Flexible On-Chip Inductors and Transformer

Abstract

Inductors directly on-chip was designed, processed and tested. Combining thick, electroplated gold used to produce LCD driver ICs plus gold wire bonding, toroidal inductors are formed directly on top of ICs. Both processes are production ready. One layouts inductor line segments on top of ICs and then complete loops using gold wire bonds at packaging. Two, 4, 8 or 16 toroids will fit inside thin QFN package. Cost to integrate 2 or more inductors is less than buying 0402 chip inductors and then soldering SMT components around ICs. Integrating inductors shrinks PCB board and allows IC design of filters, LC oscillator, EM noise suppression or ESD protection circuits. On-chip 4nH to 2000nH inductors is practical today. Choosing the magnetic core material and selecting the number of loops/turns, designers can integrate different inductors on top of an existing IC. Custom, ultra-tiny magnetic cores are produced from same magnetic materials that are inside discrete inductors or transformers. 50nH to 500nH inductors with Q comparable to chip inductors are possible for MHz frequency ranges by selecting ferrite core. Using high permeability permalloy, one produces 200nH to 2000nH inductors or transformers directly on-chip. Flexibility is another advantage of on-chip Gold InductorsTM. By adjusting loop heights during wire bonding, one can adjust inductance value +- 100%. By laying out both primary and secondary coils around magnetic core, designers can choose to integrate transformer or inductors. Low cost, production processes, control with IC design, plus flexibility, one can begin to design and produce on-chip filters and transformers; achieving smaller electronics.