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Panasonic Corporation
Thermal Fluid Analyses for the Design of the World’s Smallest Optical Disc Drive

The market of optical media, such as DVD and Blu-ray disc drives, is competitive. Demand is high, and customers expect lower prices and further miniaturization. Panasonic Corporation uses thermal fluid analysis during product development to maintain temperatures below hardware durability limits, even under extreme operating conditions.

Fig 4 Optical head structure of ultra slim Blu-ray disc drive (9.5 mm thickness) and simulation example
Overall mechanism structure (upper left) and optical pickup (lower left). Click to enlarge.

Development of the First Ultra Slim Optical Disc Drive

 scSTREAM was used for the development of an ultra slim optical disc drive for laptop computers. Panasonic developed this industry-first drive (fig 4). Successful development of an ultra slim optical drive requires keeping the designated size and simultaneously maintaining the heat dissipation capability of a high-power Laser Diode with three different wavelengths.

 Reducing the temperature of a Laser Diode in a small drive is challenging because the temperature tends to increase in smaller spaces, and less surface area is available for heat dissipation. Blu-ray disc players use a blue Laser Diode with a 605 nanometer wavelength to generate a 0.1 micrometer laser spot on the disc surface. This requires the ability to focus the light with very high accuracy. For this reason, errors in optical systems, which can be caused by deformation of parts due to heat generation and declination of optical axes, must be minimized.

​Fig 5 Analysis example of a Blu-ray disc drive by using scSTREAM.
Only showing the heat-emitting components (laser-driven Blu-ray disc, DVD, and CD drives, and IC chip). The diagram on left shows the status before implementing the countermeasures, and the diagram on right shows countermeasure effects.

 The heat sources of the optical pickup are the Laser Diode, the Laser Diode Driver (LDD), and the object lens driver, which is activated by magnetic coils that emit heat. If the object lens temperature rise is uneven at different locations, the lens will deform and the size of the laser spot will change. This can ultimately alters the quality of the recording or the played output. Therefore, the one thermal goal is to maintain a uniform inside temperature distribution. An analysis of the inner temperature during drive operation is shown in fig 4. The heat source is shown in fig 5. As shown in the figure, the Laser Diode and LDD temperatures have been decreased by implementing thermal control measures. A steady-state analysis of an optical disc requires a detailed mesh with 20 to 100 million mesh elements. This level of geometrical resolution is necessary to capture the extremely small gaps between components.​

 In 2011, Panasonic released a recorder with a 100GB hard drive using a multilayer optical disc drive. Thermal control became more complicated for the multilayer disc. Concurrent with the pursuit of drive miniaturization, Panasonic engineers used scSTREAM to adjust designs to achieve heat conduction and dissipation targets that maintained the operational temperature of the Laser Diode at the target values.

Applying SC/Tetra for Dust Dispersion Analysis

 Panasonic has also undertaken research and development on a high-capacity data archiver that uses optical discs. A high-capacity data archiver is often used in data centers to store an immense body of data such as movie files. Panasonic engineers were looking for a convenient way to record/replay with greater recording density compared to Blu-ray disc drives. They used SC/Tetra to conduct dust dispersion analyses inside the chassis.

 Mr. Nakata explains that accounting for dust dispersion in recording systems was never thought necessary until recently. However, a high-capacity data archiver can be easily affected by small, nanometer sized dust particles, because of its greater recording density. Since performing maintenance inside the chassis is unrealistic, understanding the dust dispersion patterns within the device makes it possible to modify the design as needed. SC/Tetra was also used to conduct transient analysis of varying dust concentration over time.

SC/Tetra was used to both estimate varying dust concentrations over time and design the dust collection system. Fig 6 shows a dust collection system design that uses filters. Dust particles larger than 10 nanometers on the recording head would likely lower the device's reliability. A filter was installed for removing dust particles, and it was modeled in simulation such that half of the dust particles larger than 0.1 micrometers are removed each time they pass the filter. Panasonic engineers performed the thermal fluid/particle analyses to evaluate how effectively dust could be removed over a period of time. The results showed that the dust clearance time increased by a factor of 9 when the clearance volume doubled.

Fig 6 Dust dispersion analysis example of a high-capacity archiver by using SC/Tetra.
Color bar indicates the level of concentration.


Utilizing Heat without Waste

​ Panasonic is also using the thermal fluid analysis tools to design a fuel cell cogeneration system. A fuel cell is designed to generate power using the energy generated from the chemical reaction between extracted fuel bound hydrogen and oxygen in the air. A household fuel cell cogeneration system uses hydrogen from urban gas and oxygen in the air to generate power. Cogeneration means to generate multiple forms of energy. For the household cogeneration system, hot water can be supplied simultaneously using by-product waste heat.

​ To further improve the overall system’s energy efficiency, energy generation efficiency must be improved. This requires strict control of the thermal design to minimize heat. “Fuel cell system design must consider cost, size, capability and durability,” says Mr. Nakata. This is where the application of thermal fluid analysis comes in. With the current system design, Panasonic engineers perform thermal fluid analysis to determine the best layout for each component, evaluate different flows, observe the heat exchange, and calculate the heat balance.

Moving to More Integrated Analyses

 Panasonic engineers hope that chemical calculations such as catalysis reactions and combustion models will soon be implemented into Cradle analysis tools as optional functions. By identifying the heat generated in the chemical reaction and understanding the combustion phenomena, analysis of the entire fuel cell system can be more integrated.

 Cradle software has been used to help design many Panasonic products. Panasonic engineers are eager to continue to apply the analysis tools to a wide range of energy related products that is sure to lead to more effective product development.

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of April 30, 2014 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.

 

Company Details









 

Panasonic Corporation
Founded December 15, 1935
(after changed from Matsushita Electric Housewares Manufacturing Works to Matsushita Electric Industrial)
Business Manufacturing general electronics products and components for  home appliances, factory automation, Information Technology (IT),  and related services
Representative Kazuhiro Tsuga, President
Location of Head Office Kadoma-shi, Osaka, Japan
Capital 258.7 billion JPY
​(as of March 31, 2014)

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