JP2004098118A - Solder powder and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide solder powder which exhibits excellent packing properties into an organic component which serves as a vehicle in production of solder paste even when the solder powder consists of fine particles, and to provide its production method. <P>SOLUTION: The molten metal 11 of solder introduced from a molten metal nozzle 13 into a nozzle body 16 is atomized by an atomizing gas 14 injected under a pressure of 0.5 to 3 MPa from gas nozzle pores 15 of the nozzle body 16 set annularly around the outlet of the molten metal nozzle 13. Further, the atomizing gas 14 is circulated at a solder feed amount of 2 to 30 Nm<SP>3</SP>/kg, so that the solder powder having a mean particle diameter of 1 to 15 μm and a tap density of 3.5 to 6 g/cm<SP>3</SP>is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【００４５】
「表１」からもわかるように、実施例１〜３のはんだ粉は平均粒径が１〜１５μｍであり、かつタップ密度が３．５〜６ｇ／ｃｍ^３であり、本発明が目的とする、微細でありながら、充填性に優れたものであった。
【００４６】
これに対し、比較例１のはんだ粉は、アトマイズガス圧力が低いことに起因して、平均粒径が大きく、本発明が目的とする微細なはんだ粉とは言い難かった。
【００４７】
また、比較例２のはんだ粉は、はんだ供給量に対する循環ガス量が少なすぎて、凝集粉や粗粒粉が多く発生し、その結果、タップ密度が低いものであった。
【００４８】
また、比較例３のはんだ粉は、はんだ供給量に対する循環ガス量が多すぎて、変形粉や微粒粉が多く発生し、その結果、タップ密度が低いものであった。
【００４９】
【発明の効果】
本発明のはんだ粉は、微細なはんだ粉でありながら、はんだペーストを製造する際に、ビヒクルとなる有機成分中への充填性に優れており、ファインピッチソルダリング技術の要求を十分満足するものである。また、本発明のはんだ粉の製造方法によれば、上記はんだ粉を効率良く生産することが出来る。
【図面の簡単な説明】
【図１】本実施の形態にかかるガスアトマイズ装置の概略構成図である。
【図２】本実施の形態にかかるガスアトマイズシステムの概略構成図である。
【符号の説明】
１０　ガスアトマイズ装置
１１　はんだ溶湯
１２　はんだ溶湯保持槽
１３　溶湯ノズル
１４　アトマイズガス
１５　供給孔
１６　ノズル本体
１７　冷却チャンバー
２１　循環ライン
２２　第１サイクロン
２３　第２サイクロン
２４　バグフィルタ
２５　循環ファン
２６　滴下用ルツボ炉
２７　アトマイズガス発生装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solder powder used for a solder paste for mounting electronic components, particularly to a solder powder suitable for fine pitch mounting and a method for producing the same.
[0002]
[Prior art]
In recent years, with the spread of small and lightweight devices such as OA devices and portable communication devices, electronic circuits incorporated therein have been reduced in size and density, and mounting technology for mounting various components on a circuit board has become important. It has become to. In particular, there is a growing demand for fine pitch soldering technology, which has become a central component of mounting technology, and the average particle size of solder powder for general-purpose solder paste is generally 20 to 50 μm. It has shifted to the fine particle side, and the demand for finer solder powder tends to increase.
[0003]
Conventionally, many solder powders have been manufactured by a disk atomizing method or a gas atomizing method. However, in these methods, only the general-purpose solder particles having a large average particle diameter can be obtained, and the solder particles having a large average particle diameter can be obtained. Even if the powder was classified, only a small amount of the desired fine solder powder was obtained. Therefore, there is a need for a technique for efficiently producing solder powder having a smaller average particle size in order to obtain the desired fine solder powder.
[0004]
In response to such demands, in the gas atomization method, a method of producing fine metal powder by a so-called high-pressure gas atomization method for increasing a gas pressure to be introduced has attracted attention. For example, Non-Patent Document 1 below describes that a copper powder having a median size of 15 μm can be obtained at a gas pressure of 4.5 MPa, and a fine metal powder can be obtained by increasing the gas pressure. It is disclosed.
[0005]
On the other hand, when a solder paste is produced using fine solder powder, the filling property into an organic component serving as a vehicle is important. The reason is that as the particle size of the solder powder particles becomes finer, the tap density tends to become smaller.Therefore, even in fine pitch soldering, a paste containing a larger amount of solder powder in a smaller amount of paste is preferred. Needless to say, this is preferable.
[0006]
[Non-patent document 1]
"Fine Powders: the heat is on at PSI," Metal Powder Report, March 2001 issue.
[Problems to be solved by the invention]
As described above, fine solder powder is considered to be obtained by employing the high-pressure gas atomization method. In addition, fine solder powder having a high filling property is still obtained with satisfactory quality. Absent.
[0008]
It is an object of the present invention to provide a solder powder which is a fine solder powder and which has an excellent filling property in an organic component serving as a vehicle when a solder paste is produced, and a method for producing the same.
[0009]
[Means for Solving the Problems]
The present inventors have made intensive research efforts and have found that a solder powder having fine and specific filling characteristics can solve the above-mentioned problems, and completed the present invention.
[0010]
A first invention based on this finding provides a solder powder characterized by having an average particle diameter of 1 to 15 μm, a tap density of 3.5 to 6 g / cm ³ , and being produced by a gas atomization method. is there.
[0011]
A second invention is a method for producing a solder powder by a gas atomizing method, in which a molten solder flowing from a molten solder holding tank is rapidly solidified.
Introducing an inert gas as an atomizing gas at a pressure of 0.5 to 3 MPa, and circulating a gas used for atomizing and cooling at a solder supply amount of 2 to 30 Nm ³ / kg and a method for producing a solder powder. It is in.
[0012]
A third invention is the method for producing solder powder according to the second invention, wherein the temperature in the cooling chamber is controlled at 20 to 80 ° C.
[0013]
A fourth invention is the method for producing solder powder according to the second or third invention, wherein two or more centrifugal force dust collectors are installed in a gas circulation system connected to the cooling chamber.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a method for manufacturing a solder powder according to the present invention will be described, but the embodiment does not limit the present invention.
[0015]
The solder powder in the present invention has an average particle size of 1 to 15 μm, a tap density of 3.5 to 6 g / cm ³ , and is manufactured by a gas atomizing method.
According to this solder powder, even though it is a fine solder powder having an average particle size of 1 to 15 μm, it is excellent in filling property into an organic component serving as a vehicle when manufacturing a solder paste.
[0016]
Various solder alloys can be used as the alloy composition of the solder powder in the present invention.
As a specific alloy composition, including tin and lead alloys, particularly eutectic solder alloys, tin was combined with one or more of silver, copper, zinc, bismuth, indium, and antimony elements. Lead-free solder alloys.
[0017]
The average particle size of the solder powder of the present invention is preferably 1 to 15 μm.
If the average particle diameter is more than 15 μm, it is not suitable for use in fine pitch soldering, which is not preferable. On the other hand, if the average particle diameter is less than 1 μm, it is difficult to produce by the high-pressure gas atomizing method. In addition, it is also a problem in other characteristics such as oxidation resistance.
[0018]
The tap density of the solder powder of the present invention is preferably 3.5 to 6 g / cm ³ .
This is because when the tap density is less than 3.5 g / cm ³ , the filling property into the paste vehicle is inferior, so that it is not preferable. In the case of fine solder powder as in the present invention, it is difficult to set the tap density to 6 g / cm ³ .
Furthermore, the tap density is more preferably 4 to 5 g / cm ³ in consideration of the fact that it is possible to prevent the aggregation of particles accompanying the high filling property and to maintain the optimum state that does not hinder the filling property after pasting. preferable.
[0019]
Further, the solder powder of the present invention is manufactured by a gas atomization method, and it is considered difficult to obtain a solder powder by other manufacturing methods, including industrial productivity and efficiency.
[0020]
Next, the production method of the present invention will be described.
[0021]
The method for producing a solder powder according to the present invention is a method for producing a solder powder by a gas atomizing method, in which a molten solder flowing from a molten solder holding tank is rapidly solidified by a gas atomizing method, wherein an inert gas is atomized at a pressure of 0.5 to 3 MPa. The gas introduced and atomized and used for cooling is circulated at a flow rate of 2 to 30 Nm ³ / kg-solder.
[0022]
In the production method of the present invention, a gas atomizing method of rapidly cooling and solidifying the molten solder flowing down from the molten solder holding tank is employed. In particular, it is possible to introduce an inert gas at a pressure of 0.5 to 3 MPa as an atomizing gas. is important.
[0023]
As a device that actually performs the gas atomizing method, for example, a general-purpose gas atomizing device equipped with a confined nozzle or the like as shown in FIG. 1 can be used.
As shown in FIG. 1, a gas atomizing apparatus 10 includes a solder molten metal holding tank 12 for holding a molten solder 11, a molten metal nozzle 13 for flowing the molten molten metal 11, and an atomizing gas for rapidly cooling the molten solder 11 flowing from the molten metal nozzle 13. It comprises a nozzle body 16 having a supply hole 15 for supplying 14 and a cooling chamber 17 for cooling the solder powder obtained by atomization.
[0024]
FIG. 2 shows a gas atomizing apparatus 10 provided with a circulation line 21 for once discharging the atomizing gas 14 to the outside and recirculating the atomizing gas 14, the first and second cyclones 22, 23, and a bug for removing fine particles in the gas. The filter 24 and the circulation fan 25 are interposed.
In FIG. 2, reference numeral 26 denotes a dripping crucible furnace, and reference numeral 27 denotes an atomizing gas generator.
[0025]
Taking the case of using a gas atomizing device equipped with this confined nozzle as an example, in FIG. 1, the molten solder 11 introduced into the nozzle body 16 from the molten metal nozzle 13 is installed in a ring around the molten metal nozzle 13 outlet. It is atomized by the atomizing gas 14 ejected from the gas nozzle hole 15 of the nozzle body 16.
[0026]
In the present invention, the atomizing gas used for the atomizing is an inert gas, for example, a nitrogen gas, a helium gas, an argon gas or the like can be used. However, from the viewpoint of cost, the use of a nitrogen gas is preferable.
In addition, when a reactive gas is used as the atomizing gas, particularly when an oxidizing gas such as air is used, the oxygen concentration of the solder powder increases, which is not preferable. Note that there is no need to use a reducing gas.
[0027]
In the present invention, it is preferable to introduce the atomizing gas at a pressure of 0.5 to 3 MPa.
This is because when the pressure is less than 0.5 MPa, it is difficult to efficiently produce the desired fine solder powder, while when the pressure is more than 3 MPa, the liquefaction and condensation of the gas are difficult. This is because it is not preferable because the particle size of the solder powder varies due to generation or the like.
[0028]
Further, in the gas atomizing system according to the present embodiment, as shown in FIG. 2, it is also important that the atomizing gas used for cooling is circulated in the circulation line 21.
That is, the solder powder 20 atomized by the atomizing gas settles while receiving a cooling action in the chamber 17, while the gas in the chamber is recirculated in order to be reused as a new cooling gas. ing.
Alternatively, a gas is once extracted from the chamber for the purpose of separating the solder powder having a particle size outside the target size, and recirculation is performed in order to reduce the concentration of the solder powder particles in the chamber.
[0029]
In the present invention, by specifying the amount of the circulating gas, it is possible to efficiently obtain a solder powder having a high filling property.
That is, by circulating a specific circulating gas amount per unit time and solder supply amount, it is possible to obtain a solder powder having an optimum fine average particle size and a high filling property.
Specifically, it is necessary to circulate the circulating gas at a flow rate of 2 to ³⁰ Nm ³ / kg · solder supply amount.
[0030]
Here, when the circulating gas amount is less than 2 Nm ³ / kg · solder supply amount, the circulating gas amount is insufficient with respect to the amount of the atomized solder powder, so that the solder powder particle concentration in the chamber is high. It is not preferable because agglomeration powder or coarse powder is generated, which impairs the filling property of the solder powder.
When the circulating gas amount exceeds 30 Nm ³ / kg · solder supply amount, the solder powder receives an external force such as friction in the circulation path, and deformation or partial atomization occurs, thereby lowering the tap density. There is a possibility that it is not preferable.
[0031]
Further, in consideration of further increasing the productivity of the solder powder having less shape defects, it is more preferable that the circulating gas amount is ^{3 to} 10 Nm ³ / kg · the solder supply amount.
[0032]
In the present invention, it is preferable to control the temperature in the cooling chamber 17 to 20 to 80 ° C. because the properties of the solder powder are stable.
Here, if the temperature is lower than 20 ° C., the cost increases due to atomizing gas and excessive cooling, which is uneconomical and not preferable. It is not preferred because irregular powders are likely to be generated due to such factors.
[0033]
Further, in the present invention, the circulation line 21 of the gas circulation system connected to the cooling chamber is provided with two or more centrifugal dust collectors, so that solder powder having a desired average particle diameter can be collected. preferable.
It is common to install a centrifugal dust collector such as a cyclone in a circulation system in an atomizing device, but in a single-stage installation, solder powder near the target average particle diameter in a separation tank is used. This is because the fine particles are discharged together with the circulating gas together with the finer solder powder, and even if they are collected later by classification, quantitative complexity is inevitable.
[0034]
Further, in the present invention, if the gas replacement time in the chamber, expressed as chamber volume / circulating gas amount, is 0.5 to 1.6 minutes, the target solder can be efficiently produced without excessive circulation. Powder recovery is possible and more preferred.
[0035]
【Example】
Hereinafter, the effects of the present invention will be described with reference to examples.
[0036]
[Examples 1 to 3]
4.825 kg of tin ingot (grade 99.5% by mass) and 0.175 kg of silver ingot (grade 99.99% by mass) were weighed, put into a crucible furnace, and melted by heating. The molten metal is transferred to another crucible furnace for dropping, and while maintaining the temperature at about 480 ° C., the opening / closing valve inserted in the small hole at the bottom of the crucible for dropping is opened, the nitrogen regulating valve is opened, and atomization is performed. Started.
In the atomizing chamber (0.4 m ³ ), nitrogen gas was previously introduced at 1 Nm ³ / minute, and at the same time, the atomizing gas was circulated by a gas circulation fan.
Atomization was continued until there was no molten metal in the dropping furnace.
[0037]
About the obtained atomized powder, the average particle diameter and the tap density were measured by the following methods.
Here, the average particle size was measured using a particle size distribution analyzer Microtrac FRA type (manufactured by Nikkiso Co., Ltd.).
The tap density was measured using a powder tester PT-E type (manufactured by Hosokawa Micron).
[0038]
[Example 1]
The atomizing gas pressure was 2.0 MPa, the atomizing gas flow rate was 1.0 Nm ³ / min, the circulating gas amount was 6.4 Nm ³ / min, the molten solder supply amount was 0.45 kg / min, and the chamber temperature was 43 mm. ° C.
The replacement of the gas in the chamber required 0.06 minutes.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0039]
[Example 2]
The atomizing gas pressure was 2.8 MPa, the atomizing gas flow rate was 1.4 Nm ³ / min, the circulating gas amount was 10.2 Nm ³ / min, the molten solder supply amount was 0.51 kg / min, and the chamber temperature was 40 ° C. ° C.
The replacement of the gas in the chamber required 0.04 minutes.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0040]
[Example 3]
The atomizing gas pressure is set to 0.8 MPa, the atomizing gas flow rate is set to 0.4 Nm ³ / min, the circulating gas amount is set to 5.5 Nm ³ / min, the supply amount of the molten solder is set to 0.38 kg / min, and the temperature in the chamber is set to 47 mm. ° C.
It took 0.07 minutes to replace the gas in the chamber.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0041]
[Comparative Example 1]
The atomizing gas pressure was 0.3 MPa, the atomizing gas flow rate was 0.2 Nm ³ / min, the circulating gas amount was 6.0 Nm ³ / min, the molten solder supply amount was 0.44 kg / min, and the chamber temperature was 52 mm. ° C.
It took 0.07 minutes to replace the gas in the chamber.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0042]
[Comparative Example 2]
The atomizing gas pressure was 2.0 MPa, the atomizing gas flow rate was 1.0 Nm ³ / min, the circulating gas amount was 0.8 Nm ³ / min, the molten solder supply amount was 0.47 kg / min, and the temperature in the chamber was 43 mm. ° C.
The replacement of the gas in the chamber took 0.50 minutes.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0043]
[Comparative Example 3]
The atomizing gas pressure was 2.0 MPa, the atomizing gas flow rate was 1.0 Nm ³ / min, the circulating gas amount was 14.6 Nm ³ / min, the molten solder supply amount was 0.46 kg / min, and the chamber temperature was 41 ° C. ° C.
It took 0.03 minutes to replace the gas in the chamber.
An outline of the atomizing apparatus used is shown in FIG. 1, and the characteristics of the obtained solder powder are shown in "Table 1".
[0044]
[Table 1]

[0045]
As can be seen from Table 1, the solder powders of Examples 1 to 3 have an average particle size of 1 to 15 μm and a tap density of 3.5 to 6 g / cm ³ , which is an object of the present invention. Although it was fine, it was excellent in fillability.
[0046]
On the other hand, the solder powder of Comparative Example 1 had a large average particle size due to the low atomizing gas pressure, and was hardly a fine solder powder intended in the present invention.
[0047]
In the solder powder of Comparative Example 2, the amount of the circulating gas with respect to the supplied amount of the solder was too small, and a large amount of agglomerated powder and coarse powder was generated, and as a result, the tap density was low.
[0048]
In the solder powder of Comparative Example 3, the amount of the circulating gas with respect to the supplied amount of the solder was too large, and a large amount of deformed powder and fine powder was generated, and as a result, the tap density was low.
[0049]
【The invention's effect】
The solder powder of the present invention, while being a fine solder powder, has an excellent filling property in an organic component serving as a vehicle when producing a solder paste, and sufficiently satisfies the requirements of fine pitch soldering technology. It is. Further, according to the method for producing solder powder of the present invention, the above-mentioned solder powder can be efficiently produced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a gas atomizing device according to the present embodiment.
FIG. 2 is a schematic configuration diagram of a gas atomizing system according to the present embodiment.
[Explanation of symbols]
REFERENCE SIGNS LIST 10 Gas atomizing device 11 Solder melt 12 Solder melt holding tank 13 Melt nozzle 14 Atomizing gas 15 Supply hole 16 Nozzle body 17 Cooling chamber 21 Circulation line 22 First cyclone 23 Second cyclone 24 Bag filter 25 Circulating fan 26 Crucible furnace 27 for atomization 27 Atomize Gas generator

Claims (4)

A solder powder having an average particle size of 1 to 15 μm, a tap density of 3.5 to 6 g / cm ³ , and manufactured by a gas atomization method. A method for producing a solder powder by a gas atomizing method, which rapidly solidifies a molten solder flowing down from a molten solder holding tank,
Introducing an inert gas as an atomizing gas at a pressure of 0.5 to 3 MPa, and circulating a gas used for atomizing and cooling at a solder supply amount of 2 to 30 Nm ³ / kg and a method for producing a solder powder. . In claim 2,
A method for producing solder powder, comprising controlling the temperature in a cooling chamber to 20 to 80C. In claim 2 or 3,
A method for producing solder powder, comprising installing two or more centrifugal dust collectors in a gas circulation system connected to a cooling chamber.

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