Altech Chemicals Explains High Purity Alumina Use in Semi-Conductor Applications

THE BOURSE WHISPERER: Sometimes a company announcement comes along that needs to be brought to the attention of punters, simply due to the information it presents.

Altech Chemicals Limited (ASX: ATC) released such an announcement today; one that provides information regarding the use of high purity alumina (HPA) in the manufacture of epoxy moulding compounds (EMCs) that are used in the semi-conductor industry to improve heat dissipation.

Altech recently commenced an investigation of the EMC for semi-conductor market for the purpose of targeting some of its future HPA product into this market segment.

The information below is straight from the announcement. There has been no editing by The Resources Roadhouse as we feel it tells the story in a much more knowledgeable fashion than we could.

Introduction of alumina into EMCs used in semi-conductors

Typically industrial-strength epoxy compounds are used for the package assembly of semi-conductors, as the epoxy compounds provide the required physical protection, mechanical strength, as well as a number of desired performance properties – primarily in relation to heat and moisture, both of which can destroy a semi-conductor, warp an electronic device (that the semi-conductor is used in), or even cause a device to catch fire.

Electronic devices continue to become more compact – Moore’s Law – the exponential growth in the number of transistors that can be packed into a single semi-conductor.

However, thermal or heat dissipation is a real problem as semi-conductors continue to reduce in size and contain more transistors.

It is suggested that heat could represent the ultimate barrier to the ever smaller and more powerful semi-conductors that end-users have become accustomed to.

The epoxy resins that have traditionally been used for semi-conductor package assembly are reaching their limits in terms of effective heat dissipation.

However, adding thermally conductive materials into the resins has been demonstrated to improve heat dissipation and thereby improve the protection of semi-conductors against heat related failure.

The thermally conductive fillers that are being used include HPA, crystalline silica, and magnesium oxide.

HPA however is a preferred filer, due to its heat conductivity (7 times higher than silica) and a much lower thermal expansion coefficient (50% lower).

Figure 1 below illustrates a typical semi-conductor chip encased in an epoxy resin compound with HPA used as a thermal filler.

The heat produced from a semi-conductor chip and the die pad more efficiently dissipates via the alumina rich epoxy resin and lowers thermal stress related problems for the semi-conductor and the assembly package (integrated circuit board).

Figure 2 below is a scanning electron microscope (SEM) image of HPA used as a filler material in an epoxy resin moulding compound. The image demonstrates the efficiency of the conductive filler within the epoxy resin package.

The purity of the material selected as the conductive filler in an epoxy resin for use in the semi-conductor industry is extremely important, consequently there are very stringent (and low) limits on the impurities permitted in the chosen filler.

Of the impurities, sodium is probably the most detrimental element.

Radioactive material is another detrimental impurity, as gamma rays from an impurity such as thorium increases the likelihood of semi-conductor and/or CPU malfunction.

Thorium is present in bauxite, the traditional feedstock used for the production of aluminium.

A small amount of thorium residue will remain in any HPA produced via the conventional bauxite – alumina – aluminium production process (Bayer process).

Thorium is not present in HPA that is produced from Altech’s kaolin HCL processing route.

Special morphologies (crystal form, shape and structure) are also demanded of the EMC filler, in the case of HPA the industry requires a morphology that is conducive to low viscosity, an attribute that is favourable in the epoxy resin packaging process.

Altech’s preliminary investigation into the demand for high quality HPA from the EMC semi-conductor market indicates a global market size in the range of 700 – 900tpa, with a price of US$100/kg being commanded by product that meets required specifications.

Year-on-year growth in the market is typically in line with growth experienced in the semi-conductor business.

Altech believes that its low sodium HPA, and the morphology of its HPA, may be ideal for the EMC semi-conductor application, and the company intends to commence the development of a product specification that may suit this market sector’s requirements.