Advanced Adhesion Strength Testing Methods of Thin Film Multilayers in Electronic Packaging Systems

With the continued miniaturization and increasing performance of electronic devices, new technical challenges have arisen. One such issue is delamination occurring at critical interfaces inside the device. This major reliability issue can occur during the manufacturing process or during normal use of the device. Proper evaluation of the adhesion strength of critical interfaces early in the product development cycle can help reduce reliability issues and time-to-market of the product. However, conventional adhesion strength testing is inherently limited in the face of package miniaturization, which brings about further technical challenges to quantify design integrity and reliability. Although there are many different interfaces in today's advanced electronic packages, they can be generalized into two main categories: 1) rigid to rigid connections with a thin flexible polymeric layer in between, or 2) a thin film membrane on a rigid structure. Knowing that every technique has its own advantages and disadvantages, multiple testing methods must be enhanced and developed to be able to accommodate all the interfaces encountered for emerging electronic packaging technologies. For evaluating the adhesion strength of high adhesion strength interfaces in thin multilayer structures a novel adhesion test configuration called “single cantilever adhesion test (SCAT)” is proposed and implemented for an epoxy molding compound (EMC) and photo solder resist (PSR) interface. The test method is then shown to be capable of comparing and selecting the stronger of two potential EMC/PSR material sets. Additionally, a theoretical approach for establishing the applicable testing domain for a four-point bending test method was presented. For evaluating polymeric films on rigid substrates, major testing challenges are encountered for reducing testing scatter and for factoring in the potentially degrading effect of environmental conditioning on the material properties of the film. An advanced blister test with predefined area test method was developed that considers an elasto-plastic analytical solution and implemented for a conformal coating used to prevent tin whisker growth. The advanced blister testing with predefined area test method was then extended by employing a numerical method for evaluating the adhesion strength when the polymer’s film properties are unknown.

An Investigation into the Efficacy of a pH-Sensitive Material for Milk Spoilage Detection

Ambiguous expiration dates on milk cartons can mislead consumers into prematurely disposing unspoiled milk and potentially drinking spoiled milk. These misconceptions can lead to wastage that harms the environment, or potential discomfort and illness. The incorporation of pH-sensitive indicators into plastic milk cartons has the potential to replace stamped expiration dates as the traditional method of milk spoilage indication. We studied the correlation between bacteria count and milk pH to establish pH measurement as an effective indicator of milk quality. We then developed a method for incorporating bromothymol blue, a pH-sensitive color-changing dye, into a hydrogel made of polyacrylamide. This hydrogel can be added to existing packaging for milk or other products with detectable pH changes. Additionally, we conducted a consumer survey and analyzed current food packaging trends in the market. Our research indicates that a spoilage-indicating milk carton could have strong market potential as food industries increasingly adopt intelligent packaging designs.