PCB Laminate Storage, Shelf Life and Moisture Control Laminate is a chemically active material that keeps changing after it leaves the supplier. Prepreg continues to advance its cure, cores absorb moisture from the air, and a roll left in the wrong corner of the store can turn a proven lamination…

Preventing Solder Mask Skips and Voids Solder mask skips are the defects that look trivial and are not. A small area where the ink did not transfer leaves copper exposed, changes the surface the solder sees, and creates a point where contamination can reach the laminate. Because they are small,…

Planning an HDI Microvia Stackup Before Layout High density interconnect is often described as making the holes smaller, but that description misses the point. The real change is that the layer structure becomes a design variable rather than a fixed frame: the number of build-up layers, the thickness of each…

Aluminium Nitride: Preparation, Placement and Process Control Aluminium nitride occupies a specific niche among substrate materials. It is a ceramic that is electrically insulating and thermally conductive, and it is chosen when a circuit has to move a large amount of heat through an insulating layer rather than around it.…

SMT Feeder Setup and Changeover in Production Lines Placement machines get the attention, but the feeders feeding them decide how the line actually performs. A misindexed feeder throws off every placement it serves, a worn tape guide causes pick errors that look like nozzle faults, and a slow changeover eats…

Mounting Hole: Mechanical Constraints That Shape the PCB Layout A printed circuit board is a mechanical component as much as an electrical one, and the mechanical requirements are usually stated late, after the layout is under way. Bringing them forward removes most of the late redesign that mechanical constraints otherwise…

Surge Protection Design for a Low Voltage AC Supply Port A 36 volt AC supply rail does not look like a high risk interface. The voltage is low, the current is modest, and the connected equipment is often a controller, a sensor or a relay board. The mistake is to…

UPS Circuit Board Design: Inverter, Charger and Layout A UPS circuit board sits between the mains supply and equipment that is not allowed to stop, so it has to handle high voltage, high current, thermal cycling and continuous operation at the same time. The topology chosen at the start decides…

Flexure Life and Bend Fatigue in Flex Circuits A flexible circuit that is bent once during assembly and a flexible circuit that bends twice a day for ten years are entirely different design problems. The first can be treated almost like a rigid board; the second is a fatigue structure,…

Board Strain Measurement During Assembly A board that flexes by a fraction of a millimetre during assembly can crack a multilayer ceramic capacitor or lift a solder joint, and the damage may not appear until months later in the field. Because the cause is mechanical and the effect is electrical,…