This process produces thin metallic or ceramic films onto a. wide range of substrates which themselves can be either metallic or non metallic. The films are generally in the 1µm 10µm thickness range but these limits are not rigid, film adherence is generally better than that from vacuum evaporation or from electroplating.
The process involves the use of two electrodes, one being the target material which is deposited onto the other electrode or substrate. The electrodes are in a dynamic vacuum of approximately 10 millibars, produced by bleeding an inert gas, usually high purity argon, into a continuously pumped chamber. The potential difference across the electrodes may be DC or RF (usually 13.6MHz) and is in the order of 1000V with the target being negative with respect to the substrate. The argon gas forms a plasma of positive ions which bombard the target material and literally knock out (i.e. sputter) atoms of the target. The sputtered atoms have a high energy and when they impinge on any surface, they form an adherent coating. The substrate is arranged positioned to receive the maximum flux of sputter material.
One advantage of the system is that the targets do not have to be homogeneous and can be produced by powder metallurgical methods, or they can be cast or simply cut from bar or sheet. The composition of the coating may also be varied by making composite targets from blocks etc., taking advantage of the mixing that occurs in the plasma.
At TWI, Substrates up to 100mm in diameter may be coated to a reasonable degree of uniformity.
For information about TWI's capabilities please contact us.