#15 - Medical Imaging Sensor Packaging

The medical industry is experiencing exponential growth in everything sensors and the range of imaging sensors used in medical applications is wide:  from extra compact cameras (i.e. for endoscopes) up to huge x-ray sensor arrays, visible light over Infra Red (IR) to different tomography sensors like X-ray & CT, Ultrasonic, Magnetic Resonance (MRT), Positron Emission (PET) and others.  

As varied as the sensors are, we see diverse assembly tasks and bonding technologies:  full area bond to Focal Plane Arrays (FPA) with millions of bumps, micro optics assembly of endoscopes to placement of huge scintillator units with the highest co-planarity demands, and epoxy processes to reflow processes.  We have found that these applications have several packaging requirements in common:  the need for high precision (due to fine pitch), long term process stability and reliable conductive connections in micron or even submicron scale accuracy. 

As an example, bonding a large sensor array to a readout unit involves handling a large amount of bumps in the process.  Two electrical connections per sensor element are needed to process the signal.  A state-of- the-art, 1k x 1k pixel sensor array contains 2 million bumps.  To achieve good results, the bonding platform must offer extraordinary evenness of the entire system and keeping all parameters constant over a large area or distance can be very challenging. 

Considering that required bonding force increases with the amount of bumps, our customers are often faced with very high bonding forces.  High forces can easily lead to deformation of parts of the bonding system.  If the bonding system design is not optimized for maximum mechanical stiffness, the total value of all deformations will exceed the tolerable limits for low or medium force ranges.   Our bonders have the integrity to handle bonding forces up to 1000 N.  This, in combination with passive or active coplanarity control, provides an effective solution.

1/21/16

Keywords:  medical imaging sensors, medical device bonding, x-ray sensor array, focal plane array
Author: Bodo Kuhnert, Finetech GmbH

Spinner