Precision Dispensing on PCBs: Underfill, Dam-and-Fill and Conformal Coating Compared-Shenzhen Second Intelligent Equipment

Every dispensing operation on a PCB looks like putting adhesive on a board, yet underfill, dam-and-fill and conformal coating machine demand almost opposite things from the machine: one must wick underneath, one must hold a wall, one must spread thin and even. Understanding those differences is how you judge whether a single platform can cover several lines.

 Shenzhen Second Intelligent Equipment Underfill relies on capillary action to fill the gap between die and board. Volume must be exact: too much wicks onto neighbouring components, too little leaves voids. The critical controls are preheat temperature, dispensing position close to the die edge, and a single-side or L-shaped pass. Warmer material lowers viscosity and fills faster but shortens working time, so the line has to balance the two.

Dam-and-fill lays a wall of high-viscosity, high-thixotropy material, cures it, then fills the cavity with a low-viscosity resin. Dam width and height set the depth that can be filled in one pass, and the wall is usually as tall as or slightly taller than the components. The most common error is running both materials through the same valve: either the dam sags or the fill never reaches the corners.

 3.Conformal coating: thin, even, selectively masked

Conformal coating targets a uniform film tens of microns thick rather than a dot or bead. The requirement shifts to path continuity and film control: valve opening, travel speed and overlap ratio together set thickness. Masking is the other difficulty — connectors, gold fingers, test points and thermal areas must all be avoided precisely, and applying and peeling maskant is a process in itself.

4.What it takes to cover several operations on one machineFor low volume and high mix, one precision dispensing platform with quick-change valves and multiple supply modules is workable — provided the machine supports recipe switching, the valve interfaces are common, and fixtures accommodate different board formats. If shift output is high and coating and dispensing cycle times differ widely, separate machines make more sense, because waiting losses from mismatched cycle times outweigh the price difference.

https://secondintelligent.com/industry-news/application-of-precision-dispensing-in-pcba-conformal-coating-process/