Stabilising images for mobile devices

4 September 2019

Ninety per cent of people in developed countries now own a smartphone, according to professional services multinational Deloitte, and they rely on the tiny cameras in these devices to deliver optimal images.

That requires sound adhesion of the components, and the same is the case for every mobile device that contains a camera, from sensors in self-driving vehicles to drones and security systems.

Dr Cheung Kwok-yuen (Croucher Scholarship 2004) is working to make sure that this happens. He is a technical manager for ASM Pacific Technology Ltd, which manufactures systems used in the mass production of electronics all over the world. He is currently involved in the development of the company’s die attach and lens holder attach machines that will produce better camera modules for the millions of people who use them in their phones, and for many other devices.

Cheung, who grew up in Hong Kong, earned his bachelor degree in Chemical Engineering at Hong Kong University of Science and Technology (HKUST) in 2000, followed by an MPhil in 2002. He then moved to Japan to work as a research engineer at Mitsubishi Chemical Corporation.

In 2004, he moved to the UK, to undertake a PhD at Imperial College London, supported by his Croucher Foundation Scholarship. His research focused on petrochemical facility optimisation for continuous chemical processes. Using simulations and modelling, he was able to analyse and remove free variables found in different levels of manufacturing.

After finishing his PhD, Cheung returned to Hong Kong with his wife, Susanna Wan (also a Croucher Scholar), where he was hired by ASM Pacific Technology Hong Kong Ltd. “When I started, they called my position, ‘process engineer’,” he explained. “I had to have a mindset to tackle problems with the machines that use epoxy to adhere sensors to their chips.” Cheung’s prior chemical engineering knowledge and experience with optimisation complement his role in developing camera gadgets.

Cheung’s work is critical for the progression of camera modules, robust instruments capable of enabling tasks ranging from photographic imaging to facial and fingerprint recognition in security systems. These modules are also essential for providing 3D sensing and creating augmented reality systems, which can be used in anything from popular smartphone applications to self-driving vehicles.

The lens holder machine that Cheung developed involves a lens holder complex with an adhered image sensor circuit created from the die attachment process. The lens holder complex is a printed circuit board containing the hardware for the camera module. Using a bonding head, the machine attaches the image sensor to the complex, forming the finished camera gadget included in a smartphone.

This process requires immense precision and accuracy during the adherence stage. Any deviation of the sensor attachment from the holder may result in the camera module being unable to focus properly. This would result in a phone that could not take pictures or videos.

The die attachment machine in development by Cheung uses an adhesive bond approach to secure an image sensor to a semiconductor chip. Dies are small integrated circuits cut from a wafer containing other dies. Die bonding connects the integrated circuit to a silicon chip, the connection acting as a foundation for the rest of the manufacturing process.

Cheung’s patented design attaches an image sensor die to a printed circuit board using epoxy. The tool seeks to stabilise the orientation of the die when it is bonded to the circuit board while using enough epoxy to solidify the die’s placement. If not done properly, the camera gadget may not attach properly to other components and lose function over time. This could have serious consequences, for example, leading to fatal accidents in autonomous vehicles as such vehicles require sensors to work accurately to avoid obstacles.

Cheung reflected on the future of his role as a technical manager and process engineer. “Chemical engineering is very static compared with the mobile phone industry. We have to keep up with customer needs that change all the time.”

Dr Cheung Kwok-yuen obtained his bachelor and master degrees in Chemical Engineering at Hong Kong University of Science and Technology. After his master’s degree, he moved to Japan to work as a research engineer at Mitsubishi Chemical Corporation. In 2004, he was awarded a Croucher Scholarship for his PhD research on “Site-Wide and Supply Chain Optimisation for Continuous Chemical Processes” at Imperial College London. Cheung is now a technical manager at ASM Pacific Technology, Hong Kong. He leads a process engineering team to develop machinery equipment that facilitates the fabrication of camera modules used in different electronic gadgets. Dr Cheung received a Croucher Scholarship in 2004.

To view Dr Cheung’s Croucher profile please click here.