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

Mr. Hideki Nakata
Energy System Development, Energy Solutions Center, Panasonic Corporation R&D Center Headquarters

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.


​ Panasonic is a general electronics company with businesses in home appliances including audio visual devices, industrial equipment, IT tools, business and household products, and energy/environmental products. In 2018 the company will celebrate its 100th anniversary.
 

​​Fig 1 Progress of optical disc drives
Panasonic has manufactured own optical disc drives from CD player  development. Click to enlarge.




Fig 2 Structure of optical pickup: consisting of a LD, object lens, actuator, and photodetector. Click to enlarge.

 Mr. Hideki Nakata, from the Blu-ray disc drive development task force at the Panasonic Corporation R&D Center Headquarters, has been involved in optical disc drive development since the time when CD drives were the dominant product in the market (fig 1). He has worked as a development researcher for optical pickups (fig 2), the main component of the optical disc drives, which read and write information. Mr. Nakata has also developed Mini Discs, DVD, and Blu-ray discs. He has applied thermal fluid analysis tools for the development of the optical pickup, a part of the drives where Panasonic has outperformed its competitors. Analyses have been used to determine the most effective thermal design of a high-power Laser Diode based on its thermal conductivity and radiation emissivity during conceptual design. Mr. Nakata was also the project leader of the ultra slim Blu-ray disc drive development, where he was in charge of research, design and establishing the manufacturing facility. Later he was part of the development team for a high-capacity archiver. In 2013 Mr. Nakata started working on the research and development of fuel cells. A fuel cell is designed to generate power by the chemical reaction between the hydrogen extracted from the fuel and oxygen in the air. Mr. Nakata has been using thermal fluid analyses to design the generator.

Fig 3 Determining the heat dissipation structure by using scSTREAM. Click to enlarge.

Improving Heat Dissipation in a Resinified Device Using Thermal Simulation

Panasonic first introduced scSTREAM, a structured mesh thermal fluid analysis tool, in 2005 when they were developing optical disc drives for Mini Discs. Mini Discs consist of a high-power 800 nanometer wavelength Laser Diode, which generates a micrometer laser spot onto the disc surface using small optical systems to read and write signals. “The design of optical disc drives must balance production cost, device size, capability and reliability, which often pushes each constraint to its limit,” says Mr. Nakata. Panasonic recognized the need to improve thermal design when facing the fierce competition in the portable Mini Disc market driven by lower prices and smaller size. Aluminum die casting had been used for the base component for the optical element, but was changed to resin to reduce cost. However, the resin did not conduct heat as well as the aluminum, which would have increased the temperature of the Laser Diode past its design limit, and devices would have been damaged. To avoid this, Panasonic utilized the convection caused by laser disc rotation to help cool the optical pickup more effectively.

Higher Demand for Less Prototyping

 Initially, the disc system product development process involved designing and prototyping, followed by testing to measure the Laser Diode temperature. If the temperature exceeded the safe limit, the engineers performed a redesign, produced another prototype, and revalidated the capability. This development cycle took three months. Completing the evaluation of each component and the overall structure could take up to two years to completely ensure the Laser Diode met its durability requirements. In a time when product development needs to be as short as possible, performing detailed thermal design early in the process and accounting for heat conductivity and emissivity in the analysis could significantly reduce the development time. Not only would development be faster but high product quality could also be maintained. Panasonic needed a highly accurate analysis tool with easy operability to enable them to make quick decisions about thermal design. They found scSTREAM could help them meet their requirements.


Constructing an Accurate Temperature Prediction Model

 Panasonic decided to use scSTREAM because “not only did it have a comprehensive variety of functions, but its interface was extremely easy to use compared to other tools,” says Mr. Nakata. Panasonic engineers found it convenient that 3D-CAD data could be directly imported into scSTREAM. Then the mesh elements could be generated without having to transform the geometry data into a different format. Setting the thermal contact resistance between components using data from experiments was also simple, as well as simulating the air flow generated by disc rotation.

 The Panasonic engineers report that, using thermal analysis, the Laser Diode temperature could initially be predicted in the early design phase within 5ºC. The analysis accuracy was improved to 1ºC, by making precise measurements of the thermal resistance between components during prototype experiments. By doing this, the thermal design was completed by the second experiment, which also served to double-check that the measured values were as predicted. The Panasonic engineers said that by performing the thermal analysis the design period has been reduced to a half year. In addition, they are also able to accurately anticipate temperature variations under different operating conditions prior to the actual production. They have also been able to apply the analysis method developed for the Mini Disc drive to the miniaturization of their DVD and Blu-ray disc drives.

*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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