Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Carolyn R. Duran, Apple Inc.

Oh, The Things We Build! What Materials Research Looks Like at Apple

Written by Molly McDonough

How does a $2 trillion company, like Apple, develop the best materials they can for the products they make? This question is exactly what Carolyn Duran, Senior Director, Product Integrity at Apple, discussed during her talk Oh, The Things We Build! What Materials Research Looks Like at Apple. Within Apple’s hardware engineering teams there is significant focus on the impact of materials on product development. Teams, including Duran’s, work to improve the durability, recyclability, and reusability of the other two billion Apple products that are currently in use. Duran’s talk focused on three materials use cases: glass in iPhone screens, aluminum used for MacBook casings, and plastics used in keyboards.

Testing for materials durability for glass in iPhone screens focuses primarily on determining how the glass fractures, and how to reduce the likelihood of fracture. The failure analysis falls into four broad categories: mechanical, optical, scratch, and coating durability. By tuning the crystallinity of the glass through glass cooling and promoting nucleation and crystal growth through the annealing process, the microstructure of the cover glass can be modified to decrease the likelihood of fracture. Additionally, the team at Apple worked with corporate partners, like Corning, to optimize the chemical strengthening process of the glass. By using ion exchange, one can encourage compressive stress in the glass at the surface, leading to the closure of fractures. This work resulted in a four times reduction in failures in the field with ceramic glass going from iPhone 11 to iPhone 12.

Next, Duran focused on how the alloy compositions of aluminum used in MacBook laptops have changed over the years to improve durability while maintaining the look and feel Apple users know and love. Apple uses 6000 series aluminum alloys for their MacBook products, which are fabricated using an extrusion/sheet process followed by precipitation strengthening. This is followed by aluminum anodization, which is an aqueous electrochemical process that oxidizes the surface to form an amorphous Al₂O₃. This leaves the surface porous, alloying it to be dyed to various colors.

The alloy team set out to find a new aluminum alloy that was more durable than the previous version by leveraging computational materials science to analyze material yield and solubility for hundreds of alloys. From the hundreds of alloys, the team picked the 10 best alloy options. From this, two alloys made it to product testing, and additional modifications were made following this testing. The new material passed Apple’s qualification process in less than six months, and led to a 30% increase in strength.

Lastly, Duran discussed how Apple improves plastics used in keyboards. Apple’s keyboard keys consist of four layers: top hard coat for protection, a color coat, a base coat for opacity, and a tinted diffuse substrate layer for glyph color and light scattering. Quality and durability issues commonly arise in keyboards, like top coat staining, glyph transmissivity, and side wall light leakage. The top coat staining issue was reduced by testing various solvent- and water-based solutions. The team found that solvent-based low volatile organic compounds showed the lowest color change due to chemical staining.

A large part of the materials development at Apple also focuses on minimizing the environmental impact of manufacturing Apple products. The company focuses primarily on reducing its impact on the climate, utilizing resources that can be recycled, and focusing on smart chemistry, meaning using chemicals that won’t end up as “forever chemicals” in the environment. For example, Apple has reduced the amount of CO₂ produced from their anodization process by over 72% by utilizing ELYSIS™ technology. Apple has also transitioned to utilizing more recycled and reusable materials, including reducing the plastic in their packaging by 18% since 2015.

Apple has put a large stake into using materials science and engineering to solve real-world problems for their customers.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.