Contact Angle Measurement to Detect Damage on Hydrophobic Surfaces

GenMark Dx is a molecular diagnostics company focused on multiplex tests that diagnose complex medical conditions. GenMark's eSensor technology is based on DNA hybridization and electrochemical detection. The ePlex platform is capable of performing sample-to-answer assays involving nucleic acid extraction, reverse-transcription polymerase chain reaction (RT-PCR), and multiple target detection. For these reactions to take place, a highly hydrophobic coating on a Printed Circuit Board (PCB) is required. The current method for detecting damage on the PCBs is time consuming and has a high scrap cost. The goals of this project were to determine an alternative non-destructive quality control test to detect damaged PCBs. The contact angle is measured by distributing a small droplet (2 μl) of liquid onto the surface to be measured. An image of the droplet is captured using a high-resolution camera, which is used to measure the contact angle. The contact angle is calculated from the drop volume and diameter. Based on experiment results, undamaged coating had average CAs 65°, and damaged had average CAs 60° and below. T-tests were used to compare the two test conditions. The contact angle measuring process is non-destructive and is capable of distinguishing damaged from undamaged hydrophobic coating. A low contact angle indicates damage, while a high contact angle indicates an undamaged hydrophobic surface. A contact angle that is above 60° can be considered undamaged, and a contact angle that is below 60° can be considered damaged.