CA2016718A1 - Tunnel for treating an element in a gas environment including a gas generator - Google Patents
Tunnel for treating an element in a gas environment including a gas generatorInfo
- Publication number
- CA2016718A1 CA2016718A1 CA 2016718 CA2016718A CA2016718A1 CA 2016718 A1 CA2016718 A1 CA 2016718A1 CA 2016718 CA2016718 CA 2016718 CA 2016718 A CA2016718 A CA 2016718A CA 2016718 A1 CA2016718 A1 CA 2016718A1
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- Canada
- Prior art keywords
- entry
- exit
- gas
- fluid barrier
- fluid
- Prior art date
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Abstract
ABSTRACT
An apparatus and a process are disclosed for treating an element with a reducing gas. The apparatus permits wiring boards and the like to be soldered in a reducing gas atmosphere such as hydrogen thus avoiding the necessity of fluxing. A hydrogen gas generator provides an instant source of gas and can be shut off instantly and no gas is stored.
The process comprises the steps of conveying the element through an entry into an enclosed zone, the entry containing at least one entry fluid barrier curtain wherein the fluid is an inert gas, filling the enclosed zone with the reducing gas, heating the element in the zone, conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas above the entry and exit fluid barrier curtains.
An apparatus and a process are disclosed for treating an element with a reducing gas. The apparatus permits wiring boards and the like to be soldered in a reducing gas atmosphere such as hydrogen thus avoiding the necessity of fluxing. A hydrogen gas generator provides an instant source of gas and can be shut off instantly and no gas is stored.
The process comprises the steps of conveying the element through an entry into an enclosed zone, the entry containing at least one entry fluid barrier curtain wherein the fluid is an inert gas, filling the enclosed zone with the reducing gas, heating the element in the zone, conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas above the entry and exit fluid barrier curtains.
Description
- 20167~.8 Canada TUNNEL FOR TREATING AN ELEMENT IN A GAS
ENVIRONMENT INCLUDING A GAS GENERATOR
The present invention relates to treating an element with a reducing gas soldering, and more specifically, to soldering in the presence of a reducing gas in an enclosed zone.
Soldering of printed wiring boards and other similar types of elements, without the application of flux, has a number of advantages including avoiding the step of applying : flux prior to soldering and eliminating the necessity of cleanlng the flux deposits from the solder joints after soldering. Fluxless soldering may be carried out in an inert ~15 gas atmosphere generally with a reducing agent or other : solder additions which may perform the same function as flux, that is to prevent oxidation of the solder, and provide clean solder connections. In the case of solder bath, or solder wave type of soldering, the absence of flux reduces flux deposits in the solder and when liquid solder is maintained in an inert atmosphere, there is a reduction of solder oxides known as dross that form on the solder surface.
Co-pending application filed concurrently herewith, 20~6~8 entitled Shield Ga~ Wave Soldering, Serial No.
discloses soldering in a shield gas atmosphere.
In one embodiment, soldering is achieved by conveying an element so that it is contacted by a solder wave. In another embodiment, reflow soldering is used wherein solder paste or solder plating is first applied to the metallic components to be soldered and the element is then heated so that the solder melts to liquid solder which flows to form the solder joint. -Most solder paste used for reflow soldering includes flux.
However, if reflow soldering occurs in an inert atmosphere with or without a reducing agent, then reduction of the quantity of flux or modification of the chemical nature of the flux in the solder paste can be achieved.
Co-pending application concurrently filed herewith entitled Tunnel for Fluxless Soldering, Serial No.
discloses soldering of elements, such as printed wiring boards, in a non-explosive gas atmosphere which substantially excludes oxygen.
Soldering in an enclosed zone is also disclosed in co-pending application filed concurrently herewith, entitled GasCurtain Additives Zoned Tunnel for Soldering. In this application an apparatus is disclosed for soldering an element in an enclosed zone containing a gas atmosphere. The enclosed zone has an entry and an exit and at least one fluid barrier curtain at the entry and at least one fluid barrier ~ ` , .
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curtain at the exit. The conveyor conveys an element through the fluid barrier, and in one embodiment an additive aid soldering is added to the fluid in the curtain at the entry.
In another embodiment a plurality of zones are supplied in line with a conveyor to convey elementæ through the zones.
Fluid barrier curtains are provided between the zones.
It is known to conduct wave soldering in a reducing gas atmosphere, and Bertiger in U.S. patent 4,538,757 discloses wave soldering in an enclosure containing nitrogen and hydrogen. Oxygen is excluded from the enclosure to avoid an initial fluxing step. It is disclosed in this patent that a high proportion of nitrogen in the mixture reduces the risk of an explosive mixture.
Hydrogen is often used for high temperature brazing processes and the like, and although some may consider it is not beneficial for normal soldering temperatures, i.e. 300 -400-C, the literature indicates that it is a preferred reducing gas for soldering copper circuit boards. However, it is known that hydrogen is an explosive gas and therefore the use of hydrogen in an explosive mixture presents certain hazards.
It is an aim of the present invention to treat elements in an enclosed zone with a reducing gas. The treatment may be soldering, curing, drying or other type of treatment requiring the presence of a reducing gas.
20167~ 8 It is another aim of the present invention to provide a safe soldering apparatus that utilizes an explosive gas such as hydrogen. This is achieved by combining an enclosure with gas curtains at the entry and exit, a gas generator that `;
produces only the quantity of gas necessary for the enclosure, there being no shortage of gas necessary and there being substantially instant cut off of gas supply. This avoids the necessity of storage containers of hydrogen, which even if located far from the apparatus have feed lines that risk being damaged, or can leak. Furthermore, burn-off of excess gas occurs at the gas curtains at both the entry and the exit. Thus a safe soldering apparatus where a high percentage of an explosive gas such as hydrogen can be used for high efficiency soldering.
It has now been found that if one provides an enclosed zone wherein there are two fluid barrier curtains at the entry and the exit, one is able to provide the fluid barrier curtains with an inert gas to contain the gas environment within the enclosed zone. Then one can supply a reducing gas which may be an explosive gas such as hydrogen to the enclosed zone and burn off any excess reducing gas at the fluid barrier curtain. This permits a far higher concentration of hydrogen within the enclosed zone, resulting in a greater reducing action for treatment such as soldering.
Furthermore, by providing a hydrogen ga~ generator to feed the enclosed zone, one does not have to store hydrogen, and , . .:
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the supply can be cut off almost instantaneowsly by turning off the generator.
The present invention provides a process for treating an element with a reducing gas, comprising the steps of conveying the element through an entry into an enclosed zone, the entry containing at least one fluid barrier curtain wherein the fluid is an inert gas, filling the enclosed zone with the reducing gas; heating the element in the zone;
conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas at the entry and exit fluid barrier curtains.
The present invention also provides an apparatus for treating an element with a reducing gas comprising an lS enclosed zone having an entry and an exit; a conveyor means adapted to convey an element in a conveyor path through the enclosed zone from the entry to the exit; at least one entry fluid barrier curtain in the entry, having a burn-off for combustible gas above the curtain; heating means to heat the enclosed zone; at least one exit fluid barrier curtain in the exit, having a burn-off for combustible gas above the curtain; inert gas supply for the entry fluid barrier curtain and the exit fluid barrier curtain, and reducing gas supply `::
for feeding into the enclosed zone. In a further embodiment, the reducing gas supply is a hydrogen generator with no gas :-storage and with a substantially instantaneous gas cut off. ~ ;;
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In drawings which illustrate embodiments of the present invention, Figure 1 is a schematic side view illustrating one ~ -embodiment of an enclosed zone for treating an element with a reducing gas.
Figure 2 is a schematic side view illustrating another embodiment of an enclosed zone for wave soldering.
Figure 3 is a schematic side view illustrating a further embodiment of an enclosed zone for wave soldering.
Figure 1 illustrates an enclosure 10 which has an entry 12 and an exit 14. A conveyor path 16 extends from the entry 12 to the exit 14 passing through the enclosed zone 10 suitable for conveylng elements into and out of the zone 10.
The elements, which are circuit boards or other similar types ~ .
~lS of~wirlng boards and the like, are heated and treated, for example soldered within the zone 10. In another embodiment the elements may be those that require curing, drying or otherwise processed in a gas atmosphere.
Two fluid barrier curtains are provided at both the entry 12 and the exit 14. The fluid barrier curtains are preferably tho~e of the type disclosed in U.S. patent 4,696,226. The first entry fluid barrier curtain 18 and the . ., :
201~,7~ ~
, second entry fluid barrier curtain 20 are both supplied with an inert gas, preferably nitrogen, to provide a barrier for sealing the enclosed zone 10. Above the first and second entry curtains 18 and 20 are burn off exits each with a burn off device 22, such as an electrical element, for burning off hydrogen or other combustible reducing gas that exits from the curtains 18 and 20. First and second exit fluid barrier curtains 24 and 28 are provided with an inert gas such as nitrogen so that the reducing gas can not escape out of the enclosed zone 10. Burn off exits above the first and second exit curtains 24 and 28, each have a burn off device 26, such as an electrical element, to ensure all combustible gas is burnt off. Whereas an electrical element 26 is illustrated herein, a pilot light may be provided, gas or oil operated, for the burn off devices 22 and 26.
Because inert gas curtains are provided on both the entry and exit to the enclosed zone 10, hydrogen, which may be premixed up to the highest concentrations obtainable may be supplied to the zone through entry ports 30 within the enclo~ure. Any excess hydrogen from within the enclosure exits through the curtains 18, 20, 24 and 28, and is burnt off by the burn off devices 22 and 26. Thus no combustible gas escapes into the atmosphere.
A hydrogen generator 32 is preferably provided for supplying hydrogen to the enclosed zone 10. The hydrogen generator is preferably a mul'iple cell electxolysis - 20167~
generator for producing both hydrogen and oxygen in a perfect 2 to 1 ratio from water. One example of such a generator is sold by SPIRIG of Switzerland under the trade mark SPIRFLAME.
The generator uses a modest amount of electric energy and different capacities of generator are provided for different uses. The hydrogen generator has the advantage of not storing any hydrogen whatsoever, and being able to easily control the quantity of hydrogen made available to the enclosed zone 10. By turning off the generator, in other words stopping the electrical power to the generator, the hydrogen flow immediately stops. No hydrogen remains in the generator so there is no hazardous condition. The gas remaining in the enclosure 10 is burnt off by the burn off devices 22 and 26.
In another embodiment a mixture of gases, one of which is a reducing gas, may be prepared in a desired concentration for filling the enclosed zone 10. The ratio of hydrogen and inert gas such as nitrogen, ozone, argon and the like may be premixed to the desired concentration. A generator for nitrogen may be supplied, or alternatively, nitrogen may be supplied from bottles.
A heater 34 is illustrated to heat the hydrogen from the hydrogen generator 30, or hydrogen mixture feeding both the entry ports 30 to the enclosed zone 30. A control valve 36 i~ shown for controlling hydrogen flow. In one embodiment another gas may be premixed with hydrogen, prior to entering : . .
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the enclosed zone 30. A mixer and valving system is not illustrated, but would be apparent to one skilled in the art.
The nitrogen supply 40 feeds the entry and exit fluid barrier curtains 18 and 28. In one embodiment, a nitrogen heater 41 heats the nitrogen to the two entry curtains 18 and 20. The heated nitrogen assists in heating elements entering the enclosure 10. Other heaters 42 positioned below the conveyor path 16 and in some configurations above and below the conveyor path 16 in the enclosed zone 10 also assist in heating the elements. By providing a plurality of heaters 42 a heating profile can be applied to the elements to suit the required treatment conditions, such as soldering, curing, drying and the like.
A single linear conveyor may be provided to convey elements along the conveyor path 16 or more than one conveyor `~ ;
can do the same function. The conveyor may support elements on a series of fingers from one or more side chains, or in another embodiment, the elements are supported on pallets or -on an adjustable width conveyor. A flat mesh conveyor not affected by temperature may also be used.
Soldering may occur in a number of ways. In one embodiment reflow soldering occurs, wherein a solder paste or preplated contacts are preheated and solder melts and flows to form the solder joint. In one embodiment the solder cools prior to the element coming in contact with the air so that g . :~. ~: . : :
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oxidizing of the liquid solder surface is minimized or eliminated.
In another embodiment as illustrated in Figure 2 a solder wave 50 is located in the enclosed zone 10. The S solder wave 50 is positioned above a solder pot 52 and has a vibrator 54 to provide a vibration to the solder wave. One embodiment of a vibratory wave soldering is shown in U.S.
patent 4,684,065. The solder wave 50 projects upwards so that elements passing in the conveyor path 16 contacts the solder wave. In the embodiment shown in Figure 2, the second entry curtain 20 and first exit curtain 24 are fed with hydrogen or a mixture of hydrogen with nitrogen rather than nitrogen alone. The hydrogen or the mixture of hydrogen and nitrogen is not heated in the embodiment shown, although if a heat profile is desired for the elements, then hydrogen or hydrogen mixture is fed to the second entry curtain 20 may be `-heated.
Figure 3 shows a further embodiment wherein only one entry fluid barrier curtain 18 and one exit fluid barrier 20 curtain 28 are provided. Both curtains are fed from a nitrogen supply 40 and have burn off devices 22 and 26 in the form of electrical elements at burn off exits. There is provided a solder wave 50 positioned above a solder pot 52, but no vibrator is shown.
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In one embodiment the nitrogen supply to the second exit curtain 28 is cool or is cooled so that the elements leaving the enclosure 10 are cooled and the solder solidified when the element passes the second exit curtain 28.
Whereas heaters 42 are shown in both Figures 1, 2 and 3, they are not always needed, and may be omitted. The heat is then provided by heating the gas before entering the enclosure.
Variouæ changes may be made to the embodiment shown herein without departing from the scope of the present invention which is limited only by the following claims.
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ENVIRONMENT INCLUDING A GAS GENERATOR
The present invention relates to treating an element with a reducing gas soldering, and more specifically, to soldering in the presence of a reducing gas in an enclosed zone.
Soldering of printed wiring boards and other similar types of elements, without the application of flux, has a number of advantages including avoiding the step of applying : flux prior to soldering and eliminating the necessity of cleanlng the flux deposits from the solder joints after soldering. Fluxless soldering may be carried out in an inert ~15 gas atmosphere generally with a reducing agent or other : solder additions which may perform the same function as flux, that is to prevent oxidation of the solder, and provide clean solder connections. In the case of solder bath, or solder wave type of soldering, the absence of flux reduces flux deposits in the solder and when liquid solder is maintained in an inert atmosphere, there is a reduction of solder oxides known as dross that form on the solder surface.
Co-pending application filed concurrently herewith, 20~6~8 entitled Shield Ga~ Wave Soldering, Serial No.
discloses soldering in a shield gas atmosphere.
In one embodiment, soldering is achieved by conveying an element so that it is contacted by a solder wave. In another embodiment, reflow soldering is used wherein solder paste or solder plating is first applied to the metallic components to be soldered and the element is then heated so that the solder melts to liquid solder which flows to form the solder joint. -Most solder paste used for reflow soldering includes flux.
However, if reflow soldering occurs in an inert atmosphere with or without a reducing agent, then reduction of the quantity of flux or modification of the chemical nature of the flux in the solder paste can be achieved.
Co-pending application concurrently filed herewith entitled Tunnel for Fluxless Soldering, Serial No.
discloses soldering of elements, such as printed wiring boards, in a non-explosive gas atmosphere which substantially excludes oxygen.
Soldering in an enclosed zone is also disclosed in co-pending application filed concurrently herewith, entitled GasCurtain Additives Zoned Tunnel for Soldering. In this application an apparatus is disclosed for soldering an element in an enclosed zone containing a gas atmosphere. The enclosed zone has an entry and an exit and at least one fluid barrier curtain at the entry and at least one fluid barrier ~ ` , .
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curtain at the exit. The conveyor conveys an element through the fluid barrier, and in one embodiment an additive aid soldering is added to the fluid in the curtain at the entry.
In another embodiment a plurality of zones are supplied in line with a conveyor to convey elementæ through the zones.
Fluid barrier curtains are provided between the zones.
It is known to conduct wave soldering in a reducing gas atmosphere, and Bertiger in U.S. patent 4,538,757 discloses wave soldering in an enclosure containing nitrogen and hydrogen. Oxygen is excluded from the enclosure to avoid an initial fluxing step. It is disclosed in this patent that a high proportion of nitrogen in the mixture reduces the risk of an explosive mixture.
Hydrogen is often used for high temperature brazing processes and the like, and although some may consider it is not beneficial for normal soldering temperatures, i.e. 300 -400-C, the literature indicates that it is a preferred reducing gas for soldering copper circuit boards. However, it is known that hydrogen is an explosive gas and therefore the use of hydrogen in an explosive mixture presents certain hazards.
It is an aim of the present invention to treat elements in an enclosed zone with a reducing gas. The treatment may be soldering, curing, drying or other type of treatment requiring the presence of a reducing gas.
20167~ 8 It is another aim of the present invention to provide a safe soldering apparatus that utilizes an explosive gas such as hydrogen. This is achieved by combining an enclosure with gas curtains at the entry and exit, a gas generator that `;
produces only the quantity of gas necessary for the enclosure, there being no shortage of gas necessary and there being substantially instant cut off of gas supply. This avoids the necessity of storage containers of hydrogen, which even if located far from the apparatus have feed lines that risk being damaged, or can leak. Furthermore, burn-off of excess gas occurs at the gas curtains at both the entry and the exit. Thus a safe soldering apparatus where a high percentage of an explosive gas such as hydrogen can be used for high efficiency soldering.
It has now been found that if one provides an enclosed zone wherein there are two fluid barrier curtains at the entry and the exit, one is able to provide the fluid barrier curtains with an inert gas to contain the gas environment within the enclosed zone. Then one can supply a reducing gas which may be an explosive gas such as hydrogen to the enclosed zone and burn off any excess reducing gas at the fluid barrier curtain. This permits a far higher concentration of hydrogen within the enclosed zone, resulting in a greater reducing action for treatment such as soldering.
Furthermore, by providing a hydrogen ga~ generator to feed the enclosed zone, one does not have to store hydrogen, and , . .:
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the supply can be cut off almost instantaneowsly by turning off the generator.
The present invention provides a process for treating an element with a reducing gas, comprising the steps of conveying the element through an entry into an enclosed zone, the entry containing at least one fluid barrier curtain wherein the fluid is an inert gas, filling the enclosed zone with the reducing gas; heating the element in the zone;
conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas at the entry and exit fluid barrier curtains.
The present invention also provides an apparatus for treating an element with a reducing gas comprising an lS enclosed zone having an entry and an exit; a conveyor means adapted to convey an element in a conveyor path through the enclosed zone from the entry to the exit; at least one entry fluid barrier curtain in the entry, having a burn-off for combustible gas above the curtain; heating means to heat the enclosed zone; at least one exit fluid barrier curtain in the exit, having a burn-off for combustible gas above the curtain; inert gas supply for the entry fluid barrier curtain and the exit fluid barrier curtain, and reducing gas supply `::
for feeding into the enclosed zone. In a further embodiment, the reducing gas supply is a hydrogen generator with no gas :-storage and with a substantially instantaneous gas cut off. ~ ;;
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In drawings which illustrate embodiments of the present invention, Figure 1 is a schematic side view illustrating one ~ -embodiment of an enclosed zone for treating an element with a reducing gas.
Figure 2 is a schematic side view illustrating another embodiment of an enclosed zone for wave soldering.
Figure 3 is a schematic side view illustrating a further embodiment of an enclosed zone for wave soldering.
Figure 1 illustrates an enclosure 10 which has an entry 12 and an exit 14. A conveyor path 16 extends from the entry 12 to the exit 14 passing through the enclosed zone 10 suitable for conveylng elements into and out of the zone 10.
The elements, which are circuit boards or other similar types ~ .
~lS of~wirlng boards and the like, are heated and treated, for example soldered within the zone 10. In another embodiment the elements may be those that require curing, drying or otherwise processed in a gas atmosphere.
Two fluid barrier curtains are provided at both the entry 12 and the exit 14. The fluid barrier curtains are preferably tho~e of the type disclosed in U.S. patent 4,696,226. The first entry fluid barrier curtain 18 and the . ., :
201~,7~ ~
, second entry fluid barrier curtain 20 are both supplied with an inert gas, preferably nitrogen, to provide a barrier for sealing the enclosed zone 10. Above the first and second entry curtains 18 and 20 are burn off exits each with a burn off device 22, such as an electrical element, for burning off hydrogen or other combustible reducing gas that exits from the curtains 18 and 20. First and second exit fluid barrier curtains 24 and 28 are provided with an inert gas such as nitrogen so that the reducing gas can not escape out of the enclosed zone 10. Burn off exits above the first and second exit curtains 24 and 28, each have a burn off device 26, such as an electrical element, to ensure all combustible gas is burnt off. Whereas an electrical element 26 is illustrated herein, a pilot light may be provided, gas or oil operated, for the burn off devices 22 and 26.
Because inert gas curtains are provided on both the entry and exit to the enclosed zone 10, hydrogen, which may be premixed up to the highest concentrations obtainable may be supplied to the zone through entry ports 30 within the enclo~ure. Any excess hydrogen from within the enclosure exits through the curtains 18, 20, 24 and 28, and is burnt off by the burn off devices 22 and 26. Thus no combustible gas escapes into the atmosphere.
A hydrogen generator 32 is preferably provided for supplying hydrogen to the enclosed zone 10. The hydrogen generator is preferably a mul'iple cell electxolysis - 20167~
generator for producing both hydrogen and oxygen in a perfect 2 to 1 ratio from water. One example of such a generator is sold by SPIRIG of Switzerland under the trade mark SPIRFLAME.
The generator uses a modest amount of electric energy and different capacities of generator are provided for different uses. The hydrogen generator has the advantage of not storing any hydrogen whatsoever, and being able to easily control the quantity of hydrogen made available to the enclosed zone 10. By turning off the generator, in other words stopping the electrical power to the generator, the hydrogen flow immediately stops. No hydrogen remains in the generator so there is no hazardous condition. The gas remaining in the enclosure 10 is burnt off by the burn off devices 22 and 26.
In another embodiment a mixture of gases, one of which is a reducing gas, may be prepared in a desired concentration for filling the enclosed zone 10. The ratio of hydrogen and inert gas such as nitrogen, ozone, argon and the like may be premixed to the desired concentration. A generator for nitrogen may be supplied, or alternatively, nitrogen may be supplied from bottles.
A heater 34 is illustrated to heat the hydrogen from the hydrogen generator 30, or hydrogen mixture feeding both the entry ports 30 to the enclosed zone 30. A control valve 36 i~ shown for controlling hydrogen flow. In one embodiment another gas may be premixed with hydrogen, prior to entering : . .
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the enclosed zone 30. A mixer and valving system is not illustrated, but would be apparent to one skilled in the art.
The nitrogen supply 40 feeds the entry and exit fluid barrier curtains 18 and 28. In one embodiment, a nitrogen heater 41 heats the nitrogen to the two entry curtains 18 and 20. The heated nitrogen assists in heating elements entering the enclosure 10. Other heaters 42 positioned below the conveyor path 16 and in some configurations above and below the conveyor path 16 in the enclosed zone 10 also assist in heating the elements. By providing a plurality of heaters 42 a heating profile can be applied to the elements to suit the required treatment conditions, such as soldering, curing, drying and the like.
A single linear conveyor may be provided to convey elements along the conveyor path 16 or more than one conveyor `~ ;
can do the same function. The conveyor may support elements on a series of fingers from one or more side chains, or in another embodiment, the elements are supported on pallets or -on an adjustable width conveyor. A flat mesh conveyor not affected by temperature may also be used.
Soldering may occur in a number of ways. In one embodiment reflow soldering occurs, wherein a solder paste or preplated contacts are preheated and solder melts and flows to form the solder joint. In one embodiment the solder cools prior to the element coming in contact with the air so that g . :~. ~: . : :
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oxidizing of the liquid solder surface is minimized or eliminated.
In another embodiment as illustrated in Figure 2 a solder wave 50 is located in the enclosed zone 10. The S solder wave 50 is positioned above a solder pot 52 and has a vibrator 54 to provide a vibration to the solder wave. One embodiment of a vibratory wave soldering is shown in U.S.
patent 4,684,065. The solder wave 50 projects upwards so that elements passing in the conveyor path 16 contacts the solder wave. In the embodiment shown in Figure 2, the second entry curtain 20 and first exit curtain 24 are fed with hydrogen or a mixture of hydrogen with nitrogen rather than nitrogen alone. The hydrogen or the mixture of hydrogen and nitrogen is not heated in the embodiment shown, although if a heat profile is desired for the elements, then hydrogen or hydrogen mixture is fed to the second entry curtain 20 may be `-heated.
Figure 3 shows a further embodiment wherein only one entry fluid barrier curtain 18 and one exit fluid barrier 20 curtain 28 are provided. Both curtains are fed from a nitrogen supply 40 and have burn off devices 22 and 26 in the form of electrical elements at burn off exits. There is provided a solder wave 50 positioned above a solder pot 52, but no vibrator is shown.
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In one embodiment the nitrogen supply to the second exit curtain 28 is cool or is cooled so that the elements leaving the enclosure 10 are cooled and the solder solidified when the element passes the second exit curtain 28.
Whereas heaters 42 are shown in both Figures 1, 2 and 3, they are not always needed, and may be omitted. The heat is then provided by heating the gas before entering the enclosure.
Variouæ changes may be made to the embodiment shown herein without departing from the scope of the present invention which is limited only by the following claims.
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Claims (20)
1. A process for treating an element with a reducing gas comprising the steps of conveying the element through an entry into an enclosed zone, the entry containing at least one entry fluid barrier curtain wherein the fluid is an inert gas;
filling the enclosed zone with the reducing gas;
heating the element in the zone;
conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas above the entry and exit fluid barrier curtains.
filling the enclosed zone with the reducing gas;
heating the element in the zone;
conveying the element from the enclosed zone through an exit containing at least one exit fluid barrier curtain, wherein the fluid is an inert gas, and burning off excess reducing gas above the entry and exit fluid barrier curtains.
2. The process for treating according to Claim 1 wherein the treating is soldering.
3. The process for treating according to Claim 2 wherein the inert gas is nitrogen.
4. The process for treating according to Claim 2 wherein the reducing gas is selected from the group of hydrogen and a mixture of hydrogen with at least another gas.
5. The process for treating according to Claim 4 wherein a hydrogen generator is supplied having no gas storage and with a substantially instantaneous gas cut off.
6. The process for treating according to Claim 4 wherein the hydrogen is preheated.
7. The process for treating according to Claim 1 wherein the entry contains at least two entry fluid barrier curtains, and the exit contains at least two exit fluid barrier curtains, and the fluid for all the curtains is inert gas.
8. The process for treating according to Claim 2 wherein the entry contains at least two entry fluid curtains, a first entry fluid barrier curtain wherein the first fluid is an inert gas, followed by a second entry fluid barrier curtain, wherein the second fluid is a reducing gas, and the exit contains at least two exit fluid curtains, a first exit fluid barrier curtain, wherein the first fluid is a reducing gas, followed by a second exit fluid barrier curtain, wherein the second fluid is an inert gas.
9. The process for treating according to Claim 8 wherein the reducing gas is selected from the group, consisting of hydrogen and a mixture of hydrogen with at least another gas.
10. The process for treating according to Claim 3 wherein the inert gas fed to the exit fluid barrier curtain is cooled.
11. The process for treating according to Claim 1 wherein heaters are provided to heat the elements passing through the enclosed zone.
12. The process for treating according to Claim 2 wherein the treating is wave soldering.
13. The process for treating according to Claim 2 wherein the treating is reflow soldering.
14. An apparatus for treating an element with a reducing gas comprising an enclosed zone having an entry and an exit;
a conveyor means adapted to convey an element in a conveyor path through the enclosed zone from the entry to the exit;
at least one entry fluid barrier curtain in the entry, having a burn off for combustible gas above the curtain;
heating means to heat the enclosed zone;
at least one exit fluid barrier curtain in the exit, having a burn off for combustible gas above the curtain;
inert gas supply for the entry fluid barrier curtain and the exit fluid barrier curtain and reducing gas supply for feeding into the enclosed zone.
a conveyor means adapted to convey an element in a conveyor path through the enclosed zone from the entry to the exit;
at least one entry fluid barrier curtain in the entry, having a burn off for combustible gas above the curtain;
heating means to heat the enclosed zone;
at least one exit fluid barrier curtain in the exit, having a burn off for combustible gas above the curtain;
inert gas supply for the entry fluid barrier curtain and the exit fluid barrier curtain and reducing gas supply for feeding into the enclosed zone.
15. The apparatus for treating according to Claim 14 wherein the reducing gas supply is a hydrogen generator with no gas storage and with a substantially instantaneous gas cut off.
16. The apparatus for treating according to Claim 14 including at least two entry fluid barrier curtains, and at least two exit fluid barrier curtains, all the curtains having burn-offs for combustible gas.
17. The apparatus for treating according to Claim 14 including a first entry fluid barrier curtain in the entry with an inert gas supply, followed by a second entry fluid barrier curtain with a reducing gas supply, and a first exit fluid barrier curtain in the exit, with a reducing gas supply, followed by a second exit fluid barrier curtain with an inert gas supply, all the curtains having burn-offs for combustible gas.
18. The apparatus for treating according to Claim 14 including a heater for the reducing gas.
19. The apparatus for treating according to Claim 14 including heaters for heating elements conveyed on the conveyor path in the enclosed zone.
20. The apparatus for treating according to Claim 14 including wave soldering means within the enclosed zone.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2016718 CA2016718A1 (en) | 1990-05-14 | 1990-05-14 | Tunnel for treating an element in a gas environment including a gas generator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2016718 CA2016718A1 (en) | 1990-05-14 | 1990-05-14 | Tunnel for treating an element in a gas environment including a gas generator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2016718A1 true CA2016718A1 (en) | 1991-11-14 |
Family
ID=4144979
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2016718 Abandoned CA2016718A1 (en) | 1990-05-14 | 1990-05-14 | Tunnel for treating an element in a gas environment including a gas generator |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2016718A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0640424A1 (en) * | 1993-08-19 | 1995-03-01 | Rockwell International Corporation | Hydrogen assisted reduced oxide soldering system |
-
1990
- 1990-05-14 CA CA 2016718 patent/CA2016718A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0640424A1 (en) * | 1993-08-19 | 1995-03-01 | Rockwell International Corporation | Hydrogen assisted reduced oxide soldering system |
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