Underfill Dispense Software
A successful dispense process requires that the correct volume of fluid is dispensed. For larger devices the amount of fluid may be ample and if all of the fluid were to be dispensed at one time, the fluid would cover the substrate, not flow under the device – envision a flash flood. Larger components also require the fluid to be metered to the device in a controlled manner during multiple filling passes. This process allows a controlled amount of fluid to flow under the component before the next wave of fluid arrives. When substrates have many sizes of components, the number of passes and flow rates of individual components can vary dramatically. Some devices may require upwards of 10 to 15 passes. When components like these are mixed with components that require only two or three passes, programming an optimized process can be difficult and time consuming.
GPD Global has developed UltiPath™ software – it determines the best path for the gantry to take during a complex underfill process. An operator programs a device for underfill with an appropriate number of passes, dispense rate, dispense height, etc. and defines the minimum amount of delay between each of the passes for the fluid to flow (avoiding the flash flood of underfill). Each device is programmed and stored in a component library. When it is time to create the program, the operator inserts the components without worrying about which component is dispensed first or which one has the most or least number of passes. When the program is executed, the system dispenses the first pass on all units and then makes a decision as to which unit to include in the next pass. If, after trials, it is determined that one of the units requires more time to flow, no problem! Adjust the flow time for the device in question and rerun the program. There is no need to reposition lines in the program or reorder other devices. Additionally, if it appears more passes may minimize the wet-out area, no problem! Adjust the number of passes and rerun the program. Again, there is no need to reposition lines or order, the system takes care of it.
A desirable end result of an underfill process has a uniform fillet around the component that doesn’t wet to other devices or cover large areas around the component. With larger components, obtaining a desirable cosmetic look is not possible by dispensing all the fluid in a single pass. If it were, the dispensed fluid would be all over the substrate. In this case, the multiple “fill” passes must be programmed with a suitable delay between them to all fluid to flow under the device. Subsequent fill passes stay within the desired wet-out area and flow under the component. In some cases, 10 or more passes may be required.