Apparatus and method for printing a viscous substance, by means of laser induced forward transfer, on a product

Abstract

An apparatus for printing viscous substance, by means of Laser Induced Forward Transfer, on a product, comprising: - a substrate handler arranged for holding a substrate and positioning a first surface of the substrate into a coating position and a printing position; - a support for positioning the first surface of the product; - a coater arranged for providing a layer of viscous substance on the first surface of the substrate; - a printing device comprising a first emitter unit arranged for transmitting a beam of electromagnetic radiation for printing; - a scanning device arranged for scanning the beam of electromagnetic radiation; - a control unit communicatively coupled with the substrate handler and / or the support; the apparatus further comprising at least one of: - a warping system arranged for introducing a predetermined warp of the first surface of the product; and - a measuring device arranged for measuring a warp of the first surface of the product. A method of printing viscous substance on a product using the apparatus.

Description

[0001] Title: Apparatus and method for printing a viscous substance, by means of Laser Induced Forward Transfer, on a product

[0002] Description:

[0003] According to a first aspect of the present disclosure, the disclosure relates to an apparatus for printing a viscous substance, by means of Laser Induced Forward Transfer, on a product.

[0004] According to a second aspect of the present disclosure, the disclosure relates to a method for printing a viscous substance, by means of Laser Induced Forward Transfer, on a product using an apparatus according to the first aspect of the present disclosure.

[0005] A known method for applying a viscous substance such as solder paste to a product, such as a Printed Circuit Board (PCB), relies on stencil printing or dispensing. Stencil printing is a deposition method requiring direct contact with the PCB. Stencil printing is a non-digital method, where a stencil, also referred to as a mask, is used to define the printing pattern. It also limits the freedom to achieve small volumes for small components while allowing relatively large volumes of viscous substance to be applied for the larger components which are also still present on new PCBs.

[0006] Dispensing is a nozzle-based deposition technology requiring the control of a gap that is present between the end of the nozzle and the PCB. The gap between the end of the nozzle and the PCB is either actively measured and compensated or calibrated according to a pre-mapping. A drawback of dispensing is the relatively low speed of applying the viscous substance. It is noted that a relatively high speed of applying viscous substance is in particular relevant for high volume production. A further drawback of dispensing is the relative frequent clogging of nozzles of the dispenser resulting in missed shots, thereby avoiding, or at least partly avoiding, application of viscous substance onto the PCB. A further method for applying a viscous substance on a product, such as solder interconnects in a three-dimensional Integrated Circuit (IC), also referred to as 3D interconnects, 3D chip stacking, 3D stacking or 3D packaging may comprise placing preformed solder balls in deposits of a Ball Grid Array (BGA) socket. A drawback of this placement technique is the relatively expensive equipment required. In addition, the size of the solder balls that may be placed is relatively large.

[0007] Because products may have warpage, defining a fixed printing gap with a high precision over an area is hard. Warpage, for instance, within a printed circuit board comes mainly from the unequal division of copper within the different layers of the printed circuit board and becomes especially evident after the printed circuit board went through the printed circuit board assembly production line once, because of the heat exposure during the reflow process. When a printed circuit board has gone through the assembly production line again in order to solder the components on the other side of the printed circuit board, the warpage may be even larger. Said warpage has a large impact on the printing gap and it is important to keep the printing gap as stable / constant as possible over the whole printing area.

[0008] It is an object of the present disclosure to provide an apparatus and a method that at least partly overcomes a drawback of the known methods of applying a viscous substance to a product.

[0009] The apparatus according to the first aspect of the present disclosure comprises: a substrate handler arranged for holding a substrate and positioning a first surface of the substrate into a coating position and a printing position, wherein, in the printing position, the first surface of the substrate is at a predetermined position relative to a first surface of the product for printing the viscous substance, by means of Laser Induced Forward Transfer, on the product; a support for positioning the first surface of the product in relation to the first surface of the substrate in the printing position of the substrate; a coater arranged for providing a layer of viscous substance on the first surface of the substrate in the coating position of the substrate; a printing device comprising a first emitter unit arranged for transmitting a beam of electromagnetic radiation for printing, by means of Laser Induced Forward Transfer, in the printing position of the substrate, the viscous substance, by means of Laser Induced Forward Transfer, on the first surface of the product; a scanning device arranged for scanning the beam of electromagnetic radiation across the first surface of the substrate for printing a selective layer-part of the viscous substance, by means of Laser Induced Forward Transfer (LIFT).

[0010] Laser Induced Forward Transfer (LIFT) is a direct-write technique that was first reported by Bohandy, Kim, and Adrian in 1986 for the deposition of Cu patterns on Si and fused silica substrates under high vacuum conditions. In this technique, a pulsed laser is used to induce the transfer of the material from a donor substrate to a receiver substrate, usually placed at a short distance or in contact with each other. Donor substrates are usually laser transparent and coated with a thin film of the material of interest. As the laser beam passes through the transparent substrate, it is being absorbed by the film, which is subsequently propelled toward the receiver substrate, above a certain laser energy threshold.

[0011] Providing the apparatus with the substrate handler and the support, a substrate may be positioned relative to the product. In addition, the functionality of the substrate handler to hold the substrate and positioning the substrate in a coating position and a printing position allows the substrate to be coated in a position wherein the risk of damaging the product during the coating, by the coater, for instance by spilling of viscous substance may be prevented.

[0012] The coater is used to apply a layer of viscous substance on the substrate, which can be relatively small compared to the product. This coated substrate is then positioned relative to the product using the substrate handler and the support, as explained above, such that the viscous substance may be transferred to the product by means of the LIFT process.

[0013] The beam of electromagnetic radiation originating from the first emitter unit is arranged for locally removing the viscous substance from the substrate at the location of impingement of the beam of electromagnetic radiation at the surface of the viscous substance.

[0014] In this regard, the beam of electromagnetic radiation is arranged for locally heating the layer of viscous substance up to a temperature causing rapid vaporization of part of the viscous substance. Due to the rapid vaporization, a gas bubble is formed that locally pushes the viscous substance away from the substrate.

[0015] By positioning the product relative to the substrate in a predetermined position, the viscous substance that is pushed away from the substrate may be directed to predetermined positions of the product and thereby providing the product with viscous substance at the predetermined positions.

[0016] The scanner device allows for scanning the beam of electromagnetic radiation along the surface of the viscous substance and thereby allowing to transfer a predetermined pattern of the viscous substance and thereby printing viscous substance onto the product according to the predetermined pattern.

[0017] The apparatus further comprises a control unit communicatively coupled with the substrate handler and / or the support; and at least one of: a warping system arranged for introducing a predetermined warp of the first surface of the product, wherein the control unit is arranged for controlling the substrate handler and / or the support, based on the predetermined warp, for positioning, during printing, a part of the selective layer-part that is to be printed at a predetermined distance from a location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed; and a measuring device arranged for measuring a warp of the first surface of the product, wherein the control unit is arranged for controlling the substrate handler and / or the support, based on the warp measured by the measuring device, for positioning, during printing, a part of the selective layer-part that is to be printed at a predetermined distance from a location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed. The invention according to the present disclosure relies at least partly on the insight that in order to print a viscous substance on products, the printing gap has to be controlled at a high precision. This can be achieved by mapping / measuring the first surface of the product including its warpage and actively adjust the position of the first surface of the substrate relative to the first surface of the product. This adjustment can be done with multiple degrees of freedom and the measuring of the first surface of the product with a viscous substance measuring system. It is important that after measuring / mapping of the first surface of the product, the first surface of the product doesn’t change which can be achieved by clamping the product before the mapping is done and until after the printing of the viscous substance on the first surface of the product has been done. With the apparatus according to the present disclosure, the warpage can be controlled such that the printing gap can be kept constant, i.e. , within defined limits, over the whole printing area.

[0018] The printing gap is defined as the distance between the surface of the layer of viscous substance and the surface of the product onto which the viscous substance is to be printed.

[0019] With “degrees of freedom” as used in the present disclosure are meant the types and directions of moving the substrate, i.e., sliding along and rotating about the x, y, and z axes.

[0020] Preferably, the apparatus further comprises at least the other of the warping system and the measuring device, wherein the control unit is arranged for controlling the substrate handler and / or the support, based on the predetermined warp and the warp measured by the measuring device, for positioning, during printing, the part of the selective layer-part that is to be printed at the predetermined distance from the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed.

[0021] In an embodiment, the control unit is further arranged for controlling, based on the warp measured by the measuring device, the warping system for introducing the predetermined warp. In another embodiment, the warping system is further arranged for maintaining the predetermined warp during printing.

[0022] It may be beneficial that the warping system is further arranged for introducing a convex warp in at least one direction of the product seen from the side of the first surface of the product.

[0023] The warping system may comprise a clamping arrangement for clamping the product at predetermined locations of the product, preferably at predetermined locations at one or more edges of the product, for introducing the predetermined warp.

[0024] The clamping arrangement may comprise a pre-formed frame or two or more clamps and / or pins, preferably two or more clamps and / or pins, such as four or six clamps and / or pins. The introduction of a multiplicity of clamping or other force generating elements like the clamps and / or pins provides improved pre-warp in the product and enables asymmetric warp conditions. Such localized or “tailor-made” warpage is especially beneficial for larger or more flexible PCBs.

[0025] The pre-formed frame or clamps and / or pins may be positioned under the product to be warped.

[0026] The clamping arrangement may further comprise means for creating a vacuum for fixating the product in the warping system, such as a vacuum pump, a suction cup, or a venturi device.

[0027] With “warping” as used in the present disclosure is meant that the warpage may be any type of warpage, such as linear warpage, bi-directional warpage, twist or torsional warpage, or a combination of two or more thereof. Bi-directional warpage includes saddle-shaped warpage, wherein the product is concave in one direction and convex in the other, and domed warpage, wherein the product is convex or concave in both in-plane directions simultaneously. In an embodiment, the measuring device is arranged for measurement of a topography of the first surface of the product and arranged for determining, based on the topography measured, the warp of the first surface of the product.

[0028] In another embodiment, the control unit is further arranged for controlling the substrate handler and / or the support for positioning, during printing, a part of the selective layer-part that is to be printed substantially parallel, preferably parallel, to a region of the first surface of the product comprising the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed.

[0029] In yet another embodiment, the support comprises the warping system.

[0030] In an embodiment, the apparatus comprises a gap control module arranged for controlling a printing gap between the substrate and the product based on the warp measured by the measuring device.

[0031] The gap control module may be arranged for bringing the substrate at the predetermined position relative to the first surface of the product.

[0032] The apparatus according to the first aspect of the present disclosure may further comprise a heating device arranged for heating the viscous substance, preferably the heating device is arranged for heating the selective layer-part of the viscous substance on the substrate. Heating of the viscous substance, preferably the selective layer-part of the viscous substance on the substrate, preheats the viscous substance, preferably the selective layer-part of the viscous substance on the substrate, to reduce the viscosity of said viscous substance, preferably the selective layer-part of the viscous substance on the substrate.

[0033] The method according to the second aspect of the present disclosure comprises the steps of: providing the substrate and the product; supporting, by the support, the product; holding the substrate, by the substrate handler; moving the substrate, by the substrate handler, to the coating position; providing, by the coater, the layer of viscous substance on the first surface of the substrate; moving, by the substrate handler, the substrate to the printing position; emitting, by the first emitter unit, the beam of electromagnetic radiation for printing the viscous substance, by means of Laser Induced Forward Transfer (LIFT), on the product; scanning, by the scanning device, the beam of electromagnetic radiation across the first surface of the substrate for printing the selective layer-part of the viscous substance, by means of Laser Induced Forward Transfer (LIFT); and further comprising at least one of the steps of: warping, by the warping system, the product and introducing the predetermined warp of the first surface of the product and controlling, by the control unit, the substrate handler and / or the support, based on the predetermined warp, for positioning, during the step of scanning, the part of the selective layer-part that is to be printed at the predetermined distance from the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed; and measuring, by the measuring device, the warp of the first surface of the product and controlling, by the control unit, the substrate handler and / or the support, based on the warp measured by the measuring device, for positioning, during the step of scanning, the part of the selective layer-part that is to be printed at the predetermined distance from the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed.

[0034] The skilled person will understand that the order of execution of the steps of the method according to the second aspect of the present disclosure may be different as compared to the order as presented in the claims. Hence, the method steps may be executed in different manners.

[0035] During the step of warping, the control unit may be controlling the warping system based on the warp measured by the measuring device, for introducing the predetermined warp. During the step of scanning, the warping system may maintain the predetermined warp.

[0036] During the step of scanning, the printing gap between the substrate and the product may be controlled by the gap control module based on the warp measured by the measuring device.

[0037] During the step of moving, the substrate may be brought at the predetermined position relative to the first surface of the product by the gap control module.

[0038] During the step of scanning, the control unit may be controlling the substrate handler and / or the support for positioning the part of the selective layer-part that is to be printed substantially parallel, preferably parallel, to the region of the first surface of the product comprising the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed.

[0039] In an embodiment of the method according to the second aspect of the present disclosure, an accuracy of a distance between the part of the selective layer-part that is to be printed and the location at the first surface of the product onto which the viscous substance of the part of the selective layer-part is to be printed is in the range of -50 micrometres and 50 micrometres, preferably in the range of -25 micrometres and 25 micrometres, more preferably in the range of -5 micrometres and 5 micrometres.

[0040] During the step of scanning, a distance between a surface of the layer of viscous substance facing away from the first surface of the substrate and the first surface of the product onto which the viscous substance is to be printed may be at a predetermined distance in the range of 30 micrometres to 1000 micrometres, preferably in the range of 30 micrometres to 400 micrometres.

[0041] The method according to the second aspect of the present disclosure may further comprise a step of heating, by a heating device, the viscous substance, wherein the heating is done before the step of emitting. Preferably, the selective layer-part of the viscous substance on the substrate is heated by the heating device.

[0042] Preferably the viscous substance comprises solder paste and wherein, during the step of heating, by the heating device, the viscosity of the solder paste is in the range of 0.5 to 200 Pa-s.

[0043] In this regard, the viscosity of the solder paste may be determined according to the IPC-TM-650-2.4.34.2 Test Methods Manual and IPC-TM-650-2.4.34.3 Test Methods Manual depending on the viscosity of the solder paste.

[0044] In an embodiment, one or more of the steps of moving the substrate to the coating position, providing the layer of viscous substance, moving the substrate to the printing position, and emitting the beam of electromagnetic radiation are repeated for providing the viscous substance to predetermined positions on the product.

[0045] In another embodiment, the substrate is substantially transparent, preferably transparent, for the electromagnetic radiation emitted, by the first emitter unit, during the step of emitting.

[0046] Embodiments of the apparatus for printing viscous substance on a product according to the first aspect of the present disclosure as presented herein are also applicable to the method for printing viscous substance on a product according to the second aspect of the present disclosure, and vice versa.

[0047] Effects of the apparatus for printing viscous substance on a product according to the first aspect of the present disclosure as presented herein correspond to or are similar to effects of the method for printing viscous substance on a product according to the second aspect of the present disclosure.

[0048] The present disclosure is hereinafter explained in more detail with reference to the accompanying drawings in which embodiments of the present disclosure are shown and in which like reference numbers indicate the same or similar elements. The present disclosure is by no means limited to the embodiments described therein.

[0049] Fig. 1 schematically shows a top view of an apparatus according to the present disclosure;

[0050] Fig. 2 schematically shows an isometric side view of the apparatus of Fig. 1 ;

[0051] Fig. 3 schematically shows an isometric side view of the apparatus of Fig. 1 ;

[0052] Fig. 4A and 4B schematically shows details of a warping system of an apparatus according to the first aspect of the present disclosure;

[0053] Fig. 5 schematically shows the various situations for introducing warpage in the product;

[0054] Fig. 6 schematically shows printing of viscous substance on a warped product;

[0055] Fig. 7 schematically shows a method according to the present disclosure;

[0056] Fig. 8 schematically shows a method according to the present disclosure.

[0057] In Fig. 1 , an apparatus 1 according to the present disclosure for printing a viscous substance 2 on a product 3 is shown. The apparatus 1 comprises a substrate handler 4 arranged for holding a substrate 5 and positioning a first surface 7 of the substrate 5 into a coating position 9 and a printing position 11. In the printing position 11 , the first surface 7 of the substrate 5 is at a predetermined position relative to a first surface 12 of the product 3 for printing the viscous substance 2 on the product 3.

[0058] The apparatus 1 also comprises a support 13 for positioning the first surface 12 of the product 3 in relation to the first surface 7 of the substrate 5 in the printing position 11 of the substrate 5. In the shown top view of the apparatus 1 , the product 3, seen from an operator’s 39 position, moves from left to right as indicated by the black arrows.

[0059] Furthermore, in Fig. 1 , the apparatus 1 comprises a coater 15 arranged for providing a layer 17 of viscous substance 2 on the first surface 7 of the substrate 5 in the coating position 9 of the substrate 5; a printing device 19 comprising a first emitter unit 21 arranged for transmitting a beam of electromagnetic radiation 23 for printing, in the printing position 11 of the substrate 5, the viscous substance 2 on the product 3; a scanning device 25 arranged for scanning the beam of electromagnetic radiation 23 across the first surface 7 of the substrate 5 for printing a selective layer-part 27 of the viscous substance 2; and a warping system 31 arranged for introducing a predetermined warp of the first surface 12 of the product 3, wherein a control unit 29 (not visible in Fig. 1) is arranged for controlling the substrate handler 4 and the support 13, based on the predetermined warp, for positioning, during printing, a part of the selective layer-part 27 that is to be printed at a predetermined distance from a location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed.

[0060] Fig. 2 shows an isometric side view of the apparatus 1 of Fig. 1 from the side facing towards the operator 39 (not shown in Fig. 2). This side view provides more details about how the apparatus 1 according to the present disclosure may be arranged; for example, the first emitter unit 21 is clearly shown next to the printing device 19 and the printing device 19. The apparatus 1 further comprises a measuring device 33 arranged for measuring a warp of the first surface 12 of the product 3, wherein the control unit 29 (not visible in Fig. 2) is arranged for controlling the substrate handler 4 and the support 13, based on the warp measured by the measuring device 33, for positioning, during printing, a part of the selective layer-part 27 that is to be printed at a predetermined distance from a location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed.

[0061] The apparatus 1 shown in Fig. 2 further comprises a heating device 49 arranged for heating the viscous substance 2, preferably for heating the selective layer-part 27 of the viscous substance 2 on the substrate 5.

[0062] Fig. 3 shows an isometric side view of the apparatus 1 of Fig. 1 from the side facing away from the operator 39 (not shown in Fig. 3). From this side the control unit 29 can be seen. The control unit 29 is communicatively coupled with the substrate handler 4 and the support 13. The scanning device 25 is also clearly visible in this side view. Furthermore, the control unit 29 is further arranged for controlling, based on the warp measured by the measuring device 33, the warping system 31 for introducing the predetermined warp.

[0063] The measuring device 33 is further arranged for measurement of a topography of the first surface 12 of the product 3 and arranged for determining, based on the topography measured, the warp of the first surface 12 of the product 3.

[0064] Fig. 3 further shows that the substrate handler 4 comprises a gap control module 45 arranged for controlling a printing gap between the substrate 5 and the product 3 based on the warp measured by the measuring device 33. The gap control module 45 is arranged for bringing the substrate 5 at the predetermined position relative to the first surface 12 of the product 3.

[0065] As depicted in Figs. 1-3, the support 13 comprises the warping system 31.

[0066] Fig. 4A shows a side view of part of the apparatus 1 according to the first aspect of the present disclosure. In Fig. 4A, a product 3 having the first surface 12 is fixated on the warping system 31 that comprises a clamping arrangement 35. The clamping arrangement 35 is for clamping the product 3 at predetermined locations of the product 3, preferably at predetermined locations at the edges of the product 3, for introducing the predetermined warp. The warping system 31 is further arranged for maintaining the predetermined warp during printing and for introducing a convex warp in at least one direction of the product 3 seen from the side of the first surface 12 of the product 3.

[0067] In Fig. 4B, which shows a side view of part of the apparatus 1 according to the first aspect of the present disclosure, the warping system 31 is used for warping the product 3 by moving the edges of the warping system 31 towards each other (indicated by the arrows pointing towards each other) such that the convex warp is introduced (indicated by the arrow pointing upwards). Fig. 5 shows several situations of a product 3 onto which forces are being applied at several locations (indicated by the solid arrows). Depending on where the forces are applied, warpage is introduced in the product 3 in different manners.

[0068] In (a), a top view and a side view of a product 3 are shown. The product 3 is clamped at the sides with the clamping arrangement 35, being two clamps, and forces are applied at the edges on the short sides of the product 3 resulting in the edges on the short sides being pushed downwards thereby introducing a symmetric convex warp, which is similar to the situation shown in Fig. 4B. The clamping arrangement 35 may also be a preformed frame or comprise two pins.

[0069] In (b), a top view of a product 3 is shown. The product 3 is clamped at the four corners with the clamping arrangement 35, being four clamps and / or pins, and equal forces are applied on each corner. The forces applied to diagonally opposed clamps are equally strong and directed in opposing directions enabling that a torsional force can be applied, whereby the product 3 can be twisted. Such torsional force could be combined with a linear force, for example as shown in situation (a), to provide both a linear warp and a bi-directional and / or torsional warp (also referred to as twist).

[0070] In (c), a top view and a side view of a product 3 are shown. The product 3 is clamped with the clamping arrangement 35 near the edge at one side of the product 3 and more towards the middle at the other side of the product 3 and at several locations along the periphery of the product, as indicated by the arrows. By clamping the product 3 in this manner, it becomes possible to use certain elements, for example clamps, to introduce force intended to warp or twist the product 3, and other elements, for example pins, to introduce pinning points in order to limit the motion of specific portions of the product 3. For example, a pinning element could be used to induce an asymmetric warpage, whereby the left-hand side of the product 3 is essentially unwarped, whilst the right-hand side of the product 3 exhibits a warp starting at the point of the pinning point. The dashed line indicates where the warp starts.

[0071] Fig. 6 (a)-(d) shows a schematic of the printing of viscous substance on a warped product having a first surface 12 with a convex warp. In Fig. 6 (a), a product 3, having a first surface 12, and a substrate 5 that is transparent for the electromagnetic radiation 23 emitted by the first emitter unit 21 , e.g., a glass substrate, having a first surface 7 on which a layer 17 of viscous substance 2 has been applied, are positioned above each other in the printing position 11. By presenting the product 3 having the convex-warped first surface 12 below the substrate 5 it can be used as a deposition method. The distance d2 between the surface 37 of the layer 17 of viscous substance 2 facing away from the first surface 7 of the substrate 5 and the first surface 12 of the product 3 onto which the viscous substance 2 is to be printed is at a predetermined distance in the range of 30 micrometres to 1000 micrometres, preferably in the range of 30 micrometres to 400 micrometres.

[0072] The first surface 12 of the product 3 has a convex warp that has a topography that remains the same during the printing viscous substance 2 on a product 3.

[0073] The control unit 29 is further arranged for controlling the substrate handler 4 and the support 13 for positioning, during printing, a part of the selective layer-part 27 that is to be printed parallel to a region of the first surface 27 of the product 3 comprising the location at the first surface 27 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed (indicated by the dashed circle).

[0074] An accuracy of a distance d1 between the part of the selective layer-part 27 that is to be printed and the location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed may be in the range of -50 micrometres and 50 micrometres. The accuracy of the distance d1 is preferably in the range of -25 micrometres and 25 micrometres, more preferably in the range of -5 micrometres and 5 micrometres.

[0075] A beam of electromagnetic radiation 23 is transmitted by a first emitter unit 21 (not shown) on the substrate 5. The apparatus 1 according to the first aspect of the present disclosure is arranged for providing the beam of electromagnetic radiation 23 of the first emitter unit 21 to the first surface 7 of the substrate 5 via a second surface 41 of the substrate 5. The beam of electromagnetic radiation 23 locally heats a selective layer-part 27 of the layer 17 of viscous substance 2 causing rapid vaporization within the layer 17 of the viscous substance 2 such that a gas bubble 43 is formed.

[0076] As becomes clear from Fig. 6 (a), the substrate 5 is transparent for the electromagnetic radiation 23 emitted, by the first emitter unit 21 , during the emitting.

[0077] In Fig. 6 (b), the gas bubble 43 pushes the selective layer-part 27 of the layer 17 of the viscous substance 2 away from the substrate 5. Viscous substance 2 that is pushed away by the bubble 43 is deposited on the predetermined position on the surface 51 of the product 3. Subsequently in Fig. 6 (c), the substrate 5 is moved upwards (indicated by the black arrows) thereby creating a rupture position (indicated by the dashed circle) such that the selective layer-part 27 of the layer 17 of the viscous substance 2 is being separated from the layer 17 of viscous substance 2. As shown in Fig. 6 (d), the selective layer-part 27 of viscous substance 2 is deposited on the predetermined position on the product 3. Hence, the viscous substance 2 is printed on the printing circuit board 3. As seen in Fig. 6(d), the tip of the deposited droplet of viscous substance 2 has a concave tip. However, the droplet may also have a convex tip instead.

[0078] A method 101 for printing viscous substance 2 on a product 3 using the apparatus 1 is shown in Fig. 7. The method 101 comprises the steps of providing 103 the substrate 5 and the product 3; supporting 105, by the support 13, the product 3; holding 107 the substrate 5, by the substrate handler 4; moving 109 the substrate 5, by the substrate handler 4, to the coating position 9; providing 111 , by the coater 15, the layer 17 of viscous substance 2 on the first surface 7 of the substrate 5; moving 113, by the substrate handler 4, the substrate 5 to the printing position 11 ; emitting 115, by the first emitter unit 21 , the beam of electromagnetic radiation 23 for printing the viscous substance 2 on the product 3; scanning 117, by the scanning device 25, the beam of electromagnetic radiation 23 across the first surface 7 of the substrate 5 for printing the selective layer-part 27 of the viscous substance 2; warping 119-1 , by the warping system 31 , the product 3 and introducing 119-2 the predetermined warp of the first surface 12 of the product 3 and controlling 119-3, by the control unit 29, the substrate handler 4 and the support 13, based on the predetermined warp, for positioning, during the step of scanning 117, the part of the selective layer-part 27 that is to be printed at the predetermined distance from the location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layerpart 27 is to be printed; and measuring 121-1 , by the measuring device 33, the warp of the first surface 12 of the product 3 and controlling 121-2, by the control unit 29, the substrate handler 4 and the support 13, based on the warp measured by the measuring device 33, for positioning, during the step of scanning 117, the part of the selective layer-part 27 that is to be printed at the predetermined distance from the location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed.

[0079] During the step of warping 119-1 , the control unit 29 is controlling the warping system 31 based on the warp measured by the measuring device 33, for introducing the predetermined warp.

[0080] During the step of scanning 117, the warping system 31 maintains the predetermined warp.

[0081] During the step of scanning 117, the printing gap between the substrate 5 and the product 3 is controlled by the gap control module 45 based on the warp measured by the measuring device 33.

[0082] During the step of moving 113, the substrate 5 is brought at the predetermined position relative to the first surface 12 of the product 3 by the gap control module 45.

[0083] During the step of scanning 117, the control unit 29 is controlling the substrate handler 4 and the support 13 for positioning the part of the selective layer-part 27 that is to be printed substantially parallel, preferably parallel, to the region of the first surface 12 of the product 3 comprising the location at the first surface 12 of the product 3 onto which the viscous substance 2 of the part of the selective layer-part 27 is to be printed.

[0084] As becomes clear from Fig. 7, the step of warping 119-1 the product 3 and introducing 119-2 the predetermined warp of the first surface 12 of the product 3 and controlling 119-3 the substrate handler 4 and the support 13 may be skipped. Alternatively, the step of measuring 121-1 the warp of the first surface 12 of the product 3 and controlling 121-2 the substrate handler 4 and the support 13 may be skipped.

[0085] The order of execution of the steps may be different as compared to the order as disclosed in Fig. 7. Hence, the steps of the method 101 may be executed in different manners than the order as disclosed in the claims.

[0086] Fig. 7 further shows that one or more of the steps of moving 109 the substrate 5 to the coating position 9, providing 111 the layer 17 of viscous substance 2, moving 113 the substrate 5 to the printing position 11 , and emitting 115 the beam of electromagnetic radiation 23 may be repeated for providing the viscous substance 2 to predetermined positions on the product 3.

[0087] Fig. 8 shows the method 101 as disclosed in Fig. 7, the method 101 further comprising a step of heating 123, by the heating device 49, the viscous substance 2. The step of heating 123 is done before the step of emitting 115. Preferably, the selective layer-part 27 of the viscous substance 2 on the substrate 5 is heated by the heating device 49.

[0088] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the present disclosure, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or component may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof.

[0089] The foregoing description provides embodiments of the present disclosure by way of example only. The scope of the present disclosure is defined by the appended claims. One or more of the objects of the present disclosure are achieved by the appended claims.

Claims

CLAIMS1. An apparatus (1) for printing a viscous substance (2), preferably solder paste or a conductive glue, by means of Laser Induced Forward Transfer (LIFT), on a product (3), the apparatus (1) comprising: a substrate handler (4) arranged for holding a substrate (5) and positioning a first surface (7) of the substrate (5) into a coating position (9) and a printing position (11), wherein, in the printing position (11), the first surface (7) of the substrate (5) is at a predetermined position relative to a first surface (12) of the product (3) for printing the viscous substance (2), by means of Laser Induced Forward Transfer (LIFT), on the product (3); a support (13) for positioning the first surface (12) of the product (3) in relation to the first surface (7) of the substrate (5) in the printing position (11) of the substrate (5); a coater (15) arranged for providing a layer (17) of viscous substance (2) on the first surface (7) of the substrate (5) in the coating position (9) of the substrate (5); a printing device (19) comprising a first emitter unit (21) arranged for transmitting a beam of electromagnetic radiation (23) for printing, in the printing position (11) of the substrate (5), the viscous substance (2), by means of Laser Induced Forward Transfer (LIFT), on the first surface (12) of the product (3); a scanning device (25) arranged for scanning the beam of electromagnetic radiation (23) across the first surface (7) of the substrate (5) for printing a selective layer-part (27) of the viscous substance (2), by means of Laser Induced Forward Transfer (LIFT); a control unit (29) communicatively coupled with the substrate handler (4) and / or the support (13); the apparatus (1) further comprising at least one of: a warping system (31) arranged for introducing a predetermined warp of the first surface (12) of the product (3), wherein the control unit (29) is arranged for controlling the substrate handler (4) and / or the support (13), based on the predetermined warp, for positioning, during printing, a part of the selective layer-part (27) that is to be printed at a predetermined distance from a location at the first surfacelayer-part (27) is to be printed; and a measuring device (33) arranged for measuring a warp of the first surface (12) of the product (3), wherein the control unit (29) is arranged for controlling the substrate handler (4) and / or the support (13), based on the warp measured by the measuring device (33), for positioning, during printing, a part of the selective layer-part (27) that is to be printed at a predetermined distance from a location at the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layerpart (27) is to be printed.

2. The apparatus (1) according to claim 1 , wherein the apparatus (1) further comprises at least the other of the warping system (31) and the measuring device (33), wherein the control unit (29) is arranged for controlling the substrate handler (4) and / or the support (13), based on the predetermined warp and the warp measured by the measuring device (29), for positioning, during printing, the part of the selective layerpart (27) that is to be printed at the predetermined distance from the location at the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed.

3. The apparatus (1) according to claim 2, wherein the control unit (29) is further arranged for controlling, based on the warp measured by the measuring device (33), the warping system (31) for introducing the predetermined warp.

4. The apparatus (1) according to claim 1 , 2 or 3, wherein the warping system (31) is further arranged for maintaining the predetermined warp during printing.

5. The apparatus (1) according to any of the preceding claims, wherein the apparatus (1) comprises a gap control module (45) arranged for controlling a printing gap between the substrate (5) and the product (3) based on the warp measured by the measuring device (33).

6. The apparatus (1) according to claim 5, wherein the gap control module (45) is arranged for bringing the substrate (5) at the predetermined position relative to the first surface (12) of the product (3).

7. The apparatus (1) according to any one of the preceding claims, wherein the warping system (31) is further arranged for introducing a convex warp in at least one direction of the product (3) seen from the side of the first surface (12) of the product (3).

8. The apparatus (1) according to any one of the preceding claims, wherein the warping system (31) comprises a clamping arrangement (35) for clamping the product (3) at predetermined locations of the product (3), preferably at predetermined locations at one or more edges of the product (3), for introducing the predetermined warp.

9. The apparatus (1) according to claim 8, wherein the clamping arrangement (35) comprises a pre-formed frame or two or more clamps and / or pins, preferably two or more clamps and / or pins, such as four or six clamps and / or pins.

10. The apparatus (1) according to claim 8 or 9, wherein the clamping arrangement (35) further comprises means for creating a vacuum for fixating the product (3) in the warping system (31), such as a vacuum pump, a suction cup, or a venturi device.

11. The apparatus (1) according to any one of the preceding claims, wherein the measuring device (33) is arranged for measurement of a topography of the first surface (12) of the product (3) and arranged for determining, based on the topography measured, the warp of the first surface (12) of the product (3).

12. The apparatus (1) according to any one of the preceding claims, wherein the control unit (29) is further arranged for controlling the substrate handler (4) and / or the support (13) for positioning, during printing, a part of the selective layer-part (27) that is to be printed substantially parallel, preferably parallel, to a region of the first surface(3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed.

13. The apparatus (1) according to any one of the preceding claims, wherein the support (13) comprises the warping system (31).

14. A method (101) of printing a viscous substance (2) on a product (3), by means of Laser Induced Forward Transfer (LIFT), using an apparatus (1) according to any one of the preceding claims, the method (101) comprising the steps of: providing (103) the substrate (5) and the product (3); supporting (105), by the support (13), the product (3); holding (107) the substrate (5), by the substrate handler (4); moving (109) the substrate (5), by the substrate handler (4), to the coating position (9); providing (111), by the coater (15), the layer (17) of viscous substance (2) on the first surface (7) of the substrate (5); moving (113), by the substrate handler (4), the substrate (5) to the printing position (11); emitting (115), by the first emitter unit (21), the beam of electromagnetic radiation (23) for printing the viscous substance (2), by means of Laser Induced Forward Transfer (LIFT), on the product (3); scanning (117), by the scanning device (25), the beam of electromagnetic radiation (23) across the first surface (7) of the substrate (5) for printing the selective layer-part (27) of the viscous substance (2), by means of Laser Induced Forward Transfer (LIFT); and further comprising at least one of the steps of: warping (119-1), by the warping system (31), the product (3) and introducing (119-2) the predetermined warp of the first surface (12) of the product (3) and controlling (119-3), by the control unit (29), the substrate handler (4) and / or the support (13), based on the predetermined warp, for positioning, during the step of scanning (117), the part of the selective layer-part (27) that is to be printed at the predetermined distance from the location at the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed; andmeasuring (121-1), by the measuring device (33), the warp of the first surface (12) of the product (3) and controlling (121-2), by the control unit (29), the substrate handler (4) and / or the support (13), based on the warp measured by the measuring device (33), for positioning, during the step of scanning (117), the part of the selective layer-part (27) that is to be printed at the predetermined distance from the location at the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed.

15. The method (101) according to claim 14 using the apparatus (1) according to claim 3, wherein, during the step of warping (119-1), the control unit (29) is controlling the warping system (31) based on the warp measured by the measuring device (33), for introducing the predetermined warp.

16. The method (101) according to claim 14 or 15 using the apparatus (1) according to claim 4, wherein, during the step of scanning (117), the warping system (31) maintains the predetermined warp.

17. The method (101) according to any of the claims 14 to 16 using the apparatus (1) according to claim 5, wherein, during the step of scanning (117), the printing gap between the substrate (5) and the product (3) is controlled by the gap control module (45) based on the warp measured by the measuring device (33).

18. The method (101) according to any of the claims 14 to 17 using the apparatus (1) according to claim 6, wherein, during the step of moving (113), the substrate (5) is brought at the predetermined position relative to the first surface (12) of the product (3) by the gap control module (45).

19. The method (101) according to any of the claims 14 to 18 using the apparatus (1) according to claim 12, wherein, during the step of scanning (117), the control unit (29) is controlling the substrate handler (4) and / or the support (13) for positioning the part of the selective layer-part (27) that is to be printed substantially parallel, preferably parallel, to the region of the first surface (12) of the product (3) comprising the locationat the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed.

20. The method (101) according to any of the claims 14 to 19, wherein an accuracy of a distance (d1) between the part of the selective layer-part (27) that is to be printed and the location at the first surface (12) of the product (3) onto which the viscous substance (2) of the part of the selective layer-part (27) is to be printed is in the range of -50 micrometres and 50 micrometres, preferably in the range of -25 micrometres and 25 micrometres, more preferably in the range of -5 micrometres and 5 micrometres.

21. The method (101) according to any of the claims 14 to 20, wherein, during the step of scanning (117), a distance (d2) between a surface (37) of the layer (17) of viscous substance (2) facing away from the first surface (7) of the substrate (5) and the first surface (12) of the product (3) onto which the viscous substance (2) is to be printed is at a predetermined distance in the range of 30 micrometres to 1000 micrometres, preferably in the range of 30 micrometres to 400 micrometres.

22. The method (101) according to any of the claims 14 to 20, wherein one or more of the steps of moving (109) the substrate (5) to the coating position (9), providing (111) the layer (17) of viscous substance (2), moving (113) the substrate (5) to the printing position (11), and emitting (115) the beam of electromagnetic radiation (23) are repeated for providing the viscous substance (2) to predetermined positions on the product (3).

23. The method (101) according to any of the claims 14 to 22, wherein the substrate (5) is substantially transparent, preferably transparent, for the electromagnetic radiation (23) emitted, by the first emitter unit (21), during the step of emitting (115).

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