JPH0324922A - Pot plunger for transfer molding - Google Patents

Abstract

PURPOSE:To obtain a hard alloy for a pot plunger for transfer molding made thin in the mean free path of a bonding phase and excellent in corrosion resistance and abrasion resistance by forming the bonding phase of a WC base hard alloy from a Co-Cr alloy and making the mean particle size of the WC phase of the sintered body of said alloy fine to set the same to specific mum or less. CONSTITUTION:The bonding phase of the WC base hard alloy used in a pot plunger for transfer molding is composed of 8 - 20% of a Co-Cr alloy and the mean particle size of the sintered body of said alloy is set to 0.8mum or less. The Co-Cr phase enhances the corrosion resistance against the corrosion due to the gas generated in a resin preheating stage and markedly reduces initial damage. When the mean particle size in the sintered body is 0.8mum or less in the measurement of a particle size by to an image analyser, the mean free path of a bonded metal becomes sufficiently thin and the pool of the bonded metal is hard to generate and spot-like corrosion and damage in an axial direction due to a silica particle become hard to generate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cemented carbide tool for a pot plunger for a transfer mold, which has excellent wear resistance.

[Prior art]

Generally, as a method for sealing electronic components, upper and lower molds engraved with the shape of the product are closed, and a sealing material made of compacted powder (
In recent years, transfer molding has been carried out, in which a thermosetting resin (thermosetting resin) is placed in a pot built into a mold, heated, plasticized, pushed out with a plunger, and transferred to harden or shape.In recent years, electronic devices have become highly integrated. Along with this, wiring patterns and element chips have become larger and stronger sealing resins have been required.As a result, the wear of pots and plungers has increased, and cemented carbide products, especially JIS V3
~v5 equivalent products are increasing.

On the other hand, regarding cemented carbide, especially ultrafine grained cemented carbide, WC
An alloy is used in which the particles are made finer, a small amount of TaC, Cr, V, etc. is added as a grain suppressor, and bonded with Co.The alloy is characterized by its toughness, and has both excellent wear resistance and toughness, and is widely used. It is put into practical use.

[Problems to be solved by the invention] However, when cemented carbide is used, the gas generated when the resin is processed corrodes the cemented carbide, and if it continues to be used, the resin will adhere to the corroded parts. In particular, the silica particles contained in the resin dig in, causing scratches in the axial direction on the outer periphery of the plunger, into which molten resin, silica particles, etc. infiltrate and accumulate, further interfering with the operation of the plunger.

A similar phenomenon also occurred on the inner wall of the pot, where corrosion caused spots and scratches, and like the plunger, resin adhered to these spots, causing the problem that the pot would no longer work. An object of the present invention is to use a cemented carbide with improved corrosivity and increase hardness to prevent corrosion that occurs in the early stages of use, thereby extending the life of the plunger.

[Means for solving problems]

The present invention has been developed based on the above viewpoint, and a pot plunger for a transfer mold is made of a WC-based cemented carbide made of a Co-Cr alloy with a binder phase of 8 to 20%. The hard alloy is characterized in that its sintered body has an average grain size of 0.8 microns or less.

Refining the particle size means free
In addition to making the path thinner and improving corrosion resistance, it significantly reduces spot-like scratches that occur initially due to corrosion, and also reduces axial scratches that occur later, thereby extending life.

The Co-Cr binder phase increases the corrosion resistance of the binder phase against corrosion caused by gas generated during the preheating stage of the resin.
Significantly reduces initial damage.

The composition and average grain size of the cemented carbide according to the present invention are limited for the following reasons.

1) Content of Co-Cr alloy in binder phase is 8%
If it is less than 8% to 20%, the amount of bonding metal will not be sufficient and sufficient toughness will not be provided, and if it exceeds 20%, the WC content will be relatively reduced and the wear resistance will be significantly impaired. did. Further, the amount of Cr added may be less than the amount that forms a solid solution in Co, and an amount that causes Cr to form a single phase is not preferable because it impairs toughness.

2) The average particle size in the sintered body is determined by particle size measurement using an image analyzer. If the average particle size is 0.8 microns or less, the mean free path of the bonding metal is determined.
is sufficiently thin so that pools of bonded metals are less likely to form.
This is because the spot-like corrosion mentioned in the problem section and the axial scratches caused by silica particles are less likely to occur.

Furthermore, in the cemented carbide, V,
Although the addition of TaC, etc. is effective and has the effect of making the average particle size finer, it is unrelated to improving corrosion resistance, and Cr
It is effective when added in combination with.

The present invention will be described in detail below based on examples.

〔Example〕

Commercially available WC powder (average particle size 0.6 μm and 2.5 μm)
, Cr powder (2.0μm), TaC powder (1.0μm)
m) and. The compositions shown in Table 1 were prepared using Go powder. Also, for comparison, 90WC-9.1Go-0.9Cr
An alloy corresponding to JISV4 was also manufactured using WC2.5 micron powder so as to have the following composition. These powders were mixed, dried, sintered for 1400' CI hours, and then processed into a predetermined shape.

In addition, in order to confirm changes in physical properties and microstructure, the chips were polished and lapped, and then hardness and fracture toughness values were measured. The results are also shown in Table 1.

In addition, the particle size was determined by electron microscopy. We carried out a wt observation and measured using an image analyzer based on the photograph. The measurement results of the present invention and the comparative example show that the average particle size of the WC phase is 0.55 to 0.75 μm in the present invention, and 2.3 μm in the comparative example.
It was m. Furthermore, we confirmed its performance in actual resin sealing work using a single-type transfer mold. The outline is shown in Figure ↓, and the service life is compared. Using epoxy resin as a resin tablet,
The preheated tablet was pressed and fluidized, introduced into a preheated mold (preheating temperature was 150 degrees Celsius), and cured and shaped.

As a result, even when using alloys whose hardness was adjusted to the same level, the comparative example reached the end of its life due to axial scratches in about 2 months, whereas the alloy 4 of the present invention lasted about 10'+ months. In this test, the influence of particle size was noticeable, and while the comparative example reached the end of its service life due to corrosion and axial scratches in the early to middle stages of use, the inventive example was able to prevent scratches due to initial corrosion. Longer life has been achieved through normal wear.

Also, regarding the processability and corrosion resistance due to the preheating temperature, which varies depending on the type of resin and filler. CoCr amount! )!
! It is possible to select the optimal component by adjusting the

〔Effect of the invention〕

In WC-based cemented carbide, the mean fr of the binder phase can be reduced by using a Co-Cr alloy as the binder phase and refining the average particle size of the WC phase in the sintered body to 0.8 microns or less.
We have developed a cemented carbide for transfer molding pots and plungers with a thin ee path and excellent corrosion and wear resistance.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the transfer mold according to the present invention, and FIG. 2 is a sectional view of the pot, showing the state at the initial stage of use. FIG. 3 is also a sectional view of the pot, showing its state after long-term use.

Claims (1)

[Claims] A pot plunger for transfer molding, characterized in that the average grain size of the sintered body is 0.8 microns or less in a WC-based cemented carbide made of a Co-Cr alloy with a binder phase of 8 to 20%.