CA1239055A - Vapour phase soldering - Google Patents
Vapour phase solderingInfo
- Publication number
- CA1239055A CA1239055A CA000465695A CA465695A CA1239055A CA 1239055 A CA1239055 A CA 1239055A CA 000465695 A CA000465695 A CA 000465695A CA 465695 A CA465695 A CA 465695A CA 1239055 A CA1239055 A CA 1239055A
- Authority
- CA
- Canada
- Prior art keywords
- solder
- vapor
- bath
- vapour
- soldering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
ABSTRACT
Improvements in or relating to Vapour Phase Soldering.
A method of soldering wherein a component or components to be soldered. such as a printed circuit board and soldered preforms. are immersed in a vapour bath to melt the solder. following which the components are withdrawn from the vapour bath. In the method according to the invention, the vapour bath is composed predominantly of perfluotetradecahydrophenanthrene (C14F24).
Improvements in or relating to Vapour Phase Soldering.
A method of soldering wherein a component or components to be soldered. such as a printed circuit board and soldered preforms. are immersed in a vapour bath to melt the solder. following which the components are withdrawn from the vapour bath. In the method according to the invention, the vapour bath is composed predominantly of perfluotetradecahydrophenanthrene (C14F24).
Description
1239~)5S
This invention relates to the technique known as vapor phase soldering or "condensation reflow soldering".
8 In such a technique, at least one component to be soldered is immersed in a vapor bath to melt the solder and cause it to flow, and the component is then withdrawn from the vapor bath. In one particular well-known application of this technique, electronic - I components incorporating soldered items such as preforms are assembled in desired positions with respect to a circuit board and the assembly is when immersed in a bath of vapor, the latent heat of condensation of which causes the solder to melt and - flow, thus securing the component to the board.
Alternatively or additionally, the component to be soldered may be the circuit board itself.
There are a number of publications describing this technique, which was developed by the Western Electric _, Company. Thus it is described in the journal Tin and its Uses" No. 130 (1981) pages 1-3 and also in Electronic Production, June 1980 pages 21-27.
1'~3~;)55 However, one of the problems connected with this technique is that of selecting a suitable material for the production of the bath vapor. An ideal material should desirably have the following properties:
a. a suitable boiling range, i.e. sufficient to melt the solder b. chemically inert in the vapor phase in the presence of metals, glass, ceramics and polymeric materials etc.
0 c. safe to handle and not liable to produce toxic or corrosive substances during its evaporation/
condensation cycle in the presence of metals, glass, ceramics, and polymeric materials, and moisture d. recoverable by condensation 1- e. non-flammable f. of high-vapour density to form a heavy layer in the vessel g. excellent dielectric properties h. not leaving residues after evaporation i. melts below room temperature.
The use of various fluids in this context is described in the two references referred to above.
However, the prior art fluids do not meet all the above criteria. The biggest outstanding problems are the formation of (1) perfluoroisobutylene (fib) and (11) acidic products, e.g. hydrogen fluoride, during the guy course of the evaporatlon/condensatlon cycle used In the vapor-soldering technique. These problems are referred to In the sea-on of the references died above. Perfluorolsobutylene Is highly toxic (tlme-welghted average threshold limit value for a 8-hour work-day - 0.01 Pam).
We have now found that a particularly effective and safe vapour-phase soldering technique can be devised If the essential heat-transfer vapor Involved In the process Is come posed predominantly of perfluorotetradecahydrophenanthrene (C14F24).
The present Invention provides a method of soldering wherein a component to be soldered Is Immersed In a vapor bath to melt the solder, and the component Is then withdrawn from the vapor bath, wherein the vapor bath Is composed predominantly of perfluorotetradecahydrophenanthrene (C14F24).
Preferably there Is used a component which carries a solder having a molting point below 200C. The solder used may be a 60t40 tlntlead solder.
The Invention also provides a vapour-phase solder bath composed predominantly of perfluorotetradecahydrophenanthrene (C1 4F24 ) -It will be appreciated that the component to be sol-dewed may be any component having applied thereto or carrying a solder which may flow when melted by the heat 1~3~(~SS
of the vapoue phase. As indicated previously, such a component may for example be a printed circuit board or one or more soldered items such as preforms to be applied to a circuit board. Such components (i.e.
5 circuit board and preforms) would usually be treated together by the method of the invention i.e. in the same vapor bath, but it is nevertheless envisaged that the components could be separately treated in the vapor bath and subsequently joined together.
13 The preparation and physical properties of the perfluorotetradecahydrophenanthrene are well documented in the chemical literature (see for example US patent no. US-A-2459780 and Tetrahedron 19~(12) 1893-1901 (1963)). The boiling point of the material and its 1 other relevant physical properties can be summarized as follows:
Molecular weight 624 Density, kg/l (liquid) 2.03 Vapor density, (gel) 24.8 (SUP) Boiling point, C 215 Pour point typical C Kiwi Electrical resistivity (minimum) 10 ohm.cm Dielectric strength (minimum) 13 KVtmm.
It has now been determined, experimentally, that in a series of evaporation/condensation cycles in the 1~3~C155 presence of solder alloys and polymeric materials, the production of perfluoroisobutylene from the perfluorotetradecahydrophenanthrene is non-detectable using gas chromatography (limit 1 part in 101 by weight) with an electron-capture detector linked to a maws spectrometer, compared with the greater than O.lppm of fib found with a known vapour-pha~e soldering fluid Skye TV e (a per fluorinated tertiary amine-oommc~cially known as Fluorinert RUM FC70) using the save 13 separation/detection techniques (see Turbine and Ado, Electronic Production, June 1980, pages 21 to Z7).
The perfluorotetradecahydrophenanthrene is suitable for use with solders melting below 200C. Typical solder compositions which may be used in the method 1-. according to the invention are given below:
Solder Composition White%) Molting Point/ranqe (C) Sun Pub Sub A Cud 62 35.7 2.0 0.3 179 23 51.2 30.6 18.2 145 The invention will now be further illustrated by reference to the following non-limiting Examples in which:
1'~3~VSS
Example 1 describes the use of perfluorotetradecahydro-phenanthrene when used as a vapour-phase soldering fluid In five Instances (a) to (e) In the method according to the Invention;
Example 2 describes the analytical procedure used to determine the fib content of fluid vapor, for the fluid to be used In the method according to this Invention (designated under the trademark Flute PP11 In the Examples) In comparison with a prior art fluid (supplied under the trademark Fluorlnert FC 70).
Example 3 Illustrates the relative thermal stability of the fluid to be used In the method according to the Invention compared with a prior art fluid (Fluorlnert FC 70).
Flute PP11 (a trademark for perfluorotetradecahydro-phenanthrene) (10 kg) was poured Into a Hybrid Technology Company "Phase 4" vapour-phase soldering tank. The liquid was heated to boiling and a vapor layer was established (after about 20 men-vies at 3.5 Ow power Input). Trlchlorotrlfluoroethane (about 10 ml) was then poured Into the tank to form a secondary vapor zone, above the Flute PP11 vapor.
~2~390SS
At this stage the heater control was set on 'low.
The following tests were then conducted:
1 (a) 74 connectors were inserted in a tin-lead through-plated board and 60/40 Snub solder-ring preforms were fitted. 26 of the connectors were gold plated and the remainder were tin-lead plated. The assembly was lowered into the Flute PPlllvapour for a total dwell time of 20 seconds, followed by a 1 minute dwell in the secondary vapor zone. The assembly was I removed for inspection and all joints were found to be satisfactorily soldered by visual inspection.
(b) The above test was repeated using 28 gold-plated connectors and 56 tin-lead plated connectors. All joints were found to be satisfactorily I soldered.
(c) Two 'chip carriers', each having eighteen solder paste (tin-lead, 60/40) coated connectors, were placed on corresponding tin-lead ~60/40) coated pads on a ceramic substrate. The assembly was lowered into the Flute PPlllvapour zone for 20 seconds, followed by a one minute dwell in the secondary vapor zone. All joints were found to be satisfactorily soldered.
(d) The above test was repeated, except that a chip carrier was placed on each side of a horizontally r k) - 8 orientated ceramic substrate. the lower chip being fixed in place by surface tension. All joints were found to be satisfactorily soldered by visual inspection.
(e) A tin-lead solder (60~40) coated printed 5 circuit board, lo cm x lo cm, was cleaned with hydrochloric acid, rinsed with distilled water and dried with absorbent paper. The circuit board was then ( a I
lowered for 30 seconds into the Flute Ply vapor zone, followed by a dwell time of l minute in the secondary 13 vapor zone. Satisfactory reflow of the tin-lead occurred, i.e. the solder flowed over the circuit board.
An evaporation Yank was filled with vapor phase soldering fluid to a depth of about one inch (2.5cm) 1- above the level of immersion heaters. A copper cooling coil was fixed so that it was about three inches (7.6cm) above the liquid level and water flow was turned on.
The heaters were switched on full to start with and then back to about half power once the boiling had commenced 23 and a vapor layer had been established at cooling coil level.
The system was sampled at a level three inches ivies (7.6 cm) above the vapor layer, at half hourly Intervals over a period of four hours.
Analysis of the samples for pflb (perfluorolsobutylene) was performed using a gas chromatography with electron capture detector and a gas sample valve equipped with a 5 cc sampling loop. A 12 ft. x 1/8 Inch (366 x 0.3 cm) Carbowax porously C.
100-120 mesh column was used (Carbowax and Porously are trade-marks). Analytical procedures Included an Initial column temper-azure hold at 60C for 10 minutes followed by temperature pro-grammlng at the rate of 20/mln. up to a maximum of 140C. The maximum temperature was maintained until all high boilers had eluded from the column and the detector had cleaned off (1 1/2 to
This invention relates to the technique known as vapor phase soldering or "condensation reflow soldering".
8 In such a technique, at least one component to be soldered is immersed in a vapor bath to melt the solder and cause it to flow, and the component is then withdrawn from the vapor bath. In one particular well-known application of this technique, electronic - I components incorporating soldered items such as preforms are assembled in desired positions with respect to a circuit board and the assembly is when immersed in a bath of vapor, the latent heat of condensation of which causes the solder to melt and - flow, thus securing the component to the board.
Alternatively or additionally, the component to be soldered may be the circuit board itself.
There are a number of publications describing this technique, which was developed by the Western Electric _, Company. Thus it is described in the journal Tin and its Uses" No. 130 (1981) pages 1-3 and also in Electronic Production, June 1980 pages 21-27.
1'~3~;)55 However, one of the problems connected with this technique is that of selecting a suitable material for the production of the bath vapor. An ideal material should desirably have the following properties:
a. a suitable boiling range, i.e. sufficient to melt the solder b. chemically inert in the vapor phase in the presence of metals, glass, ceramics and polymeric materials etc.
0 c. safe to handle and not liable to produce toxic or corrosive substances during its evaporation/
condensation cycle in the presence of metals, glass, ceramics, and polymeric materials, and moisture d. recoverable by condensation 1- e. non-flammable f. of high-vapour density to form a heavy layer in the vessel g. excellent dielectric properties h. not leaving residues after evaporation i. melts below room temperature.
The use of various fluids in this context is described in the two references referred to above.
However, the prior art fluids do not meet all the above criteria. The biggest outstanding problems are the formation of (1) perfluoroisobutylene (fib) and (11) acidic products, e.g. hydrogen fluoride, during the guy course of the evaporatlon/condensatlon cycle used In the vapor-soldering technique. These problems are referred to In the sea-on of the references died above. Perfluorolsobutylene Is highly toxic (tlme-welghted average threshold limit value for a 8-hour work-day - 0.01 Pam).
We have now found that a particularly effective and safe vapour-phase soldering technique can be devised If the essential heat-transfer vapor Involved In the process Is come posed predominantly of perfluorotetradecahydrophenanthrene (C14F24).
The present Invention provides a method of soldering wherein a component to be soldered Is Immersed In a vapor bath to melt the solder, and the component Is then withdrawn from the vapor bath, wherein the vapor bath Is composed predominantly of perfluorotetradecahydrophenanthrene (C14F24).
Preferably there Is used a component which carries a solder having a molting point below 200C. The solder used may be a 60t40 tlntlead solder.
The Invention also provides a vapour-phase solder bath composed predominantly of perfluorotetradecahydrophenanthrene (C1 4F24 ) -It will be appreciated that the component to be sol-dewed may be any component having applied thereto or carrying a solder which may flow when melted by the heat 1~3~(~SS
of the vapoue phase. As indicated previously, such a component may for example be a printed circuit board or one or more soldered items such as preforms to be applied to a circuit board. Such components (i.e.
5 circuit board and preforms) would usually be treated together by the method of the invention i.e. in the same vapor bath, but it is nevertheless envisaged that the components could be separately treated in the vapor bath and subsequently joined together.
13 The preparation and physical properties of the perfluorotetradecahydrophenanthrene are well documented in the chemical literature (see for example US patent no. US-A-2459780 and Tetrahedron 19~(12) 1893-1901 (1963)). The boiling point of the material and its 1 other relevant physical properties can be summarized as follows:
Molecular weight 624 Density, kg/l (liquid) 2.03 Vapor density, (gel) 24.8 (SUP) Boiling point, C 215 Pour point typical C Kiwi Electrical resistivity (minimum) 10 ohm.cm Dielectric strength (minimum) 13 KVtmm.
It has now been determined, experimentally, that in a series of evaporation/condensation cycles in the 1~3~C155 presence of solder alloys and polymeric materials, the production of perfluoroisobutylene from the perfluorotetradecahydrophenanthrene is non-detectable using gas chromatography (limit 1 part in 101 by weight) with an electron-capture detector linked to a maws spectrometer, compared with the greater than O.lppm of fib found with a known vapour-pha~e soldering fluid Skye TV e (a per fluorinated tertiary amine-oommc~cially known as Fluorinert RUM FC70) using the save 13 separation/detection techniques (see Turbine and Ado, Electronic Production, June 1980, pages 21 to Z7).
The perfluorotetradecahydrophenanthrene is suitable for use with solders melting below 200C. Typical solder compositions which may be used in the method 1-. according to the invention are given below:
Solder Composition White%) Molting Point/ranqe (C) Sun Pub Sub A Cud 62 35.7 2.0 0.3 179 23 51.2 30.6 18.2 145 The invention will now be further illustrated by reference to the following non-limiting Examples in which:
1'~3~VSS
Example 1 describes the use of perfluorotetradecahydro-phenanthrene when used as a vapour-phase soldering fluid In five Instances (a) to (e) In the method according to the Invention;
Example 2 describes the analytical procedure used to determine the fib content of fluid vapor, for the fluid to be used In the method according to this Invention (designated under the trademark Flute PP11 In the Examples) In comparison with a prior art fluid (supplied under the trademark Fluorlnert FC 70).
Example 3 Illustrates the relative thermal stability of the fluid to be used In the method according to the Invention compared with a prior art fluid (Fluorlnert FC 70).
Flute PP11 (a trademark for perfluorotetradecahydro-phenanthrene) (10 kg) was poured Into a Hybrid Technology Company "Phase 4" vapour-phase soldering tank. The liquid was heated to boiling and a vapor layer was established (after about 20 men-vies at 3.5 Ow power Input). Trlchlorotrlfluoroethane (about 10 ml) was then poured Into the tank to form a secondary vapor zone, above the Flute PP11 vapor.
~2~390SS
At this stage the heater control was set on 'low.
The following tests were then conducted:
1 (a) 74 connectors were inserted in a tin-lead through-plated board and 60/40 Snub solder-ring preforms were fitted. 26 of the connectors were gold plated and the remainder were tin-lead plated. The assembly was lowered into the Flute PPlllvapour for a total dwell time of 20 seconds, followed by a 1 minute dwell in the secondary vapor zone. The assembly was I removed for inspection and all joints were found to be satisfactorily soldered by visual inspection.
(b) The above test was repeated using 28 gold-plated connectors and 56 tin-lead plated connectors. All joints were found to be satisfactorily I soldered.
(c) Two 'chip carriers', each having eighteen solder paste (tin-lead, 60/40) coated connectors, were placed on corresponding tin-lead ~60/40) coated pads on a ceramic substrate. The assembly was lowered into the Flute PPlllvapour zone for 20 seconds, followed by a one minute dwell in the secondary vapor zone. All joints were found to be satisfactorily soldered.
(d) The above test was repeated, except that a chip carrier was placed on each side of a horizontally r k) - 8 orientated ceramic substrate. the lower chip being fixed in place by surface tension. All joints were found to be satisfactorily soldered by visual inspection.
(e) A tin-lead solder (60~40) coated printed 5 circuit board, lo cm x lo cm, was cleaned with hydrochloric acid, rinsed with distilled water and dried with absorbent paper. The circuit board was then ( a I
lowered for 30 seconds into the Flute Ply vapor zone, followed by a dwell time of l minute in the secondary 13 vapor zone. Satisfactory reflow of the tin-lead occurred, i.e. the solder flowed over the circuit board.
An evaporation Yank was filled with vapor phase soldering fluid to a depth of about one inch (2.5cm) 1- above the level of immersion heaters. A copper cooling coil was fixed so that it was about three inches (7.6cm) above the liquid level and water flow was turned on.
The heaters were switched on full to start with and then back to about half power once the boiling had commenced 23 and a vapor layer had been established at cooling coil level.
The system was sampled at a level three inches ivies (7.6 cm) above the vapor layer, at half hourly Intervals over a period of four hours.
Analysis of the samples for pflb (perfluorolsobutylene) was performed using a gas chromatography with electron capture detector and a gas sample valve equipped with a 5 cc sampling loop. A 12 ft. x 1/8 Inch (366 x 0.3 cm) Carbowax porously C.
100-120 mesh column was used (Carbowax and Porously are trade-marks). Analytical procedures Included an Initial column temper-azure hold at 60C for 10 minutes followed by temperature pro-grammlng at the rate of 20/mln. up to a maximum of 140C. The maximum temperature was maintained until all high boilers had eluded from the column and the detector had cleaned off (1 1/2 to
2 hours). The detector temperature was maintained at 325C.
Further, the gig column was linked to a mass spectrograph. This Increased the sensltlvlty for perfluorolosbutylene, down to a detection limit of 0.0001 Pam by weight fib.
Using boiling Flute PP11 (a trademark) In the test tank described above, no perfluorolsobutylene could be detected.
LO Turblnl and F M Ado (Electronic Production, June 1980, pages 21 to 27), using a similar system filled with the perfluorlnated tertiary amine Fluorlnert FC70, found slgnlfIcant levels of fib In the vapor (e.g.
12~ US
0.14 Pam fib in one example and greater than 1 Pam fib in a second).
a I cry or C Flute PPlll~perfluorotetra(de~hydrophenanthrene) - was compared with Fluorinert FC701by the following method:
The two separate liquids (200 ml. each) were heated under reflex in glass apparatus in the presence of copper filings (1 gym.). Samples were taken at 2 h., 13 oh., and 16 h intervals and compared for reactive fluoride (expressed as F') and acidity (HO) content.
The results are given below:
FC70 Pull Flux F', Acidity, F', Acidity, 1, Time gel ~lequiv./ml. gel /~equiv./ml.
Start 2 NOD. 1 NOD.
2 his 39 _ 16 his. 68 0.54 1 NOD.
I In order to s mutate the practice situation more owe or) 'to I
closely, Flute PP11Jand Fluorinert FC701were compared in a laboratory vapor phase soldering tank. In this 123g~55 unit the liquid was in direct contact with metal heating elements and the vapor was condensed by means of water-cooled copper coils.
Each liquid was separately heated under reflex for 4 hours followed by measurement of acidity and reactive fluoride concentration. The results are given below.
, Acidity,~equiv./ml. F,/ug./ml.
Liquid Before After Be eye After Reflex Reflex Reflex I Reflex I FC70 NOD. 0.04 2 30 Pull NOD. I NOD. 1 NOD. = Not detectable.
Conclusion:
I I
Flute Plus significantly more stable than Fluorinert ~vq~
I FC701when used for vapor phase soldering.
Further, the gig column was linked to a mass spectrograph. This Increased the sensltlvlty for perfluorolosbutylene, down to a detection limit of 0.0001 Pam by weight fib.
Using boiling Flute PP11 (a trademark) In the test tank described above, no perfluorolsobutylene could be detected.
LO Turblnl and F M Ado (Electronic Production, June 1980, pages 21 to 27), using a similar system filled with the perfluorlnated tertiary amine Fluorlnert FC70, found slgnlfIcant levels of fib In the vapor (e.g.
12~ US
0.14 Pam fib in one example and greater than 1 Pam fib in a second).
a I cry or C Flute PPlll~perfluorotetra(de~hydrophenanthrene) - was compared with Fluorinert FC701by the following method:
The two separate liquids (200 ml. each) were heated under reflex in glass apparatus in the presence of copper filings (1 gym.). Samples were taken at 2 h., 13 oh., and 16 h intervals and compared for reactive fluoride (expressed as F') and acidity (HO) content.
The results are given below:
FC70 Pull Flux F', Acidity, F', Acidity, 1, Time gel ~lequiv./ml. gel /~equiv./ml.
Start 2 NOD. 1 NOD.
2 his 39 _ 16 his. 68 0.54 1 NOD.
I In order to s mutate the practice situation more owe or) 'to I
closely, Flute PP11Jand Fluorinert FC701were compared in a laboratory vapor phase soldering tank. In this 123g~55 unit the liquid was in direct contact with metal heating elements and the vapor was condensed by means of water-cooled copper coils.
Each liquid was separately heated under reflex for 4 hours followed by measurement of acidity and reactive fluoride concentration. The results are given below.
, Acidity,~equiv./ml. F,/ug./ml.
Liquid Before After Be eye After Reflex Reflex Reflex I Reflex I FC70 NOD. 0.04 2 30 Pull NOD. I NOD. 1 NOD. = Not detectable.
Conclusion:
I I
Flute Plus significantly more stable than Fluorinert ~vq~
I FC701when used for vapor phase soldering.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method of soldering wherein a component to be soldered which carries solder, is immersed in a vapour bath to melt the solder, and the component is then withdrawn from the vapour bath, the improvement wherein the vapour bath is composed predominantly of perfluorototradecahydrophenanthrene (C14F24).
2. The method according to claim 1, wherein the solder has a melting point below 200°C.
3. The method according to claim 2, wherein the solder is a 60/40 tin/lead solder.
4. A vapour phase solder bath composed predominantly of perfluorotetradecahydrophenanthrene (C14F24).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000465695A CA1239055A (en) | 1984-10-17 | 1984-10-17 | Vapour phase soldering |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000465695A CA1239055A (en) | 1984-10-17 | 1984-10-17 | Vapour phase soldering |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1239055A true CA1239055A (en) | 1988-07-12 |
Family
ID=4128944
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000465695A Expired CA1239055A (en) | 1984-10-17 | 1984-10-17 | Vapour phase soldering |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1239055A (en) |
-
1984
- 1984-10-17 CA CA000465695A patent/CA1239055A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |