JPH01139710A - Manufacture of fine granular alloy powder - Google Patents

Abstract

PURPOSE:To manufacture alloy powder containing the specific particle size of noble metal more than iron and a little impurities and oxide film by adding fine reduced iron powder into acidic salt mixed solution of metal containing two or more kinds of Sn, Pb, Cu, Ag and Pd. CONSTITUTION:The acidic salt mixed solution of chloride, sulfate, nitrate, etc., of two or more kinds of Sn, Pb, Cu, Ag and Pd is preparated. In this mixed solution, the reduced iron powder having 0.1-3.0mum particle size at the sufficient quantity to precipitate the whole of the component metal in the solution is added, heated, stirred to hold it. Successively, the alloy powder of Sn-Pd, etc., is developed and deposited after leaving as it is. By this method, the alloy powder having 0.1-3.0mum particle size and almost spherical shape can be manufactured without using any pulverizing machine.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is inexpensive and has less impurities and oxide film.
The present invention relates to a method for producing an alloy powder of a metal smaller than .mu.m in diameter than iron.

[Conventional technology and its problems]

Silver powder paste is widely used for printed wiring in the electronics industry. In recent years, with the miniaturization, precision, and high integration of electronic components, the width of print application has become significantly narrower, and the silver powder in the silver powder paste is required to be finer. In particular, silver paste consisting of a mixture of silver powder, vitreous binder powder, coating adhesive, and solvent has traditionally been used as a conductive paste for ICs, but with the miniaturization of ICs, pastes with a width of 10 μm or less have been used. In print coating, in order to form an uninterrupted fine line after baking the paste, the raw material silver powder must be as fine as possible, preferably 3 μm or less. Currently, silver powder with a particle size of 3 μm or less is produced and used, but when silver is pulverized, it becomes chemically active as the surface area of the powder increases, and its oxidation resistance deteriorates. For this reason, conductive pastes made of fine silver powder cannot avoid increasing their resistivity over time. For example, as a countermeasure, a method of mixing fine silver powder and fine palladium powder has been attempted. There is. However, when silver and palladium are in a powder state in which they are not alloyed with each other, the mixture does not exhibit a sufficient effect in preventing aging of the C performance.

The present inventor aimed to meet the demand for miniaturization of ICs.

The conductive powder for the conductive paste is a fine powder of 3 μm or less,
In addition, in order to improve corrosion resistance, it was thought that it was necessary not only to simply mix silver fine powder and palladium fine powder during paste processing, but also to alloy silver and palladium and obtain fine powder.

Copper-silver alloy powder having a particle size of 3 μm or less may also be used for similar purposes. At least the current 10μ
Copper-silver alloy powder, which is more resistant to oxidative deterioration, is more desirable than copper fine powder alone for printed coating wiring of about 500 yen. However, on the other hand, the silver fine powder currently used is 3 μm thick.
It is difficult to obtain inexpensive copper fine powder with a particle size of 3 μm or less.

This means that in conventional manufacturing methods, copper particles with a thickness of 3 μm or less
This means that silver alloy powders are even more difficult to manufacture.

Further, as ICs and LSIs become surface-mounted and substrates become more flexible, the use of solder pastes that allow wiring by printing and baking is increasing. In this field as well, the miniaturization of lead terminals is progressing with the miniaturization, precision, and high integration of electronic components, and the development of finer printing solder powder is desired.

[Focus on problem solving]

The present inventors have developed a 3 μm film that is inexpensive and has few impurities and oxide films.
As a result of repeated research on the manufacturing technology of the following fine-grained alloy powder,
- Iron powder with a particle size in the range of 0.1 μm to 3.0 μm is added to a mixed solution of two or more acidic salts of tin, lead, copper, silver, and palladium whose electric potential is more important than iron ions. By doing so, the secondary particle size is 0.1 μm, which is almost the same as iron powder.
The present invention was completed by discovering a phenomenon in which tin-lead, steel-silver, or silver-palladium alloy powders having a diameter of 3.0 μm can be precipitated by displacement.

[Structure of the invention]

The present invention provides a method for producing an alloy powder of a metal stronger than iron, which comprises adding fine reduced iron powder to a mixed solution of acid salts of component metals.

Specifically, the method of the present invention uses tin, lead, and copper.

A particle size of 0.1 to 3.0 consisting of two or more of silver and palladium.
A method for producing alloy powder in the range of 0 μm, comprising preparing a mixed solution containing acid salts of each component metal in the same equivalence relationship as the composition of the target alloy, and adding this solution to the total amount of the component metals present in the solution. 0.1 to 3.0 in an amount sufficient to precipitate
A method is provided comprising contacting with reduced iron powder of μm particle size.

That is, unlike conventional powder manufacturing methods, the present invention does not perform any mechanical pulverization, but merely uses a wet reaction that utilizes the ionization tendency of metals, and the primary particle size can be reduced from 0.1 μm to 3 μm.
Various alloy powders of m can be obtained.

The form, purity, and particle size of the iron powder used in the present invention greatly affect the form, purity, and particle size of the fine alloy powder produced, so iron oxide powder, ferrous sulfate powder, or ferrous chloride powder Fine reduced iron powder having a primary particle size of 0.1 μm to 3 μm, which is obtained by reducing iron powder with hydrogen gas, carbon monoxide, etc., is most preferable in terms of cost and purity.

As acidic salts of tin, lead, copper, silver and palladium, chlorides, sulfates and nitrates of these metals are common, with chlorides being most preferred. When creating these acidic salt aqueous solutions, there are three methods: ``dissolving commercially available chloride in water as it is'', ``reacting the oxide with hydrochloric acid etc. and dissolving it'', and ``anodic electrolysis in an aqueous solution such as hydrochloric acid''. Possible methods include ``dissolving method.'' When the above-mentioned reduced iron powder is dispersed into a slurry using an attritor or a sand mill using water as a solvent and added to an aqueous solution of these acid salt mixtures, fine grained alloy powder is formed and precipitated, and the solution becomes ferrous iron. It becomes an aqueous solution.

By dissolving an equivalent amount of iron, all of the component metals present in the solution that are more important than the iron precipitate out, so an alloy powder is formed in the same proportion as was initially present in the solution.

The resulting alloy is a mixture of components in a substantially microscopic state.

When iron powder of 3 μm or less is present in an amount less than the equivalent amount, the iron powder will not remain as a nucleus in the produced alloy powder.

A complexing agent may be added to control the precipitation rate of component metals.

In the displacement precipitation reaction of various fine-grained final alloy powders, the higher the bath temperature, the weaker the acid salt concentration, the faster the addition rate of iron powder, and the stronger the stirring, the more fine metal powder tends to precipitate by displacement. be. However, the larger the primary particle size of the iron powder used, the larger the particle size of the alloy powder that precipitates by displacement, and the slower the rate of displacement precipitation. The reason for this is
In principle, the same number of moles of metals as dissolved iron ions precipitate to form an alloy. This may be due to the fact that the dissolution rate is likely to decrease. In addition, reduced iron powder has a reduction rate of 80% when reduced at 380°C to 700°C in hydrogen gas using a rotary kiln etc.
~99% of Cf is used, and since it is handled in air, the surface is usually covered with a thin oxide film, and due to the slow start of the dissolution reaction, residual Cf1. The influence of acidic groups such as SO4 is large. Therefore, adding a small amount of hydrochloric acid or the like is effective in accelerating the dissolution reaction of iron powder. The alloy powder that precipitates basically depends on the form of the reduced iron powder. If the reduced iron powder is monodispersed one by one, the alloy powder produced will also be monodisperse particles, and if the iron powder is sintered in clusters, the alloy powder will also be clusters. Fine granular alloy using the six-prong method. The production of powder is an extremely simple process and does not require steps such as ball milling, so there is very little contamination with impurities and the production cost is low.

[Specific illustration of the invention]

Examples of the present invention are shown below.

Example 1 High-purity iron oxide powder (Fe, 99.9% or more, particle size 0.1 to 1.0 μm) obtained from the hydrochloric acid recovery equipment of Nisshin Noh Steel Co., Ltd.'s Sakai Works was heated using electricity. Hydrogen gas reduction was performed at 500° C. for 5 hours using a resistance heating type rotary kiln to obtain fine reduced iron powder with a reduction rate of 99% and a particle size of 0.5 to 2.0 μm. 56g of this reduced iron powder and 100c of water
c and 300 with an attritor manufactured by Mitsui Miike Kakoki Co., Ltd.
A dispersion treatment was performed at rpm for 2 hours to form a slurry. This slurry was heated to 80 to 90°C and stirred vigorously using a propeller stirrer, while adding stannous sulfate (SnSO4.2H,
O) 132g/Q and lead nitrate (Pb(NO3)z) 1
Mixed aqueous solution with 40g/n (Sn in this solution:
Pb = 60: 40 (weight)), and after addition 3
The mixture was heated and stirred for 0 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand still to precipitate the produced tin-ship gold powder, and the supernatant liquid was removed. Next, the operations of washing with water, standing still, and separating are repeated five times, followed by filtration and drying to obtain tin-lead alloy fine powder 154.
I got g. According to analysis by ICP, the composition of this powder is Sn: Pb = 60: 40 (weight),
Impurities were less than 1%. Furthermore, the particle size of this powder was determined to be 0.5 to 2.5 μm as measured by microtrack analysis.

Example 2 33 g of reduced iron powder and 100 g of water, the same as used in Example 1
cc was made into a slurry using an attritor. Next, ammonium chloride (NH4CQ) 200g/Q and silver chloride (A
gCQ) 120g/Q and palladium chloride (PdCn
, ) 35.5g/Q mixed solution (Ag in this solution
: Pd=80 : 20 (weight)) IQ 80-90
While maintaining the temperature at ℃ and stirring strongly with a propeller stirrer,
The slurry from above was added. Note that ammonium chloride was added to form a silver complex.

After the addition, the mixture was heated and stirred for 30 minutes to sufficiently advance the substitution reaction. After that, stirring was stopped, and the produced silver-Paran 94 alloy powder was allowed to settle, and the supernatant liquid was removed.Then, the steps of washing with water, standing, and separation were repeated 5 times, and then filtered and dried. 107 g of silver-palladium alloy fine powder was obtained. By the same analysis as in Example 1, Ag: Pd=flO
: 20, impurities less than 1%, particle size 0.5-2.5 μm.

Example 3 50 g of the same reduced iron powder as in Example 1 and 100 cc of water were made into a slurry using an attritor. Next, 100g/+2 of sodium thiosulfate (Na2SzOa) and cupric chloride (Cu
CQ, 2H,O) 144g and silver chloride (Ag(,
Q) 30g of mixed solution (Cu:Ag=8 in this solution)
0:20 (weight)) IQ was heated and maintained at 80 to 90°C, and the slurry was added while stirring strongly with a propeller stirrer. Note that sodium thiosulfate was added to form a silver complex. Added heat, heating.

While stirring, the substitution reaction proceeded sufficiently. After that, stirring was stopped and the copper-silver-gold powder was allowed to settle, and the supernatant liquid was removed.Next, the process of washing with water, standing still, and separating was repeated 5 times, followed by filtration, drying, and copper-silver gold powder. Silver alloy fine powder 72
I got g. According to the same analysis as in Example 1, Cu:Ag=
80: 20 (weight), impurities less than 17%, particle size 0.
It was 5 to 2.5 μm.

[Action/effect of the invention]

As explained in detail above, according to the manufacturing method of the present invention, various alloy fine powders with a particle size of 0.1 μm to 3.0 μm and a spherical shape can be produced in a comparative manner without using a crusher such as a ball mill. It can be manufactured at low cost using simple equipment. Note that this method does not involve work at high temperatures, so it has the advantage of having a relatively small amount of oxide film and less contamination of impurities from the crusher.

Therefore, it can be used as a material for conductive pastes, conductive adhesives, and solder pastes that require a small oxide film.

Claims (1)

[Claims] 1. A method for producing an alloy powder consisting of two or more of tin, lead, copper, silver, and palladium and having a particle size in the range of 0.1 to 3.0 μm, the composition of the alloy aiming at acid salts of each component metal. By preparing a mixed solution containing in the same equivalence relationship as and bringing this solution into contact with reduced iron powder with a particle size of 0.1 to 3.0 μm in an amount sufficient to precipitate the entire amount of component metals present in the solution. How to become.