JPH08216160A - Mold for molding resin - Google Patents

Abstract

PURPOSE: To extend the life of a mold for molding an epoxy resin or the like by using a hard alloy enhanced in corrosion resistance against corrosion generated from the initial stage of use to enhance the hardness of the mold. CONSTITUTION: A WC base hard alloy of which the bonding phase is 3-10% of a Co-Cr type bonding phase is characterized by that the particle size of the sintered element thereof is 0.6μm or less and constituted by replacing a part of WC with a metal selected from Ta, Nb, V and Mo, carbide, nitride or carbonitride thereof within a range of 5wt.% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide tool of a resin molding die having excellent wear resistance and corrosion resistance.

[0002]

2. Description of the Related Art Generally, for sealing electronic parts, a pot in which upper and lower molds engraved with the product shape are closed and a sealing material (thermosetting resin) obtained by compacting powder is incorporated in the mold. A transfer mold is used in which it is charged into a container, heated, plasticized, pushed out by a plunger, transferred, and cured for molding. For degassing and preheating as this pretreatment,
Mold the resin into tablets. There is an example in which high speed steel having specific hardness, Young's modulus and transverse rupture strength, cemented carbide, stellite, etc. are applied to the die as in Japanese Patent Publication No. 4-32536.

With the high integration of electronic devices, the size of wiring patterns and device chips has increased, and the strength of the encapsulating resin has become more demanding. Therefore, in the process of preheating the resin, gas that is highly corrosive is used. The wear resistance resulting from the corrosion resistance of the above has become a problem, and the number of cemented carbide products, particularly JIS V3 to V5 equivalent products, has been increasing. Regarding cemented carbides, especially ultrafine grained cemented carbides, alloys made by refining WC particles and adding a small amount of TaC, Cr, V, etc. as a grain suppressor and bonding with Co are used. It has excellent wear resistance and toughness, and is widely used in practice.

[0004]

However, when cemented carbide is used for the resin molding die, the gas generated during processing of the resin corrodes the cemented carbide, and if it is used as it is, corrosion will occur. The resin adheres to the part, especially the silica particles contained in the resin bite into it, and the unevenness of the tablet-shaped outer peripheral part becomes severe. There were problems such as being modeled and insufficient degassing.

[0005]

It is an object of the present invention to use a cemented carbide having improved corrosion resistance against corrosion that occurs from the beginning of use, to increase the hardness, and to extend the life of the mold. That is.

[0006]

The present invention has been made based on the above-mentioned point of view, and a resin molding die is provided with three binder phases.
In a WC-based cemented carbide consisting of 10% to 10% Co-Cr alloy, the average grain size of the sintered body is 0.6 micron or less. Also, since the binding metal is a small amount in the Co-Cr system, one part of Ta, Nb, V, Mo metal, carbide, nitride, carbonitride is used in the range of 5% or less by weight of 1 part of WC. Alternatively, it may be replaced by two or more kinds to have a grain suppressing effect.

[0007]

[Function] To reduce the particle size and the total amount of the binder metal, the mean free path of the binder phase is thinned,
In addition to improving the corrosion resistance, it is possible to significantly reduce the number of speckled scratches initially generated by corrosion and reduce the subsequent drop of WC particles in the cemented carbide to prolong the life. The Co-Cr binder phase enhances the corrosion resistance of the binder phase against the corrosion caused by the gas generated in the step of preheating the resin, and significantly reduces the initial damage.

The composition and average grain size of the cemented carbide according to the invention are limited for the following reasons. First, the binder phase Co
If the content of the -Cr alloy is less than 3%, the amount of the binding metal is not sufficient and the toughness is not sufficiently given. If it exceeds 10%, the WC content is relatively decreased and the wear resistance is improved. In order to inhibit, it was set to 3 to 10%. Further, the amount of addition of Cr is not more than the amount of solid solution in Co, and the amount of addition of Cr in a single phase hinders the toughness, which is not preferable. Next, the average particle size of the sintered body is measured by an image analyzer. If the average particle size is 0.6 micron or less, the mean free particle of the bonding metal is measured.
h is thin enough that a pool of bonded metal is less likely to occur,
This is because the spot-like corrosion described in the section of the problem is less likely to occur.

Further, in the cemented carbide, the addition of V, TaC, etc. for the purpose of grain suppression is effective and has the effect of making the average grain size finer, but it is irrelevant to the improvement of corrosion resistance, and Cr The effect is exhibited by the combined addition of and. Hereinafter, the present invention will be described in detail based on examples.

[0010]

EXAMPLES Commercially available WC powder (average particle size 0.6 μm and 2.5 μm), Cr powder (2.0 μm), TaC powder (1.0 μm) and Co powder were used, and the composition shown in Table 1 was used. Created in.

[0011]

[Table 1]

For comparison, 92% WC-8.0% C
An alloy equivalent to JIS K30 was also manufactured by using WC 2.5 micron powder so as to have a composition of o. After mixing these powders, drying and sintering at 1400 ° C for 1 hour,
It was processed into a predetermined shape. In addition, in order to confirm changes in physical properties and microstructure, after polishing and lapping the above chips,
Hardness and fracture toughness values were measured. The results are also shown in Table 1. In addition, the grain size is microscopically observed with an electron microscope,
The image was measured with an image analyzer.

According to the measurement results of the example of the present invention and the comparative example, the average particle size of the WC phase in the present invention was 0.45 to 0.58 μm, and the average particle size of the comparative example was 2.3 μm. Furthermore, actual tablet molding was performed in a resin molding die and the performance was confirmed. The outline is shown in FIG. 1 and compared by the number of service days.

[0014]

[Figure 1]

As the resin tablet, an epoxy resin is used, and a certain amount of powdery resin is weighed and filled in a mold, and then the pressed / molded tablet is guided to a preheated mold (preheating temperature is 150 ° C.). It was cured and molded. As a result, the alloy whose hardness was adjusted to the same level had its mold surface roughened due to corrosion in about 10 days, whereas the alloy 4 of the present invention withstood for about 2 months. In this test, the effect of the particle size was significantly exhibited, whereas the comparative example reached the end of its life due to rough skin from corrosion in the early to middle stages of use, whereas the inventive example was normally worn because scratches due to initial corrosion were prevented. Has achieved longer life. In addition, regarding workability by preheating temperature that changes depending on the type of resin and the type of filler, and corrosion resistance, Co
It is possible to select the optimum component by adjusting the amount of -Cr. In addition, hard materials such as diamond or Cr on the surface
A soft substance such as N can be coated to improve corrosion resistance, wear resistance and the like.

[0016]

In the WC-based cemented carbide, the binder phase is Co
-Cr alloy, the average grain size of the WC phase in the sintered body
We have developed a cemented carbide for resin molding dies, which has a small mean free path of the binder phase and is excellent in corrosion resistance and wear resistance by making it finer than 0.6 microns.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a resin molding die according to the present invention.

[Explanation of symbols]

 1 Upper punch 2 Die 3 Resin 4 Lower punch

Claims (2)

[Claims] 1. A resin molding, characterized in that in a WC-based cemented carbide composed of a Co--Cr based alloy having a binder phase of 3 to 10%, the average grain size of the sintered body is 0.6 μm or less. Mold. 2. The WC according to claim 1, wherein one part of WC is made of one or more of Ta, Nb, V and Mo metals, carbides, nitrides and carbonitrides within a range of 5% by weight or less. A resin molding die characterized by being replaced.