Ultem (PEI) Diffusion Bonding Manifolds

Ultem (PEI) Diffusion Bonding Manifolds

March 2023

Ultem, Polyetherimide (PEI) has long been renowned as having superior properties for high temperature operation, excellent chemical resistance, and biological compatibility.  Now the trend to use Ultem for fluidic manifolds and especially diffusion bonded versions, is on the rise. This is being driven by the growth in applications such as medical diagnostics, DNA sequencing and diverse life science equipment solutions.

Ultem’s chemical resistance is particularly beneficial if the fluidic manifolds are being sterilised using aggressive cleaning fluids and processes. It can also stands up well against other forms of sterilisation like autoclaving and Gamma radiation. Ultem’s biocompatibility properties are suitable for most sensitive applications in these fields.

Originally developed by General Electric Company in 1982 under the trade name Ultem, it is an amorphous thermoplastic, amber to transparent in colour.  It is often used as a replacement material for Polyether Ether Ketone (PEEK) due to its availability, price & performance characteristics plus the ability to bond layers of Ultem to itself to create complex manifolds.

 

Carville has been using their unique, High Accuracy Diffusion Bonding (HADB) method and precision CNC machining expertise to produce Ultem Manifolds for over 20 years. Carville’s bonding method ensures the tight tolerances (typically +/-0.05mm) of the pre bond CNC machined features are maintained throughout the bonding process, so, that they can be aligned accurately with the post bond CNC features.

The process also allows microfluidic channel sizes down to 0.15mm width and depth to be maintained. Carville’s bonding process can produce large footprint fluidic manifolds over 450mm x 450mm, with multiple layers.  These HADB manifolds offer a very high degree of design flexibility for fluid management, including multiple subsystems in a single, highly repeatable component, analogous to a PCB.

When working with Ultem, it is vital to have a robust heat treatment regime before and during manufacture.  This will help to ensure that the material will hold its dimensional accuracy, diminish any opportunity for cracking/crazing and warpage.

When Ultem is first extruded, the material is in a highly stressed state. Therefore, significant normalisation heat treatment, close to the material glass transition temperature, is essential before any mechanical processing. Subsequent machining processes will stress the material again, so additional annealing steps during manufacture are also required to relieve this. Heat treatment is particularly important when manufacturing diffusion bonded manifolds, as the parts go through several machining, diamond milling, bonding and polishing steps, which all add stress.

When considering Ultem for a manifold, the design will require careful attention to detail. It is important to avoid any high mechanical stress points in the final application.   Layer thickness and features need to be optimised, as well as avoiding sharp angled stress points. The use of metal threaded inserts is an effective way to reduce the potential stresses when screwing in components.

Carville directly support the design and manufacture of Ultem manifolds from our UK base for a wide range of companies, from start-ups to large corporations, especially in the USA and Europe.

For further information or to discuss an application, please contact Carville Ltd.

sales@carville.co.uk

www.carvilleplastics.com

Tel +44 (0) 1306 881681