Method and laser arrangement for electrically contacting terminal faces of two substrates

Abstract

To provide a method for electrically contacting terminal faces of two substrates.SOLUTION: The invention relates to a method for electrically contacting terminal faces of two substrates, a first substrate (02), being positioned against the terminal faces of a second substrate (03), and a first laser radiation (41) being applied to at least one of the substrates (02, 03) on the rear side in a first application phase, and a second laser radiation (51) being applied to at least one of the substrates (02, 03) in a second application phase and a solder material (07) arranged between the substrates (02, 03) being fused at least to such an extent that an electrical contact is established between the terminal faces of the substrates, said terminal faces facing each other, and the application in the first application phase being carried out with a first laser radiation, which has a wavelength that differs from the second laser radiation, and the switch from the first application phase to the second application phase being controlled by a control device (06).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for electrically contacting the terminal surfaces of two substrates according to claim 1. In addition, the present invention relates to a laser device for applying laser energy to at least one of the substrates according to claim 10.

Background Art

[0002] Various methods for connecting or contacting the terminal surfaces of two substrates are already known, and the terminal surfaces are arranged and configured in overlapping positions. In this method, laser energy is used to generate the heat required for connection in the region of the contact pairs formed from the terminal surfaces. For example, a method or device for thermally connecting the terminal surfaces of two substrates is known. In this method or device, an optical fiber is used to introduce laser energy into the contact pairs of the terminal surfaces, and the cross-section of the optical fiber is sized such that simultaneous application of the laser radiation emitted from the end cross-section of the optical fiber to all contact pairs is possible. However, such a method does not allow any targeted application of the laser radiation to individual contact pairs. Furthermore, in this method, the terminal surfaces of the substrates contact each other without any additional compressive load and are fixed in their relative positions only by the self-weight of the upper substrate. Furthermore, it is known that it is possible to perform applying laser radiation to the substrates from the rear side via a transparent pressure plate that brings the terminal surfaces of the two substrates into contact with each other in order to thermally connect the terminal surfaces of the two substrates. In this context, a transparent glass plate is used as the pressure plate.

[0003] Furthermore, a method of directly mounting a semiconductor chip on a carrier substrate is known from the general prior art. For example, there is a method of directly attaching a semiconductor chip to a carrier substrate or a printed circuit board with its terminal surface facing the carrier substrate and with a soldering material previously deposited on the terminal surface of the chip. During reflow soldering, the soldering material coating is remelted in a soldering oven and joined to the terminal surface of the carrier substrate. Such methods are very complex both in terms of their operation and the devices required for them.

[0004] Furthermore, it is known to connect the terminal contacts of two substrates by applying a solder material as a spherical solder material onto the solderable terminal contacts of one substrate by means of a solder ball supply device of a laser soldering system and at least partially melting it by means of a laser device so as to form a material bonding connection between the terminal contacts of the substrates. Alternatively, the solder material located on the terminal contacts can be at least partially melted by heating one substrate in order to form a material bonding connection between the terminal contacts of the substrates after the first substrate is deposited on the second substrate. However, applying thermal energy to the surface of the substrate can cause unwanted burning of the substrate, especially in the case of temperature-sensitive substrates. In a general method, depending on the absorption capacity of the solder material or the substrate, the proportion of laser radiation that can be used to heat the solder material is very small, while a considerable proportion of the radiation is reflected by the solder material or the substrate without contributing to its heating. This actually causes a considerable energy loss, and as a result, the amount of energy required to melt the solder material increases significantly. Summary of the Invention Problems to be Solved by the Invention

[0005] Accordingly, it is an object of the present invention to propose a method and a laser device that enable reliable connection of two substrates by melting a solder material with low energy consumption. Furthermore, the contact of the terminal surfaces of the substrates should be improved, and damage to the substrates to be connected should be avoided. Means for Solving the Problems

[0006] This object is achieved by a method having the features of claim 1 and a laser device having the features of claim 10.

[0007] A method for electrically contacting the terminal surfaces of two substrates according to the present invention, wherein a first substrate whose terminal surface faces a second substrate is electrically and mechanically connected to the terminal surface of the second substrate, the method can be divided into at least three steps: a positioning step, a first application step, and a second application step. In the positioning step, the first substrate is positioned with its terminal surface relative to the terminal surface of the second substrate. Thus, the terminal surfaces of the first substrate and the second substrate can be arranged and configured in overlapping positions for connecting or contacting the first substrate and the second substrate. In the first application step, a first laser emission is applied to at least one of the substrates, i.e., the first substrate or the second substrate, from the rear side using a first laser device. In the context of the present invention, "rear side" refers to the rear side of the substrate, which corresponds to the side of the substrate facing outward from the other substrate. In other words, this means that the rear side of the first substrate is the side of the substrate facing outward from the second substrate, and the rear side of the second substrate is the side of the substrate facing outward from the first substrate. The terminal surfaces of the substrates are arranged and configured on the front side opposite to the rear side of the substrates, and the solder material is arranged and configured between the terminal surface of the first substrate and the terminal surface of the second substrate. The solder material and the substrate, particularly the substrate to which the laser emission is applied using the first laser device, are heated by applying the first laser emission to one of the substrates using the first laser device in the first application step, but the solder material is not yet melted. By heating the substrate and the solder material to a higher temperature level, the absorption capacity of the substrate and the solder material can be increased. This has the advantageous effect that only the additional amount of energy required to heat the solder material to the melting temperature starting from the temperature level reached in the first application step needs to be introduced following the switch to the second application step in which a second laser emission is applied to at least one of the substrates using a second laser device, and the increase in the absorption capacity of the substrate and the solder material after the first application step reduces the proportion of reflection of the laser emission, thereby increasing the effectiveness of the application of the second laser emission.In the second application stage, the solder material disposed between the substrates is melted at least to the extent that electrical contact is established between the terminal surfaces of the first substrate and the second substrate, and the terminal surfaces face each other. Preferably, in addition to establishing electrical contact between the terminal surfaces facing each other, the first substrate is also mechanically fixed on the second substrate. Preferably, the first substrate whose terminal surface faces the second substrate can be directly electrically and mechanically connected to the terminal surface of the second substrate by directly fixing the terminal surface of the first substrate on the second substrate using the solder material pre-applied to the terminal surface of the first substrate.

[0008] In the context of the present invention, the term "solder material" also relates to solderable metal compounds, particularly solderable soft metal compounds, used in the form of, for example, solder paste or solder balls, in addition to Cu-Cu hybrid joints, sintered pastes and / or copper pads for copper pillars. The term "sintered paste" relates to a suspension containing particles of at least one solderable soft conductive material and a solvent.

[0009] In the context of the present invention, in addition to dividing the method according to the present invention for electrically contacting the terminal surfaces of two substrates into a positioning step, a first application step, and a second application step, it has been recognized that it is further advantageous for the application to be carried out in the first application step using a first laser emission having a wavelength different from that of the second laser emission. Thus, the wavelength of each laser emission can achieve efficient preheating of the mating part by applying the first laser emission having the first wavelength to the mating part, while it has been recognized that efficient melting of the solder material can be achieved by applying a second laser emission having a second wavelength different from the first wavelength to the mating part, so that the requirements in the first application step and / or the second application step can be met. This brings the advantage that gentle heating by the first laser emission, which is easily absorbed by various materials, can be carried out in the first application step, and the advantage that the second laser emission, which causes a deeper heating effect in the material of the mating part, especially the solder material, is used only in the second application step. As a result, in particular, thermal damage during the first application step can be prevented. Furthermore, the required laser output of the second laser device can be designed to be initially lower compared to a general laser device due to preheating, on the one hand reducing system costs, and on the other hand making it possible to miniaturize the laser device used in this method. The first laser emission can preferably have a shorter wavelength than the second laser emission. For example, the first laser emission can be in the ultraviolet wavelength range in the first application step, and the second laser emission can be in the near-infrared wavelength range in the second application step.

[0010] Furthermore, in the first laser device during the first application stage, it is conceivable that a lower laser energy input is required than in the second laser device during the second application stage. It is further conceivable that the second laser device for melting the solder material can have a higher output than the first laser device. Due to the increase in the absorption capacity of the mating part in the situation of the first application stage, the output of the second laser device can be significantly reduced compared to a general method having only one application stage. As a result, the second laser device can be controlled more precisely, and thermal damage to the substrate can be prevented. Preferably, due to the lower laser energy input to the solder material and / or the first substrate, the second laser device can have a significantly lower laser output than required when not using the first laser device in the first application stage. However, since the output of the laser source can generally be controlled more precisely in a lower output range than in a higher output range, as a result, more precise control of the second laser device is possible. On the other hand, thermal damage generated especially at a high laser output can be prevented. In particular, the required laser output of the second laser device can also be designed to be initially low, which on the one hand enables reduction of the system cost, and on the other hand enables miniaturization of the laser device used in this method.

[0011] In the context of the present invention, it has been recognized as advantageous that the switching from the first application stage to the second application stage is controlled using a control device depending on the duration of the first application stage, depending on the laser energy introduced into one of the substrates, depending on the temperature of one of the substrates, and / or depending on the temperature of the solder material. In other words, the control device is configured to activate the second laser device based on different measured values or sensor data, and thus trigger the transition from the first application stage to the second application stage.

[0012] The control device can control the switching from the first application stage to the second application stage depending on the duration of the first application stage. This means that when the first laser emission is applied to one of the substrates over a sufficient time period using the first laser device, the switching from the first application stage to the second application stage is triggered by the control device. This is because, assuming a constant laser output throughout the first application stage, the laser energy input can be determined based on the duration of the application and the laser output of the first laser device. When sufficient laser energy has been generated in the connection partners, i.e., the first substrate, the second substrate, and the solder material, the switching from the first application stage to the second application stage can be triggered by the control device.

[0013] Alternatively or additionally, the control device can control the switching from the first application stage to the second application stage depending on the laser energy introduced into one of the substrates and / or the solder material. Compared to control based only on the duration of the first application stage, control depending on the introduced laser energy offers the advantage that it can also take into account the control or variation of the laser output during the first application stage. In this context, it has been recognized that by recording the laser output at any point in time during the first application stage, an accurate calculation of the laser energy input to the connection partners is possible even if the laser output changes during the first application stage.

[0014] Furthermore, alternatively or additionally, the switching from the first application stage to the second application stage can be controlled using a control device depending on the temperature of one of the substrates and / or depending on the temperature of the solder material. The temperature of one of the mating parts can be monitored at least periodically or continuously for this purpose. Thus, when the temperature of the mating part is sufficient and the absorption capacity of the joining partner has increased sufficiently, the switching from the first application stage to the second application stage can be carried out. Preferably, the temperature of the first substrate and / or the solder material is detected and the switching from the first application stage to the second application stage is controlled based on those temperature values. It is also conceivable that the temperature of one of the substrates is measured and the temperature of the solder material is determined taking into account the structure and material of the substrate.

[0015] In the context of the present invention, the term "substrate" is understood to include all components provided with a conductive path structure and an external terminal surface for establishing contact. Thus, for example, a chip, a printed circuit board or a carrier substrate can be a substrate in the context of the present invention. The preferred fields of application of the method proposed here or the fields of use of the device proposed here are also in the fields of flip-chip technology and also surface-mounted device (SMD) technology.

[0016] In the context of the present invention, the term "mating part" refers to the first substrate, the second substrate, and the solder material.

[0017] The term "laser device" can be understood to be a laser emission device for emitting laser radiation alone, or alternatively a laser emission device in combination with a radiation guiding device through which laser radiation is guided from the laser emission device to the mating part. Devices having lenses and / or mirrors are known as radiation guiding devices.

[0018] As a result, the proposed method can be used very generally, for example, to connect different substrates including metallized chips to another substrate. The general use of this method is essentially based on the fact that the two application stages can be very accurately adapted to the mating part. Furthermore, this makes it possible to increase the energy efficiency of the method and minimize damage to the mating part. In particular, it is possible to avoid material destruction such as that which occurs when chips, which are usually made of different materials, are heated in a common manner. In this context, it has been recognized as advantageous that the chips are heated according to a gradient rather than in a stepwise manner.

[0019] Furthermore, in the context of the present invention, it has been recognized that a first laser device can be used to heat the ambient environment in addition to the mating part during the first application stage, thereby improving and simplifying the contact of the opposing terminal surfaces of the first substrate and the second substrate during the second application stage. Furthermore, it has been recognized that an adhesive can be cured using the first laser device and / or the second laser device. In particular, the adhesive can be cured by energy input and the resulting heating of the adhesive. By way of example and not limitation, epoxy compounds, dry films, bis-benzocyclobutene (BCB) compounds, polyimide compounds and / or UV curable compounds can be used as adhesives.

[0020] Advantageous embodiments of the present invention are the subject matter of the dependent claims. Furthermore, all combinations of at least two of the features disclosed in the present specification, the claims and / or the drawings are within the context of the present invention. All features and embodiments disclosed with respect to the method are also understood to relate, not identically but in an equivalent manner, to a laser device according to the present invention. In this context, linguistically common conversions and / or similar substitutions of each term in the context of customary language practice, in particular the use of synonyms supported by generally recognized language literature, are specifically understood to be encompassed by the present disclosure without being explicitly mentioned in their respective formulations.

[0021] The temperature of the connection partner can be advantageously measured non - contact. Using a temperature sensor, the radiant temperature of at least one of the substrates and / or the solder material can be measured during at least the first application phase. Then, the switching from the first application phase to the second application phase can be controlled using a control device depending on the radiant temperature of one of the substrates and / or depending on the radiant temperature of the solder material. Advantageously, the temperature sensor can be realized as an infrared pyrometer. Such infrared pyrometers can measure with high precision and speed, and due to their compact structure, they are suitable for applications with limited installation space. They are also relatively lightweight and can be positioned extremely flexibly due to their compact design. For example, the infrared pyrometer can be arranged within the joining tool of a laser device for electrically contacting the terminal surfaces of two substrates. Thus, the infrared pyrometer offers various advantages compared to known infrared cameras for detecting temperature, especially those that are very large and heavy compared to the infrared pyrometer. In particular, the rapid detection of temperature, advantageously performed in less than 1 ms, more preferably in less than 0.3 ms, is a great advantage compared to the relatively slow detection of temperature by infrared cameras, which is usually within the range of 25 ms. Preferably, the radiant temperature of the first substrate and / or the solder material can be measured by the temperature sensor during at least the first application phase, and the switching from the first application phase to the second application phase can be controlled using a control device depending on the radiant temperature of the first substrate and / or depending on the radiant temperature of the solder material.

[0022] In the second application phase, in addition to the application using the first laser device, an application using a second laser device can be performed. Thus, the laser radiation is simultaneously applied to the connection partner by the first laser device and the second laser device in the second application phase. The fact that the application using the first laser device is maintained allows the second laser device to operate at a lower output.

[0023] If the radiant temperature of at least the first substrate, the second substrate, and / or the solder material is measured by the temperature sensor during the first application stage, the radiant temperature of at least the first substrate, the second substrate, and / or the solder material can also be measured by the temperature sensor during the second application stage. Then, the end of the second application stage can be performed depending on the measured radiant temperature during the second application stage of at least the first substrate, the second substrate, and / or the solder material. Thus, the method can be implemented with minimal equipment and control effort.

[0024] The switching temperature at which the switch from the first application stage to the second application stage is triggered can be selected depending on the properties of the substrate and / or solder material being contacted. Thus, the material-specific absorption capacity of the substrate and / or solder material, which changes with the temperature of the material, can be taken into account for the specification of the switching temperature when defining the switching temperature in each case.

[0025] The first laser device can be switched on in a clock-controlled standby mode during a defined duty cycle and can be switched to an operating mode by a control device depending on the ambient temperature of at least one substrate measured by a temperature sensor. In the context of the present invention, the "standby mode" refers to the standby mode of the first laser device, in which mode the actual function of the laser device, i.e., the emission of laser radiation, is temporarily stopped, but it can be activated at any time without preparation or without a longer waiting time. In the context of the present invention, the "ambient temperature" of the substrate is the temperature or temperature change that occurs as soon as the substrate is placed within the measurement range of the temperature sensor. Therefore, since the measurement of the temperature of the substrate requires the presence of the substrate, a temperature sensor can be used to trigger the switching between the first application stage and the second application stage and, if necessary, also to end the second application stage, and it is also possible to use the temperature sensor to detect at least one substrate. Therefore, the temperature sensor makes it possible to trigger the method as soon as the substrate enters the measurement range of the temperature sensor. In particular, the method can be triggered if the temperature of the first substrate can be measured by the temperature sensor during the duty cycle of the first laser device, which is repeated in a clock-like manner, during which the first laser device is in the standby mode. This is because the temperature of the first substrate can only be measured if the first substrate is present, and as a result, the temperature value determined by the temperature sensor or the temperature change determined by the temperature sensor indicates the presence of the first substrate.

[0026] According to a preferred embodiment, in the first application stage, the first laser radiation can be applied to the first substrate from the back side using the first laser device, and then, in the second application stage, the second laser radiation can be applied to the first substrate from the back side using the second laser device. This means that both the first laser radiation and the second laser radiation impinge on the first substrate from the back side, thereby making it possible to make the device for carrying out the method compact.

[0027] According to a further preferred embodiment, in a first application step, a first laser device can be used to apply a first laser radiation to a first substrate on the rear side and to a second substrate on the front side. Subsequently, in a second application step, a second laser device can be used to apply a second laser radiation to the first substrate on the rear side. In the first application step, then, the first laser radiation is applied to both the first substrate and the second substrate. This can be done, for example, such that the first substrate is smaller than the second substrate and the focus of the laser radiation in a direction intersecting the application direction is larger than the first substrate, whereby the first laser radiation not only impinges on the first substrate but also on the second substrate. Further, this has the positive effect that the ambient environment of the mating part, in particular the ambient environment of the first substrate, can be preheated during the first application step. In the second application step, the focus of the second laser beam can be oriented such that the second laser radiation impinges only on the first substrate, and as a result, energy is introduced only into the first substrate.

[0028] According to another embodiment, in a first application step, a first laser device can be used to apply a first laser radiation to a second substrate on the rear side, and in a second application step, a second laser device can be used to apply a second laser radiation to the first substrate. This offers the advantage that no elaborate deflection device or radiation guiding device is required, since, for example, the laser radiation can be applied to the second substrate from below in the first application step and to the first substrate from above in the second application step. Thus, the application of the first laser radiation can also be realized in a simple manner in both the first and the second application steps.

[0029] The activation of the process gas can be carried out or supported using at least a first laser device in a first application stage. In particular, the process gas can be heated by at least a first laser emission. By way of example, and never by way of limitation, argon, oxygen, nitrogen, hydrogen or helium can be used as the process gas. The process gas can be used to create a less reactive and / or reducing ambient environment. The process gas can also be used to discharge the reactive gas after and / or before the process step.

[0030] In a second aspect, the invention relates to a laser device for applying laser energy to at least one substrate, the laser device comprising - at least one first laser device that emits a first laser emission, - at least one second laser device that emits a laser emission having a wavelength different from that of the first laser emission, - a control device configured to operate the second laser device and having a temperature sensor and / or a time sensor and comprising.

[0031] Next, in order to establish electrical contact between the terminal surfaces of the first substrate and the second substrate facing each other, in a first application step, a first laser device can be used to apply first laser radiation to at least one of the substrates on the rear side, while in a second application step, a second laser device can be used to apply second laser radiation to at least one of the substrates. As already explained with respect to the method, due to the connection partner, in particular the preheating of the substrate to which the first laser radiation is applied in the first application step, the absorption capacity of the connection partner can be increased, and thus the output of the laser device used in the second application step can be reduced compared to conventional devices and methods having only one application step. The first laser device can already preheat the substrate and the solder material, but cannot yet melt the solder material. The establishment of electrical contact between the terminal surfaces of the first substrate and the second substrate facing each other is carried out only in a second application step during the application of laser radiation to at least one of the substrates using the second laser device, and the solder material is melted to establish contact. The control device can activate the second laser device, in other words, the switching from the first application step to the second application step can be controlled by a temperature sensor and / or a time sensor. The switching from the first application step to the second application step, which depends on the temperature of one of the substrates and / or on the temperature of the solder material, can be controlled by a temperature sensor. The control device can activate the second laser device depending on the laser energy introduced into one of the substrates and / or depending on the duration of the first application step by a time sensor, and thus control the switching from the first application step to the second application step.

[0032] It is conceivable that the laser device comprises at least one additional laser device, and the additional laser device can emit additional laser radiation having a wavelength different from the first laser radiation and / or the second laser radiation. The laser device can preferably have a third laser device, the third laser device can emit third laser radiation, and the third laser radiation has a wavelength different from the first laser radiation and / or the second laser radiation. The third laser radiation can be applied to the connection partner in a third application stage. The laser device can have a fourth laser device in addition to the third laser device, the fourth laser device can emit fourth laser radiation, and the fourth laser radiation has a wavelength different from the first laser radiation, the second laser radiation, and / or the third laser radiation. This laser radiation can be applied to the connection partner in a fourth application stage. The laser device can comprise any number of additional laser devices.

[0033] The first laser device can have an ultraviolet laser (UV (ultraviolet) laser), and thus can emit UV laser radiation. The second laser device can have a near-infrared laser (NIR (near-infrared) laser), and thus can emit NIR laser radiation. Ultraviolet lasers are known to emit laser radiation in the wavelength range of 200 nm to 400 nm. Furthermore, near-infrared lasers (NIR) are known to emit laser radiation in the wavelength range of 785 nm to 1550 nm. In the context of the present invention, it has been recognized that ultraviolet lasers and the laser radiation emitted thereby are particularly suitable for preheating the connection partner. In contrast, near-infrared lasers, the emitted laser radiation of which is in a wavelength range different from that of the UV laser, are advantageously suitable for melting the solder material for establishing contact between the terminal surfaces in the second application stage.

[0034] It is also conceivable that the first laser device has a diode laser as a radiation source and the second laser device has a pulsed laser as a radiation source. As a result, certain advantages resulting from the implementation of the method according to the invention are already taken into account when selecting the laser device, i.e., for example, a relatively low-power radiation source is used for the first laser device, and the first laser device must only be sufficient to bring the connection partner to a temperature level with increased absorption capacity. The second laser device is realized as a "power laser" compared to the first laser device.

[0035] The laser device can be provided with a bonding tool for positioning and bonding a first substrate on a second substrate. The beam channels for the beam path of the first laser emission and / or the beam path of the second laser emission can be realized within the bonding tool. The first substrate can be positioned by the bonding tool such that its terminal surface faces the terminal surface of the second substrate. The bonding tool can have a holder for removably fixing the first substrate to the bonding tool for this purpose. The first substrate can be held and positioned relative to the second substrate by the holder, and in particular, can be positioned in an overlapping position with the second substrate. Furthermore, in order to improve the connection between the first substrate and the second substrate, it is conceivable that pressure can be applied to the first substrate by the bonding tool. Since the beam channels for the beam path of the first laser emission and / or the beam path of the second laser emission are realized within the bonding tool, the application of the laser emission to at least one substrate can be achieved in a simple manner by the bonding tool. Therefore, the design of the device can be made less complicated, and the laser emission applied through the beam channel of the bonding tool can be directly applied to the rear side of the substrate fixed to the bonding tool. Therefore, there is no need to consider another laser device or another beam channel realized separately from the bonding tool in the surrounding environment of the connection partner, and thereby, since there is no need to consider a collision with another beam channel, the bonding tool can be moved significantly more easily. In other words, the bonding tool thus has significantly more available space, and thereby, the movement distance and position deviation can be minimized.

[0036] The temperature sensor for detecting the emission temperature can be arranged and configured within the beam path of the reflected emission of the first substrate, the second substrate, and / or the solder material. The temperature sensor can be realized as an infrared sensor, preferably a pyroelectric infrared sensor. Thereby, the temperature of the connection partner whose reflected emission is captured can be measured non-contact. The reflected beam generated from the application of the laser emission can be used for temperature measurement by the infrared sensor anyway.

[0037] The temperature sensor can be arranged and configured within the laser device such that the beam path of the reflected radiation intended for temperature measurement, as well as the beam paths of the first laser radiation and the second laser radiation, at least partially, simultaneously progress within the beam channel. Thereby, by realizing just one beam channel, it becomes possible to advantageously shield all beam paths from the ambient environment. Preferably, the beam channel in which the beam path of the reflected radiation and the beam paths of the first laser radiation and the second laser radiation can at least partially progress simultaneously is realized within the joining tool. The infrared sensor can be arranged and configured at the end of the beam channel within the joining tool spaced from the substrate. The end of the beam channel facing the substrate can be realized by a holder that can be used to hold the first substrate. However, it is also conceivable that the beam path of the reflected radiation and the beam path of the first laser radiation at least partially progress simultaneously within a common beam channel, while the beam path of the second laser radiation progresses within a separate beam channel.

[0038] The laser device can have a substrate support that can fix at least the rear side of one of the substrates. The rear side of the second substrate can preferably be fixed to the substrate support. By fixing the rear side of one of the substrates to the substrate support, the positioning of the first substrate relative to the second substrate can be simplified. Preferably, the first substrate or the second substrate is held in a form-fitting manner on the substrate holder such that the lower surface of the held substrate abuts against the substrate holder. Furthermore, it is conceivable to hold the substrate to be held on the substrate holder by generating a holding force. To generate the holding force, a negative pressure can be applied to the substrate abutting against the substrate holder. Thus, the substrate holder enables positioning of the substrate while it is being held.

[0039] An optical window having an optically transparent window body for unobstructed passage of laser radiation and / or reflected radiation to and / or from at least one substrate can be introduced into a substrate support. In the context of the present invention, the term "optical window" typically refers to an optically transparent plate designed to provide maximum transmission of optical radiation within a specific wavelength range, in this case preferably laser radiation, while simultaneously reducing reflection and absorption. Further, the optical window can act as a thermal insulator so that as much heat as possible can be transmitted through the optical window. The optical window can be arranged and configured within a beam path of one of the laser radiations and / or a beam path of the reflected radiation that can be captured by a temperature sensor. In other words, the first laser radiation, the second laser radiation, and / or the reflected radiation can penetrate the optically transparent window body of the optical window. Additional laser radiation can be introduced by the optical window to the lower surface of the substrate, particularly the second substrate, and / or the reflected radiation can be reflected and captured through the optical window. As a result, it is possible to apply laser energy through the optical window via the lower surface of the second substrate, particularly during the first application step. Further, the first substrate arranged and configured on the second substrate can be positioned in a simple manner without taking into account the second laser device, whereby the joining tool has a significantly larger available space above the joining partner due to the application of the second laser radiation from below. Thus, for example, the movement distances required when changing or orienting the joining tool, the first laser device, and / or the capture device above the joining partner can be minimized, and thus displacement of the position during the joining process and / or the positioning step can be prevented.

[0040] The bonding tool can have a holder having a negative pressure device for applying a negative pressure to the first substrate, and the first substrate can be fixed to the opening of the pressure chamber of the negative pressure device. The first substrate can preferably be removably fixed to the opening of the pressure chamber of the negative pressure device, and the substrate can be removed by releasing the negative pressure. By fixing the substrate to the bonding tool by negative pressure, the substrate can be gently held on the bonding tool without being particularly deformed and positioned with respect to the second substrate. The negative pressure can be formed in a pressure chamber that can position the first substrate at its opening, and as a result, the negative pressure abuts against the substrate and holds it on the holder. The pressure chamber can have at least one side wall, and the other wall closing the pressure chamber can be formed by the optical window and the first substrate. This means that the optical window can be arranged opposite to the opening of the pressure chamber at a distance from the second substrate. Advantageously, for positioning, it is sufficient to ensure that only the side walls of the pressure chamber abut against the substrate, thereby gently holding the substrate and preventing deformation that can occur when the optical window is in direct contact with the substrate. Thus, furthermore, this also enables a three-dimensional substrate to be fixed to the bonding tool. It has been found to be particularly advantageous for the side walls of the holder to abut against the rear side of the first substrate. This enables the laser radiation impinging on the first substrate through the holder to be focused on the first substrate and eliminates stress or combustion on the surfaces surrounding the substrate, such as those of the second substrate. The negative pressure device of the holder can also be considered to generate a negative pressure that can hold the second substrate on the substrate support. Thus, since the substrate support and the holder jointly use the negative pressure device, the installation space can be advantageously saved.

[0041] A beam channel that at least partially extends within the bonding tool can be at least partially arranged within the pressure chamber and / or the pressure chamber can form at least one section of the beam channel. Preferably, the pressure chamber forms the last section of the beam channel, which means the section of the beam channel that comes into contact with the substrate.

[0042] The laser device can include a radiation guiding device having at least one mirror and / or lens for guiding laser radiation to one of the substrates. In particular, when two laser radiations are guided through a single beam channel, the radiation guiding device can have at least one semi-transparent optical mirror. At this time, the laser radiation from one of the two laser devices can penetrate the semi-transparent mirror so that the laser radiation collides with the rear side of the substrate, and the laser radiation from the other laser device is deflected by the semi-transparent mirror so that the beam path of the other laser radiation is also directed to the rear side of the substrate.

[0043] It is understood that the foregoing embodiments and the examples further described below can be implemented not only individually but also in any combination with each other without departing from the scope of the present invention. It is also understood that the foregoing embodiments and the examples further described below are related to the method according to the present invention equally or at least similarly without being separately mentioned thereto.

[0044] Embodiments of the present invention are schematically shown in the drawings and will be described below by way of example. Brief Description of the Drawings

Brief Description of the Drawings

[0045]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0046] FIG. 1 shows an embodiment of a laser device 01 according to the present invention for applying laser energy to at least one of substrates 02, 03, and the laser device 01 is suitable for performing a method according to the present invention for electrically contacting the terminal surfaces of two substrates 02, 03. In the illustration shown in FIG. 1, the first substrate 02 is arranged and configured above the second substrate 03 at a position overlapping the second substrate 03 by a bonding tool 11. A solder material 07 is arranged and configured between the first substrate 02 and the second substrate 03. The solder material 07 is arranged and configured on the terminal surfaces of the substrates 02, 03, each of which is formed on the front side of the substrates 02, 03. On the other hand, the rear side 31 of the second substrate 03 faces outward from the solder material 07 and can be positioned on a substrate support 12 (not shown here). As shown in FIGS. 1 and 3, the rear side 21 of the first substrate 02 can be brought into contact with the holder 14 of the bonding tool 11. A negative pressure can be applied to the first substrate 02 to fix it to the holder 14, and the negative pressure is formed in a pressure chamber 15 of a negative pressure device connected to a negative pressure pump (not shown here) via a pressure line 17. The pressure chamber 15 is formed by an optical window 13 and the side wall of the bonding tool 11 or the holder 14 of the bonding tool. The opening of the pressure chamber 15 is formed by the opening of the holder 14 and can be closed by the first substrate 02. As a result, it is clear that when a negative pressure is applied to the pressure chamber 15, a negative pressure is also applied to the substrate 02 to fix and position it on the holder 14. Through the optical window 13 arranged and configured in a beam channel 10 arranged and configured in the bonding tool 11, a first laser emission 41 emitted by a first laser device 04 and a second laser emission 51 emitted by a second laser device 05 can be applied to the rear side 21 of the first substrate 02. Therefore, the first laser emission 41 can be applied to the first substrate 02 during the first application stage, and the second laser emission 51 can be applied to the substrate 02 during the second application stage. It is also conceivable that the first laser emission 41 and the second laser emission 51 are applied to the substrate 02 in the second application stage.To perform the switching between the Inca stages or to activate the second laser device 05 to trigger the exposure to the second laser radiation 51, a control device 06 and a temperature sensor 08 are included. The temperature sensor 08 is arranged and configured within the beam channel 10 such that the temperature sensor 08 can capture the reflected radiation 81 reflected from the rear side 21 of the first substrate 02 and can transmit the temperature measurement value to the control device 06. The temperature sensor 08 and the control device 06 are shown by dotted lines and are connected via a data link 18 that serves to transmit the temperature measurement value and / or supply power to the temperature sensor. Further, the control device 06 can be connected to the first laser device 04 and the second laser device 05 via the data link 18 shown as a dotted line. Further, in addition to the temperature sensor 08, the control device 06 can have a time sensor, not shown here. The control device 06 is configured to control the switching from the first application stage to the second application stage depending on the duration of the first application stage, depending on the laser energy introduced into the first substrate 02, or depending on the temperature of the first substrate 02. It is also conceivable that the control device 06 is configured to determine the temperature of the solder material 07 based on the temperature of the first substrate 02, the reflected radiation it receives from the temperature sensor 08, and the characteristics of the first substrate 02. Further, it is clear that the beam path 42 of the first laser beam 41 emitted by the first laser device 04 is deflected in the direction of the first substrate 02 by the semi-transparent mirror 161 of the radiation guiding device 16. In contrast, the beam path 52 of the second laser beam 51 emitted by the second laser device 05 extends in the direction of the first substrate 02 through the semi-transparent mirror 161 of the radiation guiding device 16 without being deflected. The radiation guiding device 16 also has a lens 162 that serves to focus the laser radiation.

[0047] Figure 2 shows a second embodiment of a laser device 01 according to the invention, having a first laser device 04 and a second laser device 05. The first laser radiation 41 emitted by the first laser device 04, which follows the beam path 42, is not only focused on the rear side 21 of the first substrate 02, but it is also evident that radiation is applied to the region adjacent to the substrate 02. Thus, the first laser radiation 41 impinges not only on the first substrate 02 but also on the second substrate 03, and thus preheats the ambient environment of both the first substrate 02 and the second substrate 03. Further, in contrast to the first embodiment, the temperature sensor 08 is arranged and configured to capture the reflected radiation 81 coming from the solder material 07, and thus the temperature of the solder material 07 can be measured non - contact. Next, a radiation guiding device 16 having a semi - transparent mirror 161 deflects the first laser radiation 41 along the beam path 42 and focuses the second laser radiation 51, which has a beam path 52 and is emitted by the second laser device 05, onto the rear side 21 of the first substrate 02 by means of a lens 162. The radiation guiding device 16 can have additional lenses (not visible here) in order to focus the first laser radiation 41 onto a defined area on the mating partner and the ambient environment. This means that in the laser device 01 shown in Figure 2, the first substrate 02, the second substrate 03, and the ambient environment of the first substrate 02 can be preheated by the first laser radiation 41 in the first application step, and the second laser radiation 52 can be applied to the first substrate 02 in the second application step, as a result of which the solder material 07 melts and an electrical contact is established between the terminal surfaces of the first substrate 02 and the second substrate 03 facing each other. The control device 06 can further have a time sensor in addition to the temperature sensor 08, and as a result, the control device 06 can control the switching from the first application step to the second application step depending on the duration of the first application step, depending on the laser energy introduced into one of the substrates 02, 03, or depending on the temperature of the solder material 07.

[0048] The embodiment of the laser device 01 according to the present invention shown in FIG. 3 substantially corresponds to the embodiment shown in FIG. 1, but is different in that the first laser radiation 41 emitted by the first laser device 04 impinges on the rear side 31 of the second substrate 03. For this purpose, the second substrate 03, in particular the rear side 31 of the second substrate 03, is arranged on the substrate support 12 such that the rear side 31 of the substrate 03 abuts against the optical window 13 introduced into the substrate support 12. The beam path is directed through this optical window 13 by the mirror 161 of the radiation guiding device 16. According to FIG. 3, the radiation is applied to the first substrate 02 from above the mating partner in the second application stage. The first substrate 02 can be positioned relative to the second substrate 03 by the bonding tool 11. The laser radiation 51 follows a beam path 52 through a lens 162 that serves to focus it on the rear side 21 of the first substrate 02 through the optical window 13 of the bonding tool 11. In order to fix the first substrate 02 to the holder 14 of the bonding tool 11, a negative pressure can be applied via a pressure line 17 to a pressure chamber 15 formed at the end of the bonding tool 11 facing the first substrate 02. The second laser radiation 51 is guided through the beam channel 10 of the bonding tool 11 after focusing in order to shield the second laser radiation 51. Next, the control device 06 serves to control the switching between the first application stage and the second application stage and can have a time sensor (not shown here) in addition to the temperature sensor 08 shown here. The temperature sensor 08 captures the reflected radiation 81 emitted from the rear side 21 of the first substrate 02. The temperature sensor 08 can be arranged above or within the region of the laser device 05. The control device 06 can control the switching from the first application stage to the second application stage depending on the duration of the first application stage, depending on the laser energy introduced into the second substrate 03 by the first laser device 04, or depending on the temperature of the first substrate 02. In contrast to FIG. 1, according to the embodiment shown in FIG. 3, no elaborate radiation guiding device 161 is provided above the mating partner. Furthermore, since the first laser device 04 is arranged below the substrate support 12 and thus not within the movement region of the bonding tool 11, there is significantly more free space available when the bonding tool 11 moves.

[0049] List of reference signs

Explanation of signs

[0050] 01 Laser device 02 First substrate 21 Rear side of the first substrate 03 Second substrate 31 Rear side of the second substrate 04 First laser device 41 First laser emission 42 Beam path of the first laser device 05 Second laser device 51 Second laser emission 52 Beam path of the second laser device 06 Control device 07 Solder material 08 Temperature sensor 81 Reflected emission 10 Beam channel 11 Bonding tool 12 Substrate support 13 Optical window 14 Holder 15 Pressure chamber 16 Emission induction device 161 Mirror 162 Lens 17 Pressure line 18 Data link.

Claims

1. A method for electrically contacting terminal surfaces of two substrates (02, 03), the first substrate (02) being electrically and mechanically connected to the terminal surface of the second substrate (03) with its terminal surface facing the second substrate (03), The first substrate (02) is arranged with its terminal surface facing the terminal surface of the second substrate (03), - a first laser radiation (41) is applied to at least one of said substrates (02, 03) on the rear side using a first laser device (04) in a first application step, a second laser radiation (51) is applied to at least one of the substrates (02, 03) using a second laser device (05) in a second application step, such that a solder material (07) arranged between the substrates (02, 03) is melted at least to such an extent that an electrical contact is established between the terminal surface of the first substrate (02) and the terminal surface of the second substrate (03) facing each other, - during the first application step, said application is performed with a first laser radiation having a different wavelength than the second laser radiation, - the switching from the first application phase to the second application phase is controlled using a control device (06) in dependence on the duration of the first application phase, in dependence on the laser energy introduced into one of the substrates (02, 03), in dependence on the temperature of one of the substrates (02, 03) and / or in dependence on the temperature of the solder material (07).

2. 2. The method according to claim 1, characterized in that the radiation temperature of at least one of the substrates (02, 03) and / or the solder material (07) is measured at least during the first application phase by a temperature sensor (08), preferably realized as an infrared pyrometer, and the switching from the first application phase to the second application phase is controlled using the control device (06) in dependence on the radiation temperature of one of the substrates (02, 03) and / or in dependence on the radiation temperature of the solder material (07).

3. 3. The method according to claim 1 or 2, characterized in that in the second application step, in addition to the application using the first laser device (04), the application using the second laser device (05) is performed.

4. 4. The method according to claim 2, characterized in that the radiation temperature of at least one of the substrates (02, 03) and / or the solder material (07) is measured by the temperature sensor (08) during the second application phase, and the termination of the second application phase is performed in dependence on the radiation temperature of at least one of the substrates (02, 03) and / or the solder material (07).

5. 10. The method according to claim 9, characterized in that the first laser device (04) is switched on in a standby mode clocked for a defined duty cycle and is switched into an operating mode by the control device (06) in dependence on an existing temperature of at least one of the substrates (02, 03) measured by the temperature sensor (08).

6. the first laser radiation (41) is applied to the first substrate (02) at the rear side using the first laser device (04); 10. The method according to any one of the preceding claims, characterized in that the second laser radiation (51) is applied to the first substrate (02) on the rear side using the second laser device (05) in a second application step.

7. the first laser radiation (41) is applied to the first substrate (02) at the rear side and to the second substrate (03) at the front side using the first laser device (04) in the first application step, 10. The method according to any one of the preceding claims, characterized in that the second laser radiation (51) is applied to the first substrate (02) at the rear side using the second laser device (05) in the second application step.

8. the first laser radiation (41) is applied to the second substrate (03) at the rear side using the first laser device (04) in the first application step, 10. The method according to any one of the preceding claims, characterized in that the second laser radiation (51) is applied to the first substrate (02) in the second application step using the second laser device (05).

9. 10. A method according to any one of the preceding claims, characterized in that the process gas is activated at least during the first application stage.

10. A laser device (01) for applying laser energy to at least one substrate (02, 03), comprising: at least one first laser device (04), at least one second laser device emitting a laser radiation having a wavelength different from that of said first laser radiation; a control device (06) configured to activate said second laser device (05) and having a temperature sensor (08) and / or a time sensor; A laser device (01).

11. 11. The laser arrangement according to claim 10, characterized in that the first laser device (04) comprises an ultraviolet laser and the second laser device (05) comprises a near infrared laser.

12. 12. The laser device according to claim 10 or 11, characterized in that a joining tool (11) is provided for positioning and joining the first substrate (02) on the second substrate (03), and a beam channel (10) for the beam path (42) of the first laser radiation (41) and / or the beam path (52) of the second laser radiation (51) is realized in the joining tool (11).

13. The laser device according to any one of claims 10 to 12, characterized in that the temperature sensor (08) for detecting the radiation temperature is arranged in a beam path of reflected radiation (81) of the first substrate (02), the second substrate (03) and / or the solder material (07) and is realized as an infrared sensor, preferably a pyroelectric infrared sensor.

14. 14. The laser device according to any one of claims 10 to 13, characterized in that a substrate support (12) is provided to which at least the rear side of one of the substrates (02, 03), preferably the rear side (31) of the second substrate (03), can be fixed.

15. 15. The laser device according to claim 14, characterized in that an optical window (13) having an optically transparent window body for unhindered passage of laser radiation (41, 51) and / or reflected radiation (81) to and / or from at least one substrate (02, 03) is introduced into the substrate support (12), the optical window (13) being arranged in a beam path (42, 52) of one of the laser radiation (41, 51) and / or in a beam path of the reflected radiation (81), which can be captured by the temperature sensor (08).

16. 10. The laser apparatus according to claim 9, wherein the joining tool (11) comprises a holder (14) having a negative pressure device for applying negative pressure to the first substrate (02), the first substrate (02) being capable of being fixed at an opening of a pressure chamber (15) of the negative pressure device.

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