What Is an Optical Pickup Bobbin?

Optical pickup bobbins are critical components used in the following devices: optical disc reading units for music CD and CD-ROM and DVD-ROM for PCs, and optical disc reading/writing units for music CD-R/RW discs and DVD discs (i.e., optical disc drives and optical disc recorders).
Optical disc drives are able to perform data reading and writing operations by applying laser beam onto minute pits on the disc, with dimensions in the μm (1/1000 mm), that have been engraved into optical discs. When reading and writing data, the focusing lens itself must be moved at extremely high speeds, using magnetic forces, in order to be able to focus the laser beam onto the correct sections of the disc, as it rotates at high speed. Coils are utilized to provide the magnetic force to move the lens. The lens is mounted on top of the optical pickup bobbin, as shown in the figure below, thus the bobbin can also be referred to as the "lens holder."

Figure 6-3-1 Structure of Optical Pickup Bobbin

Characteristics Required of the Material

The characteristics required for optical pickup bobbins are as follows. SUMIKASUPER LCP, which satisfies these characteristics, is widely used in optical pickup bobbins.

Table 6-3-1 Required Characteristics of Optical Pickup Bobbins and Characteristics of SUMIKASUPER LCP

Requirement	Reasons of the requirements	Characteristics of SUMIKASUPER LCP
Small size and light weight	For power saving and high sensitivity	Low specific gravity
		Formability that enables precision molding
Reading signals accurately	If resonation occurs at less than the operating frequency (up to 20kHz), the signal can not be read. The resonant frequency of low specific gravity and high rigidity material is high.	High rigidity (Flexural modulus at 0.5mm thickness = approx. 30GPa)
		Low specific gravity
Low cost	Can be mass-produced through injection molding. As dip soldering can be performed during the assembly process (350 to 400°C x several seconds), the process of inserting metal terminals is no longer required as cost.	Formability that enables precision molding
		Low specific gravity

Grades of SUMIKASUPER LCP for Optical Pickup Bobbins

Of SUMIKASUPER LCP grades, the E5006L and E5008L grades are suitable for optical pickup bobbin applications.
The standard grade E5006L is the most suitable grade for pickup bobbins.
The E5008L is recommended for CD-DA (for audio) and low-speed CD-ROMs.