Functional fluid jetting performance optimization

Abstract

Abstract The manufacturing method utilizing digital printing technology offers alternatives to create electronic structures to be used even in microelectronic applications. Material deposition based on digital inkjet technology offers advantages over both traditional mask-etch technologies and other printing methods. Inkjet technology works in an additive manner, reducing material consumption and the amount of created waste. Additionally, the digital nature of the process allows flexible production, e.g., rapid design changes, quick prototyping, and small, customized series. This research paper introduces ink jetting performance optimization utilized in a concept where discrete components and bare silicon chips were integrated in a single module with ink jetted interconnections. Jetting optimization of fluids enhances the droplet placement and volume accuracy that is a critical issue when forming interconnections for dense IC circuits. The overall drop placement error in jet printing is a combination of several error sources such as mechanical, dynamical and material related issues. However, the largest error portion is induced by a single printhead. The printhead related errors can be detected by observing the flight behavior after firing from the printhead nozzle. This paper focuses on optimizing the performance of ejected droplets during flight, i.e., drop formation sequence and minimum flight time variance. The average drop velocities of drops fired from separate printhead nozzles can be used to evaluate the difference in placement on substrate, which in worse case may lead to electrical wiring failures. The performance optimization was done by analyzing the initial state, modeling the drop velocity during flight, optimizing the process parameters to satisfy the model, and accepting the model after verification. Two inks, conductive and dielectric, were evaluated and improvement in placement accuracy was achieved through enhanced uniformity in drop average velocities, a dimensionless number, coefficient of variation was enhanced from 0.051 to 0.040,with conductive ink and from 0.111 to 0.049 with dielectric ink, thus decreasing the velocity related drop placement error.