Component Cracking in Reflow: Thermal Shock and Moisture A cracked component is a failure that is often invisible at the end of the assembly line and certain to appear in the field. The crack may run through a ceramic body, through the encapsulation of a plastic package or through the…

Through Hole Fill: Vertical Fill and Solder Volume Control Through hole fill is the proportion of a plated barrel that is occupied by solder after the joint has formed. Barrel fill, more formally called vertical fill, is expressed as a percentage of the board thickness, and it is specified separately…

Presser Foot and Stack Clamping in PCB Drilling Every drilling machine presses the stack against the tool with a foot that surrounds the spindle. The presser foot flattens the entry material onto the panel, holds the layers in register and limits the vibration that the drill induces. Stack clamping is…

Conveyor Angle in Wave Soldering: The Exit Decides The conveyor of a wave soldering machine is inclined, and the angle is one of the few parameters that affects bridging, icicles, barrel fill and solder usage at the same time. The incline is set so that the board meets the wave…

Haloing Around a Hole: What the Laminate Is Telling You Haloing is the pale ring that appears in the laminate around a drilled hole, visible on a finished board as a lighter area and in a microsection as a separation between the resin and the glass fabric. The laminate has…

Scratches and Dents: Handling Damage in PCB Fabrication Scratches, dents and edge chips are the most common cosmetic defects on a finished board, and they are almost never produced by the process that is supposed to make the feature. They are produced by moving the panel: through a conveyor, into…

Copper Wicking: Where the Plating Travels and Why Copper wicking is the extension of plated copper along the laminate surface or into the bundle of glass fibres beside a drilled hole, beyond the boundary that the artwork defines. The copper is thin, it follows the fibres or the interface between…

Hole Wall Copper Thickness: Measuring the Minimum That Matters Hole wall copper carries the current between the layers of a board and provides the mechanical support that keeps a plated barrel intact through thermal cycling. It is specified as a minimum rather than an average, because a barrel fails where…

Vapour Degreasing for PCB Assembly: Solvent and Residue Control Vapour degreasing cleans a board by condensing solvent onto it. The solvent is boiled in a sump, its vapour rises and fills the tank above a defined vapour line, and a cold board introduced into that vapour causes the solvent to…

Conformal Coating Cure Profile: Solvent Release and Verification A conformal coating cures by losing solvent and then by a chemical or physical change in the resin. The cure profile is the combination of time, temperature and, for some chemistries, humidity or ultraviolet exposure that the coating sees after application. Getting…