Patent Publication Number: US-2022216087-A1

Title: Light induced selective transfer of components between substrates

Description:
TECHNICAL FIELD AND BACKGROUND 
     The present disclosure relates to a method and apparatus for light induced selective transfer of components between substrates. 
     Conventional pick-and-place is a good technology to assemble large number of millimeter sized components at low resolution alignment accuracies (100&#39;s um). Unfortunately conventional pick and place technology scales badly for higher throughput speeds (&gt;100K units a second), of small components (&lt;50 um) at high resolutions alignment accuracies (&lt;2 um). So when large amounts of microscopic components need to be placed, this may be unsuitable. For example, micro-LED (μLED) displays are a candidate for future displays Due to their brightness, only a small area of the pixel area needs to be emissive for high brightness displays. In other words, a relatively low coverage is needed. So, even for relatively high display resolutions, e.g. around 70-600 pixels per inch (PPI), depending on the application, the LEDs can be of very small dimensions, e.g. less than 30 μm. But because μLEDs can be expensive to grow at high temperatures on expensive substrates such as sapphire, it is preferred that as much as possible of the wafer area is utilized for LED fabrication. Accordingly it is desired to selectively transfer components from a growth substrate to a product substrate with increased pitch (spacing) between the components. 
     For these and other reasons it is desired to improve assembly methodology of small components such as μLEDs, combining high resolution placement and accuracy with high throughput, e.g. for manufacturing displays or other devices. 
     SUMMARY 
     Various aspects of the present disclosure relate to methods and systems involved in light induced selective transfer of components. Components on a first substrate are contacted with an adhesive layer on a second substrate while the adhesive layer is (at least partially) melted by heat. The adhesive layer is then solidified to form an adhesive connection between the components and the second substrate. The first and second substrates are moved apart to transfer the components by the adhesive connection of the adhesive layer from the first substrate to the second substrate. Components from the second substrate may then be transferred to a third substrate, e.g. by radiating light onto adhesive regions holding the components. 
     By using a hot melt adhesive layer on the second substrate, the components can be easily transferred from a first substrate to a second substrate, and then to a third substrate using (selective) light induced forward transfer. This may be more versatile compared e.g. to pick and place methods. This may be particularly beneficial if the first substrate with components is unsuitable for light induced forward transfer. For example, the first substrate itself is unsuitable, e.g. opaque. For example, the connection of the components with the first substrate is not suitably affected by the light, or at least less suitable than the presently envisaged adhesive layer. Advantageously, the transfer by light melting the adhesive layer may additionally provide improved control over the transfer, e.g. compared to other methods of LIFT relying on dry ablation, blister formation, or mismatching thermal expansion coefficient. 
     By providing the third substrate with recesses, alignment can be improved for transfer of some of the components. Furthermore contact with protrusions on the third substrate may prevent inadvertent transfer of neighboring components. For example, the contact may physically block the transfer at those positions. For example, the contacting third substrate may act as a heat sink to at least partially diminish heating of the components at the contacting positions. The recesses may also further facilitate the transfer. For example, without contact to the third substrate, the components may be released from the second substrate and travel to the third substrate. It will be appreciated that the distance travelled can be well controlled by the defined points of contact and/or depth of the recesses. This may improve control over the transfer process. Furthermore, without the heat sinking effect of the contacting third substrate, the suspended components may be heated to a relatively higher temperature causing their release, e.g. by weakening of an adhesive or other reaction at their contact position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawing wherein: 
         FIGS. 1A-1D  illustrate transferring components from a first substrate to a second substrate, and transferring a first subset of the components from the second substrate to a third substrate; 
         FIGS. 2A-2C  illustrate transferring components into recesses of a third substrate; 
         FIGS. 3A and 3B  illustrate a flow of heat according to some embodiments; 
         FIGS. 4A-4C  illustrate electrically connecting components to the third substrate; 
         FIGS. 5A-5C  illustrate preparing the components on the third substrate for further transfer; 
         FIGS. 6A-6C  illustrate transferring the components to a fourth substrate; 
         FIGS. 7A-7C  illustrate transfer between the third and fourth substrates using light. 
         FIGS. 8A-8C  illustrate transferring the components together with an electrical circuit; 
         FIGS. 9A-9C  illustrate transferring different components from respective second substrates to a common third substrate; 
         FIGS. 10A-10C  illustrate possible shapes, sizes, and distances according to some embodiments; 
         FIGS. 11A-11C  show plan view photographs of transferring a subset of components from a second substrate to a third substrate. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that the terms “comprises” and/or “comprising” specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise. Likewise it will be understood that when a connection between structures or components is described, this connection may be established directly or through intermediate structures or components unless specified otherwise. 
     According to some aspects described herein, a contact and/or non-contact light induced transfer process is provided. For example, bare die chips, micro-LEDs, or other components can be transferred. In some embodiments, all components are first bonded from a wafer or blue tape onto a transparent carrier using a thin layer a hot melt adhesive. Subsequently the components are de-bonded from the blue tape or wafer using a mechanical or optical debonding method. The subsequent carrier may be placed underneath a laser system. By impinging a beam laser onto the component, a fast, selective and non-contact transfer of the components is achieved. In order to ensure that the components are not damaged, an optically dense hot melt can be used. This can be achieved by incorporating an additive to the hot melt layer. As a consequence the energy of the laser is dissipated in the hot melt, melting it and in the process transferring the component at relatively low speeds and high accuracies. 
     In some embodiments, the components (e.g. micro-LEDs, IC&#39;s) are delivered on a wafer or blue tape and transferred to a transparent carrier substrate. The carrier substrate is coated with a liquid (hot melt) adhesive. The layer of hot melt is brought into contact with the components on the wafer or blue tape. Re-heating the hot melt will melt it, e.g. so that the components become slightly immersed in the liquid. After cooling down, the components are fixed to the hot melt and the carrier with attached components can be separated from the wafer/blue tape by peeling or by first releasing the components, e.g. using a laser lift off process. For example, the carrier may be a substrate transparent to the laser, e.g. comprising borosilicate glass, quartz, or even sapphire. To enable further alignment of the micro components on the donor receptor, a number of alignment markers may be pre-patterned to facilitate the alignment process. In this case the wafer is aligned onto the glass carrier at high precision. The carrier with attached components can now be placed in the laser system for deposition. For example, the components are detached from the carrying substrate by application of a laser pulse to the back of the component. It will be appreciated that direct LIFT from the blue tape may typically be infeasible, e.g. when the layer thickness is too thick, its optical absorption is too high and/or it may result in an ablation process with high launch speed making accurate placement difficult. In the present case e.g. a scanning mirror or other light source allows to selectively transfer the components at a high throughput rate (e.g. 10-1000 KHz). For example, this can be reached by using either an x-y scanning mirror system, or a polygon scanning mirror system. For high density patterns, the polygon mirror system can reach higher throughput rates. 
     Some previous processes for light induced transfer may have relied on an ablation process of a dry adhesive at the component adhesive interface. This typically leads to very high launching speeds since there is a high energy required to reach the ablation threshold and consequently its difficult to align. The component may even bounce or be blown away by the formed gas. Alternatively previous processes may have relied on the formation of a bubble in PI due to ablation (LEAP). This is challenging to downscale, e.g. as the bubble geometry may not scale. Also adhering the components to PI is not easy. In process using a temperature expansion coefficient mismatch between acceptor and donor the laser may be directly impinging onto the components through a PDMS substrate. This could be unwanted as the laser may damage the component itself. 
     Conversely, the present described solution relies on a thermal process where the laser beam is not necessarily brought in contact with the component. Heating can be specifically directed to the hot melt from a solid to a liquid allowing a jet to be formed, stabilizing the component while it is slowly expelled from the donor. In other words, the present methods may use the melting of a hot melt instead of ablation to allow limiting the velocity of the component but also allow for the formation of a stabilizing jet. Compared to conventional pick-and-place, such laser process is orders of magnitude faster. The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and/or cross-section illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise. 
       FIGS. 1A-1D  illustrate transferring components  11 , 12 , 13  from a first substrate  10  to a second substrate  20 , and transferring a first subset  11  of the components from the second substrate  20  to a third substrate  30 . 
     In some embodiments, e.g. as shown in  FIG. 1A , a first substrate  10  is provided with the components  11 , 12 , 13 . In one embodiments the first substrate  10  comprises an adhesive foil holding the components  11 , 12 , 13 . For example, the first substrate  10  may be formed by a backing tape or dicing tape used during wafer dicing, i.e. the cutting apart of pieces of semiconductor material following wafer microfabrication. In another embodiment, the first substrate  10  may be formed by a wafer with components, e.g. the first substrate  10 . In another or further embodiment, the first substrate  10  may itself act also as dicing tape. 
     In some embodiments, e.g. as shown in  FIG. 1A , a second substrate  20  is provided with an adhesive layer  20   a  comprising an adhesive material  20   m.  Preferably, the adhesive material  20   m  comprises a hot melt adhesive. A hot melt adhesive (HMA), also referred to as hot glue, can be described as a form of thermoplastic adhesive that undergoes a phase transition, in particular melts, under the influence of elevated temperature. When the adhesive is melted, its adhesive strength may be significantly lowered, e.g. by a factor ten, twenty, fifty, hundred, or more, compared to its solid form. Melting of the adhesive may include or consist of an increase in viscosity of the material, e.g. by a factor of more than two, three, five, ten, twenty, fifty, hundred, or more (compared to the solidified adhesive). The melting may cause a wetting and/or flowing of the adhesive material, e.g. depending on temperature. In some embodiments, the adhesive layer may be melted to the point of wetting for forming an adhesive connection with components. In other or further embodiments, the adhesive may be melted to the point of flowing for transferring the components. Hot melt adhesives typically consist of a base material with various additives. For example, common base materials may include Ethylene-vinyl acetate (EVA) copolymers, Polyolefins (PO), Polyamides and polyesters, Polyurethanes, et cetera. For example, additives may include materials such as tackifiers, waxes, stabilizers, et cetera. The natures of the base material and the additives may influence the nature of the mutual molecular interaction and interaction with the substrate. The composition may be formulated to have a suitable glass transition temperature (onset of brittleness) below the lowest service temperature and melt temperature. The melt viscosity and the crystallization rate and corresponding open time can be tailored for the application. 
     In some embodiments, e.g. as shown in  FIG. 1B , the components  11 , 12 , 13  on the first substrate  10  are brought in contact with the adhesive layer  20   a  on the second substrate  20  while the adhesive layer  20   a  is (at least partially) melted by heat H. For example, the second substrate  20  is laminated onto the first substrate  10 . For example, the adhesive layer  20   a  may be melted before and/or during contact with the components  11 , 12 , 13 . In one embodiment, the heat H is provided by irradiating the adhesive layer  20   a  with light, e.g. through the second substrate  20  as shown, or from the side of the adhesive layer  20   a  (not shown), e.g. before the contact. The heat can also be provided in other ways, e.g. using an oven to heat the adhesive layer  20   a  before and/or during the contact. 
     In a preferred embodiment, the hot melt adhesive material has a melting temperature at least above room temperature, e.g. more than forty, fifty or sixty degrees Celsius so the adhesive can easily solidify when a source of heating is removed. On the other hand it may also be preferred that the melting temperature is not too high so the adhesive strength can be easily removed when needed, e.g. during transfer, and not damage the component. For example, the adhesive layer has a melting temperature less than two hundred fifty degrees Celsius, preferably, less than two hundred degrees, more preferably less than hundred-fifty degrees, e.g. between eighty and hundred-twenty degrees Celsius. 
     In some embodiments, the adhesive layer  20   a  is allowed to solidify to form an adhesive connection between the components  11 , 12 , 13  and the second substrate  20 . For example, the solidification takes place after removing the heating (H) in  FIG. 1B . For example, the adhesive layer  20   a  may be actively or passively cooled to below its melting and/or glass transition temperature. 
     In some embodiments, e.g. as shown in  FIG. 1C , the first and second substrates  10 , 20  are moved apart, e.g. delaminated, to transfer the components  11 , 12 , 13  by the adhesive connection of the adhesive layer  20   a  from the first substrate  10  to the second substrate  20 . Preferably, the adhesive connection formed by the adhesive layer  20   a  between the components  11 , 12 , 13  and the second substrate  20  is stronger than any connection (adhesive or otherwise) the components  11 , 12 , 13  may have to the first substrate  10 , e.g. stronger by at least a factor two, three, five, ten, or more. In some embodiments, the connection or adhesion of the components  11 , 12 , 13  to the first substrate  10  may be removed or lowered before the transfer. For example, a UV dicing tape can be used as the first substrate  10  wherein the adhesive bond is broken by exposure to UV light before the components are pulled off by the second substrate  20 . It can also be envisaged to use another hot melt adhesive with a lower melting point so the adhesive layer on the first substrate  10  may still be melted while the adhesive layer  20   a  on the second substrate  20  is solidified. While the second substrate  20  is shown in the figures above the first substrate  10 , this is not necessary. For example, the configuration of the first and second substrates can be flipped upside down, or sideways. Optionally the second substrate  20  can be flipped or positioned in any desired orientation after the transfer of the components from the first substrate  10 , e.g. for subsequent steps as described in the following. 
     In some embodiments, e.g. as shown in  FIG. 1D , at least a first subset of the components  11  is transferred from the second substrate  20  to a third substrate  30 . Preferably, the transfer is initiated by radiating light L onto at least a first set of adhesive regions  21   a  of the adhesive layer  20   a  holding the at least first subset of components  11 . Preferably, the second substrate  20  is transparent, at least for the light L which is used to release the components. In a preferred embodiment, e.g. as shown, the light L is directed through the second substrate  20 , i.e. from the back of the components. Accordingly, the second substrate  20  is preferably transparent to the light L. For example, the second substrate  20  transmits most of the light, e.g. more than fifty, sixty, seventy, eighty, or even more than ninety percent. In another or further embodiment, the adhesive layer  20   a  is between the components and the light source. Most preferably, the adhesive layer  20   a  absorbs the light L. Alternatively, some of the light may be absorbed by the components which may also indirectly heat the adhesive. This latter mode of heating may be less preferred, e.g. in case the components are sensitive to heat. 
     In some embodiments, e.g. as shown, the light L is radiated exclusively onto a sub-region of the adhesive layer  20   a.  Accordingly, the adhesive layer  20   a  may be locally melted to release only the selected first subset of one or more components  11 . In the embodiment shown, a single component is transferred at a time, e.g. using a directional laser beam. Alternatively, or in addition, multiple laser beams can be used to selectively transfer multiple components simultaneously. In a preferred embodiment (not shown), a mask is disposed between a light source, e.g. flash lamp, and the second substrate  20  to project a light pattern onto the adhesive layer  20   a  which simultaneously transfers a corresponding pattern of components. While some applications may benefit particularly from the option of selective light induced transfer of subsets of components, it can also be envisaged that all components are transferred to the third substrate  30 . 
     In some embodiments, the light L may heat the adhesive material to a temperature where it starts to flow, e.g. taking the component along. Without being bound by theory, a direction of a resulting flow may be determined by the heating profile. For example, rapid heating of the adhesive material may cause a pressure wave. In a preferred embodiment, the light L is delivered a relatively short pulse for causing the heating and initiating the transfer. For example, the light pulse can be less than hundred milliseconds, less ten milliseconds, or even less than one millisecond. Using shorter pulsed may cause a sufficiently fast temperature rise before the heat has time to dissipate. In other or further embodiments, multiple pulses can be used or a longer pulse which continues to heat the adhesive material and/or component. In some embodiments, e.g. as shown, the light L causes at least the first set of adhesive regions  21   a  to melt and form one or more respective jets  21   j  of melted adhesive material  11   m , wherein the at least first subset of components  11  is transferred to the third substrate  30  by the jets  21   j  extending from the second substrate  20  towards the third substrate  30 . 
     Preferably, the hot melt adhesive layer or material has a relatively low viscosity when melted in a wetting phase to establish adhesion with the components, e.g. less than 1000 Pa·s (similar to peanut butter), preferably less than 500 Pa·s, more preferably less than 200 Pa·s, most preferably less than 100 Pa·s, typically more than 10 Pa·s. On the one hand, the viscosity is preferably low enough to allow establishing adhesion, e.g. allow the component to sink into the layer; and on the other hand high enough that the material does not start dripping from the substrate at this stage. The viscosity may be lower during the light induced transfer phase, e.g. less than 10 Pa·s (similar to honey), preferably less than 1 Pa·s, more preferably, less than 100 mPa·s, most preferably, less than 10 mPa·s, or even less than 1 mPa·s (similar to water). The lower the viscosity at this stage, the easier and/or faster the component may transfer between the substrates. Typically, the adhesive material may act as a non-Newtonian fluid, e.g. preferably shear thinning which may facilitate jet formation. When the material (re)solidifies, the viscosity may be increased, e.g. to more than 10 5  Pa·s, more than 10 6  Pa·s, and/or the material may effectively act as a solid. 
     In some embodiments, the one or more jets  21   j  may extend partially or completely (at least momentarily) between the adhesive layer  20   a  on the second substrate  20  and the components  11  on the third substrate  30 . For example, a respective component  11  may be carried by a respective jet or droplet of melted adhesive material to the third substrate  30 . This method of transfer by a melted jet may provide better control e.g. compared to (explosive) ablation of an adhesive layer. In other or further embodiments, the jet  21   a  of adhesive material may at least partially retract back to the adhesive layer  20   a  after the transfer. For example, the jet may break apart during or after the transfer. Some of the adhesive material may also be transferred together with the respective component and can optionally be cleaned off the component, if necessary. 
     In a preferred embodiment, e.g. as shown, the third substrate  30  is disposed below the second substrate  20  (along a gravitational vector) at least during the transfer of the first subset of components  11  there between. 
     For example, the first subset of components  11  can be helped by a gravitational vector falling (in a non-contact manner) over some distance DZ) towards the third substrate  30 . Also other configurations can be envisaged, e.g. the third substrate  30  can be on the top and the second substrate  20  on the bottom, or the substrates can face each other sideways. For example, the jets or droplets may carry the components in any direction, e.g. depending on momentum created by (sudden) heating of the light. 
     In some embodiments, during the transfer by radiating light L, a (non-zero) distance DZ between the components  11 , 12 , 13  on the second substrate  20  and their destination surface on the third substrate  30  is less than twice a (largest) cross-section diameter X of the components  11 , 12 , 13 . For example, the distance DZ is between five percent (factor 0.05) and two-hundred percent (factor two) the diameter X of the component (in plane with the substrate), preferably between twenty and hundred percent, more preferably between thirty and fifty percent. Within such ranges, the component placement can be relatively accurate while still having sufficient distance to completely transfer, allowing the jet to break apart, and prevent inadvertent contact of the non-transferred components  12 , 13  with the third substrate  30 . For example, a component with a cross-section size of 350 μm can be transferred over a gap size between about 20 μm and 500 μm. 
     In some embodiments, the adhesive layer  20   a  is configured to (directly) absorb a relatively high percentage of the light L before it reaches the component. In this way the energy is at least initially dissipated directly in the adhesive for causing the melting, and overheating of the component may be alleviated. In a preferred embodiment, the adhesive layer  20   a  is configured to absorb at least ten percent of the light L, preferably at least thirty percent, more preferably at least fifty percent, or even more than eighty or ninety percent. The more light is directly absorbed by the layer, the better the component may be protected from damage. 
     In some embodiments, a layer thickness DA of the adhesive layer  20   a  between the components  11 , 12 , 13  and a source of the light L is set to achieve a desired light absorption. For example, the layer thickness DA is more than ten micrometers, more than twenty micrometers, more than fifty micrometers, more than hundred micrometers, or more, e.g. up to one or two millimeters, depending on the application. For example, the layer thickness DA may be the same or similar as a thickness of the components e.g. a factor 0.1-10 times this thickness. The layer thickness may also determine an amount of material which may flow with the component during transfer. The original layer thickness of the adhesive layer can be more than the thickness DA of the material between the component and light source, e.g. if the components are partially sunken into the adhesive layer. 
     In some embodiments, an absorption coefficient of the adhesive layer  20   a  for the light L is relatively high. In some embodiments, the hot melt adhesive material may be transparent by itself. To increase absorption a dye or absorber can be added to absorb at the wavelength of the light L. For example, TiO2 can be added for a 355 nm UV laser. Since the process may be predominantly thermally driven and not ablation based, different absorbers can be considered for different types of lasers. E.g. a green laser could be used in combination with Rodamine absorber or an NIR laser 1064 with a NIR absorbing dye such as the Epolight 9837. Since the process is expected to be predominantly thermally driven and not ablation based, different absorbers can be considered for different types of lasers. E.g. a green laser could be used in combination with Rodamine absorber or an NIR laser 1064 with a NIR absorbing dye such as the Epolight 9837. 
       FIGS. 2A-2C  illustrate the third substrate  30  is provided with recesses  31  for receiving the transferred components  10 . For example, the accuracy of component placement may be improved by this or other adaptation of the third substrate  30 . 
     In some embodiments, e.g. as shown in  FIG. 2A , the first subset of components  11  is arranged according to a first component layout A on the second substrate  20 . In another or further embodiment, the third substrate  30  comprises recesses  31  disposed at least at relative positions A′ corresponding to the first component layout A. In some embodiments, e.g. as shown in  FIG. 2B , the second and third substrates  10 , 20  are aligned to have the first subset of components  11  suspended over the corresponding recesses  31  without contacting the third substrate  30 . In other or further embodiments, the light L is projected onto at least the first component layout A on the second substrate  20  to transfer the first subset of components  11  across and into the corresponding recesses  31  of the third substrate  30 . In some embodiments, e.g. as shown in  FIG. 2C , the substrates may be moved apart after the transfer. 
     In some embodiments, e.g. as shown, the components  11 , 12 , 13  on the second substrate  20  are divided in different, e.g. exclusive, subsets including a second subset of components  12  arranged according to a second component layout B. In other or further embodiments, the third substrate  30  comprises protrusions  35  formed by non-recessed areas of the third substrate  30  disposed at least at relative positions B′ corresponding to the second component layout B. In one embodiment, in the aligning the second and third substrates  10 , 20  the second subset of components  12  is in contact with the corresponding protrusions  35  of the third substrate  30 . In another or further embodiment, after the transfer of the first subset of components  11 , the second subset of components  12  remains attached to the second substrate  20 . 
     In some embodiments, a first subset of components  11  is selected for transfer during a first component transfer and arranged according to a first component layout “A”. In the embodiment shown, a second subset of components  12  is selected to remain on the second substrate  20  during the first component transfer and arranged according to a second component layout “B”. Also further subsets may be defined, e.g. in the shown embodiment the third subset of components  13  is arranged according to a layout “C”, which in this case is also selected to remain on the second substrate during the first component transfer. Of course the remaining components  12  and  13  can also be considered as part of a single layout in this regard. 
     In a preferred embodiment, a third substrate  30  comprises recesses  31  disposed at least at relative positions A′ corresponding to the first component layout “A”. In other words, the distances between the recesses  31  correspond to the distances between the first subset of components  11 . Also the sizes, e.g. diameters, of the recesses  31  correspond to the sizes of the components  11 , so that they fit in the recesses as further explained below. The concept of a recess as used herein generally refers to a concavity or an area of the third substrate  30  whose level is below the average surface level of the third substrate  30 . 
     In a preferred embodiment, the third substrate  30  comprises protrusions  35 . The protrusions  35  are disposed at least at relative positions B′ corresponding to the second component layout “B”. In other words the distances between the dimensions of the protrusions  35  correspond with those of the second subset of components  12  (and third subset of components  13  in this case). For example, protrusions can be formed by non-recessed areas of the third substrate  30 , or otherwise. The concept of a protrusion as used herein generally refers to a convexity or an area of the third substrate  30  whose level is above the average surface level of the third substrate  30 . Protrusions on the surface of the third substrate  30  may define recesses there between and/or vice versa. 
     In one embodiment, e.g. as shown in  FIG. 2B , the second and third substrates  10 , 20  are aligned, i.e. relatively positioned. In the embodiment shown, the first subset of components  11  is suspended over the corresponding recesses  31  without contacting the third substrate  30 . Furthermore, as shown, (at least) the second subset of components  12  is preferably in contact with the corresponding protrusions  35  of the third substrate  30 . 
     In some embodiments, light “L” is projected, e.g. in a first component transfer, onto at least the first component layout “A” on the second substrate  20 . Preferably, the second substrate  20  is transparent to the light “L” so that the light can shine through the second substrate  20  to illuminate the adhesive layer  20   a  and/or components  11  from the back. Alternatively, or in addition, light may also shine from other directions, e.g. heating the components which in turn heat an area of the second substrate, or layer there between, for release. In the embodiment shown, the light causes all of the first subset of components  11  to be deposited or transferred across and into the corresponding recesses  31 . At the same time (at least) the second subset of components  12  can remain attached to the second substrate  20 . In the embodiment shown, also the third subset of components  13  remains on the second substrate  20 . It will be appreciated that the contact with the corresponding protrusions  35  may prevent transfer of the second subset of components  12  in the first component transfer (and also the components  13  here). For example, the contact physically blocks the transfer. 
     In the embodiment shown, at least some of the light “L” is also projected onto the second component layout “B”. For example, the whole second substrate  20  or a significant area thereof may be illuminated. In another or further embodiment (not shown here), the light can also be patterned e.g. to selectively or exclusively illuminate the first subset of components  11 . Also in that case, the present methods can be advantageous e.g. in preventing inadvertent transfer of nearby components which can be indirectly heated via the second substrate  20 , especially when the components and distances there between are in a micrometer regime. 
     In some embodiments (not shown), the second subset of components  12  is selected for transfer during a second component transfer. The second component transfer can be separate from the first component transfer, e.g. takes place at different instances of time and/or place. For example, the second component transfer comprises aligning the second substrate  20  with the remaining second subset of components  12  over a third substrate (not shown) comprising recesses disposed at least at relative positions corresponding to the second component layout “B”. In some such embodiments, the third substrate for the second component transfer is another substrate with other recesses. In other such embodiments, the same substrate is used in the second component transfer, e.g. comprising additional recesses not used in the first component transfer. For example, in the second component transfer, light is projected onto at least the second component layout on the second substrate to transfer the second subset of components  12  components across and into the corresponding recesses. 
     In the embodiment shown, the plurality of components includes a third subset of components  13  e.g. components selected to remain on the second substrate  20  during both a first and second component transfer (not shown). In the embodiment, the third subset of components  13  is arranged according to a third component layout C. For example, the third substrate for transfer in the second component transfer comprises protrusions disposed at least at relative positions corresponding to the third component layout C for contacting the third subset of components  13  during the second component transfer. For example, the third subset of components  13  is selected for transfer during a third transfer step (not shown). Of course the components may also be divided in only two subsets, or divided into more than three subsets of components, e.g. four, five, ten, or more subsets. 
     In general, different subsets of the components can be transferred in different transfer steps into different recesses on the same or different third substrates. Preferably, each transfer step is effected by a separate (single) pulse of light “L” or a separate sequence of pulses. Alternatively, a continuous light source could be used in principle. 
     In some embodiments, components of first subset of components  11  are interspersed with components of the second subset of components  12  on the second substrate  20 . Accordingly, the density of components on the second substrate  20  can be relatively high compared to the density on the third substrate  30 . In the embodiment shown, the components  12  in the second subset have the same relative positions as the components  11  in the first subset. In other words, the second component layout “B” is the same but shifted as the first component layout “A”. This may have an advantage that the same target layout of recesses can be filled with either of the component layouts “A” or “B”. For example, a first third substrate with recesses is filled with the first subset of components  11  and a second third substrate with identical recess layout is filled with the second subset of components  12 . 
     In the embodiment shown, the components  12  of the second subset are (directly) neighboring the components  11  of the first subset on the second substrate  20 . It will be appreciated that particularly for such neighboring components it may be difficult to control localized heat deposition in the second substrate  20 , especially for small components and/or high densities. Accordingly the present methods and systems may prevent inadvertent transfer of such neighboring components. 
     In some embodiments (not illustrated here), components are transferred onto a circuit for connection therewith. For example, solder material or conductive adhesive is disposed on the third substrate to connect the component with the circuit, e.g. electrodes. Alternatively, or in addition, solder or other material may be disposed underneath the components on the second substrate and transferred together with the components. Soldering or other types of connections can be performed in one step, in some embodiments. For example, the heat from the light may cause both transfer and soldering. Alternatively, or in addition, the components may also be connected to a circuits after transfer. In some embodiments, the components comprise one or more electrical connections on top, i.e. facing away from the third substrate. For example, a connection can be made to such component by depositing, e.g. printing, an electrode on top of the third substrate advantageously connecting to the top. It will be appreciated that the recessed components can be more easily connected to the top from an adjacent (relatively raised) level of the third substrate which can be flush with the component in some embodiments. Also connections to the side of the component may be envisaged. It will be appreciated that side connections may be further facilitated by providing the recess with sloped edges. 
       FIGS. 3A and 3B  illustrate a flow of heat H according to some embodiments. In some embodiments, e.g. as shown, it may be difficult or impractical to limit an extent of the heating to the designated component  11  for transfer. For example, the components (e.g. micro-LEDs) and/or the distance between them can be relatively small. Accordingly, the heat H may spread also to neighboring components  12  which are supposed to remain on the substrate. It will be appreciated that the contacting protrusions on the third substrate may effectively keep the neighboring components  12  in contact with the adhesive layer  20   a  even if it (partially) melts. Furthermore, the contact may allow heat to be better dissipated for the neighboring components  12  than the component to be transferred  11 . After the transfer, as shown in  FIG. 3B , the adhesive layer and/or components may cool down to re-solidify the adhesive layer  20   a  and the neighboring components  12  can re-adhere to the second substrate  20 . 
     In some embodiments, the contacting third substrate  30  can act as a heat sink for the second subset of components  12 . For example, a significant fraction of heat generated by the light, e.g. pulse, is dissipated through the contact with the third substrate  30 , e.g. more than twenty percent, more fifty percent, or even more than eighty or ninety percent. This may be useful, in case at least some of the light “L” impinges at the second subset of components  12 , e.g. directly heating the second subset of components  12 . Alternatively, or in addition, it may be useful in case at least some of the light “L” impinges near the second subset of components  12 , e.g. indirectly heating the second subset of components  12  via the second substrate  20 . 
     In the embodiment shown, the light “L” causes the first subset of components  11  to be heated to a first temperature T 1  and the second subset of components  12  to a second temperature T 2 . By the measures described herein, it may occurs that the second temperature T 2  is lower than the first temperature T 1 . Preferably, the first temperature T 1  is above a threshold for releasing the first subset of components  11  from the second substrate  20 . In some embodiments, the adhesive layer  20   a  between the second substrate  20  and the first subset of components  11  is weakened to release the first subset of components  11 . In other or further embodiments, an adhesive between the second substrate  20  and the second subset of components  12  is not sufficiently weakened to release the second subset of components  12 . Alternatively, or additionally, the adhesive may cool down after the light “L” is gone and its adhesive strength is restored while the second subset of components  12  still contact the second substrate  20 . 
     In some embodiments it is preferred that the third substrate  30  has a relatively high heat conduction coefficient at least at the contacting interface. For example, the heat conduction coefficient and/or heat capacity of the third substrate  30  is relatively high compared to the heat conduction coefficient and/or heat capacity of the second substrate  20 , e.g. ten percent higher or more, e.g. twice as much. Providing the second substrate  20  with a relatively low heat conduction coefficient can also provide further benefits of lowering sideway conduction of heat H and/or facilitating heating of the components  11 . 
       FIGS. 4A-4C  illustrate electrically connecting components  11  to the third substrate  30 . 
     In some embodiments, e.g. as shown, an electrically conductive material  50   s  is applied to the components  11  while the components  11  are disposed on the third substrate  30 . In some embodiments, the components have electrical input/output connections on the top, i.e. facing away from the third substrate  30  and the conductive material  50   s  can be applied also on top. For example, the components may comprise micro-LEDs configured to direct light to the other side through the third substrate  30 . In other or further embodiments, the component connections can be at the side and/or at the bottom. In some embodiments, a solder or other material can be applied to the component connections, which can help to establish an electrical connection to electrodes  30   e  of a circuit on the third substrate  30 , as shown here; or to another substrate, as shown later. For example, the third substrate  30  may be a final substrate, e.g. used in an end product; or used as an intermediate (template) substrate for subsequent transfer. 
     In some embodiments, e.g. as shown, the recesses  31  and/or protrusions  35  comprise one or more electrodes  30   e  to form respective electrical connections with the transferred components  11 . While the conductive material  50   s  can be applied to components on a substrate without recesses (not shown) or electrodes  30   e,  it will be appreciated that having the components  10  in respective recesses  31  may help in applying the conductive material  50   s  and/or establishing electrical connections with the electrodes  30   e.  For example, the components can be at least partially, or fully sunken into the recesses  31 , or flush with the surface of the protrusions. 
     In some embodiments, e.g. as shown, a screen  50  is used with respective openings matching positions where the conductive material  50   s  is to be applied. For example, the openings are aligned with the recesses or other component positions before applying the conductive material  50   s.  For example, a screen printing or similar process can be used to easily apply the conductive material  50   s.    
     In some embodiments, e.g. as shown, the third substrate  30 , or at least the recesses  31  are provided with an adhesive layer  31   a  to hold the transferred components in the recesses. For example, the third substrate  30  (also) comprises a hot melt adhesive layer  31   a  to hold the components  11  after transfer. In some embodiments, the adhesive layer  31   a  on the third substrate  30  may be melted before the transfer. In other or further embodiments, the adhesive layer  31   a  may melt as a result of receiving a component with still elevated temperature dissipating its heat. In other or further embodiments, the adhesive layer  31   a  may be melted by applying heat during and/or after the transfer. Alternative to a hot melt adhesive, also other types of adhesive can be used for the adhesive layer  31   a,  or the adhesive layer  31   a  can be omitted, e.g. if the subsequent electrical connections are sufficient, or the components are picked up in a subsequent step. 
     In some embodiments, the adhesive layer  31   a  (hot melt or otherwise) may help to hold the components during and/or after establishing the electrical connections. In other or further embodiments, e.g. wherein the adhesive layer  31   a  is a hot melt adhesive or other layer suitable for subsequent (light induced) transfer, the components  11  can be transferred to yet another substrate as will be described later. 
       FIGS. 5A-5C  illustrate preparing the components  11  on the third substrate  30  for further transfer. In some embodiments, an electrically conductive material is applied to the components  11  (in recesses or otherwise) before the components are transferred from the third substrate  30  to a fourth substrate (not shown here). For example, a solder material can be applied which may be melted during or after the subsequent transfer. The process of applying the conductive material may otherwise be similar as explained above, e.g. using screen printing. 
       FIGS. 6A-6C  illustrate transferring the components  11   r,   11   g , 11   b  to a fourth substrate  40 . The components may all be the same, or different components, e.g. red, green, and blue (micro)LEDs arranged in a predetermined configuration on the third substrate  30 . 
     In some embodiments, e.g. as shown, the components may be picked up by the fourth substrate  40 . In other or further embodiments, the components may be adhered by the conductive material  50   s  to electrodes  40   e  on the fourth substrate. For example, adhesion of the conductive material  50   s  is activated while contacting the electrodes  40   e . Advantageously, the third substrate  30  need not be flipped to transfer the components  11 , so optionally, they need not be adhered to the third substrate  30 , e.g. only held by the recesses  31 . 
     In some embodiments, heating H may be applied, e.g. to melt a solder or other conductive material  50   s.  In other or further embodiments, the heating may lower or remove adhesion to the third substrate  30 , e.g. in case a hot melt or similar adhesive is used. It will be appreciated that picking up components can be relatively easy by virtue of their presence in recesses  31 , as shown. Alternatively, components can also be picked up from non-recessed areas. While the present embodiment shows all components  11  on the third substrate  30  being transferred to the fourth substrate  40 , it can also be envisaged to selectively transfer a subset of the components to the fourth substrate. 
       FIGS. 7A-7C  illustrate transfer between the third and fourth substrates  30 , 40  using light L. 
     In some embodiments, e.g. as shown, components are transferred selectively from the third substrate  30  to the fourth substrate  40 , e.g. using selective illumination by light L. In some embodiments, each of the components is transferred to the fourth substrate, e.g. sequentially or simultaneously. In other embodiments, only a subset of components is transferred. So it will be understood that in principle each transfer step between the first, second, third, and fourth substrates, may include the transfer of all, or a subset of components. Preferably, the transfer of the first to the second substrate, and from the third to the fourth substrate includes transfer of all components; while only a subset of components is transferred between the second and third substrate. This allows, e.g. to decrease a density of components and/or combine different components on the third substrate by selective transfer using light while the components can be simultaneously transferred to a final substrate in a desired configuration. 
     In a preferred embodiment, the solder or other conductive material  50   s  for electrically connecting the components to a respective substrate  30 , 40  is melted by the same light pulse L as used for transferring the components  11 . For example, a single light pulse can be used to heat the adhesive material and/or component for initiating the transfer, wherein that heat also causes the conductive material  50   s  to melt before or after arriving at the destination substrate. Alternatively, different light pulses can be used, or the conductive material  50   s  can be heated or otherwise activated in another way. 
     In some embodiments, the third substrate  30  with recesses  31  is re-used after transferring some or all of the components  11  to one or more further substrates  40 . For example, the third substrate  30  may act as a re-usable template with a predefined geometry of recesses to repeatedly manufacture a respective product. Optionally, the adhesive material, e.g. hot melt, can be also be re-used, or applied again between re-use. 
       FIGS. 8A-8C  illustrate transferring components  11  together with an electrical circuit. 
     In some embodiments, the third substrate  30  comprises a hot melt adhesive layer  30   a.  In one embodiment, as shown, the components  11  are held by regions of the adhesive layer  30   a  in respective recesses  31  of the third substrate  30 . In another or further embodiment, as shown, electric circuit parts  30   e  connected to the components  11  are held by regions of the adhesive layer  30   a  on respective protrusions  35  of the third substrate  30 . Accordingly the components  11  connected to the electric circuit parts  30   e  can be transferred in one step to the fourth substrate  40 . 
     In some embodiments, e.g. as shown in  FIG. 8B , contact is made between the circuit and the fourth substrate  40  while the adhesive layer  30   a  is melted, e.g. using light or other heating. For example, the fourth substrate  40  comprises a pressure sensitive adhesive or a connection with the fourth substrate  40  is established in another way. In other or further embodiments, the circuit with components may be transferred contactlessly, e.g. using a light pulse. 
     In some embodiments (not shown), the third substrate  30  comprises a mask pattern which is used for exposing a photo-curable material on the fourth substrate  40 . For example, the mask pattern comprises a circuit pattern to be used for connecting the components. For example, the photo-curable material may be altered by exposure to the light to change its conductivity. In this way electrical pathways can be formed by the exposure. Alternatively, or additionally, the photo-curable material may be developed after the exposure, possibly before the components are placed. In some embodiments, electrical connections, e.g. soldering may be established afterwards. Advantageously, this may allow automatic alignment between the components and destination circuit layout. 
     In some embodiments (not shown), one or more of the first, second, third, or fourth substrates comprise alignment marks for relative alignment, e.g. of the components with the recesses, or the recessed components with the destination circuit. For example, the alignment marks may be detectable through a respective the substrate by light exposure. 
       FIGS. 9A-9C  illustrate transferring different components  11   r,   11   b,   11   g  from respective second substrates  20   r,   20   g,   20   b  to a common third substrate  30 . 
     In the embodiment shown, the light “L” is patterned according to the first component layout “A”. In other words, the light “L” is exclusively projected onto the first subset of components  11  and/or the light “L” is blocked from projecting onto any of the other component layouts (here layouts “B” through “G”). For example, a mask is disposed between the light source (not shown here) and second substrate  20 . A mask can be particularly useful for light sources such as a flash lamp. For example, the mask passes or reflects light to project onto the first component layout “A” while preventing light from projecting onto at least the second component layout “B”, and in this case also preventing light onto any of the other layouts. Alternatively or in addition to a mask, the light can be patterned or otherwise localized in different ways, e.g. one or more relatively narrow or focused beams of (laser) light can be used. 
       FIG. 9A  illustrates a first component transfer, according to some embodiments, wherein a first component  11   r  is transferred from a second substrate  20   r  in a first recess  31   r  on the third substrate  30 . Of course also multiple of the same first components  11   r  can be transferred at different locations depending on the first component layout A. In the embodiment shown, e.g. components  12   r , 13   r  are in contact with the third substrate  30  so they remain on the second substrate  20   r.  In the embodiment shown, another component  14   r  on the second substrate  20   r  is suspended over a second recess  31   g  but not illuminated by the light “L” and thus not transferred during the first component transfer into the second recess  31   g.  The same is also the case for component  17   r  here. In some embodiments, e.g. as shown, a mask M is disposed in the light beam to selectively block light from reaching said other component  14   r.  Alternatively, light is selectively directed, e.g. by a mirror. 
       FIG. 9B  illustrates a second component transfer, according to some embodiments, wherein a second component  11   g  is transferred into the second recess  31   g.  In some embodiments, the second component  11   g  is transferred from another second substrate  20   g.  For example, the second substrate  20   g  is different from the second substrate  20   r,  e.g. comprising different components. In the embodiment shown, another component  17   g  on the second substrate  20   g  is suspended over the previously deposited first component  11   r ′ in the first recess  31   r.  Preferably, though not necessarily, said other component  17   g  is not in contact with the previously deposited first component  11   r ′. For example, the first recess  31   r  is deeper than a thickness of the previously deposited first component  11   r ′. This may prevent inadvertent transfer of said other component  17   g.  Furthermore, as shown, during the second component transfer, yet another component  14   g  on the second substrate  20   g  may be suspended over a third recess  31   b  but not illuminated by the light “L” and thus not transferred into the second recess  31   g.    
       FIG. 9C  illustrates a third transfer step, according to some embodiments, wherein a third component  11   b  is transferred from yet another second substrate  20   b  in the third recess  31   b  on the third substrate  30 . In the embodiment shown, other components  14   b,   17   b  on the second substrate  20   b  are suspended above the previously deposited first and second components  11   r ′, 11   g ′ in the respective first and second recesses. 
     In some embodiments (not shown), the third substrate  30  comprises redundant recesses which can be used to deposit additional components e.g. for repairing a device with broken components such as a display screen with broken pixels. Some aspects of the present disclosure may provide a method for repairing a third substrate  30  with previously deposited components  11  in recesses  31 , e.g. previously manufactured according to a method as described herein or otherwise. For example, in some embodiments the third substrate  30  comprises redundant empty recesses adjacent the recesses  31  with the previously deposited components  11 . Accordingly, a repair method may e.g. comprise locating a broken component among the previously deposited components  11  and adding another component in a redundant recess adjacent the broken component using a method as described herein. Instead of using redundant recesses, the substrate may also be repaired by removing broken components in any way and proceeding with the insertion of a new component in the recess cleared of the broken component according to the method as described herein. 
     These or other methods of repair may also be incorporated as part of a manufacturing process, e.g. by testing and/or locating the presence of broken components on the third substrate after one or more initial transfer steps. If broken components are detected and/or located, the methods as described herein can be used to fix or supplement any broken components to repair the third substrate For example, a method for manufacturing a display screen may comprise manufacturing a third substrate with components in recesses according to the methods described herein, wherein the components are light emitting devices forming pixels. If any broken pixels are found, these can be repaired as described by adding additional components. Alternatively, or in addition to using redundant recesses, broken components may also be removed from their respective recesses and replaced by the methods as described herein. 
       FIG. 10A  schematically illustrates relative sizes and distances between components on the second substrate  20  (which may be the same on the first substrate  10 ). 
     In some embodiments, e.g. as shown, neighboring components  11 , 12  on the second substrate  20  are spaced apart by an inter-component spacing Sc. For example, the inter-component spacing Sc is less than ten micrometer, preferably less than five micrometer, or less, e.g. between one and three micrometer. Advantageously, the smaller the inter-component spacing Sc between the components, the more effective the surface of the second substrate  20  or precursor substrate, e.g. growth substrate, may be utilized. 
     In the embodiment shown, the components  11 , 12  have a component diameter Wc (along a surface of the second substrate  20 ). For example, the component diameter Wc is less than hundred micrometer, preferably less than fifty micrometer, or even less than five micrometer, e.g. between 0.1-100 μm. Advantageously, the smaller the components, the more components fit the surface and hence, the more efficiently a surface can be used as a source for the component transfer. 
     In the embodiment shown, the components  11 , 12  have a component thickness He (transverse to the surface of the second substrate  20 ). For example, the component thickness He is less than ten micrometer, preferably less than five micrometer, ore even less than three micrometer, e.g. between 0.1-10 μm. Advantageously, the thinner the components, the less material is needed for their manufacture, which may allow cheaper production. 
     In some embodiments, as shown, it may be preferably that the component diameter We is greater than the component thickness Hc, e.g. by a factor of at least two, three, five, or more. Advantageously, components with a diameter that is relatively large compared to their thickness may be more suitable for transfer as described herein, e.g. heat more quickly by the light and less prone to rotation while transferring mid air. 
       FIG. 10B  schematically illustrates an embodiment of a third substrate  30  with a component  11  disposed in a recess  31 . 
     In the embodiment shown, the bottom of the recess  31  has a bottom diameter Wb that is at least equal to the component diameter Wc. Otherwise it may be difficult to fit the component in the recess. Preferably, a bottom of the recesses  31  has a bottom diameter Wb that is less than 1.3 times the component diameter Wc, preferably less than 1.2, more preferably less than 1.1 times, e.g. between 1.00 and 1.05 times the component diameter Wc. Advantageously, the tighter the fit between the component diameter We and the bottom diameter Wb, the more accurate may the target position be defined. 
     In the embodiment shown, a top of the recess  31  has a top diameter Wt that is at least equal to the bottom diameter Wb, preferably larger by a factor or at least 1.1, more preferably at least 1.2, e.g. the top diameter Wt is between 1.2 to 1.5 times the bottom diameter Wb. Advantageously, by providing the recesses with a top diameter that is relatively wide compare to the bottom diameter, it may be easier to transfer the components into the recesses. In other or further embodiments, as shown, the outer edges of the recesses  31  are sloped at an angle θ with respect to a surface normal of the third substrate  30  and/or bottom. For example, the angle θ is more than ten degrees, preferably more than twenty degrees or more than thirty degrees, e.g. between forty and seventy degrees. Advantageously, sloped outer edges may held guide the components into the recesses, even if the component layout on the second substrate is slightly misaligned with respect to the recesses. In some embodiments, the sloped edges may provided further functionality such as reflecting light emitted by a component in the recess. 
     Preferably, the recesses have a depth Hr that is at least equal half the component thickness Hc, preferably deeper. By providing sufficient recess depth, the third substrate may be sufficiently removed for effective component transfer. In some embodiments, as shown, the recesses have a depth Hr that is at least equal the component thickness Hc, preferably deeper e.g. by a factor of at least 1.01 or more, e.g. the recess depth Hr is between 1.1 and 1.5 times the component thickness. By providing recesses with depth greater than the component thickness, the components may be completely below the surface of the third substrate which can be of benefit for various reasons, e.g. in a subsequent transfer step or to connect electrodes to a top of the component flush with the top surface of the third substrate. 
       FIG. 10C  schematically illustrates an embodiment of a third substrate  30  with different components  11   r,   11   g,   11   b,  e.g. manufactured as described with reference to  FIGS. 9A-9C . 
     In some embodiments, e.g. as shown, a periodic distance or pitch Pt of components on the third substrate  30  is greater than a periodic distance or pitch Pd of components on the second substrate  20 , e.g. by a factor of at least two, three, five, or more. For example, the pitch Pd of components on the second substrate  20  is ten micrometer while the pitch Pt of components on the third substrate  30  is more than twenty micrometer, e.g. up to hundred micrometer, or more. 
     In some embodiments, the components  11  comprise light emitting devices, e.g. μLEDSs. In other or further embodiments, the components are grouped. For example, each group comprises light emitting devices configured to emit different colors, e.g. red, green and blue. In the embodiment shown, the groups of components  11   r,   11   g,   11   b  form pixels indicated as pix 1  and pix 2  here. For example, the third substrate  30  is part of a display screen, e.g. a monochrome or color display. In the embodiment shown, the groups of components, e.g. pixels, are spaced apart with an inter-pixel spacing Sp that is greater than the inter-component spacing Sc, though this is not necessary. Typically the pixels have a pitch Pp between forty and four hundred micrometer, or more. For example, a resolution of 70 pixels per inch PPI may correspond to a pitch of 25400/70=363 μm. For example, a resolution of 600 PPI may correspond to a pitch of 42 μm. So for a resolution of 600 PPI, the pitch Pt of grouped components may be even smaller, e.g. 42 μm/3 components=14 μm micrometer per component or smaller. Of course also other resolutions are possible. 
       FIGS. 11A-11C  show plan view photographs demonstrating selective transfer of components  11  from a second substrate  20  to a third substrate  30 .  FIG. 11A  illustrates alignment of the light (L) on the components with the laser system.  FIG. 11B  illustrates an image after transferring the components to the third substrate  30  with the (transparent) second substrate  20  still on top.  FIG. 11C  illustrates the transferred components  11  on the third substrate  30  after removing the second substrate  20 . 
     For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. For example, while embodiments were shown in cross-section view with a rows of components, of course the substrates and layouts can be two dimensional, e.g. comprising additional rows of component in various layouts. Also alternative ways may be envisaged by those skilled in the art having the benefit of the present disclosure for achieving a similar function and result. E.g. features of different layouts may be combined or split up into one or more alternative embodiments. 
     Hybrid contact/non-contact approaches as described herein may have advantages for targeted component, e.g. with the design of the cavity adapted to the component dimensions, a mechanical self-alignment is provided ensuring a high placement accuracy. This can be optionally further enhanced through reflow self-alignment in the cavity. For non-targeted components: during the transfer process, non-targeted components remain in contact with the receiving substrate, providing, on the one hand, a mechanical stop against undesired/accidental transfer. On the other hand, the physical contact of components with the receiving substrate enables an additional approach for selective transfer. While some transfer methods may use a patterned light-source directing the light only to the targeted components., the physical contact of the components can provide a heat-sink at the non-targeted locations, enabling selective component transfer also with a non-patterned light-source. Also, the non-targeted components in contact with the substrate may ensuring a well-defined stand-off height for the targeted components. 
     The various elements of the embodiments as discussed and shown thus offer various advantages, including an advantage that parts where the third substrate contacts the non-transferred components may prevent their transfer by physical blocking and heat-sinking, the advantage that in a second iteration (e.g. with different LEDS), the previously placed components do not obstruct the new components; an advantage that the recesses can provide alignment and constriction of placed components; and advantage that sloped edges of the recesses could further help with placement and may also provide a reflection surface e.g. for the LEDS. Of course, it is to be appreciated that any one of the above embodiments or processes may be combined with one or more other embodiments or processes to provide even further improvements in finding and matching designs and advantages. It is appreciated that this disclosure offers particular advantages to manufacture and repair of display, particularly using microscopic sized LEDs, and in general can be applied for any application wherein components are selectively transferred by light. 
     Aspects of the present disclosure may be embodied by an apparatus configured and/or programmed to perform the methods. For example, the apparatus comprises respective substrate handlers to provide the various substrates and relatively position them with respect to each other and/or with respect to a light source for delivering the light to the substrates. In some embodiments, the substrate handlers, light source, and/or optional mask between the light source and substrate(s) can be moved by one or more actuation and/or alignment mechanism. Also other components, e.g. mirrors to direct a laser beam may be controlled. The action of these and other components may be determined by a controller, e.g. with hardware and/or software components, to perform operational acts in accordance with the present methods. Aspects of the present disclosure may also be embodied as a (non-transitory) computer-readable medium storing instructions that, when executed by one or more processors, cause a device to perform the method as described herein. 
     In interpreting the appended claims that follow, it should be understood that the word “comprising” does not exclude the presence of other elements or acts than those listed in a given claim; the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several “means” may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise.