Ultra-thin Rohacell for smartphone speakers

Rohacell rigid foam from Evonik Resource Efficiency of Germany and Daicel-Evonik of Japan has been adopted as a core material for the ultra-thin composite diaphragms in smartphone receiver speakers by Yoneshima Felt headquartered in Osaka City, Japan.

A smartphone is equipped with two types of micro-speakers, the companies explain – a loud-speaker and a receive speaker, which deliver sound directly to the ear.

Today’s state-of-the-art smartphones deliver high output which can generate increased internal temperatures, so micro speaker diaphragms are now required to have high heat resistance. Miniaturisation of the receiver is also essential.

Using slicing technologies developed by Yoneshima Felt, Rohacell foam can be sliced into thin sheets that measure a mere 100 microns. Even at this extremely thin thickness, the foam core withstands high temperatures and contributes to superior sound quality by reducing the size and weight of the receiver diaphragm.

Rohacell foam is used worldwide as a core material in carbon fibre reinforced plastic (CFRP) sandwich applications, including aircraft bulkheads and interior structural components in high-performance passenger cars.

The ultra-thin composite diaphragm was awarded the Electrical and Electronic Components Award at the Urtla-Monozukuri Parts Award, sponsored by Nikkan Industrial News, in 2018.