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.