JP4609347B2 - Solder flux and solder paste using the flux - Google Patents

Description

  The present invention relates to a solder flux with little residue after soldering and a solder paste using the flux.

  The solder paste used in the conventional reflow soldering method contains solder fine particles, rosin, a solvent, an activator, and the like. However, in the conventional reflow soldering method using a solder paste, a large amount of the rosin component remains as a flux residue in the soldered portion after reflow, and thus it is necessary to clean and remove this flux residue with a cleaning liquid. In general, the cleaning liquid was cleaned with an alcohol or glycol solvent.

  Recently, however, it has become difficult to clean and remove the residue sufficiently as the density of electronic components is increased, and there is a movement to omit the cleaning step with a solvent due to a decrease in mounting cost and environmental load. Since it is becoming active, there is a demand for a residue-free solder paste that does not require cleaning after reflow, and research and development is ongoing. Specifically, measurement by a thermal gravimeter method including an organic substance having at least two hydroxyl functional groups per molecule, an air or nitrogen gas atmosphere flow rate of 200 ml / min, and a temperature increase rate of 10 ° C./min. Thus, when the mass% becomes approximately 0%, the soldering flux having a temperature of approximately 170 ° C. or higher and the solder solidus temperature or higher, solder powder, and at least a hydroxyl functional group in one molecule When three masses of organic substances are contained, the air flow rate is 200 ml / min, and the temperature rise rate is 10 ° C./min. A solder paste composed of a solvent having a temperature of approximately 235 ° C. or higher and a solder solidus temperature or higher has been proposed (for example, see Patent Document 1). By using the soldering flux and the solder paste shown in Patent Document 1, at the temperature at which the solder starts to melt, it is present in a liquid state in the solder portion without being decomposed or evaporated, and a wet state can be realized, and At the end of the soldering process, it is possible to perform soldering in which no residue is generated by evaporation or decomposition / evaporation of all the flux. Therefore, there is no need for post-cleaning.

Moreover, it is a solder paste for reflow soldering in which powder solder and paste-like flux are mixed, and the flux is reflowed with at least one solid solvent that is solid at normal temperature and evaporates at reflow temperature, and a highly viscous fluid at normal temperature. There has been proposed a residue-free solder paste containing at least one high-viscosity solvent that evaporates at a temperature and at least one liquid solvent that is a liquid at room temperature and evaporates at a reflow temperature (see, for example, Patent Document 2). ). In this Patent Document 2, it is possible to impart optimum flow characteristics to the flux without containing rosin, and in spite of being no residue, and the parts retention, storage stability, printability, dischargeability, and It has good wettability and can ensure resin adhesion without washing after reflow soldering.
JP-A-9-94691 (Claims 1, 10, paragraphs [0009] and [0100]) JP 2004-25305 A (Claim 1, paragraph [0016])

However, in order to further improve the continuous printability of the solder paste disclosed in Patent Document 1, it is conceivable to add a viscous component. There is a problem that the quality deteriorates. As a measure for preventing deterioration of wettability by adding a viscous component, wettability can be improved by adding a small amount of an activator. However, when a halogen-based material or an amine-based material is added as an activator, the insulation reliability deteriorates. Further, even if an evaporative material is selected as the activator, the reaction product reduces the insulation reliability, and therefore, it is necessary to select an appropriate activator in order to improve the continuous printability.
Moreover, in the solder paste shown by the said patent document 2, the viscosity of a flux can be improved by including a solid solvent like 2,5-dimethylhexane-2,5-diol in a flux, Even if this solid solvent is added, the necessary and sufficient adhesiveness as a flux cannot be obtained. Therefore, the addition of a high-viscosity solvent such as isobornylcyclohexanol has made the viscosity appear. However, sufficient viscosity was not obtained. Moreover, in the said patent document 2, although amine salt is added as an activator, since it will lead to the fall of insulation reliability, adding such a substance has been a problem.

An object of the present invention is to provide a soldering flux having good wettability and less residue after completion of soldering, and a solder paste using the flux.
Another object of the present invention is to provide a soldering flux that does not require a cleaning step after completion of soldering and a solder paste using the flux.

Invention, reducing solid active agent comprising a saccharide having 4-6 hydroxyl groups, consists of a compound having an isobornyl group, and a highly viscous solvent viscosity at 30 ° C. exhibits 10Pa · s~100Pa · s according to claim 1 Each contains a low viscosity solvent having a viscosity at 30 ° C. of 1 mmPa · s to 500 mmPa · s, and each content of the reducing solid activator, the high viscosity solvent and the low viscosity solvent is a reducing solid activator: High viscosity solvent: Low viscosity solvent = 10 to 40% by weight: 20 to 40% by weight: 10 to 50% by weight In a range of 10 to 50% by weight , the solder flux is characterized by being blended so as to satisfy the total amount of 100% by weight. It is.
In the invention according to claim 1, in addition to the generally low viscosity solvents used, in combination with both a high viscosity solvent comprising a compound having a reducing solid active agent and an isobornyl group consisting of saccharides having 4-6 hydroxyl groups using By doing so, it is possible to impart optimum adhesive properties, wettability and thixotropy to the flux without using any rosin. Therefore, it is no longer necessary to add unnecessary components such as viscosity modifiers that have been added conventionally, and the residue after completion of soldering can be reduced without generating residues resulting from these components such as viscosity modifiers. Can do.

The invention according to claim 2 is the invention according to claim 1, wherein the saccharide comprises erythritol, fructose, galactose, glucose, mannose, sorbitol, lactose, sucrose, xylitol, hexitol, maltitol, lactitol, ribitol, and mannitol. It is a flux that is one kind of compound selected from the group or a mixture of two or more kinds.
In the invention according to claim 2, the above-listed compounds or mixtures can obtain an appropriate viscosity and exhibit good wettability. Moreover, since a boiling point suitable for the soldering flux is exhibited, the generation of residues can be reduced after the soldering is completed.

The invention according to claim 3 is the flux according to claim 1, wherein the compound having an isobornyl group contains either or both of isobornylcyclohexanol and isobornylphenol.
In the invention according to claim 3 , the compounds listed above can obtain appropriate tackiness. Moreover, since a boiling point suitable for the soldering flux is exhibited, the generation of residues can be reduced after the soldering is completed.

The invention according to claim 4 is the invention according to claim 1 , wherein the low- viscosity solvent contains one or more selected from the group consisting of alkanediol, alkylene glycol, hydrocarbon, terpene and ether. It is.
The invention according to claim 5 is the invention according to claim 4 , wherein the low viscosity solvent is 2-ethyl-1,3-hexanediol, 1,5-pentanediol, 1,4-butanediol, triethylene glycol. , Tetraethylene glycol, tetradecane, α-terpineol, dibenzyl ether, p-dodecylphenol, 2-nonylphenol, and 2-phenoxyethanol, or a flux containing one or more selected from the group consisting of 2-phenoxyethanol.
In the inventions according to claims 4 and 5 , the above listed compounds are suitable for adjusting the viscosity of the flux. Moreover, since a boiling point suitable for the soldering flux is exhibited, the generation of residues can be reduced after the soldering is completed.

The invention according to claim 6 is the invention according to any one of claims 1 to 5 , further comprising a thixotropic agent together with the reducing solid activator, the high viscosity solvent and the low viscosity solvent , and the reducing solid activator. The contents of the high-viscosity solvent, the low-viscosity solvent and the thixotropic agent are as follows: reducing solid activator: high-viscosity solvent: low-viscosity solvent: thixotropic agent = 10 to 40% by weight: 20 to 40% by weight: 10 ˜50 wt%: A flux that is blended so as to satisfy the total amount of 100 wt% within the range of 5 to 20 wt% .
In the invention according to claim 6 , a thixotropic agent may be further included within the above range in accordance with its use.
The invention according to claim 7 is the flux according to claim 6, wherein the thixotropic agent is a fatty acid amide.

The invention according to claim 8 is the flux according to any one of claims 1 to 7 , wherein the viscosity is 10 to 300 Pa · s.
In the invention which concerns on Claim 8 , the flux suitable for various uses is obtained by making the viscosity of a flux in the said range.

The invention according to claim 9 is a solder paste characterized by mixing the flux according to any one of claims 1 to 8 and solder powder.
In the invention according to claim 9 , the solder paste obtained by mixing the flux according to any one of claims 1 to 8 and the solder powder can obtain a viscosity suitable for printing, and its adhesiveness at the time of mounting. Therefore, the mounting component can be held at the same position. Further, since the flux itself has a viscosity, it is not necessary to add a viscous component such as a viscosity modifier, and the residue after the soldering can be reduced.

The invention according to claim 10 is the paste according to claim 9 , wherein the solder powder is a gold-tin alloy.
The invention according to claim 11 is the paste according to claim 9 , wherein the solder melting temperature is 350 ° C. or less.

The invention according to claim 12 is a method of manufacturing an electronic component using the paste according to any one of claims 9 to 11 .

Solder flux of the present invention, reducing solid active agent comprising a saccharide having 4-6 hydroxyl groups, consists of a compound having an isobornyl group, and a highly viscous solvent viscosity at 30 ° C. exhibits 10Pa · s~100Pa · s It is a flux characterized by containing a low-viscosity solvent having a viscosity of 1 mmPa · s to 500 mmPa · s at 30 ° C. at a predetermined ratio, and contains 4 to 6 hydroxyl groups in addition to the generally used low-viscosity solvent. By using a combination of a reducing solid activator composed of saccharides and a highly viscous solvent composed of a compound having an isobornyl group, it gives optimum adhesion characteristics and thixotropy to the flux without using any rosin. be able to. Therefore, it is no longer necessary to add unnecessary components such as viscosity modifiers that have been added conventionally, and the residue after completion of soldering can be reduced without generating residues resulting from these components such as viscosity modifiers. Can do.

Next, the best mode for carrying out the present invention will be described.
The solder flux of the present invention is characterized by containing a reducing solid activator containing a saccharide having 4 to 6 hydroxyl groups, a high-viscosity solvent containing a compound having an isobornyl group, and a low-viscosity solvent, respectively. In the present invention, the “high viscosity solvent” refers to a solvent having a viscosity at 30 ° C. of 10 Pa · s to 100 Pa · s, and the “low viscosity solvent” refers to a viscosity at 30 ° C. of 1 mmPa · s to 500 mmPa · s. Means something In addition to the commonly used low-viscosity solvents, the combination of both the reducing solid activator and the high-viscosity solvent makes it possible to achieve optimum adhesion characteristics, wettability and thixotropy for flux without using any rosin. Sex can be imparted. Therefore, it is no longer necessary to add unnecessary components such as viscosity modifiers that have been added conventionally, and the residue after completion of soldering can be reduced without generating residues resulting from these components such as viscosity modifiers. Can do. Moreover, since each component contained in the flux uses a component having a low boiling point, the flux component can be volatilized at a relatively low temperature, and when used as a solder paste, the volatile gas component is contained inside after melting the solder. It has the characteristic that the void which remains and becomes voids in the solder is reduced. Furthermore, since about 50% of the flux component is volatilized when the solder is melted and 100% is volatilized after the solder is melted, there is no residue resulting from the flux component, and no cleaning is required after the soldering is completed.

  A reducing solid activator containing a saccharide having 4 to 6 hydroxyl groups exhibits a reducing action similar to that of rosin during reflow soldering, so that the wettability of the flux can be improved. The saccharide contained in the reducing solid activator has 4 to 6 hydroxyl groups. When the number of hydroxyl groups is less than 4, the activity is insufficient, the wettability decreases, and the number of hydroxyl groups. If the number exceeds 6, the molecular weight increases, the boiling point of the compound becomes too high, and a residue is generated after the soldering is completed. Examples of the saccharide include one compound selected from the group consisting of erythritol, fructose, galactose, glucose, mannose, sorbitol, lactose, xylitol, hexitol, maltitol, lactitol, ribitol, and mannitol, or a mixture of two or more. Can be mentioned. Since the saccharides listed above have moderate thickening, they impart moderate tackiness and moderate thixotropy to the flux. Moreover, since a boiling point suitable as a soldering flux is shown, a residue can be reduced after soldering is completed. The content of the reducing solid activator in the flux is preferably 5 to 60% by weight, particularly preferably 10 to 40% by weight based on 100% by weight of the total amount. When the content of the reducing solid activator is less than 10% by weight, the activity is insufficient and the wettability is lowered. When the content of the reducing solid activator exceeds 60% by weight, the solder powder and the flux It is difficult to handle the paste after it is made into a paste, and since the reducing solid activator is a high boiling point material, a residue is generated after completion of soldering due to an excessive content ratio, and cleaning is necessary. Become. Appropriate wettability can be obtained by dispersing a reducing solid activator having a predetermined average particle size in a high-viscosity solvent and a low-viscosity solvent. The average particle size of the reducing solid activator is preferably from 0.1 to 200 μm, particularly preferably from 1 to 30 μm. If it is less than the lower limit, it will agglomerate in the high-viscosity solvent and the low-viscosity solvent, so that a residue may be generated after reflow. However, the problem which settles in a flux arises.

  The reason why the compound contained in the high-viscosity solvent has an isobornyl group is to provide appropriate tackiness in the flux due to the complicated three-dimensional structure of the isobornyl group. In addition, the compound having an isobornyl group has a high viscosity even though the volatilization temperature is equal to or lower than the solder melting temperature, so that a high flux viscosity can be realized. Examples of the compound having an isobornyl group include either or both of isobornylcyclohexanol and isobornylphenol. Since the above-listed compounds have moderate tackiness, they impart moderate tackiness to the flux. Moreover, since a boiling point suitable as a soldering flux is shown, a residue can be reduced after soldering is completed. The content of the highly viscous solvent in the flux is preferably 10 to 60% by weight, particularly preferably 20 to 40% by weight, based on 100% by weight of the total amount. When the content of the high viscosity solvent is less than 10% by weight, the flux cannot have an appropriate viscosity and tackiness. When the content of the high viscosity solvent exceeds 60% by weight, the flux has strong tackiness. For this reason, it tends to remain other than the portion applied at the time of applying the paste, it becomes difficult to handle, and loss of the paste material is likely to occur.

  The low-viscosity solvent is contained for the purpose of adjusting the viscosity so that proper flow characteristics can be obtained. The content of the low viscosity solvent is preferably 20 to 70% by weight, particularly preferably 20 to 50% by weight, based on 100% by weight of the total amount. Examples of the low viscosity solvent include one or more selected from the group consisting of alkanediol, alkylene glycol, hydrocarbon, terpene and ether. Among the above types, 2-ethyl-1,3-hexanediol, 1,5-pentanediol, 1,4-butanediol, triethylene glycol, tetraethylene glycol, tetradecane, α-terpineol, dibenzyl ether, p- Particularly preferred are dodecylphenol, 2-nonylphenol and 2-phenoxyethanol. The above-listed compounds are suitable for adjusting the viscosity of the flux. Moreover, since a boiling point suitable for the soldering flux is exhibited, the generation of residues can be reduced after the soldering is completed.

  In addition, by using a substance that can be volatilized at a lower temperature than the reducing solid activator as the high-viscosity solvent and low-viscosity solvent, when the solder paste using this flux is melted, the high-viscosity solvent and low-viscosity solvent are Since only the reducing solid activator that volatilizes before the reducing solid activator and develops wettability remains, the amount of gas generated when the solder melts can be suppressed, and the volatile gas that causes voids can be reduced. Become.

  The flux of the present invention may further contain a thixotropic agent in accordance with its use. In this case, the addition amount of the thixotropic agent is preferably 20% by weight or less, particularly preferably 5 to 20% by weight based on the total amount of 100% by weight. Examples of the thixotropic agent to be added include fatty acid amides. Specific examples of the fatty acid amide include stearic acid amide, palmitic acid amide, lauric acid amide, oleic acid amide, erucic acid amide and the like. Stearic acid amide is preferred because it has high stability and exhibits a more appropriate boiling point as a flux.

  The viscosity of the flux of the present invention is preferably 10 to 300 Pa · s, particularly preferably 30 to 250 Pa · s. By setting the viscosity of the flux within the above range, a flux suitable for various applications can be obtained. If the viscosity of the flux is less than the lower limit value, a problem occurs that the wettability is lowered. If the flux viscosity exceeds the upper limit value, the fluidity is inferior. If the flux of the present invention is within the above range, it is possible to easily adjust the viscosity by adjusting the content ratio, so that the flux can be used according to a construction method such as a printing method or a dispensing method. Specifically, 10 to 100 Pa · s is particularly preferable in the dispensing method, and 50 to 250 Pa · s is particularly preferable in the printing method.

  The solder paste of the present invention is characterized by mixing the above-mentioned flux and solder powder. The solder paste of the present invention obtained by mixing the above-mentioned flux and solder powder can obtain a viscosity suitable for printing, and can hold the mounted component in the same position because of its adhesiveness during mounting. Also, since no flux is used without using rosin at all, the residue after soldering is small. Since there is almost no residue, it does not require cleaning to remove the residue after reflow soldering, and it can also be used for soldering parts that were not compatible with wet cleaning that would increase dirt when cleaned. Can do. Further, the solder paste of the present invention can be used for soldering to an optical system component because a component that volatilizes during remelting is not observed.

  As the solder powder used for the solder paste, lead-free solder powder is selected, of which gold-tin alloy, tin-silver-copper alloy, tin-silver alloy, and tin-copper alloy are suitable. The gold-tin alloy refers to an alloy containing gold and tin as main components and the balance being composed of inevitable impurities, and the gold-tin alloy used in the present invention has a gold content of 70 to 85% by weight, An alloy containing a tin content of 15 to 30% by weight is preferred. The tin-silver-copper alloy refers to an alloy containing tin, silver and copper as main components, with the remainder being composed of inevitable compounds. The tin-silver-copper alloy used in the present invention has a tin content of 93 to 93. An alloy containing 94.8% by weight, a silver content of 0.1 to 5.0% by weight, and a copper content of 0.1 to 2.0% by weight is preferable. A specific example is Sn-3.0Ag-0.5Cu. The tin-silver alloy refers to an alloy containing tin and silver as main components and the balance being composed of inevitable compounds. The tin-silver alloy used in the present invention has a tin content of 95 to 99.9 wt. %, And an alloy with a silver content of 0.1 to 5.0% by weight is preferable. A specific example is Sn-3.5Ag. The tin-copper alloy refers to an alloy containing tin and copper as main components and the balance being composed of inevitable compounds. The tin-copper alloy used in the present invention has a tin content of 98 to 99.9 wt. %, An alloy with a copper content of 0.1 to 2.0% by weight is preferred. A specific example is Sn-0.7Cu. Moreover, it is preferable that a solder melting temperature is 350 degrees C or less, 200 to 350 degreeC is more preferable, and 240 to 320 degreeC is especially preferable. Since the paste suitable for various uses is obtained by making the viscosity of the solder paste of this invention into the range of 40-350 Pa.s, it is suitable. The solder paste of the present invention is particularly suitably used for joining Cu substrates or Cu substrates plated with Ni, Au or the like. Since the solder paste of the present invention has good wettability and a small amount of residue after completion of soldering, by producing an electronic component using this solder paste, it is possible to apply to the electronic component after completion of soldering which has been conventionally performed. A cleaning step is not necessary.

Next, embodiments of the present invention will be described in detail.
<Example 1>
Erythritol as a reducing solid activator, a mixed solvent prepared by mixing isobornylcyclohexanol and isobornylphenol at a ratio of 8: 2 as a high viscosity solvent, and tetraethylene glycol as a low viscosity solvent, respectively. Prepared.
First, the reducing solid activator is defoamed by mixing with a stirrer so that the total amount is 25% by weight, the low viscosity solvent is 40% by weight and the high viscosity solvent is 35% by weight. As a result, a flux was obtained in which the amount of reducing solid activator added was 25% by weight, the amount of highly viscous solvent added was 35% by weight, and the amount of low viscous solvent added was 40% by weight. It was 30 Pa.s when the viscosity at 25 degreeC was measured for the obtained flux with a viscometer (made by Rheometer TA Instruments).

<Example 2>
A mixed solvent prepared by mixing xylitol as a reducing solid activator, isobornylcyclohexanol and isobornylphenol as a high viscosity solvent in a ratio of 8: 2, and 2-ethyl-1 as a low viscosity solvent. , 3-hexanediol and stearamide as a thixotropic agent were prepared.
First, the thixotropic agent is mixed in the low-viscosity solvent in such a ratio that the low-viscosity solvent is 50% by weight of the total amount and the thixotropic agent is 10% of the total amount, and the resulting mixture is heated to about 100 ° C. Then, the thixotropic agent was dissolved in a low-viscosity solvent to obtain a thixotropic agent solution, and after dissolution, cooling was performed with stirring. Next, the reducing solid activator is mixed with a stirrer so that the total amount is 20% by weight, the thixotropic agent solution is 60% by weight and the high viscosity solvent is 20% by weight. By defoaming, the amount of reducing solid activator added is 20% by weight, the amount of highly viscous solvent added is 20% by weight, the amount of low viscous solvent added is 50% by weight, and the amount of thixotropic agent added is 10% by weight. A flux was obtained. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 20 Pa · s.

<Example 3>
Prepare sorbitol as the reducing solid activator, isobornylcyclohexanol as the high viscosity solvent, 2-ethyl-1,3-hexanediol as the low viscosity solvent, and erucamide as the thixotropic agent. Example 2 except that the addition amount of the activator was 25% by weight, the addition amount of the high viscosity solvent was 30% by weight, the addition amount of the low viscosity solvent was 35% by weight, and the addition amount of the thixotropic agent was 10% by weight. Thus, a flux for solder was obtained. It was 95 Pa.s when the viscosity at 25 degreeC was measured for the obtained flux with the viscometer.
<Example 4>
Ribitol as a reducing solid activator, a mixed solvent prepared by mixing isobornylcyclohexanol and isobornylphenol in a ratio of 8: 2 as a high viscosity solvent, tetraethylene glycol as a low viscosity solvent, Prepare oleic acid amide as a thixotropic agent, 25% by weight of reducing solid activator, 25% by weight of highly viscous solvent, 33% by weight of low viscous solvent, and thixotropic agent A solder flux was obtained in the same manner as in Example 2 except that the amount was changed to 17% by weight. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 120 Pa · s.
<Example 5>
Prepare erythritol as a reducing solid activator, isobornylcyclohexanol as a high viscosity solvent, α-terpineol as a low viscosity solvent, and stearamide as a thixotropic agent, and the amount of reducing solid activator added is 40. A solder flux was obtained in the same manner as in Example 2 except that the addition amount of the high-viscosity solvent was 40 wt%, the addition amount of the low-viscosity solvent was 10 wt%, and the addition amount of the thixotropic agent was 10 wt%. It was. It was 185 Pa.s when the viscosity at 25 degreeC was measured for the obtained flux with the viscometer.

<Example 6>
Xylitol as a reducing solid activator, a mixed solvent prepared by mixing isobornylcyclohexanol and isobornylphenol at a ratio of 8: 2 as a high viscosity solvent, and p-dodecylphenol as a low viscosity solvent. , Stearamide as a thixo agent, 30% by weight of the reducing solid activator, 40% by weight of the high viscosity solvent, 25% by weight of the low viscosity solvent, A solder flux was obtained in the same manner as in Example 2 except that the addition amount was 5% by weight. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 70 Pa · s.
<Example 7>
Prepare erythritol as the reducing solid activator, isobornylcyclohexanol as the high viscosity solvent, 1,5-pentanediol as the low viscosity solvent, and palmitic acid amide as the thixotropic agent, and add the reducing solid activator. For soldering in the same manner as in Example 2 except that the amount was 20% by weight, the amount of high viscosity solvent was 40% by weight, the amount of low viscosity solvent was 30% by weight, and the amount of thixotropic agent was 10% by weight. A flux was obtained. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 85 Pa · s.

<Comparative Example 1>
65% by weight of polymerized rosin, 7% by weight of hydrogenated castor oil, 2% by weight of diethylamine hydrochloride and 26% by weight of 2-ethyl-1,3-hexanediol were mixed to obtain a rosin flux. It was. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 115 Pa · s.
<Comparative Example 2>
30% by weight of polymerized rosin, 30% by weight of trimethylolpropane, 6% by weight of hydrogenated castor oil, 0.2% by weight of diphenylguanidine, and 33.8% by weight of 2-ethyl-1,3-hexanediol To obtain a low residue flux. When the viscosity at 25 ° C. of the obtained flux was measured with a viscometer, it was 85 Pa · s.

<Comparison test 1>
As a solder powder, a gold-tin alloy powder containing tin and gold as main components and a tin content of 20% by weight was prepared. This gold-tin alloy powder has an average particle size of 15 to 50 μm. A tin-silver-copper alloy powder containing tin, silver and copper as main components, tin content of 96.5% by weight, silver content of 3% by weight and copper content of 0.5% by weight was prepared. This tin silver copper alloy powder has an average particle diameter of 5 to 15 μm. The fluxes produced in each of Examples 1 to 5 and Comparative Example 2 were mixed with gold-tin alloy powder so that the flux content was 10% by weight with respect to 100% by weight of the total paste. Further, the fluxes prepared in Examples 6 and 7 and Comparative Example 1 were mixed with tin silver copper alloy powder so that the content ratio of the flux was 10% by weight with respect to 100% by weight of the total paste. Next, by carefully stirring the alloy powder in the mixture so as not to remain as a lump, a solder paste having a flux content of 10% by weight was obtained. When the viscosity at 25 ° C. of the obtained solder paste was measured with a viscometer, the paste using the flux of Example 1 was 65 Pa · s, the paste using the flux of Example 2 was 40 Pa · s, and the paste of Example 3 was used. The paste using the flux is 130 Pa · s, the paste using the flux of Example 4 is 145 Pa · s, the paste using the flux of Example 5 is 210 Pa · s, and the paste using the flux of Example 6 is 150 Pa · s. s, the paste using the flux of Example 7 was 180 Pa · s. The paste using the flux of Comparative Example 1 was 220 Pa · s, and the paste using the flux of Comparative Example 2 was 180 Pa · s.

  Subsequently, an evaluation test was performed as shown below using the obtained solder paste. First, two hot plates were installed in a glove box in which nitrogen was flowed at a rate of about 5 L / min and the oxygen concentration of the internal atmosphere was controlled to 100 ppm or less. One of these two hot plates is used for preheating used to increase the activity of the flux, and the other is used for melting the alloy powder and completely volatilizing the flux so that the components of the flux do not remain as residues. This is for the main heating used. Next, a Cu substrate having a surface plated with Au is prepared, and this substrate is covered with a metal mask having a thickness of 0.2 mm and having a plurality of communication holes of different sizes from 200 μmφ to 2 mmφ. After applying a predetermined amount of solder paste on the board, slide the squeegee on the metal mask to fill the solder paste in the multiple communication holes, and then remove the metal mask from the board to screen-print the board. did. The surface of the substrate after screen printing is visually observed using a stereomicroscope and a low-magnification camera, and the paste filling property, rolling property (sliding property) on the substrate surface, detachability from the metal mask used as a plate, Each sagging property was evaluated. The specific evaluation of the paste filling property is evaluated as “excellent” when the paste is filled in all the communicating holes and the filling amount is satisfactory, and the paste is filled in all the communicating holes. When there is little, it is evaluated as “good”, and the communication hole with a large diameter is filled with paste, but when the paste with a small diameter is not filled with paste, it is evaluated as “good”. When the shape of the partially filled paste was deformed, the evaluation was “impossible”. The specific evaluation of rolling property (slidability) is “excellent” when the rotation of the paste inside the squeegee is smooth, and “good” when the rotation of the paste inside the squeegee is observed. The evaluation was “Yes” when the rotation of the paste inside the squeegee was slow or slow, and “No” was evaluated when the rotation of the paste was not observed inside the squeegee. In addition, the specific evaluation of the detachability from the metal mask used as the plate is evaluated as “excellent” when no paste remains on the metal mask, and as “good” when slightly left on the edge of the metal mask, The shape was once deformed by being pulled up by the metal mask, but when the shape was restored thereafter, the evaluation was “Yes”, and when the shape was still deformed by being pulled up by the metal mask, the evaluation was “No”. Furthermore, the specific evaluation of the sagging property of the paste is “excellent” when the printed solder interval can be printed up to 200 μm. When the printed solder interval is 200 μm, the sag occurs and the solder is It is evaluated as “good” when contacted, and printing is possible up to a printed solder interval of up to 300 μm. However, it is evaluated as “good” when solder contacts with each other at intervals smaller than 300 μm, and the printed solder interval is Printing was possible up to 400 μm, but “impossible” was evaluated when the solders contacted each other at an interval narrower than 400 μm.

  Next, a substrate on which a paste is printed is placed on a preheating hot plate heated to 150 ° C. to 152 ° C., preheated for 30 to 60 seconds, and then the substrate is heated to 320 ° C. to 322 ° C. It was placed on a heating hot plate and subjected to main heating for 30 to 90 seconds. After visually confirming the molten state of the solder applied on the substrate, the substrate was lowered from the main heating hot plate and cooled to room temperature. The substrate surface after cooling was visually observed for wettability and residue on the substrate surface using a stereomicroscope and a low magnification camera. The wettability was observed by confirming whether there was any undissolved residue by visual inspection and by changing the size before and after melting the solder. Specifically, when the area at the beginning of application is 100%, the area after melting is expressed as a percentage. When the area after melting is 150% or more, the evaluation is “excellent”, and the area after melting is 120. The evaluation was “good” when the percentage was not less than 150% and less than 150%, and the evaluation was “good” when the area after melting was not less than 100% and less than 120%. Residual properties were observed visually by using a stereomicroscope and a low magnification camera. Specifically, it is evaluated as “excellent” when there is no or almost no flux residue, and it is evaluated as “good” when a small amount of colorless or light yellow flux residue is observed. When a small amount of residue was observed, the evaluation was “Yes”, and when a large amount of gray or black residue was observed, the evaluation was “Not possible”. Table 1 shows the blending ratio of the fluxes produced in Examples 1 to 7, and Table 2 shows the results of evaluation tests of solder pastes using the fluxes of Examples 1 to 7 and Comparative Examples 1 and 2, respectively.

As is clear from Table 2, Comparative Examples 1 and 2 were inferior in evaluation of residue properties, and a large amount of residue was generated. In this case, it is necessary to wash after reflow. On the other hand, in Examples 1 to 7 of the present invention, all the evaluation items have a performance that can be practically used, and the evaluation of the residual property is high, so that it is not necessary to perform cleaning.

Claims (12)

Reducing solid active agent comprising a saccharide having 4-6 hydroxyl groups, consists of a compound having an isobornyl group, highly viscous solvent and 30 viscosity at ° C. is 1mmPa · s viscosity at 30 ° C. exhibits 10Pa · s~100Pa · s Each containing a low-viscosity solvent exhibiting ~ 500 mmPa · s ,
Reducing solid activator: high viscosity solvent: low viscosity solvent = 10-40 wt%: 20-40 wt%: 10 A soldering flux characterized by being blended so as to satisfy a total amount of 100% by weight within a range of 50% by weight . The saccharide is one compound selected from the group consisting of erythritol, fructose, galactose, glucose, mannose, sorbitol, lactose, xylitol, hexitol, maltitol, lactitol, ribitol and mannitol, or a mixture of two or more. Item 3. The flux according to item 1 .   The flux according to claim 1, wherein the compound having an isobornyl group is either or both of isobornylcyclohexanol and isobornylphenol. The flux according to claim 1, wherein the low viscosity solvent contains one or more selected from the group consisting of alkanediol, alkylene glycol, hydrocarbon, terpene and ether. Low-viscosity solvent is 2-ethyl-1,3-hexanediol, 1,5-pentanediol, 1,4-butanediol, triethylene glycol, tetraethylene glycol, tetradecane, α-terpineol, dibenzyl ether, p-dodecyl The flux according to claim 4 , comprising one or more selected from the group consisting of phenol, 2-nonylphenol and 2-phenoxyethanol. A thixotropic agent together with a reducing solid activator, a high viscosity solvent and a low viscosity solvent ,
The contents of the reducing solid activator, the high viscosity solvent, the low viscosity solvent and the thixotropic agent are as follows: reducing solid active agent: high viscosity solvent: low viscosity solvent: thixotropic agent = 10 to 40% by weight: 20 The flux according to any one of claims 1 to 5, which is blended so as to satisfy a total amount of 100% by weight within a range of -40% by weight: 10-50% by weight: 5-20% by weight .   The flux according to claim 6, wherein the thixotropic agent is a fatty acid amide. The flux according to any one of claims 1 to 7 , which has a viscosity of 10 to 300 Pa · s. A solder paste comprising the flux according to any one of claims 1 to 8 and a solder powder mixed therein. The paste according to claim 9 , wherein the solder powder is a gold-tin alloy. The paste according to claim 9 , wherein the solder melting temperature is 350 ° C. or less. The method to manufacture an electronic component using the paste of any one of Claims 9 thru | or 11 .