Effects of Additives in Ethylene Glycol-based Lubricant on Selective Material Removal in Slider Lapping Process

AbstractChemical mechanical nano grinding is a key technology in magnetic recording head manufacturing process. The magnetic recording head is an important component of hard disk drive which is used for reading and writing data in to the media. Thin film of metal alloys and metal oxides are fabricated on ceramic substrate called wafer to create the recording heads. In order to control surface properties of the recording head, the precise chemical mechanical nano grinding process is used. In this process the recording heads are treated to archive the designed surface properties by using lubricants to control the selectivity of material removal. This research studied the effect of additives in ethylene glycol based lubricant on the selectivity of material removal. Two additives were added in ethylene glycol to create the lubricant and their pHs were measured. The material removal rate can be predicted by measuring wettability of lubricant on surface of material. Nickel iron alloy (NiFe) was used to represent the surface material of magnetic shield of the recording head. The wettability of lubricants were measured on NiFe surface by contact angle measurement technique to show the selectivity on each NiFe. The results were compared with the atomic force micrograph of material after lapping process and show that the selective removal of material can be occurred by this method

Experimental Investigation into Vibration Characteristics for Damage Minimization in a Lapping Process

Lapping machines are used in a hard disk rough lapping process where a workpiece (a wafer row bar) is locked with a robot arm and rubbed on a lap plate. In this process, the lap plate’s condition and lifetime are among important concerned factors. The lifetime can be too short due to the plate being accidentally scratched by the workpiece during lapping. This problem leads to undesired consequences such as machine downtime and excessive plate material usage. This paper presents an experimental investigation into vibration characteristics of passed and failed lapping scenarios and discusses a potential solution to minimize the serious damage so-called “plate scratch” which intermittently occurs in such process. The experimental results show that, by in situ monitoring vibration and utilizing artificial intelligence, damage minimization can be possible