April 18, 2018 - 4:00 pm - 4:40 pm
Dr. Jan Strueben, Team Lead Organic Materials Development at Heraeus Electronics
The trend for smaller devices in the electronics industry requires miniaturization on all levels. Especially the increased demand for sensors, 5G high frequency communication circuits, touch panel displays, smaller passive electronic components and medical devices. The degree of miniaturization has become a huge challenge for current thick film technology.
The demand for finer structures has reached the limitations of screen printing which is typically used to apply thick film pastes. As a leading global supplier of materials solutions for the semiconductor and electronic packaging industries, Heraeus Electronics is well aware of the demand for component miniaturization and higher density microelectronic circuits. In this work, results from process development work done at industrial partner Neways Micro Electronics using Heraeus photoimageable pastes are presented. We show that photoimageable thick film technology can be used as robust and repeatable process in production environments. Through addition of photoactive and polymerizable components, thick film pastes are obtained that are patterned using lithographic techniques. The production of ultra fine line structures down to 25 Âµm are demonstrated. The factors that govern the minimum achievable linewidths are discussed. With the availability of ultra fine line thick film pastes such as conductor pastes with Ag, Au, AgPd but also dielectric pastes, the full range of materials is available to be used for hybrid manufacturing. Next to the standard requirements for thick film pastes such as printability, shelf life, firing behavior, photoimageable pastes must fulfill additional criteria. The paste must show sufficient optical properties to achieve fine line resolutions and their reliable use in a production environment. As a key property, the influence of the light penetration depth of the paste on the line resolution and the processability of the paste is being discussed. A reproducible and tolerant process is the result of proper optimization of paste composition.
Paste performance and corresponding process capability is evaluated in terms of tolerance to variations in exposure and development processes. Moreover paste sintering during firing must result in predictable and reproducible behavior with respect to pattern shrinkage, line integrity as well as electrical conductivity and adhesion of the material. This is a prerequisite to set up proper design rules. Industrialization aspects are discussed, specific strengths and weaknesses compared to the standard screen printing process will be indicated. A higher level of cleanliness of working environment, tools and materials gets more important when dimensions get smaller. Under these optimal industrial conditions, capability for volume manufacturing production was demonstrated at Neways.