METHOD FOR JOINING TWO JOIN PARTS USING A PLANAR EMITTER AND A JOINING DEVICE

Abstract

A method for joining a first join part, in particular a cover glass, with a second join part, in particular a housing and/or a display layer of a cover glass display assembly, uses a thermosensitive adhesive that is heated indirectly and/or directly by irradiation with light from a light source, in particular with infrared light and/or visible light, for producing the connection. A planar emitter is used as the light source. The method allows for a fast and secure joining of the join parts.

Claims

1. A method for joining a first join part with a second join part, comprising: joining the two join parts together by means of a thermosensitive adhesive and heating the adhesive indirectly and/or directly by irradiation with light from a light source in the form of a planar emitter, for producing a connection between the two join parts.

2. The method according to claim 1, wherein a strip light source is used as the light source.

3. The method according to claim 1, wherein the first join part, the second join part and/or their joining zone is irradiated with light with a light intensity measured as pulse peak intensity, of maximally 10 W/mm.sup.2.

4. The method according to claim 1, wherein the adhesive is selected from the group consisting of a thermoplastic, a substance with crosslinking constituents and an adhesive comprising a substance with crosslinking constituents.

5. The method according to claim 1, wherein a dye layer that is configured to at least partially absorb light is applied adjacent the thermosensitive adhesive, the dye layer being irradiated by the light source in the step of heating the adhesive.

6. The method according to claim 1, wherein the light source comprises at least two individual light sources.

7. The method according to claim 1, wherein the light source comprises a matrix light source.

8. The method according to claim 1, further comprising the step of masking the light with a masking device along a beam path of the light.

9. The method according to claim 8, further comprising adjusting a size and/or position of a masking window of the masking device.

10. The method according to claim 1, wherein a beam path of the light is formed and/or directed by a lens assembly and/or by a mirror device.

11. The method according to claim 6, wherein at least one individual light source is assigned to each join part.

12. The method according to claim 1, wherein the light source is operated with at least two different power levels during the step of heating.

13. The method according to claim 6, wherein at least one of the individual light sources is operated with a higher individual light power than at least one other of the individual light sources.

14. The method according to claim 1, wherein the two join parts are pressed against each other before, during and/or after the irradiation with light with a joining punch.

15. A joining device configured for joining a first join part with a second join part by means of a thermosensitive adhesive, comprising a light source configured for directly and/or indirectly heating the adhesive by irradiating the adhesive with infrared and/or visible light, wherein the light source is designed as a planar emitter.

16. The joining device according to claim 15, wherein the joining device further comprises a deformable, joining punch for pressing the two join parts against each other.

17. The joining device according to claim 16, wherein the joining punch has at least one force-receiving part which is configured to be acted upon by a contact force (F), and and at least two pressing parts for putting pressure on the first join part, wherein the at least two pressing parts are tiltably arranged and/or configured on the joining punch independently of one another relative to the force-receiving part.

18. The method according to claim 1, wherein the first join part is a cover glass and the second join part is a housing and/or a display layer of a cover glass display assembly.

19. The method according to claim 1, wherein the light is infrared light and/or visible light.

Description

BRIEF DESCRIPTION OF THE EMBODIMENTS

[0048] FIG. 1 provides a schematic representation of a joining device with an assembly with two join parts to be joined as a cross-sectional view;

[0049] FIGS. 2 to 6 provide schematic representations of joining devices with differently configured beam paths;

[0050] FIGS. 7 and 8 provide schematic side and front views of a joining device with a matrix light source;

[0051] FIG. 9 provides a schematic side view of a further improved embodiment of a joining device;

[0052] FIGS. 10 and 11 provide schematic plan views of a joining device which may be adapted to the shape of the join parts to be joined;

[0053] FIGS. 12 and 13 provide a schematic partial side view and a flat pattern view on a further joining device that is adaptable to the shape of the join parts to be joined;

[0054] FIG. 14 provides a schematic cross-sectional view of a joining punch of a joining device and

[0055] FIG. 15 shows a schematic representation of the method according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] FIG. 1 shows an assembly 10 with a first join part 12 and a second join part 14. Assembly 10 is a cover glass display assembly of a smartphone. In particular, the first join part 12 is a cover glass of the smartphone. The second join part 14 is part of a housing of the smartphone. The two join parts 12, 14 are to be joined to each other by an adhesive 16. The adhesive 16 is a TAA.

[0057] A dye layer 18 is applied to the underside of the first join part 12 and adjacent to the adhesive 16. The adhesive 16 and the dye layer 18 are thus located in a joining zone 19.

[0058] While the first join part 12 is substantially transparent to light in the wavelength ranges of visible light and near infrared, in particular in the range 800-1100 nm, the dye layer 18 is nontransparent in these wavelength ranges. It thus absorbs light from these wavelength ranges.

[0059] Light 20, in particular in the aforementioned wavelength ranges, may be generated by a light source 22 designed as a strip light source and irradiated in the direction of the assembly 10. The light source 22 in particular generates a strip-shaped light. For this purpose, the light source 22 is designed as a VCSEL array. The light output it generates as well as the radiated light distribution may be adjusted.

[0060] It can be seen that in order to join the two join parts 12, 14, the light 20 passes through the first join part 12 and is absorbed by the dye layer 18. The dye layer 18 heats up and thus the adhesive 16 heats up as well. Alternatively, it is also conceivable that the dye layer 18 is dispensed with. In such a case, it is advantageous if at least one layer below the dye layer 18, for example the adhesive 16, is configured to absorb the light 20.

[0061] By means of a joining punch 24, the first join part 12 may be pressed against the second join part 14 with a contact force F. To do so, the second join part 14 is fixed on a workpiece carrier 26. The workpiece carrier 26 may be arranged in a stationary manner. The joining punch 24 is, in particular, configured to uniformly apply the contact force F across a wide area, i.e. across a larger area of the first join part 12.

[0062] The light source 22, the joining punch 24, as well as the workpiece carrier 26 are components of a joining device 28. Apart from the parts mentioned, the joining device 28 also comprises further parts, which are not shown in FIG. 1 for simplification reasons. In particular, the joining device 28 comprises a handling device with which the join parts 12, 14 are positioned, and with which they are, in particular, inserted into the joining device 28 for processing and from which they can be removed after the completion of a joining operation. The joining device 28 also has a controller for controlling the different components. The control unit is, in particular, configured to carry out the method according to the invention by means of the joining device 28. The joining device 28 may, for example, also have a masking device for fine-tuning of the exposure. It may have one or more, in particular optical, sensor units for detecting a temperature, for example the temperature of one or both join parts. At least one of the sensor units may be reflected into the beam path of the light 20. Alternatively or additionally, at least one of the sensor units may be arranged along an optical path deviating from the beam path of the light 20. For example, the at least one sensor unit may monitor the joining region from a viewing position located outside the beam path of the light 20. The joining device may also comprise a motor and/or a sensor unit for the, in particular active, alignment of the masking device and/or the light source 22 relative to the first and/or second join part 12, 14.

[0063] FIG. 2 to FIG. 6 now show different embodiments of joining devices 28. The joining devices 28 differ, in particular, by the respective course of the beam paths of the light 20.

[0064] In the embodiment shown in FIG. 2, the light 20 is guided rectilinearly from the light source 22 to the assembly 10 to be exposed.

[0065] For shading areas to be protected of the assembly 10 or, respectively, of the smartphone, a masking device 32 is arranged in the beam path of the light 20, in particular close to the assembly 10. The masking device 32 has a masking window 33 through which light 20 can pass. The masking window 33 may have a slit-like design and/or have a varying slit width, in particular transversely to the image plane of FIG. 2.

[0066] In the embodiment according to FIG. 3, which largely corresponds to the embodiment according to FIG. 2, a lens assembly 30 is additionally arranged in the beam path of the light 20 in order to reduce scattering losses and to protect components of the smartphone or the assembly 10 which are not to be heated. The lens assembly 30 corresponds in its cross section to a convex lens. It has, just as the light source 22, an elongated shape which is transverse to the image plane of FIG. 3. It may be configured to displace the light 20, in particular along a longitudinal and/or a transverse direction, in order, for example, to avoid collisions in the installation space of different components, in particular of the joining device 28.

[0067] In a preferred embodiment of the invention, a glass pane which is transparent, in particular for the light 20 (not shown in FIGS. 1 to 9 for simplification reasons), may furthermore be placed in the beam path of the light 20. The glass pane makes it possible to form a closed contour around the joining punch 24. Thus, the light source 22 can already be moved to another assembly 10 to be joined, for example, in this or another joining device 28, so that it can illuminate the other assembly 10 while the joining punch 24 still remains with the first assembly 10 for a remaining pressure application period. Thus, for example, the utilization of the light source 22 can be increased, in particular during cooling processes of the join parts 12, 14.

[0068] The joining device 28 according to FIG. 4 is essentially configured in accordance with the joining device 28 shown in FIG. 3. This joining device 28, however, additionally comprises a mirror device 34 with which the light beam 20 is guided at an angle. Thus, the light source 22 can be positioned substantially at will, for example, depending on space requirements. The mirror device 34 is arranged between the lens assembly 30 and the masking device 32.

[0069] In the embodiment of the joining device 28 shown in FIG. 5, a lens assembly 30 (FIG. 4) can be dispensed with since the mirror device 34 is designed as a curved mirror. The mirror device 34 thus assumes both the directing and the beam-forming functions.

[0070] In the joining device 28 shown in FIG. 6, the masking device 32 is located between the light source 22 and the mirror device 34. This arrangement of the masking device 32 provides greater clearance in an area of an upper surface of the assembly 10. This additional clearance can be used, for example, to arrange the joining punch 24 (FIG. 1).

[0071] FIGS. 7 and 8 show schematic views of a further embodiment of a joining device 28, but FIGS. 7 and 8 only show the parts of the joining device 28 that are important for explanatory purposes. FIG. 7 shows a schematic side view of the joining device 28, and FIG. 8 shows a schematic front view of the light source 22 of the joining device 28.

[0072] In this embodiment, the light source 22 is formed from a plurality of individual light sources 36. The individual light sources 36 are arranged at regular intervals and, in particular, distributed across a wide area. As a result of this arrangement, it is possible, as can be seen in FIG. 8, to produce a virtually seamless light pattern with a largely homogeneous light distribution of the light 20.

[0073] In order to make this arrangement of the individual light sources 36 possible in terms of space, the masking device 32 and the mirror device 34 are each constructed from a plurality of individual elements. In particular, each individual light source 36 is assigned a single mask 38 and a single mirror surface 40 or respectively arranged in the respective beam path of the respective individual light source 36. Each individual mask 38 thus delimits or respectively masks the beam path of the individual light source 36 assigned to it. In this exemplary embodiment, the individual masks 38 are each designed in two parts so that a slit-shaped masking window is formed between their individual mask parts. However, it is also conceivable to form the individual masks 38 in one piece with a, in particular slit-shaped, preferably centered, masking window.

[0074] The individual elements 38, 40, in particular, make it possible that all the individual light sources 36 irradiate into the assembly 10 or into the joining zone 19 virtually without any scattering losses.

[0075] FIG. 8 shows that the light source 22 protrudes beyond the assembly 10 along its longitudinal direction L. To adapt the light distribution to the join parts 12, 14 of the assembly 10 to be joined, the individual light sources 36 which protrude beyond the assembly 10 in the longitudinal direction L may be operated at a lower power or generally at a different power than the single light sources 36 that are arranged directly above the assembly 10.

[0076] A further development of the joining device 28 according to FIG. 7 or FIG. 8 is shown in FIG. 9.

[0077] It can be seen, in particular, that the mirror device 34 with its individual mirror surfaces 40 extends along a horizontal direction x at most to an edge K of the joining zone 19. In other words, the mirror device 34 does not protrude beyond the edge K. To this purpose, the individual mirror surfaces 40 are suitably curved, in particular more curved in comparison with FIG. 7.

[0078] As will be explained in more detail below, a plurality of such arrangements or joining devices 28 can be positioned side by side and collision free as partial joining devices 42 and be used as a joining device 28 adaptable to different assemblies 10 (FIG. 1) to be processed of, for example, different smartphones.

[0079] Consequently, FIGS. 10 and 11 show such an adaptable embodiment of a joining device 28 and its use for two differently sized assemblies 10.

[0080] It can be seen that the assemblies 10 to be processed according to FIG. 10 or FIG. 11 are each rectangular or at least substantially rectangular.

[0081] The joining device 28 has four partial joining devices 42, which respectively correspond to the partial joining device 42 according to FIG. 9, in particular with the light source 22, the masking device 32 and the mirror unit 34. The joining device 28 can thus produce light 20 with a light pattern consisting of four strips.

[0082] Each partial joining device 42 and thus each strip of light 20 can be displaced in one direction each. As indicated in FIG. 11 by means of double arrows, these directions are each oriented perpendicular to each other.

[0083] Because the individual mirror surfaces 40 (FIG. 9) extend as far as the respective edge K (FIG. 9), the light 20 with its four strips outshines in each position of the partial joining devices 42 an (at least almost) seamless, essentially rectangular annular surface.

[0084] Thus, by moving the partial joining devices 42 and thus the strips of light 20, the size and shape of the generated light pattern can be adapted to the particular assembly 10 to be processed.

[0085] The embodiment of a joining device 28 illustrated in FIGS. 12 and 13 also allows for such an adaptability with an (almost) seamless irradiation of a substantially rectangular annular surface.

[0086] This joining device 28 in turn has four partial joining devices 42, which in turn are arranged to be displaceable, in particular collision free, in parallel or at least substantially parallel to the upper side of an assembly 10 to be joined.

[0087] FIG. 12 shows a schematic partial side view of the joining device 28. For simplicity, only two of the four partial joining devices 28 are shown in FIG. 12. FIG. 13 shows a schematic flat pattern view of the joining device 28 with the four partial joining devices 42 shown here in the flat pattern form.

[0088] Each of the partial joining devices 42 is in turn configured as a strip light source and projects light 20 onto the assembly 10. In the assembled state, i.e. in the original state that the flat pattern view shown in FIG. 13 is based on, the partial joining devices 42 are arranged perpendicular to each other according to a plan view.

[0089] In addition, as shown particularly in FIG. 12, the partial joining devices 28 are tilted in this embodiment with a tilting angle against the direction z, so that a collision with another partial joining device 28 can be avoided when one of the partial joining devices 28 is displaced.

[0090] As can be seen as well, for example, in FIG. 12, the inclination by the inclination angle also makes it possible for the light 20 to outshine an (at least almost) seamless surface.

[0091] In this joining device 28, the mirrors within the partial joining devices can be dispensed with. Intensity gradients of the light 20 which may occur, in particular at the edges of the respective beam paths, may be avoided or removed by suitable masking devices 32 (see FIG. 2 for example).

[0092] The joining device 28 may, in particular in the embodiments described above, have at least one, in particular deformable, joining punch 24 (FIG. 1).

[0093] Such a deformable joining punch 24 is shown in FIG. 14 in a schematic representation.

[0094] The joining punch 24 has a force-receiving part 44 which can be acted upon by the contact force F along a direction z orthogonal to the direction x. The force-receiving part 44 is formed as a bar and has approximately in the middle a force-receiving point 46 onto which the contact force F is applied in a joining operation.

[0095] Below the force-receiving part 44, a plurality of load-guiding parts 48 is hierarchically arranged in several planes, in this case in two planes. The load-guiding parts 48 are also designed as bars.

[0096] The load-guiding parts 48 are tiltably arranged via hinge parts 50 on the respective element located above them, i.e. on a load-guiding part 48 or on the force-receiving part 44 located above them. They are thus tiltably arranged relative to the force-receiving part 44 on the joining punch 24.

[0097] Two pressing parts 52 are arranged on each of the load-guiding parts 48 in the lowest plane. In the situation shown in FIG. 14, the joining punch 28 contacts with the pressing parts 52 the first join part 12 which is to be pressed against the second join part 14 (FIG. 1).

[0098] Due to the tiltable arrangements of the load-guiding parts 48, the pressing parts 52 are tiltably arranged on the joining punch 24, at least independently of the pressing parts 52 that are arranged on the respective other load-guiding parts 48, relative to the force-receiving part 44. It is conceivable that, as an alternative or in addition, the pressing parts 52 are directly tiltably arranged, in particular mounted, on the respective load-guiding parts 48 of the lowest plane.

[0099] This capacity to tilt causes the joining punch 24 to be deformable. It may, when the two join parts 12, 14 are pressed against each other, adapt in particular to the surface geometry of the first join part 12, which may have changed itself and may be irregular under certain circumstances due to the joining process, and thus cause a more evenly distributed or adjustably distributed introduction of the contact force F or, respectively, of generated contact pressures; to this purpose, the distributions of the contact force F or of the contact pressures may be adjusted in particular by making adaptations to the shape and/or dimensions of the components of the joining punch 24.

[0100] For clarity reasons, the deformations of the first join part 12 during the joining process are significantly enlarged in FIG. 14.

[0101] It can be seen that when the force-receiving part 44 is acted upon by the contact force F, the pressing parts 52 press with partial forces F1 to F8 onto the first join part 12 at their respective contact points or transfer the respective partial forces F1 to F8 to it.

[0102] As a result of the tiltable arrangements of the load-guiding parts 48, the load-guiding parts 48 can tilt in such a way that all the pressing parts 52 rest on the first join part 12 despite its deformations. Thus, it is possible to apply a uniform force onto the first join part 12.

[0103] FIG. 15 will now be used to explain the steps of the method 100 according to the invention in more detail below. To this purpose, reference is made once again to the reference numerals of the figures described above to identify the elements of the joining device used.

[0104] In a first step 102, the assembly 10 of the joining device 28 to be processed, which, for example, has the embodiment according to FIGS. 10 and 11, is provided. In particular, the join parts 12, 14 together with the (thermosensitive) adhesive 16 are introduced into the joining device 28 and locked in position.

[0105] The required contact pressure F or the required pressure distribution is built up in this step 102 by means of the joining punch 24.

[0106] Then, in a step 104, the masking device 32 is set up, in particular adjusted; in particular, the size of its masking window 33 is adapted to the assembly 10 to be processed. Alternatively or additionally, the masking device 32 may also be set up in advance, in particular during an initial setup step.

[0107] Furthermore, the light distribution or the emission characteristic of the light source 22 is adjusted. The adjustments of the masking device 32 and/or the light distribution of the light source 22 may be carried out, for example, analogously to the procedure illustrated in FIGS. 10 and 11. In particular, one or more partial joining devices 42 may be displaced for this purpose.

[0108] If the adhesive 16 is an LAA or a TAA, it must first be heated to a wetting temperature T1 or up to a melting temperature, and this wetting temperature T1 should be kept at least approximately over a wetting time dt1. At this wetting temperature T1, the adhesive initially wets the two join parts 12, 14 adjacent to it.

[0109] To ensure that the chemical reactions required for the establishment of the connection properties are triggered or take place in such an adhesive 16 designed as a TAA, such an adhesive 16 must subsequently be heated to a reaction temperature T2. The reaction temperature T2 must then at least approximately be held over a reaction time dt2. Then, the adhesive 16 is cooled over a cooling time dt3 until it reaches a removal temperature T3.

[0110] The temperatures T1, T2, T3 and the times dt1, dt2, dt3 are selected, in particular, depending on the materials used, in particular the adhesive 16 and/or the join parts 12, 14.

[0111] In a step 106, therefore, the light source 22 is operated for a short time with high power or intensity, causing the adhesive 16 to be heated indirectly by irradiating the dye layer 18 with light 20 until the adhesive 16 reaches the wetting temperature T1. An intensity of about 1 W/mm.sup.2 is generated, for example. After reaching the wetting temperature T1, the power or intensity of the light source 22 is temporarily reduced in order to at least approximately maintain the wetting temperature T1 over the wetting time dt1.

[0112] If the adhesive 16 is a TAA, the light source 22 is reused during a next step 108 until the adhesive 16 reaches the reaction temperature T2. In particular, the light source 22 can be operated with increased power. This increased power or intensity is, in turn, used for a comparatively short period of time. Then, the power or intensity of the light source 22 is again reduced to at least approximately keep the reaction temperature T2 over the reaction time dt2. Meanwhile, the two join parts 12, 14 are still pressed against each other or, respectively, the contact force F is still maintained by means of the joining punch 24.

[0113] If the adhesive 16 is a thermoplastic, for example a LAA, step 108 may be omitted and the method continued immediately at step 110.

[0114] Finally, in a last step 110 the temperature is reduced from the reaction temperature T2 to the removal temperature T3 over the cooling time dt3. The assembly 10 may then be removed from the joining device 28 and processed further, for example.

[0115] In a variant of the method, a plurality of method steps, in particular method steps 106 and 108, are not performed on the same joining device 28 and/or at least not by means of the same light source 22, but a plurality of joining devices 28 and/or different light sources 22 are used. A laser or a laser scanner may be used, for example, instead of a light source 22 in the form of a planar emitter for the heating to the temperatures T1 and/or T2.

[0116] It is also conceivable in order to maintain a temperature, in particular the wetting temperature T1 and/or the reaction temperature T2, to provide a thermal insulation and/or to supply thermal energy from the outside, for example via the workpiece carrier 26 and/or the joining punch 24 instead of or in addition to a reduced power supply by the light source 22.

[0117] Furthermore, a joining device 28 is conceivable which is adapted to join more than one assembly 10 or more than one pair of join parts 12, 14 to be joined together. In connection with such a joining device 28, a variant of the method 100 according to the invention is to join several assemblies 10 or pairs of join parts 12, 14 to be joined together simultaneously or alternately.

REFERENCE CHARACTERS

[0118] 10 Assembly [0119] 12 Join part [0120] 14 Join part [0121] 16 Adhesive [0122] 18 Dye layer [0123] 19 Joining zone [0124] 20 Light [0125] 22 Light source [0126] 24 Joining punch [0127] 26 Workpiece carrier [0128] 28 Joining device [0129] 30 Lens assembly [0130] 32 Masking device [0131] 33 Masking window [0132] 34 Mirror device [0133] 36 Single light source [0134] 40 Single mirror surface [0135] 42 Partial joining device [0136] 44 Force-receiving part [0137] 46 Force-receiving point [0138] 48 Load-guiding part [0139] 50 Hinge part [0140] 52 Pressing part [0141] 100 Method [0142] 102 Step [0143] 104 Step [0144] 106 Step [0145] 108 Step [0146] 110 Step [0147] dt1 Wetting time [0148] dt2 Reaction time [0149] dt3 Cooling time [0150] F Contact force [0151] F1 to F11 Partial force [0152] K Edge [0153] T1 Wetting temperature [0154] T2 Reaction temperature [0155] T3 Removal temperature [0156] x Direction [0157] z Direction [0158] Tilting angle