BGA Reballing Practice, Stencil Choice and Inspection Reballing a ball grid array package is one of the more demanding rework tasks in electronics assembly, because every ball is a joint and there may be several hundred of them on a package only a few millimetres square. It is done to…

Threaded Fasteners: Torque, Inserts and Clamp Load A threaded fastener looks like a trivial component and is one of the most common causes of a field failure. The joint either loosens, strips, or crushes what it is holding, and the cause is almost always that the torque was chosen by…

Reflow Self-Alignment and Placement Tolerance Limits Place a chip resistor half a pad width off centre and it often ends up perfectly centred after reflow. This is not luck; it is surface tension doing the work, and the industry has quietly relied on it for decades. Relying on it too…

Solder Mask Design Rules: Dams, Slivers and Openings Solder mask is not decoration. It keeps solder where it belongs, protects the copper from the environment, and defines the resolution of a fine pitch layout. The rules that govern it are geometric and they collide with each other. What the Mask…

Pad Cratering and Microcracks in Ball Grid Array Assemblies A solder joint can be perfectly formed and still fail, because the weakest link is often not the solder at all. When a ball grid array is loaded in bending, the copper pad and the resin beneath it can crack before…

High Speed PCB Design: Seven Rules That Pay Off High speed PCB design is less about a special technique than about a set of habits that reduce the number of times a board has to be redone. The seven rules below are the ones that experienced designers apply on every…

Seven Steps of PCB Design: From Library to Output A board that is designed twice costs twice as much, and most of the rework comes from skipping a step that takes an hour. The seven stages below are the ones that catch the mistakes while they are still cheap to…

PCB Drill Bit Wear and Its Effect on Plated Hole Quality A drill bit is a cutting tool that spends its life doing the hardest work in the fabrication shop. It wears progressively, and the wear shows up first in the quality of the hole wall rather than in the…

Thermal Profile: Reflow Thermal Profiling of Thick Copper PCB Assemblies A board with heavy copper planes does not heat like a thin signal board, and a profile that works on one will not transfer to the other. The copper conducts heat away from the joint faster than the laminate does,…

Fast Charging Circuit Design for Portable Products Fast charging is a system problem rather than a component choice. The power the charger can deliver is limited by the topology, the cable, the connector and the thermal design of the product being charged, and improving one of those alone changes very…