A hard disk drive (HDD) assembly includes several key components: disk, head stack assembly (HSA), dual-stage assembly (DSA), head gimbals assembly (HGA), slider head assembly, pre-amp on flex assembly and VCM assembly. These assemblies need many component attachments with adhesive and Nordson ASYMTEK offers fluid dispensing systems ideal for these HDD manufacturing and assembly processes
PZT attachment for DSA
DSA is embedded on HGA to adjust the slider head position precisely on the disk. PZT is the actuator to move the head slightly. Two PZTs are attached on HGA with die attach material. PZT size is around a millimeter size, and the die attach material thus has to be aimed to a-few-hundred-micron target, and multiple locations with a few hundred micron apart. The material dispensing is to be quite accurate, small dots and precise short moving.
The PZT needs interconnection with conductive paste (silver epoxy). Because of the PZT size, the paste dot also has to be small down to a few hundred microns: same challenge as PZT die attach material.
Head Stack Assembly (HSA)
Head stack assemblies have fine flex circuits to transfer the signals from slider head to pre-amp. The circuits are set into the small channel on the arm to avoid air friction with UV-cure adhesive. The arm is thinned down to 700 microns for denser HDD, so the channel on the arm is even narrower. Dispensing the adhesive on the channel must be precise.
Pre-Amp on Flex Assembly
Pre-amp should be closer to the slider head to diminish noise. The pre-amp (flip chip) is located on flex circuits because they can be attached to the HSA. Flip chip needs underfill. Unlike rigid boards, flex circuits are "flexible". During underfill dispensing, fiducial detection is the key to the correct dispensing location.
Key fluid dispensing applications that serve the HDD assembly industry:
● Die-attach and silver epoxy dispensing for PZT attachment
● UV-cure material dispensing for flex circuits tail tacking
● Underfill dispensing for flip chip