Diffusion bonding is a solid state joining technology for bonding similar and dissimilar materials together. The interfaces that are to be joined only undergo microscopic deformation and the joint area is homogeneous and bonding materialises at the atomic level. Diffusion bonding is carried out in a vacuum furnace under pressure with specially designed tooling. Due to the possibilities which diffusion bonding can offer, developing highly intricate and complex components such as those seen in heat exchangers have become possible. Diffusion bonding can also be used for dissimilar materials such as stainless steel to copper or ceramics. Here at Mat-Tech we have been actively developing diffusion bonding solutions for Big Science projects.