By the 1960s, the earlier version of magnetic storage, the
IBM drum storage was approaching its storage limit. Hand-made and assembled copper-wired heads were becoming too small to become extendible to smaller size and scalable to higher areal density storage per square inch. The challenges to extend the storage technology at that time were: 1, to achieve areal density beyond 3 Megabits per square inch; and 2, to batch fabricate the read/write heads. Romankiw invented several key inventions that enabled the extendibility of the magnetic storage technology. 1. US patent 3,908,194, Integrated magnetoresistive read, inductive write, batch fabricated magnetic head. This is the design of an integrated thin film head, which includes both the read and the write functionality, and which remains largely unchanged for decades. More details see
Disk read-and-write head. 2. US patent 4,295,173, Thin Film Inductive Transducer. This is the design of the writer in the thin film heads, where a magnetic yoke made with specific magnetic materials (
permalloy) is magnetized with copper coils. The design of the structure allows for high frequency switching and high magnetization at the yoke tip, which enables high frequency data writing with high fidelity. 3. US patent 3,840,898, Self-biased Magnetoresistive Sensor. This is the design of the reading part in the thin film heads. This design allows the miniaturization of the magnetoresistive sensor, which reads in 1 or 0 data on the storage media. 4. US patent 4,281,057, Variable Pre-spin Drying Time Control of Photoresists Thickness. 5. US patent 4,315,985, Fine-line circuit fabrication and photoresist application thereof. 6. US patent 3,853,715, Elimination of undercut in an anodically active metal during chemical etching. These three patents above invented and enabled the so-called "
Electroplating through mask", where the electroplated parts are well defined with patterned
photoresist using
photolithography. This is also an early version of the
LIGA process used widely for
MEMS fabrication. This innovative process was a key enabler for the fabrication of the thin film heads. 7. US patent 3,652,442, Electroplating cell including means to agitate the electrolyte in laminar flow. This is the instrument Romankiw invented to allow him to make the magnetic film for thin film head. This cell uses an innovative means to agitate the solution, with a reciprocating paddle, to provide
laminar flow agitation with uniform and well controlled
diffusion layer thickness. This enables the precise control of the composition of
permalloy and other
magnetic alloy film in a manufacturing scale. This tool also allows the application of an external magnetic field during
electroplating that creates
magnetic anisotropy in the film during deposition. The correct orientation of the
magnetic easy axis with respect to the magnetic yoke configuration is a critical requirement for fast switching of the magnetization and fast writing. 8. US patent 5,516,412. Vertical Paddle Cell. This is a follow on invention of the previous one, also with a reciprocating paddle for electroplating, but in a vertical configuration, enabling easier and faster loading / unloading of wafers, and also avoiding particle dropping from anode. 9. US patent 4,102,756. Nickel-iron (80:20) alloy thin film electroplating method and electrochemical treatment and plating apparatus. This is the
permalloy thin film electroplated using Romankiw's plating cell and process. This alloy has been the material of choice for
Disk read-and-write head for decades until the early 2000s. 10. US patent 4,003,768, Method for treating magnetic alloy to increase the magnetic permeability. This is the method of thermal annealing the electroplating permalloy in a magnetic field to further improve the permeability in the easy axis, to further improve the magnetization, magnetic switching, and the writing performance. In addition to the thin film heads, Luby's inventions also contribute to the
controlled collapse chip connection, or the
flip chip packaging technology for computer
processor,
copper interconnects,
advanced packaging,
thin film solar cell, and on-chip
inductive power convertor. == Awards ==