Negative-pressure unit for a soldering system, soldering system, and methods for operating a negative-pressure unit, for generating a characteristic map and for starting up the negative-pressure unit

Abstract

The invention relates to a negative-pressure unit for a soldering system, comprising a negative-pressure chamber and a negative-pressure pump which is designed to pump chamber gas out of the negative-pressure chamber during operation, in order to lower a chamber pressure in the negative-pressure chamber to below an ambient pressure surrounding the negative-pressure chamber, and comprising a controllable ventilation valve having different degrees of opening according to control. The invention also relates to a soldering system having a negative-pressure unit. The invention also relates to a method for operating a negative-pressure unit, to an additional method for generating a characteristic map for reading out a degree of opening of a first ventilation valve by means of a target chamber pressure of a negative-pressure unit, to an additional method for generating a characteristic map for reading out a switch-off pressure of a negative-pressure pump by means of a target chamber pressure, and to an additional method for starting up a negative-pressure unit.

Description

[0001] Title: Vacuum unit for a soldering system and soldering system and method for operating a vacuum unit, for generating a characteristic map and for commissioning the vacuum unit

[0002] Description

[0003] The invention relates to a vacuum unit for a soldering system, with a vacuum chamber and a vacuum pump which, during operation, is designed to pump chamber gas out of the vacuum chamber in order to reduce a chamber pressure prevailing in the vacuum chamber below an ambient pressure surrounding the vacuum chamber. The invention also relates to a soldering system with a vacuum unit. The invention further relates to a method for operating a vacuum unit, a further method for generating a characteristic map for reading out a degree of opening of a first venting valve above a target chamber pressure of a vacuum unit, a further method for generating a characteristic map for reading out a cut-out pressure of a vacuum pump above a target chamber pressure and a further method for commissioning a vacuum unit.

[0004] Using soldering systems, particularly ref low soldering systems, so-called SMD components (Surface Mounted Devices) are soldered onto the surface of circuit boards using solder paste. The solder paste, which is generally a mixture of solder metal granules, flux and pasty components, is applied or printed onto the surface of the circuit board for reflow soldering. The components to be soldered are then placed in the solder paste. In the ref low soldering process, the item to be soldered, i.e. the assembly consisting of circuit board, solder paste and components to be soldered, is preheated along the process channel in a preheating zone and heated in a soldering zone to a temperature which is above the melting point of the solder paste. This melts the solder paste and the solder joints are formed.

[0005] In order to remove gas bubbles, also called voids, from the solder joints that have not yet solidified, it is known, for example from DE 10 2019 125 983 Al and DE 10 2019 128 780 Al, to provide a vacuum or negative pressure unit with a negative pressure chamber in the soldering zone.

[0006] The soldering material is placed in the vacuum chamber once the solder has melted. The chamber pressure is reduced below the ambient pressure so that the gas bubbles in the liquid solder escape from the solder. The vacuum chamber must then be vented back to the ambient pressure. The vacuum must be rebuilt for each soldering process, since the

[0007] Vacuum chamber must be opened to remove the soldering material.

[0008] In the vacuum chamber, gas bubbles in the liquid solder only rise from a soldering point when a certain negative pressure is reached or undershot. A vacuum pump pumps gas out of the vacuum chamber during the evacuation process in order to reduce the chamber pressure. If this negative pressure is undershot too quickly, however, the bubbles rise too quickly and burst on the surface. This leads to solder spatter, which can create short circuits on the circuit board. Furthermore, a chamber pressure that is too far below a certain negative pressure is problematic because it cannot be ruled out that sensitive components will be destroyed. Faulty solder joints with poor or no contact between the connections can also result. Contamination of the solder material and differences in quality lead to rejection. Faulty solder joints are one of the most common causes of failure in the operation of electronic components.Adjusting the vacuum is also problematic, as once a vacuum is reached, the pressure continues to change due to the inertia of the vacuum unit after the evacuation process is switched off. Therefore, it is not possible, or only with great effort, to adjust the pressure in the vacuum chamber both precisely and reproducibly over multiple soldering cycles.

[0009] After the soldering zone, the solder is cooled in a cooling zone until the molten solder solidifies in the solder joints before the solder is removed from the reflux soldering system. The object underlying the invention is to improve the quality of solder joints and avoid rejects, particularly due to component damage.

[0010] This object is achieved by a vacuum unit according to claim 1. The vacuum unit is designed in particular for a reflow soldering system and has a vacuum chamber and a vacuum pump. The vacuum pump is designed to pump chamber gas out of the vacuum chamber in order to reduce a chamber pressure prevailing in the vacuum chamber. The reduced chamber pressure is below an ambient pressure surrounding the vacuum chamber. Furthermore, a first controllable venting valve is provided which, depending on the control, has different degrees of opening. The first venting valve is provided for venting the vacuum chamber or a vacuum region connected to the vacuum chamber and located between the vacuum chamber and the vacuum pump. Furthermore, a control unit is provided for controlling the first venting valve and for switching the vacuum pump on and / or off.

[0011] The vacuum pump can be switched on and off by switching the pump itself on and off.

[0012] It can preferably also be achieved by having the pump run continuously, the pump being connected to the vacuum chamber, in particular by a valve when switched on, so that it pumps out chamber gas, and being separated from the chamber, in particular by the valve when switched off, so that no chamber gas is pumped out. While the vacuum pump is switched on, it pumps chamber gas out of the vacuum chamber, the output of the vacuum pump preferably being constant, so that a desired target chamber pressure is reached after a certain period of time. The period of time is generally always the same for a particular vacuum pump, but can vary due to environmental influences. When using a different vacuum pump, in particular with a different output, the period of time can be different.

[0013] A target chamber pressure is the chamber pressure that should be reached or set. The time period is the time it takes until the target chamber pressure is reached. However, this time period can differ from the time the vacuum pump is switched on, as the vacuum unit system has a certain inertia, and the chamber pressure can continue to drop or rise again after it is switched off.

[0014] Depending on the set opening level of the vent valve, a different time period can be achieved. By providing a controllable vent valve with different opening levels depending on the control, the time period can be variably adjusted and, in particular, extended, thus reliably removing gas bubbles in the liquid solder and protecting sensitive components.

[0015] Depending on the degree of opening of the vent valve, inert gas can be fed into the chamber or ambient air can be fed into the vacuum area, which means that the vacuum pump has to pump out a larger volume of gas. The additional gas through the vent valve thus ensures pressure equalization. The time period can be adjusted by adjusting the degree of opening of the vent valve. The greater the degree of opening of the vent valve, the longer the time period until a target chamber pressure is reached. If the degree of opening is large, the pump has to be switched on for longer to reach a target chamber pressure, i.e. it has to pump for longer. A certain pressure reduction in a certain period of time is also referred to as a pressure gradient, i.e. a pressure change per period of time, which can include both pressure reductions and pressure increases.Overall, this allows for a gentle yet effective removal of gas bubbles in the liquid solder without damaging sensitive components.

[0016] It is advantageous if the control unit is set up in such a way that it adjusts the degree of opening before and / or while the vacuum pump is switched on.

[0017] It is further advantageous if at least one sensor is provided for measuring the chamber pressure and if the control unit is set up in such a way that it switches the vacuum pump on and / or off depending on the measured chamber pressure. It is conceivable that the sensor is provided on the vacuum chamber, in the vacuum chamber or connected to the vacuum chamber. By providing the sensor, the vacuum pump can be switched off at a switch-off pressure in order to set the target chamber pressure as precisely as possible. Furthermore, by measuring the chamber pressure, a repeatable setting of the target chamber pressure can be achieved. If the switch-off pressures are known for achieving the respective target chamber pressures at a set degree of opening, the control unit can switch off the vacuum pump and control the venting valve accordingly, so that ultimately the target chamber pressure can be produced repeatedly with the pressure gradient.Different pressure gradients are also conceivable in a single duty cycle to achieve the target chamber pressure.

[0018] The process starting from ambient pressure until a target chamber pressure is reached can be referred to as the degassing process. The venting valve can also be used to raise the chamber pressure back to ambient pressure after the degassing process has been completed, so that the vacuum chamber can then be opened and the soldering material can be removed from the vacuum chamber. After the evacuation process, i.e. after the vacuum pump has been switched off and before venting, it is advantageous if the target chamber pressure is held for a period of time. This can be achieved by closing the venting valve. This allows the set target chamber pressure to take effect during the holding period and the gas bubbles can be more effectively removed from the soldering point. This holding period is also part of the degassing process.

[0019] It is advantageous if the control unit is configured such that the degree of opening is adjusted as a function of a desired chamber pressure to be achieved, a control value, and / or as a function of at least one further process parameter. It is further advantageous if the vacuum pump is switched on, in particular switched off, as a function of a desired chamber pressure to be achieved, a control value, and / or as a function of at least one further process parameter.

[0020] It is conceivable that an input device is provided for entering the control value. It is also conceivable that the input device is provided for entering the target chamber pressure and / or the holding time period. The input device can also be a mobile device such as a mobile device or an app on a mobile device. It is further conceivable that the input device is designed such that different control value ranges can be selected and that the control unit is set up such that the degree of opening is adjusted depending on the control value ranges and / or the vacuum pump is switched depending on the control value ranges.

[0021] It is conceivable that a normalized degree of opening is included in the control value. In this context, "normalized" means, in particular, that the degree of opening is normalized with respect to a maximum adjustable degree of opening with which a target chamber pressure is still achieved; the normalized degree of opening is normalized between a closed degree of opening and the maximum adjustable degree of opening.

[0022] The control value is preferably a value between 1% and 100%, whereby the control value is related to the pressure gradient. For example: If a control value of 100% is entered, the target chamber pressure is set with the largest pressure gradient. The chamber pressure is therefore reduced as quickly as possible. The degree of opening would therefore always be closed at a control value of 100%. If a control value of 1% is entered, the target chamber pressure is set with the smallest possible pressure gradient. The chamber pressure is therefore reduced as slowly as possible. The degree of opening is set so that it is opened to the maximum extent that the target chamber pressure can just be reached.

[0023] Advantageously, the input device is designed such that different control value ranges can be selected, and the control unit is configured such that the degree of opening is adjusted depending on the control value ranges and / or the vacuum pump is switched depending on the control value range. This has the advantage that different target chamber pressures with different or identical pressure gradients can be set one after the other without the need for further input. Advantageously, at least five control value ranges can be selected.

[0024] Preferably, one further process parameter depends on components to be soldered, a soldering item, a solder, a circuit board, a soldering task and / or the assembly of the vacuum chamber. The component to be soldered is an individual component that is to be soldered onto a circuit board. As already mentioned, components can be destroyed if the pressure is reduced too quickly, i.e. if the pressure gradient is too high, or if the pressure is too low. It is therefore advantageous if the adjustment is made according to the corresponding component properties. The same applies to the soldering item. Furthermore, the adjustment can be made based on the individual properties of the soldering agents used, in particular the solder and flux, and of the circuit board. The assembly is the fill level between a full or empty vacuum chamber with components to be soldered and / or soldering item.The soldering task is part of the soldering process itself and can include temperatures, which in turn are taken into account in the setting.

[0025] It is further conceivable for the control unit to be set up in such a way that the degree of opening and / or the switching, in particular the switching off, of the vacuum pump is automatically calculated from CAD data, image data, data from a database and / or a data sheet. This is particularly advantageous when there are different components, different soldering items and soldering tasks, since the vacuum unit does not have to be set up again for each change of components, soldering items or soldering task. Advantageously, at least one camera is provided in or on the vacuum unit to capture the soldering item and / or the components to be soldered in order to generate image data.

[0026] It is conceivable that the vacuum chamber is provided between the first venting valve and the vacuum pump and / or that the venting valve is provided for venting the vacuum chamber with inert gas. The inert gas, for example nitrogen, can preferably originate from an inert gas reservoir, for example from a gas cylinder or an inert gas environment around the vacuum chamber.

[0027] It is advantageous if the first venting valve between the vacuum chamber and the vacuum pump is provided for ventilating the vacuum area between the vacuum chamber and the vacuum pump with gas.

[0028] Advantageously, the first vent valve is a flow control valve with two ports. It is also conceivable for a 2 / 2-way valve to be arranged between the first vent valve and the vacuum area. The 2 / 2-way valve is advantageously designed to switch the vent valve on and off. To switch on, the vent valve is connected to the vacuum area, and to switch off, the vent valve is separated from the vacuum area.

[0029] The first venting valve is advantageously designed as a bypass valve with at least three connections. A first connection is preferably designed as a chamber connection for connection to the vacuum chamber. A second connection is preferably designed as a venting connection. A third connection is preferably designed as a pump connection for connection to the suction side of the vacuum pump. The vented vacuum region in the first venting valve is advantageously located between the first connection and the third connection. It is advantageous if a second venting valve is provided for venting the vacuum chamber. It is conceivable that the first venting valve is designed with a check valve provided on the first connection.Such a valve arrangement has the advantage that the degree of opening of the first vent valve is independent of the second vent valve and thus of the venting of the vacuum chamber. This allows the target chamber pressure to be set more precisely.

[0030] The second connection of the bypass valve is advantageously connected to the ambient air. The atmosphere in the vacuum chamber, as well as in an entire process channel in a soldering system, is usually filled with an inert gas, such as nitrogen. The reason for this is that the soldering points do not oxidize with oxygen from the ambient air. Nitrogen is a special process substance that must be kept separately. If the second connection of the bypass valve is connected to the ambient air, the chamber gas is mixed with the ambient air during operation before it is sucked off by the pump. This has the advantage that nitrogen is saved and does not have to be introduced into the chamber during pumping. A further advantage is that the first venting valve does not have to be located in the process channel or on the chamber, but can be arranged in a more advantageous location in terms of installation space.

[0031] It is conceivable that the second venting valve has a first connection connected to an inert gas reservoir and a second connection connected to the vacuum chamber. This allows the vacuum chamber to be advantageously vented with an inert gas, for example, nitrogen.

[0032] It is also conceivable for the second venting valve to be designed as a controllable venting valve with varying degrees of opening depending on the control. This allows the pressure gradient to be adjusted after the end of the holding period during venting, similar to the first venting valve. This reduces the risk of component damage due to an excessively rapid pressure increase with an excessively large pressure gradient.

[0033] Advantageously, the control unit is configured to read out a degree of opening of the first ventilation valve and a cut-off pressure of the vacuum pump from at least one characteristic map as a function of a target chamber pressure and a control value. Further advantageously, the control unit is configured to set the degree of opening read out from the characteristic map at the first ventilation valve and to switch the vacuum pump on as a function of the cut-off pressure read out from the characteristic map and the measured chamber pressure. The characteristic map contains at least control variables for the bypass valve, connection points and cut-off points of the vacuum pump as a function of the target chamber pressure and control value. It is also conceivable for the characteristic map to contain the control variables as a function of the holding time period. This advantageously enables control of the pressure gradient and / or the target chamber pressure.It is also conceivable to regulate the pressure gradient and / or the target chamber pressure based on the measured chamber pressure.

[0034] The object underlying the invention is also achieved by a soldering system according to claim 14. The soldering system is, in particular, a reflux soldering system with a vacuum unit according to the invention. A vacuum unit according to the invention in a soldering system improves the entire soldering process by reducing quality differences in the solder joints and thus reducing waste. Furthermore, energy and process materials, such as nitrogen, are advantageously saved.

[0035] The object underlying the invention is also achieved by a method for operating a vacuum unit according to the invention according to claim 15 . The method therefore comprises the following steps: a ) input of at least one target chamber pressure and a control value for achieving the target chamber pressure; b ) generation of control signals by reading the

[0036] Degree of opening and the cut-off pressure from at least one characteristic map; c) controlling the first ventilation valve and switching the vacuum pump by means of the generated control signals to set and achieve the desired chamber pressure.

[0037] This method combines the input of target values ​​with precise and repeatable machine control.

[0038] Such a method is advantageous because, from an input of simple and understandable parameters, control signals for controlling the vacuum unit are generated in order to set the entered parameters precisely and repeatably.

[0039] Advantageously, steps b) and c) are carried out continuously until the desired chamber pressure is set and reached. In step b), the generation of control signals can also be dependent on a chamber pressure measured by the sensor, and in step c), the control and switching can be carried out using the newly generated control signals. This has the advantage of more precise control by feeding the measured chamber pressure back into the generation of corresponding control signals for setting the desired values.

[0040] Advantageously, the method comprises a further step d), wherein steps b) and c) are repeated in several stages to set and achieve more than one target chamber pressure. This is advantageous if more than one desired target chamber pressure and / or one control value is entered in step a). It is also conceivable that step a) is carried out more than once in order to enter different target chamber pressures and / or different control value ranges.

[0041] The object underlying the invention is also achieved by a method according to claim 18 for generating a characteristic map for reading out a degree of opening of a first venting valve above a target chamber pressure of a vacuum unit according to the invention. The method comprises the following steps: a) setting a degree of opening of the first venting valve and switching on the vacuum pump; b) switching off the vacuum pump when the measured chamber pressure remains at least largely constant and storing a minimum measured chamber pressure and the set degree of opening in a characteristic map. This is particularly the case when the pressure no longer changes or changes only slightly within a waiting time, wherein the waiting time can in particular be 20 seconds; and c) repeating steps a) to b) with differently set degrees of opening.

[0042] It is advantageous if the chamber pressure before step a) is equal to the ambient pressure.

[0043] It is conceivable that the stored degree of opening is standardized to a minimum control value for the pressure achievable at the stored pressure and is thus stored in the characteristic map. The object underlying the invention is also achieved by a method according to claim 19 for generating a characteristic map for reading a cut-off pressure of a vacuum pump against a target chamber pressure of a vacuum unit according to the invention.The method therefore comprises the following steps: a) switching on the vacuum pump to reach a target chamber pressure and recording a profile of the chamber pressure; b) switching off the vacuum pump as soon as the measured chamber pressure matches the target chamber pressure; c) continuing to record the profile and save the profile until a waiting time has elapsed or the chamber pressure is at least largely constant; d) determining the inertia of the vacuum unit based on the profile after the vacuum pump has been switched off and determining a switch-off pressure as a function of the chamber pressure, taking the inertia into account, and saving the switch-off pressure in the characteristic map; and e) repeating steps a) to d) with different target chamber pressures, in particular with the saved pressures from a characteristic map generated according to claim 18.

[0044] The methods according to the invention for generating the characteristic maps are preferably carried out sequentially. It is also conceivable for both methods according to the invention to generate a common characteristic map.

[0045] These methods according to the invention both have the advantage that the vacuum unit is able to learn itself automatically, in particular in the case of changing environmental influences, aging processes of machine components such as seals on the vacuum chamber and / or replacement of components after maintenance. In the first method, it is first determined which chamber pressure can be achieved with which maximum degree of opening. In the second method, the inertia of the vacuum unit is determined and the control is adapted in such a way that the dynamic system of the vacuum unit can nevertheless set the chamber pressure precisely and repeatably. The desired accuracy of the chamber pressure lies in particular in a tolerance range of 50 mBar below the target chamber pressure.

[0046] Environmental influences include, for example, the geographical elevation of the vacuum unit's location or weather conditions. Using this method, new characteristic maps can be created at any time, quickly and without great effort, so that the target chamber pressure can be set precisely and repeatably within a certain time period during operation of the vacuum unit.

[0047] The procedures for generating the characteristic maps can be carried out in particular at regular intervals, after each machine start or when the machine is started up and / or after service work.

[0048] The object underlying the invention is also achieved by a method according to claim 21 for commissioning the vacuum unit according to the invention. The method thus comprises the following steps: a) triggering the generation of at least one characteristic map according to one of the methods according to the invention; and b) providing the at least one characteristic map for the operation of the vacuum unit.

[0049] The method allows a vacuum unit, particularly in a soldering system, to be easily commissioned by generating and providing the characteristic map with the vacuum unit's parameters. This simplifies the subsequent setting of a target chamber pressure and makes it reproducible.

[0050] Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which embodiments of the invention are described and explained in more detail.

[0051] It shows :

[0052] Figures 1 and 2: different embodiments of a vacuum unit;

[0053] Figures 3 and 4: different embodiments of a ventilation valve;

[0054] Figure 5: a soldering system with a vacuum unit according to Fig. 1 or 2;

[0055] Figure 6 : a diagram of chamber pressure versus time;

[0056] Figure 7 : a process diagram for the operation of a

[0057] Vacuum unit ; Figures 8 and 9 : various process diagrams for creating different characteristic maps ; and

[0058] Figure 10 : a process diagram for commissioning a vacuum unit

[0059] Figure 1 shows one embodiment of a vacuum unit 10, and Figure 2 shows another embodiment of a vacuum unit 12. Both embodiments of the vacuum unit 10, 12 are designed to reduce a chamber pressure 14 in a vacuum chamber 16 below an ambient pressure 18 surrounding the vacuum chamber 16. For this purpose, a vacuum pump 20 is provided in each case, which pumps chamber gas 22 out of the respective vacuum chamber 16 during an evacuation process.

[0060] As described in the introduction, a vacuum unit applies a vacuum to the solder material—that is, the components to be soldered and the circuit boards populated with solder once the solder has liquefied. This is an important step in reflux soldering to remove gas bubbles or voids from the solder joint during the soldering process. Precise adjustment of the vacuum, as well as the ability to set a pressure gradient, are crucial, particularly for increasing process reliability.

[0061] For switching the respective vacuum pump 20 on and off, a control unit 24 is provided, which provides control signals via a control line 26. The vacuum pump 20 runs continuously during operation of the vacuum unit 10, 12 and is switched on or off via a valve 25 of the vacuum chamber 16. The valve 25 is either fully open or fully closed. It is also possible to provide a vacuum pump that can be switched on and off instead of the valve (not shown).

[0062] The vacuum pump 20 is activated by the control unit 24 by opening the valve 25 and, as long as it is activated, pumps chamber gas 22 from the vacuum chamber 16. When a desired chamber pressure is reached, the vacuum pump 20 is deactivated by closing the valve 25.

[0063] In order to make a pressure gradient, according to which the chamber pressure 14 is reduced, adjustable, a first venting valve 28, 30 is provided in each embodiment of the vacuum unit 10, 12. The venting valves 28, 30 have different

[0064] Embodiments, the first embodiment 28 being shown in Figure 3 and the second embodiment 30 being shown in Figure 4.

[0065] First, the functioning of the vacuum unit 10 in Figure 1 with the venting valve 28 in Figure 3 will be explained in more detail, wherein the venting valve 28 is provided for venting the vacuum chamber 16 with gas and in particular with inert gas.

[0066] Before the vacuum pump 20 is switched on, or during this process, the ventilation valve 28 is controlled by the control unit 24 and a variably adjustable degree of opening 32 is set. The degree of opening 32 is shown in a schematic representation of the ventilation valve 28 in Figure 3. The degree of opening 32 can be between 0% and 100% and in the embodiment shown designates the cross section through which the gas 34 can flow. To set the

[0067] A slide 36 is shown schematically, which can completely or partially close the cross-section 38 of the valve. The opening degree 32 is the remaining open cross-section of the vent valve 28. The slide 36 can be moved by means of a controllable adjustment unit, which is not shown. Depending on the opening degree 32, more or less gas 34 can flow through the vent valve 28 from a first connection 40 to a second connection 42. Other

[0068] Embodiments are conceivable as to how the degree of opening 32 can be adjusted, but these are not shown.

[0069] In the first embodiment 10, the first connection 40 of the venting valve 28 is connected to an inert gas environment 44 at ambient pressure 18 of the vacuum chamber 16. The environment 44 is shown as a dashed line and is intended to clarify that this is an inert gas atmosphere of nitrogen, as is created in a process channel of a soldering system.

[0070] The second connection 42 is connected to the vacuum chamber 16 in Fig. 1. This allows gas 34, in this case inert gas, to flow from the environment 44 of the vacuum chamber 16 at ambient pressure 18 into the vacuum chamber 16, depending on the degree of opening 32. The inflow of gas 34 brings about a conditional pressure equalization of the chamber pressure 14, while the vacuum pump 20 reduces the chamber pressure 14. As a result, the vacuum pump 20 has to pump for longer to reach a desired chamber pressure, which results in a slower pressure reduction than if no venting valve 28 were provided.

[0071] A pressure change over time can be referred to as a pressure gradient, in this case a pressure reduction per unit of time. For example, if the opening degree 32 is 0%, i.e. the vent valve 28 is completely closed, the pressure reduction behaves as if there were no vent valve 28. If the opening degree 32 is set to 100%, the pressure reduction occurs as slowly as possible over a long period of time with a low pressure gradient. Any values ​​between an opening degree 32 of 0% and 100% are conceivable. Ultimately, the minimum pressure gradient depends on the maximum flow rate of the vent valve at 100% opening.

[0072] A sensor 46 is provided on the vacuum unit 10. The sensor 46 measures the prevailing chamber pressure 14 and is connected to the control unit 24. The control unit 24 is configured to read and process the measured pressure 14. Based on the measured pressure 14, the control unit 24 can provide the control signals for the vent valve 28 and for switching the vacuum pump 20.

[0073] An input device 48 is provided for entering a control value S, a target chamber pressure K and a holding time T of the achieved target chamber pressure. The control value includes the pressure gradient. The input device 48 is connected to the control unit 24. The control unit 24 is configured to adjust the degree of opening 32 depending on the entered control value. Likewise, different control value ranges, preferably five stages, can be selected using the input device 48, and the control unit 24 is configured to adjust the degree of opening 32 depending on the control value ranges and to switch the vacuum pump depending on this.

[0074] Once the input has been made, the corresponding degree of opening 32 is set and the vacuum pump 20 is switched on. Once the entered target chamber pressure K is reached, the vacuum pump 20 is switched off. As soon as the target chamber pressure K is reached and any pressure holding time has elapsed, the chamber pressure 14 is increased again to the ambient pressure 18. Several target chamber pressures K one after the other in stages are also conceivable. The holding time serves to ensure that the target chamber pressure K can act for a certain time and thus the gas bubbles have time to rise from the soldering point. The pressure 14 is increased to the ambient pressure 18 via the vent valve 28 by opening the vent valve 28 and gas 34 flowing into the chamber 16 until the chamber pressure 14 is equal to the ambient pressure 18.Even when venting, i.e. when increasing the chamber pressure 14, a pressure gradient can be set via the opening degree 32 so that the chamber pressure 14 is not increased too quickly and components are not damaged.

[0075] The vacuum unit 12 according to Figure 2 has a different valve arrangement than the vacuum unit 10 according to Figure 1. The functionality of the vacuum unit 12 with respect to the adjustable degree of opening 32 for setting the desired chamber pressure K, or the pressure gradient, is similar to that for

[0076] Vacuum unit 10 described.

[0077] Unlike the vacuum unit 10 with a vent valve 28, the vacuum unit 12 has two vent valves 30 and 50. The first vent valve 30 is designed as a bypass valve 30 and is shown schematically in Figure 4. This bypass valve 30 is provided for venting a vacuum region 51 which is connected to the vacuum chamber 14 and lies between the vacuum chamber 14 and the vacuum pump 20. The components corresponding to Figure 1 are identified by corresponding reference numerals in Figure 2. The bypass valve 30 can also be constructed as a composite unit comprising a T-piece or Y-piece with three connections and a flow control valve with two connections connected to one of the three connections (not shown).

[0078] The bypass valve 30 has three connections. A first connection 52 is connected to the vacuum chamber 16, a second connection 54 is connected to the ambient air 56, and a third connection 58 is connected to the suction side of the vacuum pump 20 or to the valve 25. The suction side of the vacuum pump 20 is the side or connection through which the gas is sucked in. Furthermore, a slide 36, as described for the vent valve 28 in Figure 3, is provided to adjust the degree of opening 32 of the second connection 54. In this case, however, no inert gas is introduced into the vacuum chamber 16; instead, ambient air 56 is added to the camera gas 22 via the second connection 54, so that a gas mixture 60 of chamber gas 22 and ambient air 56 is ultimately sucked in by the vacuum pump 20 via the third connection 58. The gas mixture 60 is released from the vacuum pump 20 into the environment 62.

[0079] The vacuum region 51 between the first connection 52 and the third connection 58 is thus ventilated with ambient air 56 via the second connection 54. Depending on the degree of opening 32 of the venting valve, the vacuum pump 20 must therefore extract a larger gas volume and the pressure gradient becomes lower, as well as the time period within which the target chamber pressure K is established is extended. Such a vacuum unit 12 has the advantage over the vacuum unit 10 that no expensive process gas, such as nitrogen, has to be used to ventilate the vacuum chamber 16 during the pressure reduction.

[0080] Between the vacuum chamber 16 and the second connection 54, a further valve 63 is provided, with which the connection 54 of the bypass valve 30 can be separated from the vacuum chamber 16. The valve 63 is a 2 / 2-way valve. This ensures tightness against the negative pressure 14 prevailing in the chamber, so that no ambient air 16 can flow into the vacuum chamber 16.

[0081] The second venting valve 50 is provided for venting and increasing the reduced chamber pressure 14, in particular after completion of the degassing process, and has a first connection 64 and a second connection 66. The first connection 64 is connected to an inert gas reservoir 68 and the second connection 66 is connected to the vacuum chamber 16 via the same connection as the vacuum pump 20, although a separate connection would also be conceivable. The second venting valve 50 is advantageously constructed corresponding to the first venting valve 28 from Figure 3 and likewise has different degrees of opening depending on the control. In this way, the vacuum chamber 16 can be vented with inert gas 70 from the inert gas reservoir 68 with different pressure gradients. A further valve 71 is arranged at the second connection 66 to the vacuum chamber 16 in order to separate the venting valve 50 from the vacuum chamber 16.This ensures that no inert gas 70 flows into the chamber 16 during the degassing process and influences the chamber pressure 14. The valves 63 and 71 are also controlled by the control unit 24, but for the sake of clarity, the lines from the control unit have been omitted.

[0082] Figure 5 shows a soldering system 80 in the form of a reflow soldering system. On the left-hand side of the soldering system 80, material to be soldered (not shown) is placed into an inlet 82 of a process channel 84, which is located under hinged covers 86. A vacuum unit 10 according to Figure 1 (not shown in detail in Figure 5) or a vacuum unit 12 according to Figure 2 is provided in the process channel 84. In the process channel 84, the material to be soldered is first heated and then processed in the vacuum unit 10, 12 to remove gas bubbles in the liquid solder. The material to be soldered is then cooled again and can be removed at the outlet 90 of the process channel 84 on the right-hand side. If the vacuum unit 12 is provided, the vacuum pump 20 and the bypass valve 30 can also be provided in a lower region 88 of the soldering system 80 to save space. The vacuum pump 20 and the bypass valve 30 can be connected to the vacuum chamber 16 via a line.On the left side at input 82, an input device 48 is shown for entering control values ​​S and control value ranges for the control unit 24 arranged in the soldering system 80. It is conceivable that this input device 48 is provided for an entire soldering system control system and that the control unit 24 is integrated into a soldering system control system (not shown). Furthermore, input via a mobile control unit is conceivable, for example, via an app on a mobile device (not shown).

[0083] Various pressure curves 102, 104, 106, 108 and 110 of the chamber pressure 14 of the vacuum unit 10, 12 will be explained using the schematic diagram 100 shown in Figure 6. Time is plotted on the X-axis 112 and pressure 14 is plotted on the Y-axis. The pressure curves 102, 104, 106, 108 and 110 begin at ambient pressure 18 or pO and decrease to a minimum pressure 116. The pressure curves 102, 104, 106, 108 and 110 can generally be divided into two sections: the pressure reduction 120 and the subsequent pressure increase or venting 122. However, the times at which the pressure curves 102, 104, 106, 108, 110 change from the pressure reduction 120 to the venting 122 are different. The area markings in diagram 100 for the pressure reduction 120 and the venting 122 are exemplary for the first curve 102.

[0084] The first curve 102 begins at the ambient pressure pO or 18 and is reduced along a stepless curve to the minimum pressure 116. At time t, the pressure gradient Dl, illustrated by the dashed line, is present, i.e., the quotient of pressure change and time.

[0085] The second curve 104 has a step 124 at pressure pl fapproximately halfway between the ambient pressure 18 and the minimum pressure 116 at time t1, with the pressure p1 being held there briefly. Example values ​​for pressure 116 are approximately 10 mBar and for pressure p1 approximately 500 mBar. A slight increase in pressure is possible because the vacuum pump 20 is switched off when the pressure 14 is maintained, and the physical inertia of the system results in pressure equalization; a further pressure reduction (not shown) would also be conceivable. The pressure gradient Dl is the same for the first and second curves 102, 104; the graphs are parallel. The degree of opening 32 of the first vent valve 38, 30 is set to 0%. A control value S entered via the input device 48 would therefore be 100%, which means the fastest possible setting of the target chamber pressure K. If different target chamber pressures K with a control value S are entered, visible at the steps 124.

[0086] The third curve 106 has five stages 124; in addition to stage 124 at t1 with pressure p1, the pressures p2, p3, and p4 are also present at times t2, t3, and t4. Example values ​​for the pressures are 350 mbar for p2, 200 mbar for p3, and 50 mbar for p4. Example values ​​for the times measured from the pressure reduction from the ambient pressure 18 are approximately 1.5 s for t1, approximately 3 s for t2, approximately 4.2 s for t3, approximately 7.6 s for t4, and approximately 12.4 s for t5. An example value for a holding time T in the first stage 124 is approximately 0.8 s until the pressure p1 is further reduced; the holding times of the other stages can be the same as or different from this holding time T. The curve 106 is just as steep as the previous curves 102, 104, thus the same pressure gradient D1 is present and the degree of opening is 0%. Time t5 is the last and fifth stage, when the minimum pressure 116 is reached.The control value S entered here would be 100% and also includes the five target chamber pressures and the five stages.

[0087] The fourth progression 108 also has five steps .

[0088] Also visible is the flatter curve of the curve 108 after the first stage 124. Before the first stage 124, the pressure gradient is also equal to Dl. After the first stage 124, the pressure gradient D4 is therefore lower than the pressure gradient Dl. The degree of opening 32 is slightly open here. A control value could therefore be in the range of approximately 50%. The control value S for the curve 108 before stage 124 is therefore 100%.

[0089] The fifth gradient 110 also has five steps .

[0090] Also evident is the flatter curve of the curve 110 after the first stage 124 than that of the curve 108; the pressure gradient D5 is therefore even lower than the pressure gradient D4. The degree of opening 32 is wide open or even at 100%. A control value S could therefore be in the range of approximately 1%, which corresponds to the minimum achievable pressure gradient D5. A time offset 126 compared to the first curve 102 results from differently set pressure gradients and also the sum of the holding times T of the five stages 124.

[0091] Combinations of the pressure curves 102, 104, 106, 108, 110 with the different pressure gradients D1, D4, D5 and D6 are conceivable, as are further stage pressures and further different pressure gradients for achieving the respective stage pressures (not shown).

[0092] The degrees of opening 32, which are set in the respective stages to achieve the desired chamber pressures K, can be different for the same or similar pressure gradient.

[0093] The venting 122 after reaching the minimum target chamber pressure 116 is also made possible by the first venting valve 28 in the vacuum unit 10, and by the second venting valve 50 in the other embodiment 12. A pressure gradient D6 during venting 122 is the same for all curves 102, 104, 106, 108, 110 in the diagram 100 shown in Fig. 6. Different pressure gradients during venting 122 are also possible due to the adjustable degree of opening of the venting valves 28, 50, but are not shown in the diagram 100.

[0094] In diagram 100, the minimum pressure 116 reached is the same for all curves 102, 104, 106, 108, 110. Various higher minimum pressures between the minimum pressure 116 and the ambient pressure 18 are also conceivable, although these are not shown. Higher minimum pressures are particularly advantageous for sensitive components that can be damaged at the minimum pressure 116. Higher minimum pressures are achieved, in particular, by correspondingly higher input target chamber pressures.

[0095] In Figure 7, a method 130 is shown schematically that

[0096] Operation of the vacuum unit 10, 12 (cf. Figures 1 and 2) according to diagram 100 (cf. Figure 6). First, in a step 132, an input 136 of a control value S and a target chamber pressure K for reaching the target chamber pressure K takes place. Furthermore, a holding time period T for maintaining the target chamber pressure K after it has been reached can also be entered.

[0097] Subsequently, in a step 138, control signals 144 are generated which are based on a readout 140 of at least one characteristic map 142, 142.2 and the input 136. From the characteristic maps 142 and 142.2, the required degree of opening 32 is read as a function of the control value S, and the cut-off pressure P is read as a function of the desired chamber pressure K.

[0098] By means of the control signals 144, the vacuum pump 20 is then switched in a step 146 and the first venting valve 28, 30 is controlled to set and achieve the target chamber pressure K. Here, too, switching of the vacuum pump 25 directly or via the valve 25 is conceivable. Steps 138 and 146 are carried out continuously in a loop 148 and the generation 140 of the control signals 144 can also take place as a function of the chamber pressure 14 measured by the sensor 46. Continuously is to be understood here as meaning that steps 138 and 146 are carried out one after the other at a certain time interval, with the actual value and target value comparison of the chamber pressure taking place in the manner of a control. In such a continuous embodiment, the use of the measured chamber pressure 14 is advantageous, and an observer of the chamber pressure can also be used.

[0099] Steps 138 and 146 are also repeated after a target chamber pressure K has been set, if several target chamber pressures K have been entered in step 132. The method 130 can be executed by the control unit 24. The holding time period T influences when a further target chamber pressure K is set and / or when the chamber pressure 14 is raised again to an ambient pressure 18 by the venting valve 28, 50.

[0100] Figure 8 shows a method 150 for generating a characteristic map 142. The characteristic map 142 is used in method 130 to read out 140 a degree of opening 32 of the first ventilation valve 28, 30 above the target chamber pressure K of the vacuum unit 10, 12, wherein a measured chamber pressure 14 can also be included in the readout 140. The readout 140 is performed in particular according to method 130. The method 150 proceeds as follows:

[0101] In a step 152, the first

[0102] Opening degree 32 of the first ventilation valve 28, 30 and switching on the vacuum pump 20.

[0103] In the next step 154, the vacuum pump 20 is switched off and a minimum measured chamber pressure 14 and the set opening degree 32 are saved 155 in the characteristic map 142 if the measured chamber pressure 14 remains at least largely constant. The chamber pressure 14 is then increased again to the ambient pressure 18 and steps 152 and 154 are repeated 156 with different opening degrees 32. It is conceivable to adjust the opening degree in 5% steps per repetition so that opening degrees 32 from 0% to 100% are covered; finer or larger steps are also conceivable. A certain waiting time of approx. 20s as soon as the chamber pressure 14 is at least largely constant in order to detect possible leaks or other defects in the vacuum unit 10, 12.

[0104] It is also conceivable in step 154 ​​that the stored degree of opening 32 is standardized for each stored minimum measured pressure 14, so that later use of the characteristic map 142 is facilitated.

[0105] The characteristic map 142 can then be stored in the control unit 24.

[0106] The method 150 has the advantage that the minimum possible chamber pressures 14 for each degree of opening 32 are determined in a simple manner. The method 150 can be repeated at any time to adapt the vacuum unit 10, 12 to environmental influences and aging effects. The characteristic map 142 generated by the method has the advantage that control of the vacuum unit is simplified.

[0107] Figure 9 shows a method 180 for generating a characteristic map 142.2. The characteristic map 142.2 is used to read out 140 a cut-off pressure P of the vacuum pump 20 above the target chamber pressure K of the vacuum unit 10, 12, whereby a measured chamber pressure 14 can also be included in the readout 140. The readout 140 is carried out in particular according to the method 130. The method 180 proceeds as follows:

[0108] In a step 182, the vacuum pump 20 is switched on. During this step, a curve 184 of the chamber pressure 14 is recorded 183, as shown in diagram 100, the pressure values ​​for the recording 182 being measured by the sensor 46.

[0109] In the next step 186, the vacuum pump 20 is switched off as soon as the measured chamber pressure 14 matches the target chamber pressure K. The target chamber pressure K is, in particular, one of the pressures stored in the characteristic map 142.

[0110] Recording 183 of curve 184 continues until a waiting time has elapsed or the chamber pressure 14 is at least largely constant. The waiting time can be approximately 20 seconds, similar to that in method 150. Recording 182 is then terminated in step 188 and saved.

[0111] In step 190, the inertia of the vacuum unit 10, 12 is determined based on the curve 184 after the vacuum pump 20 has been switched off. From the determined inertia, a cut-off pressure P is then determined as a function of the chamber pressure 14, taking the inertia into account. The cut-off pressure P is immediately stored in the characteristic map 142. 2. Thereafter, a repetition 192 of steps 182 to 190 takes place with different desired chamber pressures K, in particular with the stored pressures from the characteristic map 142.

[0112] The method 180 can also include the degree of opening 32 of the ventilation valve 28, 30. Accordingly, in step 182, an opening degree 32 is also set, and in step 190, the set opening degree 32 is also saved in the characteristic map 142.2. The repetition 192 can also be carried out with different opening degrees 32 for each target chamber pressure K. The maximum possible opening degrees 32 stored in the characteristic map 142 can also be taken into account. It is conceivable to adjust the opening degree 32 in 5% steps per repetition so that opening degrees 32 from 0% to the maximum value are covered; finer or larger steps are also conceivable.

[0113] Before each repetition 192 or before step 182, the chamber pressure 14 should be increased to the ambient pressure 18; the vacuum chamber 16 is vented. Depending on the vacuum unit 10, 12, the increase is achieved through the first venting valve 28 or the second venting valve 50.

[0114] The characteristic map 142.2 generated by method 180 makes it possible to generate a precise cut-off pressure P for the precise and repeatable setting of a target chamber pressure K, even for different opening degrees 32, and to read it out during operation of the vacuum unit 10, 12. The method can be repeated at any time, particularly if ambient conditions change.

[0115] Methods 150 and 180 can be carried out independently of each other.

[0116] A method 170 for commissioning the vacuum unit 10, 12 is shown in Figure 10 and comprises the following steps:

[0117] In step 172, first the method 150 for generating the characteristic map 142 is triggered, followed by the method 180 for generating the characteristic map 142. 2.

[0118] In step 174, the characteristic maps 142 and 142.2 are provided for the operation, in particular according to method 130, of the vacuum unit 10, 12. The vacuum unit 10, 12, the soldering system 80, and the methods 130, 150, 170, 180 enable precise adjustment of the chamber pressure 14 in the vacuum chamber 16 with a predeterminable pressure gradient D1, D2, D4, D6, so that gas bubbles or voids from solder joints, particularly during reflow soldering, are removed in a way that is gentle on the components and produces little waste. A further advantage is the high accuracy of the system, with which the target chamber pressure K is achieved with a tolerance of -50 mbar.

Claims

Patent claims 1. Vacuum unit (10, 12) for a soldering system (80), with a vacuum chamber (16) and a vacuum pump (20), wherein the vacuum pump (20) is designed to pump chamber gas (22) out of the vacuum chamber (16) in order to reduce a chamber pressure (14) prevailing in the vacuum chamber (16), characterized in that a first venting valve (28, 30), which can be controlled and has different degrees of opening (32) depending on the control, is provided for venting the vacuum chamber (16) or a vacuum region (51) connected to the vacuum chamber (16) and located between the vacuum chamber (16) and the vacuum pump (20), and that a control unit (24) is provided for controlling the first venting valve (28, 30) and for switching the vacuum pump (20) on and / or off.

2. Vacuum unit (10, 12) according to claim 1, characterized in that the control unit (24) is configured such that it adjusts the degree of opening (32) of the first ventilation valve (28, 30) before and / or while the vacuum pump (20) is switched on.

3. Vacuum unit (10, 12) according to claim 1 or 2, characterized in that at least one sensor (46) is provided for measuring the chamber pressure (14) and that the control unit (24) is configured such that it switches the vacuum pump (20) on and / or off depending on the measured chamber pressure (14).

4. Vacuum unit (10, 12) according to one of the preceding claims, characterized in that the control unit (24) is set up such that the degree of opening (32) of the first venting valve (28, 30) is set as a function of a desired chamber pressure (K) to be achieved, a control value and / or as a function of at least one further process parameter.

5. Vacuum unit (10, 12) according to one of the preceding claims, characterized in that the control unit (24) is set up such that the vacuum pump (20) is switched, in particular switched off, depending on a target chamber pressure (K) to be achieved, a control value and / or depending on at least one further process parameter.

6. Vacuum unit (10, 12) according to claim 4 or 5, characterized in that the at least one further process parameter depends on components to be soldered, on the soldering material, on a soldering agent, on a soldering task and / or on the equipment of the vacuum chamber (16).

7. Vacuum unit (10, 12) according to one of the preceding claims, characterized in that the control unit (24) is set up such that an automatic calculation of the degree of opening (32) and / or the switching, in particular the switching off, of the vacuum pump (20) takes place from CAD data, image data, data from a database and / or a data sheet.

8. Vacuum unit (10) according to one of the preceding claims, characterized in that the A vacuum chamber (16) is provided between the first venting valve (28) and the vacuum pump (20) and that the venting valve (28) is provided for ventilating the vacuum chamber (16) with inert gas.

9. Vacuum unit (12) according to one of claims 1 to 7, characterized in that the first venting valve (30) is provided between the vacuum chamber (16) and the vacuum pump (20) for venting the vacuum region (51) located between the vacuum chamber (16) and the vacuum pump (20) with gas.

10. Vacuum unit (12) according to claim 9, characterized in that the first venting valve (30) is designed as a bypass valve with at least three connections (52, 54, 58), wherein a first connection (52) is connected as a chamber connection to the vacuum chamber (16), wherein a second connection (54) is designed as a venting connection and wherein a third connection (58) is connected as a pump connection to the suction side of the vacuum pump (20), and that a second venting valve (50) is provided for venting the vacuum chamber (16).

11. Vacuum unit (12) according to claim 10, characterized in that the second venting valve (50) has a first connection (64) which is connected to an inert gas reservoir (68) and a second connection (66) which is connected to the vacuum chamber (16) is connected.

12. Vacuum unit (10, 12) according to one of claims 10 to 11, characterized in that the second ventilation valve (50) is designed as a controllable ventilation valve (28) having different degrees of opening (32) depending on the control.

13. Vacuum unit (10, 12) according to one of the preceding claims, characterized in that the control unit (24) is designed to read out an opening degree (32) of the first ventilation valve (28, 30) and a cut-off pressure of the vacuum pump (20) from at least one characteristic map (142, 142.2) as a function of a desired chamber pressure (K) and a control value, and is further designed to set the opening degree (32) read out from the characteristic map (142, 142.2) at the first ventilation valve (28, 30) and to switch the vacuum pump (20) as a function of the cut-off pressure read out from the characteristic map (142, 142.2) and the measured chamber pressure (14).

14. Soldering system (80), in particular a ref low soldering system, with a vacuum unit (10, 12) according to one of the preceding claims.

15. Method (130) for operating a vacuum unit (10, 12) according to one of claims 1 to 13, comprising the following steps: a) input (136) of at least one desired chamber pressure (K) and a control value (S) for achieving the desired chamber pressure (K); b) generation of control signals (144) by reading (140) the degree of opening (32) and a cut-off pressure (P) from at least one characteristic map (142, 142.2); c) controlling the first ventilation valve (28, 30) and switching the vacuum pump (20) by means of the generated control signals to set and achieve the desired chamber pressure (K).

16. The method (130) according to claim 15, wherein steps b) and c) are carried out continuously until the setting and reaching of the desired chamber pressure (K) is achieved, and in step b) the generation of control signals (144) additionally also takes place as a function of a measured chamber pressure (14), and in step c) the control and switching takes place by means of the newly generated control signals (144).

17. Method (130) according to one of claims 15 or 16, with a further step: d) repeating steps b) and c) to set and achieve more than one target chamber pressure (K) in several stages.

18. Method (150) for generating a characteristic map (142) for reading out (140) a degree of opening (32) of a first ventilation valve (28, 30) above a target chamber pressure (K) for a vacuum unit (10, 12) according to one of the Claims 1 to 13, characterized by the following steps: a) setting a degree of opening (32) of the first ventilation valve (28, 30) and switching on the vacuum pump (20); b) switching off the vacuum pump (20) when the measured chamber pressure (14) is at least largely remains constant and storing a minimum measured chamber pressure (14) and the set degree of opening (32) in a characteristic map (142); and c) repeating steps a) to b) with differently set degrees of opening (32).

19. Method (180) for generating a characteristic map (142.2) for reading out (140) a switch-off pressure (P) of a vacuum pump (20) above a target chamber pressure (K) for a vacuum unit (10, 12) according to one of claims 1 to 13, characterized by the following steps: a) switching on the vacuum pump (20) to reach a target chamber pressure (K) and recording (183) a profile (184) of the chamber pressure (14); b) switching off the vacuum pump (20) as soon as the measured chamber pressure (14) matches the target chamber pressure (K); c) continuing to record (183) the profile (184) and storing the profile (184) until a waiting time has elapsed or the chamber pressure (14) is at least largely constant; d) Determining the inertia of the vacuum unit (10, 12) based on the curve (184) after the vacuum pump (20) has been switched off and determining a switch-off pressure (P) as a function of the chamber pressure (14) taking the inertia into account and storing the switch-off pressure (P) in the characteristic map (142.2); and e) repeating (192) steps a) to d) with different target chamber pressures (K), in particular with the stored pressures from a characteristic map (142) generated according to claim 18.

20. Method (180) according to claim 19, characterized in that the characteristic map (142.2) for reading out (140) a switch-off pressure (P) of a vacuum pump (20) is generated via a chamber pressure (14) and a degree of opening (32), wherein in step a) an opening degree (32) is set before the vacuum pump (20) is switched on, and wherein in step c) the storage is additionally carried out with the set opening degree (32), and wherein in step e) the repetition of steps a) to e) is additionally carried out with different degrees of opening (32) for each different target chamber pressure (K).

21. Procedure (170) for commissioning the vacuum unit (10, 12) according to one of claims 1 to 13, characterized by the following steps: a) triggering the generation of at least one characteristic map (142, 142.2) according to a method of claims 18 to 20; and b) providing the at least one characteristic map (142, 142.2) for the operation of the vacuum unit (10, 12).

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