Pin in Paste Reflow for Through-Hole Parts A through-hole connector can be soldered in the same reflow pass as the surface mount parts if the paste is printed into the hole as well as onto the pad. The technique removes a process step and it depends entirely on getting enough…

Edge Plating and Castellated Holes for Module Edges A small module that must be soldered to a mother board along its edge uses half holes rather than pins. The castellations are drilled and plated as part of the board, then cut in half when the module is separated from its…

Thermal Shock and Thermal Cycling: Choosing the Right Test Two tests appear in almost every reliability plan, and they are frequently confused with each other. Thermal cycling and thermal shock both vary the temperature of an assembly, and they fail it by completely different mechanisms. The Physical Difference Thermal cycling…

BGA Warpage and Coplanarity in Reflow A ball grid array is soldered by joints the inspector cannot see, and the failure that matters most is a joint that never formed because the package and the board were not parallel when the solder was molten. Warpage in a Package A package…

Wire-to-Board Connector Assembly and Strain Relief Wire-to-board connections carry power and signals off the board, and they take abuse that no surface mount joint ever sees. Cables are pulled, bent and routed by installers, and every one of those actions loads the termination. A connection that passes electrical test on…

Double-Sided Assembly: Second Side Reflow, Support and Weight A board with parts on both sides passes through the reflow oven twice. The second pass heats an assembly that already contains molten joints on the other side, and that changes almost every process decision. What the Second Pass Does to the…

Humidity and Condensation Testing of Assemblies An assembly that passes every electrical test in a dry laboratory can fail in a humid climate, and the failure will be attributed to the environment rather than to the design. Humidity testing exists to make that failure appear in the laboratory, where it…

No-Clean Flux Residue: Deciding When to Wash a Board No-clean flux is named for what it allows you to skip, not for what it leaves behind. The residue stays on the board, and in most applications that is entirely acceptable. In others it is the beginning of a reliability problem…

Metal Core Board For A High Voltage Linear Amplifier A linear power amplifier that has to deliver ten amps at two hundred volts is a thermal design problem before it is anything else. Unlike a switching amplifier, it does not convert the surplus energy into a waveform with high efficiency;…

Compliant Pin Joints: Hole Size, Insertion Force and Reliability A compliant pin joint is made by pushing a shaped pin into a plated hole, where the pin deforms elastically and the resulting spring force holds it against the barrel wall. Nothing is soldered, nothing is heated, and the connection depends…