about 20 μm between scan lines. The patterns 100 and 102 preferably extend beyond the actual width of the subsequently formed patch in step 62.

  FIG. 8B is a schematic top view of a pattern 103 of holes 101 created in a region of a defect site that prepares a site for repair, according to an embodiment of the invention. The holes 101 comprise small holes formed in the substrate 41, typically having a depth in the range of 2-8 μm. The laser parameters are typically adjusted so that the diameter of the hole 101 is slightly larger than the expected drop diameter (depending on LIFT conditions), for example in the range 4-10 μm. The distance between adjacent holes is small, typically smaller than the diameter of the holes to provide high hole density within the repair area.

  FIG. 8C is a schematic top view of a pattern 105 of holes 101 created in a region of a defect site, according to an alternative embodiment of the invention. As shown in this figure, the holes 101 need not be laid out on a linear grid, and in fact other layouts are desirable to increase the density of the holes and suppress solvent penetration into the spaces between the holes. . For example, the holes 101 in FIG. 8C are laid out in a generally triangular arrangement with a certain amount of disorder added to the pattern. As a result, the interfacial paths 106 through which the solvent can traverse between the holes are significantly longer and narrower than the uniform paths when the holes are laid out in a linear grid.

  [LIFT print]

FIG. 9A is a schematic cross-sectional view of a defect site 42 showing LIFT driven emission of metal droplets 106 from a donor film 58 towards the site, according to an embodiment of the invention. This figure shows the effect of an illuminated film 58 having a laser pulse whose duration is comparable to the time required for thermal diffusion through the film. As mentioned above, for a donor film having a thickness δ (ie, the vertical dimension in FIG. 9A) and a thermal diffusivity α, the thermal diffusion time through the film is τ = (δ ² / 4α). is there. The thermal diffusivity α of copper is about 1 cm ² / sec, and τ is about 0.25 nanosecond for a copper film with a thickness δ = 1 μm.

  Metal droplet LIFT printing techniques known in the art typically use laser pulse times of at least 10 nanoseconds with donor metal films of thickness less than about 200 nm. In this region, the pulse width is many times longer than the thermal diffusion time, resulting in the formation of an extended melt region (melt pool) in the film that has ejection characteristics similar to a viscous liquid layer. In this case, many small droplets are ejected with poor directionality. Both the donor and acceptor must be placed in close proximity in order to accurately deposit the droplets in this region.

  On the other hand, in this embodiment, an extremely short laser pulse time is used. Optimally, the pulse time may be limited to less than twice the thermal diffusion time τ, perhaps equal to τ or less. In other words, sub-nanosecond laser pulses are typically used to eject droplets from a copper film with a thickness δ = 1 μm. Alternatively, in some conditions the pulse may be 2 nanoseconds, or in some cases 5 nanoseconds. Laser pulses typically have beam energies in the range of 3-4 μJ. For at least a particular LIFT step, a large laser beam area with a beam diameter of at least 10 times the donor film thickness δ, eg, 20-30 μm, is desirable.

  FIG. 9B is a schematic illustration of donor film 58 after LIFT driven ejection of droplets 106, according to an embodiment of the invention. The selection of laser pulse parameters described above results in a "volcano" pattern 104 in the donor film. This "volcanic eruption" type causes a single droplet 106 to be ejected with high directivity, typically within about 5 mrad of the film surface normal.

  An important consequence of the high directivity of the droplet ejection is that it allows a relatively large gap D between the donor sheet 54 and the acceptor substrate 41 without compromising print accuracy. The donor substrate 56 under these circumstances can be easily positioned with the film 58 at least 0.1 mm away from the acceptor substrate, typically at least 0.2 mm away from the acceptor substrate, or when the laser radiation pulse is a donor. As long as it hits the film, it can be positioned as far as 0.5 mm.

  FIG. 10 is a schematic cross-sectional view illustrating stages in the deposition of metal droplets at defect sites on the substrate 41 according to an embodiment of the present invention. In this embodiment, a thin copper layer 110 is first printed on the dielectric substrate 41 for use as a seed layer. Thereafter, additional metal droplets 112 are deposited on layer 110 until sufficient material has been deposited to repair the defects.

  The first step in FIG. 10 is characterized by droplets of copper that rest and act on the substrate itself (usually a thin organic layer), while in the second step, the droplets are on printed copper that does not directly interact with the substrate. Be listed. Molten metal droplets that rest on the substrate with high thermal energy often bounce off the substrate and rest some distance from the initial target. This bouncing effect results in a large footprint and reduced efficiency in seed layer production. To avoid this effect, in an embodiment of the invention, the laser pulse parameters (energy, pulse time, and beam size) are controlled as described above to have a lowered temperature for later process steps. Large droplets are ejected from the film 58 while creating the initial layer 110 on the substrate 41. Upon hitting the substrate, these large droplets tend to adhere and spread in place rather than bouncing off.

  When this "flared" function, the width and height of layer 110 can be controlled by adjusting the laser pulse energy. The finer the pattern (ie, the narrower the line being repaired), the lower the laser pulse energy used at this stage.

  On the other hand, higher laser pulse energies are desirable to increase both the efficiency and quality of the process in order to build up additional droplet 112 configurations. Higher pulse energies produce hotter droplets that tend to merge into layer 110 and into each other to form more solid masses, rather than growing separate hardened spheres.

Laser radiation is applied to the donor film to create a patch on the target area of the substrate 41 (such as the repair sites in the example above), and a two-dimensional array of droplets covering the target area of the acceptor substrate. To release. The growth rate of the patch thickness as the additional drops 112 are printed depends on the printing scenario and the overlap between the drops. These print parameters also define the porosity or compactness of the print configuration. For example, given a minimum distance D = Dx = Dy between laser spots on the donor film 58, droplet spatial densities are printed along each row or column in the target area on the substrate 41 to produce droplets. Can be defined by an integer k indicating the number of droplets, which is evenly distributed with a spacing dx = dy = D / k. In most practical cases, given the device 20 and the parameter constraints of the LIFT printing process in the device, the dimension D is about 30 μm. The patch thickness h _k added by each layer is a discrete function of integer k. The inventors have generally found that the following relationship holds.

Here, h ₀ is constant and normally varies between 0.1 and 0.5 μm.

Therefore, the thickness of the area of the target area can be controlled by approximately setting the spatial density of the droplets in the array. Therefore, in order to achieve good thickness resolution, it is desirable for k to be as small as possible, while a large value of k achieves a more compact configuration (especially lower resistance at the droplet boundaries). Desirable for. In a normal scenario, given D≈30 μm, the inventors have found that the value of k should be 7 or more. Therefore, the thickness resolution h _k is on the order of 5 μm or more.

  One way to achieve a finer height resolution of the LIFT printed patch, despite this limitation, is to overprint the patch to a higher height than is actually needed and then at leveling step 73. Removing the patch (using the same laser used in printing step 62 or another laser). Excessive height ablation allows achieving a height resolution of less than 1 μm, depending on the laser used for this purpose. Alternatively, local mechanical polishing can be used for this purpose. Additionally or alternatively, device 20 may include a sensor (not shown) that performs three-dimensional measurement of the patch to provide patch height feedback during printing and / or subsequent ablation.

  11A-11C are schematic views of repair site 120 on substrate 124 showing successive stages in the deposition of a pattern of metal droplets at the site, according to an embodiment of the invention. In this embodiment, the droplets 122, 124, 126 are printed on the substrate 124 in a hexagonal honeycomb pattern to fill the patch area in the most compact possible way.

  As in the previous example, a cell of dimension Dx × Dy (which is not necessarily a square in this case) is given above by an integer density k in the X and Y directions (horizontal and vertical directions in FIGS. 11A to 11C). As defined, it is divided by the horizontal and vertical drop spacing dx and dy. A first hexagonal array of droplets 122 having these spacings is printed as shown in FIG. 11A. The optical assembly 26 prints an additional array of droplets 126 that fills part of the gap between the droplets 122 as shown in FIG. 11B, so that the next vector shifts with respect to the repair site 120 ( Or vice versa).

  A further array of droplets 128 is printed by shifting the repair site by the next vector.

  Therefore, all of the gaps between the droplets are filled, as shown in Figure 11C. The shifting may be performed in any desired order and is not necessarily shown in Figures 11A-11C.

  Optionally, the temperature of the droplet 112 striking the layer 110 can be further increased by directing a laser beam to heat the droplet flying between the donor film 58 and the printed circuit board. Using this approach (not shown), the droplet temperature can be raised above the maximum temperature achievable by its own ejection process. The laser beam provides each droplet with additional thermal energy during its flight from the donor film to the acceptor after it has been formed.

  Such extra heating can be achieved, for example, by providing additional laser irradiation in-line with the pulsed laser beam used to eject the droplets. The additional laser beam may continue to heat the metal droplet through the holes in the volcanic pattern 104 formed in the donor film and until it hits the acceptor. The heating of the droplets formed from the donor film and after separation is a pure thermal process, avoiding possible distortion of the mechanical ejection of the droplets from the film. In principle, the droplet can thus be heated to near its evaporation temperature. As a result, the heated droplets, when placed, have sufficient thermal energy to remelt some of the already deposited metal, thereby promoting droplet deposition.

  The additional laser beam used to heat the ejected droplets is either CW or pulse, provided the pulse is long enough to effectively heat the droplet volume without vaporizing its surface. Good. The pulse time should desirably be longer than the thermal diffusion time in the molten metal droplet, but shorter than the droplet flight time from the donor to the acceptor (typically on the order of microseconds).

  In addition to or in place of the droplet heating technique described above, solidification of droplets within repair patch 46 into a single mass can be facilitated in post-treatment stage 64 by annealing the patch at step 74. . A surface that is redissolved with a pulsed laser (typically a pulse of 3-4 μJ and a focal spot diameter on the repair patch in the 5-13 μm range) enhances uniformity, surface smoothness, and overall quality of the metal layer. Make it less susceptible to chemical attack. The longer the duration of the laser pulse, the deeper the remelt will penetrate into the printed metal layer and the more heat will propagate deep into the metal, causing a more complete remelt.

  Alternatively, as described above, if the patch is overprinted at an excessive height and down-trimmed by laser ablation at step 73, then the additional smoothing performed at step 74 is unnecessary. Become. The inventors have found that ablating 3-4 μm from the patch surface has the added benefit of obtaining similar smoothness to that achieved by annealing, especially when operating the ablation laser at high pulse energies.

  A micro-etching step (also referred to as soft etching) is generally performed in PCB fabrication between thin layers of successive layers to remove oxides and promote good contact and good adhesion between layers. To be done. This type of microetching is likewise carried out after a repair session in which metal is added in the gaps as described above. Therefore, it is important that the metal material used for repair be able to withstand the microetching process.

  Microetching is prone to galvanic corrosion at the interface between patch 46 and wire 40. Galvanic corrosion is a process in which the potential difference between two metal parts in contact drives a corrosive electrochemical effect, and when the metal parts are covered by a liquid (they appear to be in microetching). However, this effect is accelerated by the electrolysis process. The area ratio between the two metal parts in question also has a decisive effect on the corrosion rate. Thus, if the small area of the printed metal patch 46 has a much larger potential, slightly lower than the original copper circuit wiring 40, the patch can quickly erode away, perhaps in just a few seconds. Such potential differences can be caused by small amounts of other metal ions in the copper traces of the PCB that can slightly raise the potential of these traces relative to the pure copper droplets used in the repair patch.

  To overcome this problem, donor film 58 may comprise an additional metallic material that has a higher galvanic potential than copper. In other words, the film 58 typically comprises a lightly doped copper alloy sufficient to make it more cathode, to protect the printed patch. Usually, low proportions of the order of 1-2% of noble metals such as silver, gold, or platinum or combinations of such metals are sufficient to provide the desired protection.

  [Post-processing of repair site]

  In addition to or in place of the steps described above, various treatments may be applied at post-treatment stage 64 to protect patch 46 from corrosion and other damage. For example, the annealing step 74, as described above, may be useful in increasing the resistance of the patch to corrosion by reducing the external surface area exposed to chemical attack. By redissolving the droplets on the surface of patch 46, step 74 reduces the interfacial area between the droplets susceptible to corrosion attack.

  Additionally or alternatively, a sacrificial metal layer may be printed over patch 46. This sacrificial layer typically comprises a metal such as tin, which has a lower galvanic potential than copper (or other metal) used to make patches. The sacrificial layer is subsequently etched away during the microetching step, but the underlying patch is protected. An effective sacrificial layer may be a printed pure copper layer, or an anodic copper layer (consisting of copper with low potential metal wiring such as Al, Mg, or other suitable element).

  As mentioned above, step 73 (FIG. 3) levels the (applied) metal patch 46 to match the original PCB design rules to remove excess patch height and / or width. May be applied for. Typically, as a result of step 62, the metal patch has a larger lateral dimension than the wiring 40. This means that the patch is thicker than the original line thickness of wiring 40 in either the vertical or horizontal direction, or both. In step 73, a well-controlled stepwise laser ablation process is used to gradually remove excess metal from the top layer of patch 46 to bring the thickness of the entire patch (transverse direction) close to that of the original wiring 40. Can be brought about.

  The same type of process may be applied in steps 62 and 73 for patch width. The droplets may be printed on the substrate 41 by the laser 50 in step 62 over a width greater than the width of the original line of wiring 40. Then, in step 73, the laser removes excess material from the sides of the patch as well as the top. This ablation also achieves the desired effect of flattening the sides of the patch, thereby increasing its uniformity and reducing its vulnerability to chemical attack, as described above.

  Excess metal can be removed at step 73 in an iterative two-step process in which the laser is operated at different energy levels. In the first step, the laser emits a low energy pulse sufficient to cause oxidation but insufficient to ablate the surface of patch 46. In the second step, the laser emits a high energy pulse that removes the oxide layer formed in the first step. These two steps are iteratively repeated until the desired amount of material has been removed.

  Step 73 may be performed in connection with in-line 3D imaging to facilitate 3D shaping of patch 46 and bring it to the original 3D shape of trace 40. The same optical objective lens used to focus the laser beam can be used to acquire the 3D image information. In particular, by taking several images, the depth information can be extracted to recover the 3D configuration with the focus of the objective lens being slightly shifted from image to image.

  It will be understood that the embodiments described above are cited by way of example, and that the invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, variations and modifications not disclosed in the prior art that will occur to those of ordinary skill in the art upon reading the above description.

  It will be understood that the embodiments described above are cited by way of example, and that the invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, variations and modifications not disclosed in the prior art that will occur to those of ordinary skill in the art upon reading the above description.
According to the present specification, the configurations described in the following items are also disclosed.
[Item 1]
A method of material deposition, comprising:
Providing a transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface, the donor film having a thickness δ and a thermal diffusivity α , Thermal diffusion time τ = (δ ^Two / 4α), characterized by
Positioning the donor substrate in proximity to the acceptor substrate with the second surface facing the acceptor substrate;
Directing a plurality of pulses of laser radiation (a plurality of laser pulses) having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film, passing through the first surface of the donor substrate, the donor film Impinging on to induce ejection of a plurality of droplets of molten material from the donor film onto the acceptor substrate;
A method comprising.
[Item 2]
The method of item 1, wherein the donor film comprises a metal.
[Item 3]
The method according to item 2, wherein δ ≦ 1 μm and the pulse time of the plurality of laser pulses is less than 5 nanoseconds.
[Item 4]
4. The method of item 3, wherein the pulse time of the plurality of laser pulses is less than 2 nanoseconds.
[Item 5]
Directing the plurality of pulses directs a plurality of first pulses of the laser radiation at a first pulse energy selected to promote attachment of the plurality of droplets to the acceptor substrate, whereby Following the step of directing a plurality of second pulses of laser radiation, an initial metal layer is formed on the acceptor substrate with a second pulse energy that is greater than the first pulse energy, and the plurality of droplets are 5. A method according to any one of items 2 to 4, comprising stacking the metal on top of an initial metal layer.
[Item 6]
Item 2. The acceptor substrate is a printed circuit board, and directing the plurality of pulses includes inducing deposition of the metal to repair defects in conductive traces on the printed circuit board. 6. The method according to any one of items 5 to 5.
[Item 7]
7. The method of any one of items 1-6, wherein the pulse time is less than or equal to the thermal diffusion time of the donor film.
[Item 8]
Any of Items 1-7, wherein the donor substrate is positioned with the second surface at least 0.1 mm from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. The method described in paragraph 1.
[Item 9]
9. The method of item 8, wherein the donor substrate is positioned on the second surface at least 0.2 mm from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. .
[Item 10]
The step of directing the plurality of pulses focuses the laser radiation to impinge on the donor film with a beam spot size that is at least 10 times the thickness δ of the donor film. The method described in the section.
[Item 11]
Item directing the plurality of pulses of laser radiation comprises applying the laser radiation to the donor film to cause the emission of an array of droplets covering a target area of the acceptor substrate. 11. The method according to any one of 1 to 10.
[Item 12]
A method of material deposition, comprising:
Providing a transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface, the donor film comprising a metal;
Positioning the donor substrate close to the acceptor substrate with the second surface facing the acceptor substrate with a gap of at least 0.1 mm between the donor film and the acceptor substrate;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate, impinging on the donor film and onto the acceptor substrate through the gap, the metal from the donor film. Inducing the release of multiple droplets of
A method comprising.
[Item 13]
13. The method of item 12, wherein the gap between the donor film and the acceptor substrate is at least 0.5 mm and the plurality of pulses of laser radiation impinge on the donor film.
[Item 14]
The acceptor substrate is a printed circuit board, and directing the plurality of pulses includes inducing deposition of the metal to repair defects in conductive traces on the printed circuit board. The method described.
[Item 15]
A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
Directing a laser beam to pre-treat the defect sites on the printed circuit board;
After pretreatment of the sites, a transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface is placed in proximity to the sites of the defect. Positioning the second surface towards the printed circuit board,
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film to cause a plurality of melts from the donor film to the sites on the printed circuit board. Inducing a drop ejection, thereby repairing the defect;
A method comprising.
[Item 16]
16. The method of item 15, wherein directing the laser beam comprises removing metal from the site by laser ablation.
[Item 17]
17. The method of claim 16, wherein the defects include crevices in the conductive traces and removing the metal comprises preforming edges of the conductive traces adjacent the crevices.
[Item 18]
18. The method of claim 17, wherein pre-shaping the edges includes ablating the conductive traces such that the conductive traces are tilted toward the crevices.
[Item 19]
19. The method of item 18, wherein ablating the conductive trace includes forming a step slope in the conductive trace.
[Item 20]
Preshaping the edge includes ablating a plurality of trenches in the conductive trace to promote deposition of the droplets on the conductive trace. The method described in the section.
[Item 21]
Item directing the plurality of pulses of the laser radiation comprises depositing the plurality of droplets on the conductive traces so as to extend above the preformed edges. 21. The method according to any one of items 20 to 20.
[Item 22]
Directing the plurality of pulses of the laser radiation includes depositing the plurality of droplets on the conductive trace to form a patch in the site that matches a profile of the conductive trace. 22. The method according to any one of 17 to 21.
[Item 23]
The step of directing the laser beam directs the laser beam onto a substrate of the printed circuit board to roughen the substrate near the site, thereby facilitating deposition of the plurality of droplets onto the substrate. 23. A method according to any one of items 15 to 22, scanning.
[Item 24]
24. The method of item 23, wherein scanning the laser beam comprises forming a pattern of holes in the substrate.
[Item 25]
25. The method of item 24, wherein the pattern of the plurality of holes is non-linear.
[Item 26]
The step of directing the laser beam includes ablating the oxide layer from the conductive wiring in the vicinity of the site using the laser beam to promote deposition of the droplets on the conductive wiring. The method according to any one of Items 15 to 25.
[Item 27]
Repairing the defect includes forming a patch in the conductive line, and the method comprises, after repairing the defect, directing the laser beam to post-process the patch. 27. The method according to any one of Items 15 to 26.
[Item 28]
A method of circuit repair,
Identifying sites of defects within the conductive traces on the printed circuit board;
A transparent donor substrate having first and second opposing surfaces and a donor film containing a metal formed on the second surface is disposed adjacent to the printed circuit board, and the second surface is disposed on the transparent substrate. Positioning towards the printed circuit board,
A plurality of first pulses of laser radiation are passed through the first surface of the donor substrate and impinge on the donor film to cause the donor film to project onto the sites of the defect on the printed circuit board. Directing the ejection of a plurality of first droplets, the plurality of first pulses promoting attachment of the plurality of first droplets to a substrate of the printed circuit board, Thereby having a first pulse energy selected to form an initial metal layer on the substrate at the site, and
Directing a plurality of second pulses of the laser radiation, the second pulse energy being greater than the first pulse energy, passing through the first surface of the donor substrate and impinging on the donor film; Inducing the release of a plurality of second droplets from the donor film to the initial metal layer, thereby repairing the defect.
A method comprising.
[Item 29]
The donor substrate is positioned with the second surface at least 0.1 mm away from the printed circuit board, and the plurality of first pulses and the plurality of second pulses of laser radiation are disposed on the donor substrate. 29. The method of item 28, wherein the method comprises impinging on a film.
[Item 30]
Item 28, comprising directing a laser beam to remelt the plurality of second droplets to anneal the metal that repairs the defects after directing the plurality of second pulses. 29. The method according to 29.
[Item 31]
31. A method according to any one of items 28 to 30, comprising directing a laser beam to heat the plurality of second droplets flying between the donor film and the printed circuit board.
[Item 32]
A method of circuit repair,
Identifying sites of defects in a conductive trace having a first metallic material on a printed circuit board;
A transparent donor having opposing first and second surfaces and a donor film formed on the second surface and having a higher galvanic potential than the first metallic material and having a second metallic material. Positioning the substrate proximate the site of the defect with the second side facing the printed circuit board;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film from the donor film onto the sites of the defect on the printed circuit board. Inducing the release of a plurality of droplets of the second metallic material, thereby repairing the defects and preventing galvanic corrosion.
A method comprising.
[Item 33]
33. The method of item 32, wherein the first metallic material comprises copper and the second metallic material comprises a copper alloy.
[Item 34]
Item 34 or 33, comprising depositing a sacrificial metal layer over the second metallic material at the sites of the defect, the sacrificial metallic layer having a lower galvanic potential than the second metallic material. Method.
[Item 35]
A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is provided on the second surface in proximity to the defect site. Positioning towards the printed circuit board;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film from the donor film onto the sites of the defect on the printed circuit board. Inducing the release of a plurality of droplets, thereby forming a metal patch to repair the defect.
Directing a laser beam to post-treat the sites of the defect after forming the metal patch;
A method comprising.
[Item 36]
The conductive line has a predetermined three-dimensional profile (3D profile), and the step of directing the laser beam includes ablating material from the sites to match the patch with the 3D profile of the conductive line. , The method described in Item 35.
[Item 37]
Ablating the material includes a plurality of first laser pulses at a first energy level selected to oxidize the surface of the patch and the first energy selected to remove the oxidized surface. 37. The method of item 36, comprising the step of sequentially applying a plurality of second laser pulses having a second energy level greater than the level in an alternating manner to remove the material from the patch.
[Item 38]
38. The method of item 36 or 37, wherein directing the laser beam comprises forming a 3D image of the patch to monitor the shape of the patch before and after ablating the material.
[Item 39]
The conductive line has a plurality of first lateral dimensions, and the step of directing the plurality of pulses of the laser radiation comprises a second lateral dimension greater than a corresponding first lateral dimension of the conductive line. 39. The method of any one of items 36-38, comprising forming the patch to have a directional dimension, ablating the material including reducing the second lateral dimension of the patch. The method described in.
[Item 40]
40. The method of item 39, wherein the second lateral dimension has at least one of a height dimension and a width dimension.
[Item 41]
41. The method of any of items 35-40, wherein directing the laser beam comprises applying a plurality of laser pulses that anneal the metal patch.
[Item 42]
A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is disposed adjacent to a target area, and the second surface is printed. Positioning towards the circuit board,
Directing a plurality of pulses of laser radiation, passing through the first surface of the donor substrate and impinging on the donor film to deposit two of the plurality of droplets from the donor film on the printed circuit board. Directing the release of a dimensional array, thereby covering the target area,
A method comprising.
[Item 43]
43. Directing the plurality of pulses of the laser radiation comprises controlling the thickness of a range of the target area by setting a spatial density of the plurality of droplets in the array. Method.
[Item 44]
44. The method of item 42 or 43, wherein directing the plurality of pulses of laser radiation comprises printing the plurality of droplets on the target area in a hexagonal pattern.
[Item 45]
A device for material deposition,
A transparent donor substrate having first and second opposing surfaces and a donor film formed on the second surface, the donor film having a thickness δ and a thermal diffusivity α, and a thermal diffusion time. τ = (δ ^Two A donor substrate characterized by / 4α),
A positioning assembly that positions the donor substrate in proximity to the acceptor substrate and positions the second surface toward the acceptor substrate;
A plurality of pulses (a plurality of laser pulses) of laser radiation having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film are directed through the first surface of the donor substrate and impinge on the donor film. An optical assembly for directing the ejection of a plurality of droplets of molten material from the donor film onto the acceptor substrate;
A device comprising.
[Item 46]
The device of item 45, wherein the donor film comprises a metal.
[Item 47]
47. The apparatus according to item 46, wherein δ ≦ 1 μm and the pulse time of the plurality of laser pulses is less than 5 nanoseconds.
[Item 48]
48. The device of item 47, wherein the pulse time of the plurality of laser pulses is less than 2 nanoseconds.
[Item 49]
The optical assembly directs a first pulse of the laser radiation at a first pulse energy selected to promote attachment of the droplets to the acceptor substrate and impinges on the donor film. Thereby forming an initial metal layer on the acceptor substrate with a second pulse energy greater than the first pulse energy, following the step of directing a plurality of second pulses of the laser radiation, 49. Apparatus according to any of items 46 to 48, wherein the droplet comprises the step of depositing the metal on the initial metal layer.
[Item 50]
Item 46, wherein the acceptor substrate is a printed circuit board and the optical assembly directs the plurality of pulses to induce deposition of the metal to repair defects in conductive traces on the printed circuit board. 50. The device according to any one of claims 49 to 49.
[Item 51]
51. Apparatus according to any one of items 45 to 50, wherein the pulse time is less than or equal to the thermal diffusion time of the donor film.
[Item 52]
Any of items 45-51, wherein the donor substrate is positioned with the second surface at least 0.1 mm from the acceptor substrate, and the plurality of pulses of the laser radiation impinge on the donor film. The device according to claim 1.
[Item 53]
53. The apparatus of item 52, wherein the donor substrate is positioned with the second surface at least 0.2 mm from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. .
[Item 54]
54. The item of any one of items 45-53, wherein the optical assembly focuses the laser radiation to impinge on the donor film with a beam spot size that is at least 10 times the thickness δ of the donor film. apparatus.
[Item 55]
55. The apparatus of any one of items 45-54, wherein the optical assembly applies the laser radiation to the donor film to cause the emission of an array of droplets covering a target area of the acceptor substrate. .
[Item 56]
A device for material deposition,
A donor substrate that is transparent and has first and second opposing surfaces and a donor film formed on the second surface, the donor film comprising a metal,
A positioning assembly for positioning the donor substrate close to the acceptor substrate with the second surface facing the acceptor substrate and providing a gap of at least 0.1 mm between the donor film and the acceptor substrate;
A plurality of pulses of laser radiation are directed through the first surface of the donor substrate to impinge on the donor film and onto the acceptor substrate through the gaps to a plurality of the metals from the donor film. An optical assembly for inducing the ejection of droplets of
A device comprising.
[Item 57]
57. The apparatus of item 56, wherein the gap between the donor film and the acceptor substrate is at least 0.5 mm and the plurality of pulses of laser radiation impinge on the donor film.
[Item 58]
Item 56, wherein the acceptor substrate is a printed circuit board and the optical assembly directs the plurality of pulses to induce deposition of the metal to repair defects in conductive traces on the printed circuit board. 57. The device according to 57.
[Item 59]
A circuit repair device,
A transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface;
A positioning assembly for positioning the donor substrate proximate to a site of a defect in a conductive trace on the printed circuit board with the second surface facing the printed circuit board;
A laser beam is directed to impinge on the site of the defect on the printed circuit board to pre-treat the site and then to direct a plurality of pulses of laser radiation to direct the first of the donor substrate. An optical assembly that passes through a surface and impinges on the donor film to induce ejection of a plurality of droplets from the donor film onto the site on the printed circuit board, thereby repairing the defect.
A device comprising.
[Item 60]
60. The apparatus of item 59, wherein pretreating the site comprises removing metal from the site by laser ablation.
[Item 61]
61. The apparatus of item 60, wherein the defects include crevices in the conductive trace, and pre-treating the site includes preforming an edge of the conductive trace adjacent the crevice.
[Item 62]
62. The apparatus of item 61, wherein preforming the edge comprises ablating the conductive trace to cause the conductive trace to tilt the edge of the conductive trace toward the crevice.
[Item 63]
63. The apparatus of item 62, ablating the conductive trace comprises forming a step slope in the conductive trace.
[Item 64]
Preforming the edge comprises ablating a plurality of trenches in the conductive trace to promote adhesion of the droplets to the conductive trace. The device according to paragraph.
[Item 65]
The optical assembly directs the laser beam to induce deposition of the plurality of droplets on the conductive traces so as to extend above the pre-shaped edge, items 61-64. The apparatus according to claim 1.
[Item 66]
Item 61. The optical assembly directs the laser beam to induce deposition of the plurality of droplets on the conductive trace to form a patch in the site that matches the profile of the conductive trace. 65. The device according to any one of 65.
[Item 67]
The optical assembly scans the laser beam onto a substrate of the printed circuit board to roughen the substrate near the site, thereby facilitating deposition of the plurality of droplets onto the substrate. 67. A device according to any one of items 59 to 66.
[Item 68]
68. The apparatus of item 67, wherein the laser beam is manipulated to form a pattern of holes in the substrate.
[Item 69]
69. The device of item 68, wherein the pattern of the plurality of holes is non-linear.
[Item 70]
The optical assembly directs the laser beam to remove an oxide layer from the conductive trace near the site to promote deposition of the droplets on the conductive trace, items 59-69. The device according to any one of claims.
[Item 71]
Repairing the defect includes forming a patch in the conductive trace, the optical assembly directing the laser beam to post-process the patch after repairing the defect, from item 59. 70. The device according to any one of 70.
[Item 72]
A circuit repair device,
A transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface;
A positioning assembly for positioning the donor substrate in proximity to the printed circuit board with the second surface facing the printed circuit board;
A plurality of first pulses of laser radiation are passed through the first surface of the donor substrate and impinge on the donor film to cause a plurality of laser pulses from the donor film onto sites of defects on the printed circuit board. An optical assembly directed to direct the ejection of a first droplet, the plurality of first pulses promoting attachment of the plurality of first droplets to a substrate of the printed circuit board, An optical assembly having a first pulse energy selected to form an initial metal layer on the substrate at the site according to
The optical assembly impinges a plurality of second pulses of the laser radiation at a second pulse energy greater than the first pulse energy through the first surface of the donor substrate and onto the donor film. An apparatus that directs the release of a plurality of second droplets from the donor film to the initial metal layer, thereby directing repair of the defect.
[Item 73]
The donor substrate is positioned with the second surface at least 0.1 mm away from the printed circuit board, and the first and second pulses of laser radiation impinge on the donor film. 72. The device according to 72.
[Item 74]
Item 72. The optical assembly directs a laser beam to remelt the plurality of second droplets to anneal the metal that repairs the defects after directing the plurality of second pulses. Or the device according to 73.
[Item 75]
75. The apparatus according to any of items 72-74, wherein the optical assembly directs a laser beam to heat the plurality of second droplets flying between the donor film and the printed circuit board. .
[Item 76]
A device for repairing a defect in a conductive wiring containing a first metal material on a printed circuit board, comprising:
A transparent donor having opposing first and second surfaces and a donor film formed on the second surface and having a higher galvanic potential than the first metallic material and having a second metallic material. Board,
A positioning assembly that positions the donor substrate proximate the site of the defect and positions the second surface toward the printed circuit board;
A plurality of pulses of laser radiation are directed through the first side of the donor substrate and impinge on the donor film to cause the donor film to land on the site of the defect on the printed circuit board. An optical assembly for inducing a plurality of droplets of a second metallic material, thereby repairing the defects and preventing galvanic corrosion.
A device comprising.
[Item 77]
77. The device of item 76, wherein the first metallic material comprises copper and the second metallic material comprises a copper alloy.
[Item 78]
Item 76. The optical assembly induces deposition of a sacrificial metal layer on the second metallic material at the site of the defect, the sacrificial metallic layer having a lower galvanic potential than the second metallic material. Or the device according to 77.
[Item 79]
A circuit repair device,
A transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface;
A positioning assembly for positioning the donor substrate proximate to a site of a defect in a conductive trace on the printed circuit board with the second surface facing the printed circuit board;
A plurality of pulses of laser radiation are directed through the first surface of the donor substrate and impinge on the donor film to provide a plurality of pulses from the donor film on the sites of the defect on the printed circuit board. Of the laser beam to induce the ejection of droplets of the metal, thereby forming a metal patch to repair the defect, and further, after forming the metal patch, directing a laser beam to post-treat the site of the defect. Assembly,
A device comprising.
[Item 80]
The conductive traces have a predetermined three-dimensional profile (3D profile) and post-treating the sites is performed from the sites using the laser beam to match the patch with the 3D profile of the conductive traces. 81. Apparatus according to item 79, comprising ablating material.
[Item 81]
Ablating the material includes a plurality of first laser pulses at a first energy level selected to oxidize the surface of the patch and the first energy selected to remove the oxidized surface. 81. The apparatus of item 80, comprising: applying a plurality of second laser pulses having a second energy level greater than the level alternately and sequentially to remove the material from the patch.
[Item 82]
82. Apparatus according to item 80 or 81, wherein the optical assembly forms a 3D image of the patch to monitor the shape of the patch before and after ablating the material.
[Item 83]
The conductive trace has a plurality of first lateral dimensions, and the optical assembly directs the plurality of pulses of laser radiation to be larger than a corresponding first lateral dimension of the conductive trace. 83. The any one of items 80-82, wherein forming the patch to have two lateral dimensions and ablating the material comprises reducing the second lateral dimension of the patch. The device according to.
[Item 84]
84. The device of item 83, wherein the second lateral dimension has at least one of a height dimension and a width dimension.
[Item 85]
85. An apparatus according to any of items 79-84, wherein post-treating the sites comprises applying the laser beam to anneal the metal patch.
[Item 86]
A device for repairing defects in conductive wiring on a printed circuit board,
A transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface;
A positioning assembly that positions the donor substrate proximate a target area and the second surface toward the printed circuit board;
A two-dimensional array of droplets from the donor film onto the printed circuit board by directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film. An optical assembly that induces the release of the target region, thereby covering the target area,
A device comprising.
[Item 87]
89. The apparatus of item 86, wherein the optical assembly modifies the spatial density of the plurality of droplets in the array to control the thickness of the area of the target area.
[Item 88]
89. The apparatus of item 86 or 87, wherein the optical assembly prints the plurality of droplets on the target area in a hexagonal pattern.

Claims (88)

A method of material deposition, comprising:
Providing a transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface, the donor film having a thickness δ and a thermal diffusivity α. , A step characterized by a thermal diffusion time τ = (δ ² / 4α),
Positioning the donor substrate in proximity to the acceptor substrate with the second surface facing the acceptor substrate;
Directing a plurality of pulses of laser radiation (a plurality of laser pulses) having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film, passing through the first surface of the donor substrate, the donor film Impinging on to induce ejection of a plurality of droplets of molten material from the donor film onto the acceptor substrate;
A method comprising.   The method of claim 1, wherein the donor film comprises a metal.   The method of claim 2, wherein δ ≦ 1 μm and the pulse time of the plurality of laser pulses is less than 5 nanoseconds.   The method of claim 3, wherein the pulse time of the plurality of laser pulses is less than 2 nanoseconds.   Directing the plurality of pulses directs a plurality of first pulses of the laser radiation at a first pulse energy selected to promote attachment of the plurality of droplets to the acceptor substrate, whereby Following the step of directing a plurality of second pulses of laser radiation, an initial metal layer is formed on the acceptor substrate with a second pulse energy that is greater than the first pulse energy, and the plurality of droplets are A method according to any one of claims 2 to 4, including the step of stacking the metal on top of an initial metal layer.   The acceptor substrate is a printed circuit board, and directing the plurality of pulses includes inducing deposition of the metal to repair defects in conductive traces on the printed circuit board. The method according to any one of 2 to 5.   7. The method of any one of claims 1-6, wherein the pulse time is less than or equal to the thermal diffusion time of the donor film.   8. The donor substrate of claim 1, wherein the donor substrate is positioned with the second surface at least 0.1 mm from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. The method according to any one of claims.   9. The donor substrate of claim 8, wherein the donor substrate is positioned on the second surface at least 0.2 mm away from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. Method.   10. The method of claim 1, wherein directing the plurality of pulses focuses the laser radiation to impinge on the donor film with a beam spot size that is at least 10 times the thickness δ of the donor film. The method according to paragraph 1.   Directing the plurality of pulses of the laser radiation comprises applying the laser radiation to the donor film to cause the emission of an array of droplets covering a target area of the acceptor substrate. The method according to any one of 1 to 10. A method of material deposition, comprising:
Providing a transparent donor substrate having opposing first and second surfaces and a donor film formed on the second surface, the donor film comprising a metal;
Positioning the donor substrate close to the acceptor substrate with the second surface facing the acceptor substrate with a gap of at least 0.1 mm between the donor film and the acceptor substrate;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate, impinging on the donor film and onto the acceptor substrate through the gap, the metal from the donor film. Inducing the release of multiple droplets of
A method comprising.   13. The method of claim 12, wherein the gap between the donor film and the acceptor substrate is at least 0.5 mm and the plurality of pulses of laser radiation impinge on the donor film.   14. The acceptor substrate is a printed circuit board and directing the plurality of pulses comprises inducing deposition of the metal to repair defects in conductive traces on the printed circuit board. The method described in. A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
Directing a laser beam to pre-treat the defect sites on the printed circuit board;
After pretreatment of the sites, a transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface is placed in proximity to the sites of the defect. Positioning the second surface towards the printed circuit board,
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film to cause a plurality of melts from the donor film to the sites on the printed circuit board. Inducing a drop ejection, thereby repairing the defect;
A method comprising.   The method of claim 15, wherein directing the laser beam comprises removing metal from the site by laser ablation.   17. The method of claim 16, wherein the defects include crevices in the conductive traces, and removing the metal comprises preforming edges of the conductive traces adjacent the crevices.   18. The method of claim 17, wherein pre-shaping the edge comprises ablating the conductive trace so as to tilt the edge of the conductive trace toward the crevice.   19. The method of claim 18, wherein ablating the conductive trace comprises forming a step slope in the conductive trace.   20. Preforming the edge comprises ablating a plurality of trenches in the conductive trace to promote adhesion of the droplets to the conductive trace. The method according to paragraph 1.   The step of directing the plurality of pulses of the laser radiation comprises depositing the plurality of droplets on the conductive trace so as to extend above the pre-shaped edge. 21. The method according to any one of 17 to 20.   Directing the plurality of pulses of the laser radiation comprises depositing the plurality of droplets on the conductive trace to form a patch in the site that matches a profile of the conductive trace. Item 22. The method according to any one of items 17 to 21.   The step of directing the laser beam directs the laser beam onto a substrate of the printed circuit board to roughen the substrate near the site, thereby facilitating deposition of the plurality of droplets onto the substrate. 23. A method according to any one of claims 15 to 22, comprising scanning.   24. The method of claim 23, wherein scanning the laser beam comprises forming a pattern of holes in the substrate.   25. The method of claim 24, wherein the pattern of the plurality of holes is non-linear.   The step of directing the laser beam includes ablating the oxide layer from the conductive wiring in the vicinity of the site using the laser beam to promote deposition of the droplets on the conductive wiring. 26. The method according to any one of claims 15 to 25.   Repairing the defect includes forming a patch in the conductive line, and the method comprises, after repairing the defect, directing the laser beam to post-process the patch. 27. A method according to any one of claims 15 to 26. A method of circuit repair,
Identifying sites of defects within the conductive traces on the printed circuit board;
A transparent donor substrate having first and second opposing surfaces and a donor film containing a metal formed on the second surface is disposed adjacent to the printed circuit board, and the second surface is disposed on the transparent substrate. Positioning towards the printed circuit board,
A plurality of first pulses of laser radiation are passed through the first surface of the donor substrate and impinge on the donor film to cause the donor film to project onto the sites of the defect on the printed circuit board. Directing the ejection of a plurality of first droplets, the plurality of first pulses promoting attachment of the plurality of first droplets to a substrate of the printed circuit board, Thereby having a first pulse energy selected to form an initial metal layer on the substrate at the site, and
Directing a plurality of second pulses of the laser radiation, the second pulse energy being greater than the first pulse energy, passing through the first surface of the donor substrate and impinging on the donor film; Inducing the release of a plurality of second droplets from the donor film to the initial metal layer, thereby repairing the defect.
A method comprising.   The donor substrate is positioned with the second surface at least 0.1 mm away from the printed circuit board, and the plurality of first pulses and the plurality of second pulses of laser radiation are disposed on the donor substrate. 29. The method of claim 28, wherein the method impinges on a film.   29. After the step of directing the plurality of second pulses, comprising directing a laser beam to remelt the plurality of second droplets to anneal the metal that repairs the defects. Or the method according to 29.   31. A method according to any one of claims 28 to 30, comprising directing a laser beam to heat the plurality of second droplets flying between the donor film and the printed circuit board. A method of circuit repair,
Identifying sites of defects in a conductive trace having a first metallic material on a printed circuit board;
A transparent donor having opposing first and second surfaces and a donor film formed on the second surface and having a higher galvanic potential than the first metallic material and having a second metallic material. Positioning the substrate proximate the site of the defect with the second side facing the printed circuit board;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film from the donor film onto the sites of the defect on the printed circuit board. Inducing the release of a plurality of droplets of the second metallic material, thereby repairing the defects and preventing galvanic corrosion.
A method comprising.   33. The method of claim 32, wherein the first metallic material comprises copper and the second metallic material comprises a copper alloy.   34. Depositing a sacrificial metal layer over the second metallic material at the sites of the defect, the sacrificial metallic layer having a lower galvanic potential than the second metallic material. the method of. A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is provided on the second surface in proximity to the defect site. Positioning towards the printed circuit board;
Directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film from the donor film onto the sites of the defect on the printed circuit board. Inducing the release of a plurality of droplets, thereby forming a metal patch to repair the defect.
Directing a laser beam to post-treat the sites of the defect after forming the metal patch;
A method comprising.   The conductive line has a predetermined three-dimensional profile (3D profile), and the step of directing the laser beam includes ablating material from the sites to match the patch with the 3D profile of the conductive line. 36. The method of claim 35.   Ablating the material includes a plurality of first laser pulses at a first energy level selected to oxidize the surface of the patch and the first energy selected to remove the oxidized surface. 37. The method of claim 36, comprising the step of sequentially applying a plurality of second laser pulses having a second energy level greater than the level in an alternating manner to remove the material from the patch.   38. The method of claim 36 or 37, wherein directing the laser beam comprises forming a 3D image of the patch to monitor the shape of the patch before and after ablating the material.   The conductive line has a plurality of first lateral dimensions, and the step of directing the plurality of pulses of the laser radiation comprises a second lateral dimension greater than a corresponding first lateral dimension of the conductive line. 39. Any one of claims 36-38, comprising forming the patch to have a directional dimension, and ablating the material comprising reducing the second lateral dimension of the patch. The method described in the section.   40. The method of claim 39, wherein the second lateral dimension comprises at least one of a height dimension and a width dimension.   41. The method of any one of claims 35-40, wherein directing the laser beam comprises applying a plurality of laser pulses that anneal the metal patch. A method of circuit repair,
Identifying defects in the conductive traces on the printed circuit board,
A transparent donor substrate having opposing first and second surfaces and a donor film having a metal formed on the second surface is disposed adjacent to a target area, and the second surface is printed. Positioning towards the circuit board,
Directing a plurality of pulses of laser radiation, passing through the first surface of the donor substrate and impinging on the donor film to deposit two of the plurality of droplets from the donor film on the printed circuit board. Directing the release of a dimensional array, thereby covering the target area,
A method comprising.   43. Directing the plurality of pulses of the laser radiation comprises controlling the thickness of a range of the target region by setting a spatial density of the plurality of droplets in the array. the method of.   44. The method of claim 42 or 43, wherein directing the plurality of pulses of laser radiation comprises printing the plurality of droplets on the target area in a hexagonal pattern. A device for material deposition,
A transparent donor substrate having first and second opposing surfaces and a donor film formed on the second surface, the donor film having a thickness δ and a thermal diffusivity α, and a thermal diffusion time. a donor substrate characterized by τ = (δ ² / 4α),
A positioning assembly that positions the donor substrate in proximity to the acceptor substrate and positions the second surface toward the acceptor substrate;
A plurality of pulses (a plurality of laser pulses) of laser radiation having a pulse time that is less than or equal to twice the thermal diffusion time of the donor film are directed through the first surface of the donor substrate and impinge on the donor film. An optical assembly for directing the ejection of a plurality of droplets of molten material from the donor film onto the acceptor substrate;
A device comprising.   The device of claim 45, wherein the donor film comprises a metal.   The apparatus of claim 46, wherein δ ≦ 1 μm and the pulse time of the plurality of laser pulses is less than 5 nanoseconds.   48. The apparatus of claim 47, wherein the pulse time of the plurality of laser pulses is less than 2 nanoseconds.   The optical assembly directs a first pulse of the laser radiation at a first pulse energy selected to promote attachment of the droplets to the acceptor substrate and impinges on the donor film. Thereby forming an initial metal layer on the acceptor substrate with a second pulse energy greater than the first pulse energy, following the step of directing a plurality of second pulses of the laser radiation, 49. The apparatus of any one of claims 46-48, wherein the droplet comprises depositing the metal on the initial metal layer.   The acceptor substrate is a printed circuit board and the optical assembly directs the plurality of pulses to induce deposition of the metal to repair defects in conductive traces on the printed circuit board. 50. The device according to any one of 46 to 49.   51. The apparatus of any one of claims 45-50, wherein the pulse time is less than or equal to the thermal diffusion time of the donor film.   52. The donor substrate of claim 45, wherein the donor substrate is positioned at least 0.1 mm away from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. The device according to any one of claims.   53. The donor substrate of claim 52, wherein the donor substrate is positioned at least 0.2 mm from the acceptor substrate and the plurality of pulses of laser radiation impinge on the donor film. apparatus.   The optical assembly focuses the laser radiation to impinge on the donor film with a beam spot size that is at least 10 times the thickness δ of the donor film. Equipment.   55. An optical assembly according to any one of claims 45 to 54, wherein the optical assembly applies the laser radiation to the donor film to cause the emission of an array of droplets covering a target area of the acceptor substrate. apparatus. A device for material deposition,
A donor substrate that is transparent and has first and second opposite surfaces and a donor film formed on the second surface, the donor film including a metal,
A positioning assembly for positioning the donor substrate close to the acceptor substrate with the second surface facing the acceptor substrate and providing a gap of at least 0.1 mm between the donor film and the acceptor substrate;
A plurality of pulses of laser radiation are directed through the first surface of the donor substrate to impinge on the donor film and onto the acceptor substrate through the gaps to a plurality of the metals from the donor film. An optical assembly for inducing the ejection of droplets of
A device comprising.   57. The apparatus of claim 56, wherein the gap between the donor film and the acceptor substrate is at least 0.5 mm and the plurality of pulses of laser radiation impinge on the donor film.   57. The acceptor substrate is a printed circuit board and the optical assembly directs the plurality of pulses to induce deposition of the metal to repair defects in conductive traces on the printed circuit board. Or the device according to 57. A circuit repair device,
A transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface;
A positioning assembly for positioning the donor substrate proximate to a site of a defect in a conductive trace on the printed circuit board with the second surface facing the printed circuit board;
A laser beam is directed to impinge on the site of the defect on the printed circuit board to pre-treat the site and then to direct a plurality of pulses of laser radiation to direct the first of the donor substrate. An optical assembly that passes through a surface and impinges on the donor film to induce ejection of a plurality of droplets from the donor film onto the site on the printed circuit board, thereby repairing the defect.
A device comprising.   60. The apparatus of claim 59, wherein pretreating the site comprises removing metal from the site by laser ablation.   61. The apparatus of claim 60, wherein the defects include crevices in the conductive trace, and pretreating the site includes preforming an edge of the conductive trace adjacent the crevice.   62. The apparatus of claim 61, wherein preforming the edge comprises ablating the conductive trace to cause the edge of the conductive trace to be tilted toward the crevice.   63. The apparatus of claim 62, wherein ablating the conductive trace comprises forming a step slope in the conductive trace.   64. Preforming the edge comprises ablating a plurality of trenches in the conductive trace to promote attachment of the droplets to the conductive trace. The device according to one paragraph.   62. The optical assembly directs the laser beam to induce deposition of the plurality of droplets on the conductive traces to extend above the pre-shaped edge. 64. The device according to any one of 64.   62. The optical assembly directs the laser beam to induce deposition of the plurality of droplets on the conductive trace to form a patch in the site that matches a profile of the conductive trace. 66. The device according to any one of claims 65 to 65.   The optical assembly scans the laser beam onto a substrate of the printed circuit board to roughen the substrate near the site, thereby facilitating deposition of the plurality of droplets onto the substrate. 67. A device according to any one of claims 59 to 66.   68. The apparatus of claim 67, wherein the laser beam is manipulated to form a pattern of holes in the substrate.   69. The device of claim 68, wherein the pattern of the plurality of holes is non-linear.   70. The optical assembly directs the laser beam to remove an oxide layer from the conductive trace near the site to promote deposition of the droplets on the conductive trace. The apparatus according to claim 1.   60. Repairing the defect comprises forming a patch in the conductive trace, the optical assembly directing the laser beam to post-process the patch after repairing the defect. 71. The device according to any one of claims 70 to 70. A circuit repair device,
A transparent donor substrate having opposing first and second surfaces and a metal-containing donor film formed on the second surface;
A positioning assembly for positioning the donor substrate in proximity to the printed circuit board with the second surface facing the printed circuit board;
A plurality of first pulses of laser radiation are passed through the first surface of the donor substrate and impinge on the donor film to cause a plurality of laser pulses from the donor film onto sites of defects on the printed circuit board. An optical assembly directed to direct the ejection of a first droplet, the plurality of first pulses promoting attachment of the plurality of first droplets to a substrate of the printed circuit board, An optical assembly having a first pulse energy selected to form an initial metal layer on the substrate at the site according to
The optical assembly impinges a plurality of second pulses of the laser radiation at a second pulse energy greater than the first pulse energy through the first surface of the donor substrate and onto the donor film. An apparatus that directs the release of a plurality of second droplets from the donor film to the initial metal layer, thereby directing the repair of the defect.   The donor substrate is positioned with the second surface at least 0.1 mm away from the printed circuit board, and the first and second pulses of laser radiation impinge on the donor film. Item 72. The apparatus according to Item 72.   The optical assembly directs a laser beam to remelt the plurality of second droplets to anneal the metal repairing the defects after directing the plurality of second pulses. 72. The device according to 72 or 73.   75. The any of claims 72-74, wherein the optical assembly directs a laser beam to heat the plurality of second droplets flying between the donor film and the printed circuit board. apparatus. A device for repairing a defect in a conductive wiring containing a first metal material on a printed circuit board, comprising:
A transparent donor having opposing first and second surfaces and a donor film formed on the second surface and having a higher galvanic potential than the first metallic material and having a second metallic material. Board,
A positioning assembly that positions the donor substrate proximate the site of the defect and positions the second surface toward the printed circuit board;
A plurality of pulses of laser radiation are directed through the first surface of the donor substrate and impinge on the donor film to cause the donor film to impinge on the sites of the defect on the printed circuit board. An optical assembly for inducing a plurality of droplets of a second metallic material to repair the defects and prevent galvanic corrosion.
A device comprising.   77. The apparatus of claim 76, wherein the first metallic material comprises copper and the second metallic material comprises a copper alloy.   The optical assembly induces deposition of a sacrificial metal layer on the second metallic material at the site of the defect, the sacrificial metallic layer having a lower galvanic potential than the second metallic material. The device according to 76 or 77. A circuit repair device,
A transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface;
A positioning assembly for positioning the donor substrate proximate to a site of a defect in a conductive trace on the printed circuit board with the second surface facing the printed circuit board;
A plurality of pulses of laser radiation are directed through the first surface of the donor substrate and impinge on the donor film to provide a plurality of pulses from the donor film on the sites of the defect on the printed circuit board. Of the laser beam to induce the ejection of droplets of the metal, thereby forming a metal patch to repair the defect, and further, after forming the metal patch, directing a laser beam to post-treat the site of the defect. Assembly,
A device comprising.   The conductive traces have a predetermined three-dimensional profile (3D profile) and post-treating the sites is performed from the sites using the laser beam to match the patch with the 3D profile of the conductive traces. 80. The apparatus of claim 79, comprising ablating material.   Ablating the material includes a plurality of first laser pulses at a first energy level selected to oxidize the surface of the patch and the first energy selected to remove the oxidized surface. 81. The apparatus of claim 80, comprising: applying a plurality of second laser pulses having a second energy level greater than the level alternately and sequentially to remove the material from the patch.   82. The apparatus of claim 80 or 81, wherein the optical assembly forms a 3D image of the patch to monitor the shape of the patch before and after ablating the material.   The conductive trace has a plurality of first lateral dimensions, and the optical assembly directs the plurality of pulses of laser radiation to be larger than a corresponding first lateral dimension of the conductive trace. 83. Any one of claims 80-82, wherein forming the patch to have two lateral dimensions and ablating the material comprises reducing the second lateral dimension of the patch. The device according to paragraph.   84. The device of claim 83, wherein the second lateral dimension has at least one of a height dimension and a width dimension.   85. The apparatus of any one of claims 79-84, wherein post-treating the site comprises applying the laser beam that anneals the metal patch. A device for repairing defects in conductive wiring on a printed circuit board,
A transparent donor substrate having first and second opposing surfaces and a donor film having a metal formed on the second surface;
A positioning assembly that positions the donor substrate proximate a target area and the second surface toward the printed circuit board;
A two-dimensional array of droplets from the donor film onto the printed circuit board by directing a plurality of pulses of laser radiation through the first surface of the donor substrate and impinging on the donor film. An optical assembly for inducing the release of the target, thereby covering the target area
A device comprising.   87. The apparatus of claim 86, wherein the optical assembly modifies the spatial density of the plurality of droplets in the array to control the thickness of the area of the target area.   88. The apparatus of claim 86 or 87, wherein the optical assembly prints the plurality of droplets on the target area in a hexagonal pattern.

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