Simulation and experimental study on temperature field of fluid jet-dispenser
Fluid jet-dispensing technology has been widely used in micro-electronic encapsulation industry. The fluid viscosity varies as temperature changes, while it affects the process remarkably. Besides basic method on temperature field solution, some thermal behaviors, including heat conduction and heat exchange, boundary conditions and some physical parameters are overall analyzed in this paper. Based on the simulation software platform ANSYS, a two-dimensional transient temperature field model of jet-dispenser was built, and simulation programs on temperature field for two sorts of fluid with obviously different thermal conductivity were performed. Then heating experiments were finished to validate the feasibility of FEA, and results show that temperature distribution is homogeneous along fluid area and it meets the conditions of jetting.
Fluid Jetting for Next Generation Packages
With the advances and improvements in technology of the electronics industry, the scale of components used has consistently grown smaller. This has allowed for more efficient use of resources (a silicon chip that once held hundreds of transistors now holds millions) and more convenient and consumer friendly products (palm sized computers compared to warehouse sized computers forty years ago). However, as advances lead to decreases in the scale of components, similar advances must be made in the production process in order to assemble these components. One method used in current printed circuit board assembly is attaching components to the board with a surface mount adhesive (SMA). A small dot of adhesive is placed between two leads. The component is then placed on top of the SMA, in contact with the leads. The SMA is then cured, fixing the component in place. When applying the SMA, it is vital that the adhesives not cover any part of the leads, as this may decrease the quality of the electrical contact. As components decrease in size, so does the gap between the leads. It is therefore necessary for the size of the adhesive dot to decrease to the same degree as the components decrease. Current technology can produce dots of surface mount adhesive of approximately 20 mil diameter and roughly 0.03-0.04 ml volume. Anticipating the continuing trend in component scale reduction, however, predicts that dots in the 8-10 mil diameter range will be required. The experiment described in this paper attempted to reach this measure of dot size using SMA and silver epoxy materials. The underfilling 3D-packages with small gaps that are required to accomplish thin packages, as well as the underfilling of small die present yet another challenge to the consistency and accuracy of dispensing processes. This paper proposes a solution to this dispense challenge by way of the non-contact Jetting Underfill for both, traditional capillary flow and Forced flow Underfilling, commonly known as No-flow Underfilling. Introduction The jet used in this research was the Asymtek DJ-2111 non-contact dispense-jet (figure 1). This jet works according to the following mechanism. Beginning with an electrical signal, a solenoid is triggered, allowing air pressure into a chamber. This air pressure applies force to a seal, which is attached to a needle, not only lifting the needle, but also compressing a spring on the other side of the seal. As the needle is lifted from its seat, fluid is allowed to flow down and around the needle tip. At the end of the electrical impulse, the solenoid discharges, releasing the air pressure allowing the force form the compressed spring to slam the needle tip back down into its seat, separating and ejecting a dot from the fluid. There are several parameters that can be adjusted in order to alter the size of the dots produced. The parameter adjustments affect the dots in two different ways, either by changing properties of the fluid, or by changing mechanical properties of the jet. The pressure on the fluid in the syringe was adjusted from 10 to 30 psi. This variation affected how much force pushed the fluid down and around the needle tip when it was raised. The other parameter that affected fluid properties was the temperature to which the heater at the nozzle was set. This was varied between 30 and 60 degrees C. At higher temperature viscosity is increased, reducing surface tension and
Evaluation and Control of Collapsible Soils
Some compacted soils wetted under certain conditions of compaction and loading may exhibit additional settlement (collapse). To investigate the effect of the soil type, compaction water content, initial dry unit weight and applied pressure at wetting on collapse potential, 138 single‐oedometer tests were conducted on eight different soils. The results indicate that well‐graded soils tend to collapse more than poorly graded ones under similar conditions. Furthermore, collapse potential decreases with an increase in (1) The difference between the sand and clay percentages; (2) compaction water content; and (3) initial dry unit weight, while it increases with pressure at wetting. A multiple regression analysis was performed on the laboratory results to provide a collapse‐predictive model that was substantiated by data reported by several researchers. A chart is presented to estimate (1) The collapse potential of soils under various conditions; and (2) the critical water content beyond which no collapse is ex...