Medical-Grade Leak-Proof PCB Encasement - Flexible Material Technology

Ventana Medical Systems, a Roche Company, develops automated tissue
staining instruments to diagnose a variety of disease states, using an array
of technologies (Special Stains, H&E, In-Situ Hybridization, Immuno-Histo
Chemistry, …). Tissue staining instruments employ electromechanical
devices, and as such the staining reagents are in proximity to electronics.

A protective cover that meets an IP (Ingress Protection) rating for light
spray and drips, as well as is made from a material compatible with our fluids,
would provide modular protection and risk reduction to custom circuit
boards. By achieving the IPX4 rating, protection against ingress from
splashing chemical reagents from all directions is possible. It is tested by exposing
an item to an oscillating spray for a minimum of 10 minutes. Design passes when
there is limited ingress with no harmful effects. Currently our available
range of protection options are limited by two main factors.

Factor 1 is the serviceability of a protective cover to prevent fluids. Designs
containing rigid elements and added fasteners are not desirable nor
marketable. In order to design a solution for this, a flexible, self-sealing
housing and cover are envisioned. This closure would act much as a
waterproof cell phone case would, the soft plastic silicone type. employs a
“zipper” type or similar concept seal to allow the cover to close around the
PCB, with outlets for cable harness egress. In addition items will need to
pass through this encasement in order to mount and connect the PCB, so
a flexible material that can seal around the M5 mounting standoffs is
required.

Factor 2 is the material compatibility of soft silicone/elastomer type materials has not
been evaluated and as such reagent compatibility and best material(s) for purpose
are not known.