Reflow Conveyor and Support Tooling The conveyor carries the board through the oven and holds it while it is hot, and its behaviour decides whether the profile at the board matches the profile at the thermocouple. Support tooling then keeps the assembly flat while the alloy is liquid. Both are…

Solder Paste Printing Defect Causes Most solder defects are created at the printer, and most of them are visible in the paste deposit before the board ever reaches the oven. Learning to read the deposit is therefore the fastest route to a stable process. The defects fall into a small…

Tin Plating as an Etch Resist: Process Control Guide Tin plating as an etch resist is one of the older techniques in printed circuit fabrication and it remains the workhorse for fine line inner layers and for outer layers with heavy copper. A thin metallic layer is deposited over the…

Copper Foil Roughness: Preparation, Placement and Process Control Copper foil is not smooth. The side that bonds to the laminate is treated to give it a rough, dendritic surface that grips the resin, and the scale of that roughness is measured in microns. At low frequencies the roughness is irrelevant,…

Solder Alloy Selection for High Temperature Service An assembly that operates hot needs a solder whose melting range leaves a margin above the service temperature. The margin is what keeps the joint from creeping and from coarsening while it is in service. Why the Melting Range Matters A solder with…

Depaneling Dust and Contamination Control Depaneling produces debris, and on a populated board the debris lands on surfaces that are already finished. The particles are conductive or hygroscopic depending on their origin, and both kinds cause trouble later. Where the Debris Comes From Routing the tabs produces laminate and copper…

Automated Conformal Coating Program Setup An automated coating machine applies a film along a programmed path, and the quality of the result depends on the pattern, the material condition and the path as much as on the material itself. The program is what holds all three together. Pattern and Overlap…

Stencil Frame Tension And Its Effect On Printing A stencil is a sheet of metal tensioned in a frame, and the tension is what keeps the foil flat against the board during printing. If the tension falls, the foil sags between the squeegee strokes, the board is not in full…

Low Loss Laminate Selection For High Speed Boards The laminate in a high speed design is no longer just a mechanical carrier with a dielectric constant. Its loss characteristics set how far a signal can travel before it needs to be retimed, and the choice between a standard FR-4 and…

Conformal Coating Application Methods For PCB A conformal coating is a thin polymer film applied over an assembled board to protect it from moisture, dust, salt and chemical attack. It does not make a board waterproof in the way a sealed enclosure does, but it raises the surface insulation resistance…