Reflow soldering furnace with at least one gas purification system comprising catalyst unit

Abstract

The present application relates to a reflow soldering furnace (1) for soldering an electronic circuit board (300), the furnace (1) comprising a gas purification system (11, 21) for purifying a gas containing a flux component evaporated from the electronic circuit board (300). The gas purification system further comprises at least one gas purification unit (11, 21) comprising a catalyst unit comprising a catalyst material. The invention further relates to a corresponding reflow soldering method.

Description

[0001] This application is a divisional application of an invention patent application with an international application date of January 26, 2016, an international application number of PCT / US2016 / 014915, a national application number of 201680008469.7, and an invention name of "Reflow soldering furnace with at least one gas purification system containing a catalyst unit". Technical Field

[0002] The present invention relates to a reflow oven and method for reflow soldering. Background Art

[0003] According to U.S. Pat. No. 7,766,651 B2, a reflow oven includes, inter alia: an ambient gas purification device including a recovery device to recover a portion of the ambient gas containing evaporated flux components during soldering; a heating device to heat the recovered ambient gas to a desired temperature; an oxidation catalyst to burn the flux components contained in the heated ambient gas; and a return device to return the high-temperature gas after combustion to the heating chamber. According to the description of the U.S. Pat. No. 7,766,651 B2, the ... flux components in the ambient gas are effectively burned, the temperature of the heating chamber is controlled without using a specific cooling device, and the necessary heating in the heating chamber is reduced. Summary of the invention

[0004] The inventors have found that this is still disadvantageous, namely the cleaning efficiency of the gas cleaning device is low. Therefore, an object of the present invention is to enhance the cleaning efficiency of the gas cleaning device.

[0005] This object is achieved by the subject matter of the independent claims; preferred embodiments are specified by the dependent claims.

[0006] In particular, the object is achieved by a reflow soldering furnace for soldering electronic circuit boards, the furnace comprising a gas purification system for purifying gas containing flux components evaporated from the electronic circuit boards, wherein the gas purification system comprises at least one gas purification unit including a catalyst unit containing catalyst material.

[0007] The objects of the present invention are also specifically achieved by a method for reflow soldering of electronic circuit boards by means of a reflow soldering furnace, wherein a gas containing flux components evaporated from the electronic circuit boards is purified by a gas purification system, whereby at least one gas purification unit comprising a catalyst unit containing catalyst material is used to purify the gas.

[0008] Thereby, the gas can be cleaned more efficiently. The different gas cleaning units can be adapted to the amount of steam in the zone or group of zones to which the respective gas cleaning unit is dedicated. Thus, the cleaning capacity / energy can be adapted to the required level at a certain zone in the furnace.

[0009] Preferably, the gas may be air or a specific inert gas or inert gas mixture used inside a welding furnace, for example like nitrogen.If an air flow is mentioned, this means an air flow or a gas flow or both, depending on the type of gas inside the furnace.

[0010] Preferably, the gas cleaning unit has a cleaning device configured to clean the gas according to the following cleaning principle: at least catalyst cleaning and preferably additionally cleaning by condensing evaporated flux components on a condenser within the gas cleaning unit. The condenser is preferably a component or area inside the gas cleaning unit that features a surface area equipped with cooling means for condensing the vapors on this surface area. The gas cleaning unit can be arranged inside or outside the furnace using a suitable air / gas ducting system.

[0011] In a further preferred embodiment according to the present invention, the furnace comprises a control unit which controls (or is configured or programmed to control) the temperature of the gas impinging on the catalyst material of at least one gas cleaning unit, preferably two, three, more and / or all gas cleaning units within the range of 180-215° C. In a further preferred method according to the present invention, the temperature of the gas impinging on the catalyst material of at least one gas cleaning unit is controlled within the range of 180-215° C.

[0012] Thus, extremely energy-efficient operation is possible. Surprisingly, it was found that the cleaning performance at such low temperatures is sufficient. For efficient operation in this low temperature range, preferably, the catalyst material comprises at least one metal from the platinum group, particularly preferably two or more metals from the platinum group. Particularly preferably, the catalyst temperature of the gas impinging on the catalyst material of the at least one gas purification unit is controlled to 210°C.

[0013] In yet another preferred embodiment or method according to the present invention, at least one gas cleaning unit is dedicated to the cooling area of ​​the reflow soldering oven.

[0014] Thereby, the air in the cooling zone can be cleaned effectively without having an influence or only a minimal influence on the cooling performance. The cooling zone is well known to those skilled in the art. The cooling zone is a zone after or following the reflow zone. Preferably, the gas in the cooling zone is controlled so that the gas has a temperature in the range of 70°C-110°C, preferably 80°C-100°C. The set point of the cooling unit in the cooling zone is preferably 90°C. Preferably, the temperature of the gas impinging on the catalyst material of at least one gas purification unit dedicated to the cooling zone is controlled in the range of 180-215°C or preferably at 210°C, which provides advantageous cooling and cleaning efficiency.

[0015] In a further preferred embodiment according to the invention, the furnace comprises a clean exhaust port or a plurality of clean exhaust ports, through which the gas to be cleaned by the at least one gas cleaning unit can be discharged, for example, from the furnace. In a further preferred method according to the invention, the gas to be cleaned is discharged through the clean exhaust port.

[0016] The outlet opening is preferably an aperture in the inner wall of the furnace.

[0017] In another preferred embodiment according to the present invention, the furnace comprises

[0018] a blower box chamber having air permeable walls, preferably perforated walls, facing the path of travel of the electronic circuit board and preferably separating / bounding the blower box chamber from the path of travel;

[0019] a return chamber preferably adjacent and particularly preferably surrounding on at least two or three sides;

[0020] and a fan configured to draw gas from the return chamber, blow the gas into the blower box chamber and subsequently blow it through the wall onto the electronic circuit board, wherein the blower box includes a clean exhaust port, a pipe is connected to the clean exhaust port and to the inlet of the gas cleaning unit. In a further preferred method according to the invention, the fan is operated to draw gas from the return chamber, blow the gas into the blower box chamber and subsequently blow it through the perforated wall onto the electronic circuit board.

[0021] Thereby, the unit uses an overpressure (generated by the fans in the area of ​​the blower box chamber, respectively) to convey the gas through the furnace. The gas preferably travels through the cleaning device without an additional fan or motor; it is integrated in the existing furnace concept, using the fan that is usually already present in the blower box. Moreover, at the same time, the air flow is optimized and furnace maintenance is usually less necessary than in the case of a reversed air flow, since the fans work in a cleaner environment. The pipe piece can equally replace another kind of duct, such as a channel or the like.

[0022] Preferably, the fan is arranged in close proximity to or adjacent to an orifice connecting the blower box chamber and the return chamber. Preferably, the path of travel of the gas through the return chamber to the fan at the location of the electronic circuit board is longer than the path of travel from the fan through the blower box to the electronic circuit board. Thus, the contaminated gas has a longer time to condense, for example on the walls of the return chamber. Preferably, the return chamber at least partially surrounds the blower box and has at least one vertical outer wall. The vertical outer wall can advantageously be used to collect condensed flux components.

[0023] Preferably, a plurality of zones of the furnace each comprise such an arrangement of a blower box chamber and a return chamber.

[0024] In a further preferred embodiment according to the invention, the return chamber comprises a clean inlet to which a pipe is connected and which is connected to the outlet of the gas cleaning unit. In a further preferred method according to the invention, air is sucked from the catalyst into the return chamber through the clean inlet by a fan.

[0025] Thereby, moreover, the negative pressure serves to enhance the air flow through the catalyst.

[0026] In a further preferred embodiment according to the invention, the clean exhaust port extends (preferably horizontally) transversely to the path of travel of the electronic circuit board. In a further preferred method according to the invention, the gas is exhausted by a clean exhaust port extending transversely to the path of travel of the electronic circuit board.

[0027] Thereby, an enhancement relative to homogeneous air purification is provided. Preferably, the extension of the exhaust opening horizontally transversely to the travel path of the electronic circuit board is at least 30%, preferably at least 50%, particularly preferably at least 75% and most preferably at least 90% of the inner horizontal width of the furnace (perpendicular to the travel direction).

[0028] In yet another preferred embodiment or method according to the invention, a clean exhaust port, in particular such a clean exhaust port extending transversely to the travel path of the electronic circuit board, is arranged between two zones of the reflow soldering oven.

[0029] Thereby, the cleanliness levels of the local air in two adjacent areas can be advantageously separated.

[0030] In yet another preferred embodiment or method according to the present invention, one of the two zones of the reflow soldering oven is a peak (or reflow) zone, while the other zone follows in the travel direction of the electronic circuit board and is a cooling zone.

[0031] Thereby, the catalyst of the gas cleaning unit can clean in particular this most polluted gas.Preferably, the gas can be recirculated in the outlet baffle (gas curtain) of the furnace.

[0032] The peak region and the cooling region are regions well known to those skilled in the art and are referred to as different stages of the reflow soldering thermal profile.

[0033] In a further preferred embodiment according to the invention, the gas purification system is connected to the furnace using a gas conduit system, wherein the gas conduit system comprises a venturi pump (injector) having an injection connector for external gas feed so that the external gas accelerates the gas flow inside the gas conduit system. In a further preferred method according to the invention, the external gas is injected into the gas conduit system to accelerate the gas flow inside the gas conduit system.

[0034] Thereby, the gas flow through the catalyst is enhanced. Preferably, a gas source of (comparably cleaned) inert gas, such as nitrogen, is connected to the injection connector of the venturi pump. The inert gas is injected / purged into the connector and the overpressure is used to accelerate the air flow inside the conduit system / catalyst. Preferably, the gas cleaning unit is arranged outside the furnace, for example on the outer casing of the furnace.

[0035] In a further preferred embodiment according to the invention, the furnace comprises a duct connecting the outlet of at least one gas cleaning unit to the gas curtain at the inlet or outlet of the furnace. In a further preferred method according to the invention, the gas from the catalyst is recirculated into the gas curtain at the outlet or inlet of the furnace.

[0036] Thus, specific clean air can be used for the air curtain, which is important to prevent contamination of electronic circuit boards. Due to the catalyst, the process gas is quite clean and hardly any dust is found in the pipes or processing areas after the catalyst. The air curtain prevents air from entering the furnace. Preferably, the outlet of the catalyst is connected to both the upper and lower air curtains at the outlet or inlet of the furnace.

[0037] In a further preferred embodiment according to the invention, the venturi pump is arranged in a part of the conduit system connecting the at least one gas cleaning unit to the furnace, and the outlet of the at least one gas cleaning unit is connected to the gas curtain at the inlet or outlet of the furnace. In a further preferred method according to the invention, external gas (preferably nitrogen) is blown into a part of the conduit system connecting such a gas cleaning unit to the furnace, the gas cleaning unit having an outlet connected to the gas curtain at the inlet or outlet of the furnace.

[0038] Thereby, the air curtain air quality is further enhanced.Preferably, the injection takes place in a part of the duct system which connects the inlet of the gas cleaning unit to the furnace.

[0039] In another preferred embodiment according to the present invention, the gas purification system comprises at least two gas purification units, wherein the at least two gas purification units are dedicated to different areas of the reflow soldering furnace. In another preferred method according to the present invention, at least two gas purification units are used to purify gas originating from different areas of the reflow soldering furnace.

[0040] Thereby, the gas can be cleaned more effectively. The different gas cleaning units can be adapted to the amount of steam in the zone or group of zones to which the respective gas cleaning unit is dedicated. Thus, the cleaning capacity / energy can be adapted to the required level at a certain zone in the furnace.

[0041] Preferably, there are more than two gas cleaning units, such as 3, 4, 5 or more. Preferably, each zone or group of zones of the welding furnace has its own dedicated gas cleaning unit. Preferably, the gas cleaning unit additionally comprises a particle filter, such as a particle filter after the catalyst.

[0042] Preferably, each of the at least two gas cleaning units comprises a gas inlet and an outlet, the gas inlet being configured to direct gas from an electronic circuit board inside the furnace to the interior of the gas cleaning unit, for example to the catalyst material, and the outlet being configured to direct the cleaned gas from the interior of the gas cleaning unit, for example from the catalyst material, back to the interior of the furnace or to the outside of the furnace. Preferably, each of the at least two gas cleaning units defines an air / gas cycle or a part of such a cycle, which forces the gas through the gas cleaning unit, for example through the catalyst material of the respective gas cleaning unit. At least one or each of the at least two gas cleaning units may further comprise a device for controlling the air flow (actively: for example, a fan; and / or passively: for example, a predetermined or adjustable orifice) and / or a heating element for heating the gas to a temperature optimized or suitable for cleaning, for example, for catalysis with the catalyst material. Preferably, one or more of the gas cleaning units comprises a particle filter, for example, a metal or paper filter.

[0043] Preferably, one gas cleaning unit at least partially conducts the cleaned gas from its interior, for example from its catalyst material, further into another of the at least two gas cleaning units. The first gas cleaning unit thus acts as a pre-filter. The second gas cleaning unit draws in gas not only from the first gas cleaning unit but also from at least one different area of ​​the furnace and / or even from a further gas cleaning unit; thus, the second gas cleaning unit merges at least two different air flows.

[0044] Preferably, the zone of the reflow soldering oven is the zone inside the oven and through which the circuit board to be soldered travels. Preferably, this is the zone that is being controlled to maintain stable temperature and / or air flow conditions. Typically, the reflow soldering oven has a plurality of such zones that differ from one another in terms of controlled temperature and / or air flow conditions in order to produce a desired temperature / air flow distribution along the circuit board stroke (e.g., in order to produce a certain preheating time, soaking time, reflow time, and cooling time along the stroke). Particularly preferably, the zones of the reflow soldering oven are defined by having their own temperature control (e.g., using zone-specific heaters) and / or air flow control (e.g., using zone-specific fans and / or zone-specific air flow determining perforations). Preferably, the zones are separated from one another by gap zones that do not have air flow perforations below and / or below the circuit board stroke.

[0045] Preferably, at least two gas purification units dedicated to different areas can be understood as a gas purification unit dedicated to a specific area or area group and another gas purification unit dedicated to a different area or a different area group. If there is or is not at least one area in a group that is different from other areas or area groups, there are different area groups. Preferably, dedicated to an area further means that at least 75%, preferably at least 90%, of the gas directed to the dedicated gas purification unit originates from the area or area group dedicated to the gas purification unit. For example, the gas purification unit has an air flow with an intake volume of 100 volume units per minute (however, for example, the gas in each area circulates with an air flow of 1000 volume units per minute), at least 75 volume units per minute originate from the area dedicated to the gas purification unit, and less than 25 volume units per minute originate from other places, such as adjacent areas.

[0046] Example of gas purification units dedicated to zones: a first gas purification unit may be dedicated to zone 1, a second gas purification unit may be dedicated to zone 2 only or to a group containing zone 1 and zone 2. Another example: a first gas purification unit may be dedicated to zone 1, zone 2 and zone 3, and a second gas purification unit may be dedicated to zone 3 and zone 4.

[0047] In a further preferred embodiment according to the invention, the furnace comprises two ducts:

[0048] a first conduit connecting the outlet of at least one of the at least two gas cleaning units to the gas curtain at the inlet of the furnace,

[0049] A second conduit connects the outlet of another of the at least two gas cleaning units to the gas curtain at the outlet of the furnace.

[0050] Thus, the efficiency of the system is enhanced. The length of the conduit can be minimized. For example, one gas purification unit is arranged closer to the inlet of the furnace, while another gas purification unit is arranged closer to the outlet of the furnace. Preferably, the outlets of several gas purification units (e.g., gas purification units of zones 1 and 2 and / or 3) are combined into a gas curtain at the inlet or outlet of the furnace.

[0051] In a further preferred embodiment or method according to the invention, at least one gas cleaning unit or several or all of the existing gas cleaning units are preferably arranged outside the furnace and each housed in a housing having an extension in a horizontal direction parallel to the travel direction of the electronic circuit board. x and an extension portion e along a vertical direction perpendicular to the traveling direction of the electronic circuit board z , where e x >e z .

[0052] As a result, the air flow is enhanced and the space is used very advantageously. x / e z >=2, preferably =3. Preferably, the housing is a horizontally extending cylinder, and preferably the cylinder axis is substantially parallel to the travel direction of the electronic circuit board.

[0053] In yet another preferred embodiment or method according to the present invention, at least two of the different areas are arranged consecutively to each other along a traveling direction of the electronic circuit board.

[0054] Thereby, different gas cleaning units are dedicated to different areas along the direction of travel of the circuit board.Vapor variations are particularly expected along the direction of travel when the temperature / air flow profile changes along this direction, and thus the gas cleaning units can advantageously adapt to the vapor variations.

[0055] Successive to one another in the running direction of the electronic circuit board is preferably understood to be an arrangement of at least two zones in which the circuit board first passes through one of these zones and subsequently through the other of these zones when running through the oven.

[0056] In a further preferred embodiment according to the present invention, at least two gas purification units differ from each other in at least one of the following aspects:

[0057] air flow through a gas cleaning unit;

[0058] the amount of heating or cooling of the gas (preferably within a gas cleaning unit);

[0059] The amount of particles filtered (preferably in a gas cleaning unit);

[0060] A cleaning principle or a combination of cleaning principles implemented by the gas cleaning unit, wherein the cleaning principle is one of the following: catalyst cleaning, cleaning by condensing evaporated flux components on a condenser in the gas cleaning unit. In a further preferred method according to the invention, the air flow through at least two gas cleaning units and / or the heating or cooling by the at least two gas cleaning units are controlled differently and / or correspondingly different amounts of particle filtration or different cleaning principles or a combination of cleaning principles are used.

[0061] The cleaning performance of the gas cleaning unit can thereby be adapted advantageously and in a flexible manner to locally different cleaning requirements.

[0062] Preferably, the air flow through the gas cleaning units dedicated to areas where there is high evaporation due to the welding process, such as areas corresponding at least in part to the reflow phase of the welding process, is set or controlled to a higher level than the air flow through the gas cleaning units dedicated to areas where there is low or lower evaporation due to the welding process, such as areas corresponding at least in part to the soaking phase of the welding process. Preferably, the different air flows in the different gas cleaning units are achieved by different configured means for controlling (actively: e.g., fans; and / or passively: e.g., predetermined or adjustable orifices) the air flows. Thereby, the local different evaporations in the furnace are compensated by the different air flow conditions of the different gas cleaning units.

[0063] Preferably, the amount of gas heating by a gas cleaning unit dedicated to an area where high temperatures are present due to the welding process, such as an area corresponding at least in part to the reflow phase of the welding process, is set or controlled to a lower level (or even to zero) compared to the amount of gas heating by a different gas cleaning unit dedicated to an area where low or lower temperatures are present due to the welding process, such as an area corresponding at least in part to the soaking phase of the welding process. Preferably, heating the gas in different amounts in different gas cleaning units is achieved by different configuration means for controlling the heating or by the absence of heating in one gas cleaning unit and the presence of heating in another gas cleaning unit. The different amounts of heating use locally different temperatures in the furnace. Heating is performed only where necessary and thus energy consumption is reduced.

[0064] Furthermore, in the case where the gas cleaning units have condensers for cleaning the gas, the amount of cooling of the gas by a gas cleaning unit dedicated to areas where high temperatures exist due to the welding process (e.g., areas corresponding at least in part to the reflow phase of the welding process) is set or controlled to a higher level than the amount of cooling of the gas by a different gas cleaning unit dedicated to areas where low or lower temperatures exist due to the welding process (e.g., areas corresponding at least in part to the soaking phase of the welding process). Preferably, cooling the gas by different amounts in different gas cleaning units is achieved by different configuration means for controlling cooling (e.g., different sized or controlled condensers) or by the absence of cooling in one gas cleaning unit and the presence of cooling in another gas cleaning unit. The different cooling uses locally different temperatures in the furnace.

[0065] Preferably, the amount of filtered particles in areas with a higher particle incidence in the gas is higher than in areas with a lower particle incidence. For example, the particle filter has a higher filter density or a higher number of layers to produce a higher particle filtering amount, wherein the particle filter has a lower filter density or a lower number of layers to produce a lower particle filtering amount; alternatively, the particle filter is present in one gas purification unit and not in another gas purification unit.

[0066] Preferably, one of the at least two gas cleaning units is arranged for catalyst cleaning (ie comprises a catalyst unit containing catalyst material) and another of the at least two gas cleaning units is arranged for cleaning by condensation.

[0067] It is obvious that different adaptation methods (air flow, heating, cooling, particle filtration, cleaning principle) can be combined with each other, thereby influencing the necessary / advantageous degree of adaptation of the gas cleaning unit to the dedicated area in each other. This has been made possible by the present invention because different gas cleaning units are dedicated to different areas.

[0068] In a further preferred embodiment according to the invention, one of the at least two gas purification units comprises a catalyst unit comprising catalyst material. In a further preferred method according to the invention, a correspondingly configured gas purification unit is used.

[0069] Thereby, gas purification can be performed well at higher temperature levels. Depending on the usual process temperatures inside the area to which the gas purification unit is dedicated, this is more efficient than cooling the gas by a condenser.

[0070] Preferably, the catalyst material comprises an oxidation catalyst. Preferably, the catalyst material is arranged according to a honeycomb structure. It may alternatively have a bead structure (eg ceramic catalyst balls) or a plate structure.

[0071] Preferably, more than one, such as 2, 3, 4, 5 or more or even all, of the at least two gas purification units comprise a catalyst unit comprising a catalyst material.

[0072] In a further preferred embodiment according to the present invention, at least one further gas purification unit of the at least two gas purification units comprises a catalyst unit comprising a catalyst material, so that the furnace comprises at least two catalyst units, and the at least two catalyst units differ from each other in at least one of the following aspects:

[0073] the chemical composition and / or geometry of the catalyst material,

[0074] The air flow through the catalyst material,

[0075] The amount of preheating of the gas before it impinges on the catalyst material,

[0076] Amount of particle filtering before and / or after the catalyst material. In a further preferred method according to the invention, the air flow and / or preheating through the at least two catalyst units is controlled differently and / or catalyst materials with different chemical composition and / or geometry and / or different particle filtering are used.

[0077] Thereby, the cleaning performance of the catalyst unit can be adapted advantageously and in a flexible manner to locally different cleaning requirements.

[0078] Preferably, the chemical composition of the catalyst material of a catalyst unit dedicated to areas where high temperatures are present due to the welding process (e.g. areas corresponding at least in part to the reflow phase of the welding process) is characterized by a higher optimum catalyst reaction temperature than the chemical composition of the catalyst material of a different catalyst unit dedicated to areas where low or lower temperatures are present due to the welding process (e.g. areas corresponding at least in part to the soaking phase of the welding process). Thereby, the catalyst material is advantageously adapted to the temperatures present due to the welding process and, therefore, cleaning is effective and the required amount of preheating is lower or even not necessary (e.g. when cleaning areas where low temperatures are present and the catalyst material is adapted to the lower temperatures). The chemical composition of the catalyst material compensates for the temperature differences determined by the welding process within the furnace.

[0079] Preferably, the geometry of the catalyst material is selected from honeycomb, bead and plate structures to suit the different local requirements. As an example, the selection criteria may be one or more of the following: convenience of replacement or recyclability (if the catalyst is exhausted), required or predetermined air flow through the material, price, service life taking into account the evaporation locally present in the dedicated area, the size of the catalyst produced.

[0080] Preferably, the air flow of the catalyst material through the catalyst units dedicated to areas where there is high evaporation due to the welding process (e.g. areas corresponding at least in part to the reflow phase of the welding process) is set or controlled to a higher level than the air flow of the catalyst material through the catalyst units dedicated to areas where there is low or lower evaporation due to the welding process (e.g. areas corresponding at least in part to the soaking phase of the welding process) is set or controlled to a higher level. Preferably, the different air flows in the different catalyst units are achieved by different configured means for controlling (actively: e.g. fans; and / or passively: e.g. predetermined or adjustable orifices) the air flows. Thereby, the local different evaporations in the furnace are compensated by the different air flow conditions of the catalyst material of the different catalyst units.

[0081] Preferably, the amount of preheating of gas by a catalyst unit dedicated to areas where high temperatures are present due to the welding process (e.g. areas corresponding at least in part to the reflow phase of the welding process) is set or controlled to a lower level (or even zero) than the amount of preheating of gas by a different catalyst unit dedicated to areas where low or lower temperatures are present due to the welding process (e.g. areas corresponding at least in part to the soaking phase of the welding process). Preferably, different amounts of preheating of gas in different catalyst units are achieved by different configurations for controlling preheating or by the absence of preheating in one catalyst unit and the presence of preheating in another catalyst unit. Different preheating uses locally different temperatures in the furnace. Preheating is only performed where needed and thus reduces energy consumption.

[0082] Different amounts of particle filtering have been described above and apply equally here.

[0083] It is obvious that different adaptation methods (chemical composition, geometry, air flow, preheating, particle filtration) can be combined with each other and with the above-mentioned methods for a universal gas purification unit, thereby influencing the necessary / advantageous adaptation of each other's catalyst unit to the dedicated area. This has become possible through the present invention because different catalyst units are dedicated to different areas.

[0084] In a further preferred embodiment according to the present invention, at least two of the plurality of gas cleaning units are equipped with a diagnostic system configured to measure the efficiency of the respective gas cleaning units. In a further preferred embodiment according to the present invention, the efficiency of at least two of the plurality of gas cleaning units is measured.

[0085] Thus, different efficiency states of different gas purification units can be conveniently monitored. The efficiency indicates the contamination state of the gas purification unit, such as the contamination state of the catalyst material, so that there is no need to replace all gas purification units at once and only those exhausted gas purification units need to be replaced. When different gas purification units are used, this enhances convenience and cost. The diagnostic system is, for example, a measurement of the gas pressure or chemical component (e.g., glycol ether) concentration before and after the cleaning medium (e.g., catalyst material or condenser), thereby being a pressure drop measurement or a chemical component difference measurement, and if the pressure drop is too large (e.g., exceeding a threshold value) or the chemical component difference is too low, the diagnostic system sends a signal to this. The diagnostic system may also alternatively or additionally act on the absolute value of the pressure / chemical component concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 shows a functional overview of a reflow soldering oven 1 for soldering an electronic circuit board 300;

[0087] Figure 2 Shown with Figure 1 A functional overview diagram of a reflow soldering oven 1 similar to the one in FIG.

[0088] Figure 3 Shown with Figure 1 A functional overview diagram of a reflow soldering oven 1 similar to the one in FIG.

[0089] Figure 4 shows the amount of vapor along the direction of travel of an electronic circuit board within a soldering oven during operation of the oven;

[0090] Figure 5a and 5b Shows something like Figure 3 of furnace 1, however, has a finer regional gradient;

[0091] Figure 6 is through at least Figure 1 A cross-sectional view of a region 10 of yet another embodiment of a furnace 1;

[0092] Figure 7 is based at least on Figure 1 A side view of yet another embodiment of a furnace 1 is shown. DETAILED DESCRIPTION

[0093] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

[0094] Figure 1 , Figure 2 , Figure 3 , Figure 5a , Figure 5b , Figure 6 as well as Figure 7 is a functional overview diagram of a reflow soldering furnace according to the present invention, wherein: Figure 4 Roughly illustrating the amount of vapour along the direction of travel of an electronic circuit board within the oven during operation of the soldering oven. Preferably, the oven shown in the figures also comprises a similar arrangement of components on the bottom side of the electronic circuit board.

[0095] Figure 1A reflow soldering oven 1 for soldering an electronic circuit board 300 is shown. The circuit board 300 enters from the left side and leaves on the right side. The circuit board 300 is shown at a later stage as circuit board 300' located inside the oven 1. The oven 1 comprises a gas purification system for purifying gas containing flux components evaporated from the electronic circuit board 300. The gas purification system comprises at least one gas purification unit 11, which comprises a catalyst unit containing a catalyst material. Preferably (hence the dot-dash drawing style), the gas purification system comprises at least one further gas purification unit 21, wherein the two gas purification units 11, 21 are dedicated to different zones 10, 20 of the reflow soldering oven 1. Here, the gas purification unit 11 is dedicated to the zone 10, while the gas purification unit 21 is dedicated to the zone 20.

[0096] During operation of the furnace 1 , electronic circuit boards 300 are soldered and gases containing flux components evaporated from the electronic circuit boards 300 are cleaned by the gas cleaning system. Two gas cleaning units 11 , 21 are used to clean gases originating from different zones 10 , 20 .

[0097] Thereby, since the different gas purification units 11 , 21 can be adapted to the amount of vapor in the zones 10 and 20 , the gas can be purified more effectively.

[0098] Furthermore, this exemplary embodiment shows an arrangement of the different regions 10 , 20 successive to one another along the direction of travel of the electronic circuit board 300 .

[0099] Figure 2 Shown with Figure 1 1 , however, here the gas purification unit 11 is dedicated to the group of zones 10 and 20, and the gas purification unit 21 is dedicated only to zone 20. Thus, the gas purification unit 11 has a general purification function, while the gas purification unit 21 has a pre-purification or pre-filter function for the gas / air coming from zone 20. This can be used, for example, in situations where higher evaporation occurs in zone 20 than in zone 10.

[0100] Figure 3 Shown with Figure 1 1, however, the oven 1 comprises different zones 10, 20, 30 and 40, the gas cleaning unit 31 being dedicated to the zone 30 and the gas cleaning unit 21 being dedicated to the zone 20. Not all zones have a gas cleaning unit dedicated thereto. Here, the zone 20 represents a soaking zone and the zone 30 represents a reflow zone. In these zones 20, 30, most of the vapor is generated during operation of the oven 1, such as in Figure 4By this arrangement, the gas cleaning unit 21 can adapt to the lower steam volume in the area 20, while the gas cleaning unit 31 can adapt to the higher steam volume in the area 30, thereby achieving extremely effective cleaning.

[0101] Figure 5a and 5b Shows something like Figure 3 Furnace 1, however, has finer zone gradients. Figure 3 In the example, the zone 20 is composed of zones 20.1, 20.2 and 20.3, the gas cleaning unit 21.1 is dedicated to the zone 20.1, and the gas cleaning unit 21.2 is dedicated to the zone 20.2. This enables even more specific steam cleaning in the case of need. Figure 5b A furnace 1 is shown, wherein the reflow zone (at Figure 5a In the figure, the area 30 is composed of areas 30.1 and 30.2, and the gas purification unit 31 is dedicated to the areas 30.1 and 30.2. This shows how flexibly the principles of the invention can be applied to realize a locally adapted gas purification arrangement.

[0102] Figure 6 is through at least Figure 1 A cross-sectional view of a region 10 of a further embodiment of a furnace 1 of FIG. 1. The furnace 1 comprises a clean exhaust port 16 through which the gas to be cleaned by the gas cleaning unit 11 can be discharged from the furnace. The furnace 1 comprises:

[0103] a blower box chamber 12 having a perforated wall 15 facing the path of travel of the electronic circuit board 300 and separating / bounding the blower box chamber 12 from the path of travel;

[0104] a return chamber 13 adjacent to and surrounding at least two or three sides;

[0105] And a fan 14, which is configured to extract gas from the return chamber 13, blow the gas into the blower box chamber 12 and then blow it onto the electronic circuit board 300 through the perforated wall, wherein the blower box 12 includes a clean exhaust port 16, a pipe 16.1 is connected to the clean exhaust port and the pipe 16.1 is connected to the inlet of the gas cleaning unit 11. The fan is arranged adjacent to the orifice connecting the blower box chamber and the return chamber. The gas travel path from the fan through the return chamber to the fan at the location of the electronic circuit board is longer than the travel path from the fan through the blower box to the electronic circuit board. The return chamber has two vertical outer walls. Preferably, multiple areas of the furnace each include such an arrangement of the blower box chamber and the return chamber. The return chamber 13 includes a clean inlet 17, a pipe 17.1 is connected to the clean inlet and the pipe 17.1 is connected to the outlet of the gas cleaning unit 11.

[0106] Figure 7 is based at least on Figure 1 1 is a side view of yet another embodiment of a furnace 1 of FIG. The furnace 1 comprises a clean exhaust port 26 (inside the furnace 1 and therefore drawn in dotted lines) through which the gas to be cleaned by the gas cleaning unit 21 can be discharged from the furnace. The clean exhaust port 26 extends transversely to the travel path of the electronic circuit board 300. The clean exhaust port 26 is arranged between two zones 10, 20 of the reflow soldering furnace 1. The zone 10 is a peak zone, while the other zone 20 continues in the travel direction of the electronic circuit board 300 and is a cooling zone 9. The gas cleaning system is connected to the furnace 1 using a gas duct system (the pipe 26.1 is part of the duct system), wherein the gas duct system comprises a venturi pump having an injection connector 51 for external gas feed so that the external gas accelerates the gas flow inside the gas duct system.

[0107] exist Figure 6 and Figure 7 In the gas purification unit 11 (and Figure 7 The unit 21 is also accommodated in a housing having an extension portion e in a horizontal direction parallel to the traveling direction of the electronic circuit board 300. x and an extension portion e along a vertical direction perpendicular to the traveling direction of the electronic circuit board 300 z , where e x >e z The housing is a cylinder extending horizontally, and the axis of the cylinder is substantially parallel to the traveling direction of the electronic circuit board 300 .

[0108] By means of the present invention, a novel reflow oven and a novel method for reflow soldering are proposed. The reflow oven is preferably characterized by different gas purification units, which are arranged so that they clean the gas from the oven interior, which originates from different areas of the oven interior. Thereby, locally different evaporation energies are compensated and the same or even better gas purification can be achieved with lower energy or cost.

[0109] Reference numerals

[0110] 1Reflow soldering oven

[0111] 10 Regions

[0112] 11Gas purification unit

[0113] 12 Blower Box Chambers

[0114] 13 Return to Chamber

[0115] 14 Fan

[0116] 15 Perforated wall

[0117] 16. Clean the exhaust port

[0118] 16.1 Pipe fittings

[0119] 17. Clean the entrance

[0120] 17.1 Pipe fittings

[0121] 20 Areas

[0122] 20.1 Region

[0123] 20.2 Region

[0124] 20.3 Region

[0125] 21Gas purification unit

[0126] 21.1 Gas Purification Unit

[0127] 21.2 Gas Purification Unit

[0128] 26. Clean the exhaust port

[0129] 26.1 Pipe fittings

[0130] 30 Areas

[0131] 30.1 Area

[0132] 30.2 Area

[0133] 31 Gas purification unit

[0134] 40 Areas

[0135] 51 Connectors

[0136] 300 electronic circuit boards

Claims

1. A reflow soldering furnace (1) for soldering an electronic circuit board (300), the furnace (1) comprising a gas purification system for purifying gas containing flux components evaporated from the electronic circuit board (300), characterized in that: The gas purification system comprises at least one gas purification unit, the gas purification unit comprising a catalyst unit containing a catalyst material, The gas purification system is connected to the furnace (1) using a gas duct system, wherein the gas duct system includes a venturi pump having an injection connector (51) for external gas feed so that the external gas accelerates the gas flow inside the gas duct system.

2. The furnace (1) according to claim 1, wherein: The external gas is an inert gas.

3. The furnace (1) according to claim 1, wherein: The furnace comprises a control unit which controls the temperature of the gas impinging on the catalyst material of the at least one gas cleaning unit within the range of 180-215°C; and / or Wherein, the at least one gas purification unit is dedicated to the cooling area of ​​the reflow soldering furnace (1).

4. The furnace (1) according to claim 1, wherein: The furnace (1) comprises a clean exhaust port (16, 26) through which the gas cleaned by the at least one gas cleaning unit can be discharged.

5. The furnace (1) according to claim 4, wherein: The furnace (1) comprises: a blower box chamber (12) having air permeable walls (15) facing the path of travel of the electronic circuit board (300), Return chamber (13), and a fan (14) configured to draw gas from the return chamber (13), blow the gas into the blower box chamber (12) and then blow it through the wall (15) onto the electronic circuit board (300), wherein the blower box chamber (12) includes the clean exhaust port (16), the pipe (16.1) is connected to the clean exhaust port and the pipe (16.1) is connected to the inlet of the gas purification unit.

6. The furnace (1) according to claim 5, wherein: The return chamber (13) comprises a clean inlet (17) to which a pipe (17.1) is connected and the pipe (17.1) is connected to an outlet of the gas cleaning unit.

7. The furnace (1) according to claim 4, wherein: The clean exhaust port (16, 26) extends transversely to the travel path of the electronic circuit board (300).

8. The furnace (1) according to claim 4, wherein: The clean exhaust port (26) extending transversely to the travel path of the electronic circuit board (300) is arranged between two areas (10, 20, 20.1, 20.2, 20.3, 30, 30.1, 30.2, 40) of the reflow soldering furnace (1).

9. The furnace (1) according to claim 1, wherein: The gas duct system of the furnace (1) comprises a duct connecting the outlet of the at least one gas cleaning unit to a gas curtain at the inlet or outlet of the furnace (1).

10. The furnace (1) according to claim 9, wherein The venturi pump is arranged in a part of the conduit system, which connects the at least one gas purification unit to the furnace (1), and the outlet of the at least one gas purification unit is connected to the gas curtain at the inlet or outlet of the furnace (1).

11. The furnace (1) according to claim 1, wherein: The gas purification system comprises at least one further gas purification unit, so that the gas purification system comprises at least two gas purification units, wherein the at least two gas purification units are dedicated to different areas (10, 20, 20.1, 20.2, 20.3, 30, 30.1, 30.2, 40) of the reflow soldering furnace (1).

12. The furnace (1) according to claim 11, wherein The furnace (1) comprises two conduits, the first conduit connecting the outlet of at least one of the at least two gas purification units to the gas curtain at the inlet of the furnace (1), and the second conduit connecting the outlet of another of the at least two gas purification units to the gas curtain at the outlet of the furnace (1).

13. The furnace (1) according to claim 12, wherein: The at least one gas purification unit or several or all of the existing gas purification units are each accommodated in a housing having an extension e in a horizontal direction parallel to the travel direction of the electronic circuit board (300). x and an extension portion e in a vertical direction perpendicular to the traveling direction of the electronic circuit board (300) z , where e x >e z .

14. A method for reflow soldering an electronic circuit board (300) by means of a reflow soldering furnace (1), wherein: Gas containing flux components evaporated from the electronic circuit board (300) is purified by a gas purification system, characterized in that: at least one gas purification unit for purifying the gas, the at least one gas purification unit comprising a catalyst unit containing a catalyst material, The gas purification system is connected to the furnace (1) using a gas duct system, wherein the gas duct system includes a venturi pump having an injection connector (51) for external gas feed so that the external gas accelerates the gas flow inside the gas duct system. The method according to claim 14 , wherein the external gas is an inert gas.

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