A hard disk drive incorporating rotating magnetic disks is commonly used for storing data in the magnetic media formed on the disk surfaces, and a magnetic recording head is used in hard disk drive to magnetically record information on a rotating disk.
Magnetic heads are typically constructed on a wafer that is sliced into separate row bars. Each row bar has a number of individual recording heads. The row bar is eventually sawed into individual elements and each individual element is assembled to a head gimbal assembly (HGA) of a hard disk drive.
Each magnetic head of the row bar is typically tested before being sawed into individual components to insure that the magnetic heads comply with manufacturing specifications. For example, a read head of the magnetic head includes a magnetoresistive (MR) element that has a MR height that must be lapped to achieve a predetermined value. Typically, the lapping quantity is determined by the resistance variety of the magnetic head before lapping and after lapping. The resistance of the individual slider after being lapped is required to be identical with the predetermined resistance value. Thus, the resistance of each slider on a row bar must be measured before cutting into an individual element within a tester.
A common tester for measuring resistance includes a probe card that has a plurality of probe pins which make simultaneous contact with the electrical lapping guide (ELG) pads formed on the surface of each slider cutting portion. The pins are coupled to a measuring board through a connector to make up a current loop with each slider on the row bar, as so to measure a resistance of each slider respectively. And the type of probe card is different which is determined by the types of the row bar. Nowadays, there are two kinds of typical row bars that include shunting-type row bar and femto-type row bar respectively. Inside the shunting-type row bar, one pole of each slider is connected together to form a connection common port, namely there is a connection common port shared with each slider on a shunting-type row bar. Inside the femto-type row bar, however, each slider is separated from each other in the internal connection.
Therefore, due to the different internal connections in two types row bar, a normal probe card is commonly used to measure the slider resistance of the femto-type row bar, and a shunting probe card is used to measure the slider resistance of the shunting-type row bar separately. The normal probe card has two rows of pins which are contact the two ELG pads formed on the cutting portion of the slider of the femto-type row bar respectively and a connector connected to the pins and coupled to the measuring board. While the shunting probe card only has a row of pins and a connector connected to the pins and coupled to a measuring board, one of the pins is supplied a voltage, and the rest of the pins contact the ELG pad formed on the cutting portion of the slider of the shunting-type row bar and is supplied another voltage, so as to form a current loop to obtain resistances of sliders.
Generally, the two said types of row bars are measured with a same measuring device to economize on cost. Thus, two types of probe cards will be disassembled and switched each other frequently, which the disassembly process is complicated and time-consuming. Thus, the downtime of the machine becomes longer, and the manpower is increased simultaneously. Moreover, the probe card will be damaged easily during the disassembly and switch process, in turn, shorten the life of the probe card.
Hence, it is desired to provide an improved method of measuring slider resistance of different types of row bar with a common tester to overcome the above-mentioned drawbacks.