Device and method for reflow soldering

Abstract

Device for reflow soldering, comprising: a soldering tunnel (2) with a transport device (3) for transporting assemblies to be soldered through the soldering tunnel (2); several heating modules (4) arranged along the soldering tunnel (2), which circulate and heat a process gas forming the atmosphere of the soldering tunnel (2); and a cleaning unit (5), which cleans the process gas by means of combustion or pyrolysis, characterized in that the cleaning unit (5) is designed as a substantially enclosed cassette, which is arranged adjacent to the soldering tunnel (2).

Description

[0001] The present invention relates to a device and a method for reflow soldering, wherein the process gas is purified.

[0002] EP 3 053 691 A1 discloses a reflow soldering device which has at least two process gas purification units assigned to different zones of the soldering device. In the purification units, the process gas can be cleaned by catalytic purification using a catalyst or by condensation of the vaporized flux components onto a condenser. A subsidiary of the applicant of EP 3 053 691 A1 offers a catalyst cell for each process zone of a reflow soldering device under the trade name CATHOX (= Catalytic Thermal Oxidizer). However, two to three zones can also be purified with one catalyst cell. Similar processes to pyrolysis take place in this catalyst cell, but at significantly lower temperatures. The typical temperatures in the catalyst cells are in the range of 185°C to 250°C.These catalyst cells are equipped with granules that filter out some of the contaminants. These granules need to be replaced regularly, resulting in maintenance costs.

[0003] US patent 2007 / 0284408 A1 discloses another reflow soldering device with cleaning units for purifying the process gas. The cleaning unit comprises a heating element and a catalyst. The heating element heats the process gas to a temperature of approximately 300 to 400°C and feeds the heated gas to the catalyst. The catalyst decomposes the flux components in the process gas into water and carbon dioxide. The soldering device has several zones, such as an inlet zone, an outlet zone, a heating zone, and a cooling zone. Multiple cleaning units, each assigned to a specific zone, can be incorporated.

[0004] A similar reflow soldering device with a cleaning unit is described in US 2008 / 0014542 A1. This reflow soldering device has a flow sensor for measuring the gas flow through the cleaning unit. The flow rate can be set and regulated so that the gas heated in the cleaning unit does not need to be cooled before being returned to one of the process zones of the soldering device. For this to work, the flow rate must not be too high, otherwise too much hot, cleaned process gas would be returned. While this known device avoids cooling the cleaned process gas, it also limits the amount of process gas that needs to be cleaned.

[0005] US patent 2008 / 0295686 A1 discloses a reflow soldering device in which process gas is purified by condensing the impurities contained therein.

[0006] Furthermore, reflow soldering devices are known in which impurities are removed using a pyrolysis process, with or without a catalyst. In this process, the process gas is heated to temperatures of 300 to 500°C, causing the impurities to convert into water and carbon dioxide. This process produces short-chain molecules, inorganic residues, water vapor, and carbon dioxide (CO2). These substances either no longer condense within the soldering device or can be easily filtered out. Reflow soldering devices typically have a separate cleaning station to which a portion of the process gas is directed. In the cleaning station, the process gas is purified using pyrolysis. The process gas is then cooled and returned to the actual soldering device via a line. This line is usually a flexible plastic (or aluminum) hose with a diameter of a few centimeters.The use of such a hose requires cooling of the purified process gas.

[0007] EP 1 787 926 B1 discloses a support device for a transport system used to move assemblies, such as those used in reflow soldering equipment. This support device allows the spacing of continuous, circulating transport chains to be adjusted and the chains to be tensioned. Therefore, this support device has two tensioning and adjustment directions for setting and tensioning two parallel transport chains, located at both ends of the support device.

[0008] The present invention is based on the objective of creating a device and a method for reflow soldering with which the process gas can be effectively cleaned.

[0009] Another object of the present invention is to provide a device and a method for reflow soldering with which the process gas can be purified, wherein the device or the method is easy to implement.

[0010] Another object of the present invention is to create a device and a method for reflow soldering that can be operated very energy-efficiently.

[0011] One or more of the aforementioned problems are solved by the subject matter of the independent claims. Advantageous embodiments are specified in the respective dependent claims.

[0012] According to a first aspect of the present invention, a device for reflow soldering is provided, comprising - a soldering tunnel with a transport device for transporting assemblies to be soldered through the process chamber, - several heating modules arranged along the soldering tunnel, which circulate and heat a process gas forming the atmosphere of the soldering tunnel, - a cleaning unit which cleans the process gas preferably by means of a pyrolysis process and / or by combustion.

[0013] The device is characterized by a channel that directs the process gas cleaned by the cleaning unit from the cleaning unit to several of the heating modules, so that the cleaned process gas is distributed to several heating modules and mixes with the process gas contained in the heating modules. This channel is hereinafter referred to as the process gas distribution channel.

[0014] Depending on whether or not a catalyst is provided in the purification unit and depending on the type of catalyst used, the process gas must be heated to a temperature of approximately 250 to 700°C. The purified process gas is distributed to several heating modules via the channel according to the invention, and the heat contained in the purified process gas is distributed to these modules accordingly. The purified process gas mixes with the process gas circulating in the area of ​​the respective heating modules. Depending on the amount of heat supplied by the purified process gas, the heating effect of the heating modules can be reduced. Since the heat supplied by the purified process gas is distributed to several heating modules, overheating of the process gas in the area of ​​a single heating module is prevented. Therefore, it is not necessary to cool the purified process gas.The heat generated during the cleaning of the process gas can therefore also be used to heat the process gas in the process chamber. This allows the energy consumption of the reflow soldering machine with cleaning unit to be kept low compared to conventional reflow soldering machines with cleaning units.

[0015] Since the purified process gas is distributed across several heating modules, it is also not necessary to restrict the flow of process gas to be purified to the purification unit, as is known, for example, from US 2008 / 0014542 A1.

[0016] By distributing the purified process gas to several heating modules, a corresponding quantity of gas is displaced from the area of ​​each heating module and conveyed to the cleaning unit. The displaced gas can be forced through the process chamber, and in particular through a soldering tunnel formed within the process chamber, to a central outlet opening, from which it is routed to the cleaning unit via a suitable line. However, a further channel is preferred, which has openings in the area of ​​the heating modules to which purified process gas is conveyed, in order to discharge unpurified process gas to the cleaning unit. This further channel is referred to below as the process gas collection channel.

[0017] Furthermore, by distributing the purified process gas across several heating modules in the soldering device, only a single cleaning unit or a few cleaning units are required, so that during maintenance of the soldering device, the dirt accumulating on the cleaning unit(s) only needs to be removed from one or a few locations.

[0018] In combustion cleaning, the process gas contains oxygen, so at least some of the contaminants are burned. Pyrolysis, on the other hand, is carried out with a process gas that is free or essentially free of oxygen. The end products of combustion and pyrolysis differ somewhat.

[0019] The channels are preferably made of a heat-resistant material that can withstand at least the temperatures of the purified process gas. The channels may be delimited by metal sheets.

[0020] Preferably, the channel or channels extend through the heating modules.

[0021] At least one process gas distribution channel and / or process gas collection channel can be provided both above and below the soldering tunnel, and these two channels can be interconnected. The two channels can also be supplied separately and directly with purified process gas from the cleaning unit. Alternatively, it may be sufficient to provide only one process gas distribution channel either below or only above the soldering tunnel to distribute the purified process gas.

[0022] The process gas distribution channels and / or process gas collection channels preferably have openings leading to the heating modules. These openings can be of different sizes to selectively distribute or collect the purified process gas at the individual heating modules. It should be noted that the size of the opening is not necessarily proportional to the respective gas flow through it. The gas flow between the respective channel and the corresponding heating module is also significantly influenced by the pressure difference between the pressure in the channel and the pressure in the heating module. Furthermore, a considerable pressure drop can occur along the channel in the direction of flow. Preferably, the openings are designed such that essentially the same gas flow to and from all heating modules is present.

[0023] The openings of the channels leading to the heating modules can also be adjustable in size. This can be achieved using flaps, slides, etc. These adjustment elements can be manually adjustable, allowing a specific distribution of the process gas flow to the individual heating modules to be set before commissioning the reflow soldering device. These adjustment elements can also be equipped with an actuator that can be operated during the operation of the reflow soldering device. Preferably, the actuator is connected to a control unit so that the channel openings are automatically adjusted depending on predetermined parameters. These parameters are, in particular, the pressure and / or the temperature prevailing in the respective heating module.

[0024] Preferably, the process gas distribution channels and the process gas collection channels are designed as channels that share at least one common wall, so that the purified and unpurified process gas flow countercurrently. These channels act as heat exchangers, cooling the purified process gas and heating the unpurified process gas. This reduces the energy required for purification in the purification unit. Preferably, one of the two channels is largely enclosed by the other, thus achieving efficient heat transfer. In particular, the channel carrying the unpurified process gas is the one that encloses the channel carrying the purified process gas.

[0025] According to another aspect of the present invention, a device for reflow soldering is provided, comprising - a soldering tunnel with a transport device for transporting assemblies to be soldered through the process chamber, - several heating modules arranged along the soldering tunnel, which circulate and heat a process gas forming the atmosphere of the process chamber, - a cleaning unit which cleans the process gas preferably by means of pyrolysis, wherein the heating modules are designed as essentially closed cassettes which are arranged adjacent to the soldering tunnel.

[0026] This device is characterized by the fact that the cleaning unit is also designed as an essentially closed cassette, which is also arranged adjacent to the soldering tunnel.

[0027] A substantially closed cassette means that the cassette is gas-tight from adjacent cassettes, so no process gas is directly exchanged between them. However, the cassettes, at least those of the heating modules, have an opening facing the soldering tunnel, allowing process gas to be exchanged with the soldering tunnel.

[0028] The cleaning unit is integrated into the arrangement of heating modules and occupies the space of one of them. This allows the cleaning unit to be located within the housing of the reflow soldering device. The housing typically encloses the process chamber, all heating modules, and the cleaning unit. Therefore, it is not necessary to route the process gas to a cleaning unit located outside the housing and then back again. Since the cleaned process gas is usually very hot, heat losses from routing the process gas from an external cleaning unit back to the process chamber are avoided.

[0029] Preferably, the housing is thermally insulated to minimize heat loss.

[0030] The soldering device preferably has temperature zones in the process chamber, comprising at least one preheating zone and one peak zone. The peak zone is operated at a higher temperature than the preheating zone. In the preheating zone, the process gas temperature is typically no more than 200°C. In the peak zone, the process gas temperature is greater than 200°C, preferably greater than 230°C. Typically, the process gas in the peak zone has a temperature of approximately 250°C. In the peak zone, the solder located between the components and the printed circuit board melts. The cleaning unit is preferably arranged in the area of ​​the preheating zone, adjacent to the peak zone.

[0031] In the peak zone, a higher heating output is required than in the preheating zone. Therefore, it is advantageous to provide heating modules continuously both above and below the process chamber in the peak zone. On the other hand, the cleaning unit often generates a significant amount of heat, which is preferably directed to the peak zone where the greatest heat demand exists.

[0032] The cleaning unit is preferably located below the process chamber. The assemblies consist of a printed circuit board and electronic components, which are bonded to the circuit board with solder paste. The electronic components are usually located on the top side of the circuit board. Therefore, it is advantageous if the heating modules are arranged continuously, especially above the process chamber, so that the heated flow of process gas, directed from top to bottom into the process chamber, can be precisely controlled along the entire length of the process chamber.

[0033] The cleaning unit preferably includes a blower for circulating the process gas.

[0034] The cleaning unit includes a heating device for heating the process gas to be cleaned. The heating device can be designed to heat the process gas to a temperature of at least 250°C, preferably at least 300°C, and particularly at least 400°C or at least 500°C. The minimum temperature depends on the type and nature of the catalyst used. In cleaning units without a catalyst, it may be advantageous to heat the process gas to temperatures above 600°C. Temperatures of up to 700°C can be achieved in this case.

[0035] The cleaning unit may contain a catalyst. Depending on the type of catalyst, a different temperature is required in the heating module.

[0036] The cleaning unit may include a heat exchanger with which the cleaned process gas is cooled by exchanging heat with uncleaned process gas or with newly supplied process gas to the device.

[0037] This heat exchanger retains heat within the reflow soldering device as much as possible. Heat is only dissipated to the outside through the exhausted process gas or through conduction and radiation via the housing, which is preferably insulated. Cooling of the purified process gas with simultaneous heat dissipation outside the reflow soldering device does not occur. This results in significantly higher energy efficiency compared to conventional reflow soldering devices with cleaning units that purify the process gas via pyrolysis.

[0038] By providing a single, central cleaning unit, the design of the reflow soldering device is significantly simpler and more cost-effective compared to conventional reflow soldering devices with a large number of catalyst cells.

[0039] The cleaning unit can include a filter system. This filter system can have one or more cyclone filters, which very efficiently filter fine dust generated during pyrolysis or combustion. At temperatures above 500 °C, metal oxides, salts, and other particulate solids are formed. These constitute the fine dust.

[0040] The cleaning unit is preferably arranged adjacent to a clamping and / or adjusting device of the transport system. The transport system is, for example, equipped with a clamping and / or adjusting device as known from EP 1 787 926 B1. Reference is therefore made to this document in its entirety. The clamping and / or adjusting device is preferably not arranged in the peak zone, as this would require the use of materials that can be reliably used at temperatures above 200°C. It is considerably simpler to arrange the clamping and / or adjusting device outside the peak zone at lower temperatures. However, correct adjustment and tensioning of the transport chains is also required in the peak zone, so the clamping and / or adjusting device should also be arranged as close as possible to the peak zone.Therefore, the cleaning unit and one of the clamping and / or adjustment devices are arranged adjacent to each other and preferably adjacent to the peak zone.

[0041] According to a further aspect of the present invention, a method for reflow soldering of assemblies is provided, wherein the assemblies are passed through a hot process gas atmosphere, causing the solder located within the assemblies to melt. The process gas is heated by means of several heating modules arranged along a transport device and purified by means of a cleaning unit. During the cleaning of the process gas, the process gas is heated. The method is characterized in that the heated, purified process gas is directed to several heating modules and distributed among them. This distributes the heat generated during cleaning across several heating modules.

[0042] An inert gas can be used as the process gas. Nitrogen, in particular, is suitable. The process gas preferably has a nitrogen content of at least 99%, and more specifically, at least 99.9%. The process gas preferably contains an oxygen content of no more than 1000 ppm to 50 ppm. Other inert gases, such as CO2, can also be used instead of nitrogen. In practice, however, nitrogen has proven very effective because it is more cost-effective than other inert gases. Other inert gases can be added, for example, to influence heat transfer. Helium is one such inert gas.

[0043] Process gas to be cleaned can be routed from several of the heating modules to the cleaning unit. Alternatively, or in combination, it is also possible for process gas to be cleaned to be routed from the soldering tunnel to the cleaning unit.

[0044] The process gas being added to the reflow soldering device can be heated using a heat exchanger, which directs the heated, purified process gas in counterflow to the newly added process gas. This significantly accelerates the process gas exchange, as the newly added process gas is quickly heated to the required operating temperature.

[0045] The process gas to be cleaned, which is directed to the cleaning unit from several heating modules, is preferably guided in counterflow to the heated, cleaned process gas, so that heat is exchanged.

[0046] The exchange of heat between the purified, heated process gas and the process gas to be purified or the process gas to be added preferably takes place exclusively within the reflow soldering device and in particular within the housing of the reflow soldering device.

[0047] The invention is explained in more detail below by way of example with reference to the drawings. The drawing shows: Fig. 1. Schematic diagram of the construction of a reflow soldering device without a housing, Fig. 2 a section of a channel of the device Fig. 1 for distributing a purified process gas or for supplying unpurified process gas to a purification unit, Fig. 3 several heating modules and a cleaning unit in perspective view from an angle looking upwards and without a top cover, Fig. 4 elements of the cleaning unit made of Fig. 3 in perspective view and in partial section, Fig. 5 the elements from Fig. 4 in perspective view and another sectional view, and Fig. 6 the housing of a reflow soldering device with heating modules and a cleaning unit, as used in Fig. Figure 3 is shown in a perspective view from a low angle.

[0048] A device according to the invention for reflow soldering (= reflow soldering device) 1 ) includes a soldering tunnel 2 with a transport device 3 for transporting assemblies to be soldered through the soldering tunnel 2 Several heating modules are located along the process chamber. 4 arranged, which create an atmosphere in the soldering tunnel 2 Circulate and heat the forming process gas.

[0049] A cleaning unit 5 is intended for cleaning the process gas.

[0050] The cleaning unit 5 is with the heating modules 4 with one or more process distribution channels 26 connected to supply purified process gas to several of the heating modules 4 to distribute.

[0051] The transport facility 3exhibits one or more pairs of parallel continuous chains 10 , 11 on which the assemblies to be soldered are placed in the direction of conveyance 12 to be transported. The transport equipment 3 It is similarly designed to the one described in European Patent EP 1 787 926 B1. Reference is therefore made to this document in its entirety. Fig. 3 are three waves 13 , 14 , 15 shown which serve to determine the distance and / or height of the endless chains 10 , 11 to adjust. The waves 13 - 15 are rotatably mounted and each has a gear at one end 16 which interlock. The waves 13 - 15 They can also be driven individually. These shafts determine the height and width of the endless chains. 10 , 11 adjustable.

[0052] The transport facility 3extends in the direction of conveyance 12 through the entire soldering tunnel 2.

[0053] Along the transport facility 3 The heating modules are located above and below. 4 arranged approximately symmetrically to a horizontal plane. Fig. Figure 3 shows a perspective view from a slightly elevated angle of some of the heating modules. 4 and the cleaning unit 5 , which are located below the transport device 3 condition.

[0054] Above the transport facility 3 are the heating modules 4 without interruption, consecutively over a predetermined area of ​​the reflow soldering device 1 arranged. Below the transport device 3 The heating modules are essentially arranged consecutively without interruption in this predetermined area, although there is a gap at one point between two heating modules. 4 the cleaning unit5 is arranged. The cleaning unit 5 It thus occupies the position of a heating module. 4 one that is arranged above the transport device 3 is present. The heating modules 4 and the cleaning unit 5 Each module has a one-sided open, roughly cuboid-shaped housing. 17 open, each with the open side facing the transport device 3 is arranged in a pointing direction. The heating modules 4 above the transport device 3 are spaced away from the heating modules 4 and the cleaning unit 5 below the transport device 3 arranged, with this intermediate area forming the soldering tunnel 2 forms and provides sufficient space to accommodate the transport equipment 3 and the assemblies to be soldered.

[0055] A trial chamber 6This is the area where process gas is circulated, heated, and purified. The process chamber 6 This includes the interior of the heating modules. 4 , the cleaning unit 5 and the solder tunnel 2 between the upper heating modules 4 and the lower heating modules 4 or the cleaning unit 5 .

[0056] The module housing 17 Each consists of two longitudinal side walls 18 , two transverse side walls 19 and a floor wall 20 at the lower heating modules 4 or the cleaning unit 5 trained. The upper heating modules 4 They have a ceiling wall (not shown).

[0057] The transverse side walls 19 two adjacent heating modules 4 or adjacent heating module 4 and cleaning unit 5They can be formed from a common wall element. It is advantageous that the individual heating modules 4 and the cleaning unit 5 through the transverse side walls 19 are separated in such a way that process gas located inside the heating modules 4 or inside the cleaning unit 5 The process gas present should not flow directly to the adjacent heating module. 4 can flow uncontrollably.

[0058] The heating modules 4 feature a blower roller 7 which is open at both ends. The ends of the blower roller are held against the longitudinal side walls. 18 the module housing 17 such a distance is maintained that gas flows unhindered in two partial streams between the end faces of the blower rollers. 7 and the walls 18 flow in and out of the cylindrical surface of the blower rollers 7along whose length a ribbon-like gas stream can flow out. The design of the heating modules 4 This corresponds to known heating modules as described in WO 03 / 106092 A1. Therefore, full reference is made to this document.

[0059] In principle, it is also possible to design the heating modules differently, for example with a laterally arranged blower and corresponding process gas guide elements, as described, for example, in WO 2010 / 031864 A1. Reference is also made to this document in its entirety.

[0060] The cleaning unit of the present embodiment comprises a blower. 21 for circulating the process gas, a heating device 22 for heating the process gas, optionally a catalyst 23 and a filter system 24for filtering the heated process gas, wherein the process gas flows through the heating device, the catalyst, and the filter device in that order. In the present embodiment, the heating device 22 is integrated into the blower. 21 integrated. However, it is also possible to remove the blower. 21 at another location, for example after the filter system 24 to provide so that the air can pass through the individual elements 22 , 23 and 24 is being vacuumed.

[0061] Furthermore, the cleaning unit 5 a heat exchanger 25 on, which is between the catalyst 23 and the filter system 24 is arranged to remove the material in the catalyst 23 to cool escaping hot process gas before it passes through the filter device 24 is guided. The heat exchanger 25is designed in such a way that the hot process gas is either mixed with fresh process gas supplied from the outside and / or with gas from the individual heating modules. 4 The process gas to be cleaned is cooled in counterflow. In the present embodiment, the heat exchanger 25 in the direction of flow in front of the filter device 24 arranged. In principle, however, it is possible that the heat exchanger, with respect to the process gas flowing from the catalyst, is also located after the filter unit. 24 It can be arranged.

[0062] The catalyst is an oxidation catalyst, which initiates a pyrolysis or combustion reaction in the process gas to break down contaminants, primarily water and CO. 2- and ash particles are supported. The ash particles are removed by means of the filter system. 24The filtered components are removed using a fine-pored filter membrane. Instead of, or in combination with, a filter membrane, a filter system in the form of one or more cyclone filters can also be used. The filter system must be adapted to the end products of the pyrolysis or combustion reaction. The temperature used also influences the nature of the end products.

[0063] The cleaning unit 5 is connected to the process gas distribution channel 26 connected, which at least to some heating modules 4 leads to the routing of the hot, purified process gas to several heating modules. 4 serves this purpose. In the present embodiment, this process gas distribution channel is 26 with all heating modules 4 tied together ( Fig. 1, Fig. 2).

[0064] The reflow soldering device 1 has a process gas collection channel 27which process gas from several heating modules 4 collected and sent to the cleaning unit 5 is routed. In the present embodiment, the process gas collection channel connects 27 all heating modules 4 with the cleaning unit 5 .

[0065] The process gas collection channel 27 The guided process gas is cooler than the gas in the cleaning unit. 5 Heated, purified process gas is distributed via the process gas distribution channel. Therefore, it is advantageous if the process gas collection channel 27 at least adjacent to the process gas distribution channel, so that heat exchange occurs between the process gas in both channels. 26 , 27 This can be done. Preferably, the process gas collection channel encloses 27 at least in some sections of the process gas distribution channel 26 ( Fig. 2) Such a formation of the process channels 26 , 27represents a heat exchanger in which the hot, purified process gas to be distributed is cooled and the gas to be cleaned is cooled in the cleaning unit. 5 The process gas to be supplied is heated.

[0066] The reflow soldering device 1 a case 28 ( Fig. 6) on, that the heating modules 4 , the cleaning unit 5 and the solder tunnel 2 completely encloses. Preferably, the walls of the housing are 28 thermally insulated.

[0067] The process gas distribution channel 26 has several distribution openings 29 each of which is located inside a heating module 4 open. In the present embodiment, all distribution openings 29 They are all the same size. However, within the scope of the invention, it is also possible to design the distribution openings differently. 29to design differently. In particular, it can be useful to design the distribution openings, which lead to heating modules. 4 which lead further from the cleaning unit 5 are further away, larger than the distribution openings 29 , which are in heating modules 4 discharges that are closer to the cleaning unit 5 are arranged to form. Since the purified, heated process gas dissipates with increasing distance from the purification unit. 5 As it cools down, the distance to the respective heating module can increase. 4 More process gas is supplied.

[0068] Furthermore, it may be useful to adjust the distribution openings. 29 to be designed with adjustable flaps or sliders, so that the opening cross-section of the distributor openings 29The distribution of the manifold openings is individually adjustable. This adjustment can be made manually. However, it can also be advantageous to use electrically controlled actuators so that the opening cross-section of the manifold openings can be adjusted via a central control unit and changed during operation of the reflow soldering device. This makes it possible to individually design and change the distribution of the heated, purified process gas during operation. For example, it can be adjusted depending on the temperature of the purified, heated process gas as it exits the cleaning unit. 5 escapes, discontinuing distribution.

[0069] The process gas collection channel 27 has collection openings 30 each of which is located inside one of the heating modules 4 empty into the ground. Through the collection openings. 30 Process gas flows from the heating modules. 4 into the process gas collection channel 27, that from the blower 21 is drawn in. In the present embodiment, all collecting openings have 30 The same opening cross-section. However, it can also be advantageous to design the collecting openings with different opening cross-sections. The collecting openings can also be equipped with a flap or a slide to individually adjust the opening cross-section of each collecting opening. The adjustment can be made manually or via an electronically controlled actuator.

[0070] In the present embodiment, the process gas distribution channel 26 and the process gas collection channel 27 designed to penetrate the module housings 17 extend through it. Only a short vertical section of the channels 26 , 27 extends through the soldering tunnel 2 Since the channels 26 , 27 essentially within the module housings17 The heat transported with the heated, purified process gas also remains within the module housings. 17 and thus within the trial chamber 6 .

[0071] The heat-exchanging elements, such as the heat exchanger 25 and the counter-current channels 26 , 27 , are located inside the housing 28 They serve solely for the exchange of heat between parts of the process gas that is located in housing 28 or that is outside the housing 28 No heat exchanger is provided to cool the purified process gas relative to a medium located outside the reflow soldering device. 1 and especially outside the housing 28 The process gas is located within the reflow soldering unit. Therefore, no cooling of the purified process gas occurs against an external medium. The heat thus remains within the reflow soldering unit. 1or inside the housing 28 This reflow soldering device 1 It is therefore subject exclusively to the heat losses known from conventional reflow soldering devices that do not have a cleaning unit, such as through the escape of process gas when the assemblies exit the reflow soldering device and through heat conduction and heat radiation through the walls of the housing. 28 through. Conventional reflow soldering devices with a central cleaning unit are designed such that the cleaning unit is arranged outside the housing of the reflow soldering device, wherein the cleaned process gas is cooled against a medium outside the reflow soldering device, in particular the ambient air, so that the cleaned process gas can be fed directly into the process chamber 2 at any point.

[0072] According to the invention, the process gas distribution channel 26the purified, heated process gas onto at least several heating modules 4 distributed, to which the heated, purified process gas mixes with the gas in the heating modules. 4 The existing process gas is mixed so that the cleaning process in the cleaning unit is carried out in a way that allows the process to be carried out in a way that is effective during cleaning. 5 The heat generated is distributed across several heating modules. 4 The process gas is distributed throughout the reflow unit. This eliminates the need to cool the purified and heated process gas against an external medium. The heat can therefore remain entirely within the reflow soldering unit. This results in significant energy savings compared to conventional reflow soldering units with a central cleaning unit.

[0073] Furthermore, the cleaning module is integrated into the reflow soldering device. 1 and especially within the housing 28 arranged so that the cleaning unit 5 generated heat within the reflow soldering device 1 or within the housing 28is produced and remains there.

[0074] There are reflow soldering machines with a variety of decentralized cleaning elements. However, these operate at relatively low temperatures, which limits their cleaning effectiveness. By incorporating a central cleaning unit... 5 or a few central cleaning units (e.g., two to six or two to four cleaning units) it is possible to use one or a few cleaning units 5 It operates efficiently at a relatively high temperature, at which a very efficient breakdown of the contaminating components of the process gas is possible. Nevertheless, the heat required for cleaning is not released to the outside, but rather transferred to the individual heating modules. 4 distributed so that the heating modules are distributed 4 The generated heating output can be reduced accordingly. Reference symbol list 1 Reflow soldering device 2 solder tunnels 3 Transport equipment 4 Heating module 5 Cleaning module 6th Trial Chamber 7 Blower roller 8 9 10 Endless chain 11 Endless chain 12 Direction of conveyance 13th wave 14 wave 15 wave 16 gear 17 module housings 18 Longitudinal side wall 19 transverse side wall 20 floor wall 21 blowers 22 Heating system 23 Catalyst 24 filter unit 25 heat exchangers 26 Process gas distribution channel 27 Process gas collection channel 28 cases 29 Distributor opening 30 Collection opening QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3053691 A1

[0002] US 2007 / 0284408 A1

[0003] US 2008 / 0014542 A1 [0004, 0015] US 2008 / 0295686 A1

[0005] EP 1787926 B1 [0007, 0040, 0051] WO 03 / 106092 A1

[0058] WO 2010 / 031864 A1

[0059]

Claims

[1] Device for reflow soldering comprising - a soldering tunnel (2) with a transport device (3) for transporting assemblies to be soldered through the soldering tunnel (2), - several heating modules (4) arranged along the soldering tunnel (2), which circulate and heat a process gas forming the atmosphere of the soldering tunnel (2), - a cleaning unit (5) which cleans the process gas preferably by means of combustion or pyrolysis, characterized by , that a process gas distribution channel (26) is provided which directs the process gas cleaned by the cleaning unit (5) from the cleaning unit (5) to several of the heating modules (4), so that the cleaned process gas is distributed to several heating modules (4) and mixes with the process gas located in the heating modules (4). [2] Device according to claim 1, characterized by , that the process gas distribution channel (26) extends through the heating modules. [3] Device according to claim 1 or 2, characterized by , that at least one process gas distribution channel (26) is provided both above and below the soldering tunnel (2), wherein the two process gas distribution channels (26) are interconnected in a communicating manner. [4] Device according to any one of claims 1 to 3, characterized by , that a process gas collection channel (27) is provided to direct process gas from one or more heating modules (4) to the cleaning module. [5] Device according to any one of claims 1 to 4, characterized by , that the channels (26, 27) have openings (29, 30) which lead to the heating modules (4), the openings (29, 30) having different sizes in order to distribute the purified process gas to the individual heating modules (4) in a targeted manner. [6] Device according to any one of claims 1 to 5, characterized by, that the channels (26, 27) have openings (29, 30) which lead to the heating modules (4), wherein the size of the openings (29, 30) is adjustable. [7] Device according to any one of claims 1 to 6, characterized by , that the channel(s) (26, 27) are made of heat-resistant material, so that purified process gas can be passed through the channel(s) (26, 27) without prior cooling. [8] Device according to any one of claims 4 to 7, characterized by , that the process gas distribution channel (26) and the process gas collection channel (27) are adjacent to each other in such a way that purified process gas is directed from the cleaning unit to the heating modules and unpurified process gas is directed from the heating modules to the cleaning unit in countercurrent flow. [9] Device for reflow soldering, in particular according to one of claims 1 to 8, comprising - a soldering tunnel (2) with a transport device (3) for transporting assemblies to be soldered through the soldering tunnel (2), - several heating modules (4) arranged along the soldering tunnel (2), which circulate and heat a process gas forming the atmosphere of the soldering tunnel (2), - a cleaning unit (5) which cleans the process gas preferably by means of combustion or pyrolysis, wherein the heating modules (4) are designed as substantially closed cassettes which are arranged adjacent to the soldering tunnel (2), characterized by , that the cleaning unit (5) is also designed as a substantially enclosed cassette, which is also arranged adjacent to the soldering tunnel (2). [10] Device according to any one of claims 1 to 9, characterized by , that the device (1) has a housing (28) that encloses the soldering tunnel (2), all heating modules (4) and the cleaning unit (5). [11] Device according to claim 10, characterized by , that the housing (28) is thermally insulated. [12] Device according to any one of claims 1 to 11, characterized by , that the device (1) is designed with zones of different temperatures in the soldering tunnel (2), wherein at least one preheating zone and one peak zone are provided, wherein the peak zone has a higher temperature than the preheating zone and the cleaning unit (5) is arranged at the preheating zone adjacent to the peak zone. [13] Device according to any one of claims 1 to 12, characterized by , that the cleaning unit (5) is arranged below the soldering tunnel (2). [14] Device according to any one of claims 1 to 13, characterized by , that the cleaning unit (5) has a blower (21) for circulating the process gas. [15] Device according to any one of claims 1 to 14, characterized by, that the cleaning unit (5) has a heating device (22) for heating the process gas in order to clean it by means of combustion or pyrolysis, wherein the process gas is preferably heated to a temperature of at least 500°C. [16] Device according to any one of claims 1 to 15, characterized by , that the cleaning unit (5) has a catalyst (23). [17] Device according to any one of claims 1 to 16, characterized by , that the cleaning unit (5) has a heat exchanger (25) with which the cleaned process gas is cooled by exchanging heat with uncleaned process gas or with process gas newly supplied to the device. [18] Device according to any one of claims 1 to 17, characterized by , that the cleaning unit (5) includes a filter device (24). [19] Device according to claim 18, characterized by that the filter assembly (24) comprises one or more cyclone filters. [20] Device according to any one of claims 1 to 19, characterized by that the cleaning unit (5) is arranged adjacent to a clamping and / or adjusting device (13-15) of the transport device (3). [21] Method for reflow soldering of assemblies, wherein the assemblies are passed through a hot process gas atmosphere so that a solder located in the assemblies melts, wherein the process gas is heated by means of several heating modules (4) arranged along a transport device (3) and is cleaned by means of a cleaning unit (5), wherein the process gas is heated during the cleaning process gas, characterized by that the heated, purified process gas is directed to several heating modules (4) and distributed among these heating modules (4). [22] Method according to claim 21, characterized by , that a device according to one of claims 1 to 20 is used. [23] Method according to claim 21 or 22, characterized bythat an inert gas, in particular a gas with a nitrogen content of at least 99% and preferably at least 99.9%, is used as the process gas. [24] Method according to any one of claims 1 to 23, characterized by , that process gas to be cleaned is directed from several of the heating modules (4) to the cleaning unit (5). [25] Method according to any one of claims 21 to 24, characterized by , that when replacing process gas with newly added process gas, the newly added process gas is heated by means of a heat exchanger (25) with which the heated, purified process gas is passed in counterflow to the newly added process gas. [26] Method according to any one of claims 21 to 25, characterized by , that heated, purified process gas from the cleaning unit (5) to the heating modules (4) is guided in counterflow to process gas to be purified from the heating modules (4) to the cleaning unit (5) in order to exchange heat. [27] Method according to claim 25 or 26, characterized by , that the exchange of heat is carried out exclusively within a housing (28) of a reflow soldering device (1).

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