Heads & media: Integrated electronics
The 2012 INSIC Tape Roadmap forecasts a fifty percent increase in data rates every two years or essentially with each new generation of tape drive. This is expected to be achieved through a combination of an increase in the number of parallel channels as well as through increases in linear density and tape speed that provide an increase in the data rate of an individual channel.
Both of these strategies give rise to specific challenges for the design of the head flex cable. First, increasing the number of transducers that operate in parallel leads to an increase in the number of copper traces that must be routed along the cable, resulting in an increase in cable cost, size, mass and stiffness. The increase in mass and stiffness can cause a degradation in the performance of the track-following control system.
Second, increasing the per channel data rate can be difficult due to the challenge of matching the impedance of the readers and writers to that of the cable and the analog front end electronics on the electronics card.
These impedance matching issues can limit the maximum bandwidth of the read-back process as well as the current switching time in the write elements which in turn limits the maximum write speed as well as impacting the quality of the written transitions and hence the SNR of the read-back signal.
Both of these challenges can be addressed by the integration of some of the front-end electronics directly on the flex cable adjacent to the head. Currently, we are investigating:
- the design and integration of a CMOS multiplexer directly adjacent to the head to select the active channels and reduce the number of conductors that must be routed along the cable and,
- the design and integration of a write driver circuit adjacent to the head in order to achieve faster write current switching times and at the same time reduce power consumption and heat dissipation, see Figure 1.
The close integration of the front-end electronics with the read/write transducers will potentially become one of the key enabling technologies to facilitate the continued scaling of magnetic tape-recording to higher areal densities and data rates.
Figure 1. A prototype write driver chip with C4 solder balls for flip chip attachment to flex cable.
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IBM Research Scientist
Figure 2. Front end electronics mounted on a head flex-cable. The chip is mounted using a flip-chip technology.