Leading Group has successfully prepared metal rotating targets using supersonic cryogenic spraying technology.

In recent years, with the rapid advancement of the electronics and information industries, the applications of thin-film science have become increasingly widespread. As a key raw material in the coating industry, sputtering targets are primarily manufactured using two major processes: melting and casting, and powder metallurgy. The melting-and-casting process is commonly employed for producing metal and alloy targets. Although this process boasts a short workflow and low cost, it is relatively difficult to precisely control the target’s uniformity and grain size. By contrast, the powder metallurgy forming process uses powders as its raw material; the particle size of these powders typically needs to be less than 100 μm, and in some cases even stricter requirements—less than 10 μm—are imposed. The stringent control over particle size directly determines the grain size and compositional uniformity of the target billet after sintering.

Supersonic cryogenic spraying (cold spraying) is a powder-spraying process—a novel coating technology that operates on aerodynamic principles. In this process, high-pressure gas carries powder particles axially into the Laval nozzle of the spray gun, generating a supersonic gas flow. The powder particles—ranging in size from 1 to 90 μm—are accelerated to velocities of 500–1200 m/s by the high-speed gas flow and then impact the substrate (such as metal, ceramic, or glass) in a fully solid state. Through plastic deformation, these particles deposit onto the substrate surface, forming a dense coating. Compared to thermal spraying techniques—including supersonic flame spraying, plasma spraying, and detonation spraying—in supersonic cryogenic spraying, the substrate surface temperature typically remains below 100°C, and the particles are neither melted nor partially melted throughout the entire process. As a result, the oxygen content in the surface coating is effectively controlled, making this technique particularly well-suited for preparing metallic or alloy targets with stringent oxygen-content requirements.

Schematic diagram of the supersonic cryogenic spraying (cold spraying) principle; image source: internet.

Due to their high reflectivity and excellent light transmittance, metallic silver and its alloys are primarily used in functional materials such as reflective films for displays, storage devices, OLEDs, and Low-E glass. Materials employed as reflective film layers include elemental silver, silver-palladium alloys, silver-gallium alloys, silver-tin alloys, and silver-copper alloys. Moreover, AgGa alloy targets containing 30 atomic percent gallium can replace CuGa alloy targets in copper-indium-gallium-selenium (CIGS) thin-film solar cell structures. This is mainly because using AgGa as a raw material results in silver-indium-gallium-selenium (AgInGaSe) films with higher photoelectric conversion efficiency, making them irreplaceable in certain specialized application fields.

Domestic silver and its alloy rotary targets are mainly imported from Japan. Most of the imported silver and alloy targets are manufactured using a casting-bonding process, resulting in multi-section bonded targets. The utilization rate of rotary tube targets is only 70%, leaving 30% that needs to be recycled. If these residual targets are sent back to Japan for recycling, the high costs associated with round-trip shipping and tariffs would significantly increase the manufacturing costs for downstream manufacturers.

Metallic silver, image source: the internet

In light of this, after communicating with multiple customers and conducting thorough market research, the Thin Film Materials Division of Leading Group began developing silver and its alloy rotary targets in June 2018. Ultimately, the division settled on a supersonic, low-temperature spraying process—technologically more advanced than those used abroad—for the production of silver and its alloy rotary targets. In June 2019, the group completed construction of a cold-spray workshop and successfully passed equipment acceptance testing. After four months of experimentation, in November 2019, the group successfully produced large-size, single-element silver rotary target materials measuring OD153×1710mm, which have since been validated by our customers!

The R&D journey of silver single-element and silver alloy rotary targets; image source: Xi Jin Net.

In July 2020, the Thin Film Materials Division of Leading Group successfully developed silver alloy rotary targets, and all shipments have been validated by customers! Meanwhile, the division has subsequently received bulk orders for silver alloy targets from these same customers. The successful development of a process for preparing metal rotary targets using supersonic cryogenic spraying (cold spraying) not only provides a new solution for future R&D of target materials but also expands the Group’s market business scope, enabling it to maintain its leading position in the field of rotary targets.

Currently, the rotating targets that Leading Group can prepare using supersonic low-temperature spraying technology include:

1. Low-temperature materials based on aluminum, such as aluminum and aluminum alloys;

2. Medium-temperature materials based on copper, such as copper, silver, copper-gallium, and silver-gallium;

3. Iron-based and other high-temperature materials, such as iron-nickel-based alloys;

Partial product showcase:

1. Silver elemental target material

Specifications: OD153 × 1710mm

Product photos taken in real life; image source: Leading Group

2. Silver alloy target material

Specification: OD154 × 950mm

Product photos taken in real life; image source: Leading Group