A joint test conducted by researchers of the U.S. Air Force Research Laboratory, Oak Ridge National Laboratory, Ball Aerospace & Technologies Corporation, Brigham Young University, U.S. Army RDECOM-ARDEC and nScrypt, Inc.’s research arm, Sciperio, used two types of 3D printing technology to compare the mechanical and thermal resilience of different materials for printing electronics for harsh conditions.

The two 3D printing technologies used by the team were an nScrypt Factory in a Tool (FiT) platform outfitted with a SmartPump microdispensing tool head and a powder bed fusion laser projection technology developed by the University of South Florida called large area projection sintering (LAPS).

Using the two technologies, the team printed a simple electronic device with a conductive trace and hollow cylinder representative of printed electronics packaging that would survive harsh environmental conditions. The nScrypt system was the primary manufacturing system and the LAPS system manufactured a subset of samples for comparison. 

The tests followed military standard 883 K and included resiliency evaluation for die shear strength, temperature cycling, thermal shock and high G loading by mechanical shock. The project assessed the ability of printed electronic multi-material systems to meet harsh environmental conditions typical of qualification requirements in traditional electronics packaging.

The electronic device consisted of a cured conductive paste circuit (DuPont CB028) on a substrate and a packaging cylinder without a cap. The nScrypt SmartPump was used to microdispense both the CB028 for the conductive circuit and master bond (MB) SUP10HTND epoxy for the packaging cylinders. A subset of packaging cylinders was sintered with Nylon 12 using LAPS.  

The team chose Kapton® and FR4 as substrate materials because they are both commonly used in the electronics industry and provide a flexible and rigid substrate, respectively.

Results indicated that DW MB epoxy devices made with the nScrypt FiT show resilience to extreme temperatures, thermal shock and mechanical shocks while also surpassing the die shear strength failure criteria specified by the military standard. The LAPS sintered Nylon devices also showed mechanical resilience to thermal shock and surpassed the die shear strength failure criteria. However, there were some open circuits, increases in resistance, and delamination when LAPS Nylon devices were subjected to extreme temperatures and 20,000 G shock loading normal to the substrate. 

Table 1: Coefficient of Thermal Expansion (CTE) for Materials Studied