JPH04503187A - Perfluoroheptaglyme - Improved Vapor Phase Soldering Fluid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Perfluorinated Hebuta Glyme - Improved Vapor Phase Soldering is a Liquid Background of the Invention A preferred method for soldering a series of joints uses pre-positioned elements to melt the solder. It involves immersion in a sufficiently hot steam bath. steaming The latent heat of ignition (condensation) causes the solder to melt as the vapor condenses on the cold surface. Preferably, a solder having a melting point of about 200° C. or less is used. More information Conventional soldering offers several advantages over methods, the most notable being that it provides extremely rapid heating. For example, steam has a large heat capacity The entire circuit board can be heated evenly because it condenses on cooler elements. Uniform heating minimizes polymer decomposition, resulting in a clean final product with minimal metal oxidation Goods can be obtained. For these reasons, vapor phase soldering has become widely used in the electronics industry. The two most commonly used vapor phase soldering liquids are perfluorotripentyl perfluorotetradecahydrophenanthrene (U.S. special No. 4.549.686). Briggs (Brazin Soldering. 7: 6-8.12 (1984)) describes the use of a liquid phase for vapor phase reflow soldering of perfluoropolyethers. There is. One particular liquid has the structure: CFs[(QCF(CFS)CFz)--(QCFri,)OCFS, with an n/m ratio of 40. Dishart is a low molecular weight hexafluoropropylene oxide having the formula: F[CF(CFs)CFzOconcFzcFs, where n is 1 to 9. A vapor phase heat exchange method using oligomers is described. Calini and 14odena (European Patent Application 269,029) are perfluoroethers suitable for several vapor phase soldering applications. For example, perfluoropentaglyme is described. SUMMARY OF THE INVENTION The present invention provides novel perfluoropolyethers, perfluorinated hebutyglynes, and and vapor phase soldering is an improved vapor phase soldering method that uses perfluoroheptaglyme as the liquid. DETAILED DESCRIPTION OF THE INVENTION The present invention is also known as "vapor phase soldering" and "vapor phase solder reflow process." This invention relates to condensed soldering technology. Satisfactory soldering requires manufacturing liquid. In order to melt the solder, the liquid must have a high enough boiling point to melt the solder. do not have. Since the liquid is refluxed into the bath, it must be oxidatively stable at its boiling point. metals, polymeric materials, and the flash typically present on printed circuit boards. must be chemically inert in the vapor phase in the presence of the gas. This liquid must be recoverable by condensation and should be non-flammable. this liquid The body should have good dielectric properties and should have a melting point below room temperature. Finally, the ideal liquid would have a high heat of vaporization, be non-toxic and leave no residue after evaporation. Vapor phase soldering uses perfluoropolyether, perfluoroheptaglyme, CF5O(CF2CF to)7cFs as a liquid, and prior art vapor phase soldering has several advantages in this ability over liquids. It was found here that it is possible to submit the following. The most notable advantages are: (1) Perfluorohebbuta lime does not have more than two consecutive difluoromethylene units, making it less likely to produce lethal perfluoroisobutylene during reflux. The performance is significantly reduced (the time-weighted average critical threshold for 8 hour days is Q, 0 11)l)l). No evidence of perfluoroisobutylene was found using gas chromatography techniques in the state of the art. This means that preferably above 0.1 apH, which is often produced from FCl2. compared to the level. (2) The cost of producing perfluoroheptaglyme is likely to be lower than that of producing prior art liquids. Hepta Glyme is an inexpensive starting point Since the yield of direct fluorination is relatively high despite the high quality, cost savings are expected. (3) When using higher molecular weight perfluoroheptaglyme (966 versus 624 for perfluorotetradecaphenanthrene and 821 for FCl2). In some cases, heat exchange is more effective than with prior art liquids of lower molecular weight and comparable boiling points. (4) Since perfluorohebbuta-glyme is a single molecular fluid, it Low molecular weight oligomers of hexafluoropropylene oxide such as those described by , and hexafluoropropylene oxide and dioxide described by Briggs. Superior to copolymers with fluoromethylene. The composition of a fluid, which consists of a mixture of components with different molecular weights, constantly changes as the more volatile components evaporate, resulting in a higher boiling point fluid over time. (5) Perfluorohebbuta lime has a boiling point of 205°C, which is currently used in industry. It is superior to the perfluoropentaglyme described by Calim and Modena, as it is more suitable for the solders that are used. To produce perfluoroheptaglyme by the method described in the present invention, firstly, perfluoroheptaglyme is Manufactures taglime. Heptaglyme can be produced in a variety of ways, two of which are described below: (1) Diethylene glycol monomethyl ether is reacted with sodium metal to form an alkoxide, which is then converted into 1,2-bis- (2-chloroethoxy)-ethane to form heptaglyme. can be done. (2) Instead of this, triethylene glycol monomethyl ether can be used as thionine chloride. It is also possible to replace the hydroxyl groups with chlorine by reacting with chlorine, which can then be reacted with an alkoxide obtained by reacting tetraethylene glycol monomethyl ether with sodium. Regardless of the method used, hepta lime is easily vaporized under reduced pressure. The pure product can be obtained by distillation. This heptaglyme is then perfluorinated, preferably by direct fluorination techniques. Because elemental fluorine is reactive in nature, fluorine can be removed by inert gases such as nitrogen. It is advantageous to dilute with hydrogen or helium. Fluorine is typically diluted with nitrogen, and as the degree of fluorination increases, the concentration of fluorine usually increases. This anti Since the reaction is highly exothermic, fluorination must be carried out gradually unless provision is made to rapidly remove the heat of reaction. Immersing the reactor in a cooled liquid bath is also usually a reasonable method of obtaining commercially acceptable reaction rates. Gaseous fluorine is the preferred fluorinating agent and has a sufficiently high purity level and is acceptable. It is available at a cost that is reasonable. Using other fluorinating agents such as chlorine trifluoride However, some chlorine substitution may also occur. The fluorination reaction is generally carried out at a temperature of about -80 to about +200C, preferably -20 to +20C. This reaction can be carried out in a reactor with a UV source or in the dark. Using the preferred temperature range, sufficient fluorine It is not necessary to have an ultraviolet light source as it is reactive in minutes. If an ultraviolet light source is used, a wavelength of 250 to 350 no+ is preferred. If the reactor is illuminated by an external light source, a transparent window that does not react with fluorine or hydrogen fluoride is required. Stone coated with a thin film of fluorinated ethylene-propylene copolymer British lenses give good results. The present fluorination reaction can be carried out in various ways. inert solid, analogy Sodium fluoride powder is coated with heptaglyme to make it a free-flowing powder; It can be fluorinated in a fixed tube, in a rotating drum reactor or in a fluidized bed. The yields associated with this type of reaction primarily give high molecular weight branched products. It is generally of poor quality due to the large number of side reactions it causes. Much higher yields are obtained by dissolving the heptaglyme in a solvent that is inert to fluorine. Biershenk, L. Juhlke, Kawa and Lagov, “Liquid Phase Fluorination,” the suggestion of which is incorporated by reference, September 28, 1988. (Liquid Phase Fluorination)” U.S. Patent Application Serial No. 07/250.376 entitled "Liquid Phase Fluorination," filed September 28, 1989, Patent Attorney Case No. See EXF1a-06A. For example, 1.1.2-trichlorotho Lifluoroethane (Freon 113”) does not appreciably react with fluorine when used in the preferred temperature range and serves as a good reaction solvent. function. Other suitable solvents are perfluorocarbons, perhalogenated chlorofluorocarbons, carbon and perhalogenated chlorofluoroethers. This reaction Batch mode, in which all the Hebuta Glyme is dissolved in the solvent prior to chlorination, also The Hebuta Glyme is continuously pumped into the solvent while the Primer is bubbled into the solution. It can also be carried out in continuous mode. In general, continuous operation yields better gives better product quality, and improved speed. If this reaction is carried out in a solvent, use a hydrogen fluoride scavenger, such as sodium fluoride. Hydrogen fluoride may be present in the solution to trap the byproduct hydrogen fluoride, or However, the preferred manner of carrying out this reaction is to Hydrogen fluoride is present to form a complex with all the generated hydrogen fluoride. Ru. Fluorination of the ether in the presence of sodium fluoride provides improved yields while minimizing chain cleavage and rearrangement. This suggestion is clearly explained in this case. See U.S. Pat. In general, perfluorohebbuta-glyme is preferably used in a solvent, such as 1.1. Coupling heptaglyme into a stirred reactor containing 2-trichlorotrifluoroethane. The temperature is maintained at about -20°C to about +20°C. Dilute fluorine gas is the preferred fluorinating agent and reacts well in the absence of ultraviolet light. Fluorine should be diluted to below the flammability limit (in fluorine) of the liquid medium. Sufficient sodium fluoride is present to complex all of the byproduct hydrogen fluoride. When present, excellent yields are obtained. The products obtained in this manner generally have a purity of 90 to 95% and a residual hydrogen content of 0.001% or less. Essentially residual hydrogen and reactive components from reactive end groups, e.g. chain cracking reactions. A final fluorination of several hours with 50% fluorine at around 175° C. gives good results in order to obtain a liquid that does not contain any of the fluorinated acyl groups formed by the fluorine. The resulting inert liquid is then distilled to provide sufficient water for most applications. perfluoroheptaglyme of sufficient purity can be obtained. This reaction can be best summarized by the following equation: CHs OCH2CH20CHx CH! OH+ Na →Na0CHxC HzOCH*CHtOCHs + 1/2Hz2NaOCHiCHzOCHzC HtOCHs+ CI CHt CH20CHt CH! OCH2CH! Cl-CH30(CHICH,O), CH3CFsO(CFzCFtO)tCFs+34NaHF Under the law, soldering is done by evaporating elements that should not be soldered to perfluorinated butaglyme. Immerse it in an air bath to dissolve the solder. The soldered elements are then removed from the bath. The preferred solder is 60/40 tin/lead (Sn/Pb) solder, which generally has a melting point below about 200°C. Any solder that can be used can be used. This method is particularly useful for soldering electrical components on printed circuit boards. The following examples further illustrate the invention. Example 1: Synthesis of Hebuta Glyme 1500 liters of diethylene glycol methyl ether were placed in a 3 liter dry flask flushed with nitrogen and equipped with a mechanical stirrer. flask temperature 138 g of sodium metal (6 moles) was added in small chunks intermittently over 2 hours while maintaining the temperature below 70°C. After 24 hours, all the sodium had reacted, so 561 g of 1,2-bis-(2-chloroethoxy)-ethane (3 mol) was gradually added over 2 hours. The mixture was kept at approximately 50°C in a water bath while the contents of the flask were reacting. The mixture was stirred at room temperature overnight and then at 70°C for 1 hour. To recover the product hebutaglyme, first mix it with hydrochloric acid. The pH of the compound was adjusted to 6, followed by filtration and evaporation of the filtrate. 552 g of a bright yellow liquid, heptaglyme, was recovered with a yield of 52% (7a ■ boiling point in Hg 200-213°C). Example 2: Fluorination of Hepta Glyme in a Rotating Drum Reactor A 750 μl rotating drum reactor was charged with 175 g of finely ground sodium fluoride. 5 g of Hebuta Glyme coating was added. This free-flowing mixture was purged with nitrogen for 2 hours while the reactor was rotating at a speed of 45 revolutions per minute. The reactor was cooled to -13°C using a cold bath, while the reactant gas stream was injected with fluorine and and nitrogen at 17°5 cc/min and 200 cc/min, respectively. These conditions were maintained for 28 hours, after which the reactor was gradually heated to 35° C. over a period of 12 hours. Once the reactor temperature reached 35°C, the nitrogen flow was stopped and the reactor contents were exposed to pure fluorine for several hours. The crude product mixture was removed from the reactor and subsequently purged with several volumes of nitrogen. The product was extracted with approximately 1 liter of 1,1,2-trichlorotrifluoroethane and the 1,1°2-trichlorotrifluoroethane was flashed off using a rotary evaporator to yield 38.9 g of fluid. Obtained. This fluid was distilled to obtain 9.2 g of perfluoroheptaglyme. The remainder is the main It was a more non-volatile substance consisting of dimers and trimers of perfluorohebbutaglyme (yield 19%). Example 3: Fluorination of Hepta Glyme in a Batch Solvent Reactor 200.6 g of lime, 4 liters of 1.1.2-)lichlorotrifluoroethane A mixture of 800 g of sodium fluoride powder was prepared through a 10” pipe. The reactor was placed in a 2 foot long aluminum reactor. The reactor was rotated at 60 revolutions per minute in a water/ethylene glycol bath maintained at -10°C. The reactor was flushed with nitrogen for several hours prior to beginning the fluorination. A gas flow of 400 cc/min of fluorine and 800 cc/min of nitrogen was maintained for 14 hours, then for the next 5 hours the fluorine and nitrogen flows were reduced to 300 and 600 cc/min, respectively, during which time The reactor was gradually heated to 70°C. The contents of the reactor were exposed to pure fluorine overnight (12 hours) at 70°C, then cooled to room temperature and flushed with several volumes of nitrogen. The contents of the reactor were filtered and the NaF was washed several times with approximately 3 liters of 1.1.2-trichlorotrifluoroethane. The filtrate was collected and distilled to remove 1.1.2-trichlorotrifluoroethane, leaving 401.5 g of fluid. Approximately 50% of the yield was distilled as perfluorobutylene (boiling point 205°C). Example 4: Fluorination of heptaglyme using a continuous addition solvent reactor over approximately 10 in. 5.5 liters of 1.5 liters in a cylindrical, 22 liter stirred aluminum tank, 2 feet high. 1, 2-trichlorotrifluoroethane and 900 g of sodium fluoride powder were charged. Hydrocarbon water in continuous addition solvent reactor Substance fluorination is more fully described in U.S. Patent Application Serial No. 07/250.376 entitled "Liquid Phase Fluorination". The reactor was placed in a water/ethylene glycol bath maintained at approximately 0°C. The reactor is equipped with a condenser kept at -30℃. This condenses the 1°1,2-trichlorotrifluoroethane and returns it to the reactor. The reactor is purged by the gas mixture used for lime fluorination. The reactor was purged with several volumes of nitrogen prior to beginning the fluorination. 1.1.2-Trick 253 g of Hebutagra diluted with lorotrifluoroethane to a total volume of 660 Ill. Imu was pumped into the reactor over a period of 22 hours. During the reaction, a gas flow of about 450 to 525 cc/min of fluorine and 1500 cc/min of nitrogen was used. anti Monitor the reactor exhaust gas throughout the reaction to ensure that the incoming hepta-glyme is completely flushed out. ensured that sufficient fluorine was supplied for oxidation. Typically, the exhaust gas contained about 5% fluorine, indicating that a slight excess of fluorine was being used. After the reaction, the contents of the reactor were filtered. Remove several liters of the insoluble portion of the mixture. of 1.1.2-trichlorotrifluoroethane. Collect and evaporate the filtrate. 428 g of fluorocarbon fluid was obtained. This fluid was treated with 50% fluorine at 175° C. to yield a fluid of similar weight containing virtually no hydrogen. A second distillation isolated 396 g of hebuta lime (57% yield). Example 5: Soldering Compatibility of Perfluorinated Hebuta Glyme with Flux Perfluorinated hebutylene was poured into a vapor phase soldering tank. this liquid The body was heated to its boiling point to form a vapor layer. Soldering, which is a typical example of industrially used flux, is a glass slice coated with Solder Flux 611” (Alphametal). It was dried at 100° C. and then placed in a perfluorinated butylene vapor zone. Exposure to this vapor for 30 seconds resulted in virtually no removal of flux from the slides. Example 6: Trial Soldering of Electrical Elements Using Perfluorinated Hebuta Glyme The evaporator tank was dripped with perfluorinated butylene to its normal working level. After reaching controlled reflux conditions, the circuit board with three integrated circuits was lowered into the vapor zone for 25 seconds. The following chips are soldered to a satisfactory condition. (1) Chip with 12 connection terminals inserted into a tin-lead all-plated plate with 60/40 Sn/Pb solder. (2) Surface mounting of 14 connection terminals with gal connection terminals was placed on the chip, surface mounting with 60/40 Sn/Pb solder was placed on the board. (3) Side mounting had connection terminals; surface mounting with 18 connection terminals placed the chip; surface mounting with 6 0/40 Sn/Pb solder placed on the board. Equivalent Methods Those skilled in the art will recognize many methods that are equivalent to the specific embodiments of the invention described herein. and could be confirmed without the use of anything more than routine experimentation. Equivalent methods of this kind are intended to be covered by the following claims. It is intended that National RSM inspection report International search report US 8904258 S^ 31569

Claims (5)

[Claims] 1. The element and solder are immersed in a steam bath containing perfluoroheptaglyme. melting the solder and removing the soldered elements from the steam bath. How to solder elements. 2. The method of claim 1, wherein the solder has a melting point of 200°C or less. 3. 3. The method of claim 2, wherein said solder is a 60/40 tin/lead solder. 4. 2. The method of claim 1, wherein said element is an electrical element. 5. Use of barfluoroheptaglyme as a vapor phase soldering fluid.