Micro-joining and hermetic sealing of dissimilar and biocompatible materials is a critical issue for a broad spectrum of products such as micro-electronics, micro-optical and biomedical products and devices. Today, biocompatible titanium is widely applied as a material for orthopedic implants as well as for the encapsulation of implantable devices such as pacemakers, defibrillators, and neural stimulator devices. Laser joining is the process of choice to hermetically seal such devices.
Laser joining is a contact-free process, therefore minimizing mechanical load on the parts to be joined and the controlled heat input decreases the potential for thermal damage to the highly sensitive components. Laser joining also offers flexibility, shorter processing time and higher quality. However, novel biomedical products, in particular implantable microsystems currently under development, pose new challenges to the assembly and packaging process based on the higher level of integration, the small size of the device's features, and the type of materials and material combinations. In addition to metals, devices will also include glass, ceramic and polymers as biocompatible building materials that must be reliably joined in similar and dissimilar combinations. Since adhesives often lack long-term stability or do not meet biocompatibility requirements, new joining techniques are needed to address these joining challenges. Localized laser joining provides promising developments in this area. This paper describes the latest achievements in micro-joining of metallic and non-metallic materials with laser radiation. The focus is on material combinations of metal-polymer, polymer-glass, metal-glass and metal-ceramic using CO<sub>2</sub>, Nd:YAG and diode laser radiation. The potential for applications in the biomedical sector will be demonstrated.
Advanced microsystems for optoelectronic and biomedical applications incorporate a variety of non-metallic materials such as glass, silicon, sapphire and polymers. Examples include switches and multiplexers for fiber-optical data transmission in telecommunications, and innovative implantable microsystems currently being developed to monitor, stimulate and deliver drugs. Laser micromachining has proven to be an effective tool to address specific manufacturing challenges for these devices. Investigations have been conducted on laser ablation for precise localized material removal, laser cutting, and drilling; and application data for a range of relevant materials already exists. In contrast, applications of laser joining are currently limited to microwelding and soldering of metals. The assembly of SMD’s and the sealing of pacemakers are typical examples.
This paper will describe the latest achievements in laser microjoining of dissimilar materials. The focus will be on glass, metal and polymer that have been joined using CO<sub>2</sub>, Nd:YAG and diode lasers. Results in joining similar and dissimilar materials in different joint configurations will be presented, as well as requirements for sample preparation and fixturing. The potential for applications in the optoelectronic and biomedical sector will be demonstrated.