Conformal Coating Adhesion: Making the Film Stay Put A conformal coating is only as good as the bond it makes with the surface underneath, and most coating failures reported in the field are adhesion failures rather than material failures. The film lifts at a pad edge, moisture creeps along the…

Component Staking and Adhesives: Fixing Parts for Vibration An adhesive applied between a component and the board is a small addition that solves several problems at once: it holds a part that is too heavy for its joints, it damps a resonance that would otherwise fatigue a lead, and it…

Hand Soldering and Rework Practice for Quartz Crystals A quartz crystal is a mechanical device in a ceramic or metal package, and it is more sensitive to soldering than almost any other passive component. The resonant frequency depends on the geometry of the quartz blank, and heating the package above…

Board Level Vibration Testing: Setup, Resonance and Failure A board that survives a drop in the laboratory sometimes fails in the field, and one that fails on a shaker sometimes survives a lifetime of service. The reason is that vibration testing measures the response of a system, and the system…

Encoder Interface Signal Integrity Design An encoder reports position by counting pulses, so a single corrupted edge becomes a permanent position error in a motion system. The signals travel down a cable that runs beside motor phases and switching supplies, and they arrive at a receiver that has to distinguish…

PCB Shipping Box Design: Getting There in One Piece Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This article…

ESD Control in Electronics Assembly: Grounding and Audits Static discharge damages electronic assemblies in ways that are often invisible, and it does so at voltages far below the level a person can feel. An ESD control program exists to keep those voltages from reaching the parts. What Damage Looks Like…

Screen Printing and Stencil Making for PCB Production Printing is used on a circuit board for two different purposes: the legend and solder mask applied by the fabricator, and the solder paste applied by the assembly house. Both rely on a patterned tool, and in both cases the quality of…

Tombstoning and Mid-Chip Solder Balls: SMT Defect Diagnosis Two surface mount defects account for a large share of reflow problems: a chip component that stands on one end, and a small solder ball stuck to the side of a chip. Both are mechanical events driven by the forces acting on…

PCB Reel Tracking: Knowing Which Reel Was Used Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This article explains…