Method for controlling the temperature of parts in order to produce a soldered or sintered connection, and soldering or sintering device
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- PINK GMBH THERMOSYSTEME
- Filing Date
- 2024-08-07
- Publication Date
- 2026-07-01
Smart Images
Figure EP2024072401_06032025_PF_FP_ABST
Abstract
Description
[0001] Method for tempering components for producing a soldered or sintered joint and soldering or sintering device
[0002] The invention relates to a method for tempering components to produce a soldered or sintered connection between the components, wherein at least one controllable heat source is provided to provide thermal energy to be transferred to the components.
[0003] Furthermore, the invention relates to a soldering or sintering device for producing a soldered or sintered connection between components, wherein the soldering or sintering device has at least one controllable heat source which is designed to provide thermal energy to be transferred to the components.
[0004] State of the art
[0005] During sintering and soldering, two or more components, particularly electronic components and substrates, can be electrically and / or thermally bonded to one another using a joining material. The joining material is sintered or melted. The components to be joined can be pressed between an upper tool and a lower tool, whereby the pressing pressure during sintering is generally significantly higher than during soldering. In conventional sintering or soldering devices, the heat energy required for sintering or soldering can be transferred to the components via the upper tool and the lower tool.
[0006] Examples of conventional sintering or soldering devices and corresponding methods are described, for example, in DE 10 2006 034 600 B4, DE 203 00 375 U1, DE 10 2004 047 359 B3, DE 10 2012 206 403 B3 and WO 2014 / 135151 A2.
[0007] The devices or systems used to produce soldered or sintered joints can have one or more process chambers in which the process atmosphere required to carry out the soldering or sintering process can be adjusted and, in particular, also changed during the process. The components to be joined, which are previously combined into assemblies and, if necessary, can be fixed relative to one another in a suitable manner to maintain the desired positions by suitable means, can be transported to, from and between the various process chambers by suitable transport means. The process atmosphere in a respective process chamber can be adjusted and / or changed, for example, with regard to its material composition, pressure and / or temperature. For example, pressures between 1 hPa and 1200 hPa can be set using different process gas mixtures.
[0008] With conventional soldering or sintering devices, the heat energy can be introduced via the upper tool and / or the lower tool. In principle, heated plates or infrared radiators with variable spacing can also serve as a heat source. Another option for heating components is to introduce the heat energy into the components or into a suitable carrier plate by induction. For this purpose, one or more induction devices can be arranged in the process chamber above and / or below the components to be joined. This creates corresponding induction zones designed so that the electromagnetic energy generated by the induction devices is introduced into the components, where it generates eddy currents that heat them.To cool the induction devices, they can be directly connected to a fluid-flow cooling circuit, whereby cooling can also be achieved through thermal contact with the walls of the process chamber. Cooling via convection is also possible.
[0009] In principle, the distance between the induction devices and the components or the support plate can be adjusted to optimize the heat or energy input for different component properties. For this purpose, the existing induction devices can be raised or lowered together or individually. Furthermore, it is possible to adapt the shape of the induction devices to the shape of the components or support plates for optimized energy input.
[0010] Compared to component heating by thermal radiation or thermal contact, energy input through induction is very easy to control. With induction devices, the heat input can be continuously adjusted from no power to maximum power within fractions of a second. In order to achieve precise and differentiated temperature control in terms of time and / or space when using heat sources in which the input of thermal energy can be adjusted in a highly dynamic manner, as is particularly possible with the aforementioned induction devices, it is necessary to provide an adapted control system for the heat source, which must also take into account delays in heat transport within the components. Precise measurement of component temperatures is of great importance here.
[0011] Traditionally, the component temperature is measured by one or more temperature sensors that are in thermal contact with the components, i.e., the temperature sensor is attached to or integrated into the component to be measured. If the location where the thermal energy is introduced into the component is spaced apart from the temperature measurement location, the limited thermal conductivity of the components can cause a time delay between the energy introduction and the temperature measurement. This can lead to imprecise component temperature control and thermal overload of the components due to "overshoots."
[0012] To reduce such inaccuracies, the temperature measurement location can be chosen so that it is as close as possible to the energy input. This allows the heat source control system to react quickly to temperature changes. However, the actual temperature of the components cannot be measured very accurately, as they are not exposed to heat energy directly, but indirectly via thermal coupling, and thus with a delay.
[0013] DE 102004 047 359 B3 proposes using a non-contact optical measuring system, such as a pyrometer, for temperature measurement. However, such optical measuring systems have the disadvantage that the measured temperature is not absolute, but depends on the material and surface properties of the components.
[0014] DE 11 2008 000 853 T1 describes a temperature measurement in a heat treatment chamber with a heating element, a component, a contact temperature sensor, and a non-contact temperature sensor. The non-contact temperature sensor is located outside the heat treatment chamber, and the temperature locations for detecting the temperature of the contact temperature sensor and the non-contact temperature sensor are virtually identical, so that a difference in the measured value of the non-contact temperature sensor can be eliminated by the measured value of the contact temperature sensor. The dimensional stability and the sensor mass are very low, which has the disadvantage of creating a measuring gap, whereby changes in the number of molecules quickly affect temperature changes.
[0015] Description of the invention
[0016] The object of the invention is to provide a method for temperature control of components to create a soldered or sintered connection between the components, which enables precise adjustment of the component temperature and a flexible arrangement of the temperature sensors. This invention further aims to compensate for disruptive influences of pressure / gas fluctuations on the non-contact sensor.
[0017] The problem is solved by a method having the features of claim 1. Advantageous embodiments of the method are specified in the dependent claims.
[0018] A method for tempering components to produce a soldered or sintered connection between the components is proposed, wherein at least one controllable heat source is provided to provide thermal energy to be transferred to the components. A first temperature of a component or of a component of a soldering or sintering device in thermal contact with a component is measured at a first temperature location by means of at least one first temperature sensor which is in thermal contact with the component or component, and a second temperature of a component or of a component of a soldering or sintering device in thermal contact with a component is measured at a second temperature location without contact by means of at least one second temperature sensor.The first temperature location is spatially spaced from the second temperature location in such a way that a temperature gradient between the first and second temperatures can be expected when the temperature changes. The measured second temperature is calibrated on the basis of the measured first temperature in order to determine a calibrated second temperature, wherein the heat source is controlled at least on the basis of the calibrated second temperature. The measurement of the first and second temperatures is preferably carried out at different locations. The component(s) of a soldering or sintering device which are in thermal contact with a component and are also referred to below as device components for short can be, for example, carrier plates, carrier frames or component carriers on which the components to be joined are mounted during the manufacturing process.The first temperature can also be additionally determined by a temperature sensor integrated into a component and connectable to a control unit designed to carry out the method, in order to transmit the first temperature of a component to the control unit. Thus, if the first temperature of a component or device component is measured by several first temperature sensors, the first temperature can be determined in a suitable manner, for example, by averaging the temperatures measured by the several first temperature sensors or by other methods. The same applies to the second temperature.
[0019] The spatial spacing of the first and second temperature locations means that they are spatially distributed, i.e. they are either arranged on one side of the components at a spatial distance from one another, or are arranged on opposite sides of the components. Thus, when arranged on the same side of the components, the first and second temperature sensors can be spaced apart by at least 5%, in particular 10% of the component diameter. In any case, during a heating-up or cooling-down phase, it can be expected that the first and second temperature sensors measuring at different locations will record measured values that indicate a temperature gradient. In thermal equilibrium, i.e. with a longer dwell time at constant temperature conditions, the temperature gradient can become small or disappear completely.However, in the case of at least changing heat input from the heat source, such as in the heating or cooling phase, it can be expected that the first and second temperature sensors will record different measured values due to the spatial spacing. In any case, it cannot be assumed that the first temperature sensor records the same measured value as the second temperature sensor, so calibration of the second temperature sensor by the first temperature sensor within the framework of a temperature gradient when the temperature changes is possible, particularly under dynamic temperature conditions. Advantageously, the spaced-apart arrangement of the temperature sensors allows a high degree of flexibility in the arrangement, so the second temperature sensor can preferably be located on a side of the components or parts facing the heat source.a component carrier, as a component in thermal contact with the component, the second temperature for regulating the heat source can be detected, while the first temperature sensor can be arranged at a mechanically easily accessible location on the components or the component carrier in order to detect the first temperature. Thus, with a spaced arrangement, precise calibration of the second temperature of the second temperature sensor using the first temperature of the first temperature sensor is possible, even in confined spaces or in hard-to-reach temperature locations. Temperature sensors already integrated into the component, for example, can also be used as the first temperature sensors.
[0020] In the method according to the invention, the first and second temperatures are thus combined in a suitable manner to achieve optimal temperature control at the components. Preferably, the first and second temperatures are measured in such a way that both temperatures remain essentially unchanged for a specific period of time, so that the influence of delays in heat equalization within the components or between the components and the device components in contact with them can be largely reduced. The first and second temperatures can be measured on the same component or on the same device component or on different components or device components and in any case at two spatially spaced temperature locations.
[0021] In this context, calibration refers to the sum of activities that serve to determine, under specified conditions, the relationship between the measured values of the temperature variable output by the second temperature sensor, with the associated measurement uncertainty, and the measured values of the first measuring sensor as the reference temperature sensor, with the associated measurement uncertainty. This relationship can be used to account for the influence of the spatial distance between the first and second temperature locations, as well as other measurement-related differences.
[0022] By determining a calibrated second temperature, particular account is taken of the fact that, as a rule, with non-contact temperature sensors the measured second temperature deviates from the actual temperature at this measuring point. This is due to the fact that a non-contact measured temperature can vary due to material properties and / or surface properties of the component or device component whose temperature is measured. According to a preferred embodiment, the method is carried out in an adjustable process atmosphere, wherein adjusting the process atmosphere comprises at least adjusting a material composition, a pressure and / or a temperature of the process atmosphere. For example, the process atmosphere can contain reactive or non-reactive process gases depending on the respective process stage.If the temperature of the process atmosphere changes, this temperature change can also be included in the control of the heat source.
[0023] According to a further preferred embodiment, the first temperature sensor is selected from a group comprising at least thermistors, PTC thermistors, semiconductor temperature sensors, thermocouples, and resonant circuit-based temperature sensors. Alternatively or additionally, the second temperature sensor is a sensor configured to detect thermal radiation and is preferably selected from a group comprising at least pyrometers, bolometers, and thermopiles. The sensor types exemplified for the first temperature sensor(s) represent typical examples of contact-based temperature sensors. Accordingly, the sensor types exemplified for the second temperature sensor(s) are typical contactless temperature sensors.
[0024] According to a further preferred embodiment, the at least one heat source is designed for contact-based or contactless heat transfer to the components or to the one or more of the aforementioned components. The heat source is preferably selected from a group comprising generators of electrical, magnetic, or electromagnetic fields, preferably heating plates, induction heating elements, or infrared radiators, that can be coupled at least thermally, inductively, or capacitively to the components or to the aforementioned component(s). The list of possible heat sources is not exhaustive. However, it has been shown that generators of magnetic fields that can be inductively coupled to the components or to the aforementioned component(s), which can also be referred to as induction devices or inductors, are particularly suitable.In such induction devices, the heat output can be controlled in a variety of ways, for example by changing the operating voltage, the operating current or the frequency.
[0025] According to a further preferred embodiment, the heat source is controlled in a process step comprising the production of the soldered or sintered connection, and the calibrated temperature is determined in at least one calibration step preceding the process step, wherein the calibration step comprises generating and storing a respective calibration function, on the basis of which the calibrated second temperature can be determined from a measured second temperature. The calibration step can be carried out, for example, by measuring the first and second temperatures at two different part or component temperatures in order to then determine the calibration function from the measured values. Several calibration steps can also be carried out, in which several respective calibration functions are determined. This can be done, for example, by defining the calibration function in a component-specific manner.is generated and stored component-specifically.
[0026] According to a preferred embodiment, the calibration step is performed before each process step, with the heat source being controlled in the process step based on the previously determined calibration function. In this case, it is not necessary to know the properties of the component or device component on which the second temperature is measured in order to select a suitable calibration function. Performing the calibration step prior to the process step ensures that the temperature control does not lead to component damage due to incorrect selection of the calibration functions.
[0027] Alternatively or additionally, the calibration step can also be performed once or multiple times during the process step, preferably at predetermined times or at times when the temperature of the components or device components is essentially unchanged. The aforementioned performance of a calibration step at times when the temperature of the components or device components is essentially unchanged refers to the performance of a calibration in which a temperature curve of the components or device components exhibits respective plateaus with different temperatures. This serves to wait for a certain equilibration time in order to eliminate latencies resulting from the different temperature measurement principles and the spatial position of the measuring points.
[0028] In this context, it has proven advantageous to select a calibration function appropriate for the components to be processed from several component-specific calibration functions stored prior to a process step. The heat source is controlled in the process step based on the selected calibration function. In principle, a calibration function can also be selected first, which can then be checked and / or adjusted during the process step.
[0029] According to a further advantageous embodiment, the calibration function is a linear function or a polynomial function, preferably of the fourth degree. The use of a linear function has proven computationally simple, and any resulting inaccuracies can be tolerated. A polynomial function, especially a fourth-degree polynomial function, is particularly suitable for calibrating the measurement characteristics of a pyrometer.
[0030] According to a further advantageous embodiment, the heat source is controlled in a two-stage process, wherein in a first stage, a modified setpoint temperature is determined based on the measured first temperature and a predefined setpoint temperature, and wherein in a second stage, the output of the heat source is controlled based on the measured or calibrated second temperature and the modified setpoint temperature. Such a two-stage control is also referred to as cascade control. The predefined setpoint temperature does not necessarily have to be a fixed setpoint temperature; rather, a curve or ramp of the setpoint temperature can also be used as the basis.In particular, the expressions "based on the measured first temperature, the specified target temperature, the measured or calibrated second temperature, and the modified target temperature" are not limited to absolute values of the specified variables, but expressly also include their respective temporal profiles, i.e., in particular, their mathematical derivatives over time. Furthermore, determining the modified target temperature based on the measured first temperature and the specified target temperature does not preclude the possibility that additional parameters or measured values may be included in determining the modified target temperature. Accordingly, the heat source's output cannot be controlled exclusively on the basis of the measured or calibrated second temperature and the modified target temperature. Rather, additional parameters or measured values may also be included here.In particular, feedback can also be provided in the respective control loops in each stage of the two-stage process. According to a further preferred embodiment of the process, the components to be connected are arranged in a main extension plane, with the first temperature sensor being arranged on one side of the main extension plane and the heat source and the second temperature sensor being arranged on the other side of the main extension plane. While the second temperature sensor and the heat source are arranged on the same side of the component arrangement and thus changes in the component temperature can be detected with a very short time delay, the first temperature determined by the first temperature sensor, due to its spatial arrangement, is subject to a certain latency based on the heat conduction within the component(s) or device components.
[0031] Alternatively, the first and second temperature sensors can be arranged on one side of the main extension plane, and the heat source can be arranged on the other side of the main extension plane. Furthermore, the first and second temperature sensors and the heat source can also be arranged on the same side of the main extension plane.
[0032] In a further aspect, the invention relates to a soldering or sintering device for producing a soldered or sintered connection between components, comprising at least one controllable heat source which is configured to provide thermal energy to be transferred to the components, at least at one first temperature location a first temperature sensor which is thermally contactable with a component or a component of the soldering or sintering device which can be thermally contacted with a component and is configured to measure a first temperature of the component or the component, and at least at one second temperature location a second temperature sensor which is configured to measure a second temperature of a component or a component of the soldering or sintering device which can be thermally contacted with a component in a contactless manner.The first temperature location is spatially spaced from the second temperature location such that a temperature gradient between the first and second temperatures is to be expected upon temperature change. A control unit, which is connected to the heat source and to the first and second temperature sensors, is configured to carry out the method according to one of the preceding claims. As already mentioned above, the first temperature sensor or a further first temperature sensor can be a temperature sensor integrated into a component and connectable to the control unit in order to transmit a first temperature of this component to the control unit.
[0033] According to a preferred embodiment, the heat source has a measuring window which allows infrared radiation emitted by the components or by the said component(s) of the soldering or sintering device to pass in the direction of the second temperature sensor.
[0034] According to a further preferred embodiment, a tube pointing at least in the direction of the second temperature sensor is arranged in the measuring window, which tube is designed to direct infrared radiation emitted by the components or by the said component(s) of the soldering or sintering device in the direction of the second temperature sensor and preferably to shield the second temperature sensor from infrared radiation which was not emitted by the components or by the said component(s).
[0035] According to a further preferred embodiment of the soldering or sintering device, the components, the at least one heat source, the at least first temperature sensor, and the at least second temperature sensor are arranged in or on a gas-tight process chamber with an adjustable process atmosphere, in particular a vacuum, wherein the second temperature sensor is preferably arranged on a side of the heat source facing away from the components. In other words, the soldering or sintering device can comprise at least one gas-tight process chamber in which a process atmosphere, e.g., a low-oxygen or oxygen-free atmosphere, in particular a vacuum, can be adjusted, so that the components can be thermally treated, in particular soldered or sintered, without oxidation.Both the first and the second temperature sensor are arranged in or on the process chamber, such that the measured value signals from the temperature sensors are transmitted outside the process chamber as first and second temperatures. The second temperature sensor can be arranged inside or outside the process chamber; in the latter case, the second temperature sensor can observe the second temperature location through an optical window in the process chamber wall. A control unit, preferably arranged outside the process chamber, calibrates the second temperature based on the first temperature and regulates the heat source based on the calibrated second temperature. In this way, precise heat source control can be achieved, which can also be used, for example, to maintain a definable temperature gradient between the first and second temperature locations.
[0036] Drawings
[0037] Further advantages will become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.
[0038] They show:
[0039] Fig. 1 is a schematic sectional view of a soldering or sintering device according to an embodiment,
[0040] Fig. 2 and 3 schematic sectional views of soldering or sintering systems according to further embodiments,
[0041] Fig. 4 is a diagram with two exemplary temperature profiles of a first and a second temperature;
[0042] Fig. 5 is a schematic diagram to explain the determination of a
[0043] Calibration function for the second temperature;
[0044] Fig. 6 is a schematic block diagram of a two-stage temperature control;
[0045] Fig. 7 is a diagram with various exemplary temperature curves and a curve of a relative heating power; and
[0046] Fig. 8 shows a diagram with further exemplary temperature curves and a curve of relative heating power. In the following, the same reference numerals are used for identical or similar elements.
[0047] Fig. 1 shows a schematic, simplified sectional view of a soldering device 10 according to an exemplary embodiment. The soldering device 10 comprises a pot-shaped, downwardly open transport frame 14, in the bottom opening of which a component carrier 12 is inserted, which represents a component of the soldering device 10. Components 16, 18 to be connected are placed on the component carrier 12. The components 18 can, for example, be substrates, each of which is to be connected to a plurality of components 16, for example power semiconductors, by the soldering process. A joining material (not shown) can be provided between the components 16 and the components 18. Arranged below the transport frame 14 with the component carrier 12 arranged therein is an induction device 20 which is designed to generate a strong magnetic field which can induce eddy currents at least in the component carrier 12.These eddy currents cause the component carrier 12 to heat up. It is understood that other heat sources may also be provided instead of the induction device 20. The distance between the component carrier 12 or the transport frame 14 on the one hand and the induction device 20 on the other hand is variable.
[0048] The soldering device 10 further comprises a first temperature sensor 24 at a first temperature location, here on an upper side of a substrate as component 18, which is guided through the transport frame 14 and is spring-loaded in contact with one of the components 18 and which is configured to measure a first temperature.
[0049] The induction device 20 has a measuring window 22, which allows infrared radiation emitted from an underside of the component carrier 12 as a second temperature location to pass toward a second temperature sensor 26 arranged below the measuring window 22, so that a second temperature can be measured by the second temperature sensor 26. In this exemplary embodiment, the first and second temperature locations are arranged on opposite sides of the component carrier 12.
[0050] The first temperature location can preferably be a surface of a component 18. The second temperature location can preferably be a surface of a direct or indirect heat input (e.g., radiant heat) of the heat source 20 on the underside of the component 18 or of a component carrier 12. The first temperature sensor 24 is designed as a contact temperature sensor and can be a thermistor, PTC thermistor, semiconductor temperature sensor, thermocouple, resonant circuit-based temperature sensor, or the like. The second temperature sensor 26 is a contactless temperature sensor, for example, a pyrometer, volometer, or thermopile, which measures the temperature by detecting the infrared radiation emitted by the measurement object.
[0051] According to a modification not shown, a tube can be arranged in the region of the measuring window 22, which tube also surrounds the second temperature sensor 26 and, on the one hand, focuses or directs the infrared radiation emitted by the component carrier 12 to be detected and, at the same time, keeps extraneous radiation, which could falsify the temperature measurement, away from the second temperature sensor 26.
[0052] Fig. 2 shows a soldering device 110 according to a further embodiment, which is constructed similarly to the soldering device 10 of Fig. 1. The soldering device 110 comprises several, in the present embodiment, three component carriers 12, each component carrier 12 being assigned a separately controllable induction device 20. The distances between the induction devices 20 and the component carriers 12 are individually adjustable. All three component carriers 12 are arranged on a common transport frame 14. The respectively assigned temperature sensors 24, 26 are arranged similarly to the embodiment of Fig. 1.
[0053] The components of the soldering device 110 are located in a process chamber 28, which provides a preferably adjustable process atmosphere for the soldering process. The process chamber 28 can be temperature-controlled, evacuated, and / or pressurized, or even flooded with different process gases. The pressure and / or temperature of this process atmosphere can be set to predetermined values and, in particular, also changed. The first and second temperature sensors 24, 26 are arranged in or on the process chamber 28. In particular, the second temperature sensor 28 is arranged outside the process chamber and observes the second temperature point through an optical through-window in the process chamber wall.
[0054] Fig. 3 shows a soldering device 210 according to a further embodiment, which essentially represents a mirror image of the soldering device 110 of Fig. 2 on a horizontal axis. In contrast to the embodiment of Figs. 1 and 2, the first temperature sensors 24 are not in thermal contact with the components 18, but rather with the undersides of the component carriers 12 as the first temperature location. The second temperature sensors 26, in turn, do not measure the temperature of the component carriers 12, but can directly detect the temperatures of the components 16 and / or 18 arranged above the component carriers 12 as the second temperature location.
[0055] In all three exemplary embodiments, the devices configured to carry out the method according to the invention are illustrated as soldering devices 10, 110, 210. It is understood that the arrangement of temperature sensors 24, 26 described here as an example can alternatively also be provided in correspondingly designed sintering devices. Such sintering devices generally include additional tools that can exert the pressing pressures required to produce a sintering device on the components to be joined. These tools can optionally have suitable measuring openings through which the access required for contactless or contact-based temperature measurement on the components or components of the sintering device is created.
[0056] It is further understood that the soldering devices 10, 110, 210 may also include any necessary tools for applying pressure to the components 16, 18. For reasons of clarity, these are not shown in the present embodiments.
[0057] A simplified description of a method according to the invention for tempering components to produce soldered or sintered joints between the components 16, 18 is given below. This method can be carried out using the soldering devices 10, 110, 210 according to FIGS. 1 to 3, for example, in a control unit (not shown), which can be connected to the temperature sensors 24, 26 and the induction device(s) 20 as heat sources. With the aid of such a control unit, in particular, the heat output generated by the heat sources 20 can be regulated in order to heat the components 16, 18 to a desired temperature and also to cool them again by reducing or switching off the heating output.
[0058] While the first temperature sensor 24 can determine the part or component temperature at the first temperature location very precisely due to its contact-based operation, the part or component temperature at the second temperature location determined by the second, contactless temperature sensor 26 is subject to systematic measurement errors. An example of such a contactless temperature sensor is a pyrometer. Here, the radiant power P emitted by a measuring body whose temperature is to be determined is determined. For technical reasons, only a specific wavelength range in the infrared range is generally considered. According to the Stefan-Boltzmann law, the total radiant power P of a real body
[0059] P = s • c • A • T 4 , (1) where s is the emissivity, o is the Stefan-Boltzmann constant (o = 5.6704 • 10' 8 Wrrr 2 K' 4 , A is the area (in m2 ) and T is the temperature (in K). The emissivity s thus represents the thermal radiation capability of the measuring object and depends on both the material and the surface properties of the measuring object. The second temperature is preferably determined at short wavelengths. The measuring wavelengths of a pyrometer are preferably no longer than 5 pm, particularly preferably no longer than 2 pm, in order to limit the influence of inaccurately determined emissivity s on the measurement accuracy.
[0060] Since the emissivity s of the measurement object, i.e., a part or a component of the soldering or sintering device, is often not exactly known or is subject to local variations, the measured second temperature may have a systematic measurement error. For this reason, a calibrated second temperature is determined on the basis of the measured second temperature, with the measured first temperature being used as the calibration variable. In order to rule out the possibility that the actual temperature at the measuring point of the first temperature location, at which the first temperature is measured, differs from the actual temperature at the measuring point of the second temperature location, at which the second temperature is measured, the temperatures of the components 16, 18 or of the components of the soldering device 10, 110, 210 that are in thermal contact with the components should be in equilibrium, i.e.There should no longer be any temperature gradients between the different measuring points of the first and second temperature locations. This can be achieved, for example, by keeping the heat source's heating output constant for a certain equilibration time or by regulating it to a constant temperature, and only then determining the corresponding temperature measurements.
[0061] The calibrated second temperature can be determined, for example, based on a calibration function determined during a calibration step. The determination of such a calibration function is described in more detail below.
[0062] An advantage of the method according to the invention is that the measurement of the first temperature, which is carried out with a temperature sensor in thermal contact with a component or device component at the first temperature location and is therefore slow but provides a very accurate measured value, is suitably combined with the measurement of the second temperature, which is carried out by a non-contact temperature sensor at the second temperature location and is therefore fast but only provides inaccurate measured values due to the material dependency. This combination of the measured values for the first and second temperatures achieves optimal temperature control on the components. In addition, a flexible and spaced arrangement of the first and second temperature sensors is possible.
[0063] Fig. 4 shows exemplary time profiles for the first temperature (T1) and the second temperature (T2), with the absolute value of the time scale being arbitrary. The temperatures T1, T2 were measured on opposite sides of a copper component with a thickness of 5 mm. A heat source 20 is arranged on the same side as the temperature sensor 26 detecting the second temperature T2, while the temperature sensor 24 detecting the first temperature T1 is arranged on the side of the component facing away from the heat source 20 (cf. the arrangements in Figs. 1 and 2).
[0064] While the second temperature T2 reaches a maximum at around t = 48 °C, the first temperature T1 reaches a plateau at around t = 55 °C, i.e. the first temperature T1 remains approximately constant from this point onwards. The time difference of 7 °C between reaching the maximum of the second temperature T2 and reaching the plateau of the first temperature T1 is due to the latency period caused by heat transport between the two sides of the component. Furthermore, Fig. 4 shows that the first temperature T1 has a much slower and therefore less fluctuating curve than the second temperature T2. In addition, because calibration has not yet been carried out (the measured second temperature T2 is shown in Fig. 4), there is a temperature difference of approximately 20 to 25 °C between the two temperatures T1 and T2.
[0065] With reference to Fig. 5, the implementation of a calibration step will now be explained by way of example. For this purpose, a first temperature T1.1 is measured in contact and a second temperature T2.1 is measured without contact at a first time t1 on an exemplary component whose temperature is continuously or intermittently increased. At a second time t2, a first temperature T1.2 and a second temperature T2.2 are measured.
[0066] Under the simplified assumption of a linear relationship between a measured second temperature T2 and a calibrated second temperature T2', the calibrated second temperature T2' can be calculated according to the equation
[0067] T2' = k*T2 + Toffset, (2) where k is a calibration factor and T Offset is a temperature difference at time t1. The factor k can be determined from the temperatures measured at times t1 and t2 according to the following equation: k = ri ' 2 ~ r1 ' 1 . (3)
[0068] The differential temperature Toffset can be determined from the temperature measurements according to the following equation:
[0069] Toffset = T1.1 - (T2.1*k). (4)
[0070] The temperature measurements for determining the calibration function are advantageously performed at times when the component exhibits no temperature gradient. This means that the component temperature is kept constant on a plateau for a suitable period of time, for example, 5 seconds. Naturally, the component temperature must be changed between the two times t1 and t2. In principle, it is also possible to repeat calibration at specified times, for example, at intervals of 10 seconds.
[0071] Alternatively, the calibration step can also be performed as part of a sample calibration step, in which a calibration function is performed for a sample component whose radiation properties correspond to the subsequently processed components or fixture components in contact with the component. This calibration function can then be accessed later during the actual process step, i.e., the actual soldering or sintering process, without the need for recalibration during the process step.
[0072] Instead of the calibration explained with reference to Fig. 5, the emissivity s can also be determined directly. This can be done, for example, by first determining the first temperature T1.1 with contact and the second temperature T2.1 without contact, similar to the procedure described with reference to Fig. 5, at an ambient temperature of, for example, 20°C. Subsequently, the component serving as the test object is heated to a higher temperature, for example, between 150°C and 250°C, and the first temperature T1.2 and the second temperature T2.2 are again determined.
[0073] The emissivity s can then be calculated according to the following equation:
[0074] For this purpose it was assumed that T2 4 2 is smaller than T2. Otherwise, the values would have to be swapped so that the emissivity s < 1.
[0075] With reference to Fig. 6, a two-stage control or cascade control of a heat source is now described, wherein the controlled variable for this heat source is described by a function u2(t). Two temperature sensors are arranged on a measurement object, wherein a first temperature sensor in contact with the measurement object generates the first temperature T1 and a non-contact temperature sensor generates the second temperature T2. The curve of the first temperature T1 is described by a function yM 1 (t) and the curve of the second temperature T2 is described by a function yM2(t). A setpoint temperature function w1(t) serves as the input variable of the control. From the signals w1(t) and yM1(1), a difference function e1(1) is generated by subtracting the signals according to the equation e1(t) = w1(t) - yM1(t) (6) and fed to a master controller R1.The master controller R1 can, for example, be designed as a PI controller (proportional-integral controller), which generates a control function u1(t) according to the equation ul(t) = e1(t) * kp + ki * f el(t) dt (7), where kp, ki are respective gain factors. Through positive coupling with the setpoint temperature function w1(t), a modified setpoint temperature function w2(t) is determined from u1(t) according to the equation w2(t) = Min(ul(t), dTmax) + wl(t) (8).
[0076] In the second control stage, the difference between the modified setpoint temperature function w2(t) and the function yM2(t) is calculated according to the equation e2(t) = w2(t) - yM2(t) (9) to generate an input function e2(t) for the slave controller R2. From this, the slave controller R2 generates the controlled variable or control function u2(t) for the heat source according to the equation u2(t) = e2(t) * kp + ki * f e2(t) dt, (10) where kp, ki are the respective gain factors.
[0077] It is understood that the specific design of the cascade control system is purely exemplary and can be modified as needed. The heat source output is adjusted as appropriate. For example, when using an induction device 20 as shown in Figs. 1 to 3 as the heat source, the control can be carried out by a control unit of the induction device 20 by adjusting the frequency, current, and / or voltage. Additionally, the distance of the induction device 20 can also be included in the control. When using an infrared heater or an ohmic heater, the heating current can be controlled.
[0078] Due to the rapid reaction of the heat source or the side of the components 16, 18 or the component carrier 12 facing the induction device 20, the temperature profile of the component side facing the induction device 20 can be controlled according to a wide range of functions, for example ramps, S-curves, quadratic functions, e-functions, holding phases or polynomials of higher degree.
[0079] This behavior can also be exploited to accelerate the heating of components 16, 18. To this end, the temperature of the component side facing the induction device 20 can be briefly increased to increase the temperature difference between the two opposite sides of components 16, 18.
[0080] Due to variations in the component properties, particularly on the component side facing the induction device 20, the non-contact second temperature sensor 26 cannot measure an absolutely precise temperature. This disadvantage is compensated for by measuring the component side facing away from the induction device 20 using the first temperature sensor 24, since this value continuously adjusts the temperature level, ensuring that the desired temperature can always be set on the components 16, 18.
[0081] Under certain circumstances, external effects, such as gas flowing into the process chamber 28, may affect the contacting first temperature sensor 24, which may impair the control process. This can be taken into account according to a modification of the cascade control described with reference to Fig. 6. In this case, the manipulated variable u1(t) generated by the master controller R1 can be set to a suitable value u1f at a given time, e.g., the time of an intended gas introduction. reeZ e can be "frozen," which allows for improved temperature control. The modified setpoint temperature w2(t) is thus generated not on the basis of u1(t) and the setpoint temperature w1(t), but on the basis of u1f reeZ e and w1 (t).
[0082] With reference now to Fig. 7 and 8, typical time courses of the functions w1(t), yM1(t), yM2(t) and u2(t) are described, with characteristic event points being marked with numbers in the diagrams.
[0083] As can be seen in Fig. 7, at event points 1 and 3, drops in the first temperature T1 occur, caused, for example, by gas flowing into the process chamber. In a cascade control system without the previously described "freeze function," these temperature drops lead to excessive counteracting of the cascade control, which manifests itself at event points 2 and 4 as temperature peaks in the second temperature T2 curve.
[0084] By "freezing" the manipulated variable u1 (t) generated by the master controller to the value ulfreeze immediately before the onset of events that may result in short-term temperature changes of the components, an improved temperature control of the component temperatures can be achieved.
[0085] Referring now to Fig. 8, characteristic events and processes, also labeled with numbers, during the implementation of the method according to the invention using the previously described cascade control are explained. The section of the curve of the second temperature T2 (yM2(t)) labeled with number 1 characterizes the lower measuring range limit of a pyrometer. During this period, the controlled variable u2(t) exhibits a constant curve, which is indicated by the number 2.
[0086] At event point 3, control begins. At event point 4, a strong overshoot of the second temperature T2 occurs, which, however, does not lead to an overshoot in the temperature T1 (yM1 (t)) curve, see section 7.
[0087] Number 5 characterizes the difference between the uncalibrated second temperature T2, which is higher than the target temperature, which is characterized by the function w1(t), due to deviating surface properties of the measurement object or components. At event point 6, the first temperature T1 reaches exactly the specified target temperature, whereby the measurement error of the non-contact second temperature sensor 28 is compensated by the calibration described above.
[0088] List of reference symbols
[0089] 10, 110, 210 soldering device
[0090] 12 component carrier, component
[0091] 14 transport frames
[0092] 16, 18 component
[0093] 20 Induction device, heat source
[0094] 22 measuring windows
[0095] 24 first temperature sensor
[0096] 26 second temperature sensor
[0097] 28 Trial Chamber
[0098] R1 master controller
[0099] R2 follower controller
Claims
Patent claims 1. A method for tempering components (16, 18) for producing a soldered or sintered connection between the components (16, 18), wherein at least one controllable heat source (20) is provided to provide thermal energy to be transferred to the components (16, 18), wherein a first temperature of a component (16, 18) or of a component (12) of a soldering or sintering device (10, 110, 210) that is in thermal contact with a component (16, 18) is measured at at least one first temperature location by means of at least one first temperature sensor (24) that is in thermal contact with the component (16, 18) or the component (12), and a second temperature of a component (16, 18) or of a component (12) of a soldering or sintering device (10, 110, 210) that is in thermal contact with a component (16, 18) is measured at at least one first temperature location a second temperature location is measured contactlessly by means of at least one second temperature sensor (26),wherein the first temperature location is spatially spaced from the second temperature location such that a temperature gradient between the first and second temperatures is to be expected upon temperature change, and wherein the measured second temperature is calibrated on the basis of the measured first temperature to determine a calibrated second temperature, and wherein the heat source (20) is controlled at least on the basis of the calibrated second temperature.
2. The method according to claim 1, characterized in that the method is carried out in an adjustable process atmosphere, wherein adjusting the process atmosphere comprises at least adjusting a substance composition, a pressure and / or a temperature of the process atmosphere.
3. Method according to claim 1 or 2, characterized in that the first temperature sensor (24) is selected from a group which includes at least thermistors, PTC thermistors, semiconductor temperature sensors, thermocouples and resonant circuit-based temperature sensors, and / or that the second temperature sensor (26) is a sensor designed to detect thermal radiation and is preferably selected from a group which includes at least pyrometers, bolometers and thermopiles.
4. Method according to one of the preceding claims, characterized in that the at least one heat source (20) is set up for contact-based or contactless heat transfer to the components (16, 18) or to the one or more of said components (12) and is preferably selected from a group which comprises generators of electrical, magnetic or electromagnetic fields, preferably heating plates, induction heating elements or infrared radiators, which can be coupled at least thermally, inductively or capacitively to the components (16, 18) or to the said component(s) (12).
5. Method according to one of the preceding claims, characterized in that the control of the heat source (20) takes place in a process step comprising the production of the soldered or sintered connection and the calibrated temperature is determined at least in at least one calibration step preceding the process step, wherein the calibration step comprises generating and storing a respective calibration function on the basis of which the calibrated second temperature can be determined from a measured second temperature.
6. The method according to claim 5, characterized in that the calibration step is carried out before each execution of a process step, wherein the control of the heat source (20) in the process step is carried out on the basis of the previously determined calibration function.
7. The method according to claim 5 or 6, characterized in that the calibration step is additionally carried out once or several times during the process section, preferably at predetermined times or at times at which the temperature of the components (16, 18) does not change substantially.
8. Method according to one of claims 5 to 7, characterized in that before carrying out a process step, a calibration function corresponding to the components (16, 18) to be processed is selected from a plurality of component-specific or component-specific stored calibration functions, wherein the control of the heat source (20) in the process step is carried out on the basis of the selected calibration function.
9. Method according to one of claims 5 to 8, characterized in that the calibration function is a linear function or a polynomial function, preferably of the fourth degree.
10. Method according to one of the preceding claims, characterized in that the control of the heat source (20) takes place in a two-stage process, wherein in a first stage a modified target temperature is determined on the basis of the measured first temperature and a predetermined target temperature, and wherein in a second stage a power of the heat source (20) is controlled on the basis of the measured or the calibrated second temperature and the modified target temperature. 1 . Method according to one of the preceding claims, characterized in that the components to be connected (16, 18) are arranged in a main extension plane, wherein the first temperature sensor (24) is arranged on one side of the main extension plane and the heat source (20) and the second temperature sensor (26) are arranged on the other side of the main extension plane, or wherein the first and the second temperature sensor (24, 26) are arranged on one side of the main extension plane and the heat source (20) are arranged on the other side of the main extension plane, or wherein the first and the second temperature sensor (24, 26) and the heat source (20) are arranged on the same side of the main extension plane.
12. A soldering or sintering device (10, 110, 210) for producing a soldered or sintered connection between components (16, 18), comprising at least one controllable heat source (20) configured to provide thermal energy to be transferred to the components (16, 18), at least one first temperature location having at least one first temperature sensor (24) thermally contactable with a component (16, 18) or a component (12) of the soldering or sintering device (10, 110, 210) that can be thermally contacted with a component (16, 18) and configured to measure a first temperature of the component (16, 18) or of said component (12), and at least one second temperature location having a second temperature sensor (26) configured to measure a second temperature of a component (16, 18) or of a component (16, 18) that can be thermally contacted with a component (16, 18) thermally contactable component (12) of the soldering or sintering device (10, 110, 210) to be measured contactlessly,wherein the first temperature location is spatially spaced from the second temperature location such that a temperature gradient between the first and second temperatures is to be expected upon temperature change, and with a control unit which is connected to the heat source (20) and to the first and second temperature sensors (24, 26) and is configured to carry out the method according to one of the preceding claims.
13. Soldering or sintering device (10, 110, 210) according to claim 12, characterized in that the heat source (20) has a measuring window (22) which allows infrared radiation emitted by the components (16, 18) or by the said component(s) (12) of the soldering or sintering device (10, 110, 210) to pass in the direction of the second temperature sensor (26).
14. Soldering or sintering device (10, 110, 210) according to claim 13, characterized in that a tube pointing at least in the direction of the second temperature sensor (26) is arranged in the measuring window, which tube is designed to direct infrared radiation emitted by the components (16, 18) or by the said component(s) (12) of the soldering or sintering device (10, 110, 210) in the direction of the second temperature sensor (26) and preferably to shield the second temperature sensor (26) from infrared radiation which was not emitted by the components (16, 18) or by the said component(s) (12).
15. Soldering or sintering device (10, 110, 210) according to one of claims 12 to 14, characterized in that the components (16, 18), the at least one heat source (20), the at least first temperature sensor (24), and the at least second temperature sensor (26) are arranged in or on a gas-tight process chamber (28) with an adjustable process atmosphere, in particular a vacuum, wherein preferably the second temperature sensor (24) is arranged on a side of the heat source (20) facing away from the components (16, 18).