Category: knowledge

What is the Indium Bonding for Sputtering Target?

Read more: What Is Indium Bonding for Sputtering Target?

The term “indium bonding” in the thin film coating industry, simply speaking, refers to bonding two (or more) sputtering targets with indium (In), or one (or more) indium plates together.

Indium

Indium can be uniquely used in lower temperature solders, is one of the softest materials. Indium is preferred for target bonding because of its excellent thermal conductivity of all available bonds. In addition, indium is the most efficient material at drawing heat away from the sputtering target. Most materials can be indium bonded and there are just a few exceptions.

Apart from indium bonding, indium is also popular for a variety of uses and purposes, such as creating alloys, photoconductors, and thermistors.

Indium bond

Sputtering targets can be cracked, warped, or damaged due to inadequate cooling, low hardness, or other reasons. From this point of view, although target bonding does generate a fee, it can well protect your target from damage. It is especially true for those less-strong target materials and precious metal materials.

Elastomer is an alternative bonding method that touts a higher temperature capability over the indium bond. Elastomer bonds are recommended when you are consistently melting indium bonds. We also recommend elastomer bonding for low melting point target materials, as well as, temperature-sensitive compounds and targets that have either low density or are especially fragile.

indium target bonding

Indium bonding is preferred in applications where:

Cryogenic stability is needed

Sealing requires high levels of hermeticity

Maximum thermal transfer is required

Bonding to not-metallic surfaces

Flux cannot be used

Backing plates

OFHC Copper Backing Plate is another well-known backing plate. It is frequently used to bond ceramic targets because of its non-magnetism and low coefficient of thermal expansion. This metal has good electrical and thermal characteristics while also being easy to machine, easy to soften, and readily available at a low cost. Copper backing plates can be re-used, with care, 20 or more times.

A molybdenum plate is usually used to substitute copper plate if copper is not appropriate for the application. For instance, the coefficient of expansion for copper is mismatched with some ceramics. And for high-temperature bonding, copper may also oxidize badly or warp. In these conditions, molybdenum is a more suitable material.

SAM Sputter Target

If you are looking for an indium bonding manufacturer, SAM is undoubtedly your best choice. Stanford Advanced Materials is devoted to machining standard backing plates and working together with the Taiwan Bonding Company for providing bonding services. For questions about target bonding materials, methods, and services, please see our listing of frequently asked questions (FAQs).

Related blog: When do you need target bonding?

Deposition of silver on glass by e-beam evaporation

The case

I am attempting to use silver evaporation pellets to deposit one-micrometer thick silver layer on the glass substrate. I found that only electron beam evaporation is accessible within the facility. I tried Ag/Ti/glass but silver peels off the Titanium layer. Up to now, only Ag/Au/Ti/glass can partially work, and only 1/2 of my samples were fully coated with silver; the other half turned into blackish-rainbow color. I wonder what is wrong in the process? Should I should some intermediate layers?

Possible Cause and Solution

The thickness of the Titanium (Ti) layer may be too large. Generally speaking, 5 to 10 nm is enough in this case.

The process is not operated in a good vacuum condition, thus the titanium layer is oxidized. In electron beam evaporation, as well as other vacuum evaporation, the vacuum degree of the evaporator is extremely important, which will greatly influence the quality of the film obtained. Thus, please make sure the vacuum chamber is well sealed before evaporating.

It is hard to avoid that the evaporated silver (as well as gold) only loosely connected to the glass substrate. Cleaning the glass with acetone and then methanol could help. Or you can just replace the glass substrate by using another transparent substrate, such as Al2O3, SiO2, AlN and Diamond. The silver layer can better deposit on those substrates mentioned above.

Other Suggestions

Titanium is an excellent adhesion layer, but it is also true that it may lose some of its adhesiveness if the vacuum is not good enough. As for its alternatives, Chromium (Cr) and Aluminum (Al) are recommended to act as the adhesion promoter.

Rising the temperature up to 100℃ in the vacuum for a few minutes may also improve the adhesion of metals.

Silver (Ag) Evaporation Materials
Silver (Ag) Evaporation Materials

For the explanation of the terminologies of vacuum coating mentioned in this passage, please refer to Terminologies of Vacuum Evaporation.

For high purity silver evaporation materials, please visit Stanford Advanced Materials.

For more news and knowledge about vacuum coating, please see SAM News.

Molybdenum Target Mammography Detection

Breast cancer, one of the major causes of deaths among women, affects about 12% of women around the world. According to research surveys, the smaller the breast cancer is when it is detected, the less the possibility of death. This requires that women should go over the medical body check regularly to decrease the risk of breast cancer. At present, molybdenum target mammography is considered the recommended breast screening examinations for women’s breast cancer.

What is the Breast Cancer?

Breast cancer is caused by the development of malignant cells in the breast. It is a sign of breast cancer when cells in the breast begin to grow out of control, and these cells usually result in forming a tumor.

Breast Cancer
Breast Cancer

 

Breast cancer itself is not a fatal disease because the breast is not an indispensable organ for maintaining human life. However, if the malignant cells spread to other important parts of the human body, such as the heart, the liver, and kidney, breast cancer may lead to death.

Breast cancer occurs almost entirely in women, but men can get breast cancer, too. And it is closely related to age—only 5% of all breast cancers occurring in women under 40 years old.

What is Molybdenum target mammography?

Molybdenum target, or molybdenum sputtering target, is known as the materials in physical vapor deposition for film coating.

Molybdenum target mammography is another important application of Molybdenum target. It is a non-invasive method to test breast diseases such as breast mass and calcification. From the viewpoint of techniques, it is a digital imaging technology that combines traditional radiology technology with modern computer technology that transforms the X-ray image into a digital image that can be quantized. Molybdenum target mammography enables radiologists to find suspicious malignant lesions in mammography easier. Thus, it has been used as a routine examination to reduce the risk of breast cancer.

Molybdenum target mammography
Molybdenum Target Mammography

Why is Molybdenum target mammography beneficial?

Molybdenum target mammography is currently the primary choice for the diagnosis of breast disease. It is an easy and non-invasive method of examination which can accurately reflect the condition of the entire breast. What’s more, it can be used to observe the breast disease caused by various factors and the results are relatively reliable. With the help of Molybdenum inspection, some precancerous lesions can be found and can be followed up for observation. So it is beneficial for women’s health.

Above information is from SAM Sputter Target, a global sputtering targets manufacturer specialized in Molybdenum target.

How was Molybdenum discovered? | History of Molybdenum

The brief history of the discovery of molybdenum

Although molybdenum was discovered in the late 18th century, it was used early before its discovery. For example, in the 14th century, Japan used a molybdenum-containing steel to make a saber. In the 16th century, molybdenite was used as graphite because it was similar to the appearance and properties of lead, galena, and graphite. At that time, Europeans referred to these kinds of molybdenum-containing ore as “molybdenite”.

Bengt Andersson Qvist
Bengt Andersson Qvist

In 1754, the Swedish chemist Bengt Andersson Qvist tested the molybdenite and found that it did not contain lead, so he believed that molybdenite and galena were not the same substance.

In 1778, the Swedish chemist Carl Wilhelm Scheele found that nitric acid did not react with graphite. While nitric acid reacted with molybdenite and produced a white powder, which was boiled together with an alkali solution to crystallize a salt. He believes that this white powder is a kind of metal oxide. After heating with charcoal, no metal is obtained; and when it is heated together with sulfur, the original molybdenite is obtained, so he believes that molybdenite should be an unknown mineral.

Peter-Jacob-Hjelm
Peter Jacob Hjelm

Inspired by Scheler, in 1781, the Swedish chemist Peter Jacob Hjelm used a “carbon reduction method” to separate a new metal from the white powder and named the metal “Molybdenum”.

Molybdenum industry development

Since molybdenum is easily oxidized and has high brittleness, molybdenum smelting and processing are limited. Molybdenum was not able to be machined in the early period, so it is impossible to apply molybdenum to industrial production on a large scale. At that time, only a few molybdenum compounds were used.

In 1891, France’s Schneider Schneider took the lead in the production of molybdenum-containing armor plates using molybdenum as an alloying element. It was found to have superior properties, and the density of molybdenum was only half that of tungsten. Molybdenum gradually replaced tungsten as an alloying element of steel. The application of the molybdenum industry was started.

At the end of the 19th century, it was found that the properties of molybdenum steel were similar to those of tungsten steel of the same composition after the addition of molybdenum in steel. In 1900, the production process of ferromolybdenum was developed. The special properties of molybdenum steel to meet the needs of gun steel materials were also discovered. This made the production of molybdenum steel rapidly developed in 1910. Since then, molybdenum has become an important component of various structural steels that are resistant to heat and corrosion and has also become an important component of non-ferrous metals — nickel and chromium alloys.

This history column aims at introducing the history of different metal elements. If you are a metal lover or history lover, you can follow our website. For previous posts of metal history, you can look them up in the “history” category.

Please visit https://www.sputtertargets.net/ for more information.

Short introduction to the element: Scandium

SAM®Scandium was first discovered by Lars Nilson in 1879. The origin of the name scandium comes from the Latin word ‘scandia’ meaning Scandinavia. It is a bright, silvery-white metal with active chemical properties that it easily oxidizes in air and reacts strongly with water. It has many of the characteristics of the rare earth elements, particularly yttrium.

In absolute terms, however, scandium is not rare. Scandium is abundant in minerals that it is found in concentrated amounts in the minerals euxenite, gadolinite and thortveitite; however, most of them existed as the form of scandium oxide (Sc2O3); thus due to the difficulties in the preparation of metallic scandium, global trade of the pure metal Scandium is very limited.

Scandium is usually alloyed with aluminum. Aluminum scandium alloys are used in the aerospace industry and other applications such as bicycle frames, fishing rods, golf iron shafts and baseball bats, etc. When used as an alloying element, adding a small amount of scandium to the aluminum alloy can promote grain refinement and increase the recrystallization temperature from 250 ° C to 280 ° C. Scandium is a strong grain refiner and an effective recrystallization inhibitor for aluminum alloys. It has a significant effect on the structure and properties of the alloy, and greatly improves the strength, hardness and corrosion resistance of the alloy.

Aluminum Scandium alloy

In addition to scandium alloys, garnets containing scandium are used as gain media in lasers, including those used in dental surgery, and scandium-stabilized zirconia has been recognized as a high-efficiency electrolyte in solid oxide fuel cells. Finally, scandium oxide is used in metal-halide lamps that are used to produce high-intensity white light that resembles sunlight.

Basic specification of scandium

Symbol: Sc
Atomic Number: 21
Atomic Weight: 44.95591
Color: silvery white
Other Names: Skandium, Skandij, Scandio
Melting Point: 1541 °C, 2806 °F, 1814 K
Boiling Point: 2836 °C, 5136 °F, 3109 K
Density: 2.985 g·cm3
Thermal Conductivity: 15.8 W·m-1·K-1

Please visit https://www.sputtertargets.net/ for more information about Scandium and other rare earth elements.

When do you need target bonding?

This post gives an answer when should require a target bonding service and how to choose different bonding services.

SAM®Sputtering targets are the material that is indispensable during a sputtering process. Sputtering targets are normally comprised of one to three distinct parts, including the backing tube, a bonding layer, and the target material. The figure shown below is an example of rotatory sputtering target. Among them, the former two parts are not unnecessary, depending on the type of materials required for the sputtering process and the manufacturing techniques that are available to produce the target. If the target material is brittle and can be easily broken during the sputtering process, it is necessary to require a target bonding service.

parts of rotatory target
parts of rotatory target

 

In terms of the target material, sputtering target varies from pure metal to ceramics. Many pure metal targets are stronger, thus some of them can be made into single piece or monolithic targets without the backing tube or a bonding layer. In contrast, ceramic targets usually require the three-layer construction technique because they are not strong enough to support their own weight and the pressure inside the tube.

Ceramic targets are usually bonded to a stainless steel backing tube because of its non-magnetism and low coefficient of thermal expansion. The thermal expansion coefficients of the backing tube material and the target can never be ignored, because a great difference between these two coefficients can lead to large stress concentrations in the target material during the sputtering process that can cause the ceramic materials to crack and break off.

In addition to stainless steel backing, indium bonding is used more frequently due to its low melting point, good thermal conductivity, low chemical reactivity, and good adhesion to most materials. Indium has the best thermal conductivity of all available bonds and is the most efficient at drawing heat away from the target. Most materials can be indium bonded but there are a few exceptions, mainly due to the low melting point of indium. Indium has a melting point of 156.6°C so temperatures in excess of 150°C will cause the bond to melt and fail.

Stanford Advanced Materials is devoted to machining standard backing plate. Please visit https://www.sputtertargets.net/ for more information.

Requirements of ITO sputtering targets for LCDs

After a long period of development, the quality of liquid crystal displays (LCDs) continues to increase, and the cost continues to decline. This means that LCDs have higher requirements for ITO sputtering targets. Therefore, in order to keep up with the development of LCD, the future development trend of ITO targets is as follows:

Liquid crystal displays
Liquid crystal displays
Lower resistivity

In recent years, liquid crystal displays have been moving in a more and more refined direction, and with the upgrade of drivers, a transparent conductive film with lower resistivity is required. Therefore, the resistivity of their raw material—ITO target—is also required to be lowered.

Increase target density

When the target density is low, the surface area for effective sputtering is reduced, and the sputtering speed is also lowered. The high-density target has uniform surface, and can obtain low-resistance film. In addition, the density of the target is also related to its service life, and the high density target generally has a longer life. This means that increasing the density of the target not only improves the film quality, but also reduces the cost of the coating, so it must be the direction for the future development of ITO targets.

Larger size

Now that the LCD screen is getting bigger and bigger, correspondingly, the size of the ITO target has to be larger. However, there are still many problems to be solved in large area coating. In the past, people weld small targets together and splice them to achieve large area coating. But the joints were likely to cause a drop in coating quality. In order to solve this problem, the size of ITO sputtering target is required to be larger in the future. This is also a big challenge for the ITO target industry.

Higher use ratio

Planar targets are still one of the most used types of sputtering targets. But one of the deadliest disadvantage of planar targets is the low use ratio. People may develop other types of ITO target, such as rotatory targets and cylindrical planar targets in the future to increase target utilization.

Please visit https://www.sputtertargets.net/ for more information.

An overview of rare earth element

The content of rare earth elements in the earth’s crust is not that scarce as the name suggests. The total Clark value of rare earth is 234.51%, which is more than common elemental copper (Clarke value 10%), zinc (Clarke value 5%), tin (Clark value 4%) and cobalt (Clarke value is 3%). However…

Rare earth definition

Rare earth contains 17 metal elements of lanthanides as well as scandium and yttrium. Scandium and yttrium are included in rare earth element because they are often symbiotic with lanthanide elements in mineral deposits, thus have similar chemical properties.

rare earth element

Discovery of Yttrium

There are 250 kinds of rare earth minerals in nature. The first to discover rare earths element was the Finnish chemist John Gadolin, who separated the rare earth element yttrium (Y) from a bituminous heavy ore (Yttria, Y2O3) in 1794.

Origin of the name

There were few rare earth minerals discovered in the 18th century, and using  chemical methods can only a small amount of water-insoluble oxides could be produced. At that time, people often referred to water-insoluble solid oxides as earth. For example, aluminum was called “ceramic earth” and calcium oxide was called “alkaline earth”. At that time, rare earths are generally separated as oxides, and because of the small quantity, they were thus named Rare Earth (RE or R).

Rare earth is not rare

The content of rare earth elements in the earth’s crust is not that scarce as the name suggests. The total Clark value of rare earth is 234.51%, which is more than common elemental copper (Clarke value 10%), zinc (Clarke value 5%), tin (Clark value 4%) and cobalt (Clarke value is 3%). However, the distribution of rare earth elements is too scattered, and these seventeen elements always exist at the same time, so the total purity is not high. In general, minerals containing 10% rare earths can be called rare earth-rich ores; pure rare earth products are expensive due to their similar properties and difficulty in extraction.

Physicochemical property

  1. Lack of sulfides and sulfates, indicating that the rare earth elements have oxytropism;
  2. The silicate of rare earth is mainly island-shaped, without layered, frame-like and chain-like structures;
  3. Some rare earth minerals (especially complex oxides and silicates) exhibit an amorphous state;
  4. The rare earth minerals mainly include silicates and oxides in magmatic rocks and pegmatites, and fluorocarbonates and phosphates in hydrothermal deposits and weathering crust deposits;
  5. Rare earth elements are often symbiotic in the same mineral due to their similar atomic structure, chemical and crystal chemical properties. That is to say that the rare earth elements of the cerium and the yttrium are often present in one mineral. But these elements do not coexist in equal amounts– some minerals are mainly composed of cerium, and some minerals are mainly yttrium.

Please visit http://www.sputtering-targets.net/ for more information.

How was tantalum discovered? | History of Tantalum

In the middle of the 17th century, a very heavy black mineral (density of SAM®Tantalum is 16.68 g/cm3) found in North America was sent to the British Museum for safekeeping. After about 150 years, in 1801, British chemist Charles Hatchett accepted the ore analysis task from the British Museum. He discovered a new element and named it Columbium (later renamed Niobium) to in honor of the place where the mineral was first discovered – Colombia.

Tantalum

In 1802, when the Swedish chemist Anders Gustaf Ekberg analyzed their minerals (the niobium-tantalum ore) in Scandinavia, he discovered a new element. He named it Tantalum, referring to the name of Tantalus, the son of Zeus God in Greek mythology.

Because Niobium and Tantalum are very similar properties, they were once thought to be the same element. In 1809, the British chemist William Hyde Wollaston compared the Niobium oxide and Tantalum oxide. Although they gave different density values, he still believed that the two were identical substances.

Tantalum Discovery History

By 1844, the German chemist Heinrich Rose refuted the conclusion that Niobium and Tantalum were the same elements, and proved that they are two different elements through chemical experiment. He named the two elements “Niobium” and “Pelopium” in the name of the Greek mythology of Tantalus’s daughter Niobe (the goddess of tears) and the son of Pelops.

In 1864, Christian Wilhelm Blomstrand, Henry Edin St. Clair Deville and Louis Joseph Troost clearly proved the Tantalum and Niobium are two different chemical elements ,and determined the chemical formula of some related compounds. In the same year, Demarinia heated tantalum chloride in a hydrogen atmosphere, and got tantalum metal for the first time through a reduction reaction. Early tantalum metals contain many impurities, and it was not until 1903 that Werner von Bolton first made pure tantalum metal.

This is a history column of SAM Sputter Target, aiming at introducing the history of different metals. If you are a metal lover or history lover, you can follow our website. For previous posts of metal history, you can search the keyword “history”.

Please visit https://www.sputtertargets.net/ for more information.

Optical Coating: Anti-wear films (hard coating film)

As a raw material for the deposition of hard coatings by PVD technology, the target will directly affect the physical and mechanical properties of the hard coating films. Therefore, the selection of good sputtering targets for coating preparation is of great practical significance.

Spectacle lenses made of inorganic materials or organic materials can cause scratches on the surface of the lens due to friction with dust or gravel (silicon oxide) during daily use. Compared with glass sheets, organic materials have lower hardness and are more likely to cause scratches. Through the microscope, we can observe that the scratches on the surface of the lens are mainly divided into two types: one is because the scratches generated by the gravel are shallow and small, and the wearer is not easy to detect; the other is the scratch caused by the larger gravel, which is deep and peripherally rough, and will affect people’s vision if it is in the central area. In order to improve the anti-wear of optical lenses, people began to study optical coatings to produce anti-wear films.

glass-lens-scratches-optical-coating

Technical Development

First generation anti-wear film technology

Anti-wear films began in the early 1970s when it was thought that glass lenses were not easy to wear because of their high hardness, while organic lenses were easy to wear because they are too soft. Therefore, the quartz material is plated on the surface of the organic lens under vacuum to form a very hard anti-wear film. However, due to the mismatch between the thermal expansion coefficient and the substrate-based material, the film is easy to take off and the film layer is brittle, thus the anti-wear effect is not ideal.

Second generation anti-wear film technology

After the 1980s, researchers theoretically found that the mechanism of wear is not only related to hardness, but also related to the dual characteristics of “hardness/deformation” of the film material, that is, some materials have higher hardness but less deformation, while some materials have lower hardness but greater deformation. The second generation of anti-wear film technology is to apply a high hardness and less brittle material to the surface of the organic lens by the immersion process.

Third generation anti-wear film technology

The third generation of anti-wear film technology was developed after the 1990s, mainly to solve the problem of wear resistance after the organic lens is coated with anti-reflection film. Since the hardness of the organic lens substrate and the hardness of the anti-reflection film layer are very different, the new theory suggests that an anti-wear film layer is required between the two layers, so that the lens are not easy to be scratched. The hardness of the third-generation anti-wear film material is between the hardness of the anti-reflection film and the lens base, and the friction coefficient is low and is not easily cracked.

optical coating

Hard coating film preparation technology

Physical vapor deposition is the mainstream technology of hard coating materials preparation. The main methods are sputtering, such as magnetron sputtering; and cathode arc evaporation, such as multi-arc ion plating.

Sputter Coating

Sputtering uses ions generated by an ion source (generally Ar ions), and accelerates them into a high-speed. The high-energy ion beam in a vacuum electric field bombards the surface of the sputtering target, and kinetic energy exchange between ions and target atoms. When the ion energy is sufficient, atoms on the surface of the sputtering target will leave the target and deposit on the surface of the substrate to form a thin film.

Cathodic arc evaporation

Cathodic arc evaporation is a PVD deposition method that uses arc evaporation electrode material as a deposition source. The low-voltage, high-current electron beam forms an arc on the surface of the material. When the arc moves on the surface of the target, the high current forms a local high temperature, which causes the surface of the metal ion evaporation material on the target surface to form a plasma. After that, a high-speed high-energy ion current is obtained by the electric field, and a film of the coating material is deposited on the surface of the substrate.

As a raw material for the deposition of hard coatings by PVD technology, the target will directly affect the physical and mechanical properties of the hard coating films. Therefore, the selection of good sputtering targets for coating preparation is of great practical significance.

Please visit https://www.sputtertargets.net/ for more information.