Thermal Testing Quality Assurance of 24LCC & 3LCC Electronic Packages
- Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)
The purpose of this project is to experimentally validate the thermal fatigue life of solder interconnects for a variety of surface mount electronic packages. Over the years, there has been a significant amount of research and analysis in the fracture of solder joints on printed circuit boards. Solder is important in the mechanical and electronic functionality of the component. It is important throughout the life of the product that the solder remains crack and fracture free. The specific type of solder used in this experiment is a 63Sn37Pb eutectic alloy. Each package was manufactured with conformal coating along with and without an underfill material below the device. Conformal coating helps protect the board from environments such as electrostatic discharge and humidity. It is commonly used in broad types of engineering disciplines such as commercial, military, research and development, etc. Conformal coating can also pose a risk for the life of the board because of its high thermal expansion coefficient. This can greatly decrease the life of the product if it regularly sees high temperature variations. This leads to a shorter fatigue life of the solder. The fatigue life is a common mechanical problem in the field of electronic devices. Adding underfill can help increase the fatigue life of the solder. However, applying underfill adds time to manufacturing and production. This ultimately increases the cost per unit. The study of conformal coated printed circuit boards with and without underfill was done on two different surface mount electronic packages. The electronic packages studied were 24 and 3 contact Leadless Ceramic Chips packages. When the package was not underfilled, the coating was allowed to flow underneath. The assembly was analyzed and tested to obtain the best available combination of conformal coating, underfill, and potting to design the most robust and reliable circuit board while keeping in mind certain factors such as cost, manufacturing time, and need. Different types of conformal coatings were considered with and without underfill for each device. 29 of each component were manufactured to have a large sample size and for the sake of individual defects and imperfections. Finite Element Analysis (FEA) was performed by an engineer at Sandia National Laboratories for both Leadless Ceramic Chips. From the FEA results, a test acceleration profile was derived and the number of temperature cycles to fail the solder interconnects were found for three different cases. Experimentation was done as a secondary measure to validate this data to show confidence in the theoretical analysis. Accelerated testing functions as a quality check for the product. Accelerated testing is extremely useful in the research and development phase of engineering. It can save money from the potential of early life defects and the costs that come along with warranties. Accelerated testing makes a weaker design more robust and checks the reliability of a strong design in a shorter period of time. It is extremely helpful in a world where deliverables are in high demand and scheduling is tight. Accelerated testing helps the engineer gain an understanding of what needs to be improved and what works well. There are many different types of accelerated tests. Our circuit boards were accelerated inside a closed thermal chamber because of the high number of use cycles. The ultimate goal of this experimentation is to help identify what will prevent any premature cracking or fracturing in the solder alloy. It is important to understand that underfilling each component may or may not be needed. If underfill is not needed, there are several production benefits.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 1561196
- Report Number(s):
- SAND-2016-3058R; 637663
- Country of Publication:
- United States
- Language:
- English
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