Takao Fujikawa

Atmosphere Control in the Hip Treatment of Ceramics

Hot Isostatic Pressing (HIP) of ceramics has been recognized as an ideal process to produce fully dense and highly reliable parts in the course of application to ferrite magnetic recording heads, alumina cutting tool inserts, and automobile engine parts made of silicon nitride. Usually these parts are processed by the so-called capsule-free method in which the processed parts are exposed directly to the pressure medium gas. In this case, some interactions between the processed parts and the gas may occur and this phenomenon has to be carefully considered for some nitrides and oxides. Here, the influence of the surrounding gas is termed as an atmosphere and discussed from the viewpoint of thermo-dynamics. Three practical methods to create the desired atmospheres are explained and some examples in the application are given for silicon nitride, superconductive ceramics, and calcium carbonate.

Recent Development Of O2-Hip Equipment

Progress in the development of O2-HIP equipment is described in this paper regarding safety and the achievement of a new high temperature O2-HIP apparatus.

Development and application of ultra-high-temperature HIP by means of an optical temperature measurement system

Abstract The development of an optical temperature measurement system has made ultra-high-temperature HIP processing feasible. Previously, HIPing at temperatures in excess of 2200°C was difficult to operate stably with the conventional W/Re thermocouple. Using the system developed, glassy carbon, which is expected to be used as the substrate in magnetic heads and hard disks was HIPed at 2600°C and 200 MPa and confirmed to be fully densified.

Recent Advances in HIP Technology and Atmosphere Control in HIP Treatment

HIP treatment, invented in the United States in mid 50’s, is now widely used in industries, in order to obtain fully dense materials made of metals and ceramics. Usually HIP treatment is carried out in a high pressure gas atmosphere of inert gas such as argon to prevent unfavorable surface reactions occur during treatment. However in the case of ceramics, changes in the chemical composition may occur in such an inert atmosphere, because ceramics are usually compounds of metals and gaseous elements such as oxygen, nitrogen. Thus for example some oxides require HIP treatment under an atmosphere with oxygen partial pressure, or oxygen in the work-piece will dissipate into the atmosphere and the chemical composition of the resultant work-piece change from the original one and sometimes the electronic properties or colors change. To prevent such unfavorable phenomenon, the atmosphere control HIP treatment technologies have been developed mainly in Japan. Three types techniques of atmosphere controlling around the work-piece are known. One is the full pressure method, another is the partial pressure method and the third one is the powder-embedding method. These methods are applied depending on the required atmosphere and availability. For example in the case of silicon nitride, full gas pressure method using pure nitrogen gas as pressure medium is used and this method became very popular in Japan. In the case of super-conductive oxide ceramics, the oxygen partial pressure methods have been employed.

Recent Advances in Dry-Bag Cip Equipment

Dry-bag CIP process has become a very popular method in the large volume production of powder compacts in the P/M and ceramic industries. Intensive technological research on the Drybag equipment has been carried out to improve the dimensional accuracy and the productivity. In this study, the rubber mold design technology with FEM simulation during pressing has been introduced, in order to achieve higher dimensional preciseness, and criteria for the selection of Drybag equipment, namely the In-line type or Off-line type, have been established based on the powder flowability index proposed by Carr. Based on these research results, high productivity Off-line Drybag CIP equipment, which can realize good dimensional accuracy with high productivity, was developed even for non granulated powders with poor packing density. This paper describes the research results and the present status of the most advanced Off-line Dry-bag CIP equipment technologies.

Recent Trends of HIP Equipment Technology in Japan

The progress of HIP (Hot Isostatic Pressing) is discussed from both the historical viewpoint and its future potential. HIP is now recognized as a useful method to obtain products with isotropic properties and high density. It is used in the manufacture of high integrity castings, various PM products and ceramic components. Especially in Japan these resultant natures have attracted attention from ceramic researchers, because HIP can compensate for the lack of reliability due to residual porosity formed in the sintering stage. P/M High speed tool steel billets, alumina cutting tool inserts, soft ferrite for magnetic recording heads all have been produced by the HIP process. Research activities are now expanding into so-called nano-technology areas such as Si-wafer processing and nano-level sensors. Entering the 21st century, however, a sluggish economy and environmental friendliness are producing strong demand for further development of smaller and lighter products with higher mechanical or electronic properties. In addition to these, the requirement for the higher productivity to reduce processing cost is intensifying, thus the developmental works on HIP equipment technology are being focussed on the improvement of its productivity as well as application to novel processing areas.Copyright

Application of high pressure process into Cu/low-k technologies

High-pressure processing in the range of 16-120 MPa has been introduced to Cu/low-k interconnect technologies as a new generation. Hot isostatic pressing (HIP) was applied to the formation of Cu plugs with a high aspect ratio. A new finding related to a combination with electroplated Cu is also discussed. A supercritical CO/sub 2/ fluid was applied to a formation of low-k porous silica films as a means of capillary-force-free drying. A low dielectric constant, as low as 1.1, was achieved by using this technique. It is demonstrated that high-pressure processing has several attractive advantages for semiconductor processing.