JPH01149902A - Fine granular complex powder - Google Patents

Abstract

PURPOSE:To manufacture fine granular complex powder suitable for injection molding by executing electric plating of Zn, Ni, Sn, Pb, Cu, etc., on the surface of fine granular iron powder having the specific particle size. CONSTITUTION:The electric plating of one or more kinds selected among Zn, Ni, Sn, Pb and Cu is executed on the surface of the granular fine iron powder or carbonyl iron powder having 0.1-10mu the range of the particle size, obtd. by reducing fine oxide powder with hydrogen gas. By this method, the fine granular complex powder having suitable use as the powder raw material for injection molding is obtd. and powder metallurgy product having good quality is formed at low cost and further excellent effect is shown as electrical conductive filler.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a metal powder suitable for injection molding, and further to a fine granular composite powder suitable as a conductive filler for electromagnetic shielding materials and printed circuit materials for ICs. .

[Conventional technology]

Injection molding has been known as one field of powder metallurgy. This involves thoroughly kneading fine metal powder with a binder, granulating it, molding it with an injection molding machine, and then performing a binder removal and sintering process to obtain a molded product with a complex shape.

Therefore, the densification of the finished product is mainly performed by sintering, without going through the powder compaction process as in normal powder metallurgy. However, even in the green compact state that has been injection molded, it is advantageous for densification to be as high and uniformly filled as possible. Note that if the shrinkage rate that occurs during binder removal treatment and sintering becomes non-uniform in three dimensions, the dimensional accuracy after sintering will deteriorate. From these facts, metal powder for injection molding has a spherical shape.
It is said that a fine powder with an equiaxed shape and a particle size of several micrometers is suitable. Conventionally, small particle diameter portions of atomized powder, carbonyl iron powder and nickel powder, high melting point metal powder obtained by hydrogen reduction of oxide powder, and the like have been used for injection molding.

On the other hand, in recent years, the need for electromagnetic shielding to prevent radio wave interference has been emphasized, and conductive paints using electrolytic copper powder or carbonyl nickel powder have been put into practical use. In addition, with the miniaturization, precision, and high integration of electronic components, I
As a conductive filler for C-printed circuit materials, there is a demand for metal powder that is as fine as possible, 3 μm or less in size, spherical, and inexpensive.

[Problem that the invention seeks to solve]

Traditional injection molding powder metallurgy using metal powder requires a binder. This may cause problems in densification of the sintered product and also in dimensional accuracy. Furthermore, a process for uniformly dispersing the metal powder and the binder and a process for removing the binder are added, which increases the number of man-hours and increases the cost of the binder.

On the other hand, conventional conductive metal powder used in electromagnetic shielding materials and IC printed circuit materials is generally expensive, and is a fine spherical powder made of highly conductive metal with a particle size of 3μ or less and excellent filling and dispersibility. Powder could not be obtained cheaply.

[Means for solving problems]

The present invention provides a fine granular composite powder obtained by electroplating one or more of zinc, nickel, tin, lead, or copper on the surface of granular iron powder with a grain size ranging from 0.1 u+m to 10 μm. It is something to do.

In other words, in the present invention, zinc, nickel, and tin are applied to the surface of granular iron powder having a grain size ranging from 0.1 μm to 10 μm.

A fine granular composite powder for injection molding that is electroplated with one or more types of lead or copper.

Furthermore, the present invention provides a conductive filler for electromagnetic shielding materials or IC printed circuit materials, which is made by applying nickel or copper electroplating to the surface of granular iron powder having a grain size ranging from 0.1 μm to 10 μm. .

Zinc, nickel,
The present inventors have discovered that a powder electroplated with one or more of tin, lead, and copper is the most suitable powder as a powder metallurgy raw material for injection molding. In other words, 9 When dissimilar metal powders are mixed and injection molded in the past 1 For example, when iron powder and nickel powder are mechanically mixed and injection molded, it is not always the case that they are mixed uniformly from a microscopic point of view. Therefore, there were problems with the dimensional stability, mechanical strength, and even corrosion resistance of the sintered body.
As in the present invention, if each grain of fine iron powder used is plated with nickel, for example, the uniformity of the nickel component is extremely good compared to the powder mixing method, and sintering It was found that the mechanical properties of the sintered material are uniform and have less variation, and the corrosion resistance of the sintered body is also good because this occurs between nickel and nickel. Furthermore, there is a great cost advantage in that it does not require the use of expensive nickel fine powder.

A method for obtaining fine reduced iron powder by reducing iron oxide powder with hydrogen gas is to form a uniform powder fluidized bed in a rotary kiln rotating at low speed using iron oxide powder as fine as possible.
This is possible by reducing hydrogen gas at a low temperature of 560°C or lower. With this method, from 0.1 μm to 3. Approximately spherical fine iron powder in the OtIm range can be obtained with a purity of 97wt or higher than 1. If such iron powder is used as an electroplating base material.

A much finer granular composite iron powder can be produced than using carbonyl iron powder with a particle size in the range of 3 μm to 10 μm.

In addition, instead of hydrogen gas reduced iron powder or carbonyl iron powder, acicular reduced iron powder obtained by reducing iron chloride powder with hydrogen gas (this is often used for metal tapes, etc.) can be used. can also be used as an electroplating base material, and in this case, it is also possible to impart the same characteristics as described above.1 For example, if the acicular reduced iron powder is electroplated with nickel, its corrosion resistance can be greatly improved. Can be done.

The electroplating solution used to obtain the fine granular composite powder according to the present invention includes conventionally used zinc, nickel,
Plating solution compositions of tin, lead, and copper can be used. In addition, electroless plating of N1-P, N1-B, N1-N or copper can also be performed. It is also possible to perform two-layer plating, such as electrolytic nickel plating on iron powder and then electrolytic copper coating. In this case, 1. For example, by plating the iron powder with two layers of nickel and copper, 2. the shrinkage rate during sintering can be minimized to improve the dimensional accuracy of the sintered body and reduce the residual porosity. .

As a specific technique for electroplating fine iron powder with the various metals mentioned above, for example, the method proposed in Japanese Patent Application No. 161950/1988 can be applied to the present invention.

The fine granular composite powder of the present invention can be used for graphite +
Elements such as Si+' Cr+ V, Nb+ Te, etc. may be blended in an amount. It is preferable to coat with a trace amount of added elements by sputtering.

The fine granular composite powder according to the present invention, which is made by electroplating nickel or copper on the surface of granular iron powder with a particle size in the range of 0.1 μm to 10 μm, has been conventionally used as an electromagnetic shielding material or an IC printed circuit material. It is very suitable as a conductive filler because it is cheaper and finer than nickel powder or copper powder.

The fine-grained composite powder of the present invention can be manufactured by the following manufacturing method, typical examples of which are shown below.

[Example 1 of manufacturing method] High purity iron oxide powder (average particle size; (1,65//f
fi, impurity blasphemy Cj! =0.0911t, χ, S
iO2=0.02wt, χ.

CrtOs = 0.05wt, χ, 99.5wL as FezO3, % or more) was 1.0 using Turbo Classifier TC-15N type manufactured by Nisshin Engineering Co., Ltd.
The particles were classified into particle sizes of 1.0 μm or less and iron oxide powders of 1.0 μm or less were obtained.

160g of this iron oxide powder is 100mm in diameter and 8 in length.
00mm 5US304 electric heating rotary kiln, and while rotating at 2 rpm, hydrogen gas was heated at 42 rpm.
Hydrogen gas reduction was carried out at 450°C for 10 hours by flowing at a flow rate of 7mln. After reduction, it was cooled to obtain 110 g of reduced iron powder. When this was tested, it was found that it was made of high-purity iron with a reduction rate of 97%, had an average particle size of 0.8 μm, and an aspect ratio of 2.0, and was virtually unsintered. .

30 tons of 30 g each of this reduced iron powder were taken out and subjected to two-layer plating of electrolytic nickel plating, electrolytic copper plating, electrolytic nickel plating after electrolytic copper coating, and 0
Three types of plating were performed. For plating, the same equipment as described in Japanese Patent Application No. 161950/1983 was used.

(1), Electronickel plating conditions [bath composition] Nickel sulfate 150g/42 Ammonium chloride 15g/1 Boric acid 15g/e [Plating conditions] pH 5.8 to 6.2 a, temperature Room temperature anode Nickel plate cathode Titanium plate current and Maintenance time 2.8A and 1 hour (2) 5
Electrolytic copper plating conditions [bath composition] Pyrophosphoric acid 1i1 345g/l Potassium hydroxide 18g/1 Ammonia water 10ml/It (plating conditions)
.

pH 8,2~8.8 Liquid temperature 40~60'C Anode Copper plate cathode 5US304 plate Current and plating time 2.5A and 1 hour As a result of these plating treatments, both electrolytic nickel plating and electrolytic copper plating have no effect on the iron powder surface. The amount of plating deposited was 8 wt each.
It was χ.

Regarding the two-layer coating of electrolytic copper plating followed by electrolytic nickel plating, each plating time was halved to 0.5 hours.
Performed under the same conditions as above, 4 wt.% nickel and 4-
A fine granular composite powder plated with two layers of copper of t and χ was obtained.

[Example 2 of manufacturing method] Carbonyl iron powder manufactured by ITEC (USA) (average particle size: 5.
100 g of 0 μ cocoons (purity: 99% or higher) was subjected to three types of plating: electrolytic zinc plating, electrolytic tin plating, and electrolytic lead plating under the conditions shown below. In addition.

For plating, as in Example 1,
The same equipment as shown in No. 61950 was used.

(3) Electrogalvanizing conditions [bath composition] Zinc chloride 150g/1 Ammonium chloride 200g/i! [Plating conditions] pH 3,5-4.0 Liquid temperature 3o-40"C Anode Zinc plate cathode 5115304 plate current and plating time 5A and 4 hours (4), electrolytic tin plating conditions [Bath composition] Potassium stannate 80g/1 Potassium hydroxide 30g/j! [Plating conditions] pH 12-13 Liquid temperature 80-90''C Anode Tin plate cathode 5US304 plate current and plating time 5A and 2 hours (5), electrolytic lead plating conditions [Bath composition] Lead borofluoride 205g/12 Boric acid 20g/1 Boric acid 20g/1 Gelatin 0.15g/j2 [Plating conditions] pH 1,0~2.0 Liquid temperature 30~40'C Anode Lead plate cathode 5US304 plate current and plating time 3A and As a result, a composite iron powder of the present invention was obtained which was subjected to electrolytic zinc plating, electrolytic tin plating, and electrolytic lead plating in an amount of 20 wt and χ amount.

(Effects of the Invention) The fine granular composite powder of the present invention obtained as described above is very suitable as a powder metallurgy raw material for injection molding, and it is possible to obtain high-quality powder metallurgy products at low cost. In addition, the fine granular composite powder of the present invention exhibits excellent effects as a conductive filler.It can also be applied to many uses such as rust-preventing pigments and magnetic materials.

Claims (3)

[Claims] (1) Fine granular composite powder obtained by electroplating one or more of zinc, nickel, tin, lead, or copper on the surface of granular iron powder with a particle size in the range of 0.1 μm to 10 μm. (2) The fine granular composite powder according to claim 1, wherein the granular iron powder is reduced iron powder obtained by reducing fine iron oxide powder with hydrogen gas. (3) The fine granular composite powder according to claim 1, wherein the granular iron powder is carbonyl iron powder.