Method and apparatus for focusing a viscous medium dispensed from an output opening of an output device of a jet device

Abstract

Method for focusing a viscous medium dispensed from an output opening (3) of an output device (2) of a jet device (1), wherein at least one gas stream (11) is directed onto the viscous medium between the output of the viscous medium and the impact of the viscous medium on a substrate (4), wherein the viscous medium is focused by means of the gas stream (11), wherein the gas stream (11) is guided such that it rotates around the viscous medium, characterized in that the gas stream (11) passes through at least one gas outlet (9) of a nozzle device (7) before the gas stream (11) impacts the viscous medium, and that the nozzle device (7) has an opening (8) for the viscous medium and the nozzle device (7) rotates around the opening (8) for the viscous medium.

Description

Prior ArtThe invention relates to a method for focusing a viscous medium discharged from a discharge opening of a jet device according to the preamble of claim 1.A method according to the preamble of claim 1 is known from DE 29 24 174 A1. In this case, an annularly formed gas stream is generated, which surrounds and focuses a jet of adhesive emerging from a nozzle.Furthermore, it is known from DE 35 05 619 A1 to surround a media jet emerging from a nozzle by means of air streams emerging from a plurality of air nozzles aligned in the longitudinal direction of the media jet in the circumferential direction and to interfere with the media jet by means of at least one additional air nozzle in order to achieve a speckle effect. The latter at least one air nozzle thereby impinges with a circumferential component on the media jet.DE 23 56 229 A1 discloses an atomizing nozzle having one or more passages for the material or a liquid to be atomized and for at least one propellant gas which forms a gas vortex outside the atomizing nozzle.Jetting is known for the contactless metering of droplets of a viscous medium, for example an adhesive or a solder, onto a substrate. An apparatus and a method for jetting drops are known, for example, from WO1999 / 064167A1. Herein, the viscous medium is located in a dispensing chamber and is jetted from a dispensing valve by a rapid reduction in the volume of this dispensing chamber.Disclosure of the InventionThe method according to the invention for focusing a viscous medium dispensed from a dispensing opening of a jet device offers the advantage that focusing of the viscous medium is achieved when a single gas stream is used. This is achieved by rotating the gas stream around the viscous medium. In this way, with a correspondingly fast rotation of the gas flow around the viscous medium, it can be achieved that with only one gas flow, by rotating around the viscous medium, for example satellites, which can arise in all directions around the viscous medium, can be directed into the main droplets of the viscous medium. Due to the fact that only one gas stream can be used when the gas stream rotates around the viscous medium, it can be achieved that the gas is brought to a particularly high speed at the same flow rate of the supplied gas compared with arrangements with a plurality of gas streams. Accordingly, a further advantage of this arrangement is that in this case it is not necessary to divide the gas stream into a plurality of partial gas streams which would then have a correspondingly lower flow speed.The measures listed in the subclaims make possible advantageous refinements and improvements of the method specified in the main claim for focusing a viscous medium dispensed from an outlet opening of a jet device.It is particularly advantageous if the discharge opening is detected by the gas flow. As a result, the gas stream can be used at the same time to clean the dispensing opening, for example, of residues of the viscous medium which have remained at the dispensing opening.It can also be achieved by the discharge opening being captured by the gas flow that satellite formation is suppressed already during the discharge operation, since secondary droplets which would form during the tearing away of the viscous medium from the discharge opening remain directly in the main droplet.Alternatively, it is also particularly advantageous if the discharge opening is not detected by the gas flow. In this case, a particularly exact manipulation of the shape of the viscous medium by means of the gas flow is possible, since turbulence or similar disturbances do not arise as a result of the gas flow striking the discharge opening.In this case, the impingement of the gas stream on the viscous medium can furthermore be effected in a targeted manner only shortly above or in the region of the impingement of the viscous medium on the target location on a substrate. As a result, the shape and the diameter of the viscous medium which it has after impingement on the substrate can be adjusted particularly exactly.In an advantageous development of the method according to the invention, the gas stream consists of a plurality of partial gas streams. This allows a particularly exact manipulation of the shape and direction of the viscous medium. Furthermore, as a result, shapes that deviate from a round shape of the viscous medium after it has hit the substrate can also be adjusted in a particularly simple manner, such as an oval or line-like shape.It is particularly advantageous if the gas stream passes at least one gas outlet of a nozzle device before the gas stream impinges on the viscous medium. The direction and the shape of the gas flow can be adjusted particularly specifically by the nozzle device or the gas outlets of the nozzle device.The nozzle device can furthermore have an opening for the viscous medium. This has the advantage that the nozzle device can be mounted directly on or in the vicinity of the dispensing opening of the jet device without the nozzle device being in the way of the viscous medium.In this case, it is particularly advantageous if the gas stream is divided into a plurality of partial gas streams by a plurality of gas outlets located in the nozzle device. This achieves the effect that not a plurality of devices for generating a gas stream are required, but rather only one device for generating a gas stream which is subsequently divided into a plurality of partial gas streams by the nozzle.A possibility, which can be realized with particularly simple means, of setting the gas stream or the partial gas streams in rotation around the viscous medium is achieved in the case that the nozzle device has an opening for the viscous medium by the nozzle device rotating around the opening for the viscous medium.The device according to the invention for focusing a viscous medium discharged from a discharge opening of a jet device likewise has the advantages mentioned above.Exemplary EmbodimentDRAWINGSExemplary embodiments of the invention are illustrated in the drawings and are explained in more detail below. The following are shown: FIG. 1 is a cross-sectional view of a viscous medium dispenser of a jet device with an apparatus for carrying out the method of the present invention FIG. 2 shows cross sections of nozzle devices with different geometries.DESCRIPTION OF THE EMBODIMENTFIG. 1 shows a detail of a jet device 1. The jet device 1 has a dispensing device 2 for dispensing the viscous medium, for example in the form of a jet valve, a jet needle or a jet nozzle. In particular, this can be a tappet valve, a resonant pressure valve or an aerosol jet valve.The invention is described below without limiting generality using a jet valve as output device 2.The viscous medium is discharged from a discharge port 3 of the discharge device 2. Typical diameters of the dispensing opening 3 of the dispensing device 2 are in the range between 50 and 4000 μm.The viscous medium can be, for example, a fixing adhesive or a conductive adhesive. Silver conductive adhesives, for example, such as the commercially available PC3001 from Heraeus or Ablebond 84-1 LMI SR4 from Henkel, are used as conductive adhesive.The viscous medium is discharged in the form of droplets from the discharge opening 3 of the jet valve and, after a flight phase, impinges on a substrate 4.Depending on the shape of the dispensing opening 3 and depending on whether the substrate 4 remains static or is moved, different geometries of the viscous medium can be adjusted at the point of impingement on the substrate 4. For example, it is conceivable to use dispensing devices 2 with one or more dispensing openings 3.It can also be seen from FIG. 1 that a device 5 for focusing the viscous medium discharged from the discharge opening 3 of the jet device 1 is attached to the jet valve. The fastening to the jet valve is preferably effected via a screw clamping connection 6 to the jet valve.However, constructions are also conceivable in which the device 5 for focusing the viscous medium is not fixedly attached to the jet valve. For example, the device 5 for focusing the viscous medium can be rotatably mounted around the jet valve by ball bearings mounted on the jet valve. This can be realized, for example, by mounting ball bearings on the device 5 according to the invention, which are received by a flange, which in turn can be fastened to the dispensing device 2. It is also possible that the device 5 for focusing the viscous medium is not mounted on the jet valve, but rather separately therefrom.It can further be seen from FIG. 1 that the device 5 for focusing the viscous medium preferably comprises a nozzle device 7. In this exemplary embodiment, the nozzle device 7 has two continuous gas outlets 9. The gas outlets 9 serve for supplying gas in the direction of the medium discharged from the jet valve.The gas can be led directly through the gas outlets 9 or by means of focusing nozzles 10 introduced into the gas outlets 9, the latter being the case in the exemplary embodiment shown in FIG. 1. On the side facing away from the substrate 4, the focusing nozzles 10 are connected to the gas supply. Alternatively, the gas supply can also be attached directly to the gas outlet 9. For example, by conical admission of the gas outlets 9 or of the focusing nozzles 10, the gas stream 11 can be additionally accelerated.The gas can be provided via a domestic network or, for example, via a gas cylinder and, for example, be conducted via a hose system to the gas outlet 9 or the focusing nozzle 10. This is not shown in FIG. 1. Suitable gases are, for example, inert gases such as, for example, nitrogen or alternatively, for example, air.The viscous medium is discharged from the discharge opening 3 of the discharge device 2 of the jet device 1. This takes place in the form of a main drop from which secondary drops can undesirably split off. The main drop and the sub drops fly from the discharge port 3 of the jet device 1 toward the target location on the substrate 4.By means of the device 5 for focusing the dispensed medium, a gas stream 11 or, in the exemplary embodiment shown in FIG. 1, two partial gas streams 12, 13 are generated, which are directed in the direction of the jet axis 14, that is to say the connecting line between the dispensing opening 3 of the jet device 1 and the location of impingement of the viscous medium on the substrate 4.This is achieved by the gas passages in the nozzle device 7 or the focusing nozzles 10 which lead through the nozzle device 7 being inclined at an angle to the jet axis 14. This angle is preferably less than 45° and preferably greater than 3°. A laminar gas flow 11 is preferably generated through the gas passages 9 or the opening of the focusing nozzles 10.During the flight of the viscous medium or of the main drop, the gas stream 11 or in this case the two partial gas streams 12, 13 strike the viscous medium. This directs the secondary droplets into the main droplets.Furthermore, the main drop is compressed, i.e. focused, by the gas stream 11 so that it impinges on the substrate 4 with a smaller diameter at its target location than would have been the case if no gas stream 11 had been directed onto it.In this case, it is not only conceivable for the main drop to be focused uniformly from all directions in order to achieve a round shape of the drop after it has hit the substrate 4. The focusing can also take place, for example, from different directions to different extents by the arrangement of the gas outlets 9, with the result that a geometry of the drop on the substrate 4 deviating from a round shape is established.By means of the arrangement shown in FIG. 1, the drop is brought, for example, into a shape which is elongated perpendicularly to the plane of the paper. Focusing directed onto the plane of the paper does not take place here. If, as in this exemplary embodiment, the focusing of the drop does not take place equally from all directions, the drop can therefore have an even larger diameter when it impinges on the substrate 4 in the directions in which no focusing takes place than would have been the case if no gas stream 11 had been directed onto it.Typical delivery rates for the gas stream 11 are between 20 and 200 cm 3 / min of the gas or air used for the gas stream 11.The nozzle device 7 illustrated in FIG. 1 can be designed in different geometries. For example, this can have two, three or four gas outlets 9. Examples of geometries of the nozzle device 7 are illustrated in FIG. 2.FIG. 2a shows a cross section of the nozzle device 7 as used in the structure shown in FIG. 1. The opening 8 for the viscous medium is located centrally. The two further openings are the two gas outlets 9.FIG. 2 bshows a cross section of a nozzle device 7 with a centrally arranged opening 8 for the viscous medium and three gas outlets 9.FIG. 2 cshows a cross section of a nozzle device 7 with a centrally arranged opening 8 for the viscous medium and four gas outlets 9.FIG. 2 d shows a cross section of a nozzle device 7 with a centrally arranged opening 8 for the viscous medium and a gas outlet 9 which is arranged annularly around the opening 8 for the viscous medium. The viscous medium is focused particularly uniformly from all directions by a gas outlet 9 shaped in this way; a round geometry of the drop results after the drop has hit the substrate 4.In order to ensure that the regions of the nozzle device 7 outside and inside the annular opening of the gas outlet 9 are held together in the nozzle device 7 shown in FIG. 2 d, these are connected to one another by two webs.The webs have the smallest possible width in order not to obstruct the gas flow 11 during the passage through the gas outlet 9. The webs are located in a different plane than the cross-sectional plane shown in FIG. 2 d, so that the webs are not shown in FIG. 2 d.Materials suitable for producing the nozzle device 7 are, for example, metals or plastics. Typical thicknesses of the nozzle device 7 are 1000 to 3000 μm, but greater or lesser thicknesses are also possible. The bores or the gas outlets 9 in the nozzle devices have diameters between 10 and 1000 μm, preferably between 50 and 500 μm.The distance between the dispensing opening 3 of the dispensing device 2 and the substrate 4 is usually in the range of a few millimetres, for example between 0.5 and 3 mm. By means of the device 5 according to the invention, it is possible to further increase the distance between the dispensing opening 3 of the dispensing device 2 and the substrate 4, for example to 5 mm or greater, without losing target accuracy in the process.As a result, it is possible, thanks to the device 5 according to the invention, to apply even small structures of the viscous medium to substrates 4 by way of bets, which structures have a surface unevenness of greater than 3 mm. Such a large surface unevenness usually comprises three-dimensional circuit carriers such as molded interconnected devices, pressure sensors, electrical circuits and flexible electrical circuits.By means of the method according to the invention, it is possible to focus the viscous medium at the target location on the substrate 4 to a diameter of only 50 μm. As a result, it is possible, for example, to jet conductor tracks, for example as a replacement for wire bonds, and contacts of passive and active components with small connection geometries.In the exemplary embodiment illustrated in FIG. 1, the output opening 3 of the jet valve is not located in the gas stream 11, but exemplary embodiments are also conceivable in which the output opening 3 of the output device 2 of the jet device 1 is detected by the gas stream 11. This can ensure that no residues of the viscous medium remain at the dispensing opening 3. The gas stream 11 in this case thus serves for cleaning the dispensing opening 3.Furthermore, in this embodiment, the gas flow 11 can serve to optimize the tear-off behavior of the viscous medium at the discharge opening 3, so that satellite formation does not occur, for example.Depending on the type of application, the viscous medium used and the desired diameter of the viscous medium after encountering the target site, it is possible, for example, to change the angle at which the gas stream 11 is directed onto the viscous medium or else to adapt the number of partial gas streams 12, 13 or, for example, the flow speed.In this case, for example, the volume flow of the gas stream can be 100 cm 3 / min, the nozzle device can have two diametrically arranged gas outlets with an opening diameter of 100 μm, and the gas stream can be inclined at an angle of 30° with respect to the jet axis. As a result, for the above-mentioned, typically used conductive adhesives, a metering distance of between 5 and 8 mm is achieved for a process-safe application of the conductive adhesive to the substrate.

Claims

Method for focusing a viscous medium dispensed from a dispensing opening (3) of a dispensing device (2) of a jet device (1), wherein at least one gas stream (11) is directed onto the viscous medium between the dispensing of the viscous medium and an impact of the viscous medium on a substrate (4), wherein the viscous medium is focused by means of the gas stream (11), wherein the gas stream (11) is guided such that it rotates around the viscous medium, characterized in that the gas stream (11) passes at least one gas outlet (9) of a nozzle device (7) before the gas stream (11) impacts the viscous medium, and in that the nozzle device (7) has an opening (8) for the viscous medium and the nozzle device (7) rotates around the opening (8) for the viscous medium.Method according to claim 1, characterised in that the discharge opening (3) is detected by the gas flow (11).Method according to claim 1, characterised in that the discharge opening (3) is not detected by the gas flow (11).Method according to one of Claims 1 to 3, characterized in that the gas stream (11) is formed from a plurality of part-gas streams (12, 13).Method according to one of the preceding claims, characterized in that the gas stream (11) is divided into a plurality of partial gas streams (12, 13) by a plurality of gas outlets (9) located in the nozzle device (7).Device (5) for focusing a viscous medium dispensed from a dispensing opening (3) of a jet device (1), characterized bya nozzle device (7) for generating a gas stream (11) directed onto the viscous medium, wherein the nozzle device (7) has at least one gas outlet (9) for guiding the gas stream (11) before the gas stream (11) impinges on the viscous medium, and wherein the nozzle device (7) has an opening (8) for the viscous medium and the nozzle device (7) is rotatable about the opening (8) for the viscous medium in such a way that the guided gas stream (11) rotates about the viscous medium.

Images