Joining method in medical device assembly to offer greater possibilities

Last week, I posted an article about “proper joint-design for medical devices” that you can find here. I will today share more about how you can select the right joining method with a drawing.

Part size, flexibility, bond line geometries or material combination limit some of the assembly processes options. For example, it is difficult to use mechanical fasteners on tiny components or flexible materials cannot be joined by Ultrasonic Welding, or the majority of materials – including many newer substrates like TPE and TPU – show limitations when attempting solvent welding. Overall adhesives show the broadest versatility when assembling medical devices.

Two dimensions will need to be considered when looking at adhesive bonding versus solvent welding. I have drawn the different design options you can consider and materials:

Design Variations:

Material Options:

Considering both material as well as design option, adhesives are the best assembly option available. They allow fast, automated bonding of parts made from dissimilar substrates. Adhesives also fill gaps, distribute stress evenly over the bond line, and deliver a hermetic seal between parts. You can choose between a wide range of adhesive technologies, many of which offer flexibility in design and end device performance.

 The most common assembly methods for flexible substrates are solvent welding and adhesive bonding. Solvent welding delivers high bond strength through a relatively simple assembly process. It can be used on certain plastics, but is not appropriate for polyolefins, most TPEs, TPUs or combination of substrates.  In addition, solvent welding cannot accommodate large gaps and works best in tight fitting parts, see above (picture design variations).  Adhesive assembly allows for a wide range of substrates and combinations thereof, fills gaps and provides hermetic seals. See picture above (Material options).  You can choose between a wide range of adhesive technologies, many of which offer flexibility in design end device performance.

This blog is part of a series of blogs on medical device assembly innovation. Want to read more? Check out our series with blogs on “Flexibility in Medical Device Design” here and “Choosing the right material for your device” here.

Author: 

Esthefan Zumbado, Manager Medical Devices IA Latin America North