Dispensing is a direct-write process for additively depositing a material on a substrate. It can deposit controlled quantities of materials in precise locations on a substrate. It offers a complete freedom of design where a material can be deposited in any pattern. It is a drop on demand repeatable process which can achieve consistent results with minimum material wastage. It can be used for depositing a wide array of materials such as polymers, epoxies and metallic inks in a viscosity range of 1 mPa.s to 100 Pa.s. It is compatible with a wide range of substrates such as PCBs, glass and silicon wafers.
Dispensing can be used for creating stacked structures which can consist of multiple materials. For packaging, dispensing is used for depositing encapsulants on the die, interconnect and package/PCB. It is also used for underfilling a flip chip arrangement. It offers a precise, accurate and repeatable method of depositing an encapsulant in digitally defined areas of a substrate. As a dispenser can deposit the material in any pattern, it is ideally suited to glob-top encapsulations and conformal coatings.
A robotic dispenser system consists of a pneumatic dispenser unit, XYZ movement stage, a syringe and a computer. A material to be dispensed is placed in the syringe, one end of the syringe is connected to an air hose which directs compressed air to the syringe and the other end has nozzle which directs the flow of ink on to the substrate. The dispenser unit controls and coordinates the air pressure applied to the contents of the syringe including the length of time the pressure is applied to the syringe. XYZ stages control the movement of the substrate and define area of substrate for material deposition. A computer coordinates the function of the dispenser unit and the movement stages. They are often determined by the application requirements of the electronics to be encapsulated.
The volume of a deposition is controlled by the following parameters.
The Advanced Packaging Facility has two table top industrial dispensing systems. The dispensers consist of 3-axis movement robots, integrated vision systems and pneumatic pressure controllers.
The following presents the specifications of the two dispenser systems: