A Practical AOI Programming Strategy for SMT Inspection An AOI machine does not find defects by itself; it finds what its program tells it to look for. That makes programming the single most important engineering task on an automated inspection line. A well built program catches real defects at a…

Class D Amplifier PCB Layout A class D amplifier is efficient because its output devices spend almost all their time either fully on or fully off, and that is exactly what makes the layout difficult. Every switching transition is a fast edge carrying a large current, and the board is…

Solder Void Prevention in PCBA Assembly A solder void is a pocket of gas trapped inside a joint, and it is the defect most likely to be accepted at inspection and questioned in the field. Voids reduce the cross section that carries current and heat, and under thermal cycling they…

Water Ingress Along A Coaxial Cable: One Wet Connector Ruins It A connector that lets water in does not fail at the connector. The water wicks along the inside of the cable, and by the time anyone notices the signal has been degrading for months, the damage extends metres beyond…

Copper Foil Roughness and High-Frequency Insertion Loss Loss in a high-speed channel is usually blamed on the laminate, and a change of dielectric is ordered, while the copper surface the signal actually travels on goes unexamined. Above a few gigahertz the two contributions are comparable, and the one that is…

Jet Printing Versus Stencil Printing for Solder Paste Deposition For thirty years stencil printing has been the default way to put solder paste on a board, and it still is for most volume production. Jet printing arrived later and changed the economics for high mix work, because it can place…

Copper Foil Surface Profile and Adhesion in PCB Lamination Copper foil is the conductor that carries every signal and every ampere on a printed circuit board, and the two industrial routes that make it produce materials with very different grain structures. The surface profile of that foil decides how firmly…

Polarised Component: Placing Polarised SMT Components in the Right Orientation Most surface mount components can be placed either way round without consequence, but a significant minority cannot. Diodes, tantalum and aluminium electrolytic capacitors, light emitting diodes, some inductors and most integrated circuits have a defined orientation, and placing one backwards…

High Precision PCBA Cost: What Actually Drives the Price A high precision pcba costs more than an ordinary assembly, and the reasons are traceable rather than mysterious. Micro-scale components, area array packages, HDI structures and strict reliability requirements each add process steps, equipment time and inspection. Understanding which of them…

PWM to Analog Conversion Filter Design Many microcontrollers have no digital to analog converter, but almost all of them have a timer output. PWM to analog conversion uses that timer and a low pass filter to produce a usable voltage, and while the principle is simple, the filter design decides…