The paper reports an effective method to fabricate micro-lens arrays with the ultraviolet-curable polymer, using an original pneumatically diaphragm-driven drop-on-demand inkjet system. An array of plano convex micro-lenses can be formed on the glass substrate due to surface tension and hydrophobic effect. The micro-lens arrays have uniform focusing function, smooth and real planar surface. The fabrication process showed good repeatability as well, fifty micro-lenses randomly selected form 9 × 9 miro-lens array with an average diameter of 333.28μm showed 1.1% variations. Also, the focal length, the surface roughness and optical property of the fabricated micro-lenses are measured, analyzed and proved satisfactory. The technique shows great potential for fabricating polymer micro-lens arrays with high flexibility, simple technological process and low production cost.

Fluid dispensing is a method by which fluid materials (such as epoxy, adhesive, and encapsulant) are delivered in a controlled manner in electronics packaging. Fluid jetting, derived from inkjet technology, is a noncontact, data-driven fluid dispensing technology. But ideal fluid materials for packaging are usually high viscous, which is difficult to realize by traditional inkjet technology. In this paper, a mechanical micro-droplet jetting system for high viscosity fluid was proposed. It consists of dispensing valve, motion stage, temperature control subsystem, pneumatic subsystem, driving circuit for solenoid valve, and system control software. Performance of this system under various circumstances was studied by changing several parameters, including working temperature, stroke length, back pressure and drive pulse width. Tiny droplets of 0.35 mm in diameter were produced by stainless steel nozzle of 0.2 mm in diameter in the experimental study. high viscosity fluid, micro-jetting, microelectronics packaging Citation: Shu X Y, Zhang H H, Liu H Y, et al. Experimental study on high viscosity fluid micro-droplet jetting system.

A thermoplastic polymer refractive microlens array has been rapidly fabricated by contactless hot embossing technology through the stainless steel template with micro through-holes array, which has a diameter of 150 µm and a pitch of 185 µm. By optimizing the technical parameters including heating and demoulding temperature, loading pressure, loading and pressure holding time, a series of high quality microlenses arrays of different sags could be obtained. In addition, the sag and the radius of curvature of the microlens are controllable. The geometrical and optical properties of the microlenses are measured and the influence of temperature and pressure duration on the optical properties of the microlenses are analysed. The results show good surface features and optical performances. Unlike previous contactless hot embossing, a low cost and durable stainless steel template was utilized instead of silicon or nickel mold to avoid valuable equipments and complicated fabrication procedure. Besides, the whole contactless hot embossing process was absence of vacuum equipment. We think that the technology could be an attractive high flexibility method for enhancing efficiency and reducing cost.

Micro-droplet jetting belongs to the field of precision fluid dispensing techniques. Unlike traditional subtraction manufacture process, micro-droplet jetting as an additive fabrication technique with features of non-contact and data-driven represents a new development trend of modern manufacturing process. In this paper, the design, fabrication and performance of a multimaterials drop-on-demand (DOD) inkjet system based on pneumatic diaphragm actuator were described. For capturing the droplet ejection process and measuring the droplet dimension, a self-made in situ imaging system based on time delayed external trigger was set up. The performance of the generator was studied by adjusting the structure and control parameters. Furthermore, the influence of fluid properties on the droplet ejection process was experimentally investigated. Micro-solderballs of 160.5 µm in diameter and UV curing adhesive micro-bumps of 346.94 µm in contact diameter with the substrate were produced. The results demonstrated that the DOD inkjet generator possesses characteristics of robust, easy to operate and maintain, and able to withstand high temperature as well as applicability to a wide variety of materials including polymers, low melting point resin and high melting point metal. The system has a great potential of being used in the fields of IC and MEMS packaging, 3D printing, organic semiconductor fabrication, and biological and chemical analysis.