CA1254112A - Soldering device, flux and method - Google Patents
Soldering device, flux and methodInfo
- Publication number
- CA1254112A CA1254112A CA000560043A CA560043A CA1254112A CA 1254112 A CA1254112 A CA 1254112A CA 000560043 A CA000560043 A CA 000560043A CA 560043 A CA560043 A CA 560043A CA 1254112 A CA1254112 A CA 1254112A
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- flux
- solder
- temperature
- heat
- accordance
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a flux composition which comprises solder flux and a chemically reactive component, said flux composition undergoing a chemical reaction resulting in a visible color change at a critical temperature.
The present invention provides a flux composition which comprises solder flux and a chemically reactive component, said flux composition undergoing a chemical reaction resulting in a visible color change at a critical temperature.
Description
Thls Inventlon relates to a heat-recoverable solderlng devlce, to methods of solderlng uslng such a devlce, to tempera-tUre Indlcatlng solder flux composltlons and to the use of such composltlons In solderlng.
Thls appllcatlon Is a dlvlslonal appllcatlon of copend-lng appl/catlon No. 412,782 flled October 4, 1982.
Heat-recoverable solderlng devlces are known In the art. See, for example, U.S. Patents Nos. 3,316,125 to Sherlock, 3,305,625 to Ellls, 3,316,343 to Sherlock, 3,396,460 to Wetmore and 3,396,894 to Ellls. Such heat-recoverable devlces generally comprlse a heat shrlnkable polymerlc sleeve havlng a fuslble Insert comprlslng solder. Elongate substrates, such as a palr of wlres, are Inserted Into the sleeve and heat Is applled causlng the sleeve to shrlnk Into contact wlth the substrates. The heat also causes the solder to melt and flow around the substrates.
Upon coollng, a solld solder Jolnt Is formed between the sub-strates. In general, the temperature requlred to melt the solder Is hlgher than the temperature requlred to shrlnk the sleeve.
! Thus, vlsual observatlon that the sleeve has completely recovered does not necessarlly mean that the temperature necessary for sol-derlng has been reached. There Is, therefore, no vlslble Indlca-tlon durlng the solderlng process that enough heat has been applled. Further, In the event that a soldered Jolnt so formed falls durlng use, there Is no way of subsequently Inspectlng the Jolnt to determlne whether the fallure was due to Inadequate heatlng durlng the solderlng process.
;
Copendlng appllcatlon No. 412,782 descrlbes and clalms a solderlng devlce comprlslng a substantlally transparent heat-recoverable polymerlc member, a fuslble solder Insert posltloned wlthln sald member and a solder flux composltlon whlch Is assocl-ated wlth sald solder Insert and whlch undergoes a vlslble colour change at a crltlcal temperature.
l~S'~
The polymerlc member Is substantlally transparent to the extent that the vlslble colour change of the solder f/ux can be seen through the member. Thls devlce thus advantageously pro-vldes a c/ear vlslble Indlcatlon that a so/der ~olnt or connec-t/on has reached the correct solderlng temperature.
The copendlng applIcatlon also dlscloses and clalms a method of solderlng at least two solderable substrates wh/ch com-prlses posltlonlng sald substrates wlthln a heat-recoverab/e sol-derlng devlce accordlng to the flrst aspect of the present Inven-tlon, and heatlng sald devlce, thereby causlng sald heat-recover-able member to recover Into contact wlth sald substrates and sald flux to undergo a vlslble colour change. Preferably the devlce Is arranged such that the heatIng step causes the heat-recover-able member to recover /nto contact wlth the substrates beforethe f/ux undergoes a vlslble co/our change. Preferably the sub-strates are genera/ly e/ongate.
The present Inventlon provldes a solder f/ux compos/-tlon whlch comprlses solder flux and a react/ve component, thef/ux composltlon undergolng a chemlcal react/on resultlng In a vlslble colour change at a crltlcal temperature.
The Inventlon also provldes a method of solderlng at least two solderable substrates located !
adjacent each other, which comprises applying to said subs,rates a quantity of solder and a flux composition according to said third aspect of the present invention, and applying heat to said substrates, solder and fl~x composition 5 until a visible colour change in said 1ux composition occurs.
The heat-recoverable member of the device of the present invention is capable of undergoing a change in its dimensional configuration on application of heat. This 10 change in dimensional config~lration is usually toward an original shape from which it has previously been deformed, but the term "heat-recoverable", as used herein, also includes a member which, on heating, adopts a new configuration even if it has not been previously deformed.
. ' ' lS The heat-recoverable member of the device according to said first aspect of the present invention generally ., . ,.. ,j comprises a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in 1~.5. Patents Nos.
20 2,027,962, 3,086,242 and 3,957,372. The original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, while hot, to a dimensionally heat-unstable form but, in other methods of preparation, a preformed dimensionally 25 heat-stable article is deformed to a dimensionally heat-unstable form in a separate stage.
In the production of the heat-recoverable member, the polymeric material is generally crcss-linked.
One manner of producing a heat-recoverable article comprises 30 shaping the polymeric material into the desired heat-stable form, s~bsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point, or for amorphous materials the sotening point, of the polymer, deforming the article and cooling 35 the article while~ in the deformed state so that the 1~25'~112 -4- ~P0783 deformed state of the article is retained. In use, applica-tion of heat will cause the article to dimensionally recover from the deformed state to the original heat-stable shape.
.
In other articles, as described, for example, in U.S. Patent No. 4,207,364, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating weakens and thus allows the elastomeric member to recover.
Examples of polymers used in the manufacture of heat-recoverable articles include polyolefins, e.g.
polyethylene and copolymers of ethylene with ethylenically unsaturated monomers, such as ethylene/ethyl acrylate, ethylene/vinyl acetate copolymers, polyvinyl chloride, ; 15 elastomers, silicones, polytetraflucroethylene, polyvinyl--. ... ;j"; .. ,~
i idene fluoride, polyurethanes, and ionomers. The polymer can be cross-linked either by radiation or chemical means.
The heat-recovery temperature of crystalline polymers is generally a temperature slightly above the crystalline melting temperature. Polymers, such as polyvinyl chloride, which are not crystalline recover at about their glass transition temperature.
The wall thickness of the member is preferably in the range of from about 0.0005 inch (0.0127mm) to about 0.05 inch (1.2700mm) and is especially preferably from about 0.0008 inch (0.0203mm) to about 0.01 inch(0.2540mm).
The solder insert may be positioned within the heat-recoverable member by coating solder onto the surface of the recoverable member. Alternatively, a solder preform of the desired configuration may be produced and this then lZ54112 inserted into the heat-recoverable member. The solder is positioned such that when two solderable substrates are positioned within the device and the device is heated, the solder is forced into intimate contact with the substrates by the recovery of the heat-recoverable member. When the heat-recoverable member is in the form of a heat-shrinkable sleeve, the solder is preferably in the shape of a ring on the inner surface of the sleeve.
The flux aids the flow of the solder or cleans the surfaces of the substrates to be joined or both. various solder flux compositions are known and are commercially available.
Widely used as solder fluxes are compositions based on natural rosln. Other fluxes include, for example, inorganic and organic acids. In use, the solder flux melts, flows and covers the substrate surface at a temperature below the melting point of the solder. Thus the particular flux used will depend of the nature of the solder in a given application. Any solder flux can be used in accordance with this invention. The flux comprises a temperature indicating component and the particular flux and the appropriate temperature indicating component to be used in a particular application can be readily ascertained by one skilled in the art without undue experimentation. The temperature lndicatlng component ls preferably one that is compatible with the flux and does not interfere wlth the normal functioning of the flux.
The solder flux is associated with the solder of the heat-recoverable soldering device. Any of the conventional means for associating flux with solder can be used. For example, a solder preform can be coated with flux by spraying, dipping, brushing or the like, usually before it has been positioned within the heat-recoverable device. The solder flux can also be used ln soldering operations such as hand soldering, in which a heat-recoverable device is not employed. In this event, the flux can be coated on - .
,; ~
1~ 2 the solder or can be positioned within the solder, fo~
example, in the form of a core which can be in various configurations as is well known in the art. The flux must be visible during the soldering process to detect the colour change in the flux when it reaches the appropriate temperature. It has been found that if the flux is positioned as a core within the solder, flow of the flux on heating renders it visible. A visible colour change occurs when the soldering temperature has been reached. In general, the soldering temperature is higher than the recovery temperature.
Thus continued heating is required after recovery in order to effect the visible colour change of the solder flux.
In accordance with this invention, the solder fluY composition contains a temperature indicator such ~ 15 that the f1ux undergoes a colour change when heated to the - ~ appropriate soldering temperature. The colour change is -~¦ preferably an irreversible colour change, that is a colour change that does not reverse, for example, when the solder and flux cool and solidify. Such an irreversible change provides a continuing indication and permanent means for determining whether the soldered joint was heated to the required temperature during soldering. Thus improperly formed terminations can be detected by visual inspection after the soldered connection is completed and cooled.
The colour change of the flux is preferably from a coloured state to a substantially colourless one. The completed solder joint is thus visible for inspection through the flux. In this way, the joint itself can be inspected to check for adequate soldering and to detect improperly formed terminations, as well as to check for application of suficient heat during the soldering process by the change in colour of the fl~x.
The flux composition changes colour at a critical ~254112 temperature. The desired critical temperature varies depending on the particular solder used. The critical temperature is that temperature which is required to effect a solder connection with the particular solder, that is the temperature required to cause the solder to melt, flow and wet the substrates so that on cooling the solder makes a mechanical and electrical bond between the substrates being soldered. The particular solder to be used varies depending on the substrates being joined and the material of the heat-recoverable member. The temperature required to effect the solder termination is generally above the temperature re~uired to cause recovery of the heat-recoverable member.
Since the critical temperature varies with the nature of the solder, the temperature indicating component of the flux composition varies depending on the solder used. Preferably, the flux composition undergoes a colour change in the temperature range of from about 150C to about 450C, especially preferably from about 200C to about 240C. The temperature of the colour change is preferably in the range of from about 20C to about 60C above the melting point of the solder. Preferably, it is about 20C to about 30C above the melting point of a low temperature solder and about 30C to about 60C above the melting point of a high temperature solder.
As stated above, the flux composition contains a temperature indicator such that at a critical temperature the flux composition undergoes a colour change. Various temperature indicators can be used, for example, azo dyes such as Pigment Red 73 (an azo dye prepared from 2-nitro-p-toludidine and 2-naphthol, CI 12120), acid-base indicators such as Thymol blue, diazo dyes such as Acid Red 73 (a diazo dye derived from p-phenylazoaniline and 2-naphthol-6,8-disulfonic acid, CI 27290), and the like. In general, any dye which is compatible with the flux and which undergoes a colour change at a critical temperature can be used.
, .
12SC~1 ~2 Preferably the flux composition contains a temperature indicator that is a chemically reactive component which undergoes a chemical reaction with the solder flux at a critical tempera-ture to produce a colour change. Partlcularly preferred are flux compositions in which, at a critical temperature, the reactive component causes the flux composition to become colourless since this allows the soldered ~oint to be readily inspected. Suitable chemically reactive components are, for example, Bromocresol Green, Basic Fuchsine or Thymol Blue.
The temperature indicator may be incorporated into a solder flux composition by known techniques. The amount of tem-perature indicator incorporated into the flux is preferably in the range of from about 0.01 to about 5 parts per 100 parts of flux and is especially preferably from about 0.05 to about 2 parts per 100 parts of flux. The amount added depends on the intensity of the colour. Sufficient temperature indicator should be added to provide a flux composition which is clearly visible during the soldering operation. The flux composition may also contain additives, for example, dispersing aids such as water, alcohol or a subfactant or emulsifier, buffers, such as an acid or salt to maintain the desired pH, for example, oxalic acid, lactic acid, maleic acid, tartaric acid, fumaric acid or citric acid, and stabilizers.
An embodiment of a device in accordance with the present invention will now be described by way of example, with reference to the accompanying drawings, wherein:-Figure 1 is a side view of a heat-recoverable device according to the present invention having two elongate substrates positioned therein;
Figure 2 is a side view of the device of Figure 1 after a solder ~oint has been effected between the elongate substrates.
12~i;411~
.
ln Figure l, a heat-recoverable device comprises a heat-recoverable member in the form of a tubular sleeve 3 having a solder insert 4. The sleeve 3 is a heat-shrinkable tube of radiation cross-linked ethylene-tetrafluo~oethylene copolymer containing fusible thermoplastic inserts 5 toward each end of the tube. Prior to being positioned within the sleeve 3 the solder insert 4 is coated with a temperature indicating flux. The coated flux is dark blue in colour and thus obscures the grey colour of the solder insert.
The unrecovered sleeve 3 is positioned over a coaxial cable l having a portion of the outer insulation removed to expose the underlying shield. The end region of a ground wire 2 with the insulation being removed ; from the end region lies adjacent the exposed shield of the 1 . 15 cable 1. The sleeve 3 is then heated causing it to shrink ; ~i into contact with the cable and ground wire and to cause the . solder to melt and flow. On heating, the flux changes colour at a temperature above the melting point of the solder becoming colourless. Heating is discontinued at this point. During heating of the sleeve, the thermoplastic inserts 5 melt and seal the sleeve to the cable. The resulting product is shown in Figure 2.
In Figure 2, sleeve 3 has shrunk into contact with and is sealed to the cable 1. As the flux is now colourless, the grey colour of the solder, 4, is visible through the sleeve. The solder has thus affected a termination between the shield of l and the exposed tip of ground wire, 2.
The following Examples illustrate various solder flux compositions in accordance with the present invention.
Temperature indicating solder flux compositions 125411.~
.
-10- ~P0783 were prepared by dispersing various dyes in a Milros #611, a commercially available rosin-based flux comprising 37 of a mixture of rosin isomers in 63% isopropyl alcohol.
The dyes used and the concentrations of dye in the result-ing temperature indicating flux compositions are listed in Table 1. Additives, as listed in Table 1, were added as appropriate to aid in dissolution of the pigment or to buffer the solution to maintain the desired p~. The dyes used are:
Acid Red 73 (commercially available as Scarlet M
Crude), a diazo dye derived from p-phenylazoaniline and 2-naphthol-6,8-disulphonic acid. (Colour Index, CI, 27290).
Pigment Red 3 (commercially available as Atlasol ' 15 Spirit Red-3) an azo dye prepared from 2-nitro-p-;, toluidine and 2-naphthol. (CI 12120).
''''. ,-~i : ~ Thymol Blue, commercially available and also referred to as thymolsulphonphthalien.
Pigment Red 52 (commercially available as Garnet Toner ~2), an azo dye derived from 2-amino-5-chloro-p-toluenesulphonic acid and 3-hydroxy-2-naphthoic acid.
(CI 15860).
Bromocresol Green, also known as 3',3'',5',5''-tetrabromo-m-cresolsulphonphthalein.
Solvent Red 24, (commercially available as Atlasol Red 4B) an azo dye derived from 4-0-tolylazo-o-toluidine and 2-naphthol. (CI 26105).
Pigment Yellow 5 (also known as Lithol Fast Yellow Y) an azo dye derived from o-nitroaniline and acetoacetanilide. (CI 11660).
1~5~
Basic Violet 14r also }nown as Basic ~uchsine, and derived from aniline and toluidine. (CI 42510).
Pigment Orange 2 (commercially available as Ozark Orange X-1481) an azo dye derived from o-nitro-aniline and 2-naphthol. (CI 12060).
The flux composition was coated onto a solder preform which was then positioned within a heat-shrinkable sleeve made ~from cross-linked polyvinylidene fluoride. A
solderable substrate, specifically an insulated wire with lO insulation removed from a segment, was inserted into the sleeve so that the uninsulated segment was positioned inside the sleeve. The sleeve was then heated causing the sleeve to shrink down onto the wire. The initial colour of the flux composition, the temperature at which the flux composition lS changed colour and the final colour of the flux are recorded in Table 1.
~ o O U U ;~ U U U t~ U U O U ' U ~r U
- o o o o o o ooo oo o o o o U ~ ~ ~ ~ ~ ~ ~ ~ ,n O ~ O
O ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~r Q
~ ~ n s u~
u~ o a)~1)~ al oaJ o alo o a) u) ~ (1 Z _ ~ OO ~ ~ ~ ~ ~ ~1 Oc-) O S.C O O O O O OO O O
Q 8 ~~ 8 8 8 8 8 88 ~ ~ u ~,~
o _ ~ ~~ ~ _ ~ ~
~C~ ~
~ .~ a) ~
~'v ~ c~c Z ' c ~ O O ~ , o o I I ~' ~ ~ I I I ! I I ~ I
a) . V
'V ~ ,0 ~ ,0 ,~, ~J dP ~ ~ ~ ~ dP ~ dP ~ ~ ~0 c Ll~ o o u~ o n o o o g O o ' . O .' -- ~ lY7 O ~ J) 3 ~ ' ~0 ~ ~, v v m m m v v v ~ v C ac' v ~
CC ~ ~ ~ ~ ~ C ~ C ~ ~ C ~ 1 C Q~
a) ~ o ~ o c 3 ~ ~ ~ ~ E ~ O
~1 .
~ . .
~ZS'~ll Z
The use of the temperature indicating solder flux composition of this invention has been described above with reference to its use in a soldering device of the heat-recoverable sleeve-type. The novel temperature indicating flux composition can be used in other soldering methods, for example, hand soldering. The temperature indicating flux can be applied in the same manner as flux is usually applied in the particular soldering method, and will change colour at the critical temperature. The io flux can be coated onto a solder preform or incorporated into the solder. It is also possible to apply the flux to the substrate(s) to be soldered.
Thls appllcatlon Is a dlvlslonal appllcatlon of copend-lng appl/catlon No. 412,782 flled October 4, 1982.
Heat-recoverable solderlng devlces are known In the art. See, for example, U.S. Patents Nos. 3,316,125 to Sherlock, 3,305,625 to Ellls, 3,316,343 to Sherlock, 3,396,460 to Wetmore and 3,396,894 to Ellls. Such heat-recoverable devlces generally comprlse a heat shrlnkable polymerlc sleeve havlng a fuslble Insert comprlslng solder. Elongate substrates, such as a palr of wlres, are Inserted Into the sleeve and heat Is applled causlng the sleeve to shrlnk Into contact wlth the substrates. The heat also causes the solder to melt and flow around the substrates.
Upon coollng, a solld solder Jolnt Is formed between the sub-strates. In general, the temperature requlred to melt the solder Is hlgher than the temperature requlred to shrlnk the sleeve.
! Thus, vlsual observatlon that the sleeve has completely recovered does not necessarlly mean that the temperature necessary for sol-derlng has been reached. There Is, therefore, no vlslble Indlca-tlon durlng the solderlng process that enough heat has been applled. Further, In the event that a soldered Jolnt so formed falls durlng use, there Is no way of subsequently Inspectlng the Jolnt to determlne whether the fallure was due to Inadequate heatlng durlng the solderlng process.
;
Copendlng appllcatlon No. 412,782 descrlbes and clalms a solderlng devlce comprlslng a substantlally transparent heat-recoverable polymerlc member, a fuslble solder Insert posltloned wlthln sald member and a solder flux composltlon whlch Is assocl-ated wlth sald solder Insert and whlch undergoes a vlslble colour change at a crltlcal temperature.
l~S'~
The polymerlc member Is substantlally transparent to the extent that the vlslble colour change of the solder f/ux can be seen through the member. Thls devlce thus advantageously pro-vldes a c/ear vlslble Indlcatlon that a so/der ~olnt or connec-t/on has reached the correct solderlng temperature.
The copendlng applIcatlon also dlscloses and clalms a method of solderlng at least two solderable substrates wh/ch com-prlses posltlonlng sald substrates wlthln a heat-recoverab/e sol-derlng devlce accordlng to the flrst aspect of the present Inven-tlon, and heatlng sald devlce, thereby causlng sald heat-recover-able member to recover Into contact wlth sald substrates and sald flux to undergo a vlslble colour change. Preferably the devlce Is arranged such that the heatIng step causes the heat-recover-able member to recover /nto contact wlth the substrates beforethe f/ux undergoes a vlslble co/our change. Preferably the sub-strates are genera/ly e/ongate.
The present Inventlon provldes a solder f/ux compos/-tlon whlch comprlses solder flux and a react/ve component, thef/ux composltlon undergolng a chemlcal react/on resultlng In a vlslble colour change at a crltlcal temperature.
The Inventlon also provldes a method of solderlng at least two solderable substrates located !
adjacent each other, which comprises applying to said subs,rates a quantity of solder and a flux composition according to said third aspect of the present invention, and applying heat to said substrates, solder and fl~x composition 5 until a visible colour change in said 1ux composition occurs.
The heat-recoverable member of the device of the present invention is capable of undergoing a change in its dimensional configuration on application of heat. This 10 change in dimensional config~lration is usually toward an original shape from which it has previously been deformed, but the term "heat-recoverable", as used herein, also includes a member which, on heating, adopts a new configuration even if it has not been previously deformed.
. ' ' lS The heat-recoverable member of the device according to said first aspect of the present invention generally ., . ,.. ,j comprises a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in 1~.5. Patents Nos.
20 2,027,962, 3,086,242 and 3,957,372. The original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, while hot, to a dimensionally heat-unstable form but, in other methods of preparation, a preformed dimensionally 25 heat-stable article is deformed to a dimensionally heat-unstable form in a separate stage.
In the production of the heat-recoverable member, the polymeric material is generally crcss-linked.
One manner of producing a heat-recoverable article comprises 30 shaping the polymeric material into the desired heat-stable form, s~bsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point, or for amorphous materials the sotening point, of the polymer, deforming the article and cooling 35 the article while~ in the deformed state so that the 1~25'~112 -4- ~P0783 deformed state of the article is retained. In use, applica-tion of heat will cause the article to dimensionally recover from the deformed state to the original heat-stable shape.
.
In other articles, as described, for example, in U.S. Patent No. 4,207,364, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating weakens and thus allows the elastomeric member to recover.
Examples of polymers used in the manufacture of heat-recoverable articles include polyolefins, e.g.
polyethylene and copolymers of ethylene with ethylenically unsaturated monomers, such as ethylene/ethyl acrylate, ethylene/vinyl acetate copolymers, polyvinyl chloride, ; 15 elastomers, silicones, polytetraflucroethylene, polyvinyl--. ... ;j"; .. ,~
i idene fluoride, polyurethanes, and ionomers. The polymer can be cross-linked either by radiation or chemical means.
The heat-recovery temperature of crystalline polymers is generally a temperature slightly above the crystalline melting temperature. Polymers, such as polyvinyl chloride, which are not crystalline recover at about their glass transition temperature.
The wall thickness of the member is preferably in the range of from about 0.0005 inch (0.0127mm) to about 0.05 inch (1.2700mm) and is especially preferably from about 0.0008 inch (0.0203mm) to about 0.01 inch(0.2540mm).
The solder insert may be positioned within the heat-recoverable member by coating solder onto the surface of the recoverable member. Alternatively, a solder preform of the desired configuration may be produced and this then lZ54112 inserted into the heat-recoverable member. The solder is positioned such that when two solderable substrates are positioned within the device and the device is heated, the solder is forced into intimate contact with the substrates by the recovery of the heat-recoverable member. When the heat-recoverable member is in the form of a heat-shrinkable sleeve, the solder is preferably in the shape of a ring on the inner surface of the sleeve.
The flux aids the flow of the solder or cleans the surfaces of the substrates to be joined or both. various solder flux compositions are known and are commercially available.
Widely used as solder fluxes are compositions based on natural rosln. Other fluxes include, for example, inorganic and organic acids. In use, the solder flux melts, flows and covers the substrate surface at a temperature below the melting point of the solder. Thus the particular flux used will depend of the nature of the solder in a given application. Any solder flux can be used in accordance with this invention. The flux comprises a temperature indicating component and the particular flux and the appropriate temperature indicating component to be used in a particular application can be readily ascertained by one skilled in the art without undue experimentation. The temperature lndicatlng component ls preferably one that is compatible with the flux and does not interfere wlth the normal functioning of the flux.
The solder flux is associated with the solder of the heat-recoverable soldering device. Any of the conventional means for associating flux with solder can be used. For example, a solder preform can be coated with flux by spraying, dipping, brushing or the like, usually before it has been positioned within the heat-recoverable device. The solder flux can also be used ln soldering operations such as hand soldering, in which a heat-recoverable device is not employed. In this event, the flux can be coated on - .
,; ~
1~ 2 the solder or can be positioned within the solder, fo~
example, in the form of a core which can be in various configurations as is well known in the art. The flux must be visible during the soldering process to detect the colour change in the flux when it reaches the appropriate temperature. It has been found that if the flux is positioned as a core within the solder, flow of the flux on heating renders it visible. A visible colour change occurs when the soldering temperature has been reached. In general, the soldering temperature is higher than the recovery temperature.
Thus continued heating is required after recovery in order to effect the visible colour change of the solder flux.
In accordance with this invention, the solder fluY composition contains a temperature indicator such ~ 15 that the f1ux undergoes a colour change when heated to the - ~ appropriate soldering temperature. The colour change is -~¦ preferably an irreversible colour change, that is a colour change that does not reverse, for example, when the solder and flux cool and solidify. Such an irreversible change provides a continuing indication and permanent means for determining whether the soldered joint was heated to the required temperature during soldering. Thus improperly formed terminations can be detected by visual inspection after the soldered connection is completed and cooled.
The colour change of the flux is preferably from a coloured state to a substantially colourless one. The completed solder joint is thus visible for inspection through the flux. In this way, the joint itself can be inspected to check for adequate soldering and to detect improperly formed terminations, as well as to check for application of suficient heat during the soldering process by the change in colour of the fl~x.
The flux composition changes colour at a critical ~254112 temperature. The desired critical temperature varies depending on the particular solder used. The critical temperature is that temperature which is required to effect a solder connection with the particular solder, that is the temperature required to cause the solder to melt, flow and wet the substrates so that on cooling the solder makes a mechanical and electrical bond between the substrates being soldered. The particular solder to be used varies depending on the substrates being joined and the material of the heat-recoverable member. The temperature required to effect the solder termination is generally above the temperature re~uired to cause recovery of the heat-recoverable member.
Since the critical temperature varies with the nature of the solder, the temperature indicating component of the flux composition varies depending on the solder used. Preferably, the flux composition undergoes a colour change in the temperature range of from about 150C to about 450C, especially preferably from about 200C to about 240C. The temperature of the colour change is preferably in the range of from about 20C to about 60C above the melting point of the solder. Preferably, it is about 20C to about 30C above the melting point of a low temperature solder and about 30C to about 60C above the melting point of a high temperature solder.
As stated above, the flux composition contains a temperature indicator such that at a critical temperature the flux composition undergoes a colour change. Various temperature indicators can be used, for example, azo dyes such as Pigment Red 73 (an azo dye prepared from 2-nitro-p-toludidine and 2-naphthol, CI 12120), acid-base indicators such as Thymol blue, diazo dyes such as Acid Red 73 (a diazo dye derived from p-phenylazoaniline and 2-naphthol-6,8-disulfonic acid, CI 27290), and the like. In general, any dye which is compatible with the flux and which undergoes a colour change at a critical temperature can be used.
, .
12SC~1 ~2 Preferably the flux composition contains a temperature indicator that is a chemically reactive component which undergoes a chemical reaction with the solder flux at a critical tempera-ture to produce a colour change. Partlcularly preferred are flux compositions in which, at a critical temperature, the reactive component causes the flux composition to become colourless since this allows the soldered ~oint to be readily inspected. Suitable chemically reactive components are, for example, Bromocresol Green, Basic Fuchsine or Thymol Blue.
The temperature indicator may be incorporated into a solder flux composition by known techniques. The amount of tem-perature indicator incorporated into the flux is preferably in the range of from about 0.01 to about 5 parts per 100 parts of flux and is especially preferably from about 0.05 to about 2 parts per 100 parts of flux. The amount added depends on the intensity of the colour. Sufficient temperature indicator should be added to provide a flux composition which is clearly visible during the soldering operation. The flux composition may also contain additives, for example, dispersing aids such as water, alcohol or a subfactant or emulsifier, buffers, such as an acid or salt to maintain the desired pH, for example, oxalic acid, lactic acid, maleic acid, tartaric acid, fumaric acid or citric acid, and stabilizers.
An embodiment of a device in accordance with the present invention will now be described by way of example, with reference to the accompanying drawings, wherein:-Figure 1 is a side view of a heat-recoverable device according to the present invention having two elongate substrates positioned therein;
Figure 2 is a side view of the device of Figure 1 after a solder ~oint has been effected between the elongate substrates.
12~i;411~
.
ln Figure l, a heat-recoverable device comprises a heat-recoverable member in the form of a tubular sleeve 3 having a solder insert 4. The sleeve 3 is a heat-shrinkable tube of radiation cross-linked ethylene-tetrafluo~oethylene copolymer containing fusible thermoplastic inserts 5 toward each end of the tube. Prior to being positioned within the sleeve 3 the solder insert 4 is coated with a temperature indicating flux. The coated flux is dark blue in colour and thus obscures the grey colour of the solder insert.
The unrecovered sleeve 3 is positioned over a coaxial cable l having a portion of the outer insulation removed to expose the underlying shield. The end region of a ground wire 2 with the insulation being removed ; from the end region lies adjacent the exposed shield of the 1 . 15 cable 1. The sleeve 3 is then heated causing it to shrink ; ~i into contact with the cable and ground wire and to cause the . solder to melt and flow. On heating, the flux changes colour at a temperature above the melting point of the solder becoming colourless. Heating is discontinued at this point. During heating of the sleeve, the thermoplastic inserts 5 melt and seal the sleeve to the cable. The resulting product is shown in Figure 2.
In Figure 2, sleeve 3 has shrunk into contact with and is sealed to the cable 1. As the flux is now colourless, the grey colour of the solder, 4, is visible through the sleeve. The solder has thus affected a termination between the shield of l and the exposed tip of ground wire, 2.
The following Examples illustrate various solder flux compositions in accordance with the present invention.
Temperature indicating solder flux compositions 125411.~
.
-10- ~P0783 were prepared by dispersing various dyes in a Milros #611, a commercially available rosin-based flux comprising 37 of a mixture of rosin isomers in 63% isopropyl alcohol.
The dyes used and the concentrations of dye in the result-ing temperature indicating flux compositions are listed in Table 1. Additives, as listed in Table 1, were added as appropriate to aid in dissolution of the pigment or to buffer the solution to maintain the desired p~. The dyes used are:
Acid Red 73 (commercially available as Scarlet M
Crude), a diazo dye derived from p-phenylazoaniline and 2-naphthol-6,8-disulphonic acid. (Colour Index, CI, 27290).
Pigment Red 3 (commercially available as Atlasol ' 15 Spirit Red-3) an azo dye prepared from 2-nitro-p-;, toluidine and 2-naphthol. (CI 12120).
''''. ,-~i : ~ Thymol Blue, commercially available and also referred to as thymolsulphonphthalien.
Pigment Red 52 (commercially available as Garnet Toner ~2), an azo dye derived from 2-amino-5-chloro-p-toluenesulphonic acid and 3-hydroxy-2-naphthoic acid.
(CI 15860).
Bromocresol Green, also known as 3',3'',5',5''-tetrabromo-m-cresolsulphonphthalein.
Solvent Red 24, (commercially available as Atlasol Red 4B) an azo dye derived from 4-0-tolylazo-o-toluidine and 2-naphthol. (CI 26105).
Pigment Yellow 5 (also known as Lithol Fast Yellow Y) an azo dye derived from o-nitroaniline and acetoacetanilide. (CI 11660).
1~5~
Basic Violet 14r also }nown as Basic ~uchsine, and derived from aniline and toluidine. (CI 42510).
Pigment Orange 2 (commercially available as Ozark Orange X-1481) an azo dye derived from o-nitro-aniline and 2-naphthol. (CI 12060).
The flux composition was coated onto a solder preform which was then positioned within a heat-shrinkable sleeve made ~from cross-linked polyvinylidene fluoride. A
solderable substrate, specifically an insulated wire with lO insulation removed from a segment, was inserted into the sleeve so that the uninsulated segment was positioned inside the sleeve. The sleeve was then heated causing the sleeve to shrink down onto the wire. The initial colour of the flux composition, the temperature at which the flux composition lS changed colour and the final colour of the flux are recorded in Table 1.
~ o O U U ;~ U U U t~ U U O U ' U ~r U
- o o o o o o ooo oo o o o o U ~ ~ ~ ~ ~ ~ ~ ~ ,n O ~ O
O ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~r Q
~ ~ n s u~
u~ o a)~1)~ al oaJ o alo o a) u) ~ (1 Z _ ~ OO ~ ~ ~ ~ ~ ~1 Oc-) O S.C O O O O O OO O O
Q 8 ~~ 8 8 8 8 8 88 ~ ~ u ~,~
o _ ~ ~~ ~ _ ~ ~
~C~ ~
~ .~ a) ~
~'v ~ c~c Z ' c ~ O O ~ , o o I I ~' ~ ~ I I I ! I I ~ I
a) . V
'V ~ ,0 ~ ,0 ,~, ~J dP ~ ~ ~ ~ dP ~ dP ~ ~ ~0 c Ll~ o o u~ o n o o o g O o ' . O .' -- ~ lY7 O ~ J) 3 ~ ' ~0 ~ ~, v v m m m v v v ~ v C ac' v ~
CC ~ ~ ~ ~ ~ C ~ C ~ ~ C ~ 1 C Q~
a) ~ o ~ o c 3 ~ ~ ~ ~ E ~ O
~1 .
~ . .
~ZS'~ll Z
The use of the temperature indicating solder flux composition of this invention has been described above with reference to its use in a soldering device of the heat-recoverable sleeve-type. The novel temperature indicating flux composition can be used in other soldering methods, for example, hand soldering. The temperature indicating flux can be applied in the same manner as flux is usually applied in the particular soldering method, and will change colour at the critical temperature. The io flux can be coated onto a solder preform or incorporated into the solder. It is also possible to apply the flux to the substrate(s) to be soldered.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A flux composition which comprises solder flux and a chemically reactive component, said flux composition undergoing a chemical reaction resulting in a visible color change at a cri-tical temperature.
2. A flux in accordance with Claim 1, wherein said flux undergoes a change in color due to chemical reaction between said flux and said reactive component at said critical tempera-ture.
3. A flux in accordance with Claim 1, wherein said solder flux comprises a rosin-based solder flux.
4. A flux in accordance with Claim 1, wherein said flux undergoes a change in colour from a coloured state to a sub-stantially colourless state.
5. A flux in accordance with Claim 1 or 2, wherein said chemically reactive component is thymolsulphonphthalein.
6. A flux in accordance with Claim 1 or 2, wherein said chemically reactive component is 3',3'',5',5''-tetrabromo-m-cresolsulphonphthalein.
7. A flux in accordance with Claim 1 or 2, wherein said chemically reactive component is an azo dye derived from aniline and toludine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000560043A CA1254112A (en) | 1981-10-05 | 1988-02-26 | Soldering device, flux and method |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/308,867 US4505421A (en) | 1981-10-05 | 1981-10-05 | Soldering methods and devices |
| US308,867 | 1981-10-05 | ||
| CA000412782A CA1245953A (en) | 1981-10-05 | 1982-10-04 | Soldering device, flux and method |
| CA000560043A CA1254112A (en) | 1981-10-05 | 1988-02-26 | Soldering device, flux and method |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000412782A Division CA1245953A (en) | 1981-10-05 | 1982-10-04 | Soldering device, flux and method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1254112A true CA1254112A (en) | 1989-05-16 |
Family
ID=25669826
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000560043A Expired CA1254112A (en) | 1981-10-05 | 1988-02-26 | Soldering device, flux and method |
| CA000560042A Expired CA1258755A (en) | 1981-10-05 | 1988-02-26 | Soldering device, flux and method |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000560042A Expired CA1258755A (en) | 1981-10-05 | 1988-02-26 | Soldering device, flux and method |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1254112A (en) |
-
1988
- 1988-02-26 CA CA000560043A patent/CA1254112A/en not_active Expired
- 1988-02-26 CA CA000560042A patent/CA1258755A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1258755A (en) | 1989-08-29 |
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