What's in Your Tape Media?
Did you ever wonder about the tape media when you were trying to determine your drive performance? If you are like most, your tape media is MP metal particle. Metal particle tape uses substrate material, the basefilm, which is coated with a durable and flexible Polyurethane-type paint containing, among other things, suspended metal particles. The particles consist of needle-shaped iron, or ferric cores, which have been processed to enhance their magnetic capabilities and chemical stability.
Immediately after coating, they are oriented in the same polar direction by a strong magnetic field while the paint is still in liquid form. This results in high squareness values in the direction of recording, reducing tape noise while increasing output and packing (aerial) density of the particles.
This process yields a coating that is less than 100% active magnetic material. The size and shape of the metal particles and other additives give the polyurethane paint, or coating, the desired magnetic, electrical, and physical characteristics needed to write and read data in a particular format. A backcoat is then applied to the reverse side of the substrate to control friction. Metal particle tape is used with formats such as DLT (digital linear tape) and LTO (linear tape open).
The other type of manufacturing process is metal evaporated. It is used for smaller form factor formats such as AIT (advanced intelligent tape). Unlike conventionally coated tape, metal evaporation takes place in a vacuum chamber. A specially-treated basefilm material is fed around a cooling drum that passes by a shutter area. Cobalt ingots are fed into a crucible and vaporized by a scanning electron beam gun. The ingots are vaporized at approximately 2000°C. The metal vapor is allowed to contact the basefilm and bond molecularly to it at the shutter area. Hence, there is no need for the binder, required to manufacture metal particle tape; the coating is nearly 100% active magnetic material to store the data.
A special oxygen gas is mixed with the vapor at the shutter area. The cooling drum is chilled to approximately -40°C to prevent the basefilm from melting at the shutter area from the intense heat of the vapor. The vapor and gas mixture deposits vertical column-like structures on the basefilm. The incident angle of the these columns, containing oxygen and cobalt, is at an angle consistent with the magnetic field that will emanate from the heads on the helical scanning drum inside the recorder. The shutter, which controls the angle of the columns, coupled with variations in the oxygen-cobalt mixture, determine the overall electromagnetic characteristics of the tape.