Design Engineering
Showcase 2021


Product Design
FATP Assembly
Failure Analysis

Project Details

Ruidun Li
Audio Product Design
Dr A. Freddie Page
In-Region Product Design Intern
Retail and Consumer Goods

My placement at Apple as an in-region product design intern entailed the opportunity to make meaningful contributions to the New Production Introduction (NPI) process of a future audio device. This experience gave me great insight to how the company approaches product development through validating design concept feasibilities, establishing assembly processes, and conducting failure analysis(FA) to design corrective actions. These learnings from supporting and solving design issues throughout build stages eventually led to my most critical work that helped unblock a key design hotspot for the program.


Demonstration of Design Engineering Thinking and Skills

Understanding of NPI

Apple follows a rigorous and extensive product development process that result in the output of a high standard product for the customer. From a product design point of view, the program first starts out from early architecture and undergoes a convergence process during each build stage. For a part design within the system to be locked down and rolled in as the Process of Record (POR) for production, a product designer must demonstrate that the concept is capable by design, process, and reliability. Such validation process requires a demonstration of design engineering thinking and skills.

Design Concept Down-selection

A flurry of actions, including tolerance analysis, actual fit checks, and design of experiments, are required to gain sufficient data to improve one’s confidence in a part design for the system. For example, the sensor sealing design of the product required a pressure sensitive adhesive to prefix the module to an enclosure and, using tolerance analysis, underwent multiple geometry iterations to reach an acceptable CPK value (process capability index) that took account of the pick-and-place equipment capability. To select the most optimum material for this adhesive, I 3D-printed specially designed fixtures for fit simulations and initiated DOEs to gather their expansion data after thermal conditioning, subsequently conducting data analysis to down-select the final material option.

Assembly Process Bring-Up

To bring-up the assembly process for the design, I developed a range of methods to verify if the assembly was nominal. This included attempts to quickly visualize the assembly through X-ray scans, CT correlation mapping, red-dye or bubble testing to validate air-tight sealing and the effort to quantify observations, such as grid mapping for glue curing conditions or pull force baseline establishments.

Reliability Test Failure FA and Corrective Actions

Root-causing for failures in reliability tests is a key activity during product development and guides the design of corrective actions. One example would be using FEA to understand the deflection of parts in the system for failures in mechanical drop testing, which led to experiments of using low modulus adhesives to act as stress relievers.

stages of NPI
Work flow from design concept to production

Role and Contributions

As an in-region product design (PD) intern at the Audio PD team, I worked at the NPI assembly site together with our Cupertino counterparts to develop the system design for a next generation Apple audio device. Responsibilities on the in-region members are even greater this year as we had to clearly communicate everything that is happening on the ground to our Cupertino teammates, who remained across the Pacific due to travel restrictions. Each member of the PD team is responsible for specific parts in the system and carries out concept feasibility evaluation, assembly process establishment, and failure analysis to validate if their designs are ready for production. In addition, the PD team is at the heart of the cross-function collaboration scene and I had to work with Technical Operations to develop processes and fixtures, Product Quality Management to ensure consistent production quality, and function teams such as Sensing or Acoustics on subject-specific issues.

My most critical contribution involves the sealing design and assembly of the optical sensor module on the product, where corrective actions that I helped develop reduced the Defective Parts Per Million rate by up to 96%. I also worked on supporting other parts in the system, such as acoustic driver assembly and enclosure environmental stress cracking. Apart from making impact to the NPI program, I also worked on establishing a database with my manager for the in-region team to document past project experiences, hoping that it will become a useful reference for old and new hires in the future.

Airpod role


My placement allowed me to understand and participate in the long and winding road that is product design. It gave the opportunity to connect the dots of engineering knowledge and methodologies learnt in university with real-world projects in the industry. Knowing that the product you worked on will be in the hands of millions is genuinely an exciting feeling and will most definitely serve as motivation for me to pursue my areas of interest in future studies and career.